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reaches to estimate overall suitability for irrigation use. In addition, SAR levels were modeled (Exhibit 49, Tables <br />E49-19 to E49-2]). Since the SAR values for Site 109 discharges, as shown on [he tables, are less than 10, (the <br />.level at which SAR hazard is no longer low) no modeling or reaches only impacted by this site were done. Trout <br />Creek above Fish <br />Creek must meet drinking water related stream standard for sulfate between June and February, and Trout Creek <br />below Fish Creek must meet this standard year-round. No other reaches immediately downstream of the mines <br />must meet this drinking water standard. Sulfate is the only drinking water standard that may be impacted by the <br />mine discharges. Modeling for sulfate was performed. <br />Observed mine water discharges during 1984 exhibited average TDS concentrations of 2060 mg/L The ionic <br />composition of the discharges was dominated by calcium, magnesium, sulfate, sodium and bicarbonate. Levels of <br />calcium, magnesium, sulfate, and iron aze higher than anticipated from the ]each experiments. Consequently, <br />sodium adsorption ratios in the mine discharge have been lower than anticipated from the ]each 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 Site <br />] 09 are estimated to be a maximum of 9.8 using the analysis from 6 Right as a worst case (Exhibit 49, Table E49- <br />1). The TDS concentration, using the analyses from 6 Right would be approximately 4000 mg/L and would be <br />dominated by sodium and sulfate. <br />As discussed in Rule 2.04.7, Ground Water Information, the most plausible explanation of increased calcium, <br />magnesium, sulfate, iron and TDS in mine discharge as compared to baseline formation water or leach test results <br />for coal, roof or floor materials, is that formation water in the vicinity of the portals has been impacted by water <br />emanating from upgradient mine spoils. Observations of mine inflows near the portals along with elevated TDS, <br />sulfate, calcium, magnesium and iron observed in the Wadge overburden well TW-1 down gradient of surface mine <br />spoils support this conclusion. The salinity of mine inflow water described in the May, 1985 Mine Inflow Survey, <br />• shows a conductivity plume downgradient from the surface mine spoils. As mining operations progress further <br />from this plume we can expect to see reductions in TDS levels and changes in ionic composition with dilution of <br />spoil water inflows. However, these decreases may be offset somewhat by the use of water from Sites 1 114 and <br />109 in the underground system. <br />As of June 1999, some inflows to the underground mine have shown higher conductivities. The large inflow to the <br />EMD at 6 Right has a conductivity of 4660 µmhos/cm (Exhibit 49, Table E49-1). Pumping of the Fish Creek <br />Borehole ceased in July 1996. At that time, the conductivity was approximately 4420 µmhos/cm. When pumping <br />restarted in August 1999, the average conductivity had increased to 7300 µmbos/cm (Exhibit 49, Table E49-5). <br />However, inflows to the EMD (excluding 6 Right) measured during the 1997 and 1998 Mine Inflow Surveys <br />averaged 2800 to 2900 µmhos/cm. In addition, water from Pond A is fhe source of make-up water for the <br />underground mine equipment. It has a conductivity of 2900 µmhos/cm. <br />The ability to discharge from the pit south of Pond D directly into Foidel Creek will provide greater control over <br />the water quality in the creek. The current system, site 109 into Pond D via the pit, has a lag time associated with <br />the discharge. After both the pit and pond are full it takes time for the them to dewater after discharge from site <br />109 is stopped. Once the direct line to Foidel Creek is established the discharge can be stopped instantaneously, <br />thus ensuring the discharge minimizes downstream impacts. The impacts from this discharge has been discussed <br />previously, as the water quality should not change due to this alternate system. <br />U <br />TR O1-39 2.05-153 8/10/01 <br />