11. Description of the Landfill (Solid Waste Disposal ...svc028.wic009tp.server-web.com/iis/V2/V2b_part11.pdfreceive waste from the pulp mill only. It is not for use by the public,

11. Description of the Landfill (Solid Waste Disposal Facility), Quarry and Water Reservoir

11.1 Overview

A solid waste disposal site, quarry and water reservoir are proposed to the north east of the East Tamar Highway.

The landfill will accept all waste except hazardous waste generated during construction and operation of all components of the pulp mill and ancillary infrastructure.

The quarry will provide construction material for the pulp mill and wharf in the event that there is a shortfall of fill from the mill site.

A water reservoir is proposed for water supply for the operation of the pulp mill.

A detailed description of these facilities is provided below and their detailed location is shown in Figure 12-1.

11.2 Landfill

11.2.1 Overview

Pitt and Sherry (2006a) prepared a Solid Waste Landfill Conceptual Design report. This forms the basis of the design description and some impact areas for this section. A copy of the report is provided in Appendix 55, Volume 16.

A landfill is proposed to be constructed in the northeast corner of a site east of the East Tamar Highway. Refer to Figure 11-1 for the proposed location. A new landfill facility is required as the existing municipal facilities at George Town are inadequately sized and are facing closure. Alternative facilities at Launceston are prohibitive given the costs of transport and the significant burden such a quantity of material will place on the landfill.

The design capacity of the landfill is 1.1 million cubic metres and has a design project life of 20 years. There is room on the site for expansion of the landfill to extend the project life to 50 years. The landfill will receive waste from the pulp mill only. It is not for use by the public, other industry or municipalities.

11.2.2 Waste Types

During the construction and operation of the pulp mill, a range of waste types will be generated. Waste types are:

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Table 178: Waste Types

Waste type Waste classification* Approximate quantity per year

5,000 m3/y Solid waste – domestic type Putrescible

11,000 m3/y boiler ash Solid waste – boiler ash Controlled waste

40,000 m3/y Solid waste - green liquor process dregs, slaker sands and lime kiln electrostatic precipitator dust

Controlled waste

56,000 m3/year Total

* Pursuant to the DPIWE Landfill Sustainability Guide 2004 and the National Environment Protection Measure (Movement of the Controlled Waste between States and Territories) 2004.

The landfill has been designed to accept all solid wastes (worst case scenario) such as boiler ash, green liquor process dregs, slaker sands and lime kiln electrostatic precipitator dust. The solid wastes are primarily inorganic in nature and relatively benign.

Approximately 220 t of hazardous waste will be generated annually. This will consist of used lubrication and hydraulic oils, used electrical equipment and various maintenance chemicals and materials. All hazardous waste will be transported to an established landfill approved for that purpose. The likely landfill for hazardous waste will be Remount Road, in Launceston. These materials will be handled, stored and disposed of in accordance with relevant Australian Standards and the requirements of EMPC (Waste Management) Regulations.

Based on the available chemical and physical information on the pulp mill solid wastes requiring disposal, it is proposed to co-dispose the green liquor dregs, lime slaker sand, lime kiln electrostatic precipitator dust and combined boiler ashes. Co-disposal of the wastes will maximise landfill space and minimise solid waste volumes.

The pulp mill wastes for disposal will be weighed and mixed at the pulp mill.

It is estimated that the mixed waste will have a moisture content of up to 50 % with typical solid sizing in the millimetre range for process dregs, slaker grit and fly ash, and typical solid’s sizing of <0.1 mm for the lime kiln electrostatic precipitator dust and fly ash.

The mixed solid waste will consist primarily of calcium and sodium hydroxides and silicates, carbonates with some phosphates and unhydrolysed oxides. The chemical characteristics of the wastes suggest no significant likelihood of adverse reactions between the waste types (apart from an initial and temporary heat of reaction due to lime hydration). Nevertheless, the nature of the process wastes necessitates cell lining and leachate collection.

Domestic waste produced at the mill site (eg. canteen and sanitary waste) will be disposed of to dedicated smaller internal cells inside the main waste cells, thereby using the cell lining and the leachate collection system of the parent cells.

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BELLBAYLINE

BELLBAYLINE

EASTTAMARHIGHWAY

495000

495000

5445000

5445000

Bell Bay Pulp MillIntegrated Impact Statement

LegendPulpMillProjectSiteBuiltupAreaWorkersAccommodationQuarryWaterReservoir

RiverOutfallWaterSupplyPipelineEffluentPipelineLandfillBoundary

RailwayDamGasPipe-LocalLeachatePipelineTransmissionLine

RoadsNational/StateHighwayMajorArterialRoadArterialRoadAccessRoadMillLayout

FIGURE11-1LANDFILLLOCATION

_̂LAUNCESTON

HOBART

Date:16/06/06Projection:MapGridofAustraliaZone55,GDA94Source:Basedatasourcedfrom

CData2001andLIST-www.thelist.tas.gov.au,allotherinfrastructuresuppliedbyGunnsPtyLtdFile:M:\41\14346\gis\map\final\vol_1\fig12_1_landfill_location.mxd

090

180270

360450

Metres

1:15,000

-

During the construction phase of the pulp mill, construction waste will also need to be disposed of. Gunns will maximise the recycling of construction waste but estimate that there will be a residual 25,000 m3 of unrecyclable construction waste that will need to be disposed of in the landfill. This will be inert material. It will not require a cell liner or leachate collection, and the cell design for the construction waste will therefore be much simpler than it will need to be for process waste. George Town Council has advised Gunns that due to disposal area constraints, the George Town Tip is unable to accept any inert or putrescible waste from the pulp mill project (per comms Gunns).

