1996-02-08_HYDROLOGY - M1977378 (5)

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Longfellow Koehler Project Page 2 The project is located within a belt of chimney type ore deposits along the northwesterly rim of the Silverton Caldera. All volcanic rock types in this area are either from the Burns or Henson Formations. There are intrusive rocks found along the concentric and radial faults associated with the volcanic activity. The area in general is considered to be highly mineralized. The project area consists of a shaft with a small access drift and corresponding waste dump, two. collapsed discharging portals with corresponding waste dumps, two mine waste dumps (estimated to contain 20,000 cubic yards) and a low pH natural pond with sediments containing metal precipitates. All water flowing through or across disturbances is exposed to pyrite and other heavy metals as well as the acidic conditions of the pond. The south collapsed adit has a general Northeasterly bearing toward Carbon Lake. The headwaters of Mineral Creek are a substantial contributor of dissolved Fe, Al and Zn as defined by the 1991-1994 sampling results of Water Quality Control Division. The site features are identified on the attached drawings. Site Loading Estimate Loading from this site is due to the intermixing of adit flows, drainage from the small basin and stormwater through a common discharge point(M-02),that has been monitored multiple times. The average results of the monitoring of M-02 for quantity and quality was used to estimate the impact of dissolved zinc from adit flows from this site. The average M-02 loading information was used and the assumption made that the same percentage attributable to waste dumps during a SGC sample session at the site is applicable to this average loading. Based on these assumptions and procedures, SGC estimates that the average daily loading for mine waste impacts at this site may be as much as 32.5 pounds of dissolved zinc per day. SGC is under no obligation to defend these estimates and they should only be used as an estimate. SGC does not represent that its mitigation project at this site will remove any specific percentage of metals loading from this site: the loading estimate contained herein does not form the basis of an enforceable permit obligation. Description of Project Hydrologic Controls Infiltration Controls The upland property has not been examined by SGC to see if there are any open stopes,glory holes or other subsidence features that may be adding water to the portal flows. The following will be done to determine whether infiltration controls have potential to reduce Adit flows.