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COLORADO DEPARTMENT OF PURL/C HEALTH AND ENVIRONMENT, Water Quality Contra( Division Rationale -Page 7, Permit No. CO-0036595 Discharge Point Chronic Low Flow, Facility Design Flow, 7WC; (%) • 30E3; (cis) (cfs! 001 0 0.15 100 The IWC for this permit is !00%, which represents a wastewater concentration of 100% effluent to 09~ receiving stream. However, in addition to the i'WC value for determining whether chronic or acute WET testing requirements are applicable, the classification of the receiving stream must be considered. According to the Colorado Water Quality Control Division Biomonitorinr Guidance Document, dated July 1, 1993, where the receiving water is classified aquatic life, class 2 without all of the appropriate aquatic life numeric standards, acute WET testing is required, regardless of dilution. Since the receiving water is classified as Class 2 Aquatic Life use, but does not have all of the appropriate aquatic life numeric standards, the Division has determined that acute WET testing is applicable far this permit (also see following paragraph). 3) Acute WET Limitations: The Division has found that discharges of underground mine drainage and preparation plant water from coal mines at similar sites have txhibited effluent tonicity. On this basis, the Division believes there is reasonable potemial jot the discharge to interfere with attainment of applicable water quality classifications or standards. Because of this condition, the acute toxicity Limit has been incorporated into the permit and becomes effective immediately. Prior to the acute WET limit becoming effective, the perniittee is required to conduct routine monitoring, the results of which are to be reported as an LCD If the LCD 5 100% effluent, the permtttee is required to conduct the automatic compliance schedule as identified in Pare/.A.2. of the permit. 4) Monitarinr Freouencv: The permtttee has performed three years of acute WEI'testing prior to this renewal permit. All tests were passed with minimal toxicity. On this basis, it is appropriate to reduce the • monitoring frequency from the typical quarterly frequency to semiannual monitoring, S) Genera! Information: The permtttee should read the WET testing sections of Part I.A.2. of the permit carefully. The permit outlines the test requirements and the required follow-up actions the permtttee must take to resolve a toxicity incident. The permittee should read, along with the documents listed in Part I.A.2. (a) of the permit, the Colorado Water Quality Control Division Biomonitorine Guidance Document. dated July 1, 1993. 77tis documen! outlines the criteria used by the Division in such areas as granting relief from WET resting, modifying test methods and changing rest species. The permtttee should 6e aware that some of the conditions outlined above may be subject to change ij the facility experiences a change in discharge, as outlined in Part lI.A.1 of the permit. Such changes shall be reported to the Division immediately. 6) Dutfalls 001. 002 and 005: Outfa[l 005 previously consisted of mine drainage and surface runoff. The permtttee eliminated mine drainage from this outfa[l, thus it now consists only of surface runoff, as do Dutfalls 001 and 002. Because these three Dutfalls consist of surface runoff only and discharge during periods of high stream flow, they are nor believed to contribute toxicity. On this basis, WEf testing is nor a requirement far these Dutfalls. However, the Division reserves the right to reopen the permit to include WET testing, should jaciliry conditions change or ijnew information becomes avaifable. 4. Stormwater Evaluation: Stormwater from active and inactive coal mining sites that has been contaminated by contact with overburden, raw material, intermediate products, byproducts, finished products or waste products located at the site is required to be covered by a Colorado Discharge Permit System (CDPS) permit !n order to be discharged to Waters of the State. This coverage may 6e obtained under either a CDPS Industrial Wastewater Discharge Permit or a CDPS Stormwater Discharge Permit. • Division records indicate that Energy Fuels Coa! has not applied for and obtained a Stormwater Discharge Permit for the Southfield Mine. Any discharges that consist only of stormwater that have become contaminated as described above, that do not discharge through the outjal[ for permit number CO-0036595 must be covered by a Stormwater Discharge Permit. Stormwater permitting issues for this jaciliry will be handled separately by the Division's Stormwater Unir, although this permit may be reopened at a later dare to incorporate stormwater provisions, if deemed appropriate.