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COLORADO DEPARTMENT OF NEAL7H, Water Quality Comro! Division • Rationale -Page 7, Permit No. CO-0029947 3. Discussion of ElRuent Limitations For Outfalls 001 and 002, r1u basis jot the 7SS, pH, and oil and grease effhtenr limitations, which are listed uw Tablc V/-1, are unchanged from the previous permit. The rationales for thaw limits ass also found within Table V/-1 and additional discussions regarding the limits are contained within the previous permit rationale Although stream standards forfecal coliform bacteria exist for Segment 1.1, sanitary xnstts are nor discharged from the mine site into Logan Wash. 7hoefore, the Division has ddermined that fecal ooliform limitations are not Herded for this permit. The total dissolved solids (IDS) limit for OutfaBs ADl and 002 has rnnsistently been met by tie facility, and with the imermittem discharge for Outfall 002 and the current lack of discharge from OutfaU 001, current salt loading to the receiving stream have been further reduced. The previous permit rationale determined that the Z01~0 mg/1 limitation ins technologically feasible for this operation and its inclusion within the permit xnuld reduce salt loading to acceptable levels. Far these reasons, shoe is no justification for an alteration of the existing limit. 7hoefore, the limit of 2000 mg/1 will ronain to effect jot Outfalls 00I and 002. Additional jurtifuarion far the TUS monitoring it provided in section VLA.3.c., 'Regulations for lmplememation of the Cobrado Salinity Standards Through the CDPS Permit Program ' Altlwugh no limits will be established, monitoring jot COD, total ammonia, nitrate, boron, suljare, fluoride, phenols, arsenic, lead, and copper will remain in effect for Outfalls 001 and 002. However, nau that the analytical method jar lead and copper bout been changed jrom the Total Recoverable method to the Potentially Dissolved method of analysis. This change has been made to provide a Consistent method of comparing the analytical restdts with the established watsr gtutlity standards. Monitoring for these parameters will continue to ensure that wato quality in Logan Wash, Roan C}eek, and the Colorado River arc not impaired by discharges from the Logan Wash mine situ If concuurationt of any one of the listed parameters is detmnined to be causing a violation of wato quality standards, the Division reservrs the right to recalculate and incorporate wato quality based lrmitations in this pcrnet for that parameto using applicable standards. a. Pollutants Limited by Wato Quality Standards -The previous permit used numeric into quality standards from Segment 2 of the Lower Colorado Rivo, receiving water data from Segment /3 of the Lowo Colorado River (Kean Creek), and gQluent data from Outfalls 001 oral 002 to develop and evaluate potential inter quality based lirtits for selected parameters. Once developed, none of the potential litters were incorporated imo the permit as the discharges from Outfall 001 and 002avere not damnined to cause violations of inter quality standards. For this permit rrnewal, factors including the lack of water quality standards for Segment 13 (Logan Wash and Roan Creek), the disrnntinued use of into quality standards for Segment 2 of the Lower Colorado River (see 1II.A.3), and the lack of new receiving stream data, eliminate the need for a detailed eHaluation of inter quality based liners. Additional justification is aNaiJabk from 'end of pipe' comparisons between the DhIIl data for OutfaU 002 (see Table V/-2) and the into quality standards for Segmem 2 of the Lowo Colorado River and with Federal 'Gold Book' Fresh Wato Acute Criteria. These 'end of pipe' comparisons are quite conservative because they arc bawd on zero dilution, w~fureas the Colorado River provides significant dilution. Compliance with Federal Frrsh Water Qeronic Giteria were Hat etnluated due to the ephemera! nature of the receiving stream