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Schwartzwalder Mine -Hydrologic Evaluation of Mine Closure and Reclamation 120 <br />7.6 Underground Mine Water Quality <br />The chemistry of groundwater entering the mine is known from samples collected from seeps, drips, and <br />flows occurring from coreholes, faults, and bulkheads in the underground workings (Figure 5). These <br />samples are affected to varying degrees by chemical loading from contact with wall rocks and minerals <br />exposed to oxidizing conditions within the mine and are not necessarily representative of the background <br />quality of bedrock groundwater20. They do, however, provide insight to the variability of water quality <br />from different underground levels, rock types, and structures within the mine. The number of samples <br />collected at each location within the underground workings is listed in Table 27. Sampling locations are <br />described in Table 33. Locations above the Steve level are grouped as "shallow mine" while those at or <br />below the 700 level are included in "deep mine"analysis. Samples collected after the water level in the <br />mine had submerged many of the deep mine locations are discussed separately as "reflooded mine water." <br />Quarterly samples were collected from most underground stations during 1998 and 1999. Sampling <br />stations located in the Minnesota and Steve levels were generally dry except in the spring, and therefore, <br />only one sample was collected from each of the upper stations (WASH, CO, ILLRS, 146, and MINK) in <br />May 1999. <br />Seasonal variation in flow rate is evident in the lack of water at sample stations in the upper levels during <br />the summer, fall, and winter months. The rates of groundwater inflow to the mine (Section 5.2.1) also <br />show a seasonal variation. However, no significant seasonal variation in flow or chemistry at the deeper <br />underground sampling stations is evident. <br />20 Samples from coreholes drilled into virgin rock may be considered representative of bedrock water quality peripheral to the <br />mine. These samples include: 7J2, 15B13, 19D15(Fe), 19D15(Mn), and 19D16. <br />4109B.071116 Whetstone Associates <br />