Remediation of a Coal Waste Pile in Union Bay, BC · Waste coal present to > 30 m offshore Iron...
Transcript of Remediation of a Coal Waste Pile in Union Bay, BC · Waste coal present to > 30 m offshore Iron...
Remediation of a Coal Waste Pile in Union Bay, BC
Remediation of a Coal Waste Pile in Union Bay, BC
Remediation of a Coal Waste Pile in Union Bay, BC
Tara Siemens, MET and Ian Mitchell, MSc, PGeoSEACOR Environmental Inc.
OutlineOutlineSite Description and HistoryEnvironmental InvestigationsProblem Formulation/Screening RARemedial Plan
Site Description and HistoryEnvironmental InvestigationsProblem Formulation/Screening RARemedial Plan
Site DescriptionSite Description13 ha waste coal pile in Union Bay, BC13 ha waste coal pile in Union Bay, BC
Site DescriptionSite Description13 ha waste coal pile in Union Bay, BCBounded to north and east by Pacific Ocean
13 ha waste coal pile in Union Bay, BCBounded to north and east by Pacific Ocean
Site DescriptionSite Description13 ha waste coal pile in Union Bay, BCBounded to north and east by Pacific OceanBounded to west by Hart Creek
13 ha waste coal pile in Union Bay, BCBounded to north and east by Pacific OceanBounded to west by Hart Creek
Site DescriptionSite Description13 ha waste coal pile in Union Bay, BCBounded to north and east by Pacific OceanBounded to west by Hart CreekFuture land use: residential/parkland
13 ha waste coal pile in Union Bay, BCBounded to north and east by Pacific OceanBounded to west by Hart CreekFuture land use: residential/parkland
Site HistorySite HistoryCoal Processing Facility1888 to ~ 1960Coal Processing Facility1888 to ~ 1960
Historical photographs from BC Archive at www.bcarchives.gov.bc.ca.
Site HistorySite HistoryCoal Processing Facility1888 to ~ 1960Coal Processing Facility1888 to ~ 1960
Historical photographs from BC Archive at www.bcarchives.gov.bc.ca.
Site HistorySite HistoryCoal Processing Facility1888 to ~ 1960Coal Processing Facility1888 to ~ 1960
Historical photographs from BC Archive at www.bcarchives.gov.bc.ca.
Site HistorySite HistoryCoal Processing Facility1888 to ~ 1960Coal Processing Facility1888 to ~ 1960
Historical photographs from BC Archive at www.bcarchives.gov.bc.ca.
Environmental InvestigationsEnvironmental Investigations
Waste Coal Pile and adjacent properties, Baynes Sound and Hart Creek
Waste Coal Pile and adjacent properties, Baynes Sound and Hart CreekSamples of waste coal, native soil, groundwater, sediment and surface water analysed for PCOCs
Samples of waste coal, native soil, groundwater, sediment and surface water analysed for PCOCsPCOCs include metals, PAHs, sulphatePCOCs include metals, PAHs, sulphateABA, kinetic testing and other geochemical parametersABA, kinetic testing and other geochemical parameters
Waste Coal Pile - ResultsWaste Coal Pile - ResultsWaste Coal: arsenic, copper, naphthalene and phenanthrene > standardsNative soils < standardsGroundwater: cadmium,cobalt, copper, nickel, zinc and sulphate > standards for aquatic life; PAHs < standards
Waste Coal: arsenic, copper, naphthalene and phenanthrene > standardsNative soils < standardsGroundwater: cadmium,cobalt, copper, nickel, zinc and sulphate > standards for aquatic life; PAHs < standards
Hart Creek - ResultsHart Creek - ResultsSurface Water < criteriaSediment: PAHs and metals > criteria in 1 sample Surface Water < criteriaSediment: PAHs and metals > criteria in 1 sample
Baynes Sound - ResultsBaynes Sound - ResultsWaste coal present to > 30 m offshoreIron staining present in sediments north and east of coal pile in areas of groundwater discharge
Waste coal present to > 30 m offshoreIron staining present in sediments north and east of coal pile in areas of groundwater dischargeSediment: PAHs and metals > criteria
9 PAHsArsenic, copper and mercury
Sediment: PAHs and metals > criteria9 PAHsArsenic, copper and mercury
Seep water: Metals > criteriaAluminum, cadmium, cobalt, iron, manganese, nickel and zinc~ 10x’s dilution of groundwater occurring during discharge to environment
Seep water: Metals > criteriaAluminum, cadmium, cobalt, iron, manganese, nickel and zinc~ 10x’s dilution of groundwater occurring during discharge to environment
GeochemistryGeochemistry
Geochemical characterization conducted by SRK Consulting (Canada) Inc.Static and kinetic testing conducted
Geochemical characterization conducted by SRK Consulting (Canada) Inc.Static and kinetic testing conducted
Testing indicated that all material is potentially acid generating or is already acidic
