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Britannia Mine: Environmental Impact Study of Treated Effluent Discharge Lee Nikl.

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Presentation on theme: "Britannia Mine: Environmental Impact Study of Treated Effluent Discharge Lee Nikl."— Presentation transcript:

1 Britannia Mine: Environmental Impact Study of Treated Effluent Discharge Lee Nikl

2 Background/Context: Recent changes to effluent permitting procedures have increased the requirements for dischargers to study potential environmental effects of their discharge Dischargers are required to complete an Environmental Impact Study (also called a Technical Assessment) and demonstrate to WLAP that the environment will not be impaired.

3 What is it about effluents that causes harm to the environment? Toxic substances contained in the effluent can act on aquatic organisms to result in adverse effects. Studying these toxic substances allows us to make responsible decisions regarding effluent discharges. Toxic substances contained in the effluent can act on aquatic organisms to result in adverse effects. Studying these toxic substances allows us to make responsible decisions regarding effluent discharges.

4 What do we need to know to predict environmental effects of an effluent? Source : Identify contaminants of potential concern (COPC). Pathway : Identify pathway between the source and the receptors in the environment. Receptors : Identify the organisms that will be potentially exposed to the effluent constituents Exposure Assessment : Identify the exposure of organisms to the COPC. Effects Assessment : Identify the likelihood that adverse effects will take place. Source : Identify contaminants of potential concern (COPC). Pathway : Identify pathway between the source and the receptors in the environment. Receptors : Identify the organisms that will be potentially exposed to the effluent constituents Exposure Assessment : Identify the exposure of organisms to the COPC. Effects Assessment : Identify the likelihood that adverse effects will take place.

5 Britannia Mine: Effluent EIS Approach The effluent treatment system is not yet constructed and there is no treated effluent. The purpose of the EIS is to make informed effluent permitting decisions before the discharge takes place. This precautionary approach prevents environmentally disruptive discharges at the outset. The effluent treatment system is not yet constructed and there is no treated effluent. The purpose of the EIS is to make informed effluent permitting decisions before the discharge takes place. This precautionary approach prevents environmentally disruptive discharges at the outset.

6 Britannia Mine: Effluent EIS Approach Source: The source of effluent is the High Density Sludge treatment system –COPCs identified are copper, zinc, cadmium Pathway: Conveyance through outfall pipe to Howe Sound. EIS assessed discharge via existing (26m) outfall and new (50m) outfall. Receptors: Fish, zooplankton, etc. Productivity greatest in the photic zone which is ~10-15m in Howe Sound (20m used) Source: The source of effluent is the High Density Sludge treatment system –COPCs identified are copper, zinc, cadmium Pathway: Conveyance through outfall pipe to Howe Sound. EIS assessed discharge via existing (26m) outfall and new (50m) outfall. Receptors: Fish, zooplankton, etc. Productivity greatest in the photic zone which is ~10-15m in Howe Sound (20m used)

7 Britannia Mine: Effluent EIS Approach Exposure Assessment: –Predicted effluent chemistry was based on lab analysis of actual tests on the effluent. –Predicted concentrations in the environment were derived from US EPA computer simulation model of effluent dispersion. –Various scenarios were examined to encompass fluctuations due to seasonality and climate. Exposure Assessment: –Predicted effluent chemistry was based on lab analysis of actual tests on the effluent. –Predicted concentrations in the environment were derived from US EPA computer simulation model of effluent dispersion. –Various scenarios were examined to encompass fluctuations due to seasonality and climate.

8 Britannia Mine: Effluent EIS Approach Exposure Assessment: –The minimum requirements of WLAP are to identify the concentration of contaminants at the edge of the Initial Dilution Zone (IDZ), a 100m radius cylinder of water surrounding the outfall terminus. –WLAP can require additional requirements to suit specific circumstances. –EIS conducted here also examined exposure within the IDZ, specifically, at the boundary of the photic zone and also at the “end-of-pipe” (federal requirements) Exposure Assessment: –The minimum requirements of WLAP are to identify the concentration of contaminants at the edge of the Initial Dilution Zone (IDZ), a 100m radius cylinder of water surrounding the outfall terminus. –WLAP can require additional requirements to suit specific circumstances. –EIS conducted here also examined exposure within the IDZ, specifically, at the boundary of the photic zone and also at the “end-of-pipe” (federal requirements)

9 Britannia Mine: Effluent EIS Approach Exposure Assessment: –The scenarios modeled (simplified version presented here – full version in report) were as follows: Exposure Assessment: –The scenarios modeled (simplified version presented here – full version in report) were as follows: Case Flow (m 3 /hr) d.Cu (ppm) d.Zn (ppm) TSS (ppm) Average Flow Design Flow Permit Flow High Flow

10 Britannia Mine: Effluent EIS Approach Effects Assessment: –The most simple and conservative means of assessing effects is to compare predicted concentrations to ambient criteria –Comparison of predicted environmental concentrations were compared to criteria in Tier 1 of this assessment. Effects Assessment: –The most simple and conservative means of assessing effects is to compare predicted concentrations to ambient criteria –Comparison of predicted environmental concentrations were compared to criteria in Tier 1 of this assessment.

11 Metal Speciation The toxicity of a metal is related to its bioavailability. Various factors in the environment control bioavailability. Ambient criteria are based on the most bioavailable form and do not provide a realistic assessment of effect. The toxicity of a metal is related to its bioavailability. Various factors in the environment control bioavailability. Ambient criteria are based on the most bioavailable form and do not provide a realistic assessment of effect.

