Stage 2F Acid Sulphate Soils Management Plan - Newcastle Coal ...

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Acid Sulfate Soil Management PlanTable 3Action Criteria for Assessing Soils with regard to Acid Sulfate Soil CharacteristicsTextureType of MaterialApproximateClay Content(%1000 tonnes disturbed)Sulphur Trail% Sulphuroxidisable(oven dry basis)Acid TrailMol H + /t Total(oven dry basis)Coarse Texture(Sands to loamysands)≤ 5 0.03 18 0.03 18Medium Texture(Sandy loams tolight clays)5-40 0.06 36 0.03 18Fine Texture(Medium toheavy clays and≥ 40 0.1 62 0.03 18silty clays)Source: after ASSMAC (1998).1 Mol H + /t = moles of hydrogen ions per tonne.The results of each sampling program will be compared with the Action Criteria provided in Table 3 to determine ifany treatment is required. Materials that are below the Action Criteria provided in Table 3 will be beneficiallyreused on-site. Material that is determined to be unsuitable for beneficial reuse on-site will be temporarilystockpiled on-site before being either treated and reused or transported to a licensed for treatment(Section 3.4.3).The characteristics of all soil materials will be recorded during excavation and movement on-site. Records willinclude a description of the excavated soil and the depth and location of its source and final placement.3.4.3 Treatment ProcessAs described in Section 3.1, during Stage 1 of the Project the sampling program only identified five samples asASS during construction works. One sample from dredged material was found to contain ASS and was returnedto the foreshore to prevent the material from oxidising. Laboratory analysis of two dredge material samples foundthe soils to be self-buffering, i.e. no treatment was necessary to minimise the ASS risk associated with oxidationof the soil. The soils were mixed with shell grit sand and allowed to break down without further treatment. Thesoil identified in the fourth positive sample was moved to the ASS treatment area and treated. The soil identifiedin the fifth positive sample was capped with a sealing layer to prevent oxidation.If required during Stage 2F of the Project, excavated soil identified as PASS or ASS will be temporarily stockpiledon-site before being either treated and reused or transported to a licensed facility for treatment. Treatment areaswill be bunded and have low permeability liners (e.g. compacted clay or geo-membrane). The treatment area willbe divided into a minimum of two areas separated by a bund wall. One area is for treatment and one forstockpiling the treated soils.The treatment area will require a settlement pond to collect any runoff. The settlement pond will be designed for a1 in 10 year, 1 hour storm duration capacity. Any runoff or fines collected in the settlement pond will requireassessment prior to decommissioning of the settlement pond.The control of acid generation from excavated soil will be achieved by neutralisation using lime, where required.There are numerous types of suitable lime including agricultural lime, hydrated lime, calcined magnesia anddolomite. These vary in their neutralising requirements and the choice depends on cost and availability.Excavated soil will be spread out in a maximum 0.3 m deep layer and covered with the required amount of lime.The required lime dose rate (i.e. kilogram of lime/tonne of material) will be determined from the results of soiltesting in accordance with the Acid Sulfate Soil Manual (ASSMAC, 1998). Lime treatment will be then undertakenby tyning lime and soil aeration with a rotary hoe or similar to obtain thorough mixing and aeration. Treatment ofsoils delivered to the treatment area will be undertaken within one day of delivery, where practicable.10
Acid Sulfate Soil Management PlanFinal validation sampling of treated soils will be conducted at the completion of treatment to determine if theneutralisation process has been successful. Validation sampling will be conducted in accordance with the AcidSulfate Soil Manual (ASSMAC, 1998). The soil will be considered neutralised if the results are below the ActionCriteria outlined in Table 3. Additional lime treatment will be conducted if validation sampling determines the soilis not below the Action Criteria outlined in Table 3.Once treatment is satisfactorily complete, the material will be capped (within the encapsulated cell) with anappropriate cover layer in accordance with Benchmarks 1 and 2 in Environmental Guidelines: Solid WasteLandfills (Environment Protection Authority [EPA], 1996), beneficially reused on the Project site or removed fromthe site for treatment at a licensed facility.3.4.4 Water Management during Excavations and TreatmentWater that accumulates in excavations during Project construction will be tested to determine its quality.Depending on the quality of this water it will be pumped to dedicated detention ponds (e.g. treatment settlementpond) or (if the water quality is suitable) pumped to the site drainage network for storage on-site and re-use.In accordance with Condition 7.3(b), Schedule 2 of Project Approval (06_0009), a Construction Surface WaterManagement Plan (CSWMP) has been developed for the Project. The CSWMP includes a description of the sitedrainage network design. The CSWMP also forms part of the Construction Environmental Management Plan withthis CET ASSMP.Water that is considered to be of unsuitable quality for re-use will be temporarily stored within dedicated detentionponds (e.g. treatment settlement pond) with low permeability liners (e.g. compacted clay or geo-membrane)before being treated for re-use and/or removed from the site and disposed of by a licensed contractor.Water that accumulates in the treatment settlement pond will be treated for re-use and/or removed from the siteand disposed of by a licensed contractor. Fines (from the treatment area) that collect in the settlement pond willbe periodically tested/analysed and if necessary treated as described in Sections 3.4.1, 3.4.2 and 3.4.3.3.5 MONITORING3.5.1 Acid Sulfate SoilsAs described in Section 3.4, a representative surface and sub-surface soil sampling and analysis program will beundertaken for the Project elements requiring excavations into the natural soil profile (Section 3.2) in order tocharacterise material to be excavated. The presence or otherwise of ASS will be identified during this surfaceand sub-surface soil sampling and analysis program.3.5.2 Surface WaterA CSWMP has been developed for the Project in accordance with Condition 7.3(b), Schedule 2 of ProjectApproval (06_0009). The CSWMP includes a surface water monitoring program for the Project. The CSWMPalso forms part of the Construction Environmental Management Plan with this CET ASSMP.11
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