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Regional ground water flow from the west is along the coal seams, discharging into Maitland Arroyo. ' Thus, the underground workings act as drainage conduits, directing ground water into and out of the arroyo alluvium. During the wetter months, water Oows increase in the Maitland alluvium, and the watertable rises. When the hydraulic head is higher in the alluvium than in the workings, the reverse would occur, whereby surface water would recharge the coal seams and into the underground workings. Thus, the underground ' workings would also act as large storage reservoirs. The rate of discharge into or out o[ the arroyo alluvium is controlled primarily by coal permeability and ' hydraulic gradients. At the time that piezometers were installed, water levels in the underground workings were higher than in the bedrock near the arroyo as indicted by the water levels at Site W82-10 (6237 feet). Water levels in the workings of the Champion and Maitland No. 2 Mines were at 6241.8 feet (W82-12L) ' and 6240.8 feet (W82-9R), respectively. Sector II ' Sector II is bounded by Maitland Arroyo to the south and by a fault to the northwest. The sector is partially dissected by a dike which intersects the fault in the west central portion of the permit area. ' Water levels in Sector II indicate a relationship between bedrock ground water and Maitland Arroyo similar to that in Sector I. However, only limited mining has taken place in the Lower Robinson Seam of Sector [I. Variations in static water levels for the various wells indicate the increased length of time these ' units require to reach equilibrium with the water level in the alluvium beneath Maitland Arroyo. The water level in the Lower Robinson seam underground workings, however, is the same throughout Sector II as Sector f due to mining through the dike (see wells W82-6R and W82-lOR). ' Sector III ' In Sector III, a similar relationship exists between the major strata and the Gordon Arroyo alluvium. Piczometric levels at Sites W82-2, W82-3 and W82-15 are largely hydrostatic. Ground water Oow proceeds up dip from the west, moving through the strata and ultimately discharging to the alluvium of Gordon ' Arroyo. The point at which these strata subcrop beneath the alluvium is where discharge takes place. Geochemical data confirms this Oow system. The electrical conductivity (EC) of the Alluvial WeII in Gordon Arroyo, located up gradient of the Cameron and Lennox seam subcrop is 900 umhos/cm. In ' contrast, alluvial piczometers down gradient from the subcrop limit have higher EC values. This increase in EC is indicative of mine waters discharging to the alluvium. The Gordon Mine workings intersect the Gordon Arroyo alluvium just upstream from W82-21A. The intersection controls the interaction of the ' alluvial ground water discharge with the workings and bedrock ground water discharge. Gronnd Water uali t Limited chemistry sampling of "natural" ground waters in the region has been conducted as most ground waters in the area have been affected by historic mining activities. The major chemistry of "natural" ground ' water in the mine plan region is dominated by sodium and bicarbonate species. Concentrations generally range from 70 to 200 mg/I Cor sodium, and from 150 to 300 mg/I for bicarbonate. Calcium and sulfate arc also present in significant quantities. Calcium values range between approximately 50 and 100 mg/I while ' sulfate ranges between 200 and 350 mg/I, rivaling bicarbonate as the dominant ion. Total dissolved solids (TDS) values vary between 800 and 1300 mg/l, and average approximately 1000 mg/I. pH values are neutral to alkaline, varying from 6.5 to 8.2. All water quality collected from 1984 through 1988 is presented in Appendix 2 and summarized in Tnble 2.