Murray River Technical Report GROUNDWATER AND … 1... · along natural flow paths to the Murray River. The travel time of contact groundwater depends on several factors including

1 | G r o u n d w a t e r M u r r a y R i v e r T e c h n i c a l R e p o r t

Murray River Technical Report

GROUNDWATER AND GEOCHEMISTRY

Context ........................................................................................................................ 2

Groundwater Quality ................................................................................................ 4

Groundwater Quantity .............................................................................................. 4

Predicted Effects and Mitigation .................................................................................. 6

Groundwater Quality ................................................................................................ 6

Groundwater Quantity .............................................................................................. 7

Key issues of concern .................................................................................................. 8

Groundwater quality ................................................................................................. 9

Groundwater quantity ............................................................................................. 11

Residual Effects Significance Analysis ...................................................................... 14

Cumulative Effects ..................................................................................................... 17

Conclusions ............................................................................................................... 17


Context

For the purposes of this assessment, groundwater effects include groundwater quality and quantity (including flow paths). Groundwater is an integral component of the water cycle and is linked with environmental conditions and ecosystems within the Project area. Groundwater is a key component that influences the aquatic and terrestrial environment including: system functioning; the health of fish and other aquatic life; wetlands; wildlife; and water quality and quantity (discussed in their respective chapters).

The development of the Project will result in direct impacts to groundwater resources. Groundwater effects will occur throughout the entire life of the Project and are expected well past closure. The groundwater resource will be primarily influenced by the underground mining components of the Project and associated impacts from subsidence. The groundwater resource and water balance will also be influenced by the surface components of the Project including mining operations, processing requirements, and by project infrastructure (including water management infrastructure) that will be located on both sides of the Murray River. Project infrastructure will be connected by an underground decline system which will be used to pump contact groundwater (from underground works) to the surface for either re-use in the mine or to be discharged to the exfiltration gallery.

Figure 1. Local and regional study area for groundwater


Changes to groundwater quality and quantity have the potential to impact surface water quality and quantity, aquatic resources, fish, terrestrial ecosystems, wildlife, land use and human health. Groundwater has the potential to adversely impact the aquatic environment through changes to surface water quantity and quality. During operations, drawdown of the water table has the potential to decrease surface water quantity in streams that overlie the mine. As well, excess contact groundwater within the mine will be pumped to the surface and discharged to an exfiltration gallery at the Decline Site, which will then flow to the Murray River.

After closure, contact groundwater will persist within the post-mine voids until water levels in the groundwater system recover, after which groundwater will slowly migrate along natural flow paths to the Murray River. The travel time of contact groundwater depends on several factors including hydraulic conductivity and gradient, porosity and distance from the underground mined area to the Murray River. At its closest point, the underground mining works are within approximately 500 metres (m) of the Murray River. The post-closure temporal boundary for the groundwater quantity and quality effects assessment has estimated travel times range between 400 years (high permeability case) and 1,000 years (base case). The potential solute migration plume from the coarse coal rejects (CCR) piles was simulated for 200 years during post-closure.

Subsidence has the potential to further impact drawdown and consequently magnify impacts to surface water and groundwater quantity and quality. To quantify potential uncertainty related to effects, the Proponent evaluated this impact by undertaking sensitivity analyses in the groundwater model. As there are no local analogs to consider in the assessment, the Proponent has used information from global experience and a literature review related to longwall mining. Recognizing modelling and sensitivity analysis, uncertainty remains around the extent of disturbance of subsidence and the subsequent impacts on groundwater drawdown.

Understanding of hydrogeology (ground water quantity and quality) is influenced by a multitude of factors, each with their own uncertainties. These factors include:

Water balance; Hydrology (surface water quantity); Geochemistry; Fault lines; and Subsidence.

