APPENDIX A – TERMS OF REFERENCE

APPENDIX B

SUMMARY OF SUBMISSIONS RECEIVED BY THE DEPARTMENT OF PLANNING

The following is a brief summary of submissions received by the Department of Planning. The key issues are discussed in various sections of the Commission’s report. PUBLIC AUTHORITIES Department of Environment, Climate Change & Water identified a number of issues raised in the Environmental Assessment that require more detail or clarity before DECCW is prepared to support the project and provide recommended conditions. These issues include: Water The risk of subsidence impacting on surface watercourses, groundwater, surface water flows and aquatic ecology has not been adequately addressed. More detail is required on the impact of subsidence on aquifers and the potential for a fault zone under the alluvium. More detail is also required on the impact of treated mine water and brine disposal on the environment. Floodplain Management The hydrologic and hydraulic models for the Dooralong/Yarramalong catchments and the Hue Hue catchment have been shown to be properly calibrated. The models do not provide an adequate level of confidence in predicting the impact of subsidence on flooding. More rigorous sensitivity testing of the catchment models should be considered to assess the impact of higher flow rates and subsidence than is currently assumed. Threatened Species and Biodiversity More detail is required on the survey effort conducted for the project, specific targeted surveys, the area that will be impacted by the project and the offset requirements due to clearing or subsidence. At this stage, DECCW cannot form a considered opinion on the effects of the proposal on threatened species and ecosystems. Noise Conditions can be provided to address noise impacts. DECCW recommends that a construction noise management plan be prepared, that noise and blast limits be imposed, that the proponent prepare an annual noise compliance survey and that only specified locomotives be permitted to operate on the rail loop. Air and Climate Change The air quality assessment appears to have been prepared in accordance with relevant standards. DECCW recommends that a reactive dust management plan be prepared for the project, and that conditions requiring world’s best practice in relation to coal stockpiling, storage and dust emissions be imposed. The assessment of greenhouse gas emissions is generally satisfactory however further information is required to support various use factors and the analysis of the product coal. An options study for coal mine methane capture and utilisation should be required within 3 years of commencement of production.

Aboriginal Cultural Heritage The proponent should conduct further excavation investigations at several sites and provide further site specific management strategies at the Spring Creek Potential Archaeological Deposit. NSW Office of Water stated that the Environmental Assessment failed to assess the potential impacts of the project on groundwater within the alluvial blanket associated with Jilliby Jilliby Creek and the Wyong River in a robust and verifiable manner. Surface flows in both these watercourses are highly reliant on shallow alluvial groundwater and the project must demonstrate that subsidence will not interrupt these flows or affect available water determinations. The groundwater impact model is deficient for robust predictions of groundwater interactions in post-subsidence conditions. The subject environment is sensitive but there is no sensitivity assessment of model outputs. The potential for redirection of alluvial groundwater into basal tensile fracture networks and/or re-activation of regional geological structures has not been adequately addressed. A precautionary exclusion zone is recommended around the alluvium of the Wyong River, Jilliby Jilliby and Little Jilliby Creeks and tributaries until greater certainty surrounding these impacts is provided. An adaptive management approach should be required so that coal extraction responds to any impacts on alluvial and surface water sources. Hunter Central Rivers Catchment Management Authority objected to the proposal. Its comments focused on the project’s impacts on the Hunter-Central Rivers Catchment Action Plan (CAP). Several CAP guiding principles have not been addressed by the proposal, including: Native Vegetation The proposed offset is not adequately described or sized and does not improve or maintain the existing ecological value. Surface Water The subsidence associated with the project will lower beds, which has a high risk of causing head cuts and ongoing bed erosion. This issue has not been adequately addressed. Groundwater The HCRCMA does not support a reduction of the shallow groundwater aquifer by 25% which appears likely to occur as a result of the project. Risk Assessment The proposal will give rise to unacceptable long-term environmental consequences. Additional information should be produced by the proponent and stringent conditions and monitoring should be imposed by the approval authority. Transport NSW required further assessment of the impacts of the project on the Main North Rail Line. The Environmental Assessment assumes static service frequency along the line but both freight and passenger services are predicted to increase in the future. The Environmental Assessment should also consider how future employees can be encouraged to access the site by means other than private vehicles.

RailCorp asked that the proponent: meet the costs for the construction of the new crossover prepare an operations review of junction interaction, and contribute to a capacity review of the rail corridor and any RailCorp proposals for

infrastructure and system enhancements. Roads and Traffic Authority noted that the results of the RTA’s own intersection simulation analysis varied from those in the Environmental Assessment. The western intersection of the Sparks Road interchange currently operates at Level of Service (LoS) C, and will operate at LoS D in 2020 with the addition of the project traffic. Both of these levels of service are acceptable. The eastern intersection operates at LoS D and C (am and pm peaks respectively). With the addition of project traffic, the LoS for this intersection will drop to an unacceptable F. Traffic control signals will therefore be required by 2012 as a result of the project. The RTA estimates that the proponent should be required to contribute $143,000 towards the cost of this upgrade. Department of Industry and Investment provided comments on the following issues: Mining Titles The relationship between the Mining Lease Areas and the Project Area is not clear in the Environmental Assessment. Rehabilitation and Mine Closure The rehabilitation plans for the project are satisfactory and will produce a safe, stable and non-polluting final landform. Subsidence Although the subsidence modelling used by the proponent is acceptable, there is remaining uncertainty in these predictions and an adaptive management approach to the project is required. Attention will need to be paid to the fringes of the subsidence area to ensure that flooding impacts and impacts on transmission lines are adequately managed. Clay Resource The project is adjacent to a regionally significant clay resource. The proponent should continue to consult with the company extracting this resource to ensure that both resources can be utilised. Forests The proponent will need to consult with the Department regarding subsidence of Forests NSW roads, the program for revegetating Wyong State Forest and the use of State Forest land. Fisheries The project has the potential to affect key fish habitats due to the hydrological changes induced by subsidence and erosion. The proponent should implement a monitoring plan to ensure that creeks and rivers are protected. The proponent should also prepare a management plan to address creek and wetland rehabilitation in the event of subsidence, erosion and/or flooding.

NSW Health raised concerns regarding the following issues: Air Quality Further information is required regarding the busiest day scenario used in the air quality assessment. The increased levels of particulate matter beyond the site are a major concern. The predicted 10ug/cm increase in PM10 particulate matter will produce increased respiratory symptoms and morbidity among residents, and the likely increase in resident populations around the site has not been addressed. Noise There is insufficient detail on construction noise levels. Licensing conditions will need to include monitoring requirements to ensure ongoing compliance and residents must have recourse to make complaints and have those complaints responded to. On Site Water Management The proposed recycled water options at both sites must comply with national guidelines. Direct potable reuse schemes must comply with appropriate standard to avoid risk to health. Climate Change Mining, transport and power generation from the coal extracted by the project will generate an estimated 361 million tonnes of carbon dioxide emissions. The annual emissions from those processes represent 2.4% of Australia’s carbon emissions. The environmental sustainability of the project should be considered in a regional context. Lake Macquarie City Council did not object to the project, but requested that any recommended conditions of approval include measures to manage and maintain the acoustic and air quality amenity of residents of the City, from both the operation of the mine and the transport of coal, via the rail network, to the Port of Newcastle. Gosford City Council stated its full support for the submissions made by Wyong City Council and the Gosford Wyong Councils Joint Water Authority. Wyong Shire Council objected to the proposal and submitted an independent review of the Environmental assessment, copies of submissions received following Council’s public forum on the project, and a DVD of the proceedings of that forum to support its objection. The independent review by PSM of the Environmental Assessment found the following: Subsidence The subsidence predictions in the EA are conservative and consistent with Australian best practice. The predictions regarding the effect of this subsidence on natural features, local houses and rural buildings appears reasonable but management strategies should be developed to ensure this impact is appropriately managed. Regional structures are unlikely to be adversely affected, but F3 Freeway infrastructure and the Hue Hue Landslide should be monitored during the operation of the project. A Subsidence Management Plan must be developed for the project.

Groundwater The input parameters adopted for the proponent’s groundwater modelling are not consistent with available data. The findings from this modelling should therefore be rejected, and it is not known how the project will affect groundwater. Flooding The flooding assessment presented in the Environmental Assessment appears reasonable and consistent with Australian best practice. However, an ongoing review of subsidence and its impacts on flooding is essential. Stream Flows Concerns remain regarding the impact of the project on near surface groundwater and the resultant loss in stream flows. Erosion will need to be monitored and managed, and preventative measures should be preferred. In addition to the findings of the PSM review, the independent review by Earth Systems of the Environmental Assessment raised several more issues. An adequate baseline was not established for the ecological assessment and only limited field surveys were undertaken. No current field baseline data was provided for aquatic fauna. On-site water impacts such as construction erosion, fuel spills and operational discharges have not been adequately addressed. The acid and metalliferous drainage potential of the mined materials and wallrock has not been assessed. On-site waste management has not been adequately addressed. The impact of the project on the surrounding rail network has not been adequately considered. The cumulative impacts of the project, alternative designs and project justification are not addressed in detail. The risk assessment and benefit cost analysis do not account for the knowledge gaps and uncertainty that exits surrounding the project. There are only limited details on the proposed management and rehabilitation plans for the project. Concerns raised during the limited community consultation undertaken by the proponents have not been adequately detailed. Gosford Wyong Councils Joint Water Authority stated that the Central Coast water supply will continue to be heavily dependent on the Wyong River and its tributaries, including Jilliby Jilliby Creek into the future. As well as submitting the PSM report included with Wyong Council’s submission, the Authority made the following comments:

the project has the potential to impact on the Mardi to Mangrove pipeline; greater emphasis will be placed on extracting water from the Wyong River, Jilliby

Jilliby Creek and Ourimbah Creek in the future, and the project has the potential to adversely impact water quality and volumes in these rivers and creeks;

the project has the potential to impact 13% of the water supply catchment area (not 5% as stated in the Environmental Assessment;

given the uncertainty in the modelling in the Environmental Assessment, the Authority considers the project a threat to the regional water supply;

weed eradication, riparian planting and education programs are not considered an appropriate offset for the impacts on water quality and supply;

the proposal for treated water from the mine contributing to the regional water supply has not been addressed in enough detail to allow it to be considered as an offset;

the commitments regarding monitoring, management and rehabilitation of the water supply catchment area are not sufficiently detailed; and

the project presents an unacceptably high risk to the regional water supply and should be refused.

Residents, Community Groups and Businesses

Positives of the proposal

The proposal will bring economic benefits to the local area including 210 local jobs and $200 million per year in local outputs.

Mining has successfully occurred in Wyong and at much shallower depths than is proposed.

Issues of concern and objection

The baseline data and modelling parameters used in the Environmental Assessment are flawed.

Coal dust and other air pollutants from the operations will affect the respiratory health of nearby residents and schoolchildren, degrade water quality, reduce the efficiency of residential photovoltaic systems and affect the viability of local food operations.

The proposed water suppression sprays would not prevent all coal dust from leaving the site.

It is unclear how long gas flaring will occur on the site and what the impacts of this activity are on air quality.

The air quality assessment does not consider cumulative impacts.

The project will undermine the integrity of regional aquifers, rivers and water supplies. The water table will be lowered. The model used for subsidence and aquifer impacts is not appropriate.

Subsidence will adversely affect water supplies, water quality, flora and fauna and housing. The assessment does not include non-conventional subsidence impacts.

There should be a minimum 1 kilometre exclusion zone around all watercourses and waterbodies.

Subsidence will prevent future residential subdivisions which are proposed to occur over the mine site.

Subsidence could affect the operation of the high voltage powerlines in the area.

The proponent should be required to pay a bond to protect the site from subsidence and water supply/quality impacts.

Vulnerable, threatened and endangered ecological species will lose their habitats.

Rail traffic noise will adversely affect nearby residents.

Additional rail traffic will increase safety risks at level crossings and slow the high-speed passenger trains on the rail line.

There will be increased traffic congestion and damage to roads as a result of the project.

The project supports coal-fired electricity generation, which is a major contributor to global warming, and this impact has not been adequately assessed. The project does not consider the need for inter-generational equity.

The project will increase the risk, length and severity of flood events and the most recent data on sea level rise has not been considered.

More sustainable alternative sources of energy have not been properly considered.

The mine will have adverse visual impacts and will decrease property values.

The tourism industry will suffer from the presence of a mine in the region.

The ventilation fans associated with the shafts will create unacceptable noise levels.

The public has not been adequately consulted regarding the project.

Residents will be forced to move or repair their houses and this will have an adverse social impact.

There would only be limited local economic benefit from the mine and most of the profits from the project would go overseas.

The site is inappropriate because it is located next to existing and proposed residential areas.

Vibrations from the operation of the project have not been assessed.

There is no clear recourse for communities affected by greater than predicted levels of subsidence or loss of water supply/quality.

Run-off from the site will lead to downstream impacts on water quality in terms of salinity and heavy metals.

The project will alienate prime agricultural land.

Drought and increased residential development means that there is no spare water to allocate to the mine.

The project will result in more shipping traffic and the potential for pollution along the coastline.

The project justification is flawed because coal is a non-renewable, polluting resource that has unacceptable impacts on human settlements and the environment. It is not safe for humans to be extracting this mineral, it has unquantified externalities, and it will lead to economic problems when coal is priced out of the energy market.

The compensation or acquisition process for local residents has not been detailed.

Employment will not be given the locals but to experienced miners from elsewhere in the region, interstate and overseas.

There is no additional employment as a result of this project, the workers for this project will come from existing projects in the region.

The environmental and social risks associated with the project outweigh the potential economic benefits.

It is not possible to fully rehabilitate areas that have been affected by longwall mining.

Noise from operations at the Tooheys Road site will be above criteria and are totally unacceptable to surrounding residents.

There is too much uncertainty surrounding the issues of subsidence and water quality/supply to allow the project to be approved.

APPENDIX C

SUMMARY OF SUBMISSIONS RECEIVED BY THE PLANNING ASSESSMENT COMMISSION

The following is a brief summary of submissions received by the Commission. Submissions made at the Public Hearing on 28 October 2010 are marked with an asterisk (*). The key issues are discussed in various sections of the Commission’s report. Mr David Harris MP (State Member for Wyong and Parliamentary Secretary for the Central Coast)* raised the following concerns:

There is insufficient data in the water modelling to ensure that the regional water supply will be protected, and there should be a moratorium on mining until the impacts of mining on water tables is better understood.

Although dust emissions from the project would be within current standards, there is growing consensus that fine particulates need to be managed more strictly.

The social and economic impacts associated with loss of water supply have not been fully considered in the socio-economic assessment for the project.

Mr Doug Eaton (Mayor – Wyong Council)* raised the following concerns:

Council have been given insufficient time to present its view to the Planning Assessment Commission.

The proponent’s assessment of rail impacts doesn’t consider future increases in commuter and coal train traffic. Even a small increase in traffic will lead to delays, accidents and residents leaving the region.

There are many examples of subsidence from mining in the region and there is no compensation from the Mine Subsidence Board.

Wyong Council* commissioned Earth Systems (Mr Nigel Murphy) and Dr Phillip Pells to assess the Environmental Assessment. These companies raised the following concerns on behalf of Council: Aquatic Fauna The EA does not contain adequate baseline data, especially for aquatic fauna. The EA’s premise is that there will be no impact on surface water, therefore no baseline for aquatic fauna is needed. Water Quality The EA’s assumption of negligible impact on surface and groundwater is flawed. Construction, fuel spills and runoff from site have not been assessed adequately. Acid and metalliferous drainage is a particular problem. This was not considered in the EA because the coal seam in other areas is known to be benign. Community Consultation The proponent has failed to be open and engage the community in meaningful dialogue.

Environmental Management and Monitoring There is not sufficient detail on management and monitoring in the EA. A plan should be prepared prior to the assessment of the project and this has not been done. There is no indication that there will be sufficient budget for the proponent to manage and monitor key environmental impacts. Mine Rehabilitation and Closure The project needs to include some conceptual outline on the rehabilitation and closure of the mine to allow us to assess the impacts of the project. Problems with the Modelling In a uniform environment, rainfall builds up a water table. But, the real world is not homogeneous, so there are site-specific issues that need to be considered. The Terrigal formation has been used in recent years to develop borefields, providing up to 10-15% of Gosford-Wyong LGAs water supply. In the Terrigal formation, there are extensive pervasive structural joints which allow borefield extraction to impact across large areas of the groundwater aquifer. However, the model used in the preparation of the EA assumes that there are no rocks or faults and that waterflow occurs directly through the pore spaces. The model adopts laboratory permeability values 10 to 100 times lower than those measured in actual studies in area. It adopts coal and overlying rock permeability values 100 times less permeable than test data. The EA findings are almost completely dictated by two input parameters. The middle constrained zone is assumed to be the same permeability as the zones around it but SCT predictions suggest that permeability increases in this zone and that there is in fact no constrained zone. The EA adopts recharge values for the rock near the surface of 0.15mm/year which is way too low because rainfall is 600m/year. Permeability has been completely underestimated and should have been based on field values, not lab values. Because of the major flaws in the modelling, it is not known what the impact of the W2CP on the groundwater resources in the region. However, all indications at present are that there will be significant impacts on bores and streams. The present modelling doesn’t allow a proper assessment to be made of the likelihood of draining normal runoff water from the creeks and streams. Other Issues Design alternatives haven’t been adequately considered so the justification for the selected design is inadequate. Cumulative impacts haven’t been adequately considered. The risk assessment fails to identify some key parties and public risks and is too optimistic. In the benefit cost analysis, some values have not been accounted for, and waste streams have not been considered. The EA did not fully address the Chikarovski Inquiry. Not all Director-General’s Requirements have been met. All of these issues need to be addressed in a supplementary EA so that a proper assessment can be completed. The proponent should:

- Prepare an outline of environmental management plans, subsidence management plans and rehabilitation plans

- Revise the risk assessment and cost benefit analysis - Undertake more community consultation

Gosford Wyong Council Joint Water Authority* reiterated the submission from Wyong Council and noted the following points:

The Central Coast water supply relies heavily on this area – 13 % of the supply comes from Jilliby Jilliby Creek and 35% from the Wyong River.

There are significant uncertainties about the impacts on surface and groundwater. Further assessment of these issues is required. A risk-based model of likelihood and consequence is required and mitigation measures need to be clarified.

The Water Authority has had no meaningful engagement/consultation with the proponent.

Mr Greg Best (Councillor – Wyong Council)* raised the following concerns:

The proposed project would result in enormous long-term change beneath a large and growing residential population, and there has been a history of uanddressed subsidence in the region.

The Commission should consider the human impact of the project, not just the economic impact.

The Minister signs off on this project, but the government is also the beneficiary. This is not transparent and independent as the government stands to gain from the project.

Ms Dayan Noonan* raised the following issues on behalf of several residents:

A community group was assembled 10 years ago to develop the Ourimbah Protocol. Many of the issues raised during that work apply to the current project.

Loss of agricultural land remains the key issue. Atmospheric emissions are a concern and directly associated with the project. Carbon

dioxide and methane gas and coal dust can contribute to forest growth, which is beneficial. The elephant in the room is fine dust, which is present wherever coal mining and transportation occur.

Mr Bruce Cross* raised the following issues: The project will be very visible from my property. There will be noise impacts that will affect my property from day one. All residents in the local area rely on tank water for domestic supply and dams for

agricultural supply, and coal dust will enter these systems. Machinery for reclaiming coal from stacks creates an enormous amount of dust and the rail line will be within 500m of residents.

Freight trains cause trouble now with breakdowns in the corridor. With an extra 7 trains a day there will be a significant load on the railway line. Traffic estimates in the EA are off because traffic volumes have increased significantly in the last 2 years.

Surface water impacts require another 2 years of study. Where will the saline water from the mine go? Into the creeks and water supply?

Mr Albert Bywater* submitted a number of photos and raised the following issues:

There will not be a sufficient buffer zone around the mine. The project will be visible from my property. The land surrounding the site is constrained.

The proponent’s Response to Submissions stated that consultation took place with me. In 1999, Kores spoke to us about purchasing the property, but the offer was not accepted. This was the extent of the consultation.

Ms Sue Wynn (Councillor – Wyong Council)* raised the following concerns:

If the Part 3A legislation did not exist, the project would have come to Council, who would have asked for more studies into the impacts.

The project will adversely impact the water supply for the region’s growing population.

All longwall mines have detrimental environmental impacts. We know that the groundwater and rivers will be ruined. Look at examples in Blue Mountains, South Coast, Lake Macquarie, Xstrata Mines and surrounding creeks, and Mandalong coal mine. Coal is being exported, but the environmental damage is felt here.

The premise for this mine is false. The modelling is based on incorrect data. The proponent’s extrapolation is false.

Over the last 25 years our air quality has deteriorated and this mine will add to the poor air quality in an area with the highest rate of asthma in Australia.

Damage is irreparable and condemns future generations to live in untenable areas. Mr Bill Keegan* has been a resident since 1963 and run dairy farms and turf farms in the region. He raised the following concerns:

If the water in Jilliby Jilliby Creek goes, our business and the employment of 10 people goes.

Dust from the coal mine will go everywhere, beyond the boundaries of the site. Land values will decrease because flats will turn into swamps. At Buff Point, 26 houses were lost so subsidence follows wherever underground

mining occurs. Coal companies are located overseas so they won’t be concerned with addressing

these impacts. Mr Michael Campbell* tabled a petition of 30 landowners and residents declaring that they have not been directly approached by the proponent regarding the impacts of the project. He made the following comments:

Lack of consultation is a breach of the Director-General’s Requirements and the project should not proceed until this has been addressed.

Mr Alan Hayes cannot attend due to illness. BHP walked away from the project in its infancy because they realised the potential

problems associated with the project. The massive coal reserve is like a golden egg for the government. It is unclear

whether the project is for 28 or 42 years, which reflects the general inadequacy of the EA.

The letter from the Department of Health did not appear in the Response to Submissions and was not available from the Department of Planning. The letter is concerned with the respiratory health impacts of project, even if they are below limits. Air health quality problems have now been exposed and this puts paid to the air quality health study in the EA.

This area of the valleys was proclaimed a water catchment in 1950 and protected, but Part 3A has wiped away the value of this proclamation.

Mr Ken Scales* raised the following concerns: The area affected by air issues includes residential areas and schools. There will be a

6% increase in mortality rate as a result of fine dusts. Coal dust impacts are cumulative and there is no guideline in Australia for ultrafine particles. The risk of mortality assessment overlooks the around-the-clock nature of the project and the prevailing winds in the region.

This mine is based on greed, it doesn’t need to use panels or go under water. It requires expensive rail infrastructure in the middle of a residential area. This is a waste of infrastructure because there are empty trains already using the line and passing the site. Coal trains are slow and dangerous and conflict with high speed commuter trains. Coal should be used for local power production to lower electricity prices (e.g. at Munmorah).

The laws that support levies on coal are outdated and laws protecting other land users’ rights should overrule this legislation.

Mr Wayne McCauley* raised the following issues:

Kores state there have been no complaints about their website, but this is not true as I have submitted a complaint. The website was not updated regularly and, if it was, any updates were incorrectly referenced.

Kores state that they held one-to-one discussions with residents, that they sent 14 newsletters to all residents in the area and established a webpage containing minutes of Community Liaison Committee meetings, press releases and statements. This is incorrect. I have only ever received one newsletter and never had a one-to-one meeting. Kores has embellished the level of consultation.

The resident survey was flawed and should be rejected. The survey report is from 2006, used 2004 telephone numbers and is for an EA in late 2009.

The EA continually says there will be no impact from the project, not that the level of risk is acceptable. It is impossible to have no impact.

The EA relies on assumptions which were based on inadequate data. The modelling predictions are inaccurate. The risk to the water supply catchment is too great to allow it to proceed.

Mr David Burgess (Total Environment Centre)* raised the following issues: Risk Assessment The level of stakeholder involvement, the availability of necessary data, the identification and analysis of specific risks, and the reasonableness of risk evaluation outcomes are all problematic in this project. TEC feels that the risk assessment was not open and responsive and excluded stakeholders. At the very least, council and key agencies should have been involved. Data availability was poor for the risk assessment, so the assumptions in that assessment were ill-founded. There is no feedback between risk management and the identification of key issues. Several documents were unavailable when the risk assessment was released (including the subsidence assessment, ecological assessment, and the heritage assessment). Hydromorphology and health assessments were released concurrently with the risk assessment. Therefore the four key risk issues were not addressed prior to the preparation of the risk assessment and did not inform it.

The evaluation did not identify any high or extreme risks, probably because ratings are arbitrary or inconsistently categorised. For example, the impact on drinking water supply is rated at 4e, which is for assets valued at less the $150,000. The water supply is actually worth at least $46 million at current prices. Loss of 1% of the water supply is worth about $500,000 per year to the Central Coast community. Water Supply The EA has been developed without the key data elements recommended by the Chikarovski review. The risk assessment has not identified the specific risks to water supply, including water quality from erosion due to subsidence, acid leakage, rock cracking, and loss of total water volume due to leakage. No modelling is provided to support the claim that the overall impact of the project on water supply will be positive. Subsidence A significant portion of the catchment will be affected by subsidence. The EA does not identify specific formations that will be affected by subsidence (which has been done for other recent longwall mine assessments). Subsidence will occur in the lower reaches of the catchment but no risks to the lake have been identified. The aquifers have not been fully mapped so the modelling is inadequate. There is no specific information on the monitoring and management of the water table. Mr Warwick O’Rourke (Australian Coal Alliance)* raised the following concerns:

I object to Professor Galvin’s participation in the PAC due to potential predispositions because of his involvement in the Chikarovski review.

The Chikarovski review noted that there is a lack of information relating to groundwater in general, but particularly the aquifer, groundwater use records and plans, lack of government management and lack of community involvement in groundwater monitoring. Without benchmark measurements prior to the establishment of mining, it will not be possible to measure impacts into the future. Lack of data also affects the accuracy of models.

I have had correspondence with the Department of Planning regarding the review of groundwater modelling for the project. This correspondence says that, in SKM’s view, the two years of modelling data should only be conducted if W2CP is approved. Mr Evans’ statements at Monday’s meeting seemed different to this. Mr Evans also said he was not invited to attend the PAC hearing.

From the Chikarovski review to present, virtually no data availability improvements have been made in the Wyong region. The Wyong Water Study shows the number of bores in the vicinity of the project. There were 5 new observation bores in 2010 on proponent-purchased property that don’t feature in the EA because they post-date the exhibition of the EA.

Many of the comments in the Wyong Water Study are at a strategic level, but there are others that make a quantitative assessment of the impact of the Wallarah 2 coal project (e.g. quantification of subsidence levels). The Wyong Water Study states that a lack of monitoring data is a problem for the quantitative assessment of projects (this is not a general strategic statement but a specific statement about assessing mining projects in the study area).

There has been considerable inactivity around the lack of data on groundwater and geology in the region. The Wyong Water Study (section 10.3) states that there is primary data insufficiency on groundwater. Regular monitoring should be undertaken for a period of two years.

The PAC needs to be informed about this issue by speaking with Mr Evans in a public arena. The Chikarovski report notes the absence of data, as does Mr Evans, so this needs to be further investigated by the PAC.

Mr Tony Kirk* raised the following concerns: No meaningful work on the geology of the region has been done in the last 20-30

years. BHP left the area because of environmental concerns. The geology of both valleys is complex. There are recognised features such as faults, fractures and dykes.

Longwall mining has little flexibility and high development costs. The mine is designed to fail (goaf) and can cause surface subsidence as far as 1.5 kilometres away from the mine site. Subsidence can cause water table problems, drain waterbodies and damage infrastructure. This is despite the best available practices.

Kores have done almost nothing to improve our knowledge of the area and the potential impacts, and have made a hurried effort to establish baseline data. This method is flawed and cannot provide sufficiently accurate data.

Mr Jim Thomson* raised the following concerns:

The overwhelming majority of submissions oppose the project. The project is opposed by the general Central Coast community, the Valley

communities, the Australian Coal Alliance, the Stop Korean Coal Mining community, the Chain Valley Bay community and the Calga, Kariong and Peats Ridge communities, the Climate Action Group Central Coast and the councils.

There have been lessons learnt from mining under the Cataract River that should not be repeated here. These lessons include the effect of mining and cracking on groundwater loss and diminished baseflow.

There is a lack of adequate baseline data with which to model groundwater. The Commission is made up of experts at fixing problems, not avoiding them in the

first place. Mr Garry Prince* raised the following concerns:

Disruptions to the rail system can be painful for commuters. There are also dust and noise problems for residents along the rail corridor. The traffic study in the EA is outdated. Chain Valley Bay mine has since then

increased their truck movements on the same road network (570 truck movements a day). Truck transport is not acceptable for this project because local roads can’t take that level of traffic.

Subsidence is a problem in the area and will be into the future. Residents are still fighting for compensation from Chain Valley Bay incident 28 years ago.

The construction of the Western Shaft will involve 62 weeks of truck movements down a little local road. Construction work in the State Forest has not been given approval.