Domestic waste will also be produced during the construction phase from the workers’ accommodation facility that will be established in George Town. It is estimated (Pitt and Sherry, 2006a) that a total of 5,000 m3 (before compaction) of this type of waste will be produced. The disposal needs for waste produced during the construction phase will arise well in advance of the need to dispose of process waste. If the accommodation facility’s domestic waste was disposed of to the landfill, the landfill’s leachate collection system will need to be constructed and operational approximately 3 years before the system was required for the process waste. Because the 5,000 m3 of domestic waste from the workers accommodation facility is relatively small (particularly when compaction is allowed for), it is considered to be more efficient and cost effective to take this waste to an established landfill, probably Remount Road.

In summary, the waste that will be disposed of in landfill comprises approximately:

A total of 25,000 m3 of construction waste during the construction phase

Up to 51,000 m3/year of process waste during the operational phase

Up to 5,000 m3/year (before compaction) of putrescible waste during the operational phase.

Following approval of the project, detailed design of the landfill will be undertaken.

11.2.3 Waste Recovery

The solid process waste produced by the pulp mill will come primarily from minerals in the raw wood, from the unusable fraction of limestone and from other impurities in process inputs.

The solid process wastes are boiler ash, green liquor process dregs, slaker grits (sand) and lime kiln electrostatic precipitator dust.

Boiler ash is inorganic (mineral) residue left from the combustion of wood in the plant’s boilers.

Green liquor dregs are nonreactive and insoluble materials left after smelt (inorganic process chemicals) from the recovery furnace is mixed with water. They consist of carbonaceous material and compounds of calcium, sodium, magnesium and sulphur.

Lime sludge is produced when lime is mixed with green liquor to produce white liquor through a recausticising process. The lime kiln converts this sludge into lime with a high content of active calcium oxide. Slaker grits are made of overburned and/or underburned lime that is produced in the lime kiln. The grits contain sodium, magnesium and aluminium salt.

The lime dust from the lime kiln will be recovered with an electrostatic precipitator. Depending on the final selection of the recausticizing equipment, the non-process elements (NPE) from the chemical recovery

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system (lime kiln and recaustisization) are purged out, either with lime kiln dust or through the pre-coat lime of the dregs filter.

Collectively, the process wastes from a Kraft mill are caustisizing materials with a pH of at least 11, containing varying proportions of calcium, aluminium, iron, sodium, potassium, sulphur, magnesium and chlorine, with calcium the predominant component (RMT Inc, 2003).

Caustisizing materials generally do not exhibit a significant environmental hazard, typically having low concentrations of heavy metals and no RCRA corrosivity or toxicity (RMT Inc, 2003).

Beneficial use methods for causticizing residuals tend to take advantage of the calcium content and/or alkalinity of these materials. The USA National Council for Air and Stream Improvement has reviewed potential beneficial uses for pulp mill solid process wastes as follows (RMT Inc, 2003):

Soil amendment: Land application is the most commonly practised beneficial use for causticizing materials, with lime mud being the material that is most commonly used as a soil amendment. The residuals serve as liming agents, replacing agricultural limestone as a means of raising soil pH to a range that enhances crop production. Causticizing residuals tend to neutralize soil more rapidly than agricultural limestone because they generally consist of smaller particles. Causticizing materials have also been successfully applied as a forest soil amendment. They have been shown to raise the pH of acidic soil and promote the growth of trees.

Alternative daily cover: Lime slaker grits have been successfully used as an alternative cover material to the traditional (15 cm) of daily soil cover used for active faces of a landfill. The use of grits as an alternative daily cover helps to control blowing litter, animals, and insects at the landfill.

Raw material in cement manufacturing: Causticizing materials are utilized as feedstocks in the production of cement. The basic raw materials required to make cement are calcium, silicon, aluminium, and iron. Causticizing materials have high percentages of calcium, aluminium, and iron, and if properly washed (as is the norm), they generally are low in constituents that can negatively impact the production and quality of cement, such as sulfur and sodium.

Soil stabilization: Soil stabilization is the alteration of soil properties to improve the chemical or engineering performance of the soil. Lime slaker grits have generally been used in this application. Lime slaker grits, when mixed with sand and compacted in lifts, have been shown to handle heavy truck traffic better than typical soil surfaces. Lime slaker grits has also been shown to be effective as a dust suppressant on unpaved roads. While the dust from the grit/sand roads is finer than that produced from native soil roads, the grit has a better liquid holding capacity, which improves efficiency for dust suppression techniques.

Fine aggregate in asphalt paving: Lime mud, lime slaker grits, and green liquor dregs have been used successfully as a substitute for fine aggregate in hot mixed asphalt.

Other: Causticizing materials have also been used in surface mine reclamation, for feedstock in compost, as an admixture to hydraulic barrier material, as a settling aid in wastewater treatment, for pH adjustment of process water, and as an ingredient in manufactured soil.

Firm reuse opportunities for process waste from the Gunns’ pulp mill will depend on the demand for that material within economic and environmentally efficient transport distances from the mill site.


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11.2.4 Leachate Characteristics

The landfill will produce leachate as a result of moisture in the process waste, and rainwater infiltration. Conceivably, there could also be some infiltration from water sprayed for dust suppression but the great majority of this is more likely to evaporate than infiltrate. The leachate will vary in strength and volume depending on many factors, including waste type and properties, size of landfill, age of landfill and landfill cover design.

Based on the information available, including experience in Finnish pulp mills, the leachate quality should have the following chemical properties:

Relatively high pH of approximately 9.5 to 12;

Potential saturation with calcium hydroxide;

Dissolved heavy metals and metalloids at elevated pHs; and

Elevated electrical conductivity and dissolved solids.

