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COLORADO DEPARTMENT OF HEdL~, Water Quality Control Division • <br />Rationale -Page 9, Permit No. CO-0029947 <br />A review of available data indicates that {IJ only seven data points art available jor review, (2J escept for <br />one tnlue, the concentration of sulfate appears to be stable and only slightly above du preferred standard, <br />and (3J discharges firm tlu Logan Wash Mine site remain infrequent and art not currerrtly used for irrigation <br />purposes. Therefore, using Best Professional Judgement, such investigations will not be required at this time. <br />However. if sulfate eoncentrarions are determined to 6e increasing rluoughout the hf2 of the permit. the <br />Division resaxs the right to rtqutre the facility to eondttrz the said tnvestigationr and may develop and <br />implemrrt a limitation jor sulfate. Therefore, sulfate monitoring will aoruirwe to be required at the given <br />~n++or+t+8 fn9uc+~!'• <br />No water quality based standards will bt included within the permit at this time. <br />b. Antiderradation -Since the applicable classified mtam segments are use prottactad, and since this penniaing <br />action will not result in an increase in any efflueru aonceruration limit or tffhtent flow limit, tlu receiving <br />inter is not a 'reviewable water', Pursuant to sections 3.1.8(2!(6) and 3.7.8(3J(aJ of The Basic Standards <br />and Merhodo(ories for Surface Water. based upon o finding of no increased water quality impact. <br />a Salinity Rerulations . In compliance with the 'llegulations jor Implementation of the Cobrado Salinity <br />Standards Through rlte CAPS Permit Program', the permittm shall continue monitoring total dissolved solids <br />for three times per month. Samples shall be taken at both effluent discharge points. Salinity requironents <br />are included in Part I, Saxion A.2 of the permit. <br />d. Whole E(fluem Tonicity (NETT Testier <br />For this facility, acute WET testing is requved (See Parts I.A and I.B of the pmnitJ. <br />(IJ ur one of WET' Testier: iht Water Quality Control Division has tstablishad the use of WET testing as <br />a method for identifying and rnntrolling tope discharges from wastevater treatment facilities. WET <br />testing is being utilized as a means to ensure that there arc no discharges of pollutanu 'in amounts, <br />concentrations or combinations which are harmful to the benefuial uses or tctuc to humans, animals, <br />plants, or aquatic life' as required by Section 3.1.11 (1J of the Basic Standards and Methodolories for <br />Surface Waters. <br />(2J Inmeam Waste Concentration (/WCI: Where monitoring or limitations for WET art deemed appropriate <br />by the Division, chronic instream dilution as represented by the IWC Ls cniical to determining if acute or <br />chronic conditions apply. For those discharges the !WC is greater than (>J 9.196, chronic rnnditions <br />apply; and wfiere the IR'C is less than or equal to (G) 9.196, acute conditions apply. The chronic IWC <br />is determined using the following equation: <br />1WC = [Facility Flow (FFJ/Stream C7vonic Low Flow (annual) + FF)f X 10096. <br />The flows and corresponding lWC values for the appropriate discharge point arc included in Table Vl-3 <br />below. <br />Table VI-3 -WET Testing IR'C Values for the Applicable Discharge Points <br />;.'Discharger:.;:.:. ,.:,..::.;:.:'lo ari:Wash:.:.:.i:;: ::':...:::.Aloirthly';Areroge:.:;:'.`,IA'C,':{96) . <br />.'!:j'Pointi!::.':::;.:.::Chroililtiw:.Flaw.:(30E3:;:;:.)::.. ,pMw:(002)':...;:':;:'::'' :::.::.:::::.::. <br />001 and 002 0.0 MGD 0.0037 MGD 100, 0 <br />the JWC value for outfalLs 001 and 002 for this permit is ]00.0%, which represents a wastewater <br />concentration of 100.0% effluent to 0.0°,6 receiving stream (or dilttion weer in WET tests). <br />