Mr Ronald Sokolowski* raised the following concerns on behalf of himself and Mr Alan Hayes:

Minister Sartor stated that future growth in the region must be satisfied – this mine will not satisfy future population growth.

The national water initiative should take precedence over any other policies. It is a proclaimed water supply catchment and should not be subject to subsidence.

The PAC has been unable to investigate the Chikarovski Inquiry because they weren’t appointed before the EA was exhibited and were not privy to the Wyong Water Study. The NSW Government reneged on their commitment.

Critical data collection must occur to allow a detailed assessment to take place. Independent review of the Wyong Water Study is recommended during two further years of data collection.

The NSW Government has breached the National Water Agreement, the Water Management Act 2000, and the precautionary principle.

33 species and 19 migratory birds use the area. Mr Evans’ view is that further information is required before the project can be

approved. This project fails to satisfy the National Strategy for Ecologically Sustainable

Development (2002) and several critical acts relating to the protection of water resources.

The mine is incompatible with the protection of our water supply because there will be subsidence in the valleys.

The proponent advances guarantees of security regarding environmental impacts. Independent consultant hydrologists have confirmed there is connectivity between aquifers, contrary to what the proponent says.

The Chikarovski report found that longwall coal mining is likely to cause subsidence in the water supply catchment. However, because of the depths of coal seams, there will be no impact on the water supply of the Central Coast. I reiterate the criticism of the science behind groundwater modelling in the EA. The recharge of aquifers will take 200 years.

The Chikarovski report reaffirms that without benchmark measures prior to mining, it will be impossible to substantiate cause and effect. The weaknesses of data have been ignored by the proponent.

There is no evidence of a catchment management plan guiding the development of the valley or the project.

Some 37 creeks and streams have been identified as being affected by coal mining in northern and southern coalfields of NSW.

Mr Warwick O’Rourke (Individual)* raised the following issues:

The PAC did not review the EA prior to exhibition. The proponent talks about the IBM method being inappropriate even though it has

been regarded as the best method available for modelling. However, the project is unique because it is uniquely deep and will extract up to 4.5m of coal (not 3m) and the near seam structure is weak (not strong) and the overburden is finer.

A modified model was developed to reflect site specifics but based on the southern and Newcastle coalfields, even though they have just said that these environments are not representative of the subject site.

The modelling was verified by comparing results with the Ellalong colliery which is not even in this mining region.

The model is not applicable to our unique Central Coast mining geology. In reference to the Bickham mine, if the water supply for the Hunter Valley thoroughbreds deserves protection, then the water supply for 300,000 residents should also be protected.

Ms Mira Wroblewski (Climate Action Group Central Coast)* raised the following concerns:

Greenhouse gas emissions targets need to be reduced by 60-80% of current levels to raise temperatures less than 2.4 degrees. New coal mines are completely incompatible with what needs to be done to address climate change.

The company has repeatedly downplayed the role of mining and energy generation in climate change (25% of emissions, when it should be 40%). But even if we accept this, 25% is not a small contribution. The export of coal for energy generation as a result of this mine will contribute 86% of the total emissions associated with the project.

The emissions from the coal burnt from this mine is equivalent to 2.9 million extra cars on the road every year for 28-42 years.

There are large direct and indirect government subsidies ($4-6 billion p.a.) given to coal production in Australia which lower its price on the world market and generate private profit. These subsidies should be spent on social infrastructure. We need to consider our responsibility for exporting coal and the consequences for the climate.

By comparison, subsidies for renewable energy in Australia are pitiful. A 2008 Newspoll survey found that 90% or respondents supported more subsidies for renewable energy.

The proponent stated that this project will help South Korea to meet its greenhouse gas emission obligations because the coal is a higher quality than they currently use. This is nonsensical, they should just be weaning themselves off coal altogether.

The proponent states that renewables can’t meet all global baseload energy demand. This is part of their project justification and is not true. It is not true that coal is cheap, and it is not true that demand is increasing. Other nations are pursuing renewable targets much more ambitious than Australia.

The project does not meet the Director-General’s Requirements in terms of ecologically sustainable development and intergenerational equity.

Mr John Lewer (Stop Korean Coal Mining)* provided the information DVD that the proponent distributed in the community and raised the following issues:

The Information DVD is inaccurate. West of Wyong is actually residential an dthere are residents within 700 metres of the coal loader site.

They will not mine under rivers but they also say that subsidence is not vertical, so the separation from rivers is inadequate.

There is no current mining near Wyong - the closest is under Lake Macquarie. The clay quarry and tile factory aren’t as visually imposing/dusty as implied in the

DVD. The presence of sewage treatment works is not an indication of a downgraded area. Buttonderry waste facility is west of Hue Hue Road and is not a waste producer. The presence of the F3 freeway, the railway line and transmission lines aren’t

indications that the area is heavy industry and therefore a coal mine is acceptable. The coal dump is not hidden from view and is within 2 kilometres (not 3) of residents. Wallarah Creek and Spring Creek run right through the site and both will be affected. Jobs and construction investment are overstated.

Ms Caroline Graham (Rivers SOS)* raised the following concerns:

The Cataract River is an example of what can happen if mining occurs.

The river was in good condition in the 1970s, then after mining in 2002 iron oxide sludge appeared as a result of the fractured bedrock of the river.

The Nepean was cracked by mining 180m away by BHP. Rivers SOS are campaigning to have a 1 kilometre exclusion zone around rivers.

River protection from mining has been called for by 5 commissions/panels of experts in NSW since 2000.

The best way to manage the community outrage is to excise sensitive river areas from mining projects.

There is just not enough detailed research into modelling for groundwater and subsidence. There are also always ‘anomalies’ and predictions are never guarantees. Rehabilitation costs millions.

All experts agree that damaging impacts can occur a lot further away from the predicted angle of draw.

There are serious problems with the advice from government agencies because their experts are gagged and scared. Government agency experts are also unaccountable like mining executives. They are not blamed if adverse consequences happen.

There was a recent FOI application that revealed SCA and the Department of Energy were concerned about mining under water supplies.

What experts do the Department of Planning rely on and how are their recommendations taken? Is SKM gagged because of their work for BHP elsewhere? Ray Evans had to differentiate between his professional and personal views. Even consultants aren’t independent.

Providing reports that are false and misleading is illegal but this is not enforced by authorities.

Remediation has not been adequate or successful in the southern coalfields. Ms Sandra Norman* raised the following concerns:

Water is the single most precious resource. Any activity that risks it should not be permitted.

This project is part of a wider exploration area and the mine will likely expand into a greater area in future.

The valleys are a significant part of the water supply catchment. The applicant acknowledges subsidence, and subsidence will affect the aquifer and

the water supply. Many rivers have been damaged by mining in this state. Historical evidence has eroded community trust. The Government has a duty of care to protect the health and property of the people in

this community and should apply the precautionary principle. Alternatives need to be considered like ‘no action’. 200 years to recharge the aquifer is a huge delay – seven generations. The PAC should just recommend that the project be avoided, not mitigated or

managed. Mr Jack Cambourn* raised the following concerns:

The subsidence damage in Chain Valley Bay was considerable and costly. Management were found guilty of breach of conditions. There is a conspiracy to hide the real story behind subsidence in Chain Valley Bay. There is still a bit of subsidence occurring 21 years after the initial problem.

The compensation offer from the government ended without residents being told in the mid 1990s. The Mine Subsidence Board did little or nothing to compensate property owners. Chain Valley Bay residents are working with the Australian Coal Alliance to expose issues and protect others under threat from subsidence.

Mr John Barrow* provided a copy of an article from the Newcastle Herald regarding the impact of mining on groundwater and surface water, and an image depicting Chain Valley Bay. Mr Barrow raised the following concerns:

The mining industry has a history of illegal mining and causing major damage. Rivers, creeks, wetlands and human settlements have been badly damage by mines in

the Southern Coalfields. It is difficult to extract funds from mining companies for rehabilitation works. Run off from the project will adversely impact on Wallarah Creek. Mining companies have little regard for the environment. Schools are going to get coal dust from the W2CP project. So are schools in

Warnervale Town Centre. San Remo school has 1200 students and is within 4 kilometres of the coal stockpile. We don’t want to leave that legacy for this area. We don’t want another 42 years of mining. Hospitals will be unable to cope with the sick population. Chain Valley Bay had a massive increase in respiratory illnesses when coal mines started.

This area occasionally gets massive storms. How will runoff from site be managed in these events? How will creeks and rivers and lakes be protected from runoff?

Mr Keith Bowman provided a copy of a study by the Colong Foundation for Wilderness into the impact of mining on the Gardens of Stone National Park and suggested that similar issues would result from the Wallarah 2 Coal Project. Mr Bowman raised the following:

The impact of the mine on regional hydrology needs to be assessed transparently and independently.

The State Government has a conflict of interest because of the royalties it receives from mining.

The project will provide fuel that will increase carbon concentrations in the atmosphere;

Miners regularly deviate from the mine plan to increase productivity regardless of the impacts on geology and hydrology.

The mine will lead to a reduced flow pattern in watercourses. Water pumped from the mine will pollute watercourses.

Mr Laurie Eyes quoted Mr Ray Evans’ statements at the meeting organised by the Department of Planning at Wyong Council on 25 October 2010. He raised the following concerns:

The recommendations in the Wyong Water Study may have been altered and do not reflect Mr Evans’ view that 2 years on monitoring is required prior to any mining approval.

The cessation of bore sampling seven years ago was meant to deprive the mine application of information.

High level aquifers and the coal seam may be interconnected, and the origin of coal seam water is critical to the assessment of the project.

These issues should be investigated by the PAC prior to the determination of the project.

APPENDIX D – WYONG STRATEGIC REVIEW

In February 2007, the NSW Government appointed an Independent Expert Panel to conduct a strategic inquiry into potential coal mining impacts in the Wyong Local Government Area (Wyong LGA). The Panel was asked to examine and report on the following terms of reference:

1. Whether coal mining under the catchment of the Mardi Dam would compromise, in any significant way, the water supply of the Central Coast;

2. Environmental impacts of any underground coal mining, with particular emphasis on:

surface and groundwater resources, especially on drinking water supply and flooding;

hazards and risks of subsidence impacts; and

the amenity of the community, including dust and noise impacts;

3. Social and economic significance of any underground coal mining to the local community, the region and State; and

4. Areas where mining should not be permitted, or if permitted the conditions under which it may proceed, having regard to the matters listed above and the NSW Government’s strategic planning policies that apply to the area.

Summary WSR Findings and Recommendations The Wyong Strategic Review Panel prefaced its findings (DoP, 2008a) with:

Mardi Dam has a very small catchment of its own but it stores water pumped from the Wyong River….. The Panel has therefore interpreted the terms of reference (TOR) as including all catchments which supply Mardi Dam, largely being the catchments of the Wyong River and Jilliby Jilliby Creek.1

Finally, it is important to note that the TOR are broad – they cover the entirety of the

Wyong LGA. They are not focused on any particular mining proposal, including Wallarah 2. The Panel was required to, on a number of occasions, clarify that the Inquiry relates to all proposed future mines within Wyong LGA, including both Wallarah 2 and sites either not yet proposed or potentially not even identified. Nonetheless, the Inquiry was set up against the backdrop of the Wallarah 2 proposal, and considers that it is important to, wherever possible, provide specific comments on Wallarah 2. It has been limited in this role insofar as the Wallarah 2 project has not yet reached the stage of submitting an environmental assessment for public exhibition and assessment under Part 3A of the EP&A Act. Consequently, not all background data has been put into the public domain by the WACJV. For this reason, and others,

1 Water is also transferred to Mardi Dam from Mangrove Creek Dam via a tunnel feeding into the Wyong River.

the Panel should not be seen as analogous to an independent hearing and assessment under Part 3A into the Wallarah 2 proposal.2

Key findings of the Wyong Strategic Review relevant to the Wallarah 2 proposal were:

1. On the weight of evidence presented to it, longwall mining is likely to cause subsidence-related impacts within the water supply catchments associated with Wyong River and Jilliby Jilliby Creek. However, because of the depth of the coal seams, this subsidence is unlikely to compromise in any significant way the water supply of the Central Coast, since the nature of the geology, geomorphology and depth of the coal seams make it unlikely that underground mining will result in a loss or contamination of surface water.

2. With appropriate mine planning, there is also little likelihood for deterioration in the quality of surface waters or contamination from hard rock saline aquifers.

3. In the absence of major, unforeseen geological anomalies (eg faults and dykes), subsidence-induced hydraulic connectivity between Wyong River, Jilliby Jilliby Creek or their alluvial systems and any underlying mine workings is extremely unlikely.

4. There is a lack of information relating to groundwater in the Wyong LGA in general. Of particular concern are a lack of monitoring of aquifer status, lack of metering of groundwater use, the absence of groundwater sharing plans, the lack of government investment in groundwater management and the lack of community involvement in effective monitoring of groundwater.

5. However, based on the available data, while groundwater does make a significant contribution to the water supply of the Central Coast (estimated to be between 3.5 and 6%), any mining activity would not significantly impact on the existing groundwater levels or groundwater availability.

6. In relation to the Wallarah 2 mining proposal, impacts arising from upsidence are likely to be minimal given the distance that mining is planned to stop short of the Wyong River. Given the wide and flat nature of the valley in which Jilliby Jilliby Creek is located, upsidence could also be expected to be minimal. Impacts arising from upsidence are also likely to be minimal because of the nature and thickness of the alluvial deposits and underlying strata.

7. .....based on the information available, damage to water supply infrastructure is extremely unlikely to arise from either direct subsidence effects or far-field horizontal movements.

8. In relation to flooding, the Panel is not in a position to express an opinion on or conduct an independent review of these matters (e.g. increased frequency of flooding, increased risk of flooding, change in flood levels). The Panel considers that there is a likelihood of some change in the distribution and extent of ponding, due to mining-induced subsidence.

9. Subsidence impacts are site specific and a lack of sound and comprehensive baseline information has limited the ability of the Panel to draw firm conclusions on the hazards and risks of likely impacts of underground mining in the Wyong LGA.

The Wyong Strategic Review Panel stated that its recommendations should apply to any

2 DoP (2008a), p7.

future coal mine development within Wyong LGA, including the Wallarah 2 proposal. These included:

1. Increased focus should be given to risk assessment in the environmental impact assessment process, and that a rigorous, standardised risk assessment process be developed and implemented by relevant government agencies in consultation with affected mining companies, representative bodies and the community.

2. Future coal mine proponents in the Wyong LGA should be required to demonstrate a strong commitment and systematic approach to keeping the community informed and responding to community concerns.

3. The Department of Planning and other relevant approval agencies should require future coal mine proponents to provide evidence of a clear, transparent and accessible community consultation process through the preparation of communications and engagement plans.

4. Any new coal mine project application should include comprehensive information concerning both the above-mentioned consultation and the potential social and economic impacts identified as part of the social and economic impact assessments.

5. In relation to groundwater and surface water resources:

a) all groundwater bores, other than low yield domestic and stock bores, should be metered;

b) for non-metered bores, annual reports of estimated usage should be a requirement of the access licence;

c) State Government funding should be allocated for development of a systematic monitoring network with automatic data logging;

d) the Wyong River Water Sharing Plan should be completed and issued as soon as possible;

e) macro water sharing plans for groundwater should be completed and issued as soon as possible; and

f) a flow gauging station should be installed at the downstream end of Porter’s Creek.

6. Subsidence impacts from new underground coal mines within the Wyong LGA should be mitigated such that affected privately-owned dwellings will be in accordance with Wyong Shire Council’s Flood Prone Land Development Policy after mining is completed (either by impact minimisation or rectification), or otherwise subject to appropriate compensation.

7. That because of the significant environmental, social and cultural values of Tuggerah Lake and the potential for mining subsidence to impact on these values, no mining causing subsidence of the Lake should be approved unless a high level of knowledge about the Lake’s ecology and hydrology (including seagrasses, tidal flows, currents, water quality and mixing) has been demonstrated and sufficient certainty and assurance provided to ensure that there would be no unacceptable adverse impacts on the Lake or its key values.

8. Any new coal mining proposal that would impact on wetlands in the Wyong LGA should provide appropriate offsets to meet the ‘maintain or improve’ principle.

9. The Department of Environment and Climate Change should consider reviewing its current air quality standards, particularly the existing deposited dust standard, and establish new standards for smaller particulates to ensure that such standards are consistent with current scientific knowledge and community expectations.

10. Any coal mine surface facility which is near residences should be required to comply with world’s best practice in relation to coal stockpiling, storage and dust emissions.

11. Further mining in the Wyong LGA should be subject to a comprehensive socio-economic cost/benefit analysis which takes into account the direct and indirect cost and benefits, including likely employment gains from mining and risks to residential growth, current and future employment and property prices.

12. There is potential to relax or remove some of the current constraints on new developments east of the F3 freeway in the Wyong LGA. There may also be potential to relax mine subsidence related restrictions on building codes in some parts of declared mine subsidence districts west of the F3 Freeway. A planning forum involving all relevant government agencies and other key stakeholders should evaluate options for future mining-related development controls in the Wyong LGA.

13. In respect of the Wallarah 2 Project proposal:

a) subject to the recommendations contained within this report, the Wallarah 2 proposal should be assessed under Part 3A of the Environmental Planning and Assessment Act 1979;

b) consideration should be given to an independent review of the final Wallarah 2 proposal as part of the Department of Planning’s assessment process;

c) given the proximity of the proposed Wallarah 2 surface facility to residential areas, noise and dust emissions from the proposed surface facilities should be minimised as recommended in this report;

d) If these emissions are unable to be satisfactorily minimised, the Wallarah 2 proponent should review the proposed location and size of its coal stockpile, including the potential for it to be moved west of the F3 Freeway;

e) the Wallarah 2 proposal should apply best practice community consultation, engagement and participation (eg NSWMC and DoP guidelines); and

f) Wyong Shire Council and the community should be encouraged to allow water monitoring stations to be installed and accessed to allow for better collection of baseline and monitoring data.

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APPENDIX E. WYONG WATER STUDY AND PEER REVIEW

The Wyong Water Study1 was commissioned by the Department of Planning in April 2010 to address the concerns expressed in the Wyong Strategic Review regarding the lack of information relating to groundwater in the Wyong LGA. The study was undertaken by consultants Sinclair Knight Merz (SKM, 2010). The brief for the study required the consultants to “assess and document the current status of groundwater and surface water information in the western part of the Wyong LGA, and to make prioritised recommendations for actions to improve the situation if current monitoring activities are found to be inadequate”2. The consultants were asked to address six key issues, including:

“the status of modelling activities (groundwater flow; rainfall-runoff; flood routing)”

“the adequacy of current surface and groundwater monitoring”; and

“the sufficiency of this information for baseline purposes, with particular reference to sufficiency for assessing the potential impacts of the Wallarah 2 Coal Project”.

The study was undertaken with the consultants knowing that their work would be subject to international peer review. A review was subsequently undertaken by Aqualinc Research Ltd (Aqualinc, 2010).

E.1 SURFACE WATER

The study reviewed three sets of data that are relevant to the current review:

The long term flow records that provide an indication of the surface water resource available to meet the needs of the environment, private landholders and the water authority;

The low flow characteristics of the main watercourses and the proportion of flow that can be attributed to baseflow derived from groundwater;

The adequacy of the records for flood assessment purposes.

E.1.1 Long Term Flow Records

In relation to surface water data, the study identified four flow gauging stations on the major creeks with records ranging from 25 to 30 years duration:

Wyong River at Yarramalong (211014) (commenced January 1973);

Wyong River at Gracemere (211009) (commenced January 1973);

Jilliby Jilliby Creek at Durren Lane (211010) (commenced November 1976);

1 SKM (2010), page 23 2 SKM (2010), Section 1.2

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Ourimbah Creek upstream of the weir (211013) (commenced November 1976).

The study did not consider the flow records for Mangrove Creek which, although it lies outside Wyong LGA, is an important element in the water supply system operated by the Gosford-Wyong Councils Water Authority (GWCWA). The records quoted above have been utilised by the GWCWA as the basis for calibrating runoff models for purposes of assessing the long term availability of water to meet the demands of the growing population on the central coast (GWCWA, 2007) . The study also identified two other sites that could be of relevance, but which have only shorter term records:

Jilliby Jilliby Creek at Olney (211004) (1959 – 1966);

Wallarah Creek at Warnervale (211006) (1966 – 1977).

The potential relevance of the gauging site on Jilliby Jilliby Creek at Olney lies in the fact that it is located in the steep headwaters of the creek and would provide a useful “baseline” station for monitoring an example of a headwaters catchment that would be unaffected by mining. The potential relevance of the gauging site on Wallarah Creek at Warnervale lies in the fact that it located downstream of the proposed Tooheys Road at which coal stockpiling and loading is proposed. This site would be of most relevance for water quality measurement and for verification of any agreed licence regime for discharge of surface runoff from the Tooheys Road site. The peer review of the Wyong Water Study undertaken by Aqualinc Research Ltd (2010) noted that the report did not provide any comment as to whether the flow data from Ourimbah Creek was representative of the flow regime in Wyong River and Jilliby Jilliby Creek, and could therefore be used as an out of catchment control site for purposes of assessing any impacts associates with coal mining. However, given that any subsidence impacts are likely to have maximum effect, if any, (in terms of possible surface cracking leading to loss of streamflow) in the rocky headwaters catchments, any consequences (in terms of loss of flow) would be difficult to detect in catchments as large as Ourimbah Creek, Wyong River or Jilliby Jilliby Creek. Any control sites to monitor the flow regime in a catchment unaffected by mining would need to occur on a much smaller catchment located in the steep headwaters of a river or creek. The peer review also noted that there is no gauging site upstream of the proposed mine footprint and concurs with the recommendation in the Wyong Water Study that the gauging station on Jilliby Jilliby Creek at Olney (211004) should be reinstated for purposes of providing headwaters a “control” catchment unaffected by mining. The Commission endorses this recommendation and the recommendation that the gauging site on Wallarah Creek (211006) should be reinstated. The Wallarah Creek gauge would provide a reference location for monitoring discharge and water quality downstream of the Tooheys Road site.

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E.1.2 Low Flow Characteristics

The Wyong Water Study recognised the inherent uncertainty of low flow measurement at sites that rely on natural hydraulic controls and noted that gauging sites except the gauge on Jilliby Jilliby Creek at Durren Lane remain stable over time. In the case of Jilliby Jilliby Creek at Durren Lane sufficient periodic re-rating of the gauging station has been undertaken to capture the inherent instability of the control section. The study included an analysis of the proportion of total flow that comprises baseflow using a mathematical filter technique. The report notes that:

“Baseflow separation using the digital recursive filter is not intended to give a precise estimate of baseflow, rather it typically provides an upper bound value which is conditioned by the available streamflow in the river. The advantage of the digital recursive filter is that it is easy to apply and allows comparisons of baseflow estimates between sites and over time.”3

The study also notes that:

“In general, estimates of baseflow using the digital recursive filter will be an upper limit of likely baseflow, because this estimate typically includes a component of interflow through the unsaturated soil profile and release of flow from bank storage following flood events.”

Table 1 is a copy of the data in Table 4.4 of the Wyong Water Study which has been rearranged in order of increasing catchment size for the two watercourses. The data in Table 1 indicates three aspects of note:

Percentage of flow attributable to baseflow is significantly higher for Wyong River than for Jilliby Jilliby Creek;

There is a slight trend for increasing baseflow contribution with increasing catchment size.

Table 1: Baseflow Estimates

Gauging Station Wyong R

@ Yarramalong (211014)

Wyong R @ Gracemere

(211009)

Wyong R @ Wyong (211002)

Jilliby Ck @ Olney (211004)

Jilliby Ck @ Durren L

(211010)

Catchment Area (km2) 181 236 249 8 92

Period of Analysis 1976-2009 1972-2009 1959-1966 1974-1989 1972-2009

Mean Baseflow (ML/day) 28.8 43.6 60.2 1.5 13.1

Summer Mean Baseflow (ML/day) 24.3 34.9 61.1 1.2 10.6

Baseflow Index 25% 28% 28% 14% 17%

(Source: Table 4.4 from Wyong Water Study, 2010)

3 SKM (2010), p23.

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Whilst the baseflow analysis is subject to the caveats quoted above, it provides a useful indication of the order of magnitude of baseflow as a proportion of the total flow. As noted in the report the estimates of baseflow derived from the analysis are generally consistent with other estimates provided by:

DWE estimates of groundwater contribution of 14% of flow for Wyong River and Jilliby Jilliby Creek (as quoted in the Wyong Strategic Review)4

Estimates of groundwater contribution of 11% derived from groundwater modelling undertaken for GWCWA5

The peer review provided little comment in relation to the base flow analysis undertaken as part of the Wyong Water study except to:

Note the absence of any baseflow index for Ourimbah Creek;

Acknowledge the value of supplementary water quality data in assessing the baseflow component. However, Aqualinc appear to have misunderstood the methodology utilised by SKM and CSIRO6 which uses naturally occurring water quality characteristics, principally electrical conductivity, rather than artificially injected chemical tracers.

The Commission considers that water quality monitoring for purposes of improving the estimation of baseflow is not warranted in itself. However, where appropriate water quality data (particularly continuously monitored electrical conductivity) is being collected for other purposes, the use of that data to assist with the estimation of baseflow should be considered, particularly on any monitoring of headwaters catchments established to assess possible consequences of mining on the flow regime.

E1.3 Flood Estimation

The Wyong Water Study noted that information relating to flood frequency and area of inundation information was summarised in the submission by the proponent to the Wyong Strategic Review. Whilst the details of the flood analysis were not obtained for the Wyong Water Study, the information presented in the submission suggests that surface water monitoring data was sufficient to estimate design flood peaks and to develop a hydraulic model to estimate design flood extent.

4 Impacts of Potential Underground Coal Mining in the Wyong Local Government Area: Strategic Review, NSW Department of Planning, July 2008, p62. 5 Alkhatib, M and Merrick, NP (2006), Groundwater Simulation and Optimisation Modelling of the Kulnura – Mangrove Mountain Aquifer Systems, Final Report for Gosford-Wyong Councils Water Authority, Research Report NCGM 2006/14, November 2006 6 Methods for Estimating Groundwater Discharge to Streams – Summary of Field Trials. Draft V1. Report prepared by SKM and CSIRO for the National Water Commission, July 2010 (quoted by SKM – not sighted)

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E1.4 Water Quality

The Wyong Water Study provides a summary of the number of monitoring events for a range of water quality parameters analysed by public agencies. The data summary in Appendix C of the Wyong Water Study shows that for both monitoring stations of most relevance to the W2CP (Wyong River at Gracemere and Jilliby Jilliby Creek at Durren Lane), much of the data was collected prior to 1990. For the Wyong River at Gracemere, the current monitoring appears to be confined to EC, NOx, TP, FRP, Turbidity and pH. For Jilliby Jilliby Creek at Durren Lane there is no data listed as being recorded since 1990. Unfortunately the Wyong Water Study overlooks the water quality data collected in connection with the W2CP which is documented in Appendix D of the EA. That dataset includes samples collected at approximately monthly intervals over the period July 2006 to December 2009 at the following sites:

Yarramalong and “Gracemere” on Wyong River;

Little Jilliby Jilliby Creek at Jilliby Road.

Four sites on Jilliby Jilliby Creek including one upstream and one downstream of the proposed mine footprint;

Hue Hue Creek at Hue Hue Road;

Buttonderry Creek at Hue Hue Road.

In summary, the Wyong Water Study notes that surface water quality information has been widely collected and includes electrical conductivity data which could be used to separate groundwater from surface runoff. No comment is made in relation to the adequacy of the suite of parameters or the frequency of data collection for purposes of characterising the overall water quality and ecosystem health of the river systems. The Wyong Water Study stated inter alia:

Sampling for water quality across the monitoring network should be undertaken on a periodic basis across the life of the proposed mine, so that impact analysis can be undertaken;

The peer review by Aqualinc notes the paucity of recent water quality results and suggests that any sites that are used to assess baseline conditions should have at least two years of relevant data prior to any mining activities that are likely to affect surface water quality:

All groundwater level, groundwater chemistry, stream flow, stream chemistry and climate sites that are used to determine baseline conditions should have at least two years of relevant data prior to the commencement of mining activity that is likely to affect surface water or groundwater flows or quality;

E.1.5 Land Use Change

Progressive changes in land use can lead to changes in the hydrologic response of catchments including peak flow and catchment yield. The Wyong Water Study identifies factors such as

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changes in forest cover (plantation establishment, logging or bushfires) and construction of farm dams as being factors that could be taken into account. Whilst noting the potential effects of land use change and possible sources of spatial data that could be used to monitor changes over time, the Wyong Water Study does not advocate routine monitoring for purposes of distinguishing some of the other factors that might cause changes in the hydrologic response of catchments affected by mining. The Commission does not consider that monitoring of land use change is warranted within the area that will be directly impacted by the Wallara 2 Coal Project.

