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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division Rationale -Page 20. Perini[ No. CO-0043648 c. Discharge Point 002A - Preenant Solution Storaee Area Leak Collection and Recovery Svstem fPS$A-LCRSI. and Discharge Point 003A -Ore Storaee Area Leak Detection Svstem IOSA-LDS) These points will be used to monitor any seepage from the leach heap that is captured prior to entering groundwater or surface streams. While the monitoring of these points will provide an indication ojthe potential for a discharge to surface water, it is not possible to translate water quality standards, federal ejJluent gurdelines, or State effluent regulation limitatiotu into effluent limitations that could be applied to the points. With respect to the parameters that have been selected for monitoring, the leakage pumping rates may be used to identify trends in leakage, and to assist in the operation of the leach facility. The concepts of leakage action codes, and using the depth of solution overthe top liner to calculate theoretical leakage rates, were presented in the perminee's mining permit application (Amendment pbJ that was submitted to the State Division of Minerals and Geology. In addition to the monitoring of leakage rates, another factor that needs to 6e considered in the evaluation of the potential for a point source discharge of pollutants is the concentration of pollutants in any leakage that is collected. The pollutants of concern are cyanide and metals. The metals that were selected for monitoring are those which have been shown to be presently near or exceeding stream standards in Arequa Culch at point AG-l. By monitoring these leakage and pollutant parameters, the permtttee should be able to control the operation of the leach facility to avoid any discharge of pollutants to surface waver. d. Discharge Point 004A - Sorings forming Arequa Gulch within Arequa Gulch Rock Storaee Area, Discharge Point OOSA -Non-Sating Seeoaee from Arequa Gulch Rock Storaee Area (does not include stormwaterl. At Discharge Into Diversion Ditch Surroundine the Vallev Leach Facility Discharge Point 006A -Non-Soring Seeaage from Arequa Gulch Rock Storage Area Mixed With Stormwater. At Discharge From Diversion Ditch to Areaun Gulch Below the Valley Leach Faci[iN Any discharges from point OOSA might entrain sign cant quantities of.cuspended solids. 7herejore, the TSS limit from federal guidelines will be applied. Discharges at point 004A should be low in suspended solids, and at point OObA, discharges would include stormwater runoff, jar which there are no special TSS effluent limitations or guidelines. Therefore, for points 004A and 006A, no TSS limit will 1>e applied. All discharges included in this section -those monitored at points 004A, OOSA or 006A, will flow to Arr¢m Cu(ch, for which [hero arc .ctremn standards for pH, cpnnide and mernLc. Therefore, water qualih~ based limits for these parameters will be applied. Limits for pH will be applied to al( discharges, being set equal to the stream standards. For cyanide, existing WAD cyanide concentrations measured at point AG-l, witicfr is at the same location as point 004A, indicate that the free cyanide stream standard is currently being attained. Therefore, limits equal to the standards will be applied immediately to all discharges listed in this section. For many metals, the existing quality measured at point AG-1 shows instream concentrations are either exceeding or near equalling stream standards. This mm- be due to seepage from historical/}' mitred areas, which nary be an~cially depressing the stream pH, or which nary be carrying n heaty [arid of meta Lc.