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COLORADO DEPARTMENT OF HEALTH, Water Qualiry Control Division Rationale -Page 4, Permit No. CO-0043648 002A This point will be used to monitor and report data associated with the Pregnant Solution Storage Area (PSSA) Leak Collection and Recovery System (LLRSJ, or PSSA-LCRS. The location of this point, shown in figure 3 of the permit, is the leak collection sump, which lies underneath a liner separating it from the pregnant solution recovery risers that are located above it. 003A This point will be used to monitor and report data associated with the Ore Storage Area (OSA) Leak Detection System (LDSJ, or OSA-LDS. While only the single point 003A will be designated for monitoring purposes, there are actually mukiple leak detection and collection poims located around the perimeter of the leach pad. The data that will be reported will summarize the results obtained from the individual leak detection points. 004A This point will be used to monitor the flow of springs which form Arequa Gulch, which are located wuhin the proposed Arequa Gulch Rock Storage Area. The location of monitoring point will be above the point where the springs enter the uttderdrain that will lie underneath the new heap leach pad. OOSA This paint will be used to monitor any other flow from the Arequa Gulch Rock Storage Area, except when direct stormwater runoff is mixed with such flow, and is located at the sump that will collect water fldwittg from the storage area. Samples for this discharge point may not be collected until at [east 24 hrnvs hove passed since the last rain event or since snowmelt in any area tributary to this prnnt has ceased. The water that will be discharged from point OOSA will include meteoric water that has infiltrated into the rock storage area and then seeped underneath the rock pile to the collection sump. During the operation of the teaching facility, the water collected in the sump will be pumped to a diversion channel which flows around the western perimeter of the leach pad and enters Arequa Gulch below a sediment control dam that will be constructed. Monitoring for discharge point ODSA will be done before the flow enters the diversion channel. For future reference, particularly during the renewal of this permit, it should be noted that current mining plans include provisions for discontinuing the pumping operation after the leaching operation hoc sewed and the heap has been detoxified, and instead, routing all flows from the rock storage area to the heap leach pad ttntterdrain . 006A /n addition to the flows that will be monitored at point OOSA, drainage plans for the rock storage area also include provisions for routing stormwater to the collection sump. Then, the combined stormwater/process water would be pumped to the same diversion channel described above. !n order to differentiate monitoring conditions and analytical results, point OOSA will not be used when stormwater is being discharged to the collection sump. Instead, point 006A will be used for such cares. Point OO6A is located at the exit from the diversion channel, prior to entering Arequa Gulch, below the new leaching facilih• and sediment control dam. /n addition w monitoring the combined stormwaterlprocess venter that is pumped from the Arequa Culch Rock Storage Area, it will also be used for any other stormwater that enters the diversion channel from other sources. The locations of points OOSA arut 006A are shorn in figure 3 of the permit. With respect to the conditions under which monitoring may be performed at point 006A, samples may be collected only after rain events or snowmelt conditions which produce visible runoff in the diversion channel have lasted for a period of at (east 5 minutes, and must be collected within 10 minutes after such preclpitntion events hove tensed.