E.2 GROUNDWATER

The Wyong Water Study provides less information on groundwater than on surface water. The report7 provides:

The number and location of extraction and monitoring groundwater bores within the Wyong study area, within the proponent’s exploration lease and within the footprint of the proposed mine;

A summary of the number of measurements of “water levels” in monitoring bores, three such bores (outside the footprint of the proposed mine) being operated by NOW and the remaining 44 being sampled by the proponent;

A summary of available groundwater chemistry data, obtained mostly by the proponent in 19988.

An indication of the availability of survey data and bore construction data;

A summary of bore extraction data, across the Wyong study area9;

A summary of available aquifer test data.

The report does not provide raw data, nor any analysis (e.g. statistics) of the data.

E.2.1 Findings and Commentary

Of particular interest to the Commission are conclusions and recommendations in the Wyong Water Study and peer review relating to “sufficiency for assessing the potential impacts of the Wallarah 2 Coal Project”. The significance of these conclusions and recommendations is that a number of submissions in writing and at the public hearing held on 28 October 2010 focused on references to a need for groundwater data for either “a minimum of 2 years”, or “ideally ... for 2 years (including previous monitoring)”, such period being either “prior to any inseam development” or “prior to the commencement of mining activity that is likely to affect surface water or groundwater flows or quality”.

7 SKM (2010), Section 5. 8 See Mackie Environmental Research, 2009, Table C.1 and Fig. C.3. 9 See Mackie Environmental Research, 2009, Table B.1 for data about bores within 2 km of the proposed project area, and EA Table 8.2 for those bores within the footprint of the proposed mine.

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The fact that different phrases have been used in different places by SKM and Aqualinc has created an opportunity for differences in interpretation. E.2.2 Findings of the Wyong Water Study In their report, SKM10 stated that:

In the context of groundwater levels, “Additional groundwater monitoring within the coal seam needs to be obtained prior to any inseam development of the proposed mine… In terms of the ability of the available data to provide a control for changes due to natural variability, this information is required once the impacting activity occurs. Therefore, if regular monitoring of the current network of available groundwater bores is re-established prior to any inseam development, then this control information would be considered adequate… Regular groundwater level monitoring of these bores for a minimum of 2 years prior to any inseam development (to establish patterns of fluctuation across different climatic events) to the proposed impact, is essential to identify impacts subsequent to the mining activity.”

In the context of groundwater quality, “If regular groundwater quality monitoring of the current and proposed bore network is re-established prior to any inseam development, then this groundwater quality control information would be considered adequate… The primary data insufficiency relates to the information available to identify the impacts of the proposed change. It is recommended that regular groundwater quality monitoring of the current monitoring network (and the proposed coal seam formation bores recommended in Section 10.2) is required. Regular groundwater quality monitoring of these bores for a minimum of 2 years prior to any inseam development, is essential for the impacts on groundwater quality to be observed.”

In their conclusions “The baseline information in the study area is sufficient for the purposes of undertaking an assessment of the potential impacts of the Wallarah 2 Coal Project. This does not relate to a more detailed analysis and management of ongoing project-related impacts, which would be more properly assessed on an expanded baseline data set developed specifically for the purposes of project management.”

In their recommendations, “Regular water level monitoring is re-instituted for an agreed observation bore network across the study area. This should ideally operate for 2 years (including previous monitoring) prior to any inseam mine development, so that natural variability can be captured in the data.”

In their review of SKM’s report, Aqualinc11 recommended that: “All groundwater level, groundwater chemistry, stream flow, stream chemistry and climate sites that are used to determine baseline conditions should have at least two years of relevant data prior to the commencement of mining activity that is likely to affect surface water or groundwater flows or quality.”

10 SKM (2010), various pp. 11 Aqualinc (2010), p30

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NOW12 reviewed SKM’s Wyong Water Study and Aqualinc’s review, and stated that: “The assertion made within the SKM study and Aqualinc peer review that two years of baseline data is adequate to capture groundwater fluctuations and provide statistically significant correlation is questionable… In terms of assessing sensitivity of surface-ground water connectivity and groundwater baseflow contributions to Jilliby Jilliby Creek and tributaries, and maintaining flow into the Wyong River, this should have been examined more closely.” The Commission accepts that, “ideally”, two years of groundwater monitoring should be available before the commencement of “inseam mine development”. However, it is worthwhile considering how this additional data could or would be used. E.2.3 Interpretation and Implications Hydrological data can be collected at different locations, at different times in the project life cycle (from before feasibility studies to during operations to after closure), at different frequencies and for different purposes. It is always easy to suggest that more data are needed. At times, when a lot of data are available, it is possible to wish for fewer data. Neither SKM nor Aqualinc have attempted to explain how data of various kinds, if they were available now, would assist in assessing the potential impacts of the Wallarah 2 Coal Project. Based on the various conclusions quoted above, some stakeholders believe that:

Measurements of groundwater levels within the coal seam would have assisted in assessment of potential impacts of the project, perhaps improving the calibration of a regional groundwater flow model in pre-mining conditions, although this explanation is not provided;

At least 2 years of data would be required to allow identification of changes after commencement of mining.

Having considered available information (see Appendix G of this report), the Commission:

supports SKM’s conclusion that currently available data are sufficient for impact assessment and for development of an impact assessment model;

agrees with SKM’s conclusion that more data would be required for assessment and management of “ongoing project-related impacts”, once operations had commenced;

notes that seasonal variations of 2 to 3 m have been observed13 in water table elevation in alluvial aquifers and in monitoring bores drilled deep into hard rock during the period 1998-2001;

does not agree that two years of monitoring would be required before commencement of “inseam mine development”;

accepts that sufficient baseline data on piezometric heads in the coal seam could be obtained prior to arrival of shafts or the inclined drift tunnel at the coal seam approximately 350 m below the Buttonderry site in Year 1 of mining14, possibly 2 or more years after project approval, and that neither of these activities would be likely

12 NSW Office of Water, Letter dated 24 September 2010 from Mark Mignanelli to PAC 13 Mackie Environmental Research, Wallarah 2 Coal Project, Groundwater Management Studies, October 2009, Fig. C2 14 EA, Section 2.6.1

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to affect surface water or groundwater flows or quality, other than groundwater in the immediate vicinity of the coal seam.

It is important to understand what is meant by “groundwater levels” within a coal seam 350 m below the land surface. When a monitoring bore is constructed and allowed to equilibrate, groundwater will flow into the monitoring bore until it reaches an equilibrium level within the bore. The level to which the water rises provides a measure of piezometric head15. In the flow system under consideration, piezometric head within the coal seam is almost certain to be between the elevation of the water table in the hills (say 185 mAHD16) and sea level (0 mAHD). The level will vary, in response to variations nearer to the land surface. Some variations, especially in deep holes, are caused by changes in atmospheric conditions (as weather systems pass by) and by earth tides. The average head at any location in a deep coal seam is unlikely to already be showing a long term trend because, in the absence of mining, there are no regional scale stresses (hydraulic gradients) to which groundwater in the coal seam would be responding. Piezometric heads are likely to be relatively steady. A useful indication of head could be obtained within weeks or months of the construction of any new borehole, and certainly within 6-12 months. Knowing piezometric head prior to mining would certainly allow computation of the decline in head that would inevitably occur once mining commenced. However the change would be so great that there would be no possibility of not seeing the change. Mining at an elevation of -350 mAHD, for example, would cause piezometric head at that location to drop to -350 mAHD. If the head prior to mining were +50 mAHD, the change in head would be 400 m. There is no reason to suggest that 2 years of monitoring data prior to mining would make it easier to detect a change of 400 m. It might be argued that additional measurements prior to mining would improve the accuracy of groundwater modelling. It is true that the calibration of a model may be influenced by knowledge of heads at depth. However calibration of any model in a steady state situation is difficult, because of the inter-relationship between estimates of hydraulic conductivity and recharge, and in the absence of robust methods for estimation of recharge independently of groundwater flow modelling The hydrogeological system is currently in quasi-equilibrium with the climate, and there is no reason to expect that climatic variations within a two-year period would lead to significant transients. Additional measurements of piezometric heads in lower Formations, or in the Wallarah / Great Northern seam itself, could in principle lead to a change in estimates of hydraulic conductivities in different units, but since recharge at the land surface is not known, there is no guarantee that additional measurements would significantly increase the degree of confidence in the calibration. It is already difficult to take into account all observations in any calibration, cf. the goodness of fit presented by Mackie Environmental Research16.

15 Piezometric head in a deep borehole is the sum of the elevation at the base of the borehole and the height of the water column within the bore. The height to which the water rises is a measure of pressure at the base of the hole, or in some circumstances a weighted average of pressures at a number of locations along the height of the borehole, if the borehole passes through several permeable aquifers. If the fluid within the borehole is more dense than fresh water, the final level will be lower, but the pressure at the base will be unchanged. It is therefore important to know the quality and density of water in the water column. 16 Mackie Environmental Research, Figure E7

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NOW identifies surface water – groundwater interaction near streams as one issue that requires special attention, but neither SKM nor Aqualinc distinguish between different questions that may need to be answered, the different types of monitoring that may be needed, and most importantly how monitoring data might be analysed or used in modelling to aid the process of understanding observed changes and predicting further changes. Additional measurements of “groundwater levels” in alluvial aquifers would be useful. In this context, the level referred to is the elevation of the water table, measured in shallow boreholes screened within the alluvium. Water table elevations fluctuate seasonally and in response to rainfall-runoff events. In order to understand the processes of stream-aquifer interaction, it would be useful to measure water table elevations and in stream surface water elevations in pairs of locations or along transects over a number of years. It is important to note that the impact of the proposed mining on alluvial aquifers near Jilliby Jilliby Creek would not occur until the end of LW 5N, approximately 3 to 5 years after the start of longwall mining. E.4 REFERENCES Alkhatib, M and Merrick, NP (2006),

Groundwater Simulation and Optimisation Modelling of the Kulnura – Mangrove Mountain Aquifer Systems, Final Report for Gosford-Wyong Councils Water Authority, Research Report NCGM 2006/14, November 2006

Aqualinc, 2010

Wyong Water Study: International Peer Review. Report prepared for the NSW Department of Planning. Aqualinc Research Ltd. August 2010.

DoP, 2008

Impacts of Potential Underground Coal Mining in the Wyong Local Government Area. Strategic Review. NSW Department of Planning. 2008.

Gosford Wyong Council’s Water Authority, 2007

WaterPlan 2050: Options Report for the Long Term Water Supply Strategy, GWCWA, July 2007

Gosford City Council and Wyong Shire Council, 2007

WaterPlan 2050 adopted by Gosford City Council and Wyong Shire Council, July/August 2007

Mackie Environmental Research, 2009,

Groundwater Assessment, Appendix B to the Environmental Assessment for the Wallarah 2 Coal Project

NSW Office of Water, Letter dated 24 September 2010 from Mark Mignanelli to the Commission

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SKM, (2010) Wyong Water Study. Report prepared for the NSW Department of Planning. Sinclair Knight Metz. August 2010.

SKM and CSIRO Methods for Estimating Groundwater Discharge to Streams – Summary of Field Trials. Draft V1. Report prepared by for the National Water Commission, July 2010 (quoted by SKM – not sighted)

APPENDIX F

SUMMARY OF PRINCIPLES OF SUBSIDENCE

Subsurface Behaviour Figure F.1 shows a conceptual model of rock mass behaviour above a mining excavation. As excavation width, W, increases, four zones progressively develop, namely1:

A caved zone comprising bulked material with a high void content that has fallen out of the roof (goaf);

A fractured zone comprising material that has a high concentration of connected vertical and horizontal fractures and therefore is highly permeable;

A constrained zone comprising irregular and disconnected vertical and horizontal fractures. In the absence of major geological discontinuities such as faults and dykes, water inflow to mine workings through this constrained zone is determined by the natural permeability of the rock mass within it.

A surface zone comprising vertical fracturing and horizontal shear that extends a limited depth into the ground. This may promote connection to strata that has a higher or lower permeability. If the deeper strata are more permeable then alternate groundwater flow systems may develop in those strata. If the deeper strata are less permeable then the flow systems are likely to remain unchanged.

Figure F.1: Conceptual Model of Caving and the Nature of Fracturing and Surface Profile above a Mine Excavation

1 This model is sometimes presented as comprising three zones, with the caved and the fractured zone combined as one zone.

In a multiple excavation situation, such as for the Wallarah 2 proposal, excavated panels are separated by pillars of insitu coal referred to as interpanel pillar or chain pillars. When the span of the excavations is small, the overburden above the excavations bridges from one interpanel pillar to the next. As the span of the excavations is increased and caving develops, some of the weight of the undermined overburden is carried by the caved material. However, because caving does not develop along a vertical plane but rather along a plane angled out over the goaf (shown in blue in Figure F.1), some portion of the weight of undermined strata is always carried by the interpanel pillars. Conventional Surface Behaviour Conventional surface subsidence results from a combination of sag of the roof strata into each excavation and compression of the interpanel pillars and surrounding strata. The amount of subsidence due to the sag of the undermined overburden increases with increase in excavation span, W, (up to a limiting value) and decreases as depth of mining, H, increases. That is, subsidence increases as W/H ratio increases, until a limiting value is reach. It also increases with increase in mining height, h. The amount of subsidence due to compression of the strata between excavations is determined by the width of the interpanel pillars, w, the height of the interpanel pillars and the nature of the roof and floor strata in the near vicinity of the coal pillar. These are all variables in the mine layout for Wallarah 2 and as the EA correctly describes, this is a complex interaction2. In flat topography, the subsurface deformation of the rock mass results in the surface usually subsiding in the form of a trough, taking on a saucer shaped appearance, Figure F.1. Trough subsidence is referred to as conventional subsidence and has the following components:

Angle of draw, which defines the limits of the subsidence trough;

Curvature, which defines the degree of outwards (convex/hogging) or inwards (concave/sagging) bending of the surface of the subsidence trough;

Vertical displacement of surface points;

Horizontal displacement (in two dimensions) of surface points;

Tilt, or slope, induced by differential vertical displacement between adjacent points;

Strain (tensile or compressive), induced by differential horizontal displacement due to stretching (hogging) or compression (sagging) of the surface.

At relatively shallow depth, displacement may occur at a point above an excavation within a few months of it being undermined. However, as depth of mining increases, roof sag above an extracted panel and compression of the pillar system can increase each time a subsequent mining panel is extracted. This gives rise to additional vertical displacement, referred to as incremental vertical displacement which in turn, generates incremental tilt and incremental strain. This is the type of behaviour that has been predicted over the Wallarah 2 Study Area.3

2 EA, Appendix A1, p2. 3 Illustrated in Figure 6.8 to Figure 6.11 of the EA for the Wallarah 2 proposal.

As with all subsidence prediction techniques, the poorest correlations between measured and predicted conventional ground movements derived from the hybrid model relate to strain. The EA discusses some of the reasons for this behaviour4 and attempts to address it in two ways, namely by:

Providing plots of strain distributions sourced from nearby longwall mines where the regional geology is closest to that of the Wallarah 2 Study Area. These are intended to ‘illustrate’ the range of strain distributions that might be experienced in the Study Area5.

Using curvature (rather than strain) as the primary impact prediction parameter.

The Commission considers both of these approaches to be relevant and insightful. However, the use of curvature instead of strain limited the Commission’s capacity to conceptualise and assess the significance of the subsidence movements and to draw comparisons with information in the public domain. With the exception of houses for which the EA provides recent research findings that correlate curvature with structural impact, the Commission had few points of reference for assessing impacts associated with curvature. Accordingly, the Commission requested the proponent to retabulate all curvature predictions in terms of strain. The strains presented in the EA and the additional strains provided at the Commission’s request were calculated by multiplying maximum curvatures by a factor of 15. This compares to a factor of 10 often applied in the Newcastle Coalfield and a factor of 12 used when comparing numerical modelling outcomes with empirical predictions. As such, the EA has adopted a conservative approach to strain prediction. However, the EA refers to strains calculated by this approach as average strains6, which the Commission considers a misnomer and liable to confuse because the term average does not have the meaning ascribed to it in statistical analysis and everyday usage7. This matter is discussed in more detail in the PAC report for the Bulli Seam Operations proposal (DoP, 2010), published after the finalisation of the Wallarah 2 EA. The Commission notes that in the proponent’s responses to its questions, ‘average predicted’ strain is now referred to as ‘maximum predicted’ strain.8 The two approaches to strain prediction noted above circumvent the issue of the curvature calibration factor. However, neither offers a complete solution. The first is limited by the fact that the geological setting, mine design philosophy (Wallarah 2 chain pillars are designed to ‘yield’) and mining parameters (depth, mining height and panel width combinations) associated with the Wallarah 2 proposal are different to those of nearby operations. Hence, strain magnitudes and distributions may also be different over the Study Area. The second approach is constrained by the fact that there is a limited data base available for correlating curvature with subsidence impacts, with impact assessment in the past being based primarily on vertical displacement, tilt and strain parameters. One of the first approaches to basing impact assessment primarily on curvature instead of strain is that arising out of research undertaken by Mine Subsidence Engineering Consultants on the impacts to housing undermined by longwall panels at Tahmoor in the Southern Coalfield (ACARP 2009). As

4 EA, Appendix A2, p45. 5 WACJV (2010a), response to PAC Question 1.5. 6 EA, Appendix A2, p45. 7 This meaning being a measure that represents the ‘middle’ of the range of a data set 8 WACJV (2010a), Supplement to Report No. MSEC248 – Predicted Conventional Strains.

noted by DII in respect to impact assessment on residential structures (DII, 2010), this method is yet to be tested. In response to its questions, the proponent advised the Commission that:

The first five longwalls to be extracted are 125 / 155 metres wide which are narrower than the subsequent longwalls which are 175 metres to 255 metres wide. The predicted mine subsidence parameters for the natural features and items of surface infrastructure located above the first five longwalls are similar levels to those typically experienced in the Southern Coalfield. ......... The predicted mine subsidence movements for the remaining longwalls are similar to those experienced elsewhere in the Hunter and Newcastle Coalfields where there is reasonable depths of cover, say greater than 200 metres. This previous longwall mining experience can be used as a guide to the expected levels of impact and to establish the management strategies for these features.9

These conclusions have been relied upon to some considerable degree in the EA when assessing subsidence impacts. Hence, it is important that they are validated early in the mining process should the W2CP be approved. The EA notes a number of features of the prediction methodology which suggest that the predictions are conservative, that is, over-estimated10. Whilst this would normally be a favourable outcome, it may not be in the case of Wallarah 2 proposal if the interpanel pillars do not yield as designed on the basis of the numerical modelling. Should these pillars not yield, vertical displacement over the pillars is likely to be less, resulting in a more irregular (or ‘wavy’) final surface profile. This, in turn, could result in larger final tilts and strains, albeit that vertical displacement is less. Hence, the Commission concurs with the submission of DII (2010) that:

Whilst the results of subsidence prediction may be used as a guide to the development of relevant management measures, I&I NSW MR specifically note the inherent uncertainty in predictions that can only be addressed by obtaining site specific data during mining.11

Non-conventional Surface Behaviour Non-conventional surface subsidence refers to situations where subsidence behaviour is dominated by site specific conditions. Three conditions of particular relevance to the Wallarah 2 proposal are steep topography, valleys and gorges, and geological structures. Far field horizontal displacements are usually listed as a fourth condition but Appendix A2 states that:

9 WACJV (2010a), response to PAC Question 1.10. 10 Reference, for example, WACJV (2010a), response to PAC Question 1.4. 11 The NSW Department of Industry and Innovation (DII) encapsulates the Minerals Resources Division (I&I NSW MR) which, in turn, includes the Subsidence Engineering Division.

The confidence levels in these predictions continue to improve and, for this reason, this report considers far-field horizontal movements to be conventional movements, rather than irregular or anomalous non-conventional movements.12

In steep topography, gravity can result in high levels of ground movement in a downhill direction, causing tensile strain to accumulate towards the top of hill sides, where it can result in one or more wide open surface cracks. Undermining of deep incised valleys and gorges, such as in the Southern Coalfield of NSW, can result in:

Valley closure whereby the two sides of a valley move horizontally towards the valley centreline.

Uplift of the valley floor due to valley closure, which can cause buckling and shearing of the valley floor and near surface strata. The difference between the amount of vertical displacement that could have been anticipated in the absence of a valley and that which eventuates is referred to as upsidence.

Buckling and shear in the near-surface strata can generate an extensive network of fractures and voids in the valley floor which can act as conduits for sub-surface flow and therefore impact on surface flow. Ground movements due to conventional subsidence may also contribute to this network if the upsidence occurs within the angle of draw of the mine workings. The phenomena of valley closure, upsidence, and far field horizontal movements have only come to be recognised in the last 15 to 20 years as a result of ground behaviour observations in the Southern Coalfield of NSW. They are known to occur in escarpment and mountainous areas in the Western Coalfield but have been of less concern in the Newcastle Coalfield to date. This might reflect to some degree the different topography in this coalfield, in particular, the absence of deeply incised valleys and gorges in a plateau setting. Predictions of upsidence and closure in the EA rely on a methodology developed from research some eight years ago.13 The methodology is based predominantly upon the measured data from Tower Colliery in the Southern Coalfield, where in-situ stresses are notably high and the topography includes steep, deep gorges.14 The EA reports that the level of confidence in the prediction methodology is not as high as that associated with the prediction of conventional subsidence but that it can be used ‘so long as sensible factors of safety are applied’15. Figure F.2 shows recent comparisons between measured incremental closure and incremental upsidence and those predicted by the methodology16. The wide scatter in outcomes and conservative nature of predictions is readily apparent, with the prediction methodology reported to have over-predicted valley related movements in more than 95% of cases.17

12 EA, Appendix A2, p39. 13 Waddington and Kay (2002). 14 EA, Appendix A2, p46. 15 EA, Appendix A2, p46. 16 Reproduced from Appendix A of the EA for Bulli Seam Operations, Illawarra Coal Pty Ltd. 17 EA for Bulli Seam Operations.

Figure F.2: Plots Showing Comparisons between Predicted (Horizontal Axis) and Measured

(Vertical Axis) Closure and Upsidence Based on EA Prediction Methodology18 In relying on this prediction methodology developed for the Southern Coalfield, the EA and associated documentation make note of important differences between the geomorphology of the Southern Coalfield and that associated with the Wallarah 2 Study Area, including:

The ridges in the forested areas of the Study Area are jointed and stress relieved.19

The upland streams in the Study Area are contained within V-shaped gullies separated by unconfined ridges, in contrast to the Southern Coalfield streams which are contained in more U-shaped gorges cut into a plateau.20

The valleys in the Study Area are not only much broader than the gorges of the Southern Coalfield but are filled with some 20-30 m of alluvium.21

Rock bars and associated pools typical of the Southern Coalfield do not exist in the upland streams in the proposed Wallarah 2 mine area.22

Streams in the alluvial filled wide valley floors above the proposed longwalls have water levels that are generally above the surrounding groundwater levels and the water levels in these streams are not controlled by a series of exposed rock bars.23

Connective Cracking A number of submissions questioned the accuracy of the hydrogeological properties and predictions for the constrained zone24. To assist its assessment, the Commission undertook a review of dimensions associated with NSW mines that have extracted longwall panels successfully beneath water bodies in the Sydney Basin and beneath alluvial valleys in the

18 Reproduced from Appendix A of the EA for Bulli Seam Operations. 19 EA, p4-57 and WACJV (2010c), p6. 20 WACJV (2010c), p6. 21 EA, p4-57. 22 WACJV (2010c), p6. 23 EA, Appendix A2, p65. 24 For example, the PSM Report that accompanies the submission of Wyong Shire Council.

vicinity of the Wallarah 2 Study Area, Table F.1. The two most critical controlling factors are mining height and panel width to depth ratio, W/H. Whilst direct comparisons cannot be made because of the different geological and geotechnical settings of the various case studies, the comparison indicates that the mining dimensions associated of the Wallarah 2 proposal are at the conservative end of past mining experiences. One of the mines involved in this review was Mandalong Colliery, which operates longwall panels of similar mining height and panel width beneath the Mandalong Valley (immediately to the north of the W2CP exploration leases) to that proposed beneath the Dooralong Valley. Another was South Bulli Colliery in the Southern Coalfield, where research concluded that higher than 185 m above the seam (equivalent to 1.7 times panel width), there was no evidence of any change in the hydraulic conductivity of water from the Cataract Reservoir to the mine workings (Byrnes, 1999). The Commission concludes that the mining dimensions proposed by the proponent for mining beneath the Dooralong Valley are not inconsistent with those which have been utilised successfully to avoid direct hydraulic connections to the surface at other mining operations. Table F.1: Panel Width to Depth Ratios Associated with NSW Longwall Mines Working

Beneath Water Bodies and Alluvial Valleys

Longwall

Panel Number

Mining Height h

(m)

Pillar Width w (m)

Void Width W (m)

Depth H (m)

W/H

John Darling Colliery

Beneath Pacific Ocean

1 (BH Seam)

~86 ~215 ~0.4

4 (BH Seam)

~128 ~220 ~0.58

5 (BH Seam)

~115 ~200 ~0.58

3 (VT Seam)

~128 ~150 ~0.85

South Bulli Colliery

Beneath Cataract Water

Reservoir

501 - 508 2.7 66 111 to 120

305 to 320

0.29 to 0.34 508 - 510 2.7 60

512 & 513 2.7 60 150 325 ~0.46

Wyee Colliery (Mannering)

Beneath Lake

Macquarie 17 to 19 3.2 45 130

150 to 160* 0.81 to 0.86

Mandalong Mine

Beneath Mandalong Valley and

adjacent hills

1 to 4 ~3.3 –

4.8 41 125

160 to 350

0.36 to 0.78

5 to 8 3.4 – 4.8 45 160 190 to

360 0.44 to 0.84

Wallarah 2 Mine

Beneath Dooralong Valley and

adjacent hills

1N 3.5 to

4.5 65 125

345 to 485** 0.26 to 0.36

LW 2N to LW 5N

3.5 to 4.5

65 155 345 to 485** 0.32 to 0.45

LW 6N to LW 11N

4.5 65 175 345 to 465** 0.38 to 0.51

* Solid Rock – that is, unweathered rock, excluding sediment thickness and water depth ** Total depth, not solid rock cover

Geological Structures The Wyong Strategic Review qualified its findings in respect of connective cracking between the surface and the mine workings with the words ‘In the absence of major, unforeseen geological anomalies (eg faults and dykes)’.25 The NSW Office of Water added a similar qualifier, stating:

Although the risk of subsidence-induced interconnectivity between alluvial groundwater systems and the mine workings may be regarded as minimal, redirection of alluvial groundwaters either to basal tensile fracture networks, and/or re-activation of regional geological structures remains a risk, against which NOW has insufficient evidence to determine minimal harm will occur under various coal operation scenarios.26

In its report that accompanies the submission by Wyong Shire Council (WSC), PSM identified that:

…. it is unlikely, but not impossible that there are other undetected geological structures within the study area. These structures can cause surface bumps to occur. They can potentially also provide flow paths for water and gas.27

The proponent has undertaken an extensive exploration program using a range of modern geophysical technologies to determine the geology of its exploration leases and, as Figure 2.2 shows, has laid out the mine workings to avoid the geological features identified from this process. Nevertheless, as acknowledged in the EA, not all geological disturbances may have been identified. There are limitations associated with geophysical techniques as to the size of geological discontinuities that they can detect. The presence of thick alluvium also impedes the effectiveness of some techniques. Many geological features are not continuous between the surface and the seam. Many also dip from the vertical and so their location underground may not coincide with their location on the surface if they are continuous. PSM went on to note that the groundwater modelling undertaken by Mackie Environmental Research (MER) was based on the assumption that:

…. there will be no significant joints, faults or other defects in the rock mass that transmit water naturally.28

In its response to submissions, the proponent acknowledged that this was the situation, referring also to the lack of inclusion of geological structures in the underpinning subsidence modelling.29 In their submissions, both DECCW and the Australian Coal Alliance have raised the presence of faulting as reported by Northern Geoscience (NG, 2005) in a (draft) report prepared for the Australian Gas Alliance (the forerunner to the Australian Coal Alliance). DECCW has submitted that:

25 DoP (2008a), p1. 26 NOW (2010), p2. 27 WSC (2010), PSM report attachment, p14. 28 WSC (2010), PSM report attachment, p23. 29 WACJV (2010b), p5-28 & 5-29.

The geology is generally well described in the EA and MSEC (2010) stated that “there are no major geological structures identified at seam level within the project area”. Discussions of geological fault zones at the surface, however, were difficult to find in the EA. It is therefore of concern that Northern Geoscience (2005) state:

A major geological feature of the Jilliby Creek is that it follows a fault zone approximately 1.3km west of Mount Alison……Midway along this feature, Little Jilliby Creek converges into Jilliby Creek and is interpreted as a conjugate fault zone which the Little Jilliby Creek has incised. The significance of the feature is that it provides a significant transient pathway to groundwater movement and discharge into the surface stream flow regime.30.

