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• <br />JEROME GAMBA & ASSOCIATES, INC. <br />CONSUUING ENGINEERS k LAND SURVEYORS <br />201 CENTENNIAL, SUffE 306D <br />P.O.80X W58 <br />GLENWOOD SPPoNGS, COLORADO 81602-1458 <br />PHONE (803) 945-2550 FAX (303) 945-1410 <br />Mined Land Reclamation Division <br />Department of Natural Resources <br />1313 Sherman Street Room 215 <br />Denver, Colorado 80203 <br />~ III IIIIIIIIIIIIIIII <br />999 <br />19 April 1990 <br />Attn: Gregg R. Squire, Reclamation Specialist <br />Re: Response to Adequacy Review of Eagle-Gypsum Amendment <br />File No. M-84-041 <br />The following responses are titled and numbered the same as <br />John Doerfer's letter of April 18. <br />Exhibit D - Mine Plan <br />1. Native rock, boulder and cobble riprap will be placed at the <br />culvert discharge points for erosion control. <br />3. a. TR-20 models were run for the three areas draining to the <br />sediment check structures. The boundaries of the three areas are <br />drawn on the Exhibit C, Mine Plan maps. The three areas are <br />titled, "Mine", "Waste" and "Process". These areas were evaluated <br />for 100 year 24 hour storms. The areas of potential disturbance <br />within the above noted drainage areas, were also evlauated on the <br />basis of the Universal Soil Loss Equation (Technical Note 50, <br />USDA-SCS, Rev., Feb. 1984.). <br />UNIVERSAL SOIL LOSS EQUATION A = RK (LS) CP <br />R = 20 (FIG. 1 MAP) <br />K = .17 ASSUMPTION FROM ONSITE OVSERVATIONS OF THE COHESIVE NATURE <br />THE GYPSITE SOILS. <br />(LS) = FACTOR FROM TABLE 2 BASED ON LENGTH AND SLOPE OF AFFECTED <br />AREA BETWEEN VELOCITY BREAK CONTOUR STRUCTURES. <br />C = .45 (FROM TABLE 6, ASSUMING WORST CASE FOR VEGETATION COVER) <br />P = 1 (ASSUMING UP fi DOWN HILL SLOPES BETWEEN VELOCITY BREAK <br />CONTOUR STRUCTURES--WORST CASE CONDITION) <br />Soil density 110 pounds/cubic foot <br />TOT. CU <br />Area seq. acres L S R K (LS) C P A TONS FT <br />process <br />6 1 5.3 1000 5.0 20 .17 1.6 .45 1 2.44 13.0 <br />stockpile <br />haul rd 2 3.2 200 10.0 20 .17 2.0 .45 1 3.06 9.8 <br />22.8 415 <br />