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Mr. R. Burgess <br />8/23/02 <br />Page 3 of 5 <br />conditions in Windy Gulch, it may take several years for water quality conditions to stabilize. If <br />performance goals are not attained by the end of 2005, then Homestake commits to conducting <br />additional studies in Windy Gulch to further evaluate water quality issues. <br />2. Depth, Placement and Dcsign of Cutoff Walls <br />Cutoff walls will be placed on competent bedrock. At the 9700 dump, bedrock is likely to be <br />rhyolite while at the 9360 dump it will be Creede Formation. Grouting will be conducted as <br />appropriate to seal fractures in bedrock. <br />3. Infiltration Through the Waste Rock Dumps <br />A soil cover will be placed on the 9700 dump and on the top surface of the 9360 dump that lies <br />north of the existing vegetation plot exclosure. The soil will be obtained from the existing lower <br />tailing embankment. <br />Four representative samples of soil material from the embankment were taken on July 29, 2002. <br />Two of the samples were taken near the top surface of the embankment, at the east and west ends. <br />These samples were comprised of loose tan to light brown soil. <br />Two samples were taken from the cut slope that was excavated through the east end of the <br />embankment for the drainage outlet channel. The two samples were taken about 6 ft and 12 ft <br />below the top of the embankment. Surficial soil material similar to that described above was <br />encountered to a depth of about 4 to 6 inches. Below that was a compacted soil material that is <br />brown to dark brown in color. This likely is the structural £11 material used in the embankment. <br />It is derived from the Creede Formation, which underlies the tailing area and is comprised of <br />paleoalluvial sediments. The Creede Formation is a soil-like material with a high percentage of <br />sand and silt. <br />The two surface samples were combined into Sample #1 -Surface and the two deeper samples <br />were combined into Sample #2 -Cut. Colorado Analytical Laboratories performed grain size <br />and soil nutrient analyses on the two composite samples. Results are attached. The results <br />indicate that both samples are classified as sandy loam. Both have a significant percentage of silt <br />and clay size particles, indicating that they will limit infiltration into the waste rock dumps and <br />will be effective in storing and retaining moisture. With the addition of fertilizer as <br />recommended in the laboratory report, the material should provide an adequate soil cover to <br />support vegetation. <br />The soil cover will significantly limit potential infiltration through the waste rock dumps. <br />Revegetation of the dump surface will limit erosion. <br />The overflow channels are an important component of the design but are expected to carry flow <br />rarely if ever. Storm events that could result in surface flow in the channels will be high <br />intensity, short duration storms and would result in very minor amounts of infiltration, if any. <br />Thus, infiltration from the overflow channels is not considered to have a significant impact on <br />water quality and addition of an impervious liner will result in minimal gains in performance. <br />However, to eliminate this concern expressed by the Forest Service, Homestake will modify the <br />design to include a 40 mil HDPE liner instead of the geofabric. It is noted that this modification <br />will result in additional costs for the reclamation project. <br />