Overview of the Human Health and Ecological Risk...
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Overview of the Human Health and Ecological Risk Assessment Mount Polley Breach Response BEST 2017Conference May 10-12, 2017 Whistler, BC Trish Miller, M.Sc., CSAP, Risk Assessment Reidar Zapf-Gilje, Ph.D., P.Eng., CSAP, Site Investigation & Risk Assessment Suzanne Simard, Ph.D., UBC Forest Ecologist Mount Polley Mining Corporation
Transcript of Overview of the Human Health and Ecological Risk...
Overview of the Human Health and Ecological Risk Assessment
Mount Polley Breach ResponseBEST 2017Conference
May 10-12, 2017Whistler, BC
Trish Miller, M.Sc., CSAP, Risk AssessmentReidar Zapf-Gilje, Ph.D., P.Eng., CSAP, Site Investigation & Risk AssessmentSuzanne Simard, Ph.D., UBC Forest Ecologist
Mount PolleyMining Corporation
May 14, 2017 3
Mount Polley Remediation Strategy
Mount PolleyMining Corporation
May 14, 2017 4
Summary of Post Event Key Findings
Physical Impacts - Available evidence to date indicates physical effects to PolleyLake, Hazeltine Creek and valley, Edney Creek, Quesnel Lake. Loss or reduction of lower trophic level habitats in affected terrestrial and aquatic environments. Restoration underway, with some re-colonizing taking hold
Chemical Impacts – Concentrations of copper and vanadium in soil/tailings were greater than BC CSR standard. SRK found tailings are not acid-generating and have low leaching potential
Biological Impacts – Loss of soil and sediment communities in affected areas; limited evidence of metal toxicity, plants growing through tailings in some areas
May 14, 2017 5
Summary of Detailed Site Investigation
Remediation AreaContaminants of Concern
Soil Groundwater Surface Water SedimentArea 2 – Polley Plug/Polley Flats
Copper, Vanadium, Sulfur, Molybdenum
Sulphate, Iron, Manganese, No Substances n/a
Area 3 – Polley Lake n/a n/a No Substances Copper, ArsenicArea 4, 5, and 6 – Hazeltine Creek
Vanadium, Sulfur, Molybdenum
Iron, Manganese, Arsenic Copper, total & dissolvedCopper (sedimentation
pond)Area 7 – Edney Creek Mouth
n/a n/a Copper, total & dissolved No Substances
Area 8 – Quesnel Lake n/a n/a No Substances Copper, ArsenicArea 9 – Quesnel River n/a n/a No Substances No Substances
Table: Summary of DSI Findings - Contaminants of Potential Concern
• Remediation in Hazeltine Creek channel on-going.
May 14, 2017 6
Problem Formulation
Mount PolleyMining Corporation
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What are the contaminants for human health?
Mount PolleyMining Corporation
Soil: no contaminants for human health
Groundwater : sulphate, arsenic, iron, manganese > DW: DW standard not used for drinking water
Surface Water: no DW exceedences
Vapours: no volatile contaminants
Air: no COPCs/particulate concerns based on dust monitoring in operational area of mine
May 14, 2017 8
Copper Concentrations in Plants
May 14, 2017 9
Notes:= operable exposure pathway; = inoperable exposure pathway.
1 There is no access to groundwater on the site
Human Receptors - Potential Exposure Pathways
Receptor of Potential Concern
Soil Groundwater1 Sediment Surface Water Dietary Items
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Fish
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Subsistence and Traditional Land User
Hiker/Camper
ATV/Snowmobile User
Boater/Kayaker
Sport Fisher
Hunter/Trapper
Quesnel Lake Resident
Logger
Mine/Rehabilitation Worker
May 14, 2017 10
Preliminary HHRA Results
HHRA Results = Total ExposureSafe Exposure
Calculations and review are in progress
Based on preliminary findings, risks to human health are acceptable
May 14, 2017 11
What are the contaminants for terrestrial wildlife?
Determined based on comparison of Site data to BC CSR Standards:
Soil/tailings: copper, vanadium Groundwater: no DW exceedencesSurface water: no DW exceedencesSediment: copper and arsenic
Physical stressors, low nutrients, organic carbon
Mount PolleyMining Corporation
May 14, 2017 12
Potential Exposure Pathways – Terrestrial Life
May 14, 2017 13
TERA - Weight of Evidence Approach
Physical changes are confounding factor to evaluating contaminant-related effects; also a stressor
Rely on multiple lines of evidence to determine risk and need for remediation
Field observations are important
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TERA – Weight of Evidence
Twenty lines of evidence (LOE) used in TERAchemistryfield & in situ measurementstoxicity testingfood chain modelling
Assessment/measurement endpoints
Decision criteria
Strength of association
May 14, 2017 15
Tree mortality, loss of lower trophic level community appears to be related to oxygen limiting conditions rather than metal concentrations
Terrestrial Ecosystem – Field Observations
May 14, 2017 16
What are the findings for terrestrial wildlife?
Mount PolleyMining Corporation
Tailings deposition and scoured zones presented physical growth-limiting conditions to lower trophic level receptors
• soil microbial community• plants• invertebrates
Statistical differences in metal concentrations between impacted area and background concentrations
• soil invertebrates• plants
Food chain modelling in progress
Findings continue to indicate that the physical change is the dominant stressor
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Potential Exposure Pathways for Aquatic Life
Mount PolleyMining Corporation
May 14, 2017 18
What are the findings for aquatic life?
TRIAD Results:Chemistry: No COPCs in surface water in Quesnel and Polley Lakes; copper in Hazeltine Channel. Periodic episodes of turbidity related to remediation work
Toxicity: Surface water toxicity tests have repeatedly shown no chemical-related impacts; limited evidence of potential impacts due to turbidity only immediately following breach;
In situ: Preliminary fish data: may be localized increase to whole body metal concentrations to small fish; muscle concentrations are similar to reference sites for small and large fish; similar productivity; on-going monitoring
Mount PolleyMining Corporation
May 14, 2017 19
What are the findings for aquatic life?
TRIAD results for sediment:
Chemistry: Polley & Quesnel Lakes; copper and arsenic
Toxicity: reduced amphipod growth; sediment bioassays confounded by uniform grain size and low organic carbon content
In situ: benthic community lost in deep part of the lake following deposition of tailings; recovery of benthic community expected based on sediment transplant studies; no impact on fish productivity
Mount PolleyMining Corporation
May 14, 2017 20
Preliminary Conclusions
Mount PolleyMining Corporation
Human health risk assessment found no contaminants for soil, drinking water, air; potential concerns related to plants and game were addressed using a food chain model calibrated to the Site
Ecological risk assessment has indicated a loss of habitat and soil and sediment-dependent receptors in the immediate area of impact but chemical-related impacts appear to be low.
Detailed geochemistry test results were a good predictor of bioavailability and toxicity of tailings to human and ecological receptors.
May 14, 2017 21
Questions?
May 14, 2017 22
Insert figure showing remediated areas along HCC
May 14, 2017 23
Hazeltine Corridor Current Soil Conditions
Copper concentrations in soil (mg/kg) in remediation areas compared to untreated areas
Area Treatment n Min Max Mean 90th
Percentile95 UCLM
Halo Intermixed Soils Zone 30 62 880 531 821 538
Floodplain Transplanted Soils Zone 30 67 532 158 302 197
Floodplain Scarified Zone 30 37 715 191 378 256
Floodplain / Halo Untreated 182 42 1560 702 1000 737