12 Britannia Mine: Effluent EIS Approach Effects Assessment: –In Tier 2 of assessment, the bioavailability of metals was assessed. –Computerized chemical speciation modeling was undertaken using predicted concentrations and background water chemistry. –This approach provides more realistic information from which to predict potential effects. Effects Assessment: –In Tier 2 of assessment, the bioavailability of metals was assessed. –Computerized chemical speciation modeling was undertaken using predicted concentrations and background water chemistry. –This approach provides more realistic information from which to predict potential effects.

13 Effluent EIS: Findings Tier 1 Assessment: (end of pipe) –Treated effluent was submitted for toxicity testing. Tier 1 Assessment: (end of pipe) –Treated effluent was submitted for toxicity testing. TestResult Rainbow trout acute lethality Not acutely lethal Amphipod survivalNot acutely lethal Chinook salmon acute lethality Not acutely lethal Topsmelt 7d survivalNot acutely lethal Topsmelt 7d growthNo significant inhibition Algal 72-h growth inhibitionNo significant inhibition Echinoid fertilizationNo significant inhibition

14 Effluent EIS: Findings Tier 1 Assessment: edge of IDZ (26m outfall)

15 Effluent EIS: Findings Tier 1 Assessment: edge of IDZ (50m outfall)

16 Effluent EIS: Findings Tier 1 Assessment: Dilution with distance from 50m outfall terminus

17 Effluent EIS: Findings Tier 1 Assessment: Photic Zone –HQs are elevated (d.Cu = 8.8; d.Cd = 17; d.Zn = 3.6) at the bottom of the photic zone (20m) using the 26m outfall depth –With a 50m outfall, effluent plume trapping depths range from 16.2 to 26.1m, depending on the flow scenario – interaction with the photic zone is not significant if effluent is discharged at 50m. Tier 1 Assessment: Photic Zone –HQs are elevated (d.Cu = 8.8; d.Cd = 17; d.Zn = 3.6) at the bottom of the photic zone (20m) using the 26m outfall depth –With a 50m outfall, effluent plume trapping depths range from 16.2 to 26.1m, depending on the flow scenario – interaction with the photic zone is not significant if effluent is discharged at 50m.

18 Effluent EIS: Findings Tier 1 Assessment: Summary –Using the 50m deep outfall, WQC were met for dissolved copper at the edge of the IDZ under all cases modeled. Interaction with the photic zone is minimal –Using the 26m deep outfall, WQC for dissolved copper are exceeded for the permit flow and high flow cases. –Total copper is predicted to exceed WQC for all flow scenarios and outfalls modeled. Tier 1 Assessment: Summary –Using the 50m deep outfall, WQC were met for dissolved copper at the edge of the IDZ under all cases modeled. Interaction with the photic zone is minimal –Using the 26m deep outfall, WQC for dissolved copper are exceeded for the permit flow and high flow cases. –Total copper is predicted to exceed WQC for all flow scenarios and outfalls modeled.

19 Effluent EIS: Findings Tier 2 Assessment (bioavailability): MetalSpeciation Modeling Results CopperMajority of copper bound by organic (65-81%) and inorganic (18-35%) ligands. Less than 0.2% present in the highly bioavailable forms (Cu +2, the most bioavailable form comprised less than 0.01%). ZincMajority of zinc exists as non-bioavailable inorganic (81-89%) and organic (5-13%) complexes. Approximately 5% of the zinc exists as Zn 2+. CadmiumMajority of cadmium exists as organic complexes (64-94%) and inorganic complexes (5-13%). Approximately 0.3 to 0.6% of the cadmium exists as Cd 2+.

20 Effluent EIS: Findings Tier 2 Assessment (bioavailability): –If the 50m outfall is used for discharge, exceedences of ambient criteria will be infrequent and, when they occur, small in magnitude –These minor exceedences are not biologically relevant, however, given the small proportion of metal that will be in a bioavailable form Tier 2 Assessment (bioavailability): –If the 50m outfall is used for discharge, exceedences of ambient criteria will be infrequent and, when they occur, small in magnitude –These minor exceedences are not biologically relevant, however, given the small proportion of metal that will be in a bioavailable form

21 Uncertainty Analysis The EIS is a predictive exercise. Assumptions were necessary and direct measurements not possible. An analysis of the uncertainties was undertaken to identify the significance and consequence, if any, to the predictions of effect. The EIS is a predictive exercise. Assumptions were necessary and direct measurements not possible. An analysis of the uncertainties was undertaken to identify the significance and consequence, if any, to the predictions of effect.

22 Uncertainty Analysis Uncertainties were either not significant or, if there was doubt, this was identified as a need for subsequent effluent monitoring. Deferral to monitoring was deemed acceptable only if there is a means to enact further control over the effluent. Uncertainties were either not significant or, if there was doubt, this was identified as a need for subsequent effluent monitoring. Deferral to monitoring was deemed acceptable only if there is a means to enact further control over the effluent.

23 Conclusion Discharge via the existing 26m outfall is not recommended. Discharge via the 50m outfall is not expected to result in adverse environmental effects. Discharge via the existing 26m outfall is not recommended. Discharge via the 50m outfall is not expected to result in adverse environmental effects.


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