SITE INFORMATION AND CORRESPONDENCE 1980-1999

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State Water Resources Control Board Resolution No. 68-16 states, in part, that"[a]ny activity which produces or may produce a waste or increased volume or concentration of waste and which discharges or proposes to discharge to existing high quality waters will be required to meet waste discharge requirements which will result irrthe best practicable treatment or control of the discharge necessary to assure that (a) a pollution or nuisance will not occur and (b) the highest water quality consistent with maximum benefit to the people of the State will be maintained." In revising the proposed permit to include appropriate mass limitations, staff should consider the State Board position on this subject--guidance which is binding on the Regional Board. In Order No.WQ 90-5,the State Board directed the San Francisco Regional Board on the appropriate method for establishing mass-based limits which comply with the State and federal antidegradation policies. In that 1990 Order, considering a petition relating to the South San Francisco Bay sewage plants,the State Board articulated the following general principles: In order to comply with the federal antidegradation policy,the mass loading limits should also be revised,based on mean loading, concurrently with adoption of revised effluent limits. The [mass] limits should be calculated by multiplying the [previous year's] annual mean effluent concentration by the [four previous year's] annual average flow. Order No. WQ 90-5 at 78. The reason the State Board ordered the mass limit equation revised was to hold the South Bay plants to their actual performance so as not to violate the antidegradation policy: The South Bay permits allow both an increase in the volume of the discharges, as well as an increase in the mass emissions of toxic pollutants over current levels. To illustrate,the actual 1989 mass emissions from the - three treatment plants was 47,600 pounds per year(lbs/yr). Allowable mass emissions under the revised mass emission limits total 67,968 lb/yr. Thus, the permits allow a lowering of surface water quality below the highest levels achieved since 1975, and the federal [antidegradation] test must be applied. Likewise, State Board Resolution No. 68-16 is applicable. Order No.WQ 90-5 at 73 (emphasis added). Hence, the State Board Order finds that any mass limit that fails to lock in the "highest levels achieved since 1975" must comply with the antidegradation policy. The State Board articulates the appropriate equation which applies the last available annual mean concentration multiplied by the annual average flow over a prior four year period. See supra. The DeltaKeeper,Tentative NPDES Permit,Lodi, 17 December 1999,Page 6.