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III IIIIIIIIIIIIIIII DIVISION OF MINERAL AND GEOLOGY INTEROFFICE MEMO Date: March 8, 2000 To: Bruce HumphrieC~~~~z~ ^ From: Harry Posey ~//a/J Subject: Reclamation and CERCLA investigation; Bulldog Mine, Homestake Mining Company, M-77-215 Re: Allen Cox' 25 February letter to Mike Long regazding reclamation and potential CERCLA actions at Bulldog: As Mr. Cox' letter and the USFS letter attachments indicate, the USFS intends to use CERCLA authority to address "a release or threat of release of hazardous substances from Bulldog waste rock dumps in Windy Gulch." (The USFS information comes from the Preliminary Assessment (PA) conducted for EPA.) The extent to which DMG will become involved in a potential CERCLA action at this active site is at issue. Water quality data were reviewed by DMG a couple of years ago. At that time, it appeared possible that the Windy Gulch zinc load might be from natural sources. However, as this was not proven, Homestake began a study under which they installed a monitor well between the 9360 and 9700 levels, injected dye tracer behind the 9360 plug, and instituted surface and alluvial water sampling. This study is partially complete. Windy Gulch flows subsurface through alluvium above the 97001evel. Whether Windy Gulch persistently comes in contact with the 9700 level waste rock is not known. The surface and al]uvial water monitoring should answer this question. 9;bo Windy Gulch surface water does not flow through the~}799~level waste rock; rather, the surface water is piped around the waste rock, through the alluvium. Piezometer readings at the 93601evel and the dye tracer indicate that water behind the 9630 plug probably does NOT enter the 9360 level waste. If it does, it contacts the waste only at the outermost edge, neaz the seep line which is near the center of the Gulch. Homestake has not yet delivered their water quality assessment for Windy Gulch so we do not know whether the 9360 or 9700 level waste rock dumps are contaminant sources or not. Certainly, they do release contaminants to stormwater and snowmelt, but stormwater I believe would be exempt from numeric water quality standards.