2001-12-11_PERMIT FILE - C1980007A (4)

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COLORADO DEPARTMENT OF PURL/C HEALTH AND ENV/RONMENT, Water Quality Control Division Amendment Na. 2 -Rationale. Page 2, Permit No. CO-0038776 • I/!. PURPOSE OF AMENDMENT This amendment addresses two requests from the permittee: 1) By letter dated November 7, 1996, the permittee requested that a new outfall be created to discharge mine water from an underground sump at the Lone Pine portals. Discharge is to Lone Plne Gulch, a tributary to the North Fork ojthe Gunnison River. Details are shown in Table fl-l as new ourfall 013. The permittee expects the efJIuenr quality to be similar to shat from outfall 0/1 nearby, which is also a mine water discharge. 2) ey letter dared December 10, 1996, the permittee requested addition of nvo more ourfal[s. Both will be discharges of surface runoff after settling in sedimentation ponds. Pond details are shown in Table !I-1 as new outfalls 014 and 015. Outfall 014 discharges to Sylvester Gulch and outfal1015 discharges to the North Fork of the Gunnison River. N. RECE/VING STREAM A. Identification, Classification and Standards /dentiflcation: Discharges to Lone Pine Gulch (outfa[l 0!3), Sylvester Gulch (outfa[l 0!4) and the North Fork of the Gunnison River (outfall 015). Lone Pine Gulch and Sylvester Gulch are within segment 6 ojthe North Fork of the Gunnison River Sub-basin of the Gunnison River Basin. The North Fork of the Gunnison River is within segment 2 of the North Fork of the Gunnison River Sub-basin of the Gunnison River Basin. 2. Classification: Segment 2 is classified for the following uses: Recreation, Class 2; Aquatic Lije, Class 1 (cold): Water Supply; Agriculture. Segment 6 is classified jot the jot/owing uses: Use Protected: Recreation. Class 2; Aquatic Life, Clots 2 (warm): Agriculture. • 3. Antidegradation: A review of these three outfalls for compliance with state amidegradation regulations war performed. Outfalls 013 and 014 are exempted because the receiving waters, Lone Pine Gulch and Sylvester Gulch, are within segment 6, which is Use Protected; thus no further review is required. Outfa[l 015 goes to the North Fork of the Gunnison River via a Colorado Depamnent ojTransportation road culvert. This receiving water is within segment 2. This segment is not Use Protected, however, the Division has determined that rso further review is necessary because dilution 6enveen the receiving water and the discharge would 6e greater than 100.•1 during [ow flow conditions. The outfall discharges in response to precipitation and therefore would not be expected to discharge during a low flow period. V. TERMS AND COND/T/ONS OF PERMIT A. Effluent Limitations and Monitoring Requirements In developing suitable effluent limitations, the Division must review al! applicable standards and regulations and apply those which are more stringent. This review includes, but is not limited to: the water quality standard based effluent limitations, federal guidelines and standards (40 CFR Subchapter N) and State Effluent Regulations (10.1.0). Such a review has been done for these new outfalls. Outfall 013: This otttfal! consists solely of mine water. No water quality standards (WQS) exist for the receiving water with the ecceprion of pH thus no WQS limitations except pH apply. Effluent limitations are primarily based on federal effluent guidelines. Because the water quality is believed to be similar to that from existing ourfal[ 0lI due to its source, all effluent limitations will be the same as those for existing mine water outfall 01 !. /t is nor necessary to consider limitations based on the WQS for the North Fork of the Gunnison River due to the large dilution available. The chronic low Jlow for the river is 41 cfs, the design flow for ourfall 013 is 0.072 MGD (0. / l cfs). This results in a dilution ratio of 3727: /. At such high dilution. no limitations would 6e needed. Please refer to the renewal rationale dated February 16, 1995, for a detailed explawtion of how the e}Jluent limitations were determined. Because of the similarity in sources, monitoring frequencies are also the same as for outfall Ol /.