Potential effects on groundwater quality and quantity were predicted through multiple model scenarios. Sensitivity analyses were developed in recognition of uncertainties such as groundwater recharge and permeability of the geological materials. EAO notes that the uncertainty in the predicted effects is compounded in several situations as the input of some models is dependent on the output of others. For example, base groundwater assumptions generate groundwater modelling outputs, which are then used as inputs to the water balance and water quality models, and where these model


outputs are then used to evaluate effects on other VCs. This model information is further used with subsidence modelling. To address this, uncertainty is carried forward via sensitivity analysis in the subsequent modelling and assessments.

Groundwater Quality

Groundwater throughout the local study area (LSA) is slightly basic (mean pH of 7.2 to 8.4). Calcium and bicarbonate tend to be the dominant ions in the shallow groundwater (less than 50 mbg), and sodium and bicarbonate dominate in the deeper groundwater. Total dissolved solid trends upwards with depth. Background concentrations of some metals are elevated; dissolved barium, iron, lithium, and manganese consistently exceeded the provincial water quality guidelines for the protection of freshwater aquatic life or raw drinking water supply in samples collected from groundwater wells in the Project area.

Groundwater Quantity

The groundwater flow system in the Project area is characterized by groundwater flowing from the upper foothills towards the Murray River. On the west side of Murray River, the M20 Creek and Mast Creek basins behave as intermediate catchment basins; the watersheds of Twenty Creek and other minor tributaries within the extent of underground mining behave as local catchment basins. On the east side of Murray River, the small watersheds containing M19A, M17B, and M19 Creeks behave as local catchment basins for shallow groundwater flow adjacent to the Coal Processing Plant (CPP) and CCR piles.

Groundwater is recharged by greater precipitation at higher elevations (due to the orographic effects), while valley bottoms constitute groundwater discharge zones. Documented seasonal variations in groundwater levels have been as high as 2 m within the baseline study area.

Stream flow is dominated by groundwater discharge (often referred to as base flow) during low flow seasons in winter. During freshet, streams may be recharging groundwater, particularly along reaches at higher elevations. Stream reaches at lower elevations are predominantly situated in groundwater discharge zones. Groundwater likely supports wetlands found along the flood plains of the Murray River during non-peak flow periods.

The Proponent predicts that drawdown of the water table from the mine will exceed the range of natural variability in some areas. Dewatering of the underground mine during operations may result in lowering of the water table (≤2.5 m (base case scenario) to >100 m (most conservative scenario)), which will have associated changes in flow directions, hydraulic gradients, and baseflow discharge to local streams. Following the


end of the mine life (25 years), the workings will be allowed to flood and the water table will rebound, eventually returning to near pre-mine conditions.

Coinciding with the area of water table drawdown, surface subsidence is predicted to occur. Subsidence will occur in the area immediately overlying the longwall panel within months of mining: the magnitude of subsidence will depend on the number of coal seams mined vertically. The overall degree of subsidence will expand spatially and temporally over the mine life. The changes in topography associated with subsidence are anticipated to have less influence on groundwater tables than mine dewatering; however, localized changes may be observed in some areas. The Application assumed that faults do not represent major groundwater flow paths. This is based on interpretation of regional faults, which are mapped as reverse (compressive) faults, and are infilled by fine grained sediments. It is possible that there could be reactivation on the faults caused by caving and subsidence. This may influence groundwater flow paths, and as such, was considered via additional sensitivity analyses conducted during the Application review stage. The Application notes the potential for changes to rock hydraulic conductivity on account of subsidence. In the initial model submitted with the Application, a zone that extended 85 m above the mine was modelled with a 20 times increase in hydraulic conductivity, which accounts for effects of subsidence. An updated model scenario with a larger zone of increased hydraulic conductivity overlying the mine was provided in response to Working Group comments.

Adjacent to the CPP, the two CCR piles will result in reduced recharge to the groundwater system in the local area; however, the resultant change in groundwater quantity would be <10% compared to baseline. The CCR piles will be built with a geomembrane liner, overdrains, and seepage collection systems. The Proponent predicts this mitigation will result in limited potential for loss of contact water to groundwater during operations. During post-closure, infiltration through the closure cover will continue to be collected by the seepage collection system, and then will be allowed to exfiltrate to groundwater. Flow path and solute transport analyses show that seepage would stay in shallow groundwater beneath and downgradient of each CCR pile, discharging to M19 and M19A Creeks downslope.