The chemical analysis of the leachate will depend on the relative mix of wastes and also on the amount of rain infiltration into uncovered waste. Indicative leachate parameters are provided in Table 179.

Table 179: Typical leachate quality expected

Parameter Range Units oC Temperature 10 – 25

pH 9.5 – 12

Conductivity 200 – 2500 mS/m

Total suspended solids 50 – 1000 mg/L

Chemical oxygen demand 200 – 2200 mg/L

Biological oxygen demand 50 – 500 mg/L

Total phosphorus 1 – 15 mg P/l

Total nitrogen 5 – 30 mg N/L

Sodium 2000 – 5500 mg/L

Chloride 500 – 1500 mg/L

Sulphate (SO4) 100 - 500 mg/L

Phenol 0.05 – 0.25 mg/L

Cadmium 0.00005 – 0.0005 mg/L

Mercury 0.0001 – 0.0003 mg/L

Lead 0.0004 – 0.006 mg/L

Zinc 0.03 – 0.08 mg/L

Cobalt 0.002 – 0.005 mg/L

Molybdenum 0.03 – 0.08 mg/L

Nickel 0.02 – 0.031 mg/L


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Leachate quantities will vary throughout the life of the landfill. When the first landfill cell is commissioned, practically all of the incident rainfall onto the open cell will flow directly to the leachate collection system.

As the waste builds up in the first operating cell, some of the rainfall will be absorbed by the waste until saturated, which will significantly moderate the leachate flow from the cell.

As the landfill cells are filled and closed, the quantity and quality of leachate produced will fluctuate.

For the overall leachate design, the volume of leachate from an open active cell plus that from the closed cells needs to be considered.

11.2.5 Landfill Design

Design Criteria

Due to the waste type classifications, the landfill is subject to Category C design criteria (secure landfill) under the DPIWE’s Sustainability Guide for the Siting, Design, Operation and Rehabilitation of Landfills, 2004.

The main landfill design criteria are summarised as follows:

Achieve the design volumes for the three different types of waste (construction waste, process waste and domestic waste);

Minimise the amount of rainfall collected and leachate produced by the developing landfill;

Minimise the amount of solid waste to be disposed of to the landfill;

Minimise the area of the landfill;

Develop the landfill progressively using individual cells with a nominal 100,000 m3 capacity;

Fully cover individual cells as filled;

Utilise favourable geological and geographical features in the design; and

Incorporate a cell liner design and cover that minimises risks to the receiving environment (Pitt and Sherry 2006a).

Other considerations such as surface water quality, drainage, leachate and groundwater are addressed in the design.

Landfill Design

The landfill will be located in a gently sloping gully near the headwaters of Williams Creek, as shown in Drawing H05069-R1 in Appendix 55, Volume 16. The floor and sidewalls of the gully in the landfill area are generally less than 5 % slope.

Natural constraints on the landfill size include a saddle to the northwest and two drainage lines running from the east above and below the site, and potential visibility from roads, tourist lookouts and residential areas. To achieve the required landfill volume within these constraints, a two-layer design will be used.


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The layout of the landfill minimises its visibility. Line of sight details are provided in Appendix 55, Volume 16, show that the landfill will not be visible from the key vantage points of the Mount George scenic lookout and the Batman Highway. It is also unlikely to be visible from the East Tamar Highway. Although a sight line (number 3) from the highway looking north intercepts the landfill, the natural tree coverage in front of the landfill is likely to screen it from view.

The landfill will consist of one construction waste cell of 25,000 m3 capacity and up to 10 process waste cells, each with an average of 100,000 m3 capacity and a surface area of up to 23,500 m2. Individual cells will be constructed, operated and closed progressively.

The first cell will be constructed at the upper end of the landfill site.

Two layers of cells will be constructed. The lower layer will be constructed first and will consist of the construction waste cell and four process waste cells. The upper layer will consist of six cells constructed on top of the four lower layer process waste cells following their closure.

The construction waste cell’s wall will stand on natural ground. The lower layer process waste cell walls will also stand on natural ground. The upper layer process waste cell walls will stand on the compacted clay capping of the lower cells, which in turn sit on the compacted process waste. Because of the fine grain size and the homogeneity of the process waste, the lower process waste cells will provide a stable platform for the upper cell walls.

Appendix 55, Volume 16 describes process waste characteristics. The process waste will have a specific density of 1000 kg/m3. This is greater than the DPIWE Landfill Sustainability Guide minimum compaction requirement for secure landfills of >850 kg/m3, even without compaction. Compaction by earthmoving equipment will increase this waste density further. Putrescible waste will be compacted by earthmoving equipment to achieve the DPIWE Landfill Sustainability Guide minimum compaction requirement for putrescible waste of >650 kg/m3. The compaction requirements will be specified as part of the geotechnical considerations for the detailed design of the landfill.

The conceptual design avoids having any cells sitting on top of the construction waste cell. The waste in this cell will by its nature be difficult to compact well enough to provide a secure platform to construct over. The construction waste cell will therefore be structurally independent from the process waste cells, apart from incidentally providing an upslope headwall for the first process waste cell of each layer.

The construction waste will be inert and benign but will be of various shapes, sizes and materials. Waste destined for this cell will be residual waste that cannot otherwise be reused or recycled. It is therefore not possible to identify a particular filling sequence for the construction waste - waste will be placed in the cell as it arises. However, to all practical extents, waste will be placed in the cell to minimise the creation of large voids that could cause instability. Waste will be compacted by running heavy machinery over it, and will be progressively covered with earth to assist stabilisation and to minimise use of voids by vermin. On final closure, the construction waste cell will be capped and revegetated.

