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Morro and Asaocla~es, LC <br />meq L-' and ~ 40 meq L-',respectively, mean HCO; contents of ~ 40 meq L' and ~ 3l meq L- <br />', and mean SO;' contents of ~ 5 meq L-' and ~ 0 meq L-', respectively. They also have very <br />low Ca'`' and Mgz+ concentrations (i.e. ~ <1 meq L-'). <br />14 SEHG and BEM fault waters have unusually positive S"C compositions (S"C ~ -2.7 and <br />+3.6 %o, respectively (Table 2). These waters also have essentially no'H, indicating no <br />rechazge during the past 50 years. Although these waters have extremely low'°C percent <br />modern carbon (pmc), the relatively positive S"C compositions preclude 14C dating. We <br />believe [hat appreciable `dead' COz has been introduced into these waters by oxidation of <br />abundant CH°. The addition of external CO, is also evident by the elevated HCO; content. <br />WEMLone Pine Seal <br />1 This water has a TDS of about 3,500 meq L"' and is similar to fault water except it has a <br />somewhat lower HCO; concentration (i.e. ~ 31 meq L"')and an elevated SO4" concentration <br />(i.e. ~ 23 meq L-'). Lone Pine Seal water also has somewhat elevated Ca2+ and Mgt' <br />concentrations (i.e. ~ 5 meq L-' and ~ 3 meq ~ 1, respectively). <br />The S"C composition is -5.4 %°, which is still slightly too positive to reliably calculate a 1°C <br />age. This water has a'H content of 4.05 TU. The combined factors of the low 1°C content <br />(5.78 pmc) and the elevated'H mean that [his water has mixed origin and [hat some of this <br />water is modem. Obviously, most of this water has a fault origin and it should therefore have <br />isotopic compositions similar to fault water. It is our understanding [hat some surface water <br />has been introduced into the NW Panels sealed sump from both mining operations (longwall <br />runoff) and perhaps some Lone Pine Gulch colluvial inflows. Mixing of surface and fault <br />water reasonably explains these isotopic compositions. <br />Edwards Portal Spring <br />The solute composition of Edwards portal spring water is fundamentally different from fault <br />groundwater. This water has a TDS of about 4,300 mg L-' and is of the Na'-Mgr'-SO;--HCO; <br />type. Of greatest significance are the Nor' and SO;" contents. Edwards portal spring water <br />has a Nor' content of only ~ 33 meq L-' and a S0 content of ~ 40 meq L"'. <br />Both Nay and SO;- may be considered as relatively conservative species in this investigation. <br />We may consider [hem as conservative species for three reasons. First, the Nay content of the <br />water in the NW Panels sealed sump is primarily a mixture of fault waters. This water will <br />therefore have a statistically greater Nor' content than does Edwards portal spring water. <br />Second, the SO;- content of all waters is below the solubility limit for gypsum and anhydrite <br />(i.e. log SI < 0.00). Third, the very elevated SO;- content of Edwards portal spring water <br />relative to fault waters cannot be attributed to processes such as sulfate reduction. Process <br />such as sulfate reduction, wllich reduce SO; concentration, could be a factor if the SO;- <br />content ofEdwards portal spring water were less than the SO;' content of fault water. <br />The S"C content oCthis water is -12.9 %o, which is in the range of most groundwater. Based <br />on the 1JC content of 5.78 pmc, we have calculated a'°C age of about 20,000 years. The 1.97 <br />edwspr.doc 3 20 January 1998 <br />