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. .Pa ye 6'iglrt . <br />. preliminary Adequacy~vic~v <br />Grand Mesa Coal Co. - Red Canyon Mine <br />Flay 8, 1981 <br />6. Sediment Cleanout: l/hile the estimate of sediment yield appears to be <br />conservative, GMCC should propose to clean out sediment at some portion of <br />the design sediment volume, say 60%. The Division prefers that some form <br />of permanent marker be placed at this level to assist inspection and mine <br />personnel in providing for adequate maintenance. <br />Load-out Sediment Pond: The load-out sediment pond is obviously of sufficient <br />size. However, the requirements for dewateriny, and emergency spillways aze <br />not met. Unless GFJCC can demonstrate that it is not practical, all of the <br />requirements of 4.05.6 must be met. <br />2.05.3 (5) Topsoil (Removal and .S toraye) <br />1. See comment H5 under section 2.04.9(1) of this letter regarding pro- <br />posed depth of topsoil salvage. <br />2. Topsoil stockpile locations could not be located nn the Proposed Surface <br />Disturbance Map. These locations should be more clearly depicted on the map. <br />Apparently, a separate stockpile is proposed for each area to he disturbed. <br />The maximum volume proposed for each stockpile should be estimated, and <br />approximate volumes to be removed from each stockpile and redistril.,uted on <br />the refuse disposal site during the permit term should be projected. <br />3. The applicant should provide an estimate of the acreage to be stripped <br />of topsoil during each year of the permit term, and the total acreage of <br />available topsoil within each of the areas to be disturbed. <br />3 (6) Overburden <br />1. The geotechnical investigation referenced in the application as ha viny <br />been conducted in the proposed portal and yard access to the ll2 mine should <br />be included in the application. A stability analysis must be submitted <br />for the proposed mine bench as required by 2.05.3(6)(c)(v). <br />2. The applicant states on page 122 that overburden will be removed to a <br />depth of two feet in presently undisturbed areas and 10 feet in presently <br />disturbed areas. An explanation of why these removal depths are proposed <br />is requested. <br />2.05.3 (9) Underground Development Waste <br />The application ex panels the waste disposal arc. inrlic;rt.,~d in pa-a permits. <br />The expanded refuse pile has an approximate total capacity of 500,000 cu. <br />yds., with an anticipated annual waste production rate of 33,000 cu. yds. <br />The application references two separate 9cotechnical analyses performed <br />within the mine plan area in the past. These vualyses should be included <br />within the permit documents. The application states that a geotechnieal <br />investigation conducted by Armstrong Engineers 6 Assoc., Inc., i.n May of <br />1980, was used as a reference in determining the stability of the proposed <br />fill and of its final slopes. Ilowever, the critical section analyzed by <br />Armstrong F Associates, Inc., was significantly different from those <br />depicted in drawings 2.05.3(9)-2 through 6. The` older fill Was dr_posited <br />in an existing strip pit whereas the enlarged proposed fill will occupy <br />a sloped foundational area. <br />