Both layers of the landfill will be constructed in a sequence from upslope to down-slope to minimise the size of the cell catchments and hence minimise ingress of surface water into the cells. Each layer will have its own leachate collection system. A schematic layout of the first and second layers of the landfill is shown in Figure 11-2 and Figure 11-3 respectively. More detail is provided in Drawings in Appendix 55, Volume 16.


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A cell of 100,000 m3 volume will take approximately 2 years of process waste if there was not waste reuse. I

The two-layer design means that very high cell walls are not required. Higher cell walls take up an exponentially greater volume of otherwise useable air space. The two-layer design optimises the use of available air space.

Source: Pitt and Sherry, 2006a

Figure 11-2 Schematic Layout of Landfill Layer 1


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Source: Pitt and Sherry, 2006a

Figure 11-3 Schematic Layout of Landfill Layer 2

11.2.6 Cell Design and Leachate Management

A schematic diagram of the arrangement of layers for leachate containment and collection and cell capping is provided in Figure 11-4.

Process waste cells will be in two levels, and the cross-section of the upper level cells will be different to that of the lower level cells. The conceptual design of each level is shown in Drawings H05069-R10_1 and H05069-R11_1 in Appendix 55, Volume 16. The conceptual design will form the basis for detailed design.


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Prepared native clayGeosynthetic clay liner

HDPE membrane

Washed stone aggregateProtective geotextile (nonwoven)

Protective waste/sand mix

Witness sump (at downstream end of cell)

Leachate drain (through whole length of cell)

Daily coverHDPE membrane

Drainage sandNative clay

TopsoilShallow rooted native vegetation

Process waste Putrescible waste

150 mm 1 mm

150 mm 1 mm

300 mm 6 mm 1.5 mm

300 mm

150 mm 300 mm 450 mm

Geotextile (nonwoven)

1 mm

Figure 11-4 Schematic layers of landfill process waste cell base and cap

It is possible that the cell(s) at the lower end of the landfill may be exposed to an approaching water table during weather wetter than that which occurred prior to the conceptual design site investigations. If this risk were significant, an additional drainage layer will be constructed underneath the bottom liner of that cell. The risk to the upper cells of an approaching water table is negligible.

Under the conceptual design, construction of the lower cell will not occur until approximately 8 years after the commencement of operations. During that period, regular monitoring of groundwater levels will be undertaken as part of routine operations, and the risk will therefore be well quantified. An appropriate drainage layer could therefore be designed well in advance of it being needed. The thickness of any required drainage layer will be determined by the demands of a calculated 1 in 100 year flow.

The density of the overlying cell layers and waste, and the ability of the geosynthetic clay liner to withstand deformation, will mean that even in exceptional flows greater than the 1 in 100 year expectancy, any impact on the integrity of the landfill will be unlikely to be significant. The most likely consequence of an exceptional flow, if indeed it posed a risk at all, will be for the water table to rise either side of the landfill and seep into the landfill cutoff drains, to be taken away as surface flow.

An additional or alternative means of releasing an accumulation of groundwater below the cell could be to install drainage groundwater bores lower down the gully. These bores could drain passively and/or be pumped out when necessary to relieve any build up of hydrostatic pressure. Such a system could be supported by the installation of pressure transducers underneath the liner. This will be considered as part of the detailed design.


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Leachate Collection

A composite geosynthetic and membrane liner will contain the process and domestic waste and associated leachate for each cell. Leachate will be collected in each cell of both the lower and upper landfill layers and then directed to the leachate sump, from where it will be pumped to the mill’s wastewater treatment plant. The leachate will not present any problems for the wastewater treatment plant. The high pH of the leachate will slightly reduce neutralization chemical use in the treatment plant due to the effluent being slightly acidic.

Construction waste cells

The construction waste will be inert and leachate collection from this cell is therefore not required. However, a drainage system will be required, to take away internal cell drainage that would otherwise accumulate behind the cell wall, particularly while the cell is open and uncapped.

Initially, pending the construction of the first process waste cell and hence the leachate drainage system, the drainage collection system of the construction cell will simply be piped through the cell wall to a sediment trap and energy dissipater, allowing drainage to continue to run along the natural drainage line without causing erosion. When the first process cell is constructed (immediately down-slope of the construction waste cell) the drainage collection pipe from the construction waste cell will be connected to the head of the leachate collection system in the process waste cell.

Following capping of the construction waste cell, its drainage system will continue to remove any rainfall that percolates through the capping.

Lower layer process waste cells

The undersurface of the process waste cells will be prepared from native (ie. in situ) clay ripped to a depth of approximately 300 mm and compacted to provide a smooth surface, free of sharp rocks that might puncture the overlying geosynthetic clay liner.

The 6 mm thick geosynthetic clay liner will be unrolled and laid in overlapping panels onto the prepared base. A 1.5 mm HDPE membrane will then be laid on top of this. This membrane is the primary barrier to leachate escape. The geosynthetic clay liner is a secondary barrier against any leakage through perforations in the membrane. The membrane will then be covered with a protective geotextile (non-woven) to reduce the potential for the overlying aggregate to puncture the membrane.

A 300 mm layer of crushed stone aggregate will be laid on top of the membrane to provide a leachate drainage layer. The leachate collection pipe network will be positioned at the bottom of this layer.