Chapter 7 of the Application includes a full discussion of groundwater quality and quantity effects.


Predicted Effects and Mitigation

This section summarizes the Proponent’s predicted effects, proposed mitigation and residual effects based on the Application.

Groundwater Quality

Table 1 identifies the potential groundwater quality effects and measures to mitigate potential effects as well as monitoring.

Table 1. Potential effects and proposed mitigation for groundwater quality

Potential Effect Proposed Mitigation and Monitoring

Change in groundwater quality related to seepage from CCR piles

Geomembrane liners will be installed and there will be a seepage collection system at CCR North and CCR South;

A network of monitoring wells will be installed downslope of CCR North and CCR South;

CCR pile contact water will be captured in a seepage collection system and preferentially used it in the CPP;

Water infiltration to groundwater from the CCR piles will be limited due to the geomembrane liners;

Excess CCR pile contact water will be collected in the CPP pond before routing through the mine and to the Exfiltration Gallery at the Decline Site; and

CCR piles will be covered and re-vegetated at closure, establishing a low permeability layer to limit infiltration through the pile.

Change in groundwater quality related to underground mining operations

Groundwater inflows to the underground mine will be collected in a central water sump;

Underground workings will be allowed to flood at closure; and

Plugs in shafts/declines will be included at closure to minimize mixing of groundwater from shallow and deep sources.


Predicted Residual Effects on Groundwater Quality

Change in groundwater quality related to seepage from CCR piles.

The Application and supporting studies predict the proposed CCR piles will have a residual adverse effect on groundwater quality, during operation and post closure, due to the development of a small plume in shallow groundwater beneath and downgradient of each CCR pile; the spatial extent will be limited due to a short flow path to M19A and M19 Creeks.


Table 2 identifies the potential groundwater quantity effects and measures to mitigate potential effects as well as monitoring.

Table 2. Potential effects and proposed mitigation for groundwater quantity

Potential Effect Mitigation and Monitoring

Change in groundwater quantity related to underground mining operations and subsidence

No specific mitigation measures have been identified to minimize the impact on groundwater quantity related to underground mining operations and subsidence.

Groundwater flow into the mine will be collected and discharged during operations;

Surface flow conditions will be monitored to determine if reduced flows are evident, which will allow for evaluation of potential mitigation measures, which could include modification of mining methods (e.g., rate of retreat, specific panel layouts) to reduce potential for flow effects during mining of subsequent panels;

If monitoring indicates flows in M20 Creek are reduced due to groundwater drawdown from operations and subsidence processes, a re-assessment of the effects on fish habitat may be required and the subsequent implementation of a fisheries offsetting plan may result;

Sealing off mined out blocks as mining proceeds; and

Underground workings will be allowed to flood at closure.

Predicted Residual Effects on Groundwater Quantity

Change in water levels, gradients and flow direction related to the underground mine, surface subsidence and CCR piles.


The Application and supporting studies predict the underground mine will have a residual effect on groundwater quantity during operation through post closure (until full recovery of water table), which includes water table drawdown, alteration of groundwater flow pattern (flow direction, hydraulic gradient) toward the mine zone as a local groundwater sink, and potential reduction of groundwater discharge to the creeks.

The predicted surface subsidence is expected to have some residual effect during operation and post-closure, including potential changes in groundwater levels and flow patterns, and groundwater discharge at the local scale. The residual effect of the CCR piles during operation and post closure is expected to include slight change of hydraulic gradients and hence a small reduction of groundwater discharge in the small area between the footprints of the two piles along the M19A Creek section.

Key Issues of Concern

EAO’s summary of Key Issues of Concern identifies key issues raised by the Working Group during Application Review, key responses and actions from the Proponent, and identifies additional mitigation measures.

