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<br />37 <br />•~ shown graphically in Figure 11. This figure shows the similarity of compo- <br />` sition of the mine discharges. The major difference in relative composition <br />of the stream waters as compared to the mine discharges is a tower concen- <br />' tration of sodium. otherwise the compositions are quite similar. The <br />combined concentration of dissolved salts in the mine discharges are greater <br />than in the stream, however. <br />Table 6 is a comparison of the chemical analyses (Appendix E, Table E2) <br />of waters taken from the three bedrock wells established as part of this <br />study with the means from the Maxwell Mine discharge. The data for well <br />LA 221A is believed to be representative of the quality of the undisturbed <br />waters in the coal seam. The differences observed between the water quality <br />~ in LA 221A and of the mine discharge is attributable to activities within <br />the mine and, to some extent, to sample and analytic variability. The large <br />i <br />~ concentrations of total iron and manganese are attributed to the steel casing <br />and the elevated total zinc is due to the galvanized iron discharge pipe <br />used in the pumping system. The concentrations of dissolved iron, manganese <br />• and zinc are meaningful, but the total concentrations of these elements are <br />not. <br />,+ <br />Water pumped from LA 264 is believed to be produced from a thin fractur- <br />ed zone at a depth of about 72 ft. as discussed previously. Even though the <br />water sample from this well represents a zone high in the overburden, the <br />composition and total concentrations are very similar to the corresponding <br />parameters from LA 221A. This observation suggests a uniform water quality <br />throughout the profile. <br />The sample from well LA 218A is not representative of the coal seam <br />waters. Because the productivity of the well was small, a volume of water <br />sufficient to displace the water standing in the well bore was not pumped, <br />and the sample is believed to be contaminated with cement which would ac- <br />count for the high pH and large concentration of carbonate. <br />• The chance in the quality of waters in the Purgatoire River as a <br />result of mine discharge is an item of particular concern. The estimated <br />• ` change in selected parameters due to the Maxwell Mine discharge are present- <br />ed in Table 7. The mass balance-mixing model: <br />