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MIN c. ID # OP. PROSPEC'~l• ~ll#: M-1977-300 • PAGE: 5 <br />INSPECTION DATE: 8-10-00 ItJSPECTOR'S INITIALS: ACS <br />35 of the report titled "Responses to State of Colorado Mi~Zed Land <br />Reclamation Division Comments on Waste Pile Related Portio~is of Permit <br />Amendment Application" prepared for Cotter Corporation by 1~ICDermid <br />Engineering Associates and Geo-Hydro Consulting. Under the=_ section <br />titled "Concentration of Constituents at Base of Pile Leacized from waste <br />Pile Material" a ratio is used to estimate the concentrati~~n of a list <br />of contaminants in water emerging from the base of the dumi~s resulting <br />from a surge of water incident on the surface of the pile. The ratio is <br />applied to the concentration of the contaminants derived from leaching <br />tests, and is equal to the estimated time for an aliquot o.E water to <br />percolate through the pile divided by the time period used in the <br />leaching tests. The determination in the appendix E-4 rep~~rt that water <br />exiting the toe of the dumps would not have an adverse imp+sct on Ralston <br />Creek water quality is largely predicated on the water quality <br />projection resulting from the use of the ratio. The Division does not <br />concur with the inherent assumption used in the applicatio~z of the ratio <br />that the concentration of a contaminant leached from the w+3ste rock <br />increases linearly with contact time between the water and the rock. <br />Cotter stated that considerable data has been generated si~zce the <br />approval of the 1983 permit amendment, and that this data ,supports the <br />conclusion that the mine waste dumps do not pose a threat to the water <br />quality in the creek and the beneficial use of that water. These data <br />were generated as a result of geochemical testing, acid base accounting, <br />and water quality monitoring. Cotter agreed to provide th~~ Division <br />with a report of the available information relating to the potential for <br />water quality impacts caused by the nature and location of the dumps. <br />The due date for this report is established as November 6, 2000. <br />cc: Carl Mount, DMG <br />Tim Pierce <br />Cotter (:orporation <br />Schwart::walder Mine <br />P . 0 . Bo:c 1017 <br />Golden, CO 80402 <br />I & E Contact Address <br />NAME Steve Landau <br />OPERATOR Cotter Corporation <br />STREET 12596 West Bayaud Ave. Suite 350 <br />CITY/STATE/ZIP Lakewood, CO 80228 <br />