Potassium Effluent Quality Criteria Amendment November 29, 2017 - PowerPoint PPT Presentation

Potassium Effluent Quality Criteria Amendment November 29, 2017

Presentation Overview • Existing Potassium EQC • Adaptive Management of Potassium at the Ekati Diamond Mine • Koala Watershed Water Quality Model Update • Request for Water Licence Amendment • Summary

SECTION TITLE Existing Potassium EQC • Current EQC for potassium for the Ekati Diamond Mine were established during the 2012 Water Licence Renewal • No generic potassium water quality guideline in existence • Site-specific Water Quality Objective Observed Trends in [K] Downstream of the LLCF (SSWQO) was developed • Long-term exposure = 41 mg/L • Short-term exposure = 112 mg/L 2

SECTION TITLE Existing Potassium EQC • Current EQC for potassium for the Ekati Diamond Mine were established during the 2012 Water Licence Renewal • No generic potassium water quality guideline in existence • Site-specific Water Quality Objective (SSWQO) was developed • Long-term exposure = 41 mg/L 1616-43 • Short-term exposure = 112 mg/L (King-Cujo) • EQC established for three watersheds (Koala, King-Cujo, and Desperation-Carrie) • Maximum average = 41 mg/L • Maximum grab sample = 82 mg/L 1616-47 (Desperation-Carrie) 3

SECTION TITLE Existing Potassium EQC • Supported by 2012 Water Quality Model (GoldSim) • Peak potassium concentrations in Leslie and Moose lakes during the 2020 ice-covered season • Stable potassium concentrations from 2010 to 2016 with no exceedances of benchmark 4

SECTION TITLE Adaptive Management of Potassium • Results from the Aquatic Effects Monitoring Program in 2013 and 2014 • differences between observed and predicted concentrations • exceedances of SSWQO in the receiving environment • Aquatic Response Framework under development, but not yet approved • Dominion developed a Potassium Response Plan (Version 1.0, March 2015): 1) Re-examine potential for potassium toxicity 2) Re-examine 2012 Koala Watershed Water Quality Model 5

SECTION TITLE Adaptive Management of Potassium • Re-examination of potassium toxicity led to the development of an updated SSWQO (July 2015; revised October 2015) • Consistent with methods recommended by CCME for a Type A Water Quality Guideline • Used a species sensitive distribution • Based on surrogate or resident taxa present in all watersheds at the Ekati Diamond Mine • Incorporated newly published and site-specific data • Short- and Long-term SSWQO underwent extensive review alongside the Potassium Response Plan (Version 1.0) • Long-term SSWQO of 64 mg/L approved by WLWB for use in all watersheds at the Ekati Diamond Mine in January 2016 • Short-term SSWQO of 103 mg/L • < 2 X Long-term SSWQO 6

SECTION TITLE Adaptive Management of Potassium • Re-examination of the 2012 Koala Watershed Water Quality Model led to better agreement between observations and predictions • updated representation of Process Plant Discharge (PPD) concentrations • changes to assumption of PPD water content • improvements to water balance • improved assumptions related to ice thickness and ice growth • Updated potassium predictions provided in July 2015 and then with Versions 1.1 and 1.2 of the K Response Plan in mid and late 2016 7

SECTION TITLE Adaptive Management of Potassium • Inconsistencies between observed and predicted concentrations in the LLCF noted over the last year • Developed and implemented an operational water management model to optimize water management in 2017 • Investigated and understood the source of elevated potassium • Updated existing Koala Watershed Water Quality Model • Potassium Response Plan (Version 1.3) submitted August 2017 (under review) 1) Water Quality Monitoring and Reporting (ongoing) 2) Investigation of Cause 3) Water Quality Modelling Update 4) Optimization of LLCF Discharge 5) Align EQC with SSWQO 8

SECTION TITLE 2017 Koala Watershed Water Quality Model • Originally developed in 2004 and updated in 2012 • Water and Load Balance Model based on GoldSim modelling software • Accounts for all inputs and outputs from LLCF • Includes sub-models of Beartooth Pit, Panda and Koala pits, and downstream lakes • Model updated in 2017 to include most recent flow, water level and water quality data 9

SECTION TITLE Model Schematic – the LLCF (Operations) 10

SECTION TITLE Model Schematic – Downstream Lakes (Operations) 3.4 km 2 39.5 km 2 Discharge from LLCF 24.4 km 2 Leslie Moose 1,400,000 m 2 Natural Watershed Nero 620,000 m 2 440,000 m 2 (local catchment) 3,700,000 m 3 1,400,000 m 3 660,000 m 3 Flow through natural streams 780,000 m 2 1,000,000 m 2 Nema 28.2 km 2 Lake Area 1,500,000 m 3 1,800,000 m 3 Lake Volume 25.5 km 2 Martine 7.1 km 2 Rennie 940,000 m 2 Slipper 1,500,000 m 3 Lac de Gras 1,900,000 m 2 6,100,000 m 3 11