The Commission identified a similar concern in its questions of the proponent re the focus on the EA on geological structure ‘at seam level’.31 In its first response to submissions, the proponent contested the unsubstantiated nature of Northern Geoscience’s conclusions32 and produced a plan showing in more detail the outcomes of the proponent’s exploration program. This plan appeared to suggest, in fact, that faulting had been detected in some boreholes within the Wallarah 2 Study Area, including two boreholes on the alignment of Little Jilliby Jilliby Creek, in the vicinity of the fault line predicted by Northern Geoscience, Figure F.3. The Commission noted that the direction of this fault line was not inconsistent with the direction of recorded faulting in the region.33 The proponent subsequently advised that:

In an attempt to identify EVERY possible occurrence of potential “faulting” intersected in exploration boreholes W2CP recorded EVERY zone containing slickensided surface34 (however small) and marked the holes as “FAULTED”.35

The proponent included photographs of bore core features for the three possible faults recorded in the vicinity of Jilliby Jilliby Creek and Little Jilliby Jilliby Creek. These display attributes consistent with there being considerable doubt as to whether they constitute faults. This doubt is also a reflection that if they do exist, they are unlikely to constitute major features. Collectively, the proponent has provided what the Commission considers a reasonably compelling case for the absence of faulting orientated along Jilliby Jilliby Creek and Little Jilliby Creek.36

30 DECCW (2010a), p4. 31 PAC Question 1.14 to WACJV. 32 WACJV (2010b), 5-32 to 5-39. 33 WACJV (2010b), Figure 25, p5-37. 34 A smooth or polished surface, often striated, that is consistent with sliding having occurred along the surface. 35 WACJV (2010f). 36 WACJV (2010f).

Figure F.3: Location of Seismic Lines and Interpreted Structures across Jilliby Creek37 A number of opportunities are still available to detect geological features well in advance of longwall mining. These include:

In-fill exploration drilling

In-seam longhole drilling for up to more than one kilometre ahead of mining.

Exposure of features during the development of main roadways and longwall gateroads.

Management of Effects and Impacts Consistent with risk management principles, there are three options for dealing with risk associated with subsidence impacts, namely:

Eliminate

Mitigate

Tolerate

Adaptive management and remediation can find application across all three options. Adaptive management is concerned with monitoring subsidence effects and impacts and, based on these outcomes, modifying the mining plan as mining proceeds so as to maintain effects, impacts and/or consequences within predicted or designated ranges38. This can involve actions such as reducing the extent of mining within a panel, altering mining height, or changing the dimensions of subsequent panels and interpanel pillars based on early

37 WACJV (2010b), Figure 24, p5-35. 38 See also Newcastle and Hunter Valley Speleological Society Inc v. Upper Hunter Shire Council and Stoneco Pty Limited [2010] NSW LEC 48. - Adaptive management is......... an iterative approach involving explicit testing of the achievement of defined goals. Through feedback to the management process, the management procedures are changed in steps until monitoring shows that the desired outcome is obtained.

warning signs of deviation from planned outcomes. It is important to appreciate that a change in longwall panel width and/or interpanel pillar width usually requires a lead time of at least two to three years. Remediation refers to the activities associated with partially or fully repairing or rehabilitating impacts and, as such, is a recovery measure for limiting the consequences of an impact. Elimination of subsidence impacts is achieved by not mining within a zone of influence of the feature to be protected. This zone is usually defined by an angle of draw that is based on achieving zero vertical displacement beneath the structure. Greater certainty against impacts can be achieved by incorporating a buffer zone around the feature and measuring the angle of draw from the outer boundary of this buffer zone. For example, in the case of a dam wall, Justice Reynolds recommended that no mining be permitted within a zone defined by a 35º angle of draw taken from a line on the surface 200 m from the edge of the structure. Mitigation involves measures undertaken to reduce the impacts of subsidence on features. Six common means are:

Restriction of ground movement, which may be achieved in one of two ways:

i. Selecting mining dimensions so as to increase the width of pillars between panels, and/or restrict mining height and/or excavation width and/or the distance that mining can approach within a feature.

ii. Partial or total backfilling of mine voids and bedding plane partings.

Isolating a feature from ground movement: Techniques include placing bearings beneath structures (such as bridges), uncovering buried structures (such as pipelines), and constructing slots in the ground at strategic locations adjacent to a feature to encourage ground movements to concentrate at the slots.

Rigid ‘floating’ foundations: By placing a structure on a rigid raft foundation that can ‘slip’ on the ground surface, the structure can move as one entity and so be protected from curvature and horizontal strain. However, it is still susceptible to tilt. This technique is often applied to houses in mining areas.

Flexible construction: Structures may be designed such that they can sustain a degree of differential movement whilst remaining safe, serviceable and repairable39. For example, weather board structures generally have a higher tolerance to tensile strain than masonry structures, whilst the tolerance of masonry structures to differential movements can be increased through the use of strategically located expansion and contraction joints.

Maintenance responses: This involves measures which aim to maintain the physical state and function of a feature, albeit that it may be impacted by subsidence during the mining process. Examples include increasing flow volume in a fractured section of a watercourse in order to maintain surface flow at pre-mining levels, installing support

39 Safe means no danger to users; Serviceable means available for its intended use; Repairable means damaged components can be repaired economically. (DoP, 2009b).

in overhangs and cliff faces prior to undermining, and periodically relevelling and realigning man-made structures.

Preservation responses: Objects and structures at risk from mine subsidence may be removed on a temporary or permanent basis prior to undermining, or logged and recorded in a visual format for posterity.

Toleration of subsidence impacts usually requires that no action be taken to control or remediate the impacts. This practice is common in very deep mines (because subsidence effects are restricted and dissipate gradually over a large area) and at locations that have no significant sub-surface and surface features. There is a variety of remediation options available to respond to subsidence impacts. Remediation of the built environment usually involves re-levelling and restoring surface finishes, although reconstruction is sometimes undertaken. In the case of natural features, options include backfilling and/or grouting of cracks and fracture networks, stabilisation of slopes, and implementation of drainage and erosion control measures. Fractures may also infill naturally in watercourses that have a moderate to high sediment load; otherwise they may have to be grouted. In the case of watercourses, it is not yet feasible to remediate an entire upsidence fracture network. The degree of success of grouting is dependent on the accessibility of the site, on the type of grouting materials used and on timing. If the site of fracturing is affected by a number of mining panels, several episodes of grouting may be required over a number of years. In the interim, mitigation measures are required to sustain surface water flows if the local ecology is not to be impacted. The proponent has committed to adaptive management, stating that:

Even though a conservative approach has been adopted for the mine subsidence predictions and impact assessment methodology, WACJV has committed itself to an adaptive and continuous improvement approach to the longwall panel design whereby the mining dimensions and limits of future mine workings will be continuously reviewed and modified as necessary as experience is gained to ensure the required subsidence parameters are observed at houses in the Hue Hue Subsidence District and within the Dooralong and Yarramalong Valley flood plains.40

DII (2010) has adopted a broader approach to adaptive management to include relocating or re-routing some infrastructure, stating in its submission:

To overcome the difficulties associated with the prediction uncertainty, it is important that the proponent be required to develop and implement an on-going robust process to ensure “adaptive management” should subsidence deviate from predictions. The term “adaptive management” in this context [subsidence prediction] refers specifically to major strategic management measures such as changes to mine layout and relocation or re-routing of certain features, etc, which must be implemented in response to monitoring data in a timely manner.

40 EA, Appendix A2, piii.

The Wallarah 2 mine layout permits longwall panel length, longwall panel width, mining height and interpanel pillar width can be varied throughout the life of the operation, although a change in longwall panel width and/or interpanel pillar width usually requires a lead time of two to three years. Mining height is the easiest and quickest parameter to change and can be quite effective given that numerical modelling has indicated that vertical displacement at the surface changes in direct proportion to mining height. However, it needs to be appreciated that the application of this adaptive management technique may be constrained by the design of the longwall mining equipment, particularly the minimum height in which it can be operated. Therefore, this factor needs careful consideration when developing equipment specifications. A specific issue arises with respect to validating the subsidence predictions from the start of the project if it goes ahead. Because subsidence develops incrementally, the various conventional subsidence parameters may not approach their limiting (final) value at a point until after the next one or two longwall panels have been extracted. The Commission notes that the first three longwall panels proposed to be extracted extend beneath the Hue Hue Mine Subsidence District. Hence, the need for any adaptive management measures may not become apparent in time to fully benefit properties undermined by the first one or two longwall panels in this area. This is a matter for consideration when developing and approving any Extraction Plans.

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APPENDIX G: GROUNDWATER

If the proposed project proceeds:

mining will cause subsidence,

mining and subsidence will cause changes in groundwater flow patterns and rates, and

changes in groundwater flow patterns and rates may affect streamflow and stream ecosystems.

The impact of subsidence on the structure and hydraulic properties of the ground and hence on groundwater flow is of great interest to stakeholders. Changes will occur. The key questions relate to the magnitude and significance of these changes, which can only be predicted by computer simulation modelling. Groundwater flow and modelling are discussed here in general terms, followed by discussion of how modelling can be reviewed and assessed. While considering and assessing the project, the Commission has been regularly reminded that others had hoped that the groundwater modelling undertaken by the proponent might be assessed by independent experts. This report reviews and assesses the proponent’s groundwater flow modelling.

G.1 FUNDAMENTALS OF GROUNDWATER FLOW

G.1.1 The role of groundwater in the hydrological cycle

Everyone has some understanding of rainfall, evaporation and streamflow, because these hydrological processes are seen and experienced in daily life. When rain falls to the land surface, some water evaporates almost immediately, some flows across the land surface towards streams and rivers as “surface runoff”, and some infiltrates into the soil and evaporates or transpires (is taken up by plants) soon afterwards. Groundwater is more difficult to understand and its behaviour is more difficult to visualise. Groundwater is water found in pores and fractures within soil and rock beneath the land surface. The “water table” is the level below which pores and fractures are saturated with water and above which the pores and fractures are dry or partially saturated. Groundwater flows within and between interconnected pores and fractures. It flows very slowly because the resistance to flow is large and the driving force is generally small. Groundwater is often considered to be a subsurface reservoir that acts to regulate the hydrological system. Because groundwater moves slowly, rapid changes in groundwater storage rarely occur. Some of the rainfall that infiltrates into the ground seeps downwards, through the unsaturated zone, in a process known as “percolation”. When it reaches the water table it is known as “recharge”. Groundwater flows slowly from areas where recharge occurs towards lower parts of the landscape, discharging to streams, rivers or sometimes the ocean. In order to reach surface water systems, groundwater may initially flow downwards to depths far below the land surface and then rise towards the land surface. Although upward flow may seem counter-intuitive, groundwater always flows “downhill” from higher areas towards a lower energy state, in much the same way that water flows in a garden hose, when the nozzle is held higher than the hose on the ground. A major difference is that the travel time of an idealised

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“particle” of groundwater from source to sink can be hundreds, thousands or tens of thousands of years, depending on the distance from source to sink and the nature of geological materials along the travel path. In many hydrological systems, the volume of groundwater flow is almost insignificant relative to the volume of water that flows as surface runoff following rainfall, and especially relative to flood events. On the other hand, the contribution of groundwater to baseflow in streams can be significant during long periods between rainfall events. “Baseflow” in some systems is derived almost entirely from shallow groundwater. Contributions to surface water supply storages are often dominated by a small number of large streamflow events each year. Baseflow contributes to the support of ecosystems along the length of streams. If baseflow stops, as it does in streams that cease to flow for some months of the year, stream ecosystems can be supported by groundwater, even though groundwater itself may not appear to flow into the stream itself. In such cases, it is the groundwater in the shallow alluvial aquifers within which the streambed is incised, that supports the ecosystem. It is the fact that the pores and fractures beneath the water table are “full” of water that is important, even if the elevation of the water table falls between intermittent runoff and recharge events.

G.1.2 Controls on rates of groundwater flow

Rates of groundwater flow depend on the nature of the material through which groundwater is flowing, and on the driving force. At the simplest level of detail, the rate of flow of groundwater (in m3 or kL per day) is equal to the product of:

“hydraulic conductivity" (sometimes called “permeability”), which is a property of the medium (measured in metres per day, or m/d),

the cross-sectional area through which flow occurs (m2), and

hydraulic gradient, which is the slope of the driving force (dimensionless).

The driving force depends on a quantity known as “piezometric head” which is a combination of elevation and water pressure (expressed in metres of water at the ambient density). At the water table, air pressure is atmospheric (i.e. zero relative to gauge pressure), so head is equal to water table elevation, and the water table elevation itself is a measure of the driving force. Hydraulic gradient at the water table is equal to the slope of the water table. Pressure increases with depth below the water table, but it does not increase linearly with depth, as in a pond or swimming pool where the surface is horizontal and the water is stagnant (“hydrostatic”). Prediction of rates of groundwater flow in real physical systems requires the use of computer simulation models that take account of the nature of the ground in three dimensions to calculate the spatial and temporal distribution of piezometric heads, gradients and flows. Since the gradients depend on land surface and other elevations, a good representation of three-dimensional geometry is necessary for accurate predictions to be made. Land surface

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elevations in uplands and lowlands influence the “boundary conditions” and define the overall driving force.

G.1.3 Groundwater flow patterns prior to longwall mining

Under natural conditions, groundwater moves from uplands to lowlands, following the overall path of least resistance. Groundwater always seeks to flow from source to sink via the easiest possible route. If hydraulic conductivities were equal at all locations (“homogeneous”) and in all directions (“isotropic”), the easiest route would be the shortest route. But not all of the flow can take the same shortest route, so the overall flow spreads out, following paths with a wide range of “travel times”. If hydraulic conductivity is larger in specific layers, e.g. in a coal seam, then that layer acts as a conduit for groundwater, and is known as an “aquifer”. Adjacent units of “interburden” with lower hydraulic conductivity are known as “aquitards”. In layered sequences of aquifers and aquitards, the easiest path for groundwater to take from source to sink is via the aquifers, via the more conductive (less resistive) materials, but only if the water can reach the aquifers without passing across layers of very low hydraulic conductivity. Even a single low permeability aquitard can limit the transmission of water to the aquifers, thereby reducing the total flow through the system. In regional groundwater flow systems, groundwater tends to flow almost horizontally within the sub-horizontal aquifers and almost vertically across the aquitards between aquifers. Vertical hydraulic conductivity in aquitards can be much smaller than horizontal hydraulic conductivity in aquifers. The “anisotropy ratio” (the ratio of horizontal to vertical hydraulic conductivity) within aquifers and aquitards, and averaged over a sequence of both, can be 1000, 10000 or more. Even if coal seams have the capacity to allow flow, the adjacent layers can be almost impermeable.

G.1.4 Potential impacts of longwall mining on groundwater flow

The impact of mining on groundwater needs to be considered from three points of view:

From an operational point of view, mining companies need to pump out the groundwater than seeps into mines, to ensure safe working conditions for workers and mining equipment. Working conditions can not be excessively wet, and some drainage of water from the roof, walls and floor of underground workings is desirable because it improves geotechnical stability. Mining companies need accurate estimates of groundwater inflows in order to design water management infrastructure such as pumps, pipes, ponds and water treatment works.

From an environmental point of view, during and shortly after mining, stakeholders are concerned about the potential for leakage of groundwater from streams and their connected alluvium towards the mined areas, at rates that may have an unacceptable impact on streamflow and surface water supplies, or on ecological conditions nearby.

From a longer term point of view, indeed long after mine closure, stakeholders are keen to understand the time that it may take for the hydrological system to recover to or near the pre-mining conditions, i.e. the period during which the hydrological system may continue be impacted by the mining operations.

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The act of mining changes the nature of the ground within the area that is mined, and also above the area that is mined. These physical changes affect the flow of groundwater near a mine. By removing coal and interburden within drifts and longwall panels, some water is released immediately, but only from pores and fractures within the mined material. The collapse of the roof immediately above longwall panels means that groundwater stored in this zone is also released, but since the effective porosity of fractured rock can be 0.1% or less, each cubic metre of ground may yield a litre of water, or less. Water within the affected volume is often low quality, and very old. The most significant impact of mining from a hydrogeological point of view is that internal air pressure on the roof, walls and floor of mined cavities is for all intents and purposes atmospheric, i.e. zero pressure (relative to gauge). Just like at the regional water table, perhaps hundreds of metres above, piezometric head on the surfaces of the mine becomes equal to elevation. New hydraulic gradients are established near the mined volume, causing flow of groundwater towards the mine. The mine becomes the new low point in the hydrological system, the new sink, until such time (long after mining) that pressures and heads return to pre-mining values. Initially, the drop in head in the mine causes groundwater within the coal seam aquifer to flow almost horizontally towards the mine. The aquifer itself does not drain. Because of the drop in water pressure, groundwater in the aquifer expands. Although water is often considered to be incompressible, its finite compressibility allows some water to be released by this expansion. As heads decline in the coal seam aquifer, to larger and larger distances from the mine, a “cone of depressurisation” is established. The reduced heads within the cone lead to a tendency for vertical seepage to occur in adjacent aquitards, both downwards from above and upwards from below. The vertical hydraulic conductivity of aquitards is sometimes so low that leakage into the coal seam aquifer is minimal. In some circumstances, the leakage from above could induce flow downwards from the water table. The rate of downwards flow is controlled by the distribution of vertical hydraulic conductivity throughout the region of downwards flow. If the whole region between water table and mine were to equilibrate with steady flow, and if the region were homogeneous with uniform vertical hydraulic conductivity, the average vertical hydraulic gradient would be 1, and the rate of leakage would be equal to the vertical hydraulic conductivity. In a layered system, the effective vertical hydraulic conductivity is known as the “harmonic mean”. Its value depends on the hydraulic conductivities and thicknesses of all layers. The calculation used to find effective properties for these “conductors in series” is analogous to that used for electrical “resistors in parallel”, as taught in high school physics. The end result is that a thin very low conductivity layer can provide a very significant barrier to flow. Overall resistance is dominated by the layer with the lowest hydraulic conductivity. If leakage were to occur from a water table aquifer, the extent of lowering of the water table would depend on horizontal hydraulic conductivity in the water table aquifer and on the regional extent of that aquifer. If the aquifer were relatively impermeable, or of limited extent, the total volume of leakage and the lateral extent of the impacts would be limited.

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Any lowering of the water table also leads to the possibility of a phenomenon called “induced recharge”. Under normal hydrological conditions, recharge to the water table is limited by the proximity of the water table to the land surface, and by the spatial distribution of vegetation whose roots take water from the unsaturated zone. Evaporation and transpiration remove water from shallow water tables, taking water that might otherwise become recharge to the groundwater system below. If the water table is lowered, by any means, he hydrological system can sometimes evolve towards a new equilibrium with slightly lower surface runoff, slightly lower evapotranspiration, slightly higher recharge and slightly higher rate of groundwater flow into the regional groundwater system. The terms groundwater flow, groundwater flux, seepage and leakage are often used synonymously. However, it is useful to distinguish between “seepage” into a mine and “leakage” from nearby surface water. Seepage starts the moment that mining starts. Leakage may occur much later, or may not occur at all. How a hydrological system responds to mining can only be assessed by groundwater flow modelling.

G.2 MODELLING OF GROUNDWATER FLOW, GUIDELINES AND REVIEWS

G.2.1 Groundwater flow modelling

The only method that can be used to predict the impact of mining on groundwater is based on the use of computers to calculate how groundwater moves through the ground. The term “modelling” is widely used in all areas of science and technology. The methodology is fundamentally the same.

Scientists and engineers first set out to develop a “conceptual model” of the system of interest, identifying the physical (and sometimes chemical and biological) processes of importance.

The next step involves choosing mathematical equations that have been shown to represent these processes, leading to a “mathematical model”. Most of the mathematical models used today were developed and understood tens of years ago, so practitioners today simply select the model they will rely on. Groundwater hydrologists rely on Darcy’s Law, equations that describe unsaturated flow and flow in networks of fractures, and the concept of a water balance to ensure that the sum of flows is equal to the change in storage at all locations at all times.

The next step involves choosing a “numerical method” for solving the mathematical model. Most of the time it is not possible to solve the mathematical equations by hand. The equations that need to be solved must be converted to a form that can be implemented in computer software. Again, practitioners today generally choose a method that was developed long ago. Groundwater hydrologists rely on finite difference and finite element models, and occasionally finite volume or boundary element methods. All the methods have both advantages and disadvantages.

In order to undertake an assessment, practitioners must select commercial software (a computer “package” or “code”) that implements the numerical method of choice, and must gain a sufficient level of experience using the software to be able to apply it to the assessment at hand. Groundwater hydrologists choose from a relatively small number of commercial packages. The most widely used are:

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MODFLOW: an open source finite difference code developed by the United States Geological Survey; supported in a variety of commercial graphical interfaces, including Visual MODFLOW, Groundwater Vistas and GMS.

MODFLOW-SURFACT and MODHMS: commercial extensions of MODFLOW designed to overcome some of the weaknesses in MODFLOW: SURFACT is supported in Visual MODFLOW, Groundwater Vistas and ViewHMS.

FEFLOW: a commercial finite element code that has its own integrated graphical interface.

While data are needed to develop a conceptual model, further effort is required to collect and utilise measurements. Groundwater models divide a three-dimensional region into hundreds of thousands or millions of elements, and calculate the piezometric head in each element, according to the water balance equations described above. To do so, it is necessary to assign values of “hydraulic properties” (hydraulic conductivities, and two types of storage coefficients, representing specific storativity and specific yield) to every cell. These values are known as “model parameters”. The values are estimated taking into account all available information, including direct measurements if possible, and measurements of piezometric heads in observation bores.

The next stage in the modelling process involves setting up a representation of the physical problem using the modelling software. At this stage, the model becomes an implementation of a “computer model”. Modelling proceeds through several well accepted stages before it becomes the “model” used for predictions:

model calibration (adjusting model parameters until the model can reproduce the historical behaviour of the physical system, to a sufficient level of accuracy),

sensitivity analysis (assessing the sensitivity of model calibration to the values of individual model parameters),

model predictions (simulating a number of future scenarios), and uncertainty analysis (assessing the robustness of model predictions to

uncertainty in model parameters). Modelling is sometimes described as a mixture of art and science. It is indeed a very technical field of endeavour, so it is very much a science. Judgement is always needed to assess whether or not a model is sufficiently accurate for current purposes, and the ability to judge comes with experience. To the extent that modelling is an art, it is a serious form of art. There is no way to predict the impact of mining without models. At the same time, there is an increasing expectation that models can or should be able to answer all questions. This is not generally the case. There is sometimes an expectation that one large regional scale model can provide answers to questions at a regional scale, as well as answers to local scale questions at locations of interest, e.g. at a specific location in the mine, near a specific pumping bore or at a location where stream-aquifer interaction may occur. This expectation is unrealistic. It may be better to address questions at different scales with a hierarchy of models designed to be used at different scales. The issue of the expectations placed on groundwater flow models will be considered further below.

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G.2.2 Guidelines, reviews and audits

There are no Australian or international standards that prescribe how a groundwater flow model should be developed. However, practitioners in Australia refer regularly to a set of guidelines developed in 2001 by the Murray-Darling Basin Commission, the so-called “MDBC guideline” (Middlemis et al, 2001). It is important to note that the guideline does not define standards. The preface to the MDBC guideline explicitly states that “these guidelines should not be considered as regulation or law, as they have not received endorsement from any of the jurisdictions they encompass. These guidelines should not be considered as de facto standards as they are likely to evolve with modelling requirements and the sophistication of modelling approaches. They also have not been formally endorsed by water managers or agencies on either a national or Murray-Darling Basin basis.” The MDBC guideline makes clear distinctions between three levels of model complexity and suggests that different approaches to modelling and reviewing are appropriate depending on the agreed level. Models developed to assess the potential impact of mining projects are generally classified as “impact assessment models”, the middle of the three levels of complexity. Mining impact assessments are often characterised by a lack of data, e.g. relative to water resources assessments nearer to population centres, because little or no hydrogeological exploration activities have taken place prior to mineral exploration. Models prepared for mining impact assessments can rarely be calibrated as well as models of water supply borefields that have been operated for many years. The MDBC guideline considers the way in which groundwater modelling studies can be reviewed, and distinguishes between model appraisals, peer reviews, model audits and model post-audits. The modelling undertaken as part of the proposed project is of sufficient complexity that appropriate review should be at least at the level of a peer review. Model audits are rarely undertaken, as they require the reviewer to use the same computer software as the proponent’s consultants to check how the model has been set up and run.

G.3 ASSESSMENT METHODOLOGY

The Minister’s direction to the Commission was that it should review the Environmental Assessment for the project, taking into consideration any issues raised in submissions and three other studies and reviews.

G.3.1 Environmental Assessment and other documents prepared by proponent

This assessment is based on consideration of documents prepared by the proponent, initially as part of the Environmental Assessment itself, and subsequently during the period of this review by PAC, in response to requests by the Commission for further information and as supplementary submissions. The proponent prepared and provided a detailed response to all EA submissions (see Section 3.2 of the Main Report).

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Material provided to the Commission during this review has helped to clarify many issues. The review by Kalf and Associates Pty Ltd, for example, provides support for the conceptual model utilised by Mackie Environmental Research. It also considers examples of longwall mining beneath water bodies and the ocean, analysis of the results of testing of hydraulic properties before and after longwall mining and provides discussion of comments made in a number of key submissions.

G.3.2 Issues raised in submissions

Submissions include reports, letters and e-mails submitted by members of the general public, government agencies and non-government organisations. Submissions including additional explanatory materials were also accepted from the proponent. Comments covered a number of common themes:

The potential impact of leakage of groundwater on streamflow and water supplies.

Failure to assess regional structural geology and to consider the potential impact of faults or shear zones.

Adoption of values of vertical hydraulic conductivity that are unjustifiably low, hence that would be expected to under-predict the potential for leakage from the surface towards longwall panels.

Belief that at least 2 years of groundwater monitoring is needed, especially in the coal seam aquifer.

G.3.3 Issues raised in the strategic review

The strategic review into the Impacts of Potential Underground Coal Mining in the Wyong LGA (DoP, 2008) raised general issues related to the availability of data on groundwater, which led to the focus of the Wyong Water Study (SKM, 2010) on data rather than processes and potential impacts. The strategic review is discussed further in Appendix D.

G.3.4 Issues raised in the Wyong Water Study and its peer review

The Wyong Water Study and its peer review by Aqualinc (2010) are discussed in detail in Appendix E.

G.4 PREDICTION METHODOLOGY

G.4.1 Hydrogeological conceptual model

The conceptual model proposed by Mackie Environmental Research (2009) assumes the occurrence of groundwater in shallow and highly variable unconsolidated alluvial deposits (sands, silts, clays), in shallow weathered sandstone (with flow in fractures that have been opened through stress relief) and in regional sedimentary rocks and coal measures.

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The sedimentary sequence is as follows (see Figure 2.9 in the EA):

Terrigal Formation

Patonga Claystone

Tuggerah Formation

Munmorah Conglomerate

Dooralong Shale

Permian (Newcastle) Coal Measures, including Wallarah / Great Northern Coal Seams

The definition of these units is based on exploration bores that cover the project area, as shown in Figure G-1. The Figure shows surface geology. The lowest unit that outcrops within the area of longwall mining is the Patonga Formation. This is overlain by alluvium in the Dooralong Valley (Jilliby Jilliby Creek) and the Terrigal Formation in the hills to the west.

Figure G-1: Exploration boreholes, superimposed on surface geology and known dykes The stratigraphy dips generally to the southwest, as shown in Figure G-2. The conceptual groundwater model assumes that recharge in the hills flows towards nearby streams but also towards the streams in valleys, and at depth towards the Pacific Ocean in the east. This concept of nested flow systems at local and regional scales is well understood and accepted.

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Figure G-2: Three-dimensional model domain showing surface topography and dipping layers

In conceptualising the system in this way, an experienced modeller would set out to simulate pre-mining conditions using boundary conditions at rivers and streams that would drive flow from recharge areas towards the rivers and streams. To simulate the potential impacts of mining, hydraulic properties and boundary conditions would be modified to represent a new low point in the hydrological system.