The drainage layer will be covered with a 1 mm geotextile (non-woven) layer to prevent overlying fines clogging drainage spaces. The geotextile will be covered with a 150 mm layer of protective mix of waste and sand (proportioned to achieve a driveable surface for waste delivery trucks and the waste spreading machinery). Waste will then be deposited and spread over the top of the protective layer. Because the leachate is likely to be saturated with calcium salts and have a pH of up to 12, there is a potential for post-precipitation of calcium salts (carbonate, sulfate, phosphate and hydroxide) onto the geotextile liner surface or in the pores of the geotextile. Lime dust might similarly move onto the geotextile surface or into its pores. These effects could bind the geotextile and restrict movement of leachate down into the


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collection system. This risk will be mitigated by use of a geotextile with an appropriate fabric structure and pore size.

A conceptual design of the leachate collection system is provided in Appendix 55, Volume 16.

The PVC leachate collection pipe will be a heavy walled 300 mm spine with 150 mm feeders running obliquely outwards and slightly uphill to the extremities of the cell in a herringbone pattern.

The main cell leachate collection will service indirectly the internal 'domestic' type waste cell also, thus keeping the leachate system simpler and reducing infrastructure costs. A sump will be installed towards the lower section of the cell underneath the leachate collection pipe to collect any liner leaks and monitor the effectiveness of the cell liner and leachate containment system.

As the landfill cells are developed downhill, the leachate collection system will be developed progressively.

The sump will only be extended through the cell wall to the next cell. Each individual cell will contain its own sump that eventually will be buried by that cell’s successor.

A main leachate collection pipe will be progressively installed down the centre of the landfill’s lower layer as the four lower layer cells are sequentially operated and closed out. Offshoots outwards from the main leachate collection pipe approximately every 25 m towards the extremity of each individual cell will ensure control of the phreatic zone throughout the cell.

Upper layer process waste cells

The six upper layer cells will have two leachate collection pipes on either side of the upper level cells due to the final surface slopes of the underlying cell. Inward offshoots from these leachate collection pipes approximately every 25 m will ensure control of the phreatic zone throughout the cell.

The leachate collection pipe(s) will be piped from the landfill footprint to a buffer storage tank(s), downstream of the landfill. The tank(s) will serve as a monitoring site and moderate leachate flows to the pulp mill effluent treatment system. The tank(s) will have an emergency overflow to Williams Creek.

The tank(s) will be sized to store at least a nominal day’s worth of landfill leachate, so that the landfill leachate can be removed from the pulp mill effluent treatment plant during preventative or corrective maintenance or other effluent treatment plant offline times.

Leachate will be treated in the mill’s wastewater treatment plant. The nature of the wastes means that there is little risk of significant environmental harm or nuisance at the landfill site (or even at the wastewater treatment site). It is possible that oils in the domestic leachate could react with caustic in the process waste, leading to some saponification but the high water hardness should moderate frothing if that occurs. If there are high dissolved ammonium salts in the waste, ammonia could be produced at high pH, potentially causing odour. High pH could also cause metals to precipitate out as hydroxides. None of these products, however, are problematic, and they will be dealt with at the treatment plant.

Metal sulphides, such as calcium sulphide and sodium sulphide, will exist in very small quantities in the process waste. In acidic conditions, these sulphides are potentially sources of hydrogen sulphide (H2S), which is a malodorous gas. However, calcium sulphide and sodium sulphide are stable at the high pH of the process waste and its leachate. In any event, the total quantities of metal sulphides present in the


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process waste will be too small to cause environmental nuisance at this remote location. Although the sulphides could dissolve in the leachate and be carried into the mill’s wastewater treatment plant, this plant will not have acidic conditions, thereby preventing the production of hydrogen sulphide.

11.2.7 Capping

Each cell (including the construction waste cell) will be capped with multiple layers to reduce rainfall infiltration, and hence leachate generation.

Construction waste will be left uncovered until the construction waste cell is no longer required, which is expected to occur prior to or soon after the commencement of operations and hence the commencement of process waste production.

Process waste will be progressively covered as it is deposited with a 150 mm intermediate cover of locally sourced soil and/or clay, which will act as a dust suppressant and, in the case of the putrescible waste, a barrier to odour and nuisance fauna. This intermediate cover will be compacted to assist with reducing rainwater infiltration but it is not intended to be a primary rain barrier.

When a process waste cell reaches its fill capacity, the intermediate cover will be overlaid with a 1 mm HDPE membrane, which will be the primary rain barrier. A 150 mm drainage layer of sand will be placed over this membrane, followed by a 300 mm layer of compacted native clay and then 450 mm of topsoil. The construction waste cell will be capped similarly.

Shallow rooted native vegetation will be planted to bind the topsoil and assist with waterproofing.

The capping will slope at approximately 5% to direct surface water into the landfill’s cutoff drains.

11.2.8 Leachate Volumes

Potential leachate volumes have been calculated using HELP (Hydrological Evaluation of Landfill Performance) (Qian et. al., 2002).

At this conceptual design stage, calculations were performed for an assumed unit process waste cell having a surface area of 1 hectare in either an uncapped or a capped state. More detailed modelling will be undertaken during the detailed design stage.

Modelling used a simulated 20 - year set of weather data, created by Visual HELP’s Weather Generator. The Weather Generator creates synthetic daily precipitation over the nominated period (in this case 20 years) by adding statistical variation around a core set of actual weather observations. The core set used was the Bureau of Meteorology’s records for Low Head. The simulated temperature and rainfall data sets are shown in Appendix 55, Volume 16.

A summary of the modelling results is provided in Table 180 for an uncapped cell and Table 181 for a capped cell. The full modelling report is provided in Appendix 55, Volume 16.


