2009-05-12_GENERAL DOCUMENTS - C1981025

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Seepage was noted in the vicinity of the No. 1 Mine portals on April 28, 1988. This water was determined to require treatment (a pH of 6.8, suspended solids of 2,180 mg/l, and recoverable iron at 120.6 mg/1). Collection systems were installed, and discharge was treated by a drip hydroxide system to lower the pH and precipitate the iron, with detention. The drip system was determined to be unnecessary; detention without chemical treatment was sufficient. This flow now comes from the No. 1 Mine airshaft and is conveyed to the current passive treatment system. The current treatment system consists of collection and transmission pipes, and a series of ponds (Long Pond, Treatment Pond 1, Treatment Pond 2, and the option for additional treatment in Pond P-9). There is no mixing of surface runoff from disturbed areas with these mine water discharges. Water from the mine water treatment ponds bypasses sediment ponds and is discharged to North Thompson Creek at CDPS Outfall 001. The locations of the portal areas, the mine water collection system, and treatment ponds are shown on Drawing D-3-2 of the PAP. Analyses on September 8 and October 12, 2002 of the untreated discharge from the No. 1 Mine indicated that the untreated discharge met water quality parameters of the CDPS permit requirements without treatment in the detention ponds. However, the discharge continues to pass through the detention ponds and discharge at Outfall 001. Prior to the middle of 1995, the mine water discharge at Mine No. 3 was from a point source inflow (spring) within the mine. This spring discharge, consistently less than 10 gallons per minute, was of good quality and, from 1986 to mid 1995, was slightly alkaline with no history of iron or sediment problems. It was piped to the surface and discharged directly to North Thompson Creek at a former CDPS discharge point 007. Groundwater inflows began to fill Mine No. 3 after cessation of mining and pumping. Flooded mine waters nearly discharged in 1993 (rose to near-portal elevation), but then resided. From 1991 throughl993, iron (total) concentrations in the spring flow were below 0.02 mg./l. Concentrations of iron in the spring discharge rose from values around 0.02 mg/1 on April 30, 1994, to 0.055 mg/1 on May 16, 1995, and a significant increase in discharge flow rate and concentrations of some parameters was noted on June 26, 1995. Mine water elevation measurements indicated that the No. 3 Mine had flooded to the portal elevation. The discharge (combined spring and mine overflow) jumped to 67.5 gallons per minute. Iron concentrations rose significantly from 0.055 mg/1 on May 16, 1995 to 6.21 mg/1 on Jun 26, 1995. TSS rose from <10 to 55 mg/l, and TDS from 845 to 1150 mg/1. By July 25, 1995, flow had dropped to 34.7 gallons per minute, TSS fell to 35 mg/l, but TDS rose to 1235 mg/1 and total iron to 6.82. These values exceeded CDPS standards established for Mine No. 1 discharge. Outfall 007 discharge was conveyed to the water treatment systems established at Mine No. 1 for treatment effective August 11, 1995. Except for one known date (inspection of April 26, 2001), there has been Mine No. 3 discharge reported in periodic inspections since the 1995 event. By dilution, combined untreated discharges from Mine No. 3 and Mine No. 1 were in compliance with the prior approved CDPS permit parameter limits (measuring 0.03ppm on December 5, 2005, the last sample taken prior to the termination of the CDPS Permit). However, the combined discharges are currently treated and discharged to North Thompson Creek at the permitted location of Outfall 001. North Thompson Creek C-1981-025 Permit Renewal 05 12 May 2009 21