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~' <br />I~I II~'~~II~'I~~'~~ <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1 113 Sherman 51 . Room 215 J+y~~ <br />Denver, Colorado 80203 III <br />Phone: (3071 Abh-3567 <br />FA%'. 0031 A12~RIOh <br />pE['ARTMEIVT OF <br />NATURAL <br />RESOURCES <br />January 7, 1997 Roy Romer <br /> Governor <br /> lames 5 Lahhead <br /> <br />Mr. Michael Gibson EnecWive Director <br /> Michael B. Long <br />Colowyo Coal Company L.P. Division Director <br />5731 State Highway 13 <br />Meeker, CO 81641 <br />RE: Colowyo Coal Mine (C-81-019) <br />Particle Size Distribution <br />Dear Mr. Gibson, <br />This letter is in response to our recent discussions regarding particle size distribution used <br />in the SEDCAD+ Pond models and the December 26, 1996 letter addressed to the <br />Division. <br />In summary, it was previously noted by the Division that a particle size distribution of 52% <br />Fine Sand, 31% Silt, and 17% Clay was used in the Gulch A SEDCAD+ model prepared <br />by Colowyo. The Division questioned this particle size distribution due to the chemical and <br />physical data for soils noted in page 2.04.9-14, Table 3 of the Colowyo Permit. <br />Colowyo responded to this concern in a letter addressed to the Division December 26, 1996 <br />depicting a new distribution of 35% Medium/Fine Sand, 37% Silt, and 28% Clay. These <br />numbers were derived from an overall average for the particle size distribution used <br />minewide. <br />The Division believes that the particle size distribution should be based on predominate soil <br />types within the permit area as well as varying soil depths found in each soil type. The <br />Division evaluated Map 6 to determine the soil type, distribution on the mine and the <br />average depth of stripped material. The following conclusions were drawn based on volume <br />of material; <br />104 Borolls Rock Outcrop- 1% <br />14 Burnette Loam- 61% <br />17 Work Loam- 34% <br />19 Campspass- 4% <br />