Testing indicated that all material is potentially acid generating or is already acidic
Under existing conditions, acidification expected to continue for decades to a century
Under existing conditions, acidification expected to continue for decades to a century
Geochemical ProfileSulphide sulphur present throughoutAccumulation of sulphate within top 2 mIncreasing pH and NP with depth
Geochemical ProfileSulphide sulphur present throughoutAccumulation of sulphate within top 2 mIncreasing pH and NP with depth
Detailed Hydrogeology Assessment
Detailed Hydrogeology Assessment
Review of climate dataInfiltration tests at pile surfaceHydraulic conductivity tests at base of pileAnalysis of tidal effectsPhysicochemical groundwater monitoringAssessment of groundwater flowEvaluation of pile water balance
Review of climate dataInfiltration tests at pile surfaceHydraulic conductivity tests at base of pileAnalysis of tidal effectsPhysicochemical groundwater monitoringAssessment of groundwater flowEvaluation of pile water balance
Infiltration Test Results Infiltration Test Results
Infiltration rate at 20cm depth is 5x greater than infiltration rate at typical surface locationsInfiltration rate at typical surface locations is 10x greater than highly compacted surface areas
Infiltration rate at 20cm depth is 5x greater than infiltration rate at typical surface locationsInfiltration rate at typical surface locations is 10x greater than highly compacted surface areas
Tidal Analysis Tidal Analysis
Tidally induced groundwater fluctuations 1.5m adjacent to foreshore; absent 400 metres inlandIntrusion of saline groundwater observed to 75m inlandUpgradient third of pile not exposed to tidal flushing
Tidally induced groundwater fluctuations 1.5m adjacent to foreshore; absent 400 metres inlandIntrusion of saline groundwater observed to 75m inlandUpgradient third of pile not exposed to tidal flushing
Summary of Groundwater Flow Summary of Groundwater Flow Estimated groundwater velocity in coal waste is 100-150 m/yrEstimated groundwater velocity in underlying native soil is 15-25 m/yrNet groundwater flow direction is towards the ocean
Estimated groundwater velocity in coal waste is 100-150 m/yrEstimated groundwater velocity in underlying native soil is 15-25 m/yrNet groundwater flow direction is towards the ocean
Water Balance Water Balance
Important Conclusions Important Conclusions
Upgradient side of pile not recharged by Hart CreekContrast in conductivity promotes seepage along interface at base of pileBaseflow flushing through pile is relatively small component of overall discharge
Upgradient side of pile not recharged by Hart CreekContrast in conductivity promotes seepage along interface at base of pileBaseflow flushing through pile is relatively small component of overall discharge
Upgradient third of pile unsaturated at the baseUpgradient third of pile unsaturated at the base
Problem Formulation/SLRAProblem Formulation/SLRABased on pre-remediation conditions; comprehensive RA to be conducted post remediationChemicals of Potential Concern for RA = parameters in different media > applicable standards/criteria
Based on pre-remediation conditions; comprehensive RA to be conducted post remediationChemicals of Potential Concern for RA = parameters in different media > applicable standards/criteria
Human Health SLRAHuman Health SLRANon-cancer and cancer risks to Site users < 1E+00 and 1E-05Risks to seafood consumers <1E+00 and 1E-05
Non-cancer and cancer risks to Site users < 1E+00 and 1E-05Risks to seafood consumers <1E+00 and 1E-05
Marine species identified as primary receptors of concernMarine species identified as primary receptors of concern
Problem Formulation/SLRAProblem Formulation/SLRAEcological RAEcological RA
Primary assessment endpoints for Eco RA:
Bioassays for benthic and pelagic speciesSpecies composition and habitat quality
Preliminary evaluation of endpoints conducted
Primary assessment endpoints for Eco RA:
Bioassays for benthic and pelagic speciesSpecies composition and habitat quality
Preliminary evaluation of endpoints conducted
Sediment bioassays:for amphipod (E. estuarius) and polycheate (N. arenaceodentata)one sample of six toxic to polychaete
Sediment bioassays:for amphipod (E. estuarius) and polycheate (N. arenaceodentata)one sample of six toxic to polychaete
Problem Formulation/SLRAProblem Formulation/SLRAEcological RA (cont.)Ecological RA (cont.)
