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01/31/2003 17:09 2799186 DOTY 9, ASSOCIATES <br />mji ,' ( (Jt> J <br />DOTY & ASSOCIATES <br />ENVIRONMENTAL, GROUND-WATIUR AND WASTE MANAGEMENT ENGINEERS <br />1440 BRICKYARD ROAD <br />SUITE 1 <br />GOLDEN, COLORADO 804W4054 <br />VOICE: (303) 279-9181 <br />FAX: (303) 279-9186 <br />Mr. Christopher C. LaRue <br />Adams County <br />Department of Planning & Development <br />4955 East 74th Avenue <br />Commerce City, Colorado 80022-1535 <br />Subject: Prediction of Impacts <br />Off Partnership Irrigation Well <br />Conditional Use Permit Application <br />Case No. EXG2002-00004 <br />120th Estates Partners, LLP <br />Dear Mr. LaRue: <br />PAGE 01 <br /> <br />htt(f:l/www.dotyeng.com <br />bpdoty@dotyeq.oom <br />January 28, 2003 <br />1502-01 <br />RECEIVET <br />FES 0.1:2003 <br />Division of Minerals and Geology <br />This letter has been prepared on behalf of the Don and Jeanne Off Partnership and <br />presents my professional opinion that the gravel mining operation proposed under the <br />above referenced conditional use permit application will cause significant impacts to <br />the irrigation wells on the Off Partnership Property. <br />PROPOSED USE & HYDRAULIC FEATURES <br />As we understand the application, the 1201h Estates Partners propose to mine in the <br />dry to a depth equivalent to or slightly above the water table. Based on depth to <br />water information from the Off wells and TH-4 drilled by the applicant near the Off <br />property, the depth of dry mining is likely to be approximately 10 feet near the Off <br />property. A slurry wall will then be constructed to fully enclose the operation; the <br />slurry wall will be keyed into bedrock. Mining will then proceed to the full depth of the <br />alluvial deposit, after which the underlying claystone materials will be used to <br />construct a clay liner on the upper portions of the slopes such that the resulting pit can <br />be used for water storage. <br />The applicant further proposes a 10 foot mining setback from the Off Partnership <br />property line. Although not the subject of this letter, the Planning Department should <br />be aware that, to the best of our knowledge, the Off Partnership has no intention of <br />agreeing to setbacks less than those specified in the regulations. The dry mining <br />excavation will be sloped at 2:1 (horizontal to vertical) from original ground to the <br />water table. The slurry wall will be constructed in the middle of a 30 foot wide bench