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COLORADO DEPART7NEM OF PUBLIC HEALTH AND ENV/RONMENT, Water Quality Contra/ Division Rationale -Page 9, Permit No. CO-0027146 b) ~pylicable Federal Effluent Guidelines and Standards; The federal guidelines which apply ro this type of facility are found under 40 CFR 434, titled Coal Minin¢ Point Source EOluent Guidelines. The limitations which apply are: Table V!-5 -Federal Standards (40 CFR 434) Parameter , _ : :Limitations - 30 Day Avg .:: ::'.: Daily Mar. pli, s. u. (minimum -maximum) --6.0 - 9.0-- Total Suspended Solids, mg/Q' 35 70 Totallron, mg/Q^ BAT** 3.5 7.0 Settleable Solids, rnQ/P* N/A 0.5 . * These parameters subject to Burden of Proof Requirements, see nest section '* Best Available Technology -applies to those ponds already constructed Alternate Limitarion Burden of Proof Requirements: /n conformance with 40 CFR 434.63, the permittee has the . burden of proof when requesting relief from !oral suspended solids (fSS), total iron and/or settleable solids limitations, ar appropriate. The iruem of this regulation is to afford relief only when needed due to a volume of water generated by a spetzjic storm evem, it is not intended to be automatically applied to all discharges caused by precipitation, nor to be used to discharge volumes in excess of that generated by the storm event. On this basis, reliejshall be granted only when necessary and shall not be granted when the perntittee has comro! over the discharge, enabling them to meet the primary limitations. Additonally, to qualify, the permiaee must certify that the pond system was properly operated and maintained prior to and during the discharge. The permittee should endeavor to meet the primary limitations whenever possible. A[l manual dewatering of ponds that are equipped with automatic dewatering systems must meet TSS and total iron limitations. If a pond has only manual dewatering capability, relief is available only to the extern required to regain necessary stability and capacity. The Division shall have final authority in determining whether relief is granted. As part of this deterntination, the Division shall evaluate whether the permittee could have controlled the discharge in such a manner that primary limitations could have been met. For rainfall, to waive TSS and total iron limitations, it is necessary to prove that discharge directly resuUed from a specific evem and occurred through automatic dewatering devices within 48 hours after measurable precipitation has stopped. To waive settleable solids limitations, it is necessary to provt that an evem greater than the magnitude of the 10-year, 24-hour event occurred. For srtowmelt, to waive T5S and total iron limitations, it is necessary to prove that discharge directly resulted from snowmelt and occurred through automatic dewatering devices within 48 hours after pond inflow has stopped. To waive settleable solids [imitations, it is necessary to prove that an event greater than the magnitude of the applicable 10-year, 24-hour evem occurred. d) Antidegradatian: Since segment 4 is Use Protected, an amidegradation review is not required for this segment pursuam to section 31.8(2)(b) of The Basic S[ar~+ard< and Methtwl~lo ' c for u~ace Water (S CCR 1002-31). TTtis applies to the outfalls discharging to Coal Creek and unmm~ed tributary to the Colorado River Additionally, in accordance with section 31.8(3)(c)(i), in cases where the ratio of the stream flow to the cjjlttem flow is 100:1 or greater, the discharge is not expected to cause significant degradation and no conditions related to antidegradation will be included in the permit. This is the case jot outfalls discharging to the Colorado River, which is within segmem 2. e) alinip~~gtr ~~o c~ In compliance with section 61.8(2)Q)) of the Qatar Ao Dic ..rge Permit ~yct m R 'o c (S CCR 1002-61), the permittee shall mardtor for total dissolved solids on a quarterly basis. Samples shall be taken at a!1 effluent discharge poims. Salinity requirements are included in Part LB.I.e, of the permit.