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Moro and Assocla~es, LC groundwater inflows into WEM. This investigation is now complete and the final report will be released in early February 1998. Thermal groundwater issuing from the 14 SEHG fault was pumped to the NE Tailgate sump where it acquired considerable total suspended solids. From the NE Tailgate sump a portion of the thermal groundwater was discharged to the surface; however, a large volume of this discharge water was pumped to the NW Panels sealed sump for underground storage and settling of suspended particulate matter. In March 1997 groundwater from the 14 SEHG and BEM faults filled the NW Panels sealed sump to the elevation of [he ventilation seals near the Lone Pine Gulch fan portal (Figure 1). Pumping to the NW Panels sealed sump was discontinued a[ that time. Discharge from BEM fault has now ceased; however, water is now flowing from a northeast extension of this fault in the 14 SE Tailgate. Solute and Isotopic Composition of Mine Waters Mean solute compositions of various mine waters are listed in Table 1. These waters include samples from eight fault-related sources in WEM (Figure 2), one sample from the 7 NWLP seal neaz the Lone Pine Gulch fan, one sample from the Edwards portal spring (Figure 1), and one sample from a Rollins Sandstone monitoring well, LP-1 (Figure 2). Table 1 lists chemical analyses in both mg L' and meq L-' reporting units. Stable and unstable isotopic compositions of various mine waters are listed in Table 2. Tables 1 and 2 contain four different groups of waters: 1. WEM in-mine fault groundwater, 2. WEM NW Panels sealed sump at the Lone Pine seal, 3. Edwards portal spring water, 4. Well water from the Rollins Sandstone at LP-1. Each of these waters has a distinct solute composition as illustrated by the shape of their Stiff diagrams (Figure 3) and their plotting locations on the Piper (1944) plot (Figure 4). Except for LP-l groundwater, the key differences between these waters are summarized below. LP- 1 is included in the tables because it is a high SO4- water from [he Rollins Sandstone from a location near the Bear Mine. It is not discussed in detail because complete laboratory analysis of the composition is not available. WEM Fault Growidwater Although 14 SEHG fault waters may be statistically distinguished from other fault waters on the basis of Na' and SO;- contents, all in-mine fault waters have similar solute compositions in that they are Na'-HCO; type waters and have small concentrations of other solutes. Solute differences between 14 SEHG and other fault waters are due to hydrodynamic partitioning in the Rollins Sandstone. The SZH and S'SO contents of these waters, discussed below, also demonstrate hydrodynamic partitioning. The two fault waters of interest to this investigation are the 14 SEHG and B East Mains (BEM). These waters have mean Na` contents of ~ 50 edwspr.doc 2 20 January 1998