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some minor reaction with non-coal minerals in the coal wall could have changed the composition of the water. However, the chemically inert nature of the coal in this setting would likely have led to very little chemical change in the water composition. Thus, a third assumption of the model was: If wager passed Through the coal wall from the sump to the Bear workings, that water would not have changed appreciably in composition. Other possible chemical processes by which the fault waters could have changed composition within the mine include (1) precipitation of minerals due to cooling of the waters. (2) dissolution of dust suppressants on the walls of either the Bear or the West Elk mine, and (3) off-gassing of some of the waters. None of these were evaluated, although they perhaps should not be discounted. To evaluate what chemical reactions are most likely to have taken place between the West Elk mine fault waters and the Edwards Portal seep water, the minerals within the stratigraphic section and waters in those units were approximated from general knowledge of the local stratigraphy and general knowledge of the composition of meteoric water. The possible mineral constituents which were considered were reduced to calcite, dolomite, gypsum or anhydrite, pyrite, and clays of non-specific major element composition. The possible carbon sources were reduced to the measured gases (CH, and CO,) from the faults, atmospheric CO,, soil gas CO,, and the carbonate minerals named above. The other gases, including oxygen and azgon, were considered. Possible sulfur sources were reduced to the above-named sulfates and sulfides. APPROACH For either the Division or the operator to show whether the fault waters are the source of the seep water, it is essential to explain at least the following variations in the data, going from the faults to the seep: 1. a significant loss of bicarbonate and cazbonate from the faults to the seep; 2. a significant gain in sulfate content between the faults and the seep; 3. a slight gain in calcium; 4. a slight gain in magnesium; 5. a slight gain in potassium; 6. a slight to nil gain in sodium; 7. a shift in "C from low to undetectable percent of modern carbon values to detectable pmc values; 8. a shift in'H from very low (0 to 0.97) tritium units to 1.97 t.u.; 9. a shift in pH from alkaline values (7.98 to 8.63) to slightly acidic (6.79); 10. a significant shift from the mixed S"C values of -2.7 to +10.7 %o to a very light value of - 12.9 %°; 11. a possible shift from light SD values in the fault waters (-l 14 to -126 °/ao) to a heavier SD value (-1 I ~ %o); 12. a possible shift in 5180 from light values ranging from -15.9 to -16.3 %o to a slightly heavier value of-15.6 °,Uo;