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• r <br />MAYFLO'aER MILL - TAILINGS POND NO. 4 <br />SEEPAGE CONTROL PLAN <br />The Mayflower Mill facility is currently operating under NPDES permit <br />number CO-0000426 issued in August of 1982. As stipulated at Part D <br />of the permit, Standard Metals .Corporation was to develop and imp lament <br />a control program for seepage waters occurring at the toe of the N~~. 4 <br />tailings pond embankment. The following outline presents seepage ~;on- <br />trol plans developed for Tailings Pond No. 9. <br />1. Installation of water quality and phreatic monitoring wells around <br />the embankment perimeter to determine the quality and quantity of <br />seepage waters. <br />2. Switching depositional methods on Tailings Pond No. 4 from the <br />modified downstream to the upstream method in order to increase <br />the width of the beach area and lower phreatic levels in the em- <br />bankment. <br />3. Installation of a bentonite seal at the tailings embankment-roz~dbed <br />abutment to reduce seepage migrating through the roadbed. <br />4. Installation of a drain and sump system for collection of seep«ge <br />waters if the preceding measures fail to eliminate the current <br />problem. <br />DISCUSSION <br />Standard Metals Corporation operates the Sunnyside Mine and Mayflower Mill <br />facilities in San Juan County Colorado, near Silverton. The mine is an <br />underground hard rock operation employing shrink stope techniques for ore <br />removal. At the mill, desired products are extracted from the mine ore <br />by gravimetric concentration and differential flotation processes. Major <br />products produced at the operation are a lead-cooper concentrate, zinc <br />concentrate, and a gold-silver amalgam. <br />Approximately 5$ of the ore processed at the mill is recovered as merchantable <br />product. The remaining 95~, primarily ground host rock, is combined with <br />mill process waste waters and transported by pipeline to the mill tailings <br />disposal site or tailings pond. The primary function of the tailings pond <br />is to confine tailings solids in a designated area to mitigate pollutional <br />impacts of the discarded waste materials. A second function is to tempo- <br />rarily retain tailings slurry water and mill process waste waters for treat- <br />ment prior to release to the facility receiving stream. <br /> <br />