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Page 2: <br />COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division <br />Rationale -Page 23 Permit No. CO-0045675 <br />The Oows and corresponding IWC for the appropriate discharge point are: <br />! Discharge Point Chronic Low Flow, Facility Design IWC, (%) <br />' 30E$ cfs Flow, <br />Cfs 1nom1 <br />001 a 1.8 0.891 (400) 33.1 <br />001 b 1.8 0.557 (250) 23.8 <br />e) Whole Effluent Toxicifv fWET) Testing (Cont.) <br />The IWC for ouffa11001c at the facility discharge Bow rate of 110 gpm is 12.0 %, which represents a <br />wastewater concentre8on o(12% effluent to 88% receiving stream. Thus, chronic WET testng is <br />applicable for ouNalls OOfa, OO1b, antl001c. <br />~ Chronic WET Monitoring: Since [he facility's wastewater source data and treated discharge data have <br />very low concentre8ons of pollutants, and one WET testing (Apol 2000) has been performed for both <br />species which resulted in passing tests for lethality end growth, the Division has determined at this <br />time that there is no reasonable potential for toxicity to occur in this discharge, thus no chronic lethality <br />limitation has been established for this permit. In accordance with Section 61.8 (2)(b)(i) o/the <br />Colorado Discharge Permit System Regulations, the permittne will be required to conduct routine <br />monitoring for chronic toxicity using Certodaphnia sp. and fathead minnows. The results of the testing <br />are to be reported on Division approved forms. The pennittee will be required to conduct two types o/ <br />statistical dertva8ons on the data, one looking (or any statisbcally sign cant difference in toxicity <br />between the control and the effluent concentrations and the second identifying the ICrx should one <br />exist. Both sets o(calcula8ons will look at the full range of toxicity (lethality, growth and reproduction). <br />If a level of chronic toxicity occurs, such that there is a statistically sign cant difference in the lethality <br />(at the 95 % con5dence level) between the control and any effluent concentration less than or equal to <br />the Instream Waste Concentre8on (IWC) ~ if the IC:s < the IWC, the permittne will be required to <br />follow the automatic compliance schedule idenfi(ed in Part I.A.4.(c) o(the permit, if the observed <br />toxicity is due [o organism lethality. If the toxicity is due to dAferences in the growth of the fathead <br />minnows or the reproduction o/the Ceriodaphnia, no immediate action on the part of the permittne will <br />be required. However, this incident, along with other WET data, will be evaluated by the Division and <br />may form the basis for reopening the permit and including additional WET limits or other requirements. <br />4) General In/ormation: The permiftee should read the WET testing sections of Part I.A. and I.B. of the <br />permit carefully. The permit ou0ines the test requirements and the required follow-up actions the <br />permittne must take to resolve a toxicity incident. The permittne should read, along with the <br />documents listed in Part I.A.4 of the permit, the Colorado Water Quality Control Division Biomonitorina <br />Guidance Document dated July 1, 1993. This document ouuines the criteria used by the Division in <br />such areas as granting relief /rom WET testing, modifying test methods and changing test species. <br />The permitttne should be aware that some of the cond&'ons outlined above maybe subject to change if <br />the facility experiences a change in discharge, as ou8ined in Part II.A.1 of the permit. Such changes <br />shall be reported to the Division immediately. <br />5. Stormwater Evaluation: Stormwater discharge permits are required for active and inactive metal mining <br />facilities as covered under Standard Industrial Classfica8on (SIC) Code f0. This SIC Code includes mining, <br />developing mines, or explortng for metallic minerals (ores). <br />Division recoMs intlicate that Battle Mountain Resources, Inc. applied for and obtained coverage under a <br />general permit (or s[ormwater discharges associated with metal mining for the San Luis Project. The COPS <br />cert~cation number is COR-040050. Sformwater permitting issues (or this facility will be handled separately <br />by the Division's Stormwater Unif, although this permit may be reopened at a later date to incorporate <br />stormwater provisions, if deemed appropriate. <br />8. Economic Reasonableness Evaluation: SecBon 258-503(8) of the revised (June 1985) Colorado Water <br />Oual' Control Act required the Division to 'determine whether or not any or all of the water quality standard <br />based effluent limitations are reasonably related to the economic, environmental, public health and energy <br />impacts to the public and affected persons, and are in furtherance o/the policies set forth in sections 258-192 <br />and 258-104.' <br />The Colorado Discharge Permit System Regulations, Regulation No. 61, /urther define this requirement under <br />81.1 f and stale: 'Where economic, environmental, public health and energy impacts to the public and <br />affected persons have been considered in the Gassifica8ons and standards setting process, permits written to <br />