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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division Rationale, Amendmem No. 4. Page 2. Pcrnut No. CO-0042161 pH = 6.5 - 9.0 s. u. TRC = 0.003 mg/l FC = 200/100 ml Unionized Ammonia = 0.02 mg/[ (chronic) However, due to the distance between the discharge point and the receiving water, the 7RC, FC and ammonia standards are not directly applied at the new outfall 002. See discussion in Section /V. B. /V. PURPOSE OF AMENDMENT In a letter dated November 17, 1992, the permittee rcquested a permit amendmem to add another discharge point, number 002, to serve as the discharge point from a new domestic wastewater treatment facility (WWI"FJ being constructed to replace existing septic tank and leach field systems. The WWTF will serve the regional office complex as well as Cyprus Yampa and 7lventymile facilities, including a 6atlJwuse. The permittee was granted site approval 84078 on January 28, /993, jot this WW1F Terms and conditions in this permit amendment correlatc with the site approval. A. Trealrnent and Discharge Point: The wastewater treatment facility will consist affour lined aerated lagoons with chlorine disinfection. The drscharge wAl 6e piped to the edge of a previously backfilled area where it will be mixed with spoils spring water at the Emerald Spring site. The aufharized discharge point is defined as the point of discharge at the eflluent weir in the control building, prior to emering the spoiir spring. B. EJJlttent Limitations: The site approval species e~luem limitations for BODJ, 7SS and fecal califarm, as well as specking hydraulic and organic capacities of 0.015 MGD and 31.2 !b. BODY/day, respectively. These capacities are applied to the influera to the WWTF and are shown in Part /.A.2.aJ of the permit. Monitoring ojpoim 3001 will 6e required ro determine whether compliance with these capacities is being maintained. The site approval does not sped rota! residual chlorine limitations because the discharge does not go directly to a surface water of the state. Therefore, rw 7RC limitations are appropriate. This will allow maximum disinfection necessary to achieve the lowest possible effluem fecal coliform count. For the same reason that 7RC limitations do not apply, no total anvnania limitations are directly applied. However, this discharge may influence the concentrations ojtatal arrunonia discharged at autfall 001. The combined spoiir spring water is used for the underground dust suppression system. A portion ojthis water is taken up with the mined coal. The majority drains to a sump that discharge to the Firh Creek Borehole ponds and is subsequently discharged through existing autfall 001. The combined spoils spring water is used for the underground dust suppression system A ponian of this water is taken up with the mined coal. The majority drains to a sump that discharges to the Fish Creek Borehole ponds oral is subsequently discharged through existing outfall OOI.For thin reason, [he permittee will need to monitor at outjall 001 for total ammonia. No limitations are being imposed at this time because it is assumed that the effluent concentrations will be extremely low. However, ijconcemrations indicate a potemial or actual impact on Fish Creek, the permit may 6c reopencd to add total ammonia limitations and/or other appropriate conditions. Table IV-1 specifies the applicable effluent limitations for autfall 002 and the rationale for each.