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Technical Revision No. 86 Page 2 <br />"y. August 12, 1999 <br />As stated previously, a revised SEDCAD model for the Shaft #3 SAE has been included with this <br />response letter. This revised SAE model is also intended [o comply with the abatement step <br />associated with NOV CV-99-005. <br />The factors used in the model were selected based on actual conditions of the Shaft #3 site. The <br />cut slope above the shaft site is primarily sandstone outcrop, with the remaining area covered <br />with an aspen fiber erosion control blanket, and soil with approximately 30 percent vegetation <br />cover. According to the SEDCAD model the amount of sediment generated is 0.64 ml/1, which <br />is slightly above the minimum standard of 0.5 mVl. It should be noted that the West Elk Mine <br />has received a lot of rain in the last two weeks, and there is no evidence of significant erosion or <br />sedimentation around the site. However, MCC will install a plunge pool along the flow line of <br />the sediment ditch prior to culvert CSLY-22 to settle out a majority of the sediments to ensure <br />that the site is not contributing excess sediment to the drainage basin. MCC has used these <br />plunge pools successfully at the Lower Refuse Pile and at the main topsoil stockpile. <br />Please call if you have any questions. <br />Sincerely, <br />Christine E. Johnsto <br />Environmental Eng r <br />cc: Henry Barbe <br />Phil Schmidt <br />v86d.doc <br />