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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division Rationale -Page 3, Permit No. CO-P043648 Based upon currently available field data and planning documents, and the above considerations, the discharge points listed below have been identified at locations that should allow the detection, assessment and control ojdischarges that might occur during all phases of the project. However, it is recognized that as the project progresses, it may be found to be necessary or advantageous to reropen the permit to add, delete or mods discharge points. OOIA Physically, this is located just below the existing Carlton Mill tailings, at CC&V's monitoring location AG-I. S. After construction of the Phase II leaching facility, it will be at the same location, where a sump will be constructed downstream of the new leach heap toe dam. Far further reference, this poim is also located upstream of the sediment control structure that will be constructed as part of the new leach heap facility. 77tis point will be used to designate the location where monitoring of Arequa Gulch will be performed in order to detect and assess drscharges from any of the following pollutam sources: a) seepage of contaminated water that may be coming from existing Carlton Mill mine tailings. The tailings are located in the drainage basin that forms the west branch of Arequa Gulch and include Tails Ponds No.s I, 2, and 3, and Leach Pad No. 1, which are shown in figure 1 of the permit. b) leaks or spills from the new cyanide leaching facility, or seepage of contaminated water from the soil liner for the facility, which will be constructed from reprocessed Ironclad Mine tailings. cJ the Arequa Gulch Rock Storage Area that will be located upstream of the new leaching facility, which will be used to store rock that is excavated from the Cresson Mine Pit, but which it not of suitable quality to be further processed. This area will also be used for disposnl of the Carlton Mil[ tailings during Phase // of the mining project, and encompasses the location of the existing springs which form Arequa Gulch. dJ nny other existing or future pollutant sources discharging into the Arequa Gulch drainage, which may enter the flow of Arequa Gulch itself above the point where it surfaces as springs. While the point source discharges being addressed by point OOIA ore those described above, it may not be practical to attempt to monitor the isolated discharges themselves, which mm' be dispersed over large areas and may enter groundwater and then resurface as flow in Arequa Gulch. Therefore, monitoring of Arequa Gulch itself will be done at point OOIA, which is downstream of any potential sources of pollutants and below the point where the stream currently surfaces. Additionally, point OOIA will be used whenever the flow going pact it sloes not include any srormwnter. Sampler jot this discharge point may nor be collected until at lead 24 hours hove passed since the lost rain event or since snowmelt in anv area tributan• to thrs point hoc ceased. 00/B This is the some location as point OOIA. But, when the flow going pas[ point (b/A includes stormwater, such as runoff from the face of either the existing tailings dam or proposed [each heap toe dons located just upstream, point t>DIB will be used. Samples may 6e collected only after rain events or snowmelt conditions which produce visible runoff in the diversion channel have lasted for a period of nt least S minutes, and must 6e collected within !0 minutes after such precipitation events hove tensed.