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'ationale -Page 6, Permit No. 00.0034141 <br />b) Water OualiN Based E111uent Limitations: The Water Quality Control Division has performed an assessment of potential <br />water quality standards based permit limitations and made a preliminary determination of applicable limitations. This <br />assessment was for this facility can be found in Appendu A, which shows the assimilative capacities jot metals and othe <br />parameters dete»nined ro be of concern to this permit. These assimilative capacites are potential effluent 7imitatio <br />Because thisfaciliry has not increased its loadfrom theprevious permit, ontidegradation requirements donor apply. Ta <br />V-1, Y-2, and Y-3 in this rationnle dtsylay effluent limitations based on this water quality assessment that the Division h <br />determined need to be imposed: <br />,cJ ~licoble Federal Ellluent Guidelines and Standards: Thefederal guidelines which apply to ibis type offaciliry arefound <br />under 40 CFR 434, titled Coal Mining Point Source E~]luent Guidelines. The limitations, which apply, are: <br />Table Y-4 -- Federal Standards (40 CFR <br />pH, s.u. (minimum -'maximum) -6.0 - 9.0- <br />Settleable Solids, mUl • N/A 0.5 " <br />' These pn~ameJers are subject Jo Burden ofP~oof Requrrements, see neu section <br />d) Alternate Limitation Burden ofProofReauirements: In conformance with 40 CFR 434.63, the.permittee.has the burden <br />ofproofwhen requesting relieffrom settleable solids limitations. Reliefshall be granted only when necessary andshaA <br />not be granted when the permittee has control over the discharge. The permittee should endeavor to meet, the primary <br />limitations wheneverpossible. This relief is available only for surface runoffoutfalls (004, 007,:009, 011= 021). <br />r. <br />For rainfall, to waive TSS and total iron limitations, it is necessary to prove that discharge occurred within 48 hours after <br />measurable precipitation has stopped. In addition, to waive settleable solids limitations, it is necessory to prove that <br />dtscharge occurred within 48 hours after precipitation greater than the 10-year, 14-hour event has stopped. <br />For snowmejt, to waive TSS and total iron limitations, it is necessary to prove that discharge occurred within 48 hours after <br />pond inflow has stopped. In addition, to waive serrleablesolids /imitations, it is necessary to prove that discharge occu <br />within 48 hours after pond inflow volume greater than the 10-year, 24-hour event has stopped. <br />The Division shall determine the adequacy ofproof. As part of this determination, the Division shall evaltiare whet e. <br />permitree could have controlled the discharge in such a manner thatprimary /imitarions could have been met. All manual <br />pond dewatering must meet TSS and total iron limitations or settleable solids limitations. : . <br />~~ e) Salinity Regulations: In conformance with the Colorado River Salinity Standards and section 61.8(1)(1) of the Colorado <br />Discharge Permit Svstem Regulations. the permittee shall monitor for total dissolved solids or conductivity on a quarterly <br />basis. Samples shall be taken at e,~luent discharge points to state waters. Salinity requirements are included in Part.1.B.2. of <br />thepermit. <br />n Whole Eflluenr Toxicity Testing: For aurfalls 003, 011, and 024, chronic WET testing is required. <br />1) Puroose of WET Testing: The Water Quality Control Division has established the use of WET testing as a methodjor <br />identifying and confrolling toxic discharges from wastewater treatment facilities. WET testing is being utilized as a <br />means to ensure that there are no discharges ofpollutanu "in amounts, concentrations or combinations which are <br />harmful io the beneficial uses or toxic to humans, animals, plants, or aquatic Life" as required 6y Section 31.11 of the <br />Basic Standards and Methodologies for Surface Waters. <br />1) InsbeamWa.cteConcentration(IWC): Where monitoringorlimitafionsforWETaredeemedappropriatebytheDivision, <br />~• chronic insiream dilution as represented by the chronic TWC is critical in determining whether acute or chronic <br />conditions shall apply..For those discharges where the chronic IWC is greater than 9.1 %, chronic conditions apply, <br />where the IWC is less than or equal to 9.I % acute conditions apply. The chronic IWC is determined using thefollowing <br />equation: <br />The flows and corresponding IWCfor the appropriate discharge point are: <br />IWC = (Facility Flow (FF)/(Stream Chronic Low Flow (annual) + FF)J X 10090 <br />