Derivation of Science-Based Environmental Benchmarks for Myra Creek: Background and Approach H. Bailey - PhD, RPBio C. Pettem – MSc, RPBio J. Baker - MSc, PChem Nautilus Environmental (on behalf of Nyrstar Myra Falls)
Acknowledgements This process has involved a lot of input, comments and data from different parties, and we would especially like to thank staff of the Ministry of Environment and Myra Falls Operations for their contributions throughout the program.
Presentation Overview Objective (SBEBS: review the basics) Study Site Conceptual model Contaminants of concern Biological receptors Approach Site details, contaminant data and response metrics Convert contaminant data into benchmarks (max, average) Preliminary findings and validation
Objective Develop Science-Based Environmental Benchmarks for contaminants of concern in Myra Creek. Key points: Measurable Instream concentrations Reflects site-specific conditions Protective of aquatic life Basis for operational and closure targets
Water Quality Metrics Measurable Impairments SBEBs/SSWQOs Screening Level Risk Assessments WQG SBEB Toxic Concentration [Contaminant Concentrations]
Overall Study Area
Key Habitat Features in Myra Creek
Biological Indicators Cutthroat trout Only fish species present Limited critical habitat (off-channel refugia, spawning) Benthic macroinvertebrate community Low productivity, high diversity (EPT taxa)
Contaminants of Concern Identified by exceedances of BCWQGs in Myra Creek Sampling conducted under low and high-flow conditions (5 samples collected over a 30-day period) Primary COCs included copper, zinc and cadmium Small (≤10%) and occasional exceedances were observed for aluminum and silver. Under high-flow conditions, concentrations of some COCs exceeded inputs from mine operations (e.g., Cu and Zn).
Conceptual Model
Contaminants of Concern: Copper 5 in 30 0.184 mg/L Total Copper (mg/L) 0.07 Short Term BCWQG 0.06 Long Term BCWQG 0.05 Maximum measured 0.04 0.03 0.02 0.01 0.00 M1 M1 M2 M2 Low Flow High Flow
Contaminants of Concern: Zinc 5 in 30 2.67 mg/L Total Zinc (mg/L) 1.00 Short Term BCWQG 0.90 0.80 Long Term BCWQG 0.70 Maximum measured 0.60 0.50 0.40 0.30 0.20 0.10 0.00 M1 M1 M2 M2 High Flow Low Flow
Contaminants of Concern: Cadmium 5 in 30 Total Cadmium (mg/L) 0.0008 Short Term BCWQG 0.0007 Long Term BCWQG 0.0006 Maximum measured 0.0005 0.0004 0.0003 0.0002 0.0001 0.0000 M1 M2 M1 M2 Low Flow High Flow
Basic Approach Extensive analytical data from site and discharge as part of regulatory requirements Extensive biological and toxicological data from site and discharge samples as part of long-term monitoring programs “No Evidence of Adverse Effects in Receiving Environment” High confidence that ambient metals concentrations are not causing adverse effects Need to present analytical data in format useful for benchmarks (i.e., average and maximum concentrations).
Available Data Analytical Historical monitoring program (effluent and receiving environment) 5-in-30 sampling program (low and high flow conditions) Biological monitoring data--Five EEM cycles under MMER back to 2003 Benthic macroinvertebrate community surveys In situ chronic exposures of cutthroat trout early life stages Fish surveys Toxicity tests on effluent Acute and sublethal testing on multiple species
Upstream Reference Reach Locations of Benthic Invertebrate, Hatchbox, and Water Quality Sampling Locations in Reference Locations Myra Falls Sixth Environmental Effects Monitoring Program Scale As Shown Date: Oct. 2018
Downstream Exposure Reach Locations of Benthic Invertebrate, Hatchbox, and Water Locations of Benthic Invertebrate, Hatchbox, and Water Quality Sampling Locations in Reference Locations Quality Sampling Locations in Exposure Locations Myra Falls Sixth Environmental Effects Monitoring Program Myra Falls Sixth Environmental Effects Monitoring Program Scale As Shown Date: Oct. 2018 Scale As Shown Date: Oct. 2018
In situ cutthroat trout ELS Exposures (embryo – swim-up)
And for your reading pleasure… Chalmers, B., J. Elphick, G. Gilron and H. Bailey. 2014. Evaluation of an in situ early life stage test with cutthroat trout, Oncorhynchus clarki , for environmental monitoring - a case study using mine effluent. Water Quality Research Journal of Canada. Methodology has also been used at other sites in Canada and the US. Impacts Site Recovery Stormwater monitoring (SeaTac Int’l Airport)
