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West Elk Mine <br />• or criteria. <br />Elevated sodium levels can have negative implications for irrigated soils that are clayey in nature. <br />This is because high sodium can cause such soils to "seal." The sodium adsorption ratio(SAR) <br />is an indicator of the risk that soils may have low permeability. Thus, waters high in sodium and <br />low in calcium and magnesium (the constituents used to calculate SAR) may impose a risk to <br />soils that are used for agriculture. If the SAR is less than 3, there is little to no risk of soil <br />"swell". Water with SAR values ranging from 3 to 6 slightly increase the risk for detrimental <br />impacts to soils, and those with values greater than 6 are cause for concern. WWE calculated the <br />values of sodium, calcium, and magnesium for the combined flow of the North Fork and the fault <br />inflow effluent and found the new SAR to be 3.6 during low flow conditions. It is important to <br />note that any increase in SAR due to mine water discharge will be temporary, due to sodium <br />exchange with calcium and magnesium on sediments and additional downstream inflows. Also, <br />the analysis assumes that the pond discharges consist solely of fault water. Other water reaching <br />the ponds, such as runoff, will have a lower SAR, thereby reducing the SAR of the pond <br />discharges. <br />WWE has reviewed the salinity (TDS) loading analysis in the 2001 Cumulative Hydrologic <br />Impacts Analysis (CHIA) for the North Fork in the context of MCC's 1996 dischazges. In the <br />CHIA, CDMG calculated the cumulative TDS (salinity) loading to the North Fork from coal <br />mines located in the North Fork valley. The assumptions used for MCC's contribution were a <br />dischazge rate of 5,520 gpm (12.3 cfs) and a TDS concentration of 2,500 mg/L. When assessing <br />• calendar year 1996, the total volume discharged from ponds MB-1 and MB-2R was <br />approximately 433 acre feet, which translates to an average continuous discharge rate of <br />approximately 270 gpm. Additionally, the TDS concentration of the B East Mains fault water <br />was typically azound 2,000 mg/L. Consequently, the annual salinity loading to the North Fork <br />from West Elk Mine for 1996 was 3,290 tons, well below the value assumed in the CHIA as <br />shown in Table 57. The analysis for 2002 results in a salt load of 1,922 tons per year, or 6 <br />percent of the values assumed in the CHIA. Furthermore, even considering the "worst case" <br />scenario, the annual salinity load is just 11 percent of the value calculated in the CHIA. <br />WWE has thoroughly evaluated the implications TDS increases and other increases in other <br />constituents within the mine discharge water, and the analyses demonstrate that increases did not <br />cause exceedances of relevant criteria/standazds, nor did they result in any adverse impacts to <br />downstream beneficial uses. Of potential concern is the high sodium level in releases from the <br />sedimentation ponds; yet conservative calculations show that downstream irrigated agricultural <br />lands would not be adversely affected by the increased sodium levels. <br />The sewage collected from the site will be domestic in nature and will consist of soluble B.O.D., <br />volatile suspended solids, and inert solids which will be treated using biological organisms to <br />aerobically stabilize the waste. Since biological treatment will be used, with no chemical treatment <br />required, there should be no secondary by-products which would not be similar to those existing in <br />the North Fork of the Gunnison. <br /> <br />2.06-10 <br />