The primary concerns related to groundwater quantity and groundwater quality are:

uncertainty regarding the characterization of potential effects due to: o low confidence in understanding of the baseline environment due to

limited number of deep groundwater wells; o reliance on models that were based on limited baseline information; and o uncertainty in the characterization of potential subsidence impacts on

groundwater; potential cascading effects on the terrestrial and aquatic environment; and uncertainty in the effectiveness of the proposed adaptive management and

mitigation options if the effects are not as predicted.

To address concerns raised during the EA, EAO facilitated an iterative issues resolution process with Working Group members and the Proponent. Through this process, EAO directed the Proponent to provide detailed responses to issues raised and to track concerns and subsequent responses. EAO acknowledges the efforts made by the Proponent to support the EA by providing additional information and engaging in issues resolution.

While EAO acknowledges that issues resolution has occurred and uncertainty had been reduced for some concerns, EAO recognizes that the information provided throughout the EA does not adequately address all concerns identified. Consequently, uncertainty remains and will be addressed through the development and implementation of the Management Plans listed in the EA Certificate. The Proponent will be required to


engage First Nations and technical reviewers (as appropriate) in the development of these Management Plans, which will allow for continued discussion on mitigation and monitoring opportunities beyond the EA. Each Management Plan will be developed and implemented to the satisfaction of EAO and consistent with relevant EAO policy guidance relating to Management Plans.

In order to mitigate key concerns on groundwater effects, EAO has included the development and implementation of the following Management Plans as a proposed condition of the EA Certificate:

Subsidence Management Plan; Fish and Fish Habitat Management Plan; Selenium Management Plan; Runoff, Erosion and Sediment Control Plan; Wetland Management Plan; Groundwater and Surface Water Management Plan; and Reclamation and Closure Plan.

In addition to the measures outlined in the Table of Conditions, the Certified Project Description provides further measures to mitigate adverse effects on groundwater. Permits under the Environmental Management Act and the Mines Act will also identify requirements to mitigate adverse effects on groundwater.

The following tables identify key issues of concern raised during Application Review and also identifies key responses and actions from the Proponent and identifies additional mitigation measures.

Groundwater Quality

Table 3. Key Concerns raised during Application review for groundwater quality

Key issues of concern raised during Application Review

Proponent Response/Action/Mitigation

Uncertainty regarding the source term for groundwater inflows into the underground workings was derived from limited groundwater samples

Engaged in iterative issues resolution and provided detailed response through tracking table. Supplemental information was provided to address concerns.

Opportunities for addressing uncertainty and defining mitigation will be provided through the development and implementation of the relevant Management Plans listed in the EA Certificate.


Uncertainty with the conceptual model for the underground water quality:

reference to geochemical load available at closure due to saturated conditions; and

does not include the potential for mine water discharge from the underground workings during the closure and post-closure periods.

Updates were made to water balance and water quality predictions using the updated source terms. The results re-confirmed the original conclusions of the Application with respect to potential effects in the receiving environment.

Opportunities for addressing uncertainty and defining mitigation will be provided through the development and implementation of the relevant Management Plans listed in the EA Certificate.

Uncertainty in Proponent’s geochemical source terms and subsequent evaluation and impact to the groundwater quality modelling results and effects assessment


Opportunities for continued mitigation will be provided through the development and implementation of the relevant Management Plans listed in the EA Certificate.

Information on gob formation, sampling and geochemistry was not provided in the Application

Information provided and evaluated by the Working Group.

Uncertainty in the Proponent’s groundwater quality predictions:

predictions to be updated to match the assumptions of the gob;

recognition that contact (mine-influenced) groundwater is expected to ultimately reach the Murray River;

uncertainty regarding water quality predictions for groundwater inflow at the end of mine life (under prediction); and



Updates were made to water balance and water quality predictions using the updated source terms. The results re-confirmed the original conclusions of the Application with respect to potential effects in the receiving environment.

