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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division Rationale - Page 11. Permit No. CO-0027154 VI. TERMS AND CONDITIONS OF PERMIT A. Effluent Limitations (continued) Footnotes for Table VI-2: * See discussion regarding alternate limitation burden of proof ** The previous permit did not limit TDS or electrical conductivity. It is unclear why it was not limited. The discharge goes to the same receiving water as the other two continuous outfalls. Thus, it is appropriate to impose a TDS-based conductivity limitation for this outfall. e/ 30-Day Average/Daily Maximum 30-Day Average J Daily Maximum J Minimum-Maximum J There shall be no acute toxicity in the effluent from this discharge point. The acute toxicity limitation is exceeded if 1) a statistically significant difference in mortality (at the 95x confidence level) is observed for either species between the control and any dilution less that or equal to the identified IWC or 2) a species mortality in any dilution of effluent (including 100X effluent) exceeds 50X. Table VI-3 -- Effluent Limitations For Outfall 007 Parameter Flow, MGD TSS, mg/1 Total Recoverable Iron, mg/1 Total Recoverable Manganese, mg/1 Potentially Dissolved Copper, mg/1 Potentially Dissolved Silver, mg/1 pH, s.u. Oil and Grease, mg/1 Electrical Conductivity, umho/cm Whole Effluent Toxicity, Acute through March 31, 1996 beginning April 1, 1996 Whole Effluent Toxicity, Chronic through June 30, 1996 Limitation Rationale Report J Design Capacity 3s/70* ~ Federal BPT 1.0 J Water Quality Standards Report J Water Quality Standards 0.073/0.130 ~ Water Quality Standards Report Water Quality Standards 6.s - 9.0 J Water Quality Standards 10 J State Effluent Regulations s,150 J Beneficial Use Report IWo-loox/sox e/ Report WET Regulations WET Regulations WET Regulations * See discussion regarding alternate limitation burden of proof J 30-Day Average/Daily Maximum J 30-Day Average Daily Maximum d/ Minimum-Maximum . g/ There shall be no acute toxicity in the effluent from this discharge point. The acute toxicity limitation is exceeded if 1) a statistically significant difference in mortality (at the 9sX confidence level) Ss observed for either species between the control and any dilution less that or equal to the identified IWC or 2) a species mortality Sn any dilution of effluent (including 100x effluent) exceeds sOX.