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Table 180: Uncapped - Estimated water balance for a nominal 1 hectare landfill cell in an uncapped state

Over 20 yearsa

% of rainb Annual averagec

Daily averaged

Peak dailye

Precipitation m3 89262.0 100 % 4463.1 12.23 392.0

Runoff m3 983.8 1.1 % 49.2 0.13 176.8

Evapotranspiration m3 37618.0 42.1 % 1880.9 5.15 -

Collected leachate m3 48738.0 54.6 % 2436.9 6.7 22.8

Leaked leachate m3 48.4 0.1 % 2.4 0.007 0.02

a: The 20 year period is for the purposes of weather simulation only. Any given cell will only be open for approximately 2 years.

b: The amount as a percent of precipitation c: The 20 year accumulated total divided by 20 d: The annual average divided by 365 e: The peak daily volume over the 20 year simulated data set

Table 181: Capped - Estimated water balance for a nominal 1 hectare landfill cell in a capped state

Over 20 yearsa

% of rainb Annual averagec

Daily averaged

Peak dailye

Precipitation m3 89262.0 100 % 4463.1 12.2 392.0

Runoff m3 10.6 0.01 % 0.5 0.002 10.2

Evapotranspiration m3 84561.0 94.7 % 4228.1 11.6 -

Collected leachate m3 1867.8 2.1 % 93.4 0.26 0.33

Leaked leachate m3 4.0 0.005 % 0.2 0.0006 0.0009

a: The 20 year period is for the purposes of weather simulation.

b: The amount as a percent of precipitation c: The 20 year accumulated total divided by 20 d: The annual average divided by 365 e: The peak daily volume over the 20 year simulated data set

Collected Leachate

The expected daily average volume of leachate collected by the drainage system of a nominal 1 hectare process waste cell during its uncapped state is 6.7 m3, with an expected peak daily volume of 22.8 m3.

The expected daily average volume of leachate collected by the drainage system of a nominal 1 hectare process waste cell during its capped state is 0.26 m3, with an expected peak daily volume of approximately 0.33 m3.


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At the full operating development of 9 closed cells and 1 remaining open cell, the estimated average daily volume of collected leachate is therefore 6.7 + (9 x 0.26) = 9.0 m3, with a peak daily volume of 22.8 + (9 x 0.33) = 25.8 m3.

These average and peak daily volumes at full development correspond to flow rates of 0.1 L/s and 0.3 L/s respectively.

These rates are 3 orders of magnitude less than the capacity of the 300 mm leachate collection pipes that will be used.

Leaked leachate

The expected daily average volume of leachate leaking through the bottom liner of a nominal 1 hectare process waste cell during its uncapped state is 0.007 m3, with an expected peak daily volume of 0.02 m3.

The expected daily average volume of leachate leaking through the bottom liner of a nominal 1 hectare cell during its capped state is 0.0006 m3, with an expected peak daily volume of approximately 0.0009 m3.

At the full operating development of 9 closed cells and 1 remaining open cell, the estimated average daily volume of leaked leachate is therefore 0.007 + (9 x 0.0006) = 0.01 m3, with a peak daily volume of 0.02 + (9 x 0.0009) = 0.03 m3.

These average and peak daily volumes at full development correspond to leakage rates from the fully developed landfill of 10 L/day and 30 L/day respectively.

Post-closure

Following the complete closure of the landfill (ie. all 10 process waste cells closed and capped), the average and peak daily leachate collection rates will be 10 x 0.26 = 2.6 m3 and 10 x 0.33 = 3.3 m3, ie. 2600 L/d and 3300 L/d or 0.03 L/s and 0.04 L/s respectively.

Following the complete closure of the landfill (ie. all 10 process waste cells closed and capped), the average and peak daily leachate leakage rates will be 10 x 0.0006 = 0.006 m3 and 10 x 0.0009 = 0.009 m3, ie. 6 L/d and 9 L/d.

11.2.9 Landfill Gas Management

The main process wastes to be disposed of to the landfill are inorganic and inert (eg. green liquor dregs, lime slaker and lime kiln electrostatic precipitator solids and boiler ash etc.). No green wastes will be disposed of to the landfill. All wastes with a calorific value will be reused as fuel for power production.

The waste type with the potential to produce gas is the domestic waste. The domestic waste will be placed in each of the ten individual process waste cells in a separate dedicated cell for each main cell.

There will therefore be 10 separate domestic waste cells, one each in the 10 process waste cells. The annual production of domestic type waste will be approximately 760 t/a or 5,000 m3/a (a bulk density of


Bell Bay Pulp Mill

0.15 before compaction). This amounts to approximately 10% of the maximum amount of wastes for disposal, ignoring compaction.

Each domestic waste cell will have a gas discharge pipe installed after final capping to prevent gas build up under the cap. Given the volume of domestic waste stored in each individual domestic cell, gas flaring is not proposed and the amount of gas generated will be small and will have negligible commercial value. Landfill gas collection will not be economic, and will not be undertaken.

11.2.10 Surface Water Management

As no water quality data are available to establish site-specific water quality objectives for Williams Creek, the State Water Policy defers to the trigger values outlined in the ANZECC Guidelines (2000) for the protection of 95% of aquatic ecosystems.

Provided that the water quality of the surface waters flowing through the landfill complies with the ANZECC trigger values for Protected Environmental values (PEVs), the State Water Policy will be satisfied. If any trigger value is exceeded, a risk assessment will need to be undertaken to determine what, if any, management action is necessary.

Diversion

Designing an appropriate surface water management system is of primary importance when a landfill location impinges on natural watercourses. The location of the landfill and its design has endeavoured to minimise interference to the natural waterways in the area.

