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-, <br />STATE OF COLORADO RiC HARD D. LAMM. Govern o~ III III III III IIII III <br />DEPARTMENT OF NATURAL RESOURCES 999 <br />D. Monte Pascoe, Executive Director <br />MIlVED LAND RECLAMATION <br />423 Centennial Building, 1313 Sherman Street <br />Denver, Colorado 80203 Tel. (30~) 839-3567 <br />David C. Shelton <br />Director <br />June 18, 1981 <br />TO: Dan Mathews - 1 W~_ - <br />£ROM: Jim Pendleton 1 <br />SUBJECT: Review of We ern S e Carbon's Suplemental Submittals For The <br />Hawks Nest <br />Pursuant to your request I have reviewed the information submitted by Western <br />Slope Carbon and forward the following cormnents for your consideration. <br />~~Parking Lot Embankment Stability Calculations <br />i <br />WSC's expanded stability calculations allowed me to discover the error in their <br />material strength data, which resulted in shear strengths rough1y10 times the <br />actual test values. I have contacted the consultant who will submit revised <br />calculations to us in the near future. At that time I will review those <br />revised calculations and inform you of my opinion regarding their conformance <br />with the required static slope safety factoring for such a road embankment. <br />Preliminary Proposal For a New Waste Disposal Site <br />The disposal site proposed by WSC looks acceptable topographically. Obviously, <br />appropriate geotechnical slope stability analyses will have to be prepared and <br />submitted in accordance with Rules 2.05.3(8), 9.10, and 4.1I. It appears as <br />though WSC's proposed "pit 6" may actually be "a dam or embankment constructed <br />to impound the coal processing waste". As such it would have to specifically <br />conform with the stringent requirements of Rule 4.11.5. In any case, WSC <br />will have to complete a geotechnical analysis to determine the hydrological <br />and geological character of the proposed site. Drawing D-7 shows "water <br />trapment" in the bottom of pit 1. It will be difficult to conform with the <br />required compaction specifications if any water is in contact with coal <br />processing waste during its placement. It will also fail to conform with <br />general water quality protection requirements of the rules which deal with coal <br />processing waste. <br />The applicant should thoroughly analyze the proposed site, keeping in mind the <br />specific tasks that follow: <br />(1) Protecting the quality of surface and ground water, utilizing appropriate <br />subdrains, surface diversions, monitoring wells, etc., as required. <br />(2) Constructing a stable waste fill or waste pile, which will conform with the <br />regulatory requirements, including appropriate geotechnical mapping of the site, <br />material sampling and material strength testing, and the completion of appropriate <br />mathematical stability analyses. <br />