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Mr. Don Simpson, Permits and Enforcement <br />Tailings Pond No. 4 Seepage Control Plans <br />Page 2 <br />Seepage control activities described at items 2 and 3 have been implemented <br />during the past six months and have been successful in reducing the amount <br />of seepage occurring at the tailings embankment toe. Specifically, seepage <br />flows occurring at the toe averaged 100 gpm in July 1982, and during the <br />same period in 1983, seepage flows have been reduced to 10 to 20 gpm (see <br />figure 1). Though seepage volumes at the embankment toe have been signif- <br />icantly reduced by implementation of proposed seepage control procedures, some <br />visible seepage is still occurring and installation of a drain and sump system <br />to collect and return seepage waters is now being investigated. Final de- <br />termination on the design and installation specifics for the seepage collec- <br />tion system as discussed is not possible at this time because modification of <br />the mill grind circuit to enhance recovery of targeted minerals is currently <br />being evaluated. Grind circuit modification may result in alteration of mill <br />tailings depositional methods which will ultimately impact seepage pathways <br />occurring in the present tailings embankment. In response to the possibility <br />of mill grind circuit modifications, determination on final seepage control <br />plans for Tailings Pond No. 4 will not be made until October 1, at which time <br />modified tailings embankment design criteria, if required, are completed. <br />If you have any questions or comments on the enclosed information, please <br />contact me. <br />WD : m b <br />Very truly yours, <br />STANDARD METALS C <br />William Dotterrer <br />Environmental Engineer <br />