The area of natural drainage that reports to Williams Creek and requires diversion around the western and eastern sides of the landfill is approximately 20 and 64 ha respectively. The area of natural drainage that reports to Williams Creek and requires diversion at the lower eastern end of the landfill is approximately 198 ha. These catchment areas were determined from 1:25000 site topographic maps.

Surface water diversions are a key component of the landfill layout.

A permanent surface water cut off drain will be installed along the western side of the ultimate landfill footprint adjacent to the access road and along the eastern side of the landfill adjacent to the ultimate landfill footprint. These drains will also collect diverted surface water from above and to the east of the landfill.

A permanent surface water diversion drain will be installed to divert surface water from a relatively large (but still ephemeral) drainage line flowing from the east at the lower end of the landfill.

The above surface water infrastructure will remain for the life of the landfill and will be integral to the final close out plan for this area of the landfill. The surface water diversion drains will be directed at an appropriate velocity and slope back into the natural Williams Creek watercourse below the landfill footprint.

The drains will be designed to handle a 1:50 year rainfall event at the nominal time of concentration for the individual catchments. The drains will be designed and constructed to appropriate design standards and for ease of ongoing maintenance.


Bell Bay Pulp Mill

During the operation of the lower layer of cells, temporary drains closer to the boundary of those cells will be installed, in addition to the ultimate outside permanent drains.

The DPIWE Landfill Sustainability Guide specifies design criteria for surface water management for a 1:50 year storm event of 24 hours duration.

The intensity of rainfall and associated surface water flow rates from a 24 hour duration storm may not be indicative of good engineering design for different locations.

For the catchments mentioned above, the time of concentration (overland flow time) for surface waters reporting to or around the landfill area is approximately 30 minutes. Using the more appropriate 30-minute rainfall event for design purposes (which gives much higher rainfall intensities and hence flow rates), the surface water cut off drain on the western side of the landfill must be able to handle 100 L/s. The surface water diversion and cut off drain on the upper eastern side of the landfill must be able to handle 3,500 L/s. The surface water diversion drain on the bottom eastern side of the landfill must be able to handle 9,000 L/s (Pitt and Sherry 2006a).

The calculations for the above information are contained in Appendix 55, Volume 16.

The conceptual design is for the permanent earth drains to be cut into the natural ground around the landfill with nominal dimensions of 2 m wide by 1 m deep and 45° sides with nominal downhill slopes of 1%.

The flow that such a drain could handle has been calculated at approximately 7,500 L/s. This design is more than enough for the western and upper eastern drains. The lower eastern drain has a slope of approximately 10% and at this slope the flow capacity of the 2 m x 1 m drain is approximately 24,000 L/s, which is also more than adequate (Pitt and Sherry, 2006a). Further detail on surface water drainage is provided in Appendix 55, Volume 16.

11.2.11 Groundwater Management

Based on preliminary geotechnical information, the siting of the landfill will not interfere with current groundwater movement. The watertable level is approximately 16 m below the surface level at the landfill area at its top end but may be less than 5 m below the surface at its lower end.

The landfill leachate quality has the potential to affect quality of the groundwater, especially the pH and conductivity, in the event of a significant breach in the landfill liner’s integrity. However, the weathered soil between the landfill and the groundwater will attenuate the impact of any leachate lost from the landfill, and the effectiveness of this attenuation will depend on where the breach occurs. Attenuation will be much greater for a breach at the upper end of the landfill than for a breach at the lower end, although the concept design does not rely on this attenuation.

Based on the conceptual landfill design, the proposed liner and capping system, the underlying geology and the leachate collection system, the risk and therefore the requirements for groundwater management are minimal.

The adoption of the proposed landfill liner design will minimise the potential risk of ground water contamination and the extent of potential contamination in accordance with Section 24.1 of the State Policy on Water Quality Management 1997.


Bell Bay Pulp Mill

Permanent groundwater monitoring bores will be installed in strategic locations, above and below the landfill footprint, to monitor the groundwater levels and quality.

11.2.12 Hours of Operation

It is proposed initially to operate the landfill between 7 am and 5 pm, seven days a week. These hours may change as mill operations dictate.

The details that may affect the proposed hours of operation are:

Amount of waste produced; and

Amount of waste diverted to beneficial reuse rather than landfill disposal.

Number of trucks to be employed, truck capacities and frequency of the turn around at the landfill (taking into account the time required for spreading and compaction of the wastes). It is envisaged that only one truck will be needed to transport the amount of pulp mill solid waste for disposal, provided that the pulp mill solid waste generation rate is reasonably constant and that the pulp mill has solid waste storage capacity for weekend storage.

A work practices study after commencement of operation may recommend adjustments to the proposed operating regime.

11.2.13 Staffing

Approximately 10 truck loads per day, each carrying approximately 20 m3 per load will be required to be loaded at the pulp mill, carted to the landfill, unloaded at the landfill and spread across the open operating cell (10 deliveries per day x 20 m3 x 250 workdays/year = 50,000 m3 per year).

There will not be a permanent presence on site. Landfill operators will be on site on as as-required basis. It is envisaged that the staffing levels at any given time for the facility will be 2 people. One person will be the supervisor and direct operations. The other is likely to be a qualified plant machinery operator.

There will be a small crib room/office and workshop that will be opened and used as needed.

11.2.14 Waste Handling

To all practical extents, construction waste will be beneficially reused or recycled, rather than disposing of it to the landfill. Examples of this would be steel and other metals, packaging materials, timber pallets, glass and plastics etc. Only residual waste that cannot be reused or recycled will be taken to the landfill for disposal.

