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DOTY & ASSOCIATES, LLC <br />ENVIRONMENTAL, GROUNDWATER AND WASTE MANAGEMENT ENGINEERS <br />1440 BRICKYARD ROAD <br />SUITE 1 <br />GOLDEN, COLORADO 80403 -8054 <br />VOICE: (303) 279 -9181 <br />FAX: (303) 279 -9186 <br />RECEIVED <br />OCT 302012 <br />Mr. Douglas M. Ikenberry, P.E. D,,,;,i of Reclamation, <br />Colorado Dept. of Public Health & Environment Mtning & Safety <br />Mail Code HMWMD- SWIM -B2 <br />4300 Cherry Creek Drive South <br />Denver, Colorado 80246-1530 <br />Subject: Request for Semi - Annual Groundwater Monitoring Frequency <br />Keenesburg Disposal Site <br />Dear Mr. Ikenberry: <br />DESCRIPTION OF OPERATION <br />http://www.dotyeng.com <br />bpdoty@dotyeng.com <br />October 27, 2012 <br />302 -17 <br />This letter requests that the groundwater monitoring frequency at the above referenced <br />site be changed to semi - annual. This is essentially a restatement and expansion of our <br />earlier request on this topic (Doty, 2008). <br />As you may recall, the Keenesburg facility was a surface coal mine that began operating <br />in 1981. The mine closed in the late 1980s and the pit was backfilled to nearly original <br />grade with stockpiled overburden material. Since 1987, ash from the coal -fired power <br />plant at the Coors facility in Golden has been hauled to the site to provide additional <br />backfill needed to complete the reclamation process. This use of ash was interpreted as <br />waste disposal and brought the facility under regulation by your Division. The approved <br />operations plan, as modified, aiso allows the facility to accept waste rock from other <br />mines on a case -by -case basis and the demolition and disposal of on -site facilities such <br />as the shop /office building. Assuming constant progress, backfilling with the approved <br />materials is expected to continue through approximately 2020. <br />Ash is placed in disposal cells that are lined with clayey overburden material and are a <br />minimum of four feet above the water table. The ash is covered routinely as it is placed <br />and, when areas approach final grade, a final cover is placed that consists of six feet of <br />clayey material. Finally, a two foot thick layer of topsand is placed over the final cover <br />and seeded to establish vegetation that is self- supporting under ambient precipitation <br />conditions. <br />In our opinion, there are three characteristics of the operation with important implications <br />relative to the frequency of groundwater monitoring. <br />