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Wesl EIk Mine (Portal No. 5) mine portals. Additional data for mine discharges is contained in the MCC • Quarterly Hydrology Reports (1982 to 1987) and the Annual Hydrology Reports (1982 to present). Data and test results indicate these mine water discharges have not adversely impacted the North Fork. The quality of mine water discharges from the B-Seam in the current permit area and in the Box Canyon Permit revision area, and from the B and E-Seams in the Apache Rocks permit revision area, are expected to be good enough to meet NPDES discharge standards. Table 53 shows well water quality for wells in the B-Seam. With the exception of pH for wells SOM C- 72-H (likely from grout contamination) and SOM 127-H, quality parameters appear to be such that B-Seam mine water will be suitable for treatment and discharge under current NPDES/CDPS permit requirements. This high pH situation, if encountered in mine water discharge, can be corrected by dilution with surface runoff in the sediment pond or by chemically adjusting the pond pH prior to discharge. The following text evaluates the water quality implications of discharges from NW, NE, and Box Canyon Panels sealed sumps and the fault inflows to the North Fork. Rather than analyzing the individual water quality impacts, these discharges have been aggregated to determine water quality changes. Individual discharges which were aggregated include: (1) North Fork diversions and return flows; (2) Pond MB-1 and MB-2R releases; (3) direct discharges to the North Fork from the fault inflows; (4) mine water discharges to Lone Pine Gulch and to Sylvester Gulch out of the NW Panels sealed sump and NE Panels sealed sump, • respectively; and (5) minor groundwater seepage from the NW Panels sealed sump. The principal water quality implications associated with sump construction and fault inflows include: 1. The total volume of discharges to the North Fork during 1996 was considerably larger than in previous years, due to the fault water. Although constituent concentrations of the discharges during 1996 were not significantly different from concentrations in past years, the total constituent loads to the North Fork were higher by virtue of the increased outflow volume. While the constituent loads were higher, the impact to the North Fork was insignificant, primarily due to the relatively small contribution of the mine discharges to the total flow of the North Fork. During succeeding years; however, total constituent loads to the North Fork are expected to decrease for a variety of reasons, including: availability of underground sumps; the new mine water pumping facility; and a leveling off of the fault inflows to lower, steady rates. 2. MCC experienced multiple NPDES permit exceedances associated with fault inflows in 1996 due to: (1) the heary hydraulic load which started in March 1996 and continued through the year, and (2) a different kind of colloid which was very difficult to treat. MCC has taken many steps to minimize the probability of future exceedances such as: separating inflows within the mine; large capacity sealed sump utilization; optimizing surface water • 2. ~5-197 Revised Jun. 1995 PR06: Revised Nov. 1998 rR80; 1 /98 PR08