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Carbon Isotope Composition The carbon isotope signature was the second line of reasoning used as evidence that the water issuing from the Edwards Portal spring is geochemically distinct and not the same water that came from the faults. The evidence is not unequivocal. A wide range of carbon isotope compositions is displayed by the waters sampled. Expressed as the ratio of the carbon-13 to cazbon-12 relative to a standazd (written as d"C as a per mil quantity), these S"C values range from +10.7 to -2.7 in the fault waters, certainly not consistent from fault-to-fault. Water from the Lone Pine Gulch seal and the Edwards Portal spring shows lighter carbon (S"C values of -5.4 and -12.9 respectively) than any of the fault waters. This observation doesn't eliminate the possibility that the Lone Pine Gulch and Edwards Portal spring water is fault water which has undergone cazbon-13 depletion between November 1996 (when B East Mains Fault water was first Bumped in the NW panel sump) and then the samples from Lone Pine Gulch and Edwards Portal were taken in December 1997. One possible mechanism is the simple dissolution of methane (CH,) during the time spent in the N W panel sump. No S"C values are available for either the Beaz or the West Elk mines, but coal itself typically displays a "C signature typical of marine sediments (around -25 per mil), with the associated methane typically depleted even more in the heavier isotope carbon-13 (lower S"C still) . It is not unreasonable to predict that water with S~'C such as the fault waters at West Elk, would show light carbon isotope numbers (low S~'C) after interacting with coal and coal-bed methane for a year while stored in the NW panel sumps or traveling through the B-seam coal. It must.be pointed out, however, for complete honesty, that the value of S"C presented for an analyzed sample of water directly from the B-seam itself is highly positive (+24). This is another piece of evidence which seems incongruous. So the S"C azgument is not conclusive, as water in this environment could easily obtain lighter cazbon isotopes during its residence. Data Needs From the hydrogeochemical perspective, the main data needs are information that tells us just what is the water in the N W panel sump. We have a range of chemical analyses from water. But we have no way of knowing how that relates to water in the sump. Analysis x could represent l % of the volume of water put into the sump, while analysis y could represent 80%. The best comparison of NW panel sump water to Edwards Portal spring water would be to use water that is now up against the down-dip wall of the NW pane! sumps. We would then have