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- -~- • III IIIIIIIIIIIIIIII • <br />~~~°~°~,R STATE OF COLORADO <br />Roy Romer, Govei <br />DEPARTMENT OF NATURAL RESOURCES <br />MINED LAND RECLAMATION DIVISION <br />FRED R. BANTA, Director <br />July 29, 1988 <br />Mr. Mark Klune, General Manager <br />Valco, Inc. <br />P. O. Box 857 <br />Pueblo, Colorado 81002 <br />RE: Pueblo East Pit, File No. M-86-015, WRC Engineering Report in <br />Response to Permit Stipulation No, 2 <br />Dear Mr. Klune~ <br />Thank you for your submittal of`WRC Engineering Inc.'s report regarding <br />diversion of water from the upland arroyo through and around the pi t. area. I <br />have finally had a chance to review it and appreciate the opportunity to work <br />with you again. <br />WRC Engineering appears to have done a satisfactory study of the arroyo and <br />diversion alternative: I agree with their recommendations and agree that a <br />10-year storm is an appropriate design event for the diversion structures, It <br />is reasonable to upgrade the existing straightened portion of the arroyo so <br />water can be diverted here while mining occurs adjacent to it, to build <br />Diversion Ditch Alternative B when the area around the existing arroyo will be <br />mined, and then redivert the water back into the lake in the pit upon the <br />completion of mining. <br />I have four concerns about your plans which we should resolve <br />1. If a storm event occurs in excess of the 10-year storm and the pit <br />is flooded, what measures will be taken by Yalco to control water <br />contamination by equipment and materials (and of course for you to <br />protect your equipment and materials from the flooding)? <br />2. What measures will be taken to stabilize the diversion structures <br />from erosion (and the water from siltation) prior to flow through <br />these structures. We recommend that the ditches be revegetated as <br />far in advance as possible of expected flow (preferably at least <br />1-2 years). Sediment barrriers (check dams, hay bales, etc.) <br />should be placed as appropriate if sedimentation occurs along areas <br />with sparse vegetation. Annual ditch monitoring and maintenance <br />should be done such that problem erosion areas can be stabilized. <br />Other alternatives are available; however, they may be more <br />expensive.. <br />215 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. (303) 866-3567 <br />