SITE INFORMATION AND CORRESPONDENCE 1980-1999

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Mass Limitations The Regional Board staff has included mass limitations for numerous parameters in Section B 1 of the tentative Permit_ In effluent dominated streams such as Dredger Cut, concentration limits, not mass loadings, control whether aquatic life will be protected from a discharge. As such, the City believes that new, restrictive mass limits are not necessary to protect designated uses. The Permit Fact Sheet contains no explanation of the water quality basis for the mass limitations, nor does the Regional Board staff provide any findings justifying the limits. High flows in the area (which are well documented) warrant the calculation of mass limits based upon the expected wet weather flows. For example, the Regional Board staff established the TSS mass limitations based on dry weather flow of 7.0 mgd. The City objects to the adoption of restrictive mass limitations as unnecessary to protect beneficial uses and inconsistent with the available technical information that verified higher mass loading may occur without an adverse effect on standards-'compliance or beneficial uses, particularly under higher flow conditions. There must be a specific water quality basis for establishing more restrictive mass limitations more stringent than secondary treatment. (See, 40 CFR § 122.44(d).) EPA Guidance on the development of water quality-based limits specifies that such limits may be adjusted to reflect changes in effluent flow (i.e., vet weather periods) if such limits will not cause a violation of applicable water quality objectives. Based upon the available technical studies and the applicable NPDES rules, imposition of a mass limit for TSS, CBOD, DO, cyanide, zinc, and lead based upon a winter flow of 7.0 mad is not necessary or appropriate for the City's facility. As supported by the scientific information, the mass limits should be, at a minimum, be based upon an 8.5 mad design flow. NPDESPermitComments Exhibit 2 Page 24 12/17/99