2009-07-01_REPORT - C1980007 (6)

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West Elk Mine 2008 Annual Hydrology Report 46 was adversely affected in the fourth quarter of 2007 or the first or second quarter of WY 2008 (MCC, 2009). In a letter dated October 30, 2008 MCC requested a permit modification including (in part): removal of the requirement to monitor and report potentially dissolved iron (Fe, PD) for Outfall 017. The rationale for Amendment 2 to CDPS Permit Number CO-0038776 is as follows and will be effective in WY 2009: "The Division concurs with the permittee's request to remove effluent limitations and reporting and monitoring requirements for potentially dissolved iron (Fe, PD) at Outfall 017, as there is no longer Reasonable Potential (RP) for this pollutant to cause or contribute to exceedances of applicable water quality criteria for dissolved iron. In a June 2006 rulemaking, Section 6 of the North Fork of the Gunnison River was divided into Segments 6a and 6b. Segment 6a, which is now the receiving water for discharges from Outfall 017, includes Sylvester Gulch and West Sylvester Gulch, both intermittent tributaries to the North Fork of the Gunnison River. This segment is not classified as a water supply, and therefore, there is no applicable water quality standard for dissolved iron applicable to Segment 6a. Segment 6b includes the main stem of the North Fork of the Gunnison River to which Sylvester Gulch is tributary and is classified as a water supply with an applicable 30-day average water quality standard of 300 ug/G dissolved iron. Using effluent data from July 2006 to July 2008 provided by the permittee, the Division performed a Reasonable Potential Analysis (RPA) to determine if discharges at Outfall 017 show a reasonable potential to cause or contribute to exceedances of the water quality standard for dissolved iron in Segment 6b. A critical low flow determination was completed using the last ten years of flow data from USGS Gauging Station 09132500 located within Segment 6b. Based on the RPA, the Division has determined that there is no "reasonable potential, " and it is appropriate to remove effluent limitations for Outfall 017 for potentially dissolved iron. Because the discharge at Outfall 017 is to Sylvester Gulch, a use protected receiving water, in accordance with Regulation No. 31, the removal of effluent limitations for potentially dissolved iron is not subject to the antidegradation review process. This removal of effluent limitations is also consistent with the exception to the CWA's backsliding prohibition, expressed at CWA section 402 (o) (2), when information is available which was not available at the time of permit issuance. In these circumstances, the "new information" is the resegmentation of the receiving water which has resulted in removal of the water supply classification for Sylvester Gulch. With this change, effluent limitations and reporting requirements for potentially dissolved iron have been deleted from the tables in Part LA. 1. d and Part 1. B.1. d of the permit, respectively. The Division concurs with the permittee's request to identify the test species used to conduct acute 48-hour, whole effluent toxicity (WET) tests as Daphnia magma. Part I.A.S.a of the permit has been changed to reflect this change" (CDPHE, 2009a). • June 2009 HydroGeo, Inc.