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Mine Plan. An average daily ground water inflow of 5,229 ft3/day was calculated for year <br />5. To assess the impact of this inflow on Calamity Draw and the San Miguel water quality <br />during mining, it was assumed that the entire flow was discharged into Calamity Draw and <br />the San Miguel River and that the TDS level for the overburden aquifer was representative <br />of the chemical load. Tables 17-SA and 17-SB show the water quality impact computations <br />for Calamity Draw and the San Miguel River, respectively. The computations are based on <br />equations presented by Ferreira (1984) and are explained in detail in the section of this <br />Tab on 'Potential Impact of Replaced Spoils on Surface Water Quality". The duration of <br />the water quality impacts is relatively short term (5 years) and the significance of the <br />impact is negligible as TDS increases in the range of only .08 to 1.5 percent are <br />projected. These projected changes in TDS levels will in no way affect the present and <br />potential uses of the surface water and are so small that they will not be measurable. <br />Water quality impacts to Tuttle Draw and the San Miguel River at ~i is confluence with <br />Tuttle Draw are addressed in the section on 'Rotential Impact of Replaced Spoils on <br />Surface Water Quality" as pumpage of ground water inflow at the Nucla mining area is not <br />necessary. <br />• <br />Introduction. This Tab contains a determination of the Probable Hydrologic Consequences <br />of the existing and proposed mining plan on the quantity and quality of surface and ground <br />water in the permit and adjacent areas. The following discussion is divided into six <br />sections. They are as follows: 1) overburden, interburden and underburden <br />characterization; 2) the controls on ground water quality, including mechanisms for the <br />production of acid, mineralogy and neutralization potential; 3) geochemical modeling; 4) <br />the effects of irrigation on the ground and surface water chemistry; S) potential impacts <br />of replaced spoil on ground water quality; and 6) potential impacts of replaced spoil on <br />surface water quality. <br />Regional and site-specific geologic and hydrologic data were collected and analyzed to <br />assess the effects of mining on the potential contamination and diminution of ground and <br />surface waters; the presence of acid-forming or toxic-forming materials and their effect <br />on ground and surface waters; the downstream availability and quality of water which is <br />Impact of Spoil Water Quality on the Cround and Surface Water Quality. <br />used for domestic, agricultural, industrial or any other such purpose; and the potential <br />impacts to the hydrologic balance. The study area includes the Nucla and Nucla East <br />• mining areas and the surrounding region bounded to the south and west by the San Miguel <br />17-30 Revised 04/11/88 <br />