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into the sump at the Fish Creek Borehole. This increases the required average dischazge rate, but lowers the
<br />conductivity of the dischazge 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 dischazges
<br />from the mine. The potential impacts have been estimated in Exhibit 49, Table E49-12 to E49-21 based upon three
<br />different discharge scenarios (Cases 1 to 3) previously discussed. The cases represent different possible ways of
<br />splitting the discharge of the inflow between the two discharge points. In Case 1, most of the discharge of the
<br />inflows is from Site 109, and in Cases 2 and 3 the discharges are more evenly divided between Sites 109 and 115.
<br />The impacts have been compared against applicable standards that may be impacted by the discharges. There are
<br />AVF's on Fish Creek below Site 115. A material damage level for flood irrigation of these AVF's has been set at a
<br />conductivity of 1,500 umhos/cm. The conductivity was modeled for this reach. It was also modeled for other
<br />reaches to estimate overall suitability for irrigation use. In addition, SAR levels were modeled (Exhibit 49, Tables
<br />E49-19 to E49-21). Since the SAR values for Site 109 dischazges, as shown on the tables, aze 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 Creek must meet drinking water related stream standard for sulfate between June and February,
<br />and Trout Creek below Fish Creek must meet this standard yeaz-round. No other reaches immediately downstream
<br />of the mines must meet this drinking water standazd. Sulfate is the only drinking water standazd that may be
<br />impacted by the mine discharges. Modeling for sulfate was performed.
<br />Observed mine water dischazges 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 bicazbonate. Levels of
<br />calcium, magnesium, sulfate, and iron are higher than anticipated from the leach experiments. Consequently,
<br />sodium adsorption ratios in the mine dischazge 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 dischazges from Site
<br />109 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 4,000 mg/L and would be
<br />dominated by sodium and sulfate.
<br />As discussed in Rule 2.04.7, Ground Water htfom~ation, 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 neaz 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 nilning 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 114 and l09
<br />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 4,660 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 7,300 µmhos/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 2,800 to 2,900 µmhos/cm. In addition, water from Pond A is the source of make-up water for the
<br />underground mine equipment. It has a conductivity of 2,900 µmttos/cm.
<br />TR07-60 2.05-153 05/01/07
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