Derivation of Science-Based Environmental Benchmarks for Myra - - PowerPoint PPT Presentation

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

WQG SBEB Toxic Concentration

[Contaminant Concentrations]

Screening Level Risk Assessments SBEBs/SSWQOs Measurable Impairments

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

Short Term BCWQG Long Term BCWQG Maximum measured 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07

5 in 30 Total Copper (mg/L)

0.184 mg/L

High Flow Low Flow

M2 M1 M2 M1

Short Term BCWQG Long Term BCWQG Maximum measured

Contaminants of Concern: Zinc

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

5 in 30 Total Zinc (mg/L)

2.67 mg/L

High Flow Low Flow

M2 M1 M2 M1

0.0000 0.0001 0.0002 0.0003 0.0004 0.0005 0.0006 0.0007 0.0008

5 in 30 Total Cadmium (mg/L)

Short Term BCWQG Long Term BCWQG Maximum measured

Contaminants of Concern: Cadmium

High Flow Low Flow

M2 M1 M2 M1

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

Scale As Shown Date: Oct. 2018 Locations of Benthic Invertebrate, Hatchbox, and Water Quality Sampling Locations in Reference Locations Myra Falls Sixth Environmental Effects Monitoring Program

Downstream Exposure Reach

Scale As Shown Date: Oct. 2018 Locations of Benthic Invertebrate, Hatchbox, and Water Quality Sampling Locations in Reference Locations Myra Falls Sixth Environmental Effects Monitoring Program Locations of Benthic Invertebrate, Hatchbox, and Water Quality Sampling Locations in Exposure Locations Myra Falls Sixth Environmental Effects Monitoring Program 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., 95th 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

M2 (Total Cu)

Compared to BC Water Quality Guidelines

BC Short Term WQG (µg/L) = (0.094(hardness)+2) BC Long Term WQG (µg/L) = 0.04(hardness)

0.005 0.01 0.015 0.02 25 50 75 100 125 150

Hardness (mg/L)

Total Copper (mg/L)

BC Short Term BC Long Term

Baseline

0.005 0.01 0.015 0.02 25 50 75 100 125 150

Hardness (mg/L)

Dissolved Copper (mg/L)

BC Short Term BC Long Term

M2 (Dissolved Cu)

Compared to BC Water Quality Guidelines Step 1

BC Short Term WQG (µg/L) = (0.094(hardness)+2) BC Long Term WQG (µg/L) = 0.04(hardness)

pSBEB Max (µg/L) = 0.122(hardness)+2

M2

Derive SBEB Max Step 2

0.005 0.01 0.015 0.02 25 50 75 100 125 150

Hardness (mg/L)

Dissolved Copper (mg/L)

SBEB Max

p

pSBEB Max (µg/L) = 0.122(hardness)+2 pSBEB Average (µg/L) = 0.07(hardness)

M2

SBEB Max and Average Step 3

0.005 0.01 0.015 0.02 25 50 75 100 125 150

Hardness (mg/L)

Dissolved Copper (mg/L)

SBEB Max SBEB Average

p p

M2 (Historical Data)

Compared to SBEBs and 5 in 30 Data

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 25 50 75 100 125 150

Hardness (mg/L)

Dissolved Copper (mg/L)

M1 5 in 30 M2 5 in 30 SBEB Max SBEB Average

p p

pSBEB Max (µg/L) = 0.122(hardness)+2 pSBEB Average (µg/L) = 0.07(hardness)

CMC (µg/L) = exp(0.9422*(ln(hardness))-1.7) CCC (µg/L) = exp(0.85452*(ln(hardness))-1.702)

0.005 0.01 0.015 0.02 25 50 75 100 125 150

Hardness (mg/L)

Dissolved Copper (mg/L)

USEPA CMC USEPA CCC

M2 (Historical Data)

Compared to USEPA Water Quality Guidelines Step 4

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)

M2 (Historical Data)

SBEBs compared to USEPA guidelines Step 5

0.005 0.01 0.015 0.02 25 50 75 100 125 150

Hardness (mg/L)

Dissolved Copper (mg/L) USEPA vs SBEB Guidelines

USEPA CMC USEPA CCC SBEB Max SBEB Average

p p

0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 50 100 150 200 250 300 350 400 450 500

Hardness (mg/L)

5 Year Historical Effluent and M2 Dissolved Copper (mg/L)

5 Year Effluent SBEB Max SBEB Average

p p

pSBEB Max (µg/L) = 0.122(hardness)+2 pSBEB Average (µg/L) = 0.07(hardness)

Comparison of M2 and Effluent Copper (SBEBs)

Copper Concentrations During in situ Test EEM Cycle 5 and 6

0.005 0.01 0.015 0.02 25 50 75 100 125 150

Hardness (mg/L)

Dissolved Copper (mg/L)

Cycle 6 Cycle 5 SBEB Max SBEB Average

p p

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)

Short Term BCWQG Long Term BCWQG Maximum measured 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16

5 in 30 Dissolved Aluminum (mg/L)

High Flow Low Flow

M1 TP4 M2 M1 TP4 M2

Reiterate Objective

Present analytical data (i.e., metals concentrations) in format useful for benchmarks (i.e., average and maximum concentrations)

Historical data are conservative; contribution of upstream sources limited under low-flow conditions

0.000 0.005 0.010 0.015 0.020 0.025 0.030

Dissolved Copper (mg/L) Across Sites

High Flow Low Flow

M1 5 in 30 M2 5 in 30 M2 5 Year M1 5 in 30 M2 5 in 30 M2 5 Year