SITE INFORMATION AND CORRESPONDENCE_CASE 2

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REGIONAL WATER BOARD RESPONSE (SWRCB/OCC File A-1846(a) and A-1846(b)) -22- PETITIONS FOR REVIEW OF W, — E DISCHARGE REQUIREMENTS ORDER NO. R5-2007-0036 (NPDEa NO. CA0079154) AND TIME SCHEDULE ORDER NO. R5-2007-0037 CITY OF TRACY, WASTEWATER TREATMENT PLANT proposal." (40 CFR § 122,2,) (See also, CWA § 306(a)(2).) Treatment plants are subject to statutory technology-based standards, and not new source performance standards under Section 306. Thus, even an expanded treatment plant is not a "new source." The treatment plant expansion was subject to CEQA analysis at the local level, since Section 13389 does not cover local permitting actions. Order R5-2007-0036 includes an antidegradation analysis, in accordance with State Water Board's Antidegradation Policy (Resolution 68-16), that considered the water quality impacts due to the expanded discharge. The Discharger's Environmental Impact Report was considered in this evaluation. The Order requires tertiary treatment or equivalent, which is a high level of treatment that is considered best practicable treatment or control (BPTC) for most constituents in the wastewater and will result in attaining water quality standards applicable to the discharge. With regards to temperature, the discussion in the Fact Sheet about the discharge causing an exceedance of a Thermal Plan requirement is based on modeling at the expanded discharge flow of 16 mgd. Effluent and receiving water limitations are included in the Orderthat implement the Thermal Plan. The Discharger is capable of complying with these limitations at the current discharge flow of 9 mgd. The Discharger must demonstrate compliance with these limitations before the discharge flow to Old River may be increased or shall have obtained an exception to the Thermal Plan requirements, which would necessitate modification of the limitations. CSPA — CONTENTION N: A significant number of the Effluent Limitations are not limited for Mass. The federal regulations require mass limitations for POTWs, but include specific exceptions. 40 CFR section 122.25(f)(1)(ii) states that mass limitations are not required when applicable standards are expressed in terms of other units of measurement (e.g. concentration). The water quality-based effluent limitations for chlorodibromomethane, dichlbrobromomethane, aluminum, and manganese are based on water quality criteria that are expressed in terms of concentration. Pursuant to 40 CFR section 122.25(f)(1)(ii), expressing the effluent limitations in terms of concentration is expressly allowed. Including additional mass limitations for these constituents, which would simply be calculated based on the concentration-based WQBEL and the Facility's design flow, are not necessary for protection of the beneficial uses of the receiving water. The Regional Water Board includes mass limitations, in addition to the concentration limitations, when the mass limitations are necessary to protect the beneficial uses of the receiving water (e.g. for bioaccumulative constituents or oxygen demanding substances).