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iii iiiiiiiiiiiii iii <br />_a_ 999 <br />~ s '' SHB AGRA INC. <br />y , <br />1 ~ B l Engineering&Environmenta/Services <br />'t" <br />January 21, 1994 <br />Mr. William C. York-Feirn <br />Colorado Division of Minerals and Geology <br />1313 Sherman St., Room 215 <br />Denver, CO 80203 <br />RE: Response to Questidns Raised in your Inspection Report, <br />LO/21/93, File N. M-93-041 <br />Dear Bill: <br />165 South Union Blvd. <br />Suite 516 <br />Lakewood, Colorado <br />U.S.A. 80228 <br />Phone: 303-763-8432 <br />Fax: 303-989-5525 <br />SHB AGRA Project E92-7075 <br />~EC~fi/r~, •~ <br />'~L ~ <br />JAN ~ 41994 <br />This letter responds to the five questions you raised in the referenced inspection report. <br />Question //l: <br />l.i,,l <br />Will water flowing through the various reservoirs also flow through the intervening <br />ridges? <br />Answer: <br />The mine waste rock will contain open voids which will allow groundwater to flow <br />relatively unimpeded across thebackfilled mine pit. Over time and with exposure to <br />water, slacking of shale may result in a reduction in hydraulic conductivity but relatively <br />free flow of water is expected. <br />Question #2: <br />Can the southern water bodies hold all of the water flowing in from the north? Is there <br />a contingency plan if water should overflow? <br />Answer: <br />A preliminary, generalized assessment of the water balance associated with the post- <br />reclamation mine pit has been made to evaluate the steady state Flow conditions in the <br />reclaimed pit and assess the potential for overflow of groundwater to surface water. <br />The following assumptions were made in the analysis: <br />1. The aquifer surrounding the mine pit has a isotropic hydraulic conductivity of <br />0.03 ft/day (10-5 cm/sec). <br />Ln A G R A <br />Earth &Environmenta/Group <br />