Application of Supporting Data Key underlying data component: EEM monitoring data over 5 cycles indicates no adverse effects on aquatic life 5-in-30 sampling data Used to identify exceedances of WQGs and seasonal differences in concentrations Historical monthly sampling data (2007 – 2012) Use to identify stable distribution patterns (much larger sample size, multiple years of data) Toxicity data Used in supporting role to validate findings
General Procedures Basic Assumption: distribution of concentrations in historical dataset represents a non-toxic condition across multiple seasons and years; just need to model Model Development needs to be transparent and defensible Already have a family of models based on hardness; e.g., BC Copper Short Term = 0.094*(hardness)+2 Re-fit model such that only 5% of datapoints exceed estimated values to establish upper boundary or maximum exposure level (e.g., 95 th percentile) Derive best-fit model using all the data points to obtain the average exposure level Compare with other recognized criteria, toxicity results, etc., for validation Revise if needed
Benchmark Derivation Focus on data from M2 Downstream of all inputs; reflects mine influences, as well as other inputs Well-mixed Essentially the same concentrations as TP- 4 Focus on the dissolved fraction; largely recognized as the bioavailable fraction Copper used to demonstrate concept
Baseline M2 (Total Cu) Compared to BC Water Quality Guidelines Total Copper (mg/L) 0.02 0.015 BC Short Term 0.01 BC Long Term 0.005 0 0 25 50 75 100 125 150 Hardness (mg/L) BC Short Term WQG ( µg/L) = (0.094(hardness)+2) BC Long Term WQG ( µg/L) = 0.04(hardness)
Step 1 M2 (Dissolved Cu) Compared to BC Water Quality Guidelines Dissolved Copper (mg/L) 0.02 0.015 BC Short Term 0.01 BC Long Term 0.005 0 0 25 50 75 100 125 150 Hardness (mg/L) BC Short Term WQG ( µg/L) = (0.094(hardness)+2) BC Long Term WQG ( µg/L) = 0.04(hardness)
Step 2 M2 Derive SBEB Max Dissolved Copper (mg/L) 0.02 0.015 0.01 SBEB Max p 0.005 0 0 25 50 75 100 125 150 Hardness (mg/L) pSBEB Max ( µg/L) = 0.122(hardness)+2
Step 3 M2 SBEB Max and Average Dissolved Copper (mg/L) 0.02 0.015 SBEB Max p 0.01 SBEB Average p 0.005 0 0 25 50 75 100 125 150 Hardness (mg/L) pSBEB Max ( µg/L) = 0.122(hardness)+2 pSBEB Average ( µg/L) = 0.07(hardness)
M2 (Historical Data) Compared to SBEBs and 5 in 30 Data Dissolved Copper (mg/L) 0.08 0.07 0.06 0.05 M1 5 in 30 M2 5 in 30 0.04 SBEB Max p 0.03 SBEB Average p 0.02 0.01 0 0 25 50 75 100 125 150 Hardness (mg/L) pSBEB Max ( µg/L) = 0.122(hardness)+2 pSBEB Average ( µg/L) = 0.07(hardness)
Step 4 M2 (Historical Data) Compared to USEPA Water Quality Guidelines Dissolved Copper (mg/L) 0.02 0.015 USEPA CMC 0.01 USEPA CCC 0.005 0 0 25 50 75 100 125 150 Hardness (mg/L) CMC ( µg/L) = exp (0.9422*(ln(hardness)) - 1.7) CCC ( µg/L) = exp (0.85452*(ln(hardness)) - 1.702)
Step 5 M2 (Historical Data) SBEBs compared to USEPA guidelines Dissolved Copper (mg/L) USEPA vs SBEB Guidelines 0.02 0.015 USEPA CMC USEPA CCC 0.01 SBEB Max p SBEB Average p 0.005 0 0 25 50 75 100 125 150 Hardness (mg/L) CMC ( µg/L) = exp (0.9422*(ln(hardness)) - 1.7) CCC ( µg/L) = exp (0.85452*(ln(hardness)) - 1.702) pSBEB Max ( µg/L) = 0.122(hardness)+2 pSBEB Average ( µg/L) = 0.07(hardness)
Comparison of M2 and Effluent Copper (SBEBs) 5 Year Historical Effluent and M2 Dissolved Copper (mg/L) 0.04 0.035 0.03 0.025 5 Year Effluent 0.02 SBEB Max p 0.015 SBEB Average p 0.01 0.005 0 0 50 100 150 200 250 300 350 400 450 500 Hardness (mg/L) pSBEB Max ( µg/L) = 0.122(hardness)+2 pSBEB Average ( µg/L) = 0.07(hardness)
Copper Concentrations During in situ Test EEM Cycle 5 and 6 Dissolved Copper (mg/L) 0.02 0.015 Cycle 6 0.01 Cycle 5 SBEB Max p SBEB Average p 0.005 0 0 25 50 75 100 125 150 Hardness (mg/L) pSBEB Max ( µg/L) = 0.122(hardness)+2 pSBEB Average ( µg/L) = 0.07(hardness)
Conclusions and Next Steps… Procedures appear to be reasonable and protective; Apply procedures to cadmium and zinc Use similar process; some tweaks may be necessary.
Spare Slides Follow
Minor Exceedances; No SBEB Proposed (aluminum) 5 in 30 Dissolved Aluminum (mg/L) 0.16 Short Term BCWQG 0.14 Long Term BCWQG 0.12 Maximum measured 0.10 0.08 0.06 0.04 0.02 0.00 M1 TP4 M2 TP4 M2 M1 High Flow Low Flow
Reiterate Objective Present analytical data (i.e., metals concentrations) in format useful for benchmarks (i.e., average and maximum concentrations)
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