G.4.2 Hydraulic properties prior to mining

Geological structure Hydraulic properties are intimately linked to geological structure. An experienced hydrogeologist first considers structure and then assesses the hydraulic properties of geological units. Depending on the relative magnitude of hydraulic conductivities, it is possible to classify geological units, or sequences of geological units, as hydrogeological units, known variously as aquifers, aquitards, or on rare occasions, aquicludes. A number of submissions have claimed that inadequate efforts have been made to identify the possibility of faults, shear zones or dykes. DECCW (2010, Attachment 1) state that: “DECCW understands that there may be faults under Jilliby Jilliby Creek”. Furthermore, “it is ... of concern that Northern Geoscience (2005) state: ‘A major geological feature of the Jilliby Creek is that it follows a fault zone approximately 1.3km west of Mount Alison. The drainage runs along the fault in almost a direct line to the south for approximately 1.5 kilometres ... Midway along this feature the Little Jilliby Creek converges into Jilliby Creek and is interpreted as a conjugate fault zone which the Little Jilliby Creek has incised... The significance of the feature is that it provides a

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significant transient pathway to groundwater movement and discharge into the surface stream flow regime.’ If correct, the potential for fault zones to exist in this area has significant implications for groundwater and surface water flows if they are undermined, particularly if/when the near surface strata are fractured and dilated.” The report by Northern Geoscience (2005) was prepared in opposition to proposals by Sydney Gas Limited to extract coal seam methane. In response, DPI (2005) found negligible risk in relation to nine separate issues, and concluded that: “The Northern Geosciences report does not raise any issues which have not previously been considered by DPI-Mineral Resources. It does not demonstrate that any of these potential impacts are likely to be significant in the context of the current proposal by Sydney Gas for JB9 and JB13.” In response to Northern Geosciences’ claim that "There is a significant case to be made for the occurrence and connection between shallow zones and deeper aquifers”, DPI stated that “There is unlikely to be any real potential for connection between near-surface aquifers and the deeper coal seam aquifers of the Dooralong and Yarramalong Valleys.” Pells Sullivan Meynink (2010, p.14) also state that: “...it is unlikely, but not impossible, that there are other undetected geological structures within the study area. These structures can cause surface bumps to occur. They can potentially also provide flow paths for water and gas. The last aspect above is not discussed in the EA but it is not expected to be of concern with regard to the known geological structures as they are either well away from areas of predicted subsidence or in areas where any additional water ingress should not affect surface water.” The proponent recognises that regional scale structures must be taken into account in mine planning. Figure G-1, for example, shows northwest to southeast trending dykes, outside the area of proposed longwall mining. Evidence has been presented to the Commission of regular revisions to the mine plan since 1995. These revisions have been designed to avoid potential impacts on the Wyong River and in some cases to avoid areas of weakness, e.g. a sill in the coal seam that has led to excision of a region along the southern boundary of the proposed mine plan. The region of dykes to the northeast of the proposed mine is consistent with plans shown in a recent community newsletter (June 2010) for Centennial’s Mandalong Southern Extension Project. The proponent has undertaken geophysical surveys to look for faults within the project area. In a presentation to the Commission, the proponent described 30 km of 2D seismic surveys, 2 km of 3D seismic surveys, 25 km2 (3000 km) of 3D marine seismic surveys as well as high resolution ground magnetic surveys. All core logs have been examined by the proponent looking for evidence of faults and shear zones. Properties of sedimentary rocks Within individual hydrogeological or “hydrostratigraphic” units, hydraulic properties are generally based on assuming that the rock matrix behaves like an equivalent porous medium. Pells Sullivan Meynink (2010, p.19) state that: “…the Mackie report has assumed that … there are no joints or defects within most of the rock strata above the coal seam and therefore no pathways for water flow other than directly through the pore space within the sandstones, siltstones and claystones.”

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In fact Mackie Environmental Research (2009, Section E4.1) state explicitly that: “Extensive core inspections suggest (that) micro fractures or joints that might enhance hydraulic conductivities are generally sparse at depth.” Mackie Environmental Research have examined and relied on cores in the proponent’s core shed in Wyong. One core is laid out and is available for public viewing. Three methods have been used to estimate hydraulic conductivities within hydrogeological units:

The first method is based on 171 packer tests performed in situ in 31 boreholes by Coffey Partners International (CPI) in 1998. Mackie Environmental Research (2009, Appendix D.1) has argued that:

packer testing implies a value of horizontal hydraulic conductivity that is dominated by narrow zones of high hydraulic conductivity and is incapable of measuring the hydraulic conductivity of the less permeable material in any test length especially when test lengths average 30 m, and are as long as 200m;

most of CPI’s results were recorded as being “below quantitation limit” (“bql” in Table D.1 of Mackie Environmental Research (2010)), i.e. CPI reported an upper bound for hydraulic conductivity rather than an accurate measurement.

He therefore argues that packer test results are over-estimates.

The second method is based on a laboratory testing (Mackie Environmental Research, 2009, Appendix D.2):

helium permeability was measured for 39 samples taken from 3 cores, some samples being drilled across the core to infer horizontal hydraulic conductivity and some being drilled parallel to the length of the core to infer vertical hydraulic conductivity;

geometric means were determined within each hydrogeological unit (Mackie Environmental Research, 2010, Table D.4), except that mudstone and claystone were not analysed, so estimates for Patonga Claystone and Tuggerah Formation are believed to be overestimates, especially in the vertical direction, because they do not account for these lower conductivity materials;

The third method is based on a combination of laboratory testing and calculation of effective hydraulic properties (Mackie Environmental Research, 2009, Appendix E4.1):

laboratory data and experience from other locations were used to develop a list of horizontal hydraulic conductivities by material type (Table E.1). The Table has been extrapolated to include values for materials for which direct measurements were not able to be obtained, because the materials can not be sampled from primary core (Section D2).

The results were then analysed as described in Section E4.1, using detailed logging to assign material types to lengths of core as short as 10 mm, then by computing effective hydraulic conductivities in the horizontal and vertical directions as thickness-weighted arithmetic and harmonic means, respectively.

This third method takes into account the effect of thin layering in sedimentary strata. The effective anisotropy ratio within units increases relative to that within individual

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material types, because effective horizontal hydraulic conductivity within a formation is dominated by those materials with larger horizontal hydraulic conductivity while effective vertical hydraulic conductivity is dominated by those materials with very low vertical hydraulic conductivity. Figure G-3 shows the important influence of claystone (with horizontal hydraulic conductivity of 5 x 10-7 m/d) on formation average hydraulic conductivity, especially in Patonga Claystone and the Tuggerah Formation.

Table G-1: Estimates of hydraulic conductivities

Formation Packer testing1 Lab/core testing2 Computed3

Kh (m/d) Kv (m/d) Kh (m/d) Kv (m/d) Kh (m/d) Kv (m/d) Terrigal Formation - - 3.31 x 10-3 3.74 x 10-4 2.1 x 10-5 3.6 x 10-6 Patonga Claystone 2.11 x 10-4 - 1.47 x 10-3 9.19 x 10-6 1.8 x 10-5 3.8 x 10-6 Tuggerah Formation 4.61 x 10-5 - 3.31 x 10-5 2.11 x 10-5 3.1 x 10-5 1.5 x 10-6 Munmorah Conglomerate 3.05 x 10-5 - 4.13 x 10-6 9.07 x 10-6 3.4 x 10-3 2.3 x 10-6 Dooralong Shale 2.59 x 10-5 - 1.07 x 10-5 2.68 x 10-6 2.0 x 10-5 2.7 x 10-6 1 Mackie Environmental Research (2009, Table D.2), vertical hydraulic conductivity not measurable by this

technique. Values computed as geometric mean of values in Table D.1, by formation.

2 Mackie Environmental Research (2009, Table D.4). All values computed as geometric mean of values in Table D.3, by formation rather than by material type. Only 2 samples in Terrigal Formation and samples in Patonga Claystone were in sandstone only. There were no samples in claystone, which is believed to be less permeable than siltstone/laminite, which in turn is less permeable than sandstone.

3 Mackie Environmental Research (2009, Table E.2). The results for Kv are strongly influenced by the belief that the horizontal hydraulic conductivity in claystone, laminite and shale is as low as 5 x 10-7 m/d, an order of magnitude lower than in fine grained sandstone.

Figure G-3: Variability of horizontal hydraulic conductivity within three boreholes

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The approach adopted by Mackie Environmental Research is based on observation rather than assumption. In fact all units from the Terrigal Formation to the Dooralong Shale have remarkably similar properties (see Table G-1), varying only by a factor of 2. Horizontal hydraulic conductivities vary from 1.8 to 3.4 x 10–5 m/d, and vertical hydraulic conductivities vary from 1.5 to 3.8 x 10–6 m/d. The anisotropy ratio (the ratio of horizontal to vertical hydraulic conductivity) within formations varies from ~5 in the Patonga Claystone to ~20 in the Tuggerah Formation. Based on laboratory measurements of porosity and Young’s modulus, Mackie Environmental Research (2009, Section 3.3.1 and Appendix E4.3) estimate specific storativity to be in the range 1 to 3 x 10-6 m-1, with an average of 2 x 10-6 m-1. Specific yield in sedimentary units is estimated to be 0.001%, based on the influence of joints and fractures, as distinct from drainable porosity in the matrix of intact rock; this parameter is important where the Terrigal Formation and Patonga Claystone units outcrop, since very low rates of recharge would cause a rapid rise in water table elevation in response to individual recharge events. Properties of alluvium Unconsolidated and variably saturated alluvial sediments occur at the surface within the Dooralong and Yarramalong valleys. These sediments typically attain thicknesses of 10 to more than 30 m and comprise mixed and variables sequences of Sands, silts and clays (Mackie Environmental Research, 2009, Section 2.3). Falling head tests at 12 locations in 1999 were re-analysed by Mackie Environmental Research, giving similar results. While the hydraulic conductivity of clay will be less than that for silt, sand and gravel, a bulk average for a mixture of all material types is believed to be in the range 0.1 to 5 m/d. A bulk average specific yield (drainable porosity) is estimated to be about 20%.

G.4.3 Hydraulic properties following mining and subsidence

If the project were to proceed, subsidence would occur. Potential impacts on groundwater and surface water would be controlled by the extent to which hydraulic properties change above the proposed longwall mining, in the zone affected by subsidence, as well as by changes in boundary conditions. In this section, the focus is on changes in hydraulic properties. Two distinct lines of reasoning have been and can be used to argue that hydraulic properties will change very little in a so-called “constrained zone” above the mine, thereby limiting loss of water from the surface to the mine below.

The first relies on geomechanical modelling of the subsidence process, and predictions of the type and magnitude of deformation in different zones. This style of modelling has been developing over the past 10 years, and is supported by observations in the field at numerous mines.

The second relies on experience at other mines, and is particularly relevant when considering the impact of structural geological discontinuities.

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Geomechanical modelling and predicted changes in hydraulic properties In this area, Mackie Environmental Research (2009) relies on studies undertaken by MSEC and SCT (2010). Over a period of more than 10 years, SCT has developed a methodology using geomechanical software known as FLAC, with additional modules developed by SCT, top predict the deformation of the rock mass overlying longwall panels, the distribution of horizontal and vertical strain throughout the rock mass, and impacts on hydraulic properties. The results of this kind of modelling are consistent with the conceptual model presented in Figure 2.4 in the Main Report. Of particular importance is the “constrained zone”. In the absence of major geological discontinuities such as faults and dykes, water inflow to mine workings through this constrained zone is determined by the natural permeability of the rock mass within it. SCT’s starting point is the strength of the rock. MSEC and SCT (2010, Sections 2.3.1 and 2.3.2) state that “the Patonga Claystone… (and) the Tuggerah Formation… are characterised by abundant interbedded green and red claystone units of low bedding plane and material strength. The green and red claystone units typically are in the 10-30 MPa range.” Measurements of strength on core samples have been correlated with sonic velocity, allowing the use of downhole geophysical (sonic) logs to obtain a detailed characterisation of rock units. Figure G-4 shows a typical distribution of unconfined compressive strength (UCS) (MSEC and SCT, 2010, Figure 2.10). The significance of this Figure is its relationship with Figure 3, and the occurrence of material with UCS in the 10-30 MPa range at depths that suggest the occurrence of claystone in the Patonga Claystone and Tuggerah Formation.

Figure G-4: Unconfined compressive strength in overburden Mackie Environmental Research (2009) has placed considerable reliance on the relative abundance of claystone above longwall panels, and on his interpretation of low vertical hydraulic conductivity prior to mining. MSEC and SCT (2010) do not explain the role of

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claystone in great detail, however SCT (1999) undertook studies for Coal Operations Australia Limited, on the lease held by the proponent. Figure G-5(a) (from SCT, 1999) shows stratigraphy to a depth of 430 m, with material of low strength (10, 20 and 40 MPa) in the upper 180 m of the profile. Figure G-5(b) shows that in spite of significant failure to a height of 100-150 m immediately above the mined panel, and in spite of fracturing to a depth of 120 m near the land surface, there remains a zone of significant thickness, from 125 to 215 m below the surface, where there is no indication of vertical fracturing. Figure G-5(c) shows that pore pressures in the zones with vertical fracturing tend towards zero during mining, suggesting downwards flow, but it is well known that changes in heads and pore pressures are transient, and there is no explanation of how long it would take after mining for these conditions to exist, nor of the corresponding rate of flow. By the time steady state flow were established from the surface to the mine, pore pressure would be expected to be 0 MPa (atmospheric) throughout the section.

Figure G-5: (a) Stratigraphy, with (b) failure modes and (c) pore pressures after longwall

mining SCT (1999, Section 8) explain that “Permeability is a function of the strata type, the confining stress acting normal to the direction of flow and the volumetric changes caused by fracture and shear of strata. The results indicate that there are no fracture zones created which would significantly enhance the flow characteristics within the strata between the upper surface fracture zone and the mine workings.” They conclude (SCT, 1999, p.iii) that “there appears to be no vertical connection between the surface cracking zone and the mined seam which would allow direct acquifer (sic.) leakage from the surface to the mine.” SCT do not argue that the flow would be zero. They imply that downwards leakage would be controlled by the pre-mining vertical hydraulic conductivity in the layer that is not affected by fracturing. In recent studies, MSEC and SCT (2010, Sections 2.4.2 and 2.5.2) have predicted subsidence for two cases, described as the Hue Hue and Valley cases. They state that above the free draining zone, “the permeability is variable due to localised areas of fractured ground. The flow in this region is considered to be tortuous and limited by the thickness of strata which is not significantly modified by the subsidence movements”.

In their Figure 2.13, they show hydraulic conductivities obtained by packer testing as a function of depth. The values range just less than 10-7 m/s (about 10-2 m/d) to less than 2 x 10-9 m/s (about 1.5 x 10-4 m/d). These values are considerably larger than those adopted by Mackie Environmental Research (2009, Figure D.3) (see Table G-1 above), by about two orders of magnitude (a factor of 100).

(a) (b) (c)

constrained zone

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In their Figure 2.14, MSEC and SCT (2010) show horizontal and vertical hydraulic conductivity in an idealised section 430 m deep, based on assumed values of matrix hydraulic conductivity and generated distributions of horizontal and vertical fractures and bedding planes prior to mining. In other words, this Figure was intended to illustrate the fact that it is possible to generate a pre-mining representation of hydraulic conductivities that approximates the observations in Figure 2.13. There was no discussion about whether the average anisotropy ratio of 3 was reasonable. It is likely to be low. Furthermore, the generated hydraulic conductivities appear to be larger than the packer test data in Figure 2.13.

The results of FLAC simulations (their Figure 2.35) show the development of a free-draining zone, overlain by a constrained zone within which the primary form of deformation is horizontal “bedding shear and reactivation”. Throughout 100 m or more, there is no tendency for continuous or connected vertical fracturing. Note the arrow point to the left, apparently intended to indicate that “the expected undisturbed conductivity values are distributed to the left of the plotted values” (cf. response to Commission questions). Note that the curve showing 5m running averages should be showing 5m running harmonic averages, which are always less than arithmetic averages, but it is not clear whether this is the case.

In response to questions from the Commission, the proponents state that “SCT are of the view that undisturbed strata conductivities overall, are much lower than represented on Figures 2.13 and 2.15 (sic.) and are in agreement with the MER characterisation and the vertical hydraulic conductivities used in regional scale groundwater modelling above longwall mining.” (Their reference to Figure 2.14 should have been to Figure 2.15.)

It requires some extrapolation, but it appears that SCT and Mackie Environmental Research agree that:

i) SCT’s calculations are in principle correct, leading to the conclusion that following subsidence a constrained zone can be expected with very few vertical fractures and horizontal confining stresses that would keep any such fractures closed, and

ii) the conclusions reached by Mackie Environmental Research about very low effective vertical hydraulic conductivities (see Table G-1 above) are also correct.

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Figure G-6: Predicted vertical hydraulic conductivity for the Valley case To account for the impacts of subsidence, Mackie Environmental Research modified vertical hydraulic conductivities in the regional model. To be specific, vertical hydraulic conductivity was increased progressively in layers 8 to 12, almost by an order of magnitude in each layer. Whereas the vertical hydraulic conductivity in the Tuggerah Formation remained at 2 x 10-6 m/d in layers 6 and 7, it was set to 0.0004, 0.004, 0.04, 0.4 and 4 m/d in layers 8 to 12 respectively (proponent’s Response to Groundwater Questions, Table 1). In response to questions from the PAC, the proponent has explained that: “The reason for the discrepancy is that SCT studies were focused on the evolution of deformation and the failure regime rather than the pre-mining conductivity regime. MER studies had an increased focus on the undisturbed regime. In assessing this regime, MER reviewed the packer tests, held discussions with the packer test operator (some years ago), inspected core and took advice from the W2CP geologist all of which lead to the view that undisturbed strata could be characterised by the matrix conductivities of the different strata at the scale adopted for numerical modelling. Packer tests conducted at Mandalong (Forster, 1997) were also considered by MER where six of seven tests in similar strata returned conductivity estimates in the range 1e-06 m/day to 4.9e-05 m/day consistent with the low values determined for W2CP and used in groundwater modelling.” (Note: these values at Mandalong refer to horizontal hydraulic conductivities. Vertical hydraulic conductivities could be expected to be up to an order of magnitude lower.) It is important to note that SCT’s methodology for calculating the impacts of longwall mining is well documented:

Gale (2008, ACARP C13013) describes the methodology outlined above.

Meanwhile, several others have developed similar methodologies:

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Waddington and Kay (2001, ACARP C8005) describe CSIRO Petroleum’s use of two other computer codes, UDEC and FLOMEC, to study subsidence under cliffs, gorges and river systems, largely in NSW.

Guo, Adhikary and Gaveva (2007, ACARP C14033) describe CSIRO Exploration & Mining’s use of COSFLOW, a three-dimensional finite element code, to predict the impacts of subsidence at the Springvale Colliery in NSW.

While the different types of models work differently, the basic concepts and outcomes are similar. It is useful to note the depth of cover over the proposed mine plan, as shown in Figure G-7 below, based on EA Figure 2.6. Depth of cover is more than 375 m in all areas underlying Jilliby Jilliby Creek. Mining is not proposed to occur near Jilliby Jilliby Creek until the end of longwall panel LW 5N, approximately 5 years after the start of mining.

Figure G-7: Depth of cover over proposed mine plan On the balance of evidence, the Commission accept that it is likely that a constrained zone will exist, absent geological features, as long as panel width is small enough relative to depth

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of cover, and that on average, throughout the region of longwall mining, effective vertical hydraulic conductivity through that zone will be close to pre-mining values as inferred from observations of core and laboratory testing. This is not to say that there will not be localised areas where other mechanisms become important. The effect of geological structure is discussed below, in the context of mining at other operations. Impact of geological discontinuities The proponent advised the Commission that:

While the W2CP project team is confident that the proposed mine area is well defined and well understood, it accepts that minor faulting may exist and probabilistic modelling has been used to incorporate potential occurrences in the mine design. The inherent risk of encountering such a feature that is likely to produce a significant water inflow to the mine is considered to be very low. This is based on experiences in the South Newcastle Coalfield where operations mining in the Wallarah and Great Northern seams beneath Lake Macquarie commonly encountered faults at a third of the W2CP cover depth, without experiencing major inflows.

The increased depth of cover and the predominance of shales and claystones in the overburden suggest that the likelihood of a fault providing significant connectivity between the surface and the workings is considerably less than that experienced in the South Newcastle Coalfield. 1

The following matters arise out of this response:

The majority of workings beneath water bodies in the South Newcastle Coalfield were approved in accordance with the Wardell Guidelines for Mining Under Tidal Waters (Wardell, 1975) and therefore have an approval condition that:

No total extraction or pillar extraction to be permitted within a distance of 40 m of any known fault having a vertical displacement greater than 3 m nor any dyke having a width greater than 6 m.

The focus to date in designing mine workings beneath tidal waters in the Newcastle Coalfield (there are extensive workings, including longwall workings, beneath the Pacific Ocean, Newcastle Harbour, Lake Macquarie, Lake Munmorah, Budgewoi Lake and the northern end of Tuggerah Lake) has been on avoiding direct hydraulic connections to the surface such that safety is not jeopardised by inundation of the mine workings. There has been a secondary focus on controlling the rate and volume of water inflow such that it does not adversely affect ground stability and mining operations. The focus has not been on preventing seepage of groundwater into the workings along geological features.

In a recent review on behalf of the proponent, Kalf and Associates Pty Ltd (2010)2 quote Booth (2002) as follows: “the successful operation of longwall mines under lakes and the

1 WACJV (2010a), response to PAC Question 1.14. 2 Kalf and Associates Pty Ltd (2010), Wallarah 2 Coal Project, Review of the Mackie Environmental Research Modelling Report, field evidence and stakeholders comments, 27 October.

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sea convincingly demonstrates that a confining zone normally exists and that highly permeable fractures directly connecting the mine to the surface generally do not exist.” Useful references are also made to the findings of the Reynolds Inquiry in 1977, and to the outcome of mining beneath Cataract Reservoir: “All of the investigations into groundwater monitoring, injection tests and water inflow into the mine indicated no evidence of any significant changes in the hydraulic connectivity from the reservoir to the mine workings… The results of various investigations undertaken by the colliery indicated that surface and subsurface strata disturbance due to mining of the six panels had no detrimental effects on the integrity of the reservoir.” The Commission concludes that:

There is a potential for geological structures to impact on surface and subsurface drainage.

This potential is likely to be low given the considerable depth of mining, the considerable thickness of the alluvium and the drainage characteristics of the alluvium and shallow aquifer systems.

Any conditions of approval should require management plans with requirements specific to geological discontinuities (structures) that are underpinned by at least an extensive groundwater monitoring system, continuous water balance assessments (water in – water out of the mine), and a requirement to review subsidence and groundwater related predictions whenever geological structures above nominated thresholds (displacement, width etc.) are encountered and to seek approval to continue to mine in those areas.

Given all these conclusions, the Commission concurs with the findings of the Wyong Strategic Review (DoP, 2008) that “in the absence of major, unforeseen geological anomalies (e.g. faults and dykes), subsidence-induced hydraulic connectivity between Wyong River, Jilliby Jilliby Creek or their alluvial systems and any underlying mine workings is extremely unlikely”.

G.4.5 Boundary conditions and recharge

Boundary conditions for the model are described by Mackie Environmental Research (2009, Appendix E.5), but not in detail. The most important boundaries are along streams, where the stream elevation defines the level to which regional groundwater flow is attracted. It is not clear whether no flow conditions have been assumed on all external boundaries to the rectangular model domain, or perhaps on three sides with the fourth having heads fixed to sea level, but if so, such conditions would not be unusual, and these external boundary conditions will have little influence on predictions in the first 200 years. Water table elevations have not been fixed in the hills. Rather, average values of steady recharge have been applied to different zones (Mackie Environmental Research, 2009, Figure E.5): 0.15 mm/y to outcropping hard rock, 5.5 mm/y to the tops of hills, 50 mm/y to alluvials and 90 mm/y to coastal sands closer to Tuggerah Lake. These values have been obtained by trial and error, and are very much controlled by estimates of vertical and horizontal hydraulic conductivity.

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Questions have been asked about the dependency of recharge estimates on estimates of hydraulic properties (Pells Sullivan Meynink, submission to the Commission at public hearing). The fact that recharge and hydraulic conductivity are individually difficult to estimate comes from the form of the water balance equation, and the fact that in a homogeneous isotropic situation, it is the ratio of recharge to hydraulic conductivity that is identifiable, not the parameters themselves. The solution to non-uniqueness issues is to utilize other sources of information on one parameter or the other or both. Recharge can sometimes be constrained by estimates of runoff and baseflow, but in this case, Mackie Environmental Research have chosen to place more weight on hydraulic conductivities. If the latter were 100 or 1000 times larger, recharge to the various zones would also have to be a lot larger.

G.4.6 Choice of modelling software

Mackie Environmental Research chose to use MODFLOW-SURFACT, based on their experience with this and other software. MODFLOW-SURFACT is a three-dimensional finite difference code. It was developed as an extension to MODFLOW, with specific additional features designed to allow drying and re-wetting of cells. MODFLOW itself does not handle drying and re-wetting robustly. MODFLOW-SURFACT allows cells to desaturate. This is useful in considering the impacts of longwall mining because the goaf (caved zone) and the overlying fractured zone drain rapidly and become unsaturated. Mackie Environmental Research chose to use this capability to represent the release of water from this damaged zone into the mine. At least one submission has challenged the use of MODFLOW-SURFACT. Pells Sullivan Meynink (2010) state that “Mackie have used the computer program, Modflow, which is widely used for this kind of work but is not a true three dimensional model. It attempts to take three dimensional factors into account through a ‘smearing’ process in vertical, one dimensional columns.” The Commission rejects this claim. Both MODFLOW and MODFLOW-SURFACT are fully three-dimensional. The review by Kalf and Associates Pty Ltd (2010) also rejects this claim.

G.4.7 Modelling methodology

The model is a 14-layer model covering an area of 575 km2. There are 105768 cells per layer, hence 1.48 million cells in total. The model is variably saturated, allowing cells to desaturate in and above the goaf. Individual cells are as small as 50 m square. This allows a large number of cells to represent the shape of longwall panels. The degree of detail in the temporal representation of the mining schedule is not described by Mackie Environmental Research (2009), but it is likely that during each year of a simulation, the properties of cells in and above longwall panels mined in that year are changed to represent the act of mining – with effective hydraulic conductivities and porosity increased in the goaf and fracture zone.

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G.4.8 Calibration

Calibration of the model has only been attempted in steady state because the regional hydrogeological system is in quasi-equilibrium with the climate, and has not been stressed sufficiently at a regional scale to allow any form of transient calibration. The locations of monitoring bores are shown in Figure G-8. The goodness of fit between model and data is shown in Figure G-9. Piezometric heads vary between 185 mAHD and nearly sea level. Within this range, the model over-predicts some heads by up to 50 m and under-predicts by up to 30 m. The differences are large, and indicate that the model does not include enough detail to capture all the physical variations and processes that caused observed heads to be what they are.

Figure G-8: Location of groundwater monitoring bores near the proposed mine used in model calibration

NOW (2010) indicated that “NOW considers the MODFLOW-SURFACT model developed for the proposal to be deficient for robust predictions of groundwater interactions in post-subsidence conditions. NOW has significant reservations as to the adequacy of the model, as it is uncalibrated to its transient and steady state modelled outputs, and is based on a simplified conceptual framework of groundwater interactions between the alluviums connected to the Wyong River and Jilliby Jilliby Creek and tributaries. It does not provide sensitivity assessment of model outputs to the steady state runs, which is inadequate for a sensitive environment, such as presented by the Jilliy Jilliby Creek and Wyong River alluvium.”

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Figure G-9: Location of groundwater monitoring bores near the proposed mine Mackie Environmental Research (2009, Section E7.3) argued that sensitivity analysis would be “of limited value”. They chose to rely on calculated effective hydraulic conductivities, effectively putting far more weight on core measurements and the methodology adopted than on sparse field observations of piezometric heads, especially given their belief that recharge from rainfall flows to streams in the uppermost part of the system (i.e. layer 1 in the model). In a presentation to the Commission at the public hearing in Wyong on 28 October 2010, Dr Pells of Pells Sullivan Meynink presented recent modelling results in two dimensions that show an almost linear relationship between recharge and hydraulic conductivity. Dr Pells argued that recharge values used by Mackie Environmental Research appeared to be too low (50 mm/y in valley floors, 0.15 mm/y on steep rocky hill slopes and 5.5 mm/y on the tops of hills). He argued that if recharge were two or three orders of magnitude (factors of 100 or 1000) higher, then effective hydraulic conductivities throughout the model could or should also be larger by the same two or three orders of magnitude. The relationship between recharge and hydraulic conductivity is well known, and is a direct result of the form of the water balance equation. A number of submissions have claimed that more data are needed before an assessment of the potential impact of the project can be made. This claim is based to some extent on the findings of the Wyong Water Study (SKM, 2010). The Commission has addressed this issue in Appendix E.

G.4.9 Sensitivity and uncertainty analyses

There is a distinction between sensitivity analysis, in which the sensitivity of model calibration to variations in model parameter values is tested, and uncertainty analysis, in which the sensitivity of model predictions to variations in model parameter values is tested.

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Mackie Environmental Research (2009) does not report on sensitivity analysis or uncertainty analysis. Section 7.3 explicitly argues that sensitivity analysis would not have had “limited value”. During an internal peer review conducted by Kalf and Associates Pty Ltd, Mackie Environmental Research (see letter to Blake Dawson 13/10/2010) provided the results of a specific kind of sensitivity analysis. Challenged to consider the possibility that hydraulic conductivities could be enhanced in the constrained zone, due to shear and dilation along horizontal bedding planes, horizontal hydraulic conductivities were randomly increased by factors up to 150 in the constrained zone. Sensitivity analysis was also conducted in relation to alluvium and stream-aquifer interaction. The results of these sensitivity studies support the results presented in the EA.

