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' Mayo and A.ssoelafea, LC <br />' meq L-' and ~ 40 meq L-', respectively, mean HCO; contents of ~ 40 meq L-' and ~ 31 meq L- <br />', and mean SO,- contents of ~ 5 meq L'' and ~ 0 meq L-', respectively. They also have very <br />low CaZ' and Mg" 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 />recharge during the past 50 years. Although these waters have extremely low "C percent <br />modern carbon (pmc), the relatively positive S"C compositions preclude "C dating. We <br />believe that appreciable `dead' CO, has been introduced into these waters by oxidation of <br />l abundant CH,. The addition of external COZ is also evident by the elevated HCO; content. <br />J WEM Lone Piste Seal <br />This water has a TDS of about 3,500 meq L"' and is similaz to fault water except it has a <br />somewhat lower HCO; concentration (i.e. ~ 31 meq L-') and an elevated SO;" concentration <br />(i.e. ~ 23 meq L-'). Lone Pine Seal water also has somewhat elevated Ca`' and MgZ' <br />concentrations (i.e. ~ 5 meq L-' and ~ 3 meq ~-1, respectively). <br />J The S"C composition is -5.4 %o, which is still slightly too positive to reliably calculate a1AC <br />age. This water has a'H content of 4.05 TU. The combined factors of [he low "C content <br />(5.78 pmc) and the elevated'H mean that this water has mixed origin and that 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. I[ is our understanding that 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 />l Edwards Portal Spring <br />J The solute composition of Edwards portal spring water is fundamentally different from fault <br />7 groundwater. This water has a TDS of about 4,300 mg L' and is of the Na'-Mg'-'-SO;--HCO; <br />type. Of greatest significance are the Na' and SO;- contents. Edwards portal spring water <br />has a Na' content of only ~ 33 meq L-' and a SO;- content of ~ 40 meq L-'. <br />Both Na' and SO;- may be considered as relatively conservative species in this investigation. <br />We may consider them as conservative species for three reasons. First, the Na' 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 Na' 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 SOa" content of Edwazds portal spring water <br />relative to fault waters cannot be attributed to processes such as sulfate reduction. Process <br />such as sulfate reduction, which reduce SO; concentration, could be a factor if the SO;- <br />content of Edwards portal spring water were less than the SOa- content of fault water. <br />The S"C content of this water is -12.9 %o, which is in the range of most groundwater. Based <br />on the 14C 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 />