Jericho Aquatic Discharge Assessment Presented by: Bruce Ott, Senior Environmental Scientist, AMEC Earth & Environmental

Water Quality Assessment Based on supplement work by: –SRK contaminant loading water balance regional and LSA climate analyses discharge concentration estimates –Greisman/Dunbar Lake C3 and Carat Lake dilution modelling Used CCME Guidelines as No Chronic Effects Level

CCME Guidelines Copper – mg/L Cadmium – mg/L Nickel – – mg/L Chromium (Cr 6+ ) – – mg/L Molybdenum – mg/L (BC 1 mg/L) Ammonia (unionized) – approx. 2 mg/L Nitrate – 15 mg/L (proposed)

Water Quality Assessment Assumptions - Operations One discharge point for all Jericho water: Water is discharged from the PKCA polishing pond into Stream C3. The sewage treatment plant discharges to the PKCA. All mine water is routed to the PKCA prior to discharge. All uncontaminated water is routed through ditches and the Stream C1 diversion.

Scenarios Examined Out of the range of scenarios that could be examined, the following were chosen as they represent the variation that could be encountered during operations: –extreme low flows; maximum contaminants –extreme low flows; average contaminants –average flows; maximum contaminants –average flows; average contaminants

Water Quality Assessment Operations Scenario 1: Extreme Low Flows and Probable Maximum PK Discharge Concentrations: Results indicate: No Health Canada guidelines are exceeded at the water intake. Some potential for chronic effects from the substances listed for the most sensitive freshwater organisms.

Continued… Mitigation during extreme low flows: –cessation of discharge –spray irrigation –addition of phosphate into the PKCA to reduce ammonia and metal concentrations (enhanced degradation)

Water Quality Assessment Operations Scenario 2: Extremely low flows and average PK discharge concentrations Protection of aquatic life guidelines predicted to be met within 100 m of mouth of Stream C3 No mitigation required

Water Quality Assessment Operations Scenario 3: Average Flows and Maximum PK Discharge Concentrations Only cadmium exceeds protection of aquatic life guidelines within 100 m of the mouth of Stream C3 Mitigation: –treatment to tie up metals in the PKCA, e.g. add PO 4 –Spray irrigation Scenario 4: Average Flows and Average PK Discharge Concentrations Cadmium exceedance ( vs mg/L)

Water Quality Assessment Assumptions - Closure The PKCA will be reclaimed to land on closure and any water flowing from Stream C3 will be essentially uncontaminated. Water from the mine area after closure discharges to the open pit. After approximately 20 years the pit will overflow through a prepared channel to sediment pond A. No active water treatment

Water Quality Assessment Closure ammonia completely oxidized prior to release metals may still be present above CCME exfiltration from Pond A if water meets health and protection of aquatic life guidelines discharge through a diffuser in Carat Lake if not to provide 36:1 dilution within 7 m diffusion of chronic not acutely toxic water

Assessment is Conservative CCME guidelines were used to indicate no chronic effects Dilution model uses conservative assumptions Sequestering of metals in the aquatic environment

General Ecotoxicology of Metals in Lakes The chemical form of the metal (e.g. complexed, chelated, adsorbed or free ionic) determines the bioavailability Bioavailability of the metal determines the toxicity of the metal Metal interaction with the components of the lake ecosystem generally reduces bioavailability Adsorption to biotic and abiotic particles suspended in the water will reduce bioavailability Increases in water hardness (i.e. calcium and magnesium levels) significantly reduce some metal toxicity

General Ecotoxicology of Metals in Lakes Adsorption to suspended algal cells, ingestion of algal cells by grazing invertebrates and transfer of metals to sediment via fecal pellets can be a major pathway of metal elimination from surface water Acclimation of fish species to elevated metal concentrations is a scientific fact with abundant support in the scientific literature Fish can physiologically adjust to higher metals concentrations in a variety of ways (e.g. increased secretion of mucus) Some metals (e.g. Cu, Zn) are physiologically necessary to maintain the health of fish populations

What are Water Quality Guidelines Water quality guidelines for metals (for the protection of aquatic life) are just that (i.e. guidelines). They are not carved in stone. They are developed by a conservative protocol that allows a very wide margin for error as the guidelines must apply to the entire range of surface waters across Canada. The water temperatures used in the studies that serve as the basis for metal water quality guidelines were not characteristic of Arctic lakes (generally these studies were conducted in the range 20-25°C). There could be major differences in the toxic responses of fish in which temperature is a significant variable

Acute Toxicity to Fish Copper – incipient lethal level: 0.33 mg/L for rainbow trout Cadmium – acute toxicity level: mg/L Nickel – acute toxicity level: 2.48 mg/L (EPA) Chromium (CR 6+ ) – acute toxicity level: mg/L early life stages Molybdenum – acute toxicity level: 100 to 1000 mg/L Unionized ammonia – acute toxicity level tied to temperature and pH Nitrate – acute toxicity to rainbow trout level 190 mg/L

Chronic Toxicity to Fish Copper – mg/L Cadmium – mg/L Nickel – mg/L soft water Chromium (Cr 6+ ) – 60 d no effects level – mg/L soft water Molybdenum – 1 – 100 mg/L Ammonia – PSL2 chronic toxicity guide 41 mg/L total ammonia Nitrate – chronic toxicity ?

Total Dissolved Solids Possible long-term (> 1 year) effect on phytoplankton and zooplankton Should not affect ecosystem function due to functional redundancy in plankton trophic levels EKATI has noted some build up of TDS downstream of Long Lake but no effects on fish observed

Summary Under average conditions discharges during mining will not be chronically toxic Options are available to mitigate if required Closure treatment can be handled passively if the open pit is allowed to fill naturally