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COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENV/RONMENI ; Water Quality Comro[ Division <br />Amendment No. 5-Rationale. Page 3, Permit No. CO-0000]32 <br />The Elk Creek Mine will extract coal from the D-Seam, which is known to contain groundwater. The initial exploration <br />work has been completed. The permittee will dewarer the D-Seam during construction of the initial mine development. <br />Following completion of construction, underground sumps will be installed that will funcrion ar dewatering locations for <br />the underground mine. The flow from the sumps will be routed to a single outfall, which is the same physical location as <br />the combined discharge from the dewatering wells. This ourfall will be identified as outfall 015. It is shown in amended <br />Figure 1 on page 19 of the permit. <br />Zhe outfall will discharge to Elk Creek, which is a tributary ro the Nonh Fork of the Gunnison River. Classifications <br />and pertinent standards for this receiving water are discussed in section I/1. <br />V. MONITORING DATA <br />Table V-I shows water quality data submined by the permittee. The values indicated for well SC-3 (located above the <br />Sanborn Creek Mine) and outfall Dll (mine water discharge from the Sanborn Creek Mine) are the maximum values of <br />a!! data submined. Zhe value shown for well EC-6 (located in the Elk Creek drainage in the immediate vicinity of the <br />planned Elk Creek Mine) represents the results of a single sample collected in October 1998. The last column indicates <br />the water quality standard for comparison. <br />Table V-l -- Monitoring Results <br />Parameter Well SC-3 OutfaU Oll:. WeII.EC-6 WQ Standard <br />Dissolved Arsenic, mg/P 0.035 N/A <0.002 0.05 (TR) <br />Dissolved Cadmium, mg/P N/A N/A <0.005 0.005 (TR) <br />Dissolved Iron, mg/A 26.8 0.07 <0.01 0.3 <br />Total Iron, mg/P 67.2 1.22 2.64 (!R) N/A^ <br />Dissolved Manganese, mg/P N/A N/A 0.011 0.05 <br />Dissolved Mercury, mg/P N/A N/A <0.0002 0.002 <br />Dissolved Selenium, mg/? N/A N/A <0.002 0.05 (TR) <br />Dissolved Zene, mg/P 0.33 0.07 0.114 5.0 (TR) <br />• There is no WQ Standard for total iron for segment 6, however a federal technology based limita[ion of 3.5 mg/P <br />applies to discharges of coal mine water. <br />7R means the rota! recoverable fraction, as defined in the Basic Standards and Methodologies for Surface Water (31.5). <br />The permittee has stated that water quality to date indicates that the water quality from the new outfall 015 will be <br />similar ro that from outfal1011. <br />VI. TERMS AND CONDITIONS OF PERMIT <br />A. Determination of Effluent Limitations <br />I. Effluent Limitations: In developing suitable efrluenr limitations, the Division must review all applicable <br />standards and regulations and apply those which are more stringent. This review includes, but is not limited to.• <br />the water quality standard based e, fjIuent limitations, federal guidelines and standards (40 CFR Subchapter N) <br />and the Regulations for Effluent Limitations (Regulation No. 62). <br />