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1 Ground water quality in the permit area has been affected by extensive underground mine workings, hence, ground waters are no longer "natural", but rather have been affected by oxidation. Increased oxygen in the ground water has accelerated weathering reactions of minerals present in the coal and rock strata. Increased oxygen in ground water or mine waters can increase the concentration o[ iron, sodium, sulfate, and bicarbonate in solution. Ground water in the permit area falls into one of two groups characterized by TDS levels. High TDS waters (greater than 1000 mg/I) are associated with abandoned underground workings, while low TDS ground water (less than 1000 mg/1) are dominantly "natural" waters with little or no effects from [he underground workings. High TDS waters are a sodium sulfate-type water, while low TDS waters range between sodium bicarbonate and sodium sulfate bicarbonate waters. This variance in the low TDS water chemistries reflect both changes in chemistry which normally occurs along a flow path, and the incorporation o[ a small component of ground water from old underground workings. Deep well water quality varies over the site from formation to formation and within formations. Three wells are sampled in Hydrogeologic Sector I with the type of waters varying from a strong sodium sulfate type at W82-11C to a sodium sulfate/bicarbonate type at W82-12L, to a strong sodium bicarbonate type at W82-tOW. The waters are moderate to highly mineralized with moderate concentrations of iron and low concentrations of trace metals. This high degree of variation is caused by the degree of oxidation from the underground mine workings. Well W82-12L was monitored for water quality during firs[ quarter of 1988. A summary of all data collected from the well is presented in Appendix 2. Results indicate a stable condition over the five years of sampling. Four wells were monitored in Sector II (W82-4L, W82-4C, W82-SR and W82-8T2). Water quality within this sector compares closely. The water in all o[ the wells is a sodium bicarbonate with moderate mineralization, SAR and iron concentrations. All o[ the wells exhibit low concentrations of trace metals. Data [or well W82-8T2 collected over the five years of monitoring is presented in Appendix 2. Quality has been consistant over the period. One deep well (W82-2L) has been monitored in Sector III over the past five years. Because of the technical revision approved in June 1988, water quality monitoring of the Trinidad Sandstone was moved from Well 8T2 in Hydrologic Sector II to Well 15T in Hydrologic Sector IIf. Water quality of Well 15T is significantly different from 8T2, being much lower in TDS, although would still be considered a sodium bicarbonate water. Water quality sampled in well 2L is similar to that which was sampled in Gordon Arroyo (W82-19A) in that it is a highly mineralized sodium suI(ate/bicarbonate water with moderate SAR and iron concentrations, high TDS and conductivity, and low trace metals. Data collected over the past five years is presented in Appendix 2. Comparison of the hydrogeologic sectors within formations may be done from examining Stations W82- 12L, W82-4L and W82-2L in Sectors f, II, ITI and Stations W82-11C and W82-4C in Sectors I, and II, respectively. Analysis indicates that the underground workings of the Cameron Seam in Sector I has changed water quality from the type of water sampled in the seam in Sector ][. Water in Sector I has much higher quantities of sodium, sulfate and TDS with a lower pH. Waters within the Lennox Scam are also affected by the exposure time to underground workings over the permit area, accounting for the variation in water quality. Sector III (Well 82-2L) exhibit higher concentrations of sodium, sulfate, and TDS than in wells W82-4L and W82-12L. Metal concentrations in the three wells are similar.