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Mayflower Mill - Tailings Pond No. $ <br />Seepage Control Plan <br />Page 3 <br />of the toe drain system at localized areas, and visual seepage from the <br />embankment toe is occurring. Upon exiting the embankment toe, the seepage <br />waters drain to the southwest corner of the embankment- highway abutment, <br />are collected there, and returned to the pond interior. <br />Concern was raised by Department of Health personnel during a site visit <br />that seepage waters from the pond may be impacting adjacent ground and <br />surface water quality. In compliance with requirements placed at Part D <br />of the discharge permit issued for the mill facility, Standard Metals <br />Corporation implemented a study to determine the quality of seepage waters, <br />and efforts which could be effected to eliminate the seepage. <br />Design criteria employed in the construction and operation of Tailings <br />Pond No. 4 was completed by F. M. Fox and Associates, consulting engineers, <br />in the summer of 1976. During the summer of 1982, F. M. Fox was contracted <br />to perform an interim inspection of Tailings Pond No. 4 to determine the <br />current status of tailing pond construction, and in conjunction with <br />Standard's seepage control study, to address the visual seepage occurring <br />at localized points the tailings embankment. The seepage control part <br />of the study performed by F. M. Fox consisted of two phases: a field <br />investigation, and laboratory analysis of samples collected in the field. <br />Activities conducted during the field investigation included installation <br />of water quality and phreatic monitoring wells at selected points of the <br />tailings e .a . , an es ole drilling to obtain samples for laboratoty <br />analysis. Constant head and falling head Permeability tests were conducted <br />in test wells 2, 11, 17, and 19 (see Figure 2 ) to detgaim -the i^-Sit <br />permeability of the toe drain. Upon completion of the field investiga- <br />tion, samples collected were transported to the laboratory to determine <br />moisture content, dry densiti -es, and size class distribution of the embank- <br />ment materials. <br />c A"1/ <br />Results of the seepage study revealed that seepage waters occuring along <br />the embankment were caused by three factors: <br />1. High uhreatic levels in the berm. <br />Migration of pond water through the roadbed at the northeast <br />abutment of the tailings pond with the roadbed. <br />Z <br />(:"-) Infiltration of the Animas River into the toe drain during <br />/ periods of high run -off. <br />Upon reviewing the results of the study determining the cause of seepage <br />from Tailings Pond No. 4, Standard Metals Corporation has developed the <br />following plan for controlling that seepage. <br />