Back-calculations were prepared for water quality parameters identified by Health Canada as contaminants of potential concern, as well as those


timing on exceedances (selenium).

identified by Ministry of Energy and Mines (MEM) as being indicators of ML/ARD potential and include: sulphate, dissolved aluminum and cadmium and total arsenic, barium, chromium, copper, iron, lead, lithium, manganese, mercury, nickel, selenium, and silver.

Timing and duration of the selenium guideline exceedance in M19A Creek has changed based on the updated water quality model results compared to the water quality model results presented in the Application.

Uncertainty in Proponent’s proposed use of nitrogen flooding as a safe and effective method for acid rock drainage mitigation

Acknowledged that nitrogen flooding is not a primary means of ML/ARD mitigation, but that it would likely have some positive impact in this regard by limiting opportunity for oxidation.


The following table identifies the key issues of concern raised during Application Review and also identifies key responses and actions from the Proponent and identifies additional mitigation measures.

Table 4. Key Concerns raised during Application review for groundwater quantity

Key issues of concern raised during Application Review

Proponent Response/Action/Mitigation

Unresolved doubts about the suitability of the existing groundwater dataset recognizing that a full coverage of the mining footprint as well as information from deeper depths is not available

Recognized concern and noted that additional information will be provided as required during permitting.

Engaged Forests, Lands, and Natural Resource Operations (FLNR) for advice on proposed drilling program required to support permitting.

Uncertainty with the inclusion of the potential impacts of subsidence:

description of subsidence footprint and affected area used in assessment; and

potential to change groundwater flow paths and the low flow regimes of the creeks within, and

Engaged in iterative issues resolution and provided detailed response through tracking table. Supplemental information was provided to address concerns including:

Additional subsidence modelling and analysis was completed; and

Additional groundwater modelling scenarios were completed to evaluate


adjacent to the underground workings footprint.

sensitivity related to subsidence.


Uncertainty regarding whether effects to the low flow regimes of the nearby creeks will be reversible once the underground workings flood. Reviewers raised concerns that the surface-groundwater interactions have the potential to be significantly altered in areas where subsidence has occurred, and stream flows may not return to the pre-mine baseline regime

Engaged in iterative issues resolution and provided detailed response through tracking table. Supplemental information, including literature review from global experience, was provided to address concerns.


Uncertainty regarding some of the assumptions and baseline data used in the ground water model and hydrogeological assessment:

concern with the site-specific hydrogeological characterization;

uncertainty is further magnified when the outputs from the groundwater model are incorporated into other models (e.g. water quality);

FLNR has recommended further drilling to increase the hydrogeological data set to reduce uncertainty and risk;

subsidence and potential impacts to hydraulic conductivity;

predicted vertical movement, horizontal movement and strain along the affected stream reaches;

assumption that the faults do not


Engaged FLNR for advice on proposed drilling program required to support permitting.

Additional subsidence modelling and analysis was completed.

New groundwater model scenario results were used to inform evaluation of potential effects associated with subsidence, and to address sensitivity and uncertainty associated with estimates of groundwater inflow rates to the underground mine, and of water table drawdown and implications to baseflow in M20 Creek and Mast Creek.

Information and maps were provided to clarify model assumptions and results.

Commitment to include plugs in shafts/declines at closure for the purpose of minimizing mixing of groundwater from


represent major groundwater flow paths;

requested maps clearly depicting groundwater model calibration and drawdown results;

exclusion of the effects on groundwater flowpaths in the model from declines, shafts, tunnels (openings) connecting the surface to the mine, both during operations, and post-closure;

request for further groundwater characterization in the northern portion of the mine;

the post-closure analysis should account for structural decay of the native rock around the openings, grout and shotcrete decay, and realistic preferential pathways;

bypass of plugs through collapsed rock should be considered, and the location and design criteria for plugs should be explained;

incorporation of linear elements (e.g., drains, streams) into the numerical flow model;

post-closure seep monitoring for the openings should be discussed; and

Uncertainty in Proponents description of ‘self-healing’ as it relates to the subsidence effects under M20 creek.

shallow and deep sources.

