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• <br />Table 17-21 <br />Assumptions Associated with the Water Quality Impact <br />Calculations Presented in Tables 17-19, 17-20A and 17-208 <br />1. Background ground water inflows into the streams and the effects on water quality <br />were ignored. <br />2. Surface Water Site SW-N3 was used to measure the quantity and quality of spoil <br />discharge from the' Nucla Mine; Site SW-N1 was considered representative of <br />background. <br />3. The "K" value (40 ft/day) used for calculating spoils flow from Nucla East was <br />determined from a "T" value estimate which was calculated from short term <br />(approximately 30 minutes) pumping drawdowns measured while sampling spoil well <br />CW-N27 for water quality. <br />• 4. All spoil water at Nucla East was assumed to flow into the overburden aquifer and <br />then discharge into Calamity Draw undiluted. <br />5. Cround water inflow into the coal aquifer at Nucla East is considered to be of no <br />significance as the coal aquifer crops in Calamity Draw a considerable distance <br />downstream of the mine. <br />6. The saturated thickness in the Nuc1a East spoils was assumed to approximate premining <br />saturated thicknesses. <br />7, All mine induced flows and chemical loads are assumed to reach the San Miguel <br />unchanged. <br />u <br />8. The mean annual TDS for the San Miguel was assumed to equal the sum of the mean <br />concentrations of Ca, Mg, Na, K, 504, HC03, and C1 and was determined to be 551 mg/1 <br />(based on lorns et al., 1965a). <br />17-72 Revised 04/11/88 <br />