SITE INFORMATION AND CORRESPONDENCE_1985-2004

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REGIONAL BOARD RESPONSE (SWRCB/OCC FILE A-1634) - 5 - PETITION 5 - 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 is required by the Clean Water Act, the Porter-Cologne Water Quality Control Act, and the plans and policies of the State and Regional Boards to protect the beneficial uses. The secondary MCL for iron protects the beneficial use of municipal and domestic supply (MUN). The Basin Plan defines MUN as the"uses of water for community, military, or individual water supply systems including, but not limited to, drinking water supply'. One cannot assume that all water removed from the river for this beneficial use is treated,whether used as drinking water or other domestic uses. Effluent limitations based on the secondary MCL are appropriate to protect the beneficial use of MUN. See pages 8-9 and 23-24 of the 19 March 2004 Response to Comments (Item No. 4, Binder No.1). Please refer to permit finding 47, information sheet section 9.4,permit tables 3 and 6, and the 19 March 2004 Response to Comments document(pages 5-6, 8-9, 23-24 and 35-36,Item No. 4, Binder No. 1) for more information. SECOND BASIS: IMPROPER IMPOSITION OF EFFLUENT LIMITATIONS FOR COPPER Manteca requests that the State Board modify, or order the Regional Board to modify, Order No. R5-2004-0028 to include effluent limitations for copper based upon CTR criteria, and Order No. R5-2004-0029 to account for the recalculation of the effluent limitations for copper. In addition,Manteca requests that the State Board modify, or order the Regional Board to modify, Order No. R5-2004-0028 to allow dilution for acute toxicity in its recalculation of the effluent limitations for copper. The discharge of copper was found to have a reasonable potential to cause or contribute to an in- stream excursion above the Basin Plan numerical water quality objective. The CTR contains a criteria for copper. However, as stated in the CTR,the Basin Plan objective applies and not the CTR. As such, an effluent limitation for copper is required and was included in Order No. R5- 2004-0028. Little to no dilution exists for many constituents due to low river flow,tidally-induced flow reversals, limited mixing of the side bank discharge, and overlap of plumes from an adjacent discharge. The availability of acute dilution is addressed in pages 27-28 of the 19 March 2004 Response to Comments, in Finding 31 of the permit, and in Section 2 of the Information Sheet. Regarding Water Code Sections 13241 and 13242 issues, please see the response to the first basis. The validity and applicability of the Basin Plan numeric objective for copper versus the CTR were previously addressed in the 19 March 2004 Response to Comments,page 3 and pages 5-6.