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COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT, Water Quality Comro! Division <br />Amendmem No. 5-Rationale. Page 2, Permit No. CO-0000732 <br />F. CMLRB Permit No.: C-81-022 <br />III. RECEIVING STREAM <br />A. /dentificalion, ClasstftcaAiort, Standards and Anltdegradation <br />1. Identification: This discharge goes to Elk Creek, which is within segmem 6 of the Nonh Fork of the Gunnison <br />River Sub-basin of the Gunnison River Basin. <br />Classification: Segment 6 is designated Use Protected and classified for the following uses: Recreation, Class <br />2; Aquatic Life, Class 2 (warm); Water Supply; Agriculture. <br />3. Numeric Standards: The standards which have been assigned in accordance with the above classifications can <br />be found in the Classifrcarions and Numeric Standards for the Gunnison and Lower Dolores River Basins. <br />Regulation No. 35 (5 CCR 1002-35), as amended December 14, 1998. The Division has made an initial <br />determination, through a review of available monitoring data, that this facility does not discharge pollutants which <br />muss be limited at this time by water quality standards ('WQS) with the exception ofpH, for which the standard is <br />6.5 !0 9.0 s. u., and iron, for which the standard is 0.3 mg/P (as dissolved iron). The permit will require additional <br />shoe-term monitoring for those parameters for which a potemial to exceed applicable WQS may exist. If, upon <br />review of the results of this additional monitoring, it is determined that a reasonable potential ro exceed the <br />WQS exists, the permit will be reopened to add effluent limitations and any other appropriate conditions, subject <br />[o public notice provisions. <br />4. Antidegradation: This segment is not subject to an antidegradation review under provisions of section 31.8(2) of <br />The Basic Standards and Methodolozies for Surface Water. Regulation No. 31 (5 CCR 1002-31) because the <br />segmem is designated as Use Protected. <br />B. Quantity, Acute and Chronic Low Flows <br />The flows which will be used to calculate acute and chronic efJluem limitations are the one day in three year low <br />flow (]E3) and the 30 day in three year low flow (30E3) respectively. Those flows have been determined for Elk <br />Creek by the Water Quality Control Division, and are as follows (all flows in cubic feet per second): <br />Table III-I -Acute and Chronic Low Flows <br />Acute . Chronic <br />Annual 0 0 <br />This creek has been classified as an intermittent stream. <br />IV. PURPOSE OF AMENDMENT, ASSESSMENT OF REQUEST AND FACILITY DESCRIPTION <br />In a letter dared July 22, 1999, the perneinee requested that a new permanent mine water outfall be authorized to <br />address discharges of mine drainage from the new Elk Creek Mine. Supporting information, including several analyses <br />of various groundwater monitoring wells, was previously submitted under a cover letter dated October 22, 1998, when <br />the permiaee requested a temporary permit to discharge from four new groundwater monitoring wells. That <br />authorization was granted under minimal discharge general permit certification numbers COG-600177 and COG- <br />600238. <br />The permiaee is developing a new coal mining area known as the Elk Creek Mine. Although this new mining site is <br />separate from the Sanborn Creek Mine, it is adjacent to the Sanborn Creek Mine and shares surface facilities. For this <br />reason, it is appropriate to cover it under this existing individual CDPS permit. <br />