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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division <br />• Amendment No. 4 Rationale - Page 2. Permit No. CO-0027154 <br />PURPOSE OF AMENDMENT: <br />This amendment (No. 4) includes changes to the total recoverable manganese <br />limitations in the permit, The existing limits for total recoverable <br />manganese (1.0 mg/1 - 30 day average, and 2.0 mg/1 - daily maximum) will now <br />be applicable to the total of ,the three existing continuous discharges, <br />discharge points 001, 005, and 007, which are now identified as discharge <br />point 019, Monitoring for total recoverable manganese is still specified at <br />discharge points 001, 005, and 007, as well as all the other applicable <br />limitations and monitoring which are required for each of these three <br />outfalls. For outfall 019, requirements include monitoring For flow and <br />limitations and reporting calculations of monitored data for total recoverable <br />manganese. <br />DISCUSSION: <br />Colorado Yampa Coal Company (CYCC) has had problems meeting the total <br />recoverable manganese limits set forth in the permit at discharge point 007. <br />The exceedances occurred in the late winter and early spring of 1989. The <br />data attached to the CYCC Amendment No. 4 request indicates that the manganese <br />exceedances are a seasonal occurrence, and probably will not occur again until <br />early in 1990. This amendment takes into account the upstream discharges from <br />001 and 005 which have lower manganese concentrations and which were not <br />• reflected in the previous calculations of the permit limitations Eor total <br />recoverable manganese. <br />In a letter dated July 11, 1989, Colorado Yampa Coal Company (CYCC) requested <br />that the existing limitations for total recoverable manganese in their permit <br />be modified to be based upon a "Waste Load Allocation" (WLA) method, which was <br />proposed by CYCC. According to this WLA method, the existing limits for total <br />recoverable manganese (1.0 mg/1 - 30 day average, and 2.0 mg/1 - daily <br />maximum) will be applicable to the total of discharge points 001, 005, and 007 <br />(which are collectively identified as discharge point 019). <br />The WLA method for the three discharge points is determined for ECtotal <br />according to the following equation. <br />(EF001) (E0001) + (EF005) (E0005) + (EF007) (E0007) _ (EFto[al) (ECtotal) <br />or <br />(ECtotal) _ (EF001) (E0001) + (EF005) (E0005) + (EF007) (E0007) <br />(EFto[al) <br />Where: EF001 = maximum daily effluent flow from discharge point 001, MGD <br />EF005 = maximum daily effluent flow Erom discharge point 005, MGD <br />EF007 maximum daily effluent flow from discharge point 007, MGD <br />EFtotal maximum daily flow from all discharges (001 , 005, 007) <br />E0001 = daily total re coverable manganese effluent concen tration <br />• from discharge point 001, mg/1 <br />