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- ~T1'~TE OF COLORP~DO DIVISION OF MINERALS AND GEOLOGY Depanmenl of Natural Resources 1 313 Sherman 51., Room '_ 15 Dem•er, Colorado 80?03 DIVISION O F Phone 130319ab-3sh~ MINERAL S FA%: 13031 93.-8106 & GEOLOGY RECLAMATION MINING•SAF ETY Date: March 3, 1999 Bill Owens Governor Greg E. watcher To: Steve Shuey E><ecmive Direnor Michael B. Long From: Harry Posey (~ ~ Division Director Re: Homestake Mining ompany; Bulldog ine; M-77-215 Upon reviewing the report on the Bulldog situation submitted by Alan Cox (Homestake) on Febtuazy 22, 1998, and from discussions with you and Allen Sorenson I would concur that the adit plug valve can be closed prior to spring melt. This presumes that if the pressure sensor indicates a rise in the static water level above the collar elevation of the A-59 raise, then the valve would be re-opened, and adit discharge water would be properly dischazged. It is further presumed that later this year, Homestake will inject a tracer in the adit behind the plug and monitor for it appearance in the area. The purpose of the tracer study is to verify that the adit water is tributazy to groundwater rather than to Windy Gulch or Willow Creek, in accordance with DMG's MOU with the CDPHE-WQCD. I would offer the following synopsis of the Bulldog hydrology and geochemistry. There are three geologic components of practical significance to this discussion. All are of Tertiary age and formed, oldest to youngest, in the following sequence: • rhyolite bedrock, • Creede Formation sedimentary rocks, and • mineralized bedrock veins and mineralized Creede Formation. The Bulldog workings consist, essentially, of the following elements: • 9700 level adit. This adit progressed westerly through generally unmineralized rhyolite bedrock. • 9700 level winze. This winze connects the 9700 level with the 9360 level, below, and was driven in essentially unmineralized rhyolite bedrock. The purpose of the 9700 level adit and winze was to provide ventilation to the 9360 level and below and to serve as a secondary escapeway. • 97001evel dump. This dump consists of waste rock from the 9700 level adit and the 9700 level winze, and has been reclaimed. 93601evel adit. This adit was driven westerly for a short distance, into the Creede Formation then fumed northward, still in Creede Formation then into rhyolite bedrock, on a trend sub-parallel with the hill slope on the west side of Willow Creek. Driving records indicate that the most significant amount of water was intersected at the Creede Formation rhyolite bedrock contact. Once in the rhyolite bedrock, the adit followed a mineralized vein. However, either the degree of mineralization or the assay grade was not sufficient to warrant upward sloping because at only a few locations