Groundwater and seep water bioassays:for topsmelt (A. affinis), sand dollar gametes (D. excentricus) and oyster spat (C. gigas)Preliminary results indicate lethality at 6%
Groundwater and seep water bioassays:for topsmelt (A. affinis), sand dollar gametes (D. excentricus) and oyster spat (C. gigas)Preliminary results indicate lethality at 6%
Abundant flora and fauna present in intertidaland subtidal, including extensive eel grass bedAbundant flora and fauna present in intertidaland subtidal, including extensive eel grass bed
Risk-Based Groundwater Remedial TargetsRisk-Based Groundwater Remedial Targets
Site-specific groundwater remedial targets currently being derived
Based on results of toxicity testing and literature reviewFinal remedial design will be based on groundwater remedial targets
Site-specific groundwater remedial targets currently being derived
Based on results of toxicity testing and literature reviewFinal remedial design will be based on groundwater remedial targets
Remediation Plan Remediation Plan Waste coal subdivided into 4 different zones:Waste coal subdivided into 4 different zones:
Main pile (focus of presentation)Main pile (focus of presentation)
Distinct characteristics indicate that different remedial strategies required for each zone
Distinct characteristics indicate that different remedial strategies required for each zone
Hart Creek depositHart Creek deposit
Tidal Zone depositTidal Zone deposit
Submarine depositSubmarine deposit
Remediation of Main PilePrimary Considerations Remediation of Main PilePrimary Considerations
Technical feasibilityCost and associated risks Potential for economic benefitsPreference given to alternativesthat provide a more permanent solution
Technical feasibilityCost and associated risks Potential for economic benefitsPreference given to alternativesthat provide a more permanent solution
Remediation of Main PileImportant Factors
Remediation of Main PileImportant Factors
Pile forms a distinctly convex domeCoarse waste material results in a net downward flux of waterSteep side slopes may destabilize over time as pile acidifies and cementation degrades Data indicates that direct revegetation is unlikely sustainable
Pile forms a distinctly convex domeCoarse waste material results in a net downward flux of waterSteep side slopes may destabilize over time as pile acidifies and cementation degrades Data indicates that direct revegetation is unlikely sustainable
Contaminant Release Mechanisms
Contaminant Release Mechanisms
Wind Dispersion of the waste coal solidsLeaching of metals by infiltrating water and runoffLeaching of metals by tidal effectsShore erosion by wave action in tidal and subtidal zoneErosion by stream flow in Hart Creek
Wind Dispersion of the waste coal solidsLeaching of metals by infiltrating water and runoffLeaching of metals by tidal effectsShore erosion by wave action in tidal and subtidal zoneErosion by stream flow in Hart Creek
Potential Control Measuresto Reduce Metal Loadings Potential Control Measuresto Reduce Metal Loadings
Alkaline amendment to offset excess acid potentialMeasures to control oxygen ingress to the pileReduction or elimination of infiltration of water
Alkaline amendment to offset excess acid potentialMeasures to control oxygen ingress to the pileReduction or elimination of infiltration of water
Primary Remedial Objectives Primary Remedial Objectives
Minimize potential release of contaminants by wind blown dustMinimize release of soluble oxidation products to groundwaterRestore coal pile to land use suitable for residential/urban park
Minimize potential release of contaminants by wind blown dustMinimize release of soluble oxidation products to groundwaterRestore coal pile to land use suitable for residential/urban park
Based on the above, the selected remedial alternative is a physical cover/cap
Based on the above, the selected remedial alternative is a physical cover/cap
Cover Design Considerations Cover Design Considerations
Climatic water balance for the pile is net positiveMain risk to low permeability cover is dessication due to wet/dry cyclesRegrading of steep slopes requiredSpecial design considerations for contact areas with roadways, foundations
Climatic water balance for the pile is net positiveMain risk to low permeability cover is dessication due to wet/dry cyclesRegrading of steep slopes requiredSpecial design considerations for contact areas with roadways, foundations
Cover Design Considerations Cover Design Considerations
Management of runoff to control erosionShoreline protection measuresManagement of runoff to control erosionShoreline protection measures
Preferred Cover Design Alternatives
Preferred Cover Design Alternatives
Natural soil low permeability barrier coverSynthetic barrier cover using HDPE/Bituminous linerSynthetic barrier cover using GCLStore and release cover
Natural soil low permeability barrier coverSynthetic barrier cover using HDPE/Bituminous linerSynthetic barrier cover using GCLStore and release cover
Cover Design Uncertainties Cover Design Uncertainties
Availability of suitable low permeability soilAvailability of vegetation substrateFinal adopted remediation design lifeFinal adopted land useOverall cost effectivenessRisk based groundwater remedial target
Availability of suitable low permeability soilAvailability of vegetation substrateFinal adopted remediation design lifeFinal adopted land useOverall cost effectivenessRisk based groundwater remedial target
Path Forward Path Forward
Risk based targets for groundwater currently being derived Slope regrading and capping of pile slated for summer 2006
Risk based targets for groundwater currently being derived Slope regrading and capping of pile slated for summer 2006
Upper reaches of Hart Creek rechannelled in Sept 2005Upper reaches of Hart Creek rechannelled in Sept 2005