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1-1 1.0 INTRODUCTION D'Appolonia Engineers-Constructors, Inc. (D'Appolonia) was contracted by Nomestake Mining Company {Homestake) to provide engineering design and construction of remedial measures aimed at correcting seepage problems .~ associated with the lower tailings dam at the Bulldog Mountain Operation near Creede, Colorado. The remedial measures consisted of a slurry wall cutoff and ~ pump-back system construction to collect and return seepage to the impound- ment. An investigative dam foundation grouting program vas also initiated to evaluate the feasibility of reducing seepage from the pond by this measure. Monitoring wells were installed to allow evaluation of system success. The construction activities Eor these remedial measures were completed over the period from June 28 to August 25, 1982. This report presents the design and the as-built details of the construction, and assesses, to the extent possible with current data, the effectiveness in achieving the goals of the program. The lower tailings dam, located approximately 1-1/2 miles south of the Bulldog Mountain Operation mine and mill (Figure 1), serves as a disposal reservoir for tailings containing cyanide from silver ore milling operations. The dam has been experiencing underseepage of tailings solutio n since 1978. The history of the pond seepage and the geologic conditions responsible for the seepage have been summarized in two previous reports by D'Appolonia.# In early 1982, prior to construction activities at the dam, surface seepage collected downstream from the pond was approximately 80 to 120 gpm. An unknown quantity of seepage was passing downstream in subsurface flow. The surface seepage was being returned to the pond with a surface collection and pump-back system installed in 1978 by {Lomestake. The remedial construction *Phase I, Remedial Measures for Lower Tailings Dam, June, 1981; Phase II, Remedial Heaeures for Lover Tailing; Dam, October, 1981. I)~P~L®FoT~