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<br />March 26, 1985 <br />Getty Mining Company <br />23385 Routt County Road 33 <br />Oak Creek, Colorado 80467 <br />Attn: Mr. Kent A. Crofts <br />Supervisor, Environmental Services <br />Subject: Hydrologic Services, Review of the Adequacy of <br />Sedimentation Pond F, Foidel Creek Mine near <br />Oak Creek, Colorado. <br />Getty Contract No. 1061 (amended) <br />ISI Project No. 4214-4025 <br />• Gentlemen: <br />We have completed our review of the adequacy of your Sedimen- <br />tation Pond F. The purpose of this review was to assess the <br />capability of existing Sedimentation Pond F to control runoff <br />and sediment from additional disturbed areas as the result of <br />construction of a new coal stockpile, conveyers, crushing and <br />screening building and loadout at your Twentymile Coal <br />Company's Foidel Creek Mine. The proposed new facilities are <br />indicated by shaded areas on sheet to of 9 of Appendix 1- <br />Pond F calculations. <br />SCOPE <br />The scope of our services included the measurement of addi- <br />tional drainage area contributing to Sedimentation Pond F <br />based on a topographic map having a horizontal scale of 1-inch <br />equals 200 feet and a contour interval of S-Feet provided by <br />Getty Mining Company. Additionally, the design criteria for <br />Pond F were provided by Getty Mining Company and included the <br />10-year, 24-hour point precipitation of 1.8 inches, the <br />25-year, 24-hour point precipitation of 2.2 inches, the runoEE <br />curve number for the disturbed acreage of 71, and the sediment <br />yield Eor the disturbed area of 0.02 acre feet per acre over a <br />3 year period. These criteria were reviewed for reasonable- <br />. Hess and are discussed below. Getty Mining Company also pro- <br />vided the as-built design of Sedimentation Pond F. <br />