Commitment to adaptive management and monitoring as per Management Plans.


Groundwater monitoring plan not provided in original application

Groundwater monitoring plan submitted as supplemental information.

Commitment to implement groundwater monitoring plan throughout mine phases.



Uncertainty in the geochemical baseline:

source terms and characterization of near seam strata, and drill log information;

uncertainty regarding gob characterization; and

concern that the source terms for groundwater inflows into the underground workings were derived from a single groundwater sample.

Engaged in iterative issues resolution and provided detailed response through tracking table. Supplemental information was provided to address concerns including:

The Proponent collected additional samples to increase the confidence in the geochemical relationship between CCR and gob and updated the water quality prediction model accounting for the updated mass of gob;

A re-conceptualization of the gob resulted in an increase the total mass at the end of the mine life from 240 million tonnes and 350 million tonnes in previous iterations, to 450 million tonnes; and

Re-evaluation of the available rock samples (gob, interburden, roof and floor, and partings) re-confirms that the CCR source terms are a reasonable and conservative source term for the gob.

Uncertainty in the cumulative effects assessment for groundwater effects.

Engaged in iterative issues resolution and provided detailed response through tracking table. Supplemental information was provided to address concerns including a cumulative effects assessment to assess the potential combined impacts of the Murray River Project with other projects in the area (historic Quintette (Babcock) Mine, proposed expansion of Quintette Mine, and Hermann Mine).

Residual Effects Significance Analysis

After considering all relevant proposed mitigation measures, EAO concludes that the Project would result in the following residual adverse effects on groundwater:


Groundwater quality: Change in groundwater quality related to seepage from CCR piles and underground mining operations.

Groundwater quantity: Change in water levels, gradients and flow direction related to the underground mine, surface subsidence and CCR piles.

EAO’s characterization of the residual effect of the Project is summarized below, as well as EAO’s level of confidence in the effects determination (including their likelihood and significance).

Table 5. EAO's Significance Analysis for groundwater

Criteria Assessment Rating

Rationale

Context

Groundwater quantity and quality are critically linked to other values, and surface-groundwater interactions are complex. The Project will adversely impact ground water quality and will change the groundwater geochemistry, levels, gradients and flow direction. Groundwater quality effects may persist for >1,000 years.

Magnitude

Groundwater Quality

Moderate

Groundwater quality will be adversely impacted by groundwater drawdown and exposure to mined areas and gob from construction through post-closure. There are uncertainties on the direct and indirect impacts on groundwater quality from subsidence.


High

Effects on groundwater drawdown will exceed the range of natural variation, potentially by large amounts. There are compounding uncertainties on the direct and indirect impacts on groundwater quantity from subsidence effects on preferential flow pathways and groundwater drawdown.

Extent Landscape Effects of subsidence impacts on groundwater quality are anticipated throughout the entire zone of influence for subsidence which extends beyond the Mine Site Assessment footprint but not the LSA.

Duration Long-term / Permanent

EAO expects the groundwater effects will persist until post closure when natural groundwater flow patterns are re-established. Estimates range from 400 to >1,000 yrs.


Reversibility Irreversible EAO considers groundwater effects resultant from subsidence to be irreversible.

Frequency Continuous EAO expects the impact to groundwater quantity and quality will be continuous.

Likelihood There is a high likelihood that residual effects will occur during construction, operation, closure and post-closure phases of the Project.

Significance Determination

The groundwater quantity and quality effects will continue far into the future, will be largely irreversible and will impact on other VCs.

EAO considered the concerns of technical reviewers throughout the entire EA process, including pre-Application. Key concerns include:

adequacy of baseline information to support modelling;

characterization of effects;

potential cascading effects on the terrestrial and aquatic environment;

uncertainty in the characterization of potential subsidence impacts associated with the Project recognizing that the effects of subsidence will have both direct and indirect impacts on groundwater quantity; and

uncertainty in adaptive management and mitigation options if the effects are not as predicted.

