SITE INFORMATION AND CORRESPONDENCE_1985-2004

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REGIONAL BOARD RESPONSE (SWRCBIOCCFILEA-1634) - 6 - PETITION 6 - PETITION FOR REVIEW OF WASTE DISCHARGE REQUIREMENTS ORDER NOS. R5-2004-0028 AND R5-2004-0029 CITY OF MANTECA WATER QUALITY CONTROL FACILITY The Regional Board properly adopted effluent limitations for copper based on the numerical water quality objective in the Basin Plan. All effluent limitations are supported by substantial evidence in the record. Please refer to permit finding 32, information sheet section 11.1,permit tables 9 and I I and the 19 March 2004 response to comments document (page 16,Item No. 4, Binder No. 1) for more information on copper. THIRD BASIS: IMPROPER IMPOSITION OF EFFLUENT LIMITATIONS FOR MBAS Manteca requests that the State Board modify, or order the Regional Board to modify, Order No. R5-2004-0028 to remove the effluent limitations for MBAS and Order No. R5- 2004-0029 to account for the removal of the inappropriate effluent limitations for MBAS. Alternatively, Manteca requests that the State Board modify, or order the Regional Board to modify, Order No. R5-2004-0028 to include effluent limitations for MBAS calculated using the harmonic mean dilution credit of 222:1, and Order No. R5-2004-0029 to account for the recalculation of the effluent limitations for MBAS. The discharge of M 3AS was found to have a reasonable potential to cause or contribute to an in- stream excursion above the Basin Plan narrative chemical constituents objective, and the narrative objectives for floating materials, tastes, and odors. As such, an effluent limitation for MBAS is required and was included in Order No. R5-2004-0028. The validity and applicability of the Basin Plan narrative chemical constituents objective for MBAS and the use of an MCL as a criterion to protect water quality are addressed in the 19 March 2004 Response to Comments,pages 5-6 and 8-9. The relation of foaming and MBAS concentrations was discussed in the 19 March 2004 Response to Comments,page 25. A Notice of Violation was issued 1 April 2003 due to observed foaming(Item No. 77, Binder No. 4). Seven additional pieces of correspondence regarding foaming were exchanged over the following months (Item Nos. 14 and 21 of Binder No. 1 and Item Nos. 52, 60, 66, 69, and 75 of Binder No.4). The investigations do not exclude the possibility that MBAS may contribute to the observed foaming. As discussed in Section 9.6 of the Information Sheet,harmonic mean or other dilution is not appropriate for MBAS in order to protect the receiving water from a potential contributor to the observed foaming at the outfall. Also note slides 16 and 17 of the 19 March 2004 Regional Board presentation(Item No. 2, Binder No. 1).