It is proposed to cool and wet the individual pulp mill process wastes prior to mixing and temporary storage in a dedicated storage area at the mill. The mixed process wastes will then be carted in covered trucks to the landfill site. The trucks will access the open operating cell by temporary gravel roads onto the previously spread and compacted fill.


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The individual waste layers will progress from the near roadside western side of the cell across to the western side of the cell. This will be achieved by having a truck tipping face about 0.5 m high established at the western side of the cell that will progress eastwards spreading over the entire area of the cell for each waste layer. The tipped waste will be spread and compacted level with the 0.5 m depth profile for the individual layer.

When putrescible waste is deposited in the landfill, it will be covered with at least 30 cm of soil and/or process waste at the end of the day to minimise odour generation and vermin infestation. To reduce disposal space wastage, the upper portion of this cover will typically be pulled back the next day (without disturbing the underlying waste) prior to depositing the next day’s waste, which in turn will be covered again.

11.3 Quarry

Gunns proposes to establish a quarry to provide construction material and road bases, road sheeting and crushed stone for the development of the Bell Bay site.

The quarry will be located north of the East Tamar Highway adjacent to the proposed landfill and water reservoir components of the project (Figure 11-1).

The quarry will only be established if there is insufficient dolerite resource required for the development of the Bell Bay site for the pulp mill and wharf.

The total reserve is estimated to be 180,000 cubic metres of dolerite. Production is proposed to be 100,000 cubic metres in the first year and approximately 20,000 cubic metres for the subsequent four years. The proposed rock extraction method is drill and blast. Blasting will be required.

It is proposed to carry out crushing and screening at the quarry.

A settling pond (approximately 25 m x 10 m x 2 m deep) will be maintained during operation to manage stormwater runoff from the site and any waters used for washing or screening.

The operation hours will be from 7 am to 7 pm during weekdays and from 8 am to 4 pm on weekends.

The quarry will be a Level 2 extractive industry and materials handling.

The quarry will be designed and operated to meet the requirements of the Quarry Code of Practice (QCOP). Following mining of the quarry, the quarry site will be rehabilitated in accordance with the QCOP.

Expolosives will be stored on site during site preparation. The storage of explosives on the site will be in licensed magazines which will comply with AS 2187.1-1998 and AS 2187.2-2006. Any Transport of explosives on public roads will comply with the Dangerous Substances (Safe Handling) Act 2005, Dangerous Substances (Safe Transport) Act 1998, the Dangerous Goods (Road and Rail Transport) Regulations 1998 and the Australian Code for the Transport of Explosives by Road and Rail.

Further details are provided in the completed Environmental Impact Information (EII) Mining and Extractive Industries form in Appendix 39, Volume 14.


Bell Bay Pulp Mill

11.4 Water Reservoir

11.4.1 Overview

Local water storage is required for a back-up water supply for the pulp mill in the event of an emergency such as the unlikely event of a water supply pipeline failure. Refer to Appendix 44, Volume 15 for details on water supply for the pulp mill.

The water reservoir will contain up to seven days of water consumption. For the production of up to 1.1 million of air dry tonnes of pulp per year this will require up to 670 ML of storage. Water allowances have been made for any possible further use by other industries along the pipe corridor.

Design Parameters of the Water Reservoir

The water reservoir will comprise an earth embankment constructed across a valley in the Tippogoree Hills immediately to the east of the mill site. It is located in close proximity to the proposed landfill and quarry (refer to Figure 11-1 for the proposed location).

Design parameters of the water reservoir are provided in Table 182.

Table 182: Summary of the Pulp Mill Site Water Reservoir

Item Design Basis

Embankment Level To RL 92.0 m maximum (to avoid overtopping to the east of the saddle)

Dam Top Water Level RL 90 m – providing 2.0 m freeboard

Lowest Operating Levels RL 85 m

Embankment Crest Lengths 460 m East and 370 m West

Embankment Crest Width 5.0 m

Maximum Wall Height 17.0 m (toe level at RL 75 m)

Upstream Wall Batter 1 vertical to 3 horizontal

Downstream Wall Batter 1 vertical to 2.5 horizontal

Construction Method Earth/rockfill embankment with 5.0m wide central clay core

Storage Capacity Up to 670 ML

200,000 m3Embankment Volume

Spillway Invert Level RL 90 m

Spillway Width 5 m

6.325 m3/s (0.8 m head) Design Flow

Source: GHD, 2005 (see Appendix 44, Volume 15)


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The water reservoir will be filled by gravity from the balance/control tank. Successful operation of this section will depend on air being prevented from entering the pipeline from the balance/control tank. This is best achieved by throttling the flow at the local site storage so that pipeline is always flowing full. It is proposed that an outlet flow control manifold be installed just upstream of the water reservoir. This valve will be actuated/regulated via a signal from the balance/control tank water level or from a pressure sensor in the outlet pipe just downstream of the balance tank. An alternative means of control would involve installing a flow meter just upstream of the valve manifold and regulating its setting based on a preset flow to achieve a fully drowned hydraulic grade line.

The above signals will be linked to a central pulp mill SCADA System.

The reservoir will not take any water from Williams Creek.

Final design of the dam will be subject to a detailed geotechnical investigation of the area; particularly with regards to sourcing clay and rock material. The water reservoir is likely to be considered a High B Hazard category. The relevant regulations under the Water Management Act 1999 require that dams of this hazard must be designed by an expert team.


Bell Bay Pulp Mill

Documents

11. Description of the Landfill (Solid Waste Disposal ...svc028.wic009tp.server-web.com/iis/V2/V2b_part11.pdfreceive waste from the pulp mill only. It is not for use by the public,