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• Based on the two sets of water level data and the site geologic setting, the Vermejo and Trinidad aquifers in the vicinity of the mine site appear to be unconfined and highly responsive to recharge from seasonal and annual variations in precipitation. These units are likely to exhibit confined conditions further from the outcrop where overburden depths increase. In well 29-4, located furthest from the outcrop and completed in both the Trinidad Sandstone and Vermejo Formations, depths to water are approximately 80 feet. Although water Levels in this well did not fluctuate as much between the two measurement periods as did the other wells, the aquifer associated with this well may still exhibit unconfined conditions because the gravel pack extends from 200 feet to 75 feet below the surface. However it is also likely that perched saturated zones may overlie the water table at that depth. It appears from the site geologic information, groundwater levels and streamflow measurements that ground water discharge occurs primarily as mine discharge and evapotranspiration along Engleville Gulch. Baseflow does not exist except in association with the mine discharge. Groundwater recharge may occur in the northern part of the mine site along the Engleville Gulch. It seems likely that alternating reaches of discharge and recharge exist along Engleville Gulch. The discharge zones appear as either intermittent seeps or areas of evapotranspiration along the crop or subcrop of the shales and clays. Limited groundwater recharge would also be expected in the upland areas ~~ Regionally, the mean specific capacity of the Raton/Vermejo/Trinidad unit has Th\ been calculated at 0.11 gpm/f t. The mean hydraulic conductivity has been calculated at 1.88 feet per day. The mean transmissivity has been assessed at • 10.4 ft /day (USGS WRI 83-132). r / a° ~~~. 2.04.7.1.2 Water Quality The quality of the ground water in the Vermejo and Trinidad aquifers is relatively poor and generally unsuitable for human consumption. This water is used, however, for irrigation, stock and plant watering, and limited domestic purposes. On April 14 6 15, 1988 ground water samples were taken at four on- site and near-site locations and sent to the laboratory for complete chemical analyses. The pH of the water, as determined at 25 degrees C, ranged from 6.66 to 7.9. The electrical conductivity (EC), analyzed under the same conditions, ranged from 1600 to 3500 micromhos. The results of these analyses are found in Appendix 4. The chemical parameters for which the samples were analyzed are Total Suspended Solids, Total Dissolved Solids, Total Hardness, Carbonate, Bicarbonate, Calcium, Chloride, Fluoride, Magnesium, Nitrogen: Ammonia ~ Nitrate, Phosphate, Potassium, Sodium, Sulfate, Sulfide, Aluminum, Arsenic, Barium, Boron, Cadmium, Chromium, Copper, Iron, Lead, Manganese, Mercury, Molybdenum, Nickel, Selenium, and Zinc. Only Nitrate, Sulfate, and Chromium concentrations exceeded the EPA secondary maximum contaminant level (SMCL) or EPA maximum contaminant level (MCL) in the ground water samples. The sample from Well 29-4 (upgradient from the mine discharge) was generally of better quality than the other three samples. This may be due in part to the completion of the well in both the Trinidad -4-