G.5 PREDICTIONS

G.5.1 Groundwater seepage into the mine

Model predictions are described by Mackie Environmental Research (2010, Section 7.1). In relation to seepage into the mine, it is predicted that inflows will commence at the start of mining, dominated by flow from deep hardrock aquifers. After 20 years, the inflow will peak at about 2.5 ML/d. Cumulatively over the life of the project, the total volume of inflow is expected to be about 26.5 GL. The model developed by Mackie Environmental Research relies on the integrity of the constrained zone, and the barrier that it would pose to leakage. The proponent is effectively claiming that 25 out of 26.5 GL flowing into the mine would come from depressurisation, i.e. from expansion of water stored deep below the earth’s surface. Less than 4% would come from shallow groundwater near the surface. The Commission entertains some uncertainty as to the source of this predicted inflow water. Should it prove to be an overestimate, the implications for mining are that mine water management is unlikely to be difficult. Project water balance is potentially more significant, if the inflow rates predicted in Figure E16.1 are either smaller or larger than in reality. If yield from depressurisation is smaller than predicted, and if the integrity of the constrained zone is maintained, it is conceivable that project water supplies from the mine may be less than anticipated.

G.5.2 Longer term impact of leakage on the water table and shallow bores

The model predicts negligible lowering in the water table in alluvial aquifers, as groundwater seeps downwards towards the goaf at ~2 x 10-6 m/d. Any downwards leakage must be balanced by either a reduction in storage (water table elevations) or a reduction in discharge to streams or both. Mackie Environmental Research (2010, Table E3) show that a reduction of 12 kL/d in baseflow to various streams is equivalent to leakage rates of up to 2 mL/m2/d over the areas of alluvium. This explains a small fraction of the 74.6 kL/d that could leak downwards at the end of mining.

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Consider the areas of alluvium associated with Jilliby Jilliby Creek in Table E3, about 8.5 km2. If specific yield in alluvium is 0.25, then leakage of say 50 kL/d would cause a lowering of the water table over this area of 0.023 mm/d or 8.5 mm/y or 0.34 m over 40 years. This explains to some extent why Figure E14, with a minimum contour of 2 m, fails to show any impact on the water table. The potential impact on shallow bores in the alluvium is likely to be negligible. Any lowering of the water table could in principle lead to a slight reduction in evapotranspiration, which in turn would reduce the tendency for the water table to be lowered. This phenomenon is known as “induced recharge”. Within a small range, it tends to ensure that a water table stays close to its equilibrium elevation. Pells Sullivan Meynink (submission to Commission at public hearing) attempted to demonstrate that the impact on deeper bores, e.g. in the Terrigal Formation beneath the alluvium, could be greater. Depressurisation of underlying formations will occur. Furthermore, nearly all of the 12 existing licensed bores that currently exist above the proposed mine are screened and draw their modest yields from sandstone or shale rather than from sands in the alluvium (EA, 2010, Table 8.2). Figure E14 suggests a lowering of head in the Terrigal Formation (layer 3) by 2 or more metres after 40 years. The long term response of piezometers at observation bores DO22 and DO32 is predicted to be such that heads in layer 5 continues to decline for 200 years (see Groundwater Response to PAC, Figure 3). Layer 5 is at the base of the Patonga Claystone, ~200 m below surface. There may be some impact on shallow bores into hardrock “aquifers” in the Dooralong Valley. The yield in these bores is small. The rate at which changes are likely occur is very slow. It is conceivable that a single borehole could “fail” due to localised damage in the rock immediately below that bore. However such failure would require displacement along a fault or other structure, and creation of sufficient hydraulic conductivity to facilitate drainage.

G.5.3 Loss of flow to surface water streams

Loss of flow could occur in two ways:

If a surface stream were located in bedrock, and if ground movement immediately below a stream bed created a pathway to the mine below, then leakage could occur directly from the stream. This could potentially occur in higher order streams in the hills where streams are incised in the Terrigal Formation. These streams are ephemeral, and any leakage from the stream bed is likely to be short term, and potentially removing a very small fraction of the streamflow.

In the valleys, where alluvium overlies bedrock and an alluvial aquifer provides baseflow to streams between runoff events, groundwater flows from the uplands to the streams. Any depressurisation of the rock underlying the alluvium could cause minor loss of groundwater, hence the discharge of groundwater to the stream as baseflow could decline.

The regional groundwater flow model presented by Mackie Environmental Research (2009) takes into account the stream network, and uses stream levels as boundaries for the regional groundwater flow system. However, the model was not designed to answer questions about

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stream dynamics. The model was calibrated in steady state, using long term average recharge and computing long term average flows. It was designed to predict long term changes in groundwater flow over a 40 year period. It uses finite difference cells oriented and sized to suit the mine plan, not to suit the detailed geometry of meandering streams. The model was not designed to simulate surface runoff and streamflow at the time scale of rainfall-runoff events. For these and other reasons, the model cannot be expected to be able simulate stream-aquifer interaction with accuracy. Mackie Environmental Research (2009, Appendix A) analysed base flows in Jilliby Jilliby Creek and the Wyong River. In Table E3, the three parts of the Jilliby Jilliby Creek catchment are estimated to yield ~1.6 ML/d prior to mining, or 584 ML/y. This is much less baseflow than the 3,000 ML/y estimated based on streamflow data (see Appendix H). In other words, any suggestion that the model provides a good representation of stream-aquifer interaction needs to be considered carefully. It is generally recognised that regional scale models of the kind developed by the proponent cannot be expected to simulate all hydrological and hydrogeological processes at all spatial and temporal scales with a high degree of accuracy.

G.5.4 Long term impacts and rate of recovery

Creating a mine at depth initiates a long-term transient that tends to cause groundwater flow towards the void (depressurisation of deep confined layers and vertical flow downwards from the surface towards the mine), followed by long-term recovery during which pressures and water levels recover. Because the mine is created by extraction of rock mass, a volume is vacated that will ultimately need to be filled with water. Part of that volume is filled by the process of subsidence, because collapse of the goaf partially fills the void. If 5 million tonnes were mined per year for 40 years, and if mined material has a density of 2.5 tonne/m3, then the volume vacated would be 80 million m3. If mining a 4.5 m seam led to average subsidence of 1.5 m, then the volume still to be filled would be ~53 million m3. If seepage into the mine during the mining life were indeed 26.5 GL, then the total volume of water required for complete recovery would be ~80 GL. Predictions by Mackie Environmental Research (2009) show recovery after 200 years, i.e. 160 years after the end of mining. Figure E17 shows that as water flows back into the mine workings in layer 12, gradually flooding the mine and raising piezometric heads and pressures, the cone of depressurisation continues to expand. At the same time, downwards leakage from above will have reached the surface aquifer, with a lower water table in layer 1, especially in the hills where the Terrigal Formation outcrops. The long term reduction of heads in layer 5 (see Section 6.5.2 above) is another example. In the proponent’s Response to Groundwater Questions, it is stated that “complete repressurisation may take longer than 400 years unless a recharge enhancement strategy to replenish deep aquifer storage is invoked”. In fact, looking at the slope of curves in that response, the recovery may be considerably slower. Just as the impacts of subsidence on groundwater and surface water depend on the accuracy of the assumption that the constrained layer will act as a barrier, it follows that predictions of

28

recovery rely on the same assumption. If the modelling has overestimated leakage, then the time for recovery may also have been overestimated. The concept of a recharge replenishment strategy is useful. There are several possibilities, ranging from gravity-fed recharge via boreholes during occasional flood events to pumping of seawater into the mine. While the latter concept may seem counter-intuitive, it deserves consideration.

G.6 FINDINGS AND CONCLUSIONS

If the project proceeds:

mining will cause subsidence,

deformation will cause changes in the hydraulic properties of the ground above the areas of longwall mining,

groundwater in the goaf and free-draining zone immediately above longwall panels will drain into the mine,

there may be changes in hydraulic properties in rock as far above the longwall panels as the land surface,

some changes in rock properties may occur in rock overlain by alluvial sediments in valley floors,

it is likely that there will be a zone at intermediate depths where horizontal hydraulic conductivities are enhanced due to shear along bedding planes, but where vertical hydraulic conductivities remain close to pre-mining values,

leakage from the water table towards the mine will occur, but rates will be controlled by the low vertical hydraulic conductivity in the constrained zone, and by potentially lower vertical hydraulic conductivity in the fractured zone above the goaf and below the constrained zone because of air entry (partial desaturation), leading in some areas to formation of a partial capillary barrier;

there will be short term changes in groundwater levels (elevations above sea level) as the surface subsides, and the depth of the water table beneath the land surface may change,

impacts on baseflow are likely to be very small, and almost undetectable in the context of normal variability, and

water table elevations may decline further in the very long term, unless special efforts are made to flood the mine before very slow leakage has an impact on the water table.

29

G.7 REFERENCES

Aqualinc (2010), Wyong Water Study: International Peer Review, report prepared for the NSW Department of Planning, August 2010.

Australasian Groundwater and Environmental Consultants (2010)

Mandalong Mine Groundwater Monitoring Review for AMER, report for Centennial Mandalong Mine, February 2009.

Byrnes, R.P (1999)

Longwall Extraction beneath Cataract Water Reservoir. Masters thesis submitted to the University of New South Wales.

Centennial Coal (2010)

Community newsletter: Centennial Mandalong Mine Southern Extension Project, June 2010.

DECCW (2010)

Wallarah 2 Coal Project (07_0160) Environmental Assessment, Submission to Department of Planning, 15 June 2010.

Department of Planning (2008)

Impacts of Potential Underground Coal Mining in the Wyong Local Government Area. Strategic Review, NSW Department of Planning, 2008.

DPI (2005)

DPI – Mineral Resources Assessment Report: Northern Geosciences (Draft) Report on Hydrogeological Investigations Dooralong & Yarramalong Valleys, GS2005/065, 28 March 2005.

Kalf and Associates Pty Ltd (2010)

Peer Review of the Mackie Environmental Research Modelling Report, Field Evidence and Stakeholders Comments, report prepared for Wyong Areas Coal Joint Venture, 27 October 2010.

Li, G, Hebblewhite, B, Galvin, J, Gale, W, Hill, D (2005)

Systems Approach to Pillar Design’ Final Report on ACARP Research Project C9018, April 2005.

Middlemis, H, Merrick, N, and Ross, J, (2001)

Groundwater flow modelling guideline, Murray-Darling Basin Commission, Project No. 125, Final Guideline – Issue 1, January 2001.

MSEC and SCT (2010).

Wallarah 2 Coal Project Subsidence Modelling Study Appendix A to the EA, February 2010.

30

NSW Office of Water (2010) MP07_0160-Wallarah No.2 underground coal project, Submission to Department of Planning, 17 June 2010.

Pells Sullivan Meynink (2010)

Report PSM1105.TR1 Rev B, Submission on behalf of Wyong Shire Council, 27 May 2010

Sinclair Knight Merz, 2010

Wyong Water Study: Assessment and Documentation of Current Groundwater and Surface Water Information - Wyong, report prepared for the NSW Department of Planning, August 2010.

Wardell, K (1975)

Mining Under Tidal Waters. Report to the Ministry for Mines and Power, NSW Government. Wardell and Partners.

WACJV(2010a) Wyong Areas Coal Joint Venture Responses to First Set of PAC Panel Questions. Staged responses in period circa 26/9/10 to 21/10/10

WACJV (2010b) Wyong Areas Coal Joint Venture Response to EA Submissions. Report to the Department of Planning, 28 September 2010.

WACJV (2010c) Geology Wyong Areas Coal Joint Venture Response, 20 September 2010

WACJV (2010d) Wyong Areas Coal Joint Venture Email and Strata Control Technology Report No. COA1671. 26 October 2010.

WACJV (2010e)

Wyong Areas Coal Joint Venture. Clarification on Previous Responses to PAC Panel Questions. 1 November 2010.

Waddington, A.A. & Kay, D.R (2002)

Management Information Handbook on the undermining of Cliffs, Gorges and River Systems. ACARP Research Projects Nos. C8005 and C9067, September 2002

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APPENDIX H

CENTRAL COAST WATER SUPPLY & SURFACE WATER ISSUES

H.1. INTRODUCTION

H.1.1. Submissions

Numerous submissions express concerns about the potential impact of the Wallarah 2 Coal Project (W2CP) on the Gosford-Wyong Joint Water Supply. For example, the submission from the Water Authority notes that:

The Wyong River and Jilliby Jilliby Creek catchments (Yarramalong and Dooralong Valleys) provide approximately 48% of the catchment area and annual stream flows.

and,

The water resources on the Central Coast are extremely limited and are fully committed to meeting the water demands of a rapidly growing area. It is essential that these limited resources are protected.1

The Water Authority submission concludes:

Given the significant contributions that Wyong River and Jilliby Jilliby Creek makes to the water supply and the level of uncertainty surrounding the impacts of the proposal on the groundwater and streamflows, this presents an unacceptably high level of risk to the Central Coast Water Supply system and the GWCWA calls for the proposal to be rejected.2

This view is echoed by Gosford Council with reference to the submissions from Wyong Shire Council and the Water Authority:

These submissions highlighted that the Central Coast water supply is highly dependent on the stream flows and water quality in Wyong River and its tributary Jilliby Creek. Further it was concluded that there are shortcomings in the proponent’s groundwater and surface water assessments and that any activity which puts at risk the quantity and quality of this source could have significant consequences for the community.3

Because of the severe water supply shortages in recent years, any potential threat to the supply as a result of mining is of significant concern to the community. As noted previously, numerous submissions in relation to the EA for the W2CP re-stated the concerns originally expressed in submissions to the Wyong Strategic Review, that the project posed an unacceptable threat to the water supply for the Central Coast which is operated by the Gosford-Wyong Councils Water Authority (the Water Authority). The issue is also taken up in the submission from the NSW Office of Water:

1 Submission by Gosford Wyong Councils’ Water Authority, 2 June 2010, page 1 2 Submission by Gosford Wyong Councils’ Water Authority, 2 June 2010, page 4 3 Submission from Gosford Shire Council, 1 June 2010

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It is critical the EA demonstrates that mining subsidence will not interrupt surface flows in either Jilliby Jilliby Creek of the Wyong River, nor lead to impacts upon Available Water Determinations or local impact triggers, including cease to pump triggers on either river system.

A range of statistics have been put forward relating to the importance of Jilliby Jilliby Creek to the Central Coast water supply. The EA contains the following statements4:

The water extracted from the Lower Wyong River Weir . . . . . . constitutes approximately 30% of the combined Central Coast Water Supply. The average river flow contribution from the Jilliby Jilliby Creek system to the Lower Wyong River Weir is approximately 37%. The remaining 63% contribution is from the Wyong River system. That is, the Jilliby Jilliby Creek contribution equates to about 11% of the total Central Coast water supply.

This assessment contrasts with the assessment provided by the Water Authority5:

Flows entering the Lower Wyong weir constitute approximately 48% of the total stream flows available for extraction for the water supply. Of these flows, approximately 28% is contributed by the Jilliby Jilliby Creek sub catchment. Therefore 13% of the total flows available for water supply are from the Jilliby Jilliby Creek sub-catchment and 35% of total flows available from the Wyong River Catchment (excluding Jilliby Jilliby flows).

Unfortunately neither the EA nor the Water Authority have provided any supporting details of the source of the statistics quoted. Notwithstanding, it appears that the contribution of Jilliby Jilliby Creek flow to the Central Coast water supply is of the order of 11-13%

H.1.2. Key Issues

In assessing the question of the potential impact of the W2CP on the Central Coast Water Supply and surface water resources in general, the Commission has considered five inter-related questions:

1. What is the relative importance of the flow from Jilliby Jilliby Creek to the overall water supply for the Central Coast, now and in the future?

2. What proportion of the Jilliby Jillaby Creek catchment area will be subject to subsidence that might lead to a reduction in surface runoff to the creek system?

3. What are the physical processes that might lead to a loss of surface runoff, how likely are they to occur and what is the level of certainty associated with the predictions?

4 EA Section 7.6.1 5 Submission from GWCWA dated 2 June 2010.

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4. What sections of the creek system will be subject to subsidence that might lead to loss of water from the creek either by direct flow into rock in the bed of the creek or loss of water from an alluvial aquifer connected to the creek system?

5. What are the physical processes that could lead to sufficient cracking of the rock to cause loss of water direct from the creek bed or from a connected alluvial aquifer, how likely is it that these could occur on a significant scale and what is the level of certainty associated with the predictions?

H.1.3. Structure

Notwithstanding the fact that potential impact on the Central Coast water supply was identified as a significant issue during the Wyong Strategic Review, neither the EA nor any of submissions from agencies or the community provide a comprehensive overview of the Central Coast water resources to support the case that the W2CP may, or may not, have a significant effect on the Central Coast water supply. Although the W2CP will mainly affect the catchment of Jilliby Jilliby Creek, the other river systems that contribute to the Central Coast water supply, particularly Wyong River and Ourimbah Creek, need to be considered in order to provide a context in which to assess the overall relevance of Jilliby Jilliby Creek to the Central Coast water supply system. In order to provide a sound basis for assessing the potential impacts of the W2CP on the water supply for the Central Coast, a summary of the key aspects of the water supply system has been prepared (see Section H.4) based on information provided in the WaterPlan 2050 Options Report6 prepared by the Water Authority together with catchment characteristics and flow data available from the Pinneena database7 and the Wyong Water Study. This appendix provides an overview of the current and future status of the Central Coast water supply system, including:

A general introduction to the surface water issues including an overview of the runoff characteristics of the main water supply catchments - see Section H.2;

An overview of the water resources of the Central Coast and the relative importance of Jilliby Jilliby Creek – see Section H.3;

An overview of the operation of the Central Coast water supply system including proposals for improvements to the water supply system as set out in the WaterPlan 2050 and the relevant provisions of the Water Sharing Plans as they affect access to water to meet the water demands of the Central Coast –see Section H.4.

6 WaterPlan 2050 Options Report for the Long Term Water Supply Strategy, GWCWA, July 2007 7 Pinneena database V9 NSW Office of Water, 2010

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In addition, this appendix provides an assessment of:

Section H.5 assesses the potential impacts of the W2CP on runoff and flow in Jilliby Jilliby Creek and its contributing sub-catchments;

Section H.6 provides an assessment of the potential impacts of the mine on the geomorphology of the creeks and floodplains and the consequences for aquatic ecosystems; and

Section H.7 provides an assessment of water quality in the various streams of relevance.

H.2. HYDROLOGIC PROCESSES

While it is common to consider surface water and groundwater as existing in different regimes, in practice the distinction is blurred by the interchange between the two. Rainfall on a catchment can enter a creek directly as surface runoff or infiltrate the shallow groundwater aquifer system and emerge as baseflow in the stream over a much longer period. An example of the delay in water permeating through shallow aquifers can be seen in the seeps that occur on sandstone slopes for days and weeks after rainfall. This mechanism is responsible for the fact that, in dry times, almost all stream flow is baseflow derived from the shallow groundwater aquifers. In addition to the water that re-emerges as baseflow in the creeks, some of the water that infiltrates into the ground or occurs as shallow groundwater can permeate very slowly down to the deeper aquifers from where it will make very limited contribution to creek flow. In common with all catchments in Australia, it is the extremes of flow patterns (floods and droughts) that are of greatest concern to the community, particularly in the face of a project that might alter the flow characteristics at these extremes. As noted above, there is a strong interconnection between surface runoff and shallow groundwater regimes which contribute to flow in the creeks and rivers. For convenience it is useful to consider flow in a creek or river as derived primarily from one of two sources:

“Surface runoff”, which, as the term indicates, relates to flow of water across the surface of the land. Surface runoff is not, however, a process that occurs uniformly across a catchment. Some areas, particularly rock outcrops and wetter areas near to the creeks will tend to produce significantly more surface runoff than, say areas of deep sandy soils in which all rainfall will infiltrate unless the rainfall is particularly heavy or prolonged. Because surface runoff is a direct result of rainfall, surface runoff will cease shortly after rainfall ceases, with some time delay as surface runoff from the remotest part of the catchment travels through the creek system to the outlet. As is self evident, surface runoff characteristics of a catchment are heavily dependent on a range of physical characteristics including topography, geology, soils and vegetation.

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“Baseflow” is the term that is used to loosely describe the contribution to flow in a creek from the shallow groundwater system. Typically, baseflow contribution will increase as the shallow groundwater system is recharged as a result of a rainfall event, and will persist for a long time after surface runoff has ceased. The persistence of baseflow and its contribution to the total flow at a particular location are a function of the location at which flow is observed. In steep headwaters creeks, any baseflow contribution may only persist for a day or so, after which the creek will remain dry until the next rainfall event. At lower elevations, particularly where the creek channel runs through alluvial deposits, baseflow may persist for many months.

The separate contributions from surface runoff and baseflow can be estimated by careful analysis of the shape of the flow hydrograph using a variety of analytical techniques. An example of a simple separation technique using purely mathematical techniques is illustrated in Figure H.1 which has been taken from the Wyong Water Study8.

(Source: Figure 4.6 in the Wyong Water Study)

Figure H.1 Estimated Separation of Baseflow for Jilliby Jilliby Creek for 2008

Note that the vertical axis in Figure H.1 is a logarithmic scale which tends to give the incorrect impression that baseflow is a very large proportion of the total flow. In this case the total annual flow was about 35,600 ML while the baseflow component was about 5,300 ML, or 15% of the total. Although the purely mathematical analysis used to derive Figure H.1 will tend to give an upper limit to the proportion of baseflow, the figure illustrates the fact that, for a catchment the size of Jilliby Jilliby Creek, there will be significant periods when all the flow in the creek will comprise baseflow.

8 Wyong Water Study: Assessment and Documentation of Current Groundwater and Surface Water Information – Wyong, Report prepared for NSW Department of Planning by SKM, August 2010

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In addition to making the distinction between surface runoff and baseflow, two other important processes need to be considered in relation to the flow regime in a creek or river:

While some reaches of a stream will contribute to baseflow, the converse will occur in other reaches and, rather than ‘gaining’ these reaches will be ‘losing’. This ‘losing’ process by seepage from the bed of a stream into the surrounding ground is particularly common along downstream sections of a river or creek. In the extreme case, such as some rivers in the arid zone, all the flow is lost and the creek eventually looses definition.

During times of flood, two competing processes occur as the flood wave progresses downstream. Additional flow from other tributaries will tend to increase the peak flow. However the natural attenuation processes associated with temporary storage of floodwater on the floodplain work to reduce the peak flow. The attenuation of a flood is an important aspect of flood behavior that needs to be taken into account in assessing flood impacts on areas with wide floodplains, such as the Dooralong Valley.

As is evident from the restrictions on the availability of surface water during the recent drought, surface runoff is a highly variable phenomenon at all time scales. In the short term, the flow rate in a stream is directly impacted by rainfall on the catchment. At longer timescales the total volume of runoff available from a catchment is a function of climatic cycles, which are characteristically high variable in Australia. This variability of climate means that it is often difficult to distinguish the effects on runoff of climate from those that might be attributable to changes on the landscape including changes in vegetation cover, construction of farm dams or subsidence.

H.3. WATER RESOURCES OF THE CENTRAL COAST

H.3.1. Overview

Table H.1 summarises the catchment areas and estimated average annual flow for the major creeks and rivers that contribute to the Central Coast water supply. These data are drawn from two sources:

Estimates prepared for the Gosford Wyong Councils’ Water Authority using modelled streamflow based on historic climate records (1885 – 2006) and observed rainfall: runoff characteristics of each catchment9;

Data extracted from the Pinneena database10 of flow records published by the NSW Office of Water based on a period when there are relatively complete records at each of the three gauging stations (June 1977 – July 2009).

9 Table 9.1 of Water Plan 2050: Options Report for the Long Term Water Supply Strategy, GWCWA 2007. 10 Pinneena CD, V9.3, NSW Office of Water 2010

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Because the two sets of data have been derived by different methods and refer to different lengths of record, the last two columns of Table H.1 provide a comparison between the different catchments in terms of ML/km2/year. On the basis of runoff per square kilometre, the simulated data for the period 1885 to 2006 are approximately 16% higher than the historic data for the period 1977/8 to 2007/8. The reasons for this difference are not immediately apparent and could be an artefact of the modelling or because of the relatively low rainfall in the period used for the historic analysis.

Table H.1: Estimated Average Annual Flows for Central Coast Catchments

Catchment Catchment Area (km2)

Average Annual Flow (ML/year)

Average Annual Flow (ML/km2/year)

1885 - 20061

1977/8-2008/9

1885 - 20061

1977/8-2008/9

Wyong River @ Gracemere (211009)

236 47,800 202

Jilliby Jilliby Creek @Durren Lane (211010)

92 18,010 196

Wyong River @ Weir 355 84,500 238

Ourimbah Creek @ U/SWeir (211013)

83 26,400 21,430 300 258

Mooney Dam 39 16,800 431

Mangrove Creek Dam 101 18,600 184

Mangrove Creek Weir (ex Mangrove Creek Dam)

241 30,000 124

Total Central Coast 176,300

The creeks and rivers of relevance to this review drain from the ridges of the Wattagan Mountains. In the upper reaches all the creeks are deeply incised and have only short lengths of first order streams that join to form second order streams within a few hundred metres. In contrast, the lower reaches of the catchments within Wyong Shire (Wyong Shire Wyong River, Jilliby Jilliby Creek and Ourimbah Creek) are characterised by wide relatively flat alluvial floodplains in which the channel meanders in a manner that is characteristic of watercourses that have very flat longitudinal grade. Despite the general similarities, the main catchments in the Wyong Shire have a number of distinct differences in topography and geology. Both Wyong River and Ourimbah Creek are bounded on to both the east and west by steep hills with deeply incised tributary creeks whereas Jilliby Jilliby Creek has predominantly lower slopes on its eastern side. Some of the main geological differences, which are reflected in the soils, land use and runoff characteristics are summarised in Table H.2. In particular it is noticeable that Wyong River and Ourimbah Creek have significant areas of permeable Hawkesbury sandstone, predominantly located on Somersby Plateau, which contains large areas of highly permeable sandstone; a significant groundwater resource.

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The data in Table H.1 shows that the average annual total surface water resources of the Central Coat catchments amount to about 176,300 ML/year of which Jilliby Jilliby Creek accounts for about 10%. Within the upland catchment area within the Jilliby Jilliby Creek catchment, approximately 16% is proposed to be undermined by the W2CP.

Table H.2: Catchment Characteristics

Attribute Wyong River @ Gracemere

(211009)

Jilliby Jilliby Creek @Durren Lane

(211010)

Ourimbah Creek@ U/SWeir

(211013)

Catchment Area (km2) 236 92 83

Hawkesbury Sandstone (%) 15% 5% 30%

Narrabeen Group (%) 80% 80% 65%

Alluvium(%) 5% 15% 5%

(Source: Percentage areas estimated from Map 3 of the Wyong Strategic Review) The differences in topography and geology lead to significant differences in runoff characteristics from these three catchments. These differences are illustrated in Figure H.2 which shows flow duration graphs for the three streams in terms of the runoff per unit area (expressed as a depth of runoff in mm per day). The data used to derive Figure H.2 is the same as that used to derive the statistics for the period 1977/8 to 2008/9 quoted in Table H.1.

Figure H.2: Flow Duration Curves for Wyong River (211009), Jilliby Jilliby Creek (211010) and Ourimbah Creek (211013)

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The graphs in Figure H.2 show that Ourimbah Creek (211013) and Wyong River (211009) have similar runoff characteristics, but that Jilliby Jilliby Creek yields significantly less runoff per unit area for 90% of the time and has significant periods (more than 10% of the time) when the creek almost ceases to flow (less than 0.001 mm/day). The greater persistence of flow for Ourimbah Creek and Wyong River shown in Figure H.2 is consistent with the analysis presented in the Wyong Water Study11 in which the baseflow component of Wyong River at Gracemere (211009) was assessed as about 28% of total flow compared to 17% for Jilliby Jilliby Creek at Durren Lane. Although the analysis for the data in Figure H.2 has been undertaken only for the three main streams in Wyong Shire that have relatively large catchment areas, the runoff characteristics of the smaller catchments of relevance to the W2CP (Hue Hue Creek, Buttonderry Creek and Wallarah Creek) can be expected to reflect even lower runoff characteristics and be more ephemeral than Jilliby Jilliby Creek. Table H.3 provides a summary of other flow statistics for the three main catchments that are located within Wyong Shire and contribute to the Central Coast water supply. Three important aspects of these statistics should be noted in relation to the availability of water for various users:

The flow statistics quoted in Table H.3 have been derived from historic data published by the NSW Office of Water12. In order to align with the entitlements set out in the various Water Sharing Plans (see Section H.4.3), the data used for the analysis in Table H.3 is based on a “water year” commencing on 1st July and only includes those years that have complete records. The data in Table H.3 may, therefore, differ slightly form data quoted in other sources, but provides a useful indication of the relative surface water resources of each catchment.

The data in Table H.3 is taken from the relevant flow gauges on each of the streams. On the whole these gauges are located downstream of licensed surface water extraction points (shown as dark blue dots in Figure H.3 and extraction for stock and domestic purposes. (The exception to this is a cluster of surface water licensed extractions on the Wyong River downstream of the Gracemere gauging station.) Because the flow statistics in Table H.3 relate to a point downstream of the majority of licensed extractions they under-state the total available surface water resources.

