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STAtyDARD METALS CORP~ATIOi`i P.O. Box 247 Silverton, Colorado 81433 (303) 387-5`.33 h;arch 21 , 1983 Mr. Don Si m_oson Fermi is and Enforcement Section Rarer duality Control Division Colur ado De oartment of Fea lth X210 East Eleventh Avenue Le over Colorado 80220 Gsar Don: Re: Infernation Request - Tail Pond No. 9 Seepage Control Plan The info:~ation recuested in your letter of February 18, 1983, reeard- ing Tail Pond No. 9 seepage control, is presented below. 1. Test holes and nits were e~:cavated at the tailings pond site dur- ing the foundation investica ti on which intercepted ground wa-.er at various depths ranging from surface to ten feet. Mont to r:inq wells numbers 1, 2, 7, 11, 13, 1°, 16 and 18 (Seepage Contro:L Plan Figure 2 ) penetrate to depths averaging five feet below the tailings al]uvi um-interface (See Figure 1). It is reasonable to assume from this information that the monitoring wells recentay installed in the tailings structure embankment intercept somE~ natural ground waters; hop:ever, due to the spatial relationship between the tailing structure ponding area and well location; the majority of water sampled in the wells is believed to on gineite in the pond. 2. The tailings dcnosition site was excav ar.ed down to river gravel in the Animas Fiver Mood ?lain during the site preparation phase of tail pond construction. Excavated materials ,were either stock- piled for reclamation or used in constructing the pond starter diY.e and toe drain, dependent on material c};ar acteristi cs. The organics and Fine were stockpiled, river grave'_s meeting toe drain permeability requirements were used in constructing the: b]anket toe drain, and moraine materials meeting starter dike S DeClf].C atlOns were used in its construction. The b]anket toe drain, constructed of river gravels overlain by filter cloth, er.terids from the upstream toe of highway 110 to a distance approximately 100 feet under the tailings pond ertrtank- mCnt (see Figure 2). The remainder of the pond lies in direct contact with natural alluvium minus excavated materials.