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Cowaut,~wa <br />M•Da0a00,[• <br />Charles F. Leaf, P. E. <br />tlLVwows <br />f 30]ISSf~0030 <br />raAiU'.G gDDRESS~. OFFICE: <br />x412 EAST M1',U LBERRV - 173 317 SOU7M RIE LDRUM <br />FORT COL LINS, COLORADO 80521 FORT COLLINS, COLORADO 80521 <br />February 27, 1978 <br />EYRLIIATIOr+ OF ON-SITE EROSION <br />CONTROL EFFEC7IVEtIESS At+D SEDIi4ENT YIELD <br />AT ORCHARD VALLEY MINE <br />by C. F, Leaf, P,E. <br />I PITRODL'CT I ON <br />• `his report is <br />implenented as part <br />Valley "ine. The p <br />for calculating the <br />discussion of these <br /> <br />an analysis of erosion control measures that wi;l be <br />of the construction of drainane facilities at Orchard <br />~ocedures used herein are the best currently available <br />ariounL of erosion from Orchard Valley ?line. A detailed <br />procedures is presented in Arrendix I. <br />CRITERIA FOR SIZING <br />SEDIMENT RETENTION P0.'+DS <br />Federal regulations developed in response to the surface ttininn Control <br />and ?eclamation Act (PL' 95-87) contain certain criteria frr sizing settling <br />ponds based on the area disturbed by mining. Specifically, 0.2 acre-foot <br />per acre disturbed must be allocated to s?diment dead storage in addition to <br />providing enou0h capacity to contain a 10-year, 24-hour storm event. Hor,ever, <br />the 0.2 acre-foot requirement may be reduced depending on the amount of erosion <br />• control upstrean from the settling ponds. "Credits" are Given for such controls <br />as burfer strips, revenetation of slopes, and drainane systems. <br />