Site 109 are estimated to be a maximum of 9.8 using the analysis from 6 -Right as a worst case (Exhibit 51,
<br /> Table E51 -1). The TDS concentration, using the analyses from 6 -Right would be approximately 4,000 mg/L
<br /> and would be 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
<br /> results for coal, roof or floor materials, is that formation water in the vicinity of the portals has been impacted by
<br /> water emanating from upgradient mine spoils. Observations of mine inflows near the portals along with
<br /> elevated TDS, sulfate, calcium, magnesium and iron observed in the Wadge overburden well TW -1 down
<br /> gradient of surface mine spoils support this conclusion. The salinity of mine inflow water described in the May,
<br /> 1985 Mine Inflow Survey, shows a conductivity plume downgradient from the surface mine spoils. As mining
<br /> operations progress further from this plume we can expect to see reductions in TDS levels and changes in ionic
<br /> composition with dilution of spoil water inflows. However, these decreases may be offset somewhat by the use
<br /> of water from Sites 114 and 109 in the underground system.
<br /> As of June 1999, some inflows to the underground mine have shown higher conductivities. The large inflow to
<br /> the EMD at 6 Right has a conductivity of 4,660 µmhos /cm (Exhibit 51, Table E51 -1). Pumping of the Fish
<br /> Creek Borehole ceased in July 1996. At that time, the conductivity was approximately 4,420 µmhos /cm. When
<br /> pumping restarted in August 1999, the average conductivity had increased to 7,300 µmhos /cm (Exhibit 51,
<br /> Table E51 -5). However, inflows to the EMD (excluding 6- Right) measured during the 1997 and 1998 Mine
<br /> Inflow Surveys averaged 2,800 to 2,900 µmhos /cm. In addition, water from Pond A is the source of make -up
<br /> water for the underground mine equipment. It has a conductivity of 2,900 µmhos /cm. The ability to discharge
<br /> from the pit south of Pond D directly into Foidel Creek will provide greater control over the water quality in the
<br /> creek. The current system, Site 109 into Pond D via the pit, has a lag time associated with the discharge. After
<br /> both the pit and pond are full, it takes time for them to dewater after discharge from Site 109 is stopped. Once
<br /> the direct line to Foidel Creek is established, the discharge can be stopped instantaneously, thus assuring the
<br /> • discharge minimizes downstream impacts. The impacts from this discharge has been discussed previously, as
<br /> the water quality should not change due to this alternate system.
<br /> The 6RT water and the Fish Creek Dewatering Well discharge water are strongly sodium sulfate waters. The
<br /> Pond A water is calcium- magnesium sulfate water, with a conductivity averaging 2,900 µmhos /cm. Use of the
<br /> Pond A water helps balance the salt loading levels and sulfate of the ground water inflows to the mine, and
<br /> reduces SAR.
<br /> The potential impact of past mine discharge to Foidel Creek is addressed in WATBALP, a water quantity and
<br /> quality model of the Trout Creek drainage (Exhibit 32, Quantity and Quality Modeling Analyses of Surface -
<br /> Water Resources of the Trout Creek Basin). The modeling analysis was based on mine discharge projections in
<br /> Table D of Exhibit 33, Mine Water Control Plan. The comparison on Figure 4 -g, Ground Water Quality Data,
<br /> of this sample with average mine discharge characteristics in 1984, shows that the sample is more representative
<br /> of spoil discharges than actual mine discharges and thus constitutes a worse case estimate of mine discharge
<br /> quality. The assumed water quality characteristics of mine discharge were based upon a single sample that was
<br /> assumed to be representative of mine outflows (Exhibit 33, Mine Water Control Plan). Mine inflow projections
<br /> have changed since the original modeling. The streamflow numbers and baseline water quality numbers from
<br /> the model combined with new (April 1999) projected mine inflow and discharge projections (Exhibit 51, Tables
<br /> E51 -12 to E51 -14) were used to project future impacts on the local drainages.
<br /> Similar calculations were performed to predict the sodium adsorption ratio conditions that might occur in Fish
<br /> Creek and Trout Creek because of discharge of mine inflows to Fish and Foidel Creeks. This was performed
<br /> primarily to evaluate possible effects on the use of Fish and Trout Creek waters for irrigation purposes. Average
<br /> values for the respective components were used.
<br /> • Calculations were performed for Fish Creek below the proposed Fish Creek dewatering discharge point and for
<br /> Trout Creek at two points (equivalents of Sites 69 and 1005) below the confluences with Middle Creek and Fish
<br /> Creeks. The results of these analyses are shown in Exhibit 51, E51 -19 to E51 -21, Table 63. The results indicate
<br /> PR09 -08 2.05 -153 04/27/09
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