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Due to the nature of the discharge and lack of domestic wastewater pollutazmts expected in the effluent, fecal <br />coliform and ammonia aze not evaluated in this water qualiTy assessment. During assessment of the facility, nearby <br />facilities, and receiving stream water quality, no additional pazazneters were identified as pollutants of concern. <br />The upstream background pollutant concentrations (M~~ used in the mass-balance equation will vary based on the <br />regulatory definition of existing ambient water quality. For most pollutants, existing quality is detemmined to be the <br />85'h percentile. For metals in the total recoverable form, existing quality is determined to be the 50`s percentile. <br />For pathogens such as fecal coliform, existing quality is determined to be the geometric mean. <br />CC&V Sediment Pond Discharee: The CC&V sediment pond discharges to Arequa Gulch in Teller Cotmty. The <br />dischazge design flow (Q~ was determined from the flow records provided by CC&V for AG1.5. The average <br />flow was calculated for each month and the highest value (representing the highest average monthly flow) was <br />selected as the discharge design flow. This value is 268.4 gpm or 0.6 cfs, which occurred in July 1998. Average <br />monthly flows of the same magnitude occurred in August 1998 (211 gpm), May 1999 (244 gpm) and August 1999 <br />(216 gpm). Use of the highest expected average monthly flow is consistent with the WQCD practice of establishing <br />the design flow for other types of permitted facilities. <br />Nearbv Sources <br />An assessment of neazby facilities based on EPA's Permit Compliance System (PCS) database found 7 dischargers <br />in the Teller County azea, with one facility discharging to the South Platte watershed. Several facilities aze domestic <br />wastewater treatment plants with no pollutants of concern in common with CC&V discharge. Other facilities were <br />located more than twenty miles from the dischazge and thus were not considered. The nearest dischargers were: <br />City of Victor WWTP (CO-0024201) discharges to Wilson Creek at a point 6 miles upstream from the <br />confluence of Wilson Creek with Fourmile Creek. Victor WWTP does not influence the assimilative <br />capacities available in Cripple Creek. <br />City of Cripple Creek WWTP (CO-0039900), which dischazges to Cripple Creek near its headwaters, <br />which is approximately 6 miles before the confluence with Founnile Creek. <br />Carlton Tunnel (CO-0024562) dischazges to Foummile Creek. <br />Due to the distance between the City of Cripple Creek WWTP and the CC&V, Arequa Gulch discharge the <br />assimilative capacities in Cripple Creek and in Arequa Gulch aze not limited by upstream facilities. Due to the <br />significant dilution of the next downstream receiving streanm, Foumule Creek, and the changes in the chazacteristics <br />of the receiving stream, modeling downstream facilities in conjunction with the CC&V dischazge to Arequa Gulch <br />was not necessary. <br />There aze non-point sources in this azea due to past mining practices. The upstream non-point sources are included <br />in the upstream background concentrations that aze used in this assessment. <br />Chlorine: The mass-balance equation was used to determine the assimilative capacity for chlorine. There are no <br />point sources discharging total residual chlorine within one mile of the Arequa Gulch dischazge. Because chlorine <br />is rapidly oxidized, in-streazn levels of residual chlorine aze detected only for a short distance below a source. <br />Ambient chlorine was therefore assumed to be zero. <br />Using the mass-balance equation provided in the beginning of Section IV, the acute and chronic low flows set out <br />in Section III, the chlorine backgound concentration of zero as discussed above, and the in-stream standards for <br />chlorine shown in Section II, assimilative capacities for chlorine were calculated. The data used and the resulting <br />calculations of the allowable dischazge concentration, M2, are set forth below. <br />Table A-8 <br />Assimilative Ca acities for Chlorine in Cri le Creek <br />Parameter Q~ (cfs x (cfs Q3 (cfs M, M, M3 Notes <br />C12, chronic 0.5 0.6 1.1 0 0.0317 0.011 <br />CIZ, acute 0.4 0.6 1.1 0 0.0202 0.019 <br />Appendix A Page 10 of 13 <br />