2009-07-01_REPORT - C1980007 (6)

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West Elk Mine 2008 Annual Hydrology Report exceedances are attributable to the amount of grey water in the influent to Outfall 007A i from showers, sinks, and floor drains. The low concentration of solids in the gray water makes consistently meeting the 85% removal for BOD and TSS extremely difficult. " 44 In order to address the percent removal issue, MCC met with Andrew Neuhart of the Colorado Department of Public Health and Environment (CDPHE) Water Quality Control Division (WQCD) on September 11, 2008. Subsequent to this meeting, MCC prepared a permit modification for submittal to the WQCD to address this recurring operational issue. In order to address the percent removal issue, representatives of MCC met with Kelly Morgan of and Andrew Neuhart of the CDPHE WQCD on September 11, 2008. Subsequent to the aforementioned meeting, on October 30, 2008, MCC submitted a CDPS permit modification request including (in part): modification of the total suspended solids (TSS) limits for Outfall 007 and modification of the percent removal requirement for five-day, biochemical oxygen demand (BODO and TSS for Outfall 007. The WQCD 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 Discharger's request to modify effluent limitations for TSS at Outfall 007, where treated domestic wastewater is discharged from the 0.02 mgd (design) West Elk Wastewater Treatment Plant (WWTP). This WWTP which meets the Division's definition of a "domestic wastewater treatment plant" [5 CCR 1002.22 (10)], is subject to the requirements established in Regulation No. 62. Regulation No. 62 establishes applicable TSS limitations of 30 and 45 mg/L (30-day and 7-day averages, respectively), which can be adjusted for waste stabilization ponds which treat domestic waste provided that (1) the waste stabilization ponds are the principal process used for secondary treatment, and (2) the facility is designed to achieve the solids removal possible with best waste stabilization pond technology. "Best waste stabilization pond technology" is defined by Regulation No. 62 as that design criteria for ponds currently in effect as adopted by the Water Quality Control Commission or by the Division. In accordance with Regulation No. 62 requirements for aerated waste stabilization ponds, the Division has therefore adjusted applicable TSS limitations for this facility to 75 and 110 mg/L (30-day and 7-day averages, respectively) based on the Discharger's representation that "best waste stabilization pond technology" is currently in place. Because the discharge at Outfall 007 is to Sylvester Gulch, a use protected receiving water, in accordance with Regulation No. 31, this relaxation of effluent limitations for TSS is not subject to the antidegradation review process. This change in TSS limits is also consistent with the exception to the CWA's backsliding prohibition, expressed at CWA section 402 (o) (2), when a technical mistake or a mistaken interpretation of law was made in establishing the original, lower TSS limits. In these circumstances, the Division had not recognized the eligibility of the WWTP for the "adjusted" limits allowed by Regulation No. 62. With this change, the TSS limitations have been changed in Part LA. 1. e. iv of the permit. The Division concurs with the Discharger's request to replace the 85 percent removal requirement for BOD5 and TSS at Outfall 007 with mass based, 30-day average limitations of 5 lbs/day and 12 lbs/day, respectively. Regulation No. 62 permits such a change when the permittee has demonstrated that the WWTP is unable to meet the 85 percent removal requirement, and that inability is not caused by excessive infiltration to the sewer system. In these circumstances the Discharger has shown that a large amount of grey water from showers, sinks, and floor drains results in very dilute influent, causing an inability to meet the 85 percent removal requirement. The Discharger states that "there is no measurable infiltration of water within the system, and it would be difficult and very expensive for the West Elk Mine to modem the system to meet the 85 percent removal requirement. " The Division has therefore established mass based,30-day average not-to exceed limitations for BODs and TSS, to replace the percent removal requirements of the permit, of June 2009 HydroGeo, Inc.