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