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West E[k Mine <br />fault water inflows were collected in a french drain constructed in the B East Mains <br />• and pumped to the surface and discharged to the North Fork in compliance with the <br />NPDES permit. <br />As previously discussed, there is substantial volume in the sealed sumps to accommodate large <br />new fracture/fault inflows, should they be experienced. <br />Water Quality Implications of Discharge to Lone Pine Gulch <br />MCC currently discharges mine water from the NW Panels sealed sump into Lone Pine Gulch <br />via NPDES discharge outfall #013. The water quality standards are consistent with MCC's <br />other mine water discharge locations. Analyses of water quality samples show that additional <br />treatment (i.e. through a sedimentation pond) is not required prior to discharge, as the NW <br />Panels sealed sump to date (November 1998) provides sufficient TSS reduction to meet <br />NPDES limitations. In fight of the fact that the Fire Mountain Canal diversion occurs <br />upstream of the Lone Pine Gulch confluence with the North Fork, thereby substantially <br />reducing North Fork flows, WWE has analyzed the water quality implications on the North <br />Fork of discharges to Lone Pine Gulch. <br />The first step was to determine what typical flows are in the North Fork downstream of the <br />Fire Mountain Canal Headgate, since this structure has 184.5 cfs of decreed water rights. A <br />- ~ monthly flow analysis was performed for an 18-year period (1975-1992) by subtracting out the <br />• recorded historic ditch diversions from the USGS gage records. While there are additional <br />inflows and diversions that occur between the gage and Lone Pine Gulch, these factors were <br />assumed to be negligible for the level of detail of our analysis. Table 58 shows that with the <br />exception of one month (September 1979) the mean monthly flow downstream of the Fire <br />Mountain Canal diversion was no lower than the winter low flows. Consequently, the water <br />quality analysis shown in Table 54 for winter low flows is applicable to the late irrigation <br />season. Table 54 shows that under winter low flow conditions, the constituent concentrations <br />are increased, but that the resulting downstream concentrations are within natural variability. <br />There are not anticipated to be significant water quality impacts to Lone Pine Gulch as a result <br />of the discharge. This conclusion is based on the following: <br />1. Only a 300-foot reach of Lone Pine Gulch carries the discharged mine water prior <br />to entering the North Fork. <br />2. Lone Pine Gulch is an ephemeral drainage. <br />3. Discharges meet NPDES limits. <br />4. Stream classifications for Lone Pine Gulch are Use Protected, Aquatic Life Warm <br />2, Recreation 2, and Agricultural. A Use Protected classification is the least <br />• stringent that can be applied to a stream by the CWQCD. <br />2.05-204 Revised Jnn. 1995 PR06: Revised,Vov. 1998 TR80; //98 PR08 <br />