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UNITED STA I ES ENVIRONMENTAL PROTECTIGi4 AGENCY 999 <br /> REGION VIII <br /> 999 18th STREET - SUITE 500 <br /> DENVER, COLORADO 80202-2466 <br /> _N Ref : SWM-DW <br /> MEMORANDUM <br /> SUBJECT: Draft Reports Relating to Proposed Sunnyside Mine <br /> Closure <br /> FROM: Paul S . Osborne <br /> Regional Ground Water Expert <br /> TO: J. David Holm, Director <br /> Water Quality Division <br /> Colorado Department of Public <br /> Health and Environment <br /> and <br /> Rob Walline, Chief <br /> Mining Waste <br /> As requested, I have reviewed the preliminary reports by <br /> Simon Hydrosearch relating to the proposed closure of the <br /> Sunnyside Mine. Generally, I am surprised that a Company would <br /> submit such poor reports in support of a proposal of this <br /> magnitude. The reports contain a great deal of anecdotal <br /> information and do not contain the level of information on site <br /> geologic and hydrologic conditions, mine workings, year round <br /> water quality data for potentially affected mines and springs, <br /> etc. Based on my review, I believe there is a large potential <br /> for flow out of the plugged mine into nearby mines, especially <br /> the Mogul Mine, through a combination of open workings and the <br /> vein and fractures in the area. I would anticipate significant <br /> flow of bad quality water. I have numerous questions and <br /> comments as a result of my review. The following two sections <br /> summarize these questions. <br /> Preliminary Characterization of the Hydrology and Water Chemistry of <br /> the Sunnyside Mine and Vicinity <br /> 1. Page 9 , Last Paragraph <br /> The report indicates that pyrite in propylitized rocks makes <br /> up between 0 . 1 and 2 . 0 percent of the rock volume. This is <br /> based on a general reference rather than site specific <br /> knowledge. It should be noted that a pyrite content in the <br /> host rock as high as 5 percent has been reported at <br /> �� Printed on Recycled Paper <br />