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(See Tables E51 -9 through 11 in Exhibit 51). This equation assumed that the existing pool is homogeneous and <br />that there will be instantaneous mixing of the two waters. In actuality, neither condition is met in the short-term, <br />but for the long -term, estimated average discharge quality, it is appropriate. The Fish Creek Borehole is <br />pumping from the bottom of the pool where the water has been standing the longest. Therefore, it will have the <br />worst water quality. The mine inflow will only partially mix with the large pool of water, however, as the pool <br />is reduced in size, mixing will occur more quickly. The results of this deviation from the equation's assumptions <br />are that the early time estimations are low and the late time estimations are high. Because the inflow rate in the <br />first 1.4 years is much less than the outflow rate, and the pool is quite large, the under - estimation of the <br />conductivity will be small. <br />The average water quality discharged from the portal (Site 109), and other situations, was estimated using a <br />simple flow - weighted mass balance equation. The equation is of the form: <br />average — KI * Q0 + (C2 * Q2) + (C. * Qj) / (Q] + Q2 + - -Q.) <br />Where: C, <br />= concentration from source I <br />Q1 <br />= flow from source I <br />C„ <br />= concentration from source n <br />Q, <br />= flow from source n <br />Based upon the above inputs, in Case 1 (Exhibit 51, Table E51 -6) the flow rate from Site 109 will increase from <br />342 (0.76 cfs) to 612 gpm (1.36 cfs) at life -of -mine. The conductivity will decrease from 3,800 umhos /cm to <br />3,100 µmhos /cm. The discharge from Site 115 will average 300 gpm for the first 1.4 years and then 55 gpm for <br />the remainder of the life of mine. In Case 2 the flow rate from Site 109 will peak at approximately 400 gpm <br />(0.89 cfs) at the end of the first 1.4 years and at the end of the life -of -mine. The conductivities in the Case 2 <br />discharges from the portal will be the same as Case 1. In Case 3, water is diverted from the EMD, North Mains <br />and 6 -Right area into the sump at the Fish Creek Borehole. This increases the required average discharge rate, <br />but lowers the conductivity of the discharge due to dilution from the diverted water. <br />Water quality change in the stream reaches downstream of the Sites 115 and 109 will be impacted by the <br />discharges from the mine. The potential impacts have been estimated in Exhibit 51, Table E51 -12 to E51 -21 <br />based upon three different discharge scenarios (Cases 1 to 3) previously discussed. The cases represent different <br />possible ways of splitting the discharge of the inflow between the two discharge points. In Case 1, most of the <br />discharge of the inflows is from Site 109, and in Cases 2 and 3 the discharges are more evenly divided between <br />Sites 109 and 115. <br />The impacts have been compared against applicable standards that may be impacted by the discharges. There <br />are AVF's on Fish Creek below Site 115. A material damage level for flood irrigation of these AVF's has been <br />set at a conductivity of 1,500 umbos /cm, The conductivity was modeled for this reach. It was also modeled for <br />other reaches to estimate overall suitability for irrigation use. In addition, SAR levels were modeled (Exhibit <br />51, Tables E51 -19 to E51 -21). Since the SAR values for Site 109 discharges, as shown on the tables, are less <br />than 10, (the level at which SAR hazard is no longer low) no modeling or reaches only impacted by this site <br />were done. Trout Creek above Fish Creek must meet drinking water related stream standard for sulfate between <br />June and February, and Trout Creek below Fish Creek must meet this standard year- round. No other reaches <br />immediately downstream of the mines must meet this drinking water standard. Sulfate is the only drinking <br />water standard that may be impacted by the mine discharges. Modeling for sulfate was performed. <br />Observed mine water discharges during 1984 exhibited average TDS concentrations of 2,060 mg/L The ionic <br />composition of the discharges was dominated by calcium, magnesium, sulfate, sodium and bicarbonate. Levels <br />of calcium, magnesium, sulfate, and iron are higher than anticipated from the leach experiments. Consequently, <br />sodium adsorption ratios in the mine discharge have been lower than anticipated from the leach experiments (see <br />previous discussion of sodium absorption rations in Section 2.04.6, Geologic Description). SAR's of mine <br />discharges have averaged about 5.3 as compared to values of 21.5, 9.5, and 8.7 for roof, floor and coal leach test <br />results, respectively. While Site 109 has not discharged since 1996, the SAR levels for new discharges from <br />TR 13 -83 2.05 -152 11/03/14 <br />