Water from Mangrove Creek Dam can be released into the Wyong River via the Boomerang Creek tunnel. Data supplied by the Water Authority13 indicates that since 1993 the average has been 1,279 ML/year with a maximum of 5,934 ML in 1994. Since 2005 negligible flow has been diverted. Because this data has only been provided for the period since 1993 and any transfers are subject to losses between the outlet and near Yarramalong and the flow gauge at Gracemere, it has not been taken into account in the statistics in Table H.3.

11 Wyong Water Study, SKM June 2010 12 Pineena V9.3, NSW Office of Water, 2010 13 Headworks Boomerang Tunnel transfers.xls, spreadsheet provided by GWCWA, 3/11/2010

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Table H.3: Recorded Runoff Statistics 1977/8 to 2008/9

Statistic Wyong River @ Gracemere

(211009)

Jilliby Jilliby Creek@Durren Lane

(211010)

Ourimbah Creek@ U/SWeir

(211013)

Average (ML/year) 47,800 18,010 21,430

10th Percentile (ML/year) 9,775 2,770 4,660

Median (ML/year) 36,390 13,385 19,135

90th Percentile (ML/year) 99,830 34,370 37,070

Source: Figure 3 of Hydromorphology Study

Figure H.3: Location of Surface Water Extraction Licences and Groundwater Bores14

14 Source: Figure 3 of Hydromorphology Study – Appendix C of EA for W2CP

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H.4. THE CENTRAL COAST WATER SUPPLY SYSTEM

H.4.1. Overview

In 1975, Gosford and Wyong Councils integrated their pre-existing individual water supply schemes and resolved to augment the supply based on harvesting water from Wyong River and Mangrove, Mooney Mooney and Ourimbah Creeks. The Councils also agreed to the construction of Mangrove Creek Dam (190,000 ML) which was commissioned in 1980. Prior to 1975, Gosford’s water supply scheme was based on Mangrove Creek Weir (on the lower reaches of Mangrove Creek) and Mooney Dam, which is located on the upper reaches of Mooney Mooney Creek. Water could be transferred from either of these two sources for treatment before distribution through to the Gosford community. Wyong’s water supply scheme was based on a weir and pumping station on the lower Wyong River which transferred water to Mardi Dam (an off river storage) from where it was and distributed to the Wyong community following treatment. Prior to construction of Mangrove Creek Dam, a common feature of both these schemes was a heavy reliance on ‘run of river’ flow, with the total volume of storage, as set out in Table H.4 (12,600 ML), being less than about 6 months’ supply for the Central Coast which typically requires about 30,000 ML/year.

Table H.4: Central Coast Water Storage Capacity as at 1975

Storage Location Volume (ML)

Mardi Dam 7,400

Mooney Dam 4,600

Wyong River Weir 300

Mangrove Creek Weir 300

Following the formation of the Gosford Wyong Councils’ Water Authority (the water Authority), in addition to construction of Mangrove Creek Dam, a number of minor enhancements to the water supply system were implemented in the late 1980s including:

Construction of the Boomerang Creek tunnel to allow water from Mangrove Creek Dam to be directed into the Wyong River when dam storage level exceeds about 20%;

Supplementing the supply to Mardi Dam by construction of a weir on Ourimbah Creek (approximately 100 ML storage) with a pump station and pipeline;

Construction of a pipeline linking the Gosford and Wyong water supply systems.

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Without under-stating the impact of the restrictions on water supply to the communities in the Central Coast during the drought years of 2002/3 to 2005/6, it should be noted that the water supply situation has altered significantly since 2007 when a number of interim upgrade works and drought contingency measures were undertaken including:

Upgrading the Wyong River pump station from 72 ML/day to about 100 ML/day;

Increasing the capacity of the transfer system to Mardi Water Treatment Plant from 100 ML/day to 240 ML/day;

Constructing a 160 ML/day pump system to increase the capacity to transfer water to the Gosford reticulation system;

Progressive imposition of water restrictions commencing in February 2002;

Construction of a pipeline capable of conveying 33 ML/day from (or to) the Hunter Water system;

Construction of a temporary weir and pipeline to transfer up to 12 ML/day from the Porters Creek Wetlands.

Table H.4 shows the volume of water supplied to the Central Coast since 1993. The graph shows a slight upward trend between 1993 and 2001 after which there was a progressive reduction until 2007 reflecting increasing stringent water restrictions. The years 2007 and 2008 show a slight increase in the volume of water supplied as restrictions were relaxed.

Source: Data supplied by GWCWA15

Figure H.4: Water Supplied to the Central Coast Since 1993

15 Headworks Boomerang Tunnel transfers.xls, spreadsheet provided by GWCWA, 3/11/2010

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Figure H.5 shows the water held in the Central Coast water supply storages over the period 1993 to 20010 expressed as a percentage of the capacity of the storages. The key aspect of Figure H.5 is that it illustrates the dominance of the Mangrove Creek Dam (190,000 ML capacity) compared to the other Central Coast storages (12,600 ML – see Table H.4. The dominance of Mangrove Creek Dam (which constitutes 94% of the capacity within the Central Coast water supply system) is shown by the fact that the total water storage within the system (green line in Figure H.5) follows the trend of Mangrove Creek Dam, regardless of the volume held in the other storages.

Source: Data supplied by GWCWA16

Figure H.5: Variation in Water Storage Expressed as a Percentage of Capacity

As shown by the data in Table H.1, the catchment area of Mangrove Creek Dam is only 101 km2 and the storage (190,000 ML) would take 10 years to fill on the basis of the average annual flow (18,600 ML/year) without any extractions for supply to the Central Coast. The fact that the Central Coast water supply system has a relatively small catchment that provides runoff to its main storage, has meant that the system was particularly vulnerable to climatic cycles. This is illustrated by Figure H.6 which shows the modelled streamflows for the Central Coast water supply catchments based on climate records from 1885 to 2006. The main points to note are that, in common with the experience in many parts of Australia, there have been long term climatic fluctuations that are reflected in the flow in the rivers and creeks:

The period from about 1900 to 1950 was a relatively dry period that extended for several decades;

16 Headworks Boomerang Tunnel transfers.xls, spreadsheet provided by GWCWA, 3/11/2010

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Commencing with the floods of 1949/50 the east coast of Australia experienced a relatively wet period until about 1991;

Since 1991, rainfall and streamflow has been significantly less than the long term average.

The wet period in the late 1980s provided streamflow that contributed a significant volume to Mangrove Creek Dam, but the relatively dry period since 1991 have led to the gradual decline in the volume held in the dam as shown in Figure H.5.

Source: WaterPlan 205017

Figure H.6: Modelled Central Coast Streamflows 1885 - 2006

H.4.2. WaterPlan 2050

In mid 2007 a long term strategic water supply plan, WaterPlan 2050, was adopted by Gosford and Wyong Councils. The plan provides for a population increase of about 100,000 to around 465,000 by 2050 and also takes account of changes in access to water imposed under the Water Sharing Plan for the Central Coast Unregulated Water Sources 20009 (see Section H.4.3 below). The essence of the WaterPlan 2050 is summarised in Figure H.7 which shows three stages of projected increase in the yield of the Central Coast water supply:

1. Completion of “Base Case” comprising the interim upgrade works and drought contingency measures listed in Section H.4 above. These works, which have already been completed, are expected to increase the yield of the system from about 31,000 ML/year to 40,000 ML/year and be capable of meeting expected demand until about 2027;

2. Completion of the pipeline linking Mardi Dam to Mangrove Creek Dam and associated upgrading of the transfer system from the Wyong Weir (scheduled for completion by June 2011). These works are expected to increase the yield

17 WaterPlan 2050, p2

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of the system from about 40,000 ML/year to 45,600 ML/year and to be capable of meeting expected demand until 2045;

3. Installation of spillway gates on Mangrove Creek Dam to increase storage capacity from 190,000 ML to 230,000 ML. These works are expected to increase the yield of the system from about 45,600 ML/year to 50,000 ML/year which would be capable of meeting expected demand until after 2050.

Source: WaterPlan 2050, p10

Figure H.7: Projected Growth in Water Supply Demand and Yield from the Central Coast Water Supply System to 206018

In addition to the major engineering works, WaterPlan 2050 includes strategies to:

Further reduce water demand by encouraging water use efficiency in both domestic and commercial premises;

Assess new resources including retrofitting of rainwater tanks, further use of groundwater as a reserve, upgrading the existing pipeline link to the Hunter Water network and possible access to water from the proposed Tillegrah Dam via the Hunter Water supply network.

Notwithstanding the fact that the various upgrades to the Central Coast water supply system are expected to provide significant improvements to the available average yield, the full benefit of these upgrades will not occur until the volume in Mangrove Creek Dam is increased to at least 40% (currently at 27.5% capacity - September 2010). For this reason the Water Sharing Plan19 includes provisions that allow additional extraction of water until the combined Central Coast water storages reach 60% capacity for the first time (see Section H.4.3 below).

18 WaterPlan 2050, Adopted by Gosford and Wyong Councils, August 2007 19 Water Sharing Plan for the Central Coast Unregulated Water Sources 2009

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As can be seen from Figure H.7, the pipeline linking Mardi Dam to Mangrove Creek Dam pipeline is a key component of the WaterPlan 2050. As illustrated by Figure H.5, a major problem in the past has been the ability of the system to store water for supply at times of low flow from the catchments, rather than overall access to surface water resources. As noted previously, Mangrove Creek Dam which has an existing storage capacity equivalent to over 5 years’ supply for the Central Coast at current demand, has only a relatively small catchment (about 101 km2 – a little bigger that the catchment of Jilliby Jilliby Creek). As a consequence of its small catchment, the Mangrove Creek Dam has not been used to its full potential. As shown in Figure H.5, since 1993 the dam has averaged less than 40% capacity and has been a maximum of only 69% full. The pipeline from Mardi Dam to Mangrove Creek Dam will allow the Water Authority to use Mangrove Creek Dam to store for water extracted from Wyong River and Ourimbah Creek. The pipeline will also reduce the water losses that are currently occur when water is released from Mangrove Creek Dam into the Wyong River about 20 km upstream of the Wong Weir - from which it is pumped into Mardi Dam for transfer into the reticulated water supply system for the Central Coast. In the context of Figure H.7, some of the claims made in submissions concerning the degree of stress suffered by the Central Coast water supply would appear to relate to the situation that existed in the drought of 2002/3 to 2005/6 rather than to the situation following the completed interim works and the construction of the Mardi Dam to Mangrove Creek Dam pipeline and associated increase in the capacity of the pump at the Wyong Weir.

H.4.3. Water Sharing Plans and Access to Water

Any consideration of potential threats to security of water supply to the Central Coast, must take account of the integrated nature of the Central Coast water system which, as described above, takes water from a variety of sources including:

Mangrove Creek and Mooney Mooney Creek which drain to the Hawkesbury River,

Ourimbah Creek, Wyong River and Jilliby Jilliby Creek which drain to Tuggerah Lake.

Rules for access to the surface water resources of these sources, is governed by a series of water sharing plans (WSPs) that have been implemented since 2003:

Jilliby Jilliby Creek WSP (2003 – updated 24 July 2009)

Ourimbah Creek WSP (2003 – updated 24 July 2009)

Kulnura Mangrove Mountain Groundwater Sources WSP (2003 – updated 20 June 2006)

Central Coast Unregulated Water Sources WSP (2009 – updated 8 January 2010)

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In general, each plan is due for review about 10 years after its original implementation. In addition, because the Water Authority draws its water from catchments that are covered by these plans, all the plans cross reference the rules governing access for bulk water supply for the Water Authority as well as access rules for stock and domestic purposes and licensed extraction within the area covered by each plan. Each plan provides rules for various aspects of access by various users including such things as flow regimes for different classes of licenses, a daily extraction limit for each user, a maximum daily extraction limit for all users within a WSP area and the annual extraction limit for each user within each WSP area. The share of the available resource that is available to each entitlement holder is specified either as a volumetric unit (ML) or as a share of the total extraction limit. In order to provide a simple overview of the distribution of surface water access between different users and across different rivers/creeks, all annual licensed extraction limits are expressed as ML/year in Table H.5.

Table H.5: Summary of Water Access Licences Under 2009 WSP Provisions

Source Stock & Domestic

(ML/year)

Licensed Extraction (ML/year)

Water Authority (ML/year)

Wyong River 31.9 3,984 34,600

Jilliby Jilliby Creek ±186 1,016

Ourimbah Creek ±509 6,529 8,400

Mangrove Creek 87.0 4,260 47,900

Mooney Mooney Creek 63.5 2,215 17,900

Note that, although the access entitlements from individual sources for the Water Authority total 108,800 ML/year, the water sharing plans currently limit the total for the Water Authority to 36,750 ML/year from all sources including Mangrove Creek, Mooney Mooney Creek, Ourimbah Creek, Wyong River, groundwater sources and bulk transfers from Hunter Water. The extraction limit for the Water Authority is scheduled to be reviewed on 1 July 2013 or after releases commence from Tillegrah Dam, whichever occurs first. In view of the fact that Figure H.7 indicates that, following completion of the Mardi Dam to Mangrove Creek Dam the capacity of the Central coast water supply system will be about 46,500 ML/year, additional water access entitlements will subsequently be required in order to allow the Water Authority to supply water up to the capacity limit of the system. (It should also be noted that the limit for supply from Mangrove Creek is about 40% greater than that from Wyong River and Jilliby Jilliby Creek combined. This refers to water extracted from Mangrove Creek Weir as well as from Mangrove Creek Dam.) A further feature of the access rules in the various WSP is that there is provision for “carry over” until the next year of a proportion of the licence entitlement. These “carry over” limits are:

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Licensed extractions 100%;

Water Authority 30% from the Wyong River source.

The ability of the Water Authority to carry over up to 30% of its Wyong River entitlement from one year to the next, together with the improved use of Mangrove Creek Dam, provides a further means of maintaining continuity of water supply to the Central Coast. In addition to the annual extraction limits outlined above, the Water Sharing Plan provides a complex set of rules for progressive implementation of restrictions on pumping from the Wyong River which are linked to completion of the fish-way and upgrading of the pumping system at the Wyong Weir (see Table H.6) and the total volume held in the Water Authority storages (see Table H.7).

Table H.6: Wyong River Flow Classes Applicable to the Water Authority

Class Conditions Flow1

Very Low

First 3 years of plan (ie until August 2012) or until Wyong fish-way and pump station upgrade complete

Nil

Thereafter – combined flow at Stations 21009 and 21010 <4 ML/day

A

First 3 years of plan (ie until August 2012) or until Wyong fish-way and pump station upgrade complete

Nil

Thereafter – combined flow at Stations 21009 and 21010 4 – 13.5 ML/day

B

First 5 years of plan (ie until August 2014) or until Wyong fish-way and pump station upgrade complete

Nil

Thereafter – combined flow at Stations 21009 and 21010 13.5 - 26 ML/day

C

First 5 years of plan (ie until August 2014) or until Wyong fish-way and pump station upgrade complete

Nil

Thereafter – combined flow at Stations 21009 and 21010 >26 ML/day

Note 1. Flow defined as the combined flow of Wyong River @ Gracemere (211009) and Jilliby Jilliby Creek @ Durren Lane (211010)

Table H.7: Permitted Pumping for the Wyong River

Flow Class

Until Total Storage Reaches 60% Capacity

for the First Time

Following Total Storage Reaching 60% Capacity

for the First Time Storages < 50%

Storages 50% - 60%

Storages < 40%

Storages 40% - 60%

Storages > 60%

A 100%2 80% 80% 80% 0%

B 100% 80% 80% 80% 60%

C 100% 80% 80% 80% 60%

Note 1. Controls applicable after Year 6 of Plan or completion of upgrade works whichever occurs first

Note 2. Percentage refers to the “percentage of remaining flow in the river”, but the Plan allows for subsequent amendment to “percentage of remaining flow in the river in excess of the lower limit of the flow class”.

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Figure H.8 graphically illustrates the implications of the rules summarised in Table H.6 and Table H.7 for the ‘worst case’ situation in which the storages are more than 60% full and the amount that can be extracted from the Wyong River is restricted to the percentage of remaining flow in the river in excess of the lower limit of the flow class. In particular it shows that, compared to pre-existing conditions for access to water from the Wyong River, the Water Sharing Plan imposes restrictions on access for about 80% of the time, but allows significantly increased access for the high flow range that represents the remaining 20%. It should be noted that Figure H.8 specifically refers to changes in access to water from the Wyong River. The Water Sharing Plan does not significantly alter access arrangements to the other sources which constitute 68% of the potentially available resource (see Table H.5).

Source: Figure 7-1 of WaterPlan 2050 Options Report

Figure H.8: Wyong River - Current and Potential Water Access

The ‘worst case’ assumptions illustrated in Figure H.8 appears to have been used in the analysis of the supply reliability set out in the WaterPlan 2050 Options Report. In this regard, the analysis appears conservative in its assessment of the water supply available to meet the future water requirements of the Central Coast.

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H.4.4. Water Demand for Mine Operations

The EA (Section 2.12) outlines the proposals for management of water generated by the mine (from surface and groundwater) as well as the water requirements for mine operations and staff amenity. In regard to the details of the requirements for water supply the EA contemplates that, although the mine will produce an excess of water from underground in the medium to long term, it will require external supplies in the start-up phase:

However, the final design and operation of the water management system will be influenced by, among other things, the availability of the mine to be serviced from and integrated with the regional potable water supply system and the regional sewerage system. (EA, page 2-48).

Assessment of the site water balance requirements indicates the site will be in water deficit during the first production year (refer Table 2.7). The deficit is attributable to water requirements for operation of the longwall. This deficit will progressively reduce over the next five production years as mine seepage water make (supply) from underground increases as mining progresses. To make up the initial deficit, a combination of separately imported potable water and sewage treatment plant recycled water will be sourced from external suppliers. (EA, page 2-60).

The site water management and treatment systems are discussed in further detail in Appendix I. For now it is sufficient to note that water requirements for both sites are expected to peak at 500 ML in the first year of operation and to reduce to about 420 ML/year from Year 5 onwards. Approximately 210 ML/ year is expected to be obtained from runoff, but this is likely to be highly variable. As the mine develops, groundwater inflow is expected to increase leading to an excess of water from Year 5 onwards. The EA contemplates that the shortfall of water for the operations will be met by a combination of potable supply and treated sewage effluent from the Charmhaven treatment plant. The Commission considers that either of these options would be feasible without compromising the Central Coast water supply:

Once the pipeline linking Mardi Dam to Mangrove Creek Dam and associated works are complete, the Central Coast water supply system should have excess capacity to supply up to 15,000 ML/year. Provision of up to 250 ML/year of potable water to the W2CP for up to 5 years should not compromise the available supply to the community.

The Charmhaven sewage treatment plant had an average dry weather flow of about 8 ML/day in 2006 (2,920 ML/year) and this is expected to triple by 2050. Treated effluent is currently discharged to the ocean at Norah Head. This source has the capacity to provide all the water required by the mine even if no groundwater inflow occurred.

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H.4.5. Conclusions Relating to Central Coast Water Supply

The Commission concludes that:

1. The water licenses held by the Water Authority offer considerable flexibility to extract water from different sources and to use “carry over” entitlements of 30% of its annual allocation.

2. The future ability of the Water Authority to provide supply is governed primarily by the water licence access rules and the facilities available to extract, store and distribute the water rather than the available water resource itself.

3. The analysis in the WaterPlan 2020 Options Report indicates that following completion of the pipeline linking Mardi Dam to Mangrove Creek Dam and associated works, the Central Coast water supply system will be capable of supplying 45,600 ML/year (see Figure H.7 which constitutes approximately 26% of the long term average total water resource of the catchments (176,300 ML/year).

4. The EA contemplates that the shortfall of water for the mine operations will be met by a combination of potable supply and treated sewage effluent. Adequate alternatives exist for supply of water for mine operations without compromising the Central Coast water supply even if the predicted groundwater inflows to the mine are not realised.

H.5. POTENTIAL IMPACTS OF LONGWALL MINING

H.5.1. Upland Creeks

For purposes of this aspect of the review a distinction has been drawn between the V shaped valleys within the steep rocky hills and the broad flat alluvial valleys. While it is recognised that there is a gradation between these valley types, these provide a basis for assessing differences in geomorphic character and the likelihood of significant loss of flow. A number of submissions have sought to draw a parallel between creeks in the Southern Coalfield and those in the steep headwaters catchments that will be undermined by the W2CP. In the southern highlands there have been instances where subsidence induced cracking has occurred within the rock that forms the bed of the creek, leading to loss of flow in the creek. As discussed in Appendix F of the Commission’s report, the EA and associated documentation notes differences between the geomorphology of the Southern Coalfield and that associated with the W2CP Project Area, including:

The upland streams in the W2CP Study Area are contained within V-shaped gullies separated by unconfined ridges, in contrast to the Southern Coalfield streams which are contained in more U-shaped gorges cut into a plateau.20

20 WACJV (2010c), p6.

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Rock bars and associated pools typical of the Southern Coalfield do not exist in the upland streams in the proposed W2CP mine area.21

The valleys in the W2CP Study Area are not only much broader than the gorges of the Southern Coalfield but are filled with some 20-30 m of alluvium.22

Streams in the alluvial filled wide valley floors above the proposed longwalls have water levels that are generally above the surrounding groundwater levels and the water levels in these streams are not controlled by a series of exposed rock bars.23

Notwithstanding these differences, the EA focuses most attention on the alluvial valleys and provides limited analysis of subsidence effects on the upland catchment areas that account for about 55% of the total mine footprint. There are scattered acknowledgements in the EA of the potential for upsidence and valley related movement in hilly terrain and along watercourses in this terrain24. However, there is minimal discussion of any associated impacts and environmental consequences. DECCW submitted that:

For some of the smaller creeks little information is provided on their characteristics and the effect of directly undermining them.25

DECCW pointed out that the upper reaches of Little Jilliby Jilliby Creek were 3rd order (in terms of Strahler stream order) and noted subsidence predictions for these reaches. DECCW then provided a number of points of reference as to the significance of these values and the associated impacts that may result,26 concluding that:

The EA is considered deficient in its lack of on-ground survey work over the project area, including a complete lack of description of any significant features (pools, rockbars, alluvium) or aquatic species in the upper reaches of Jilliby Jilliby Creek. Insufficient detail is provided in the flow regime/permanency of water in Little Jilliby Jilliby Creek and the effect longwall mining could have on the permanence of aquatic habitat........27

DECCW also made a number of similar submissions in regard to other streams. WACJV (2010b) has responded that:

All issues raised by DECCW in the adequacy review process were included in the final EA.

and

21 WACJV (2010c), p6. 22 EA, p4-57. 23 EA, Appendix A2, p65. 24 EA, Appendix A2, p29, p45 & p69; WACJV (2010b), p4-21. 25 DECCW (2010a), p1. 26 DECCW (2010a), p6. 27 DECCW (2010a), p7.

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The main creek lines and smaller tributaries have been appropriately assessed. Wyong River, Jilliby Jilliby Creek, Little Jilliby Jilliby Creek, Hue Hue Creek and other smaller tributaries were assessed in the hydrogeomorphic study and the flood study which included the whole flood plain.28

The Commission concurs with DECCW and, at the time, considered the proponent’s treatment of the issues in both the EA and in it responses to DECCW to be lacking sufficient detail. The responses suggested to the Commission that the proponent’s focus was still confined primarily to subsidence impacts on the flood plains. Accordingly, the Commission requested the proponent to ‘characterise the watercourses in the forested areas in the west of the Project Area and provide upsidence and closure predictions for these watercourses’.29 In response, the proponent produced a plan showing the location and hierarchy of streams in the Wallarah 2 Study Area (copy as Figure H.9).30 It was accompanied by a statement that the upland streams are primarily either 1st or 2nd order streams under the Strahler ordering system. The exceptions to this are Little Jilliby Jilliby Creek up to its junction with Splash Gully, and the lower reaches of Myrtle Creek which are both 3rd order streams. The associated plan shows that Little Jilliby Jilliby Creek is a 3rd order stream over the entire Wallarah 2 Study Area and that Armstrong Creek between Little Jilliby Jilliby Creek and LW 6S is 3rd order, although the accompanying text specifically describes it as 2nd order in this area. The proponent’s analysis of stream order has erroneously classified some of the creeks, omitted some all together and misinterprets the relationship between stream order and the underlying geology shown on Figure H.9:

A southern tributary of Calmans Gully is a second order stream and consequently the lower reaches are a third order stream, not second order;

Because lower reaches of Calmans Gully are a third order stream, Little Jilliby Jilliby Creek is a fourth order stream downstream of its junction with Calmans Gully, not a third order stream;

Notwithstanding the fact that the topographic map shows that Creek A and one other do not have defined channels that connect to Hue Hue Creek, the majority of the creek should be classified as third order;

The statement that, “It is important to note that the 3rd order streams roughly correspond with the Patonga Claystone and/or valley alluvium while the steeper 1st and 2nd order streams exist within the relatively erosion-resistant sandstones of the Terrigal Formation.”31 is not consistent with the information in Figure H.9 which shows that much of the length of the 2nd order reaches on Armstrongs Creek, Myrtle Creek, Creek F, Creek G and Creek O are located within an area of Patonga Claystone.

28 WACJV (2010b), p4-2. 29 PAC’s second set of questions to WACJV. 30 WACJV (2010c), Figure 1, p1. 31 WACJV (2010c), page 3

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Source: Figure 1 in WACJV (2010c)

Figure H.9: Regional Geology Showing Stream Order

The proponent also presented new information that draws attention to the difference in the gradient of key major and minor streams in the Wallarah 2 Study Area compared of these with streams in the Southern Coalfield, Figure H.10. The proponent has advised that not one significant rock bar and associated pool was noted in the survey area nor identified from aerial photography (detailed aerial laser survey) of the entire Wyong State Forest.32 This forms the basis for the proponent concluding that the potential for impacts from >200 mm predicted closure criterion is significantly less than that observed in the Southern Coalfield at similar levels of movement.

32 WACJV (2010c), page 4.

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Source: Figure 3 in WACJV (2010c)

Figure H.10: Comparison Between Stream Gradients for the Wallarah 2 Study Area and the Southern Coalfield

It should be noted that Figure H.10 requires careful interpretation. The listed watercourses in the Southern Coalfields are actually higher order than the first and second order streams that have been plotted for the W2CP area, and are therefore only comparable in that the higher order streams in the Southern Coalfields have sections in which the bed of the creek is in rock. While such classification and interpretation issues do not have significant consequences in themselves, they detract from the credibility of the remaining analysis of the status and characteristics of the creeks. Notwithstanding, the Commission concurs with the conclusion that, Consequently the gradient of these 1st and 2nd order streams is such that they are too steep for the rock bars with large associated pools as seen in areas of the Southern Coalfield to form. The proponent has designated by means of a colour overlay, those sections of the streams that are likely to be affected by more than 200 mm of predicted closure but no values of predicted upsidence and closure have been provided as requested by the Commission other those associated with the upper reaches of Little Jilliby Jilliby Creek and Indigenous heritage sites located on Myrtle Creek. In this latest information, the proponent draws the following conclusions:

….there are no specific riverine or riparian ecosystems that rely on pools in streams in the W2CP upland areas. Upland valley areas with their frequent bounder and alluvial-filled, narrow drainage lines provide microclimates.

and In the W2CP area, subsidence related fractures will have no significant impact on the net water flow behaviour of these very steep ephemeral drainage systems which are already adapted to a more stress relived condition in interbedded bedrock units of carried and lesser strength.33

33 WACJV (2010c), page 6.

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The Commission accepts these conclusions as plausible but considers that further investigation is warranted to support them. However, given that mining in most of this region is at least 15 years out, it could be sensible and more effective to defer this investigation until closer to the planned time of mining. The Commission recognises that areas of the Jilliby Jilliby Creek catchment that have the potential to suffer from cracking of the creek channel comprise only 16% of the steep rocky headwaters catchments. The majority of the creeks in this area are first and second order creeks that have ephemeral flow only immediately after rainfall. Accordingly, any creek bed cracking that might occur is unlikely to lead to a significant loss of flow or to have any impact on the water resource available to supply the Central Coast.

