2009-05-12_REVISION - C1981025 (8)

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conductivity at outfall 001 has ranged from 1,570 umhos/cm to 3,900 umhos/cm, with an average of 2,420 umhos/cm.. The average (1995 - 2005) conductivity of North Thompson Creek was 243 µmho/cm downstream of the mine portals (versus a baseline value of 494 umhos/cm) and 183 µmho/cm upstream of the mine portals (versus a baseline value of 216 umhos/cm). Dissolved Solids There are no receiving stream standards for total dissolved solids. However, the Division considered the additional total salt load on North Thompson Creek. The measured TDS concentration at outfall 001 has ranged from 1,300 mg/1 to 2,100 mg/1, with an average of 1,600 mg/l. This compares to an average upstream concentration of TDS of 141 mg/1 (160 mg/l baseline) and a downstream concentration of 203 mg/1 (218 mg/1 baseline). Thus Outfall 001 likely contributed to the rise in concentration between the upper and lower stream monitoring stations.. Depletion of Springs and Seeps Mining may cause the depletion of springs and seeps above the undermined areas. A spring and seep survey conducted by the mine has only identified two springs within the five-year mine plan area. Both springs (designated on the mine subsidence map) flowed less than one gallon per minute, except during the spring, when site SP-2 flows of 20-40 gallons per minute were reported. Both springs flow from the Upper Sandstone and are not adjudicated. Based on the low flow and poor quality, it does not appear that the springs were, or are, a significant component of the surface water regime. On May 20, 2003, the last measurement recorded,the flow of Spring 2 was estimated at 0.125 gallon per minute. Should mining have diminished Spring 2 flows, they would now re-appear in Mine No. 1 discharges. There would, thus, not be a significant impact to the surface hydrologic balance. Water Balance There was a one-time loss from the pre-mining hydraulic regime to impounded water of the underground reservoirs from flooding of the areas of coal extraction after pumping ceased. An estimated 363 acre feet in Mine No. 1 and 94 acre feet in Mine No. 3, are stored. Discharges from the Mine No. 1 portal were noticed on April 28, 1988, and from the Mine No. 3 portal on June 26, 1995. Since these times, mine inflows have been in balance with mine discharges. There may be some increase to North Thompson Creek surface flows from diversion of upper groundwater to the portal discharges at the expense of underground recharge of aquifers. Although it is not likely that all of the mine discharge water originates in the aquifers, even this maximum discharge would not significantly affect ground water use, because there is no known beneficial use of ground water in the area of the mine. Water is also impounded in the Long Pond (0.21 acre feet), Treatment Pond 1 (0.17 acre feet), and Treatment Pond 2 (0.20 acre feet). Inflows and outflows of water treatment ponds are now in balance. There is a potential for recurring retention at Pond P-9 of a volume of 1.15 acre feet, and at the Refuse Area Stock Pond of North Thompson Creek C-1981-025 Permit Renewal 05 12 May 2009 29