SECTION TITLE Ice Formation and Effects on Under-ice Concentrations IEMA-6 • Ice forming on lake surfaces is nearly 100% pure water • During ice formation constituents (e.g., potassium) held in the freezing water is excluded from the ice and remains in the ice-free water • During winter, the volume of ice-free water decreases, but the load of constituent remains the same, elevating concentrations 12

SECTION TITLE Ice Formation and Effects on Under-Ice Concentrations IEMA-6 • The magnitude of increase in concentration in under-ice depends on the relative percent of total lake water volume that is held in ice • Lake 1: Deeper waterbodies (e.g., Cell D) concentrations under-ice slightly greater than open-water • Lake 2: Shallow waterbodies (e.g., Leslie Lake) concentrations under-ice much greater than open-water Ice = 1.5-2 m Ice = 1.5-2 m 13

SECTION TITLE Mine Plan • Panda and Koala pits are Mine Plan Component Dates used for storage of Fine Koala, Panda, and Koala North open pits 2000 to 2008 Processed Kimberlite (FPK) Underground operations 2004 to 2020 and minewater beginning Beartooth Pit 2005 to 2009 2020 Pigeon Pit 2016 to 2021 Misery Pit 2002 to 2008 and 2014 to 2021 • Lynx kimberlite processing Fox Pit 2005 to 2017 begins 2018 Sable Pit 2019 to 2027 Lynx Pit 2018 to 2020 • Sable kimberlite processing Jay Pit 2021 to 2034 begins 2019 Infilling of Beartooth Pit with minewater and 2009 to 2020 FPK • Jay kimberlite processing Infilling of Koala and Panda pits with 2020 to 2034 begins 2021 minewater and FPK End of Operations 2034 14

SECTION TITLE Sources of Potassium Loadings to LLCF • Key source of Potassium Loadings is Process Plant Discharge (PPD) LLCF Sources Other PPD 15

SECTION TITLE Potassium in Process Plant Discharge • Elevated concentrations in period 2016 to present • Previous elevated concentrations were isolated and short-lived 16

SECTION TITLE Process Plant Discharge Geochemistry Potassium Study Investigation of Cause/Source Mitigation IEMA-3 • Elevated concentrations of potassium in PPD • No addition of potassium in Process Plant Geochemical investigation to better understand properties of ore • Laboratory testing program on FPK samples collected in Cell B of the LLCF, PPD samples, and ore samples collected from Fox, Misery, and Pigeon open pits, and the Koala Underground 17

SECTION TITLE Process Plant Discharge Geochemistry Potassium Study Results Solution K + K + Ca 2+ Cation Ca 2+ K + K + Ca 2+ Exchange K + K + Ca 2+ Na + K + Na + K + K + Ca 2+ Na + Na + Ca 2+ ore ore K + Misery Ore - ↑ K Fox Ore - ↑ Na 18

SECTION TITLE Predicting Future Potassium in Process Plant Discharge • 2018 – 2033: Misery will not be primary feed • Thus two options for predicting Predicted PPD Observed PPD potassium: 1) Geochemical predictive relationship between Ca and K, with model varying K Option 2 based on predicted Ca 147 mg/L 2) Set minimum calcium concentration based on calcite dissolution • Base Case = Option 2, minimum 147mg/L potassium in PPD • Greater than concentrations over most Option 1 (predictive of history of PPD production relationship) • Greater than concentrations predicted using Option 1 • Uncertainty remains, but only relevant for predictions from 2027 - 2039 19

SECTION TITLE Calibration – Water Quality Cell D Cell E Max. Avg. EQC = 41 mg/L 20

SECTION TITLE Calibration – Water Quality SSWQO = 64 mg/L SSWQO = 64 mg/L 21

SECTION TITLE Calibration – Water Quality SSWQO = 64 mg/L SSWQO = 64 mg/L 22

SECTION TITLE Future Predictions - LLCF ECCC-1 Cell D • Concentrations peak in winter 2020/2021 • Post 2021 concentrations fall as PPD is deposited in Panda and Koala pits • Concentrations rise from 2027/2028 as water is decanted from Panda and Koala pits to LLCF Cell E Proposed Max. Avg. EQC = 64 mg/L • Concentrations peak 2038/2039 when decanting ends Max. Avg. EQC = 41 mg/L 23

SECTION TITLE Future Predictions - LLCF ECCC-1 • Potassium in Cell E of the LLCF predicted to exceed 41 mg/L in the open-water season in next two to three years • Passage of loadings from recent PPD from Cell C to Cell E • Operating level in LLCF does not allow storage of all inflows for period of exceedance of 41 mg/L • Predictions also show potential exceedance of 41 mg/L in 2030s • Uncertainty associated with potassium concentrations in Sable, Lynx, and Jay ores • Water from Panda and Koala pits will not be pumped to the LLCF until 2027 24