H.5.2. Creeks Within the Alluvial Valleys

Unlike the watercourses in the steep rocky headwaters, the creeks in the alluvial valleys are incised into a relatively thick blanket of alluvium. The potential pathway for loss of flow in this part of the landscape is via lowering of the watertable within the alluvium, leading to an increase in seepage loss from the creek. Appendix G contains a detailed assessment of the groundwater predictions relating to the project. Subsidence will cause short term variations in water table elevation and depth to water table, as individual panels are mined. Mackie Environmental Research (2009) has shown that the time scale for adjustment of water table elevations, if not recovery, is months, rather than years or tens of years. The Commission also accepts that there will be negligible long term lowering the water table in the alluvium in the Dooralong valley and the Little Jilliby Jilliby Creek valley as a result of mining. It follows that shallow bores into the alluvium will be unaffected and shallow bores into low-yield hardrock aquifers will only be affected slightly and very slowly. Water loss from filling of cracking at the top of the rock mass will not produce noticeable changes. As a result, impacts on baseflow are likely to be very small, and almost undetectable in the context of normal variability. As noted in Appendix F, the Commission has reviewed the dimensions associated with NSW mines that have extracted longwall panels successfully beneath water bodies in the Sydney Basin including the Mandalong Mine which operates in leases immediately north of the W2CP lease area. On the basis of this review the Commission endorses the finding of the Wyong Strategic Review that “in the absence of major, unforeseen geological anomalies (eg faults and dykes), subsidence-induced hydraulic connectivity between Wyong River, Jilliby Jilliby Creek or their alluvial systems and any underlying mine workings is extremely unlikely”.34

34 DoP (2008a), page 1.

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H.5.3. Potential Impacts of Subsidence on Surface Runoff

Figure 6.12 of the EA shows that subsidence in the range of 2.25 to 2.5m could occur in some areas of the hills to the north and south of Little Jilliby Jilliby Creek, particularly:

The headwaters of Armstrongs Creek (LW 5S to LW 9S)

Couts Gully and Youngs Gully (LW 2SW to LW 5SW)

The headwaters of Myrtle Creek (LW 16N to LW 21N)

Section 6.6.2 of the EA acknowledges that:

Underground mining can cause vertical subsidence, which in itself does not affect the water yield of a catchment but can affect flood levels near subsided areas and, to a small extent, peak flows. Shallow mining under weak overburden layers can result in fracturing that can cause loss of groundwater and surface flows to aquifers or to the mine void. However, in the case of the W2CP the coal seams are very deep and overburden comprises strong, relatively unfractured rock with no significant aquifers so that the scenario of loss of surface flow or groundwater through fractures would be extremely unlikely if not impossible.

However, these statements do not address the potential for surface cracking on steep hillsides or the relative contributions of surface runoff from the hills and floodplains. The available streamflow data from catchments in the Central Coast do not contain any records from small headwater catchments where the contribution from baseflow would be small. An indication of surface runoff contributions for the three main water supply catchments in the Wyong Shire is provided in Table H.8 based on the data extracted from the Pinneena35 database together with estimates of the baseflow as a percentage of total runoff in the Wyong Water Study.

Table H.8: Estimated Average Surface Runoff per Square Kilometre

Wyong River

Jilliby Jilliby Creek

Ourimbah Creek

Catchment Area (km2) 236 92 83

Average Flow (ML/year) 47,806 18,011 21,432

Percent Baseflow (%) 28% 17% 30%1

Inferred Surface Runoff (ML/year) 34,420 14,949 15,002

Inferred Surface Runoff (ML/km2/year) 146 162 181 Note 1 – Baseflow estimate. Whilst the analysis in Table H.8 is simplistic and only considers averages, it provides an indication that the surface runoff from these three catchments is a similar order of magnitude. It also indicates that, notwithstanding the larger proportion of alluvial

35 Pinneena database, V9.3, NSW Office of Water, 2010

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floodplain area in the Doorlong Valley, the surface runoff per square kilometre is similar to that from the other two catchments which have a higher proportion of steep rocky sub-catchments. The inference is that runoff per square kilometre from the steep rocky headwater catchments is not significantly different to that from the alluvial floodplains. In relation to the potential for subsidence to affect runoff from the steep rocky hillsides, the Wyong Strategic Review noted:

The Panel is not in a position to comment on the potential impacts of subsidence on this environment other than in very general terms. It is possible that impacts may include open tension cracks towards the top of slopes, local areas of landslip disturbance, and upsidence induced buckling and cracking of watercourse beds leading to sub-surface flow. However, these impacts could be expected to be on a much smaller scale than those associated with mining in the Southern Coalfield. Sub-surface flow is unlikely to affect water quantity available to the Mardi Dam catchment but it might result in a reduction in water quality for a period of time. These issues require clarification in any environmental assessment lodged under Part 3A in respect of Wallarah 2.36

The Commission concurs with the findings of the Wyong Strategic Review and considers that because both the steep rocky headwater catchments and the alluvial floodplains have a mantle of soil above the underlying rock, runoff is unlikely to be significantly affected by subsidence. In the case of the steep rocky headwater catchments, the soil is relatively thin, but is more likely to be mobilised because of the steep slopes and to fill any cracks that appear at the surface. On the floodplain, the thickness of the alluvial sediments is likely to be sufficient to inhibit the propagation of any cracking to the surface. The Commission concludes that nature of the land surface and the physical characteristics of the soils and alluvium mean that any reduction in runoff due to subsidence is unlikely to be measurable and would not have any significant impact on the Central Coast water supply or cease to pump trigger flows for holders of water access licenses.

H.5.4. Floodplains and Wetlands

The Wyong Strategic Review37 notes that large areas of the Central Coast are susceptible to flooding and that DECC estimates that Wyong LGA contains around 4,370 ha of wetlands which are predominantly located in the low lying areas east of the F3 Freeway. However, none of these “officially” recognised wetlands (designated under SEPP 14 – Coastal Wetlands or zoned 7(g) Wetland Management Zone under the Wyong LEP 1991) are located within the area that lies within the footprint of the proposed W2CP.

36 DoP (2008a), page 66. 37 DoP (2008a), page 15

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Approximately 17% (620 ha) of the footprint of the W2CP mine lies under the alluvial floodplains of Jilliby Jilliby Creek and its tributaries. This floodplain is criss-crossed by numerous ancestral channels, some of which form ox-bow channels, billabongs and paperbark wetlands. Although not identified in the EA as “wetlands”38 (as defined in the DEWHA Directory of Important Wetlands), these areas would appear to contribute to the diversity of habitat on the Jilliby Jilliby Creek floodplain. Unfortunately the existence of these areas, which are identifiable from aerial photographs and can be seen from the public roads, has not been acknowledged in the EA and there has therefore been no assessment of their characteristics or importance. Nor does the EA provide an adequate assessment of the potential impacts of subsidence on these areas. The EA identifies two wetland areas that have been considered in the assessment but which lie outside the area that will be subject to potential subsidence impacts:

Porters Creek wetlands which lie to the east of the F3 and which receive flow from Buttonderry Creek as well as numerous smaller creeks. These wetlands have been under pressure from surrounding urban development including the effects of increased runoff. In recent years Council has developed strategies to limit urban stormwater draining to the wetlands in an effort to improve the hydrologic and ecological functioning of the wetlands. The EA acknowledges the important ecological values of the wetlands39 but dismisses the possible impact from the Buttonderry site facilities, which drain to Buttonderry Creek, “However, the direct impacts associated with surface facilities will not affect the wetland.”40 The possibility of stormwater discharge from the Buttonderry site or runoff from the associated effluent disposal facilities located within the catchments of the Porters Creek Wetlands has been overlooked. This issue is discussed further in Appendix I.

The EA identifies an area of Narrabeen Alluvial Drainage Line Complex located along a tributary of Wallarah Creek immediately south of the TransGrid 300 kV easement that runs in an east-west direction to the north of the Tooheys Road site. The alignment of the proposed rail line is located on the northern side of the TransGrid easement in the vicinity of this ecological community and thus avoids direct impact. Notwithstanding, location of this habitat is designated as a “wetland conservation area” on the plans for the development of the Tooheys Road site.

H.5.5. Conclusions – Potential Impacts of Mining

The Commission concludes that:

1. The assessment of the likely subsidence impacts on the upland creeks is a function of the mine layout presented in the EA. For the proposed mine layout, the predicted worst case upsidence and closure values could be expected to result in negligible impacts for the Wyong River and Jilliby Jilliby

38 W2CP Environmental Assessment (2010), page 13-4 39 Environmental Assessment: Wallarah 2 Coal Project, Page 13-5 40 W2CP Environmental Assessment (2010), page 13-5

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Creek and for Little Jilliby Jilliby Creek up to the start of LW 23N. Site specific impacts cannot be ruled out but these are likely to be sparsely distributed and of a very localised nature.

2. Any creek bed cracking that might occur in the steep rocky headwater creeks is unlikely to lead to a significant loss of flow or to have any impact on the water resource available to supply the Central Coast;

3. There will be negligible long term lowering the water table in the alluvial valleys as a result of mining.

4. Impacts on baseflow are likely to be very small, and almost undetectable in the context of normal variability.

5. Any reduction in runoff due to subsidence is unlikely to be measurable and would not have any significant impact on the Central Coast water supply or cease to pump trigger flows for holders of water access licenses.

H.6. GEOMORPHOLOGY

H.6.1. Overview

The area that is proposed to be undermined for the W2CP lies mainly beneath the catchments of Jilliby Jilliby Creek and its various tributaries including Little Jilliby Jilliby Creek, and Hue Hue Creek. Of the 37.3 km2 covered by the mine footprint approximately 3 km2 is located in the Hue Hue Creek catchment, 3 km2 in the Wyong River catchment and the remainder in the catchment of Jilliby Jilliby Creek and its tributaries. For purposes of considering the potential effects of mine induced subsidence on geomorphic processes it is useful to recognise that the creeks within the area of interest have varying form depending upon where they are located on the landscape and the geology and soils. The creeks vary from narrow incised gullies in the rocky headwater catchments to defined channels running through flat alluvial floodplains. A useful basis for considering the different channel forms and the associated geomorphic processes is to consider the Soil Landscape Units as defined by the NSW Department of Conservation and Land Management. The differences in these soil landscape units reflect differences in the underlying geology, the terrain and the erosion, deposition or in-situ formation processes at work. Mapping of the area of relevance to this review41 defines five main soil landscape units that fit into a sequence related to topography and the underlying geology: The Watagan Soil Landscape Unit is found on fine-grained Narrabeen Group sediments that form the ridge lines along the western and northern sides of the Jilliby Jilliby Creek catchment. The landform is characterised by rolling to very steep hills (>25% slope) with narrow convex crests and ridges, steep side slopes and occasional sandstone boulders and benches. Creeks are ephemeral and comprise steep V shaped gullies lined with boulders and alluvium rather than bedrock.

41 Soil Landscapes of the Gosford – Lake Macquarie 1;100,000 Sheet, CALM, 1993

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The Mandalong Soil Landscape Unit is found on Patonga Claystone on the foot-slopes of the ridges on the western and northern sides of the Jilliby Jilliby Creek catchment and on the lower elevation ridges that form the eastern boundary. It is also present on the northern Boundary of Hue Hue Creek. This landscape unit is characterised by rolling to steep low hills with narrow crests and ridges, short steep slopes (20-60%) and narrow closely spaced drainage lines. Small sandstone benches and boulders are exposed along the incised drainage lines. The Woodburys Bridge Soil Landscape Unit is also found on Patonga Claystone and is intermediate between the sandstone capping on crests of the steeper hills and the alluvial floodplains. Small areas of this unit occur on the eastern and western ridges on the catchment divide of Hue Hue Creek. The landform comprises gently undulating rises to rolling low hills with flat broad crests; short dissected moderately inclined side slopes (up to 20%) and incised closely spaced drainage lines. The Gorokan Soil Landscape Unit is found on the foot-slopes on the eastern side of the Jilliby Jilliby Creek catchment and comprises a large proportion of the Hue Hue Creek catchment. It comprises undulating low hills with broad crests and ridges, long gently inclined slopes (generally less than 15%) and broad drainage lines. The Yarramalong Soil Landscape Unit comprises the areas of alluvium on the floodplains of Wyong River, Jilliby Jilliby Creek and the lower reaches of Little Jilliby Jilliby Creek. The floodplain landform includes meander scrolls, terraces, oxbows and billabongs which are indicative of an active floodplain in which the river channel has altered course in the past.

H.6.2. Assessment

The EA acknowledges that:

Both the major water courses and smaller tributaries of these major watercourses could also be subjected to valley related movements…42

In responding to a number of public submissions, the proponent has also acknowledged that:

The key risk [to habitat and wildlife] of any underground mining proposal is the potential for micro impacts on drainage sensitive ecosystems which are undermined43.

However, it only goes on to assess these movements in relation to the Wyong River, Jilliby Jilliby Creek and Little Jilliby Jilliby Creek, of which large sections are located in alluvial valleys rather than on bedrock. At least two public submissions touched on this issue, one raising the lack of micro studies of the effect of longwall mining along the Wyong River or other tributaries, only broad scale data effects44.

42 W2CP Environmental Assessment (2010), Appendix A2, p63. 43 W2CP Environmental Assessment (2010), p2-39. 44 W2CP Environmental Assessment (2010), p2-16.

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The Commission therefore requested that the proponent characterize the watercourses in the forested areas in the west of the Project Area and provide upsidence and closure predictions. In a response the proponent commented45:

All upland streams are ephemeral and steep and are not conducive to the formation of resistant rock bar and pool systems. Accordingly, there are no specific riverine or riparian ecosystems that rely on pools in streams in the W2CP upland areas. Upland valley areas with their frequent boulder and alluvial-filled, narrow drainage lines provide moister microclimate.

Whilst this response deals with the current situation, the proponent has not provided any mapping or analysis to show where the creeks are located in relation to the predicted subsidence and whether ponding is likely to be created in any of the headwater creeks subject to subsidence. Nor does the EA canvass any options for remedial works that might be undertaken in the headwater creeks if subsidence does create ponding or cracking occurs in isolated locations where rock bars occur in the creek bed. The EA46 provides an assessment of the potential impacts of subsidence on Jilliby Jilliby Creek and Little Jilliby Jilliby Creek. Graph 147 in Section 9.6 of the EA provides a longitudinal profile of Jilliby Jilliby Creek showing the existing and post-subsidence profiles. In general, Jilliby Jilliby Creek is predicted to subside by about 1.3 m which will lead to steepening of the channel grade at the upstream edge and increased ponding near the downstream edge of the subsidence. The assessment identifies four locations in Jilliby Jilliby Creek where subsidence could impact on the creek channel:

Around the upstream (northern) point where subsidence begins. At this location the slope of the channel is expected to increase from about 0.1% to 0.45% over a distance of about 400 m;

Just upstream of the junction with Little Jilliby Jilliby Creek. At this location increased ponding will occur by up to 0.68 m due to the difference between the subsided area upstream and minimal subsidence at the junction.

Just downstream of the junction with Little Jilliby Jilliby Creek. At this location the slope of the channel is expected to increase from about 0.1% to 0.35% over a distance of about 350m;

At a location between 1.5 km and 2.5 km downstream of the junction with Little Jilliby Jilliby Creek. At this location increased ponding will occur by up to 0.32 m due to the difference between the subsided area upstream and the downstream edge of the subsidence affected area.

45 “Subsidence” response, 14/10/2010 46 W2CP Environmental Assessment (2010), pages 9-48 to 9-51 47 W2CP Environmental Assessment (2010), page 9-50

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Graph 248 provides a longitudinal profile of Little Jilliby Jilliby Creek extending 9 km upstream of its junction with Jilliby Jilliby Creek. The profile shows that the creek has a distinct change in grade from about 0.25 to 0.5% at a point about 7.5 km from the junction with Jilliby Jilliby Creek. This location approximately corresponds to the point where Calmans Gully joins Little Jilliby Jilliby Creek and it becomes a fourth order stream according to the Strahler classification system. Because the mine plan does not involve longwall mining under the alluvial section of Little Jilliby Jilliby Creek, there is predicted to be minimal subsidence impact for a distance of about 8.2 km upstream of its junction with Jilliby Jilliby Creek. The profile in Graph 2 shows subsidence of about 1.5 m occurring over a distance of about 450 m upstream of this location leading to ponding depth of about 0.36m. Unfortunately the creek profile analysis does not continue further upstream to a zone where subsidence of about 2m is predicted. In the reaches of Little Jilliby Jilliby Creek upstream of Calmans Gully the longwall panels run approximately parallel to the creek. It can therefore be expected that a similar situation will occur to that which is predicted at the upstream end of the subsidence zone on Jilliby Jilliby Creek. Where the creek first enters the subsidence area, the gradient of the bed of the creek will steepen over a distance of about 400m. Although not identified in the EA, the sections of other tributary creeks that leave the subsidence zone will have the bed slope reduced and there is potential for ponding to occur, particularly where the edge of the subsidence zone is sharp. The Hydromorphology Study (Appendix D of the EA) provides a broad assessment of the characteristics of Jilliby Jilliby Creek and Little Jilliby Jilliby Creek that run through the alluvial zone. Jilliby Jilliby Creek within the area proposed for mining is described as “This section of the creek is dominated by sand, and the channel is symmetrical and trench like (deep and narrow) with a moderate sinuosity”49. The EA notes that:

Riparian vegetation plays a very important role in the stabilisation of Jilliby Jilliby Creek due to the highly erodible nature of the bed and bank material. The vegetation increases bed and bank cohesiveness and any loss of this vegetation will result in channel instability. Riparian vegetation also directly influences large woody debris loading, which provides the dominant geomorphic controls within Jilliby Jilliby Creek. A loss of the large woody debris will increase bedload transport capacity, which in turn could lead to bed degradation and an overall increase in channel instability50.

The EA51 outlines proposals for monitoring and rehabilitation of subsidence within the sections of Jilliby Jilliby Creek and Little Jilliby Jilliby Creek that run through the alluvial zone. These proposals remain very generic, consistent with the need to gain landholder permission to carry out detailed inspections.

48 W2CP Environmental Assessment (2010), page 9-51 49 Hydromorphology Study, page 11. 50 W2CP Environmental Assessment (2010), page 9-45 51 W2CP Environmental Assessment (2010), page 9-53

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In respect of ponding within the alluvial sections of the creeks, the Commission is of the view that this impact should be able to be readily and successfully mitigated as the bed of the creek is generally some meters below the level of the floodplain, thus facilitating construction of drainage conduits (trenching, buried agricultural drains etc). Unfortunately, the EA provides no analysis of the effect of subsidence on the floodplain itself. In particular, no assessment is provided of the impact of the subsidence troughs that will be created running in a south-south-westerly direction across the floodplain. This situation has been taken account of in the flood modelling (see Appendix J), but the potential for the creation of additional ponding areas or channel avulsion within the Jilliby Jilliby Creek floodplain has been overlooked.

H.6.3. Conclusions - Geomorphology

The Commission concludes that:

1. The assessment of the likely subsidence impacts on the upland creeks is a function of the mine layout presented in the EA. Site specific impacts cannot be ruled out but these are likely to be sparsely distributed and of a very localised nature.

2. Any ponding that occurs as a result of subsidence on upland streams is likely to introduce a new habitat and lead to some localised change in the ecology.

3. The Commission notes the Proponent’s response to a question regarding the characteristics of the watercourses in the forested areas and the impacts of subsidence, but considers inadequate attention has been given to options for remedial works that might be undertaken in the headwater creeks if subsidence does create ponding or cracking occurs in isolated locations where rock bars occur in the creek bed.

4. Ponding within the alluvial sections of the creeks should be able to be readily and successfully mitigated as the bed of the creek is generally some meters below the level of the floodplain, thus facilitating construction of drainage conduits (trenching, buried agricultural drains etc).

5. The EA outlines proposals for monitoring and rehabilitation of subsidence within the sections of Jilliby Jilliby Creek and Little Jilliby Jilliby Creek that run through the alluvial zone. These proposals remain very generic at this stage, consistent with the need to gain landholder permission to carry out detailed inspections.

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H.7. SURFACE WATER QUALITY

H.7.1. Data Collection

Notwithstanding the claim that, “Extensive baseline data has been systematically collected by the WACJV on local water quality and will form an important tool following subsidence”52, the actual extent, frequency and duration of monitoring is not entirely clear from the documentation as shown by the following inconsistencies in the EA:

A total of 28 sites were sampled for water quality on a monthly basis during late 2006. The location of the monitoring sites is shown on Figure 9.6.53

On the other hand Figure 9.6 of the EA 54 shows 14 “Historical” sites and 14 “Current” sites;

Appendix 2 of the Hydromorphology Study provides details of monthly sampling and water quality analysis at only 9 locations over the period mid 2006 to late 2008 (30 months);

Table 3.1 of the Site Water Management Strategy provides only the maximum and minimum water quality values for two additional sites over the period May 2006 to May 2007 (13 months).

Furthermore, in response to a request from the Commission to characterize the watercourses in the forested areas on the western side of the project area, the proponent has provided the following:

Water quality of major streams in the project area has been monitored on a monthly basis over the majority of the period since commencement of exploration in 1996. A brief outline of the water quality condition of these streams is provided in Section 9.6.7 of the EA55.

The statement that “Extensive baseline data has been systematically collected”, does not appear to be supported by the data and analysis in the EA. In addition, to the extent that a general interpretation is provided, it is not necessarily supported by the data. For instance, in Section 9.6.4 of the EA, the following general conclusion is reached:

A combination of its low flow characteristics and catchment land uses has resulted in frequently degraded water quality within Jilliby Jilliby Creek, in terms of elevated faecal coliforms and nutrients particularly at low flows56

52 W2CP Environmental Assessment (2010) Section 9.6.13, page 9-53 53 W2CP Environmental Assessment (2010) Section 9.6.4, page 9-44 54 W2CP Environmental Assessment (2010) page 9-44 55 Response from Proponent “Subsidence” (14/10/2010) 56 W2CP Environmental Assessment (2010), page 7-10

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The reference to elevated coliform levels is only partially supported by the data in Appendix 2 of the Hydromorphology Study which shows wide variations in coliform levels between successive months. No flow data is presented corresponding to the water quality data that could be used to substantiate the assertion that elevated coliform levels were related to low flows. Table H.9 provides a summary of monthly flow statistics in Jilliby Jilliby Creek expressed as a percentage of mean monthly flow. The data shows that over the period when water quality data was collected (July 2006 to October 2008) there was a period of particularly low flow from July 2006 to April 2007, with the exception of September 2006. If the assertion that high coliform levels were a function of low flows was correct, the water quality data could be expected to show consistent elevated levels between July 2006 to April 200. In practice, particularly high levels of coliforms in Jilliby Jilliby Creek were recorded at different times at different locations and did not show consistently high levels for the extended period of low flow. It therefore appears that there are other factors influencing coliform levels rather than the just flow.

Table H.9: Jilliby Jilliby Creek Flow as Percentage of Long Term Average

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2006 3% 1% 3% 0% 0% 0% 0% 0% 257% 7% 5% 6%

2007 1% 0% 2% 3% 24% 499% 57% 358% 160% 8% 18% 1053%

2008 300% 228% 130% 460% 20% 143% 17% 13% 513% 24% 19% 49%

H.7.2. Water Quality Assessment

Section 9.6.7 of the EA provides a highly generalized overview of the water quality characteristics of the areas that are proposed to be undermined (Hue Hue Creek, Little Jilliby Jilliby Creek, Jilliby Jilliby Creek, and Wyong River). Unfortunately the EA does not assess the existing water quality and potential impacts on:

Buttonderry Creek as a result of overflow from the stormwater system at the Buttonderry Site or runoff from the effluent disposal area (which will be located outside the area which drains to the Entrance Dam). Water quality data has been collected from Buttonderry Creek (Site W15) from July 2006 to October 2008. No assessment has been provided of the overall water quality in the creek or the suitability of the water for discharge into the Porters Creek Wetland. Data collected by Council from the Buttonderry Waste Management Centre and the Porters Creek Wetlands has not been referenced.

Wallarah Creek as a result of overflow of stormwater from the Tooheys Road site. Water quality data for Wallarah Creek is referenced in the Site Water Management Strategy, but no details of the actual data are provided and there is no assessment of the overall characteristics or potential impacts resulting from the proposed project.

The proponent has not given adequate consideration to the potential impact of the project on the Porters Creek Wetlands. For example, page 3-11 of the Proponent’s response to submissions says:

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The ACA has for some time erroneously maintained that the project would impact on wetlands such as Porters Creek Swamp which is located …well outside the impact zone of the W2CP.

This statement overlooks the fact that the Buttonderry Site is located within the catchment that drains to the Porters Creek Wetlands. While there will be no direct impact on the wetlands as a result of subsidence any stormwater overflow from the Entrance Dam and runoff from the sewage effluent irrigation area will drain into Buttonderry Creek and then to the wetlands.

H.7.3. Potential for Iron Staining

In addition to the shortcomings in the assessment of the existing water quality regime and potential impacts of discharges from the operating sites, no attempt has been made to characterise water quality in the steep headwaters creeks, notwithstanding the assertion that iron staining is unlikely to occur: Without the benefit of supporting evidence, the EA claims:

With no known iron staining from existing springs there is no basis to suggest it will result from mining activity. There is a more realistic case to suggest that the existing joint/fracture systems may actually be enhanced by subsidence effects to potentially increase the water bearing capacity of these upland areas.57

and

The assessment has shown there is little if any risk of water quality contamination from metals such as iron and manganese or methane as can occur in the Southern Coalfield. This is due to differing geology, depth, near surface stratigraphy, lack of continuous cracking and integrity of the deep surface alluvials.58

Attachment A to the submission from the NSW Office of Water (NOW) notes that:

NOW regards the potential water quality changes as a consequence of surface cracking causing soluble oxidised metals to be released as inadequately assessed.

Proponent’s response states:

Further, W2CP has found no geochemical evidence to indicate that there is potential for significant contribution from or catchment impacts due to soluble oxidized metals in the steep, short drainage lines in the western forested hills in the latter years of mining

Proponent’s response to the submission from NOW proposes to manage this issue in the following manner:

57 W2CP Environmental Assessment (2010), page 4-57. 58 W2CP Environmental Assessment (2010), page 9-40.

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W2CP proposes an adaptive management approach for addressing this issue. This would involve ongoing geochemical characterization of the near-surface strata in these future areas to be mined. This information would be reviewed in the light of the subsidence monitoring information including fracture status and extensometer results.

In response to a question from the Commission, the Proponent commissioned further investigation and assessment of the geochemical characteristics of the rocks adjacent to the upland streams.

W2CP has also undertaken additional recent work to substantiate conclusions made in the EA report in relation to the low potential for impacts to arise due to iron staining or related water quality effects following subsidence in upland and valley streams. A geochemical assessment report by EcoEngineers Pty Ltd is attached as Appendix 1 to this document. The report concludes that the extensive amount of testing undertaken confirms that there is negligible likelihood of iron staining impacts that could arise from the W2CP.59

The assessment by EcoEngineers concluded:

This means that we can expect no generation of highly anaerobic conditions with vertical fractures and sheared bedding planes in the TFSS as a result of mine subsidence effects and, most importantly, no generation of significantly acidic groundwaters or groundwater-fed springs with acidic waters high in iron, manganese, nickel or zinc etc.60

H.7.4. Conclusions – Surface Water Quality

The Commission concludes that:

1. The water quality data collection and assessment is adequate to characterise the general characteristics of Jilliby Jilliby Creek and the Wyong River.

2. The existing water quality data from Buttonderry Creek has therefore not been used to establish water quality goals for site discharge from the Buttonderry Site and its associated effluent disposal area.

3. The water quality data for Wallarah Creek has not been used to establish water quality goals for site discharge.

4. Notwithstanding the geochemical analysis that was recently undertaken to assess the potential for iron staining, no effort has been made to sample water quality from upland tributaries where seeps and springs might exhibit low pH.

59 Response from Proponent “Subsidence” (14/10/2010), page 10 60 Assessment of Hydrogeochemical Effects of Mine Subsidence in Vertical Fractures and Claystone Bedding Planes in Upland Terrigal Formation Sandstone, EcoEngineers, 22 September 2010

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H.8. RECOMMENDATIONS

The Commission recommends that:

1. No mining to be permitted beneath Myrtle Creek and Armstrong Creek and beneath any watercourse within the Terrigal Formation61 until a comprehensive assessment of features (including surface water, groundwater, ecology and Indigenous heritage) and potential mining impacts on such features has been undertaken to the satisfaction of the Director-General of the Department of Planning.

2. No change mine layout be permitted, particularly the location of the first workings under Little Jilliby Jilliby Creek, be permitted until a comprehensive assessment of potential mining impacts has been undertaken to the satisfaction of the Director-General of the Department of Planning.

H.9. REFERENCES

Department of Conservation and Land Management, 1993 Soil Landscapes of the Gosford – Lake Macquarie 1:100 000 Sheet, CALM, Sydney, 1993

EcoEngineers, 2010

Assessment of Hydrogeochemical Effects of Mine Subsidence in Vertical Fractures and Claystone Bedding Planes in Upland Terrigal Formation Sandstone, 22 September 2010

Gosford Wyong Councils’ Water Authority, 2007

Water Plan 2050: Options Report for the Long Term Water Supply Strategy, July 2007

Gosford Wyong Councils’ Water Authority, 2010 Headworks Boomerang Tunnel transfers.xls, spreadsheet provided by, 3/11/2010

Gosford Council and Wyong Council, 2007

WaterPlan 2050, Adopted August 2007

NSW Government Water Sharing Plan for the Central Coast Unregulated Water Sources 2009

NSW Office of Water, 2010

Pinneena database CD, V9.3

Sinclair Knight Merz, 2010 Wyong Water Study: Assessment and Documentation of Current Groundwater and Surface Water Information - Wyong, Report prepared for the NSW Department of Planning, August 2010

61 As defined in Figure 1 of WACJV (2020c).