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C. Sedimentation Ponds <br />There is one sedimentation pond at the mine, located between the portal bench area and the office <br />facilities area, on the south side of the haul road. The pond treats runoff from the portal bench <br />disturbed area, the upper segment of the haul road surface and cut slopes, and a small supply <br />storage area. The pond is somewhat oversized (storage volume adequate to contain the sediment <br />and runoff from multiple 10 year, 24 hour precipitation events below the level of the gated 8" <br />primary discharge pipe). In addition to the primary discharge pipe, the pond has an open channel <br />emergency spillway designed for the 25-year, 24-hour precipitation event. The sedimentation <br />pond is discussed in Section 2.4.4 of the text, and designs are depicted on Figure 2.2-3. <br />The sediment pond was filled in with sediment by a l00 year magnitude storm event in August <br />2001 that had buried and overwhelmed one of the primary upland diversion culverts. In <br />association with excavation of sediment, the inside slopes of the sediment pond were reduced to <br />approximately 2H:1V. The re-constructed pond was properly certified by a professional engineer <br />(see "Impoundment Yearly Inspection" of March 29, 2002). The pond embankment failed in <br />2004, apparently as result of leakage from the buried primary discharge pipe. The embankment <br />was reconstructed and the primary dischazge pipe was replaced. Embankment reconstruction was <br />properly certified (see "Sediment Pond Certification" of December 14, 2004). <br />D. Surface and Ground Water Monitoring <br />GROUND WATER <br />Information provided by the applicant with respect to ground water in the permit area can be found <br />in 4.2.2 through 4.2.4 of Volume I of the permit application. The monitoring plan is described in <br />Section 4.2.4, and monitoring parameters are specified in Table 4.2-15. <br />As discussed in the Probable Hydrologic Consequences (PHC) section of this document, no <br />significant effects to bedrock or alluvial ground water systems are anticipated for this operation. <br />The applicant will conduct monitoring of ground water in a manner approved by the Division to <br />verify the projections of the PHC. The ground water monitoring plan is as follows (4.05.13(1)): <br />1. Quarterly monitoring of alluvial wells GW-1 and GW-3 for static water <br />level, pH, temperature, and specific conductance. <br />2. Water quality sampling of mine water discharges as required by CDPS <br />permit. <br />3. Monitoring of all non-seep inflows into the mine to include source, <br />quantity, duration and quality (pH, electrical conductance, and <br />temperature). <br />4. Monitoring of quantities of water discharged from the mine, consumed <br />in the mine, and imported for use in the mine. <br />Results of the quarterly ground water monitoring are submitted to the Division during the month <br />following the end of that quarter. Monitoring results and evaluation for ground water and surface <br />water are submitted in an annual hydrologic report (AHR). The AHR will detail inflows, <br />dischazges and consumption of water within the mine and shall be structured around the normal <br />"water year" (October 1 through September 30). The annual report will also include baseline <br />15 <br />