EAO recognizes that the effects of subsidence will have both direct and indirect impacts on the existing groundwater regime. In addition there is an inherent degree of uncertainty in the characterization of potential subsidence impacts associated with the Project as the model used to predict the impacts of subsidence are not based on local or analogous geological strata or depth of mining. This uncertainty makes it difficult to predict the magnitude, scale, and impact of the potential effects of subsidence and the correlated impacts on groundwater drawdown.

EAO also considered the above analysis regarding the relative extent of the impact, the mitigations presented by the Proponent, and conditions proposed. EAO agrees with the Proponent’s conclusion that the Project will cause residual adverse effects on groundwater.

Based on the above analysis and having considered the proposed mitigation measures (which would become legally binding as a condition of a certificate), EAO is satisfied that the Project is not likely to result in significant residual adverse effects on groundwater.


Confidence EAO has a low level of confidence in the likelihood and significance determination given:

relative extent of the impacts;

the understanding and uncertainties regarding impacts;

opportunities for continued mitigation through the development and implementation of the relevant Management Plans listed in the EA Certificate; and

uncertainty in adaptive management and mitigation options if the effects are not as predicted.

Cumulative Effects

The Proponent carried out a cumulative effects assessment to assess the potential combined impacts of the Murray River Project with other projects in the area. Three projects were identified as potentially having a cumulative effect: historic Quintette (Babcock) Mine, proposed expansion of Quintette Mine, and Hermann Mine. The Proponent concluded that cumulative effects of mine dewatering and water level management and seepage of contact groundwater and management would not be significant.

EAO recognizes the concerns of technical reviewers regarding the potential impacts and uncertainties of predicted post-closure water quality and quantity and the potential cumulative effects of the other projects within the Murray River watershed. EAO also recognizes the groundwater effects will persist until post closure when natural groundwater flow patterns are re-established. Estimates range from 400 to >1,000 yrs.

EAO further recognizes that mine site discharges can be effectively regulated through the Environmental Management Act (EMA) permitting process, and informed through the existing Northeast Murray River Aquatic Cumulative Effects Assessment Framework. Through an EA Certificate condition the Proponent will be required to continue to participate in the Northeast Murray River Aquatic Cumulative Effects Assessment Framework Steering Committee. Based on the information above, and having regard to the proposed mitigation and subsequent permitting, EAO concludes that there will not be a significant adverse cumulative effect on the aquatic environment.

Conclusions

EAO considered the comments received from First Nations and government agencies throughout the EA process, including the pre-Application stage, regarding the adequacy of the baseline information and associated analysis. EAO recognizes that the Proponent engaged in iterative issues resolution and provided detailed responses to issues raised.


EAO also recognizes the Proponent will be required to engage First Nations and technical reviewers (as appropriate) in the development of Management Plans listed in the EA Certificate, which will allow for continued discussion on mitigation and monitoring opportunities beyond the EA. Regardless, EAO recognizes that continued uncertainty related to the potential for adverse effects may not be fully resolved through future management actions. EAO recognizes that if the Project were to proceed, permitting required through the Mines Act and the Environmental Management Act would continue to address outstanding uncertainty.

Although reasonable efforts have been made in the EA assessment work, the level of conservatism in the predicted water quality is uncertain and there is potential that underground water quality and potential effects to VC’s in Murray River could be under predicted (in particular selenium and sulphate).

An important related matter is the effects on groundwater from subsidence. EAO recognizes the uncertainty in the magnitude, extent, and impact resulting from subsidence on groundwater and concludes that subsidence will contribute to adverse effects on groundwater quality and quantity.

Considering the above analysis, and having regard to the conditions identified in the legally binding Table of Conditions, EAO is satisfied that the Project’s residual adverse effects on groundwater would not be significant adverse effects.

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Murray River Technical Report GROUNDWATER AND … 1... · along natural flow paths to the Murray River. The travel time of contact groundwater depends on several factors including