PERMFILE108677 - Laserfiche WebLink

Home Browse Search

• Effects on North Thomason Creek Mining operations ceased during 1984. The mine was sealed and dewatering (pumping) of the mine was discontinued in late 1986. The mine filled by April 1988. It took approximately six calendar quarters to fill the mine. According to page 4-177a, it took an estimated 118.4 million gal{ons to fill the mine. Given the time it took to fill the mine, the depletion to Thompson Creek averaged up to 0.3 cfs. Once the mine was full in April of 1988, the depletion to Thompson Creek ceased because all the water that flowed into the mine was discharged though the mine water treatment system. Pages 4-66c though 4~6i present a narrative of the treatment system for the mine seepage water. During September 1989 a third settling pond was constructed on site to handle the No. 1 Mine water. The new pond is referred to as the long pond. The additional settling time provided by the long pond is adequate to allow the iron to settle from the mine water and be in compliance for discharge into North Thompson Creek. No chemicals have been added to the mine water since the long pond was put in service. The long pond has worked very effectively. During 1991 and 1992 cattails and algae have flourished in the long pond an have probably enhanced the treatment process. The water that is discharged into North Thompson Creek has an iron content in compliance with the NPDES permit The total dissolved solids of the mine discharge water has decreased about 43°l0 • compared to 1989 measurements. The treatment provided by the long pond is believed to contribute to the improved quality of the mine discharge. All of the water flowing into the No. 1 Mine is being allowed to flow out of the mine into the treatment ponds. Measurements of the water level in the mine are taken at two valves that penetrate a concrete bulkhead in the mine portal. One of the valves penetrates the seal approximately 3 feet higher than the other. The No. 3 Mine, (Outfall 007), has two separate so~!rces of discharge. One is from a point source (spring) within the mine that is piped directly to the surface. This good quality water was the source of the discharge from the No. 3 Mine, (Outfall 007), from 1986 through 1994. The water level in the mine fluctuated from 1986 through 1994 but no water discharged directly from the mine. During the second quarter of 1995, wet spring weather caused the mine to fill and begin discharging iron laden water. In order to treat this iron laden water, a four inch diameter PVC pipe was installed to convey the discharge from the No. 3 mine to the long pond located at the No. 1 Mine. The discharges from the mines were combined effective August 11, 1995. The combined discharge from the mines is treated by the passive water treatment system and is discharged through Outfall 001. 4-120 Revised June 1998 Rfr-o3 7~-~.a