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COLORADG DEPARTMENT OF PUBLIC HE.41.TH AND ErWlRONMENT, Water Qualarv Control Division Amendment Nv. 5-Rationale. Page 2, Permit No. CO-0000/32 . F. CiY1LRB Permit rVo.: C-8l-022 ll/. RECF.IVLVG STREA,N A. Identijicatiart. Classification, Standards attd .4 trtidegradalion Identipication: Tl¢is discharge goes to Elk Creek, which is wirhur segment 6 ojrhe North Fork of the Gunnison River Sub-bnsur of the Gunnison River Bnsur. Classification: Segment 6 is designated Use Protected and clnssi(red for the following uses: Recreation, Class 2; Aquatic Life, Class 2 (warm); lVnter Supply; Agriculture. 3. Numeric Standards: The standards which have been nssrgned in accordance with the above classificnrions can be found in the Classifications and Numeric Standards for dre Gunnison and Lower Delores River Basins. Regulation No. 35 (5 CCR l002-35), as amended December 1 d, 1998. The Division has made mr mrua! determination, through a revew of available monitoring data, that this facility does eat discharge pollutants whrch must be limited at this rime by water qualrry standards (WQS) with dre excepnon of pH. for whrch the standard rs 6.5 ro 9.0 s. u., and iron, for which the standard is 0.3 mg/P (as dissolved iron). The permit will require additional short-term monitoring for those parameters for which a potential !o exceed applicable WQS may errs[. !f, upon review of the results of this additional monitoring, it is determined that a reasonable potential to ereeed the WQS exists, the permit will be reopened to add effluent limitations and any other appropriate conditions, subject to public notice provisions. 4. Antide2radarion: This segment is not sttbjec[ to an antidegradatiorr review under provisions of section 31.8(2) of • The Basic Standards and Methodoloeies (or Surface Water, Regulation No. 31 {5 CCR 1002-31) because the segment is designated as Use Protected. B. Quantity, Acute and Chronic Low Flows The !rows which will be used to calculate acute and chronic effluent limitations are the one day in three year low Jlow (1 E3) and the 30 day in three year low flow (30E3) respectively. Those flows have been determined for Elk Creek by the Water Quality Carrtrol Division, and are as follows (all flows in cubic fzet per secondl: Table I!I-1 -- Acute and Chronic Low Flows Acute Chronic Annual 0 This creek has been classified as an intermittent stream. /V. PURPOSE OF AMENDMENT, ASSESShfENT OF REQUEST AND FACILITY DESCRIPTION In a fetter dated July 22, 1999, the permittee requested that a trees permanent mini water outfaff 6e authorized to address discharges of mine drainage from the new Elk Creek Mine. Supporting information, including several ntralyses of various groundwater monimnng wells, was previously submitted render a cover letter dated October 22, 1998, when dre permittee requested a temporary permit to discharge front jour new groundwater nronitonng wells. That nuthorizatioa was granted under minimal discharge genera! permit certification numbers COG-600177 m7d COG- 600238. Tire permittee is developrng n new coal minrng urea known as the Elk Creek Mine. Although this new mining rite is separa[e from the Sanborn Creek ,Yline, it rs adjacent m the Smrbonr Creek Mine and shares surface facilities. For this reason, it rs appropriate m cover it under this exrsting individun[ CDPS permu.