SITE INFORMATION AND CORRESPONDENCE_CASE 2

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STAFF REPORT City of Tracy The City operates a secondary sewage treatment plant that discharges treated wastewater into Old River at a point approximately 4 miles north of the City. Waste discharge requirements Order No. 77-182 was adopted by the Board it. 24 June 1977. Tracy is requesting consideration of a relaxation of the total suspended solids (TSS) effluent limitation in its NPDES permit from 20 mg/l to 30 mg/l (monthly average) . During the period July 1977 through February 1978, there were numerous viola- tions of waste discharge requirements as revealed by Tracy's monthly self- monitoring reports. As a result, the Regional Board adopted a Cease and Desist Order, No. 78-52, which included a ban on additional wet industry connections . This action was followed by Order No. 79-54 which provided a schedule to correct the plant deficiencies and allow interim BOD and TSS standards of 35 mg/l (monthly average) . Tracy has performed an engineering analysis which considers process alternatives and has drafted an Environmental Impact Report which the State Board will consider in its funding eligibility decisions. In order to reestablish compliance with NPDES requirements, Tracy has sub- mitted an improvement project report under the Clean Water Grants Program thl-t addresses disinfection requirements and solids generation and handling problems . Tracy estimates the completion cost of this project at $5.7 million. However, even after completion of the improvement project, the City anticipates, that the 20 mg/l (TSS) standard may not be consistently met without an addi- tional expenditure of 2.2 million dollars that would provide an overland flow polishing system. Further, the City anticipates that a relaxed TSS standard of 30 mg/l can be consistently met based on their current operational experiFrr; and improvement project modifications. Staff concurs with this finding. CH2M/Hill , the consultant for the city of Tracy, performed an analysis evalua- ting impacts of the proposed increase of TSS on meeting coliform requirements and ultimate BOD in Old River. They concluded the increase would have a negligible effect on Old River and would not interfere with the ability of the plant to meet the permit's 23 MPN/100 mg/l coliform standard. CH2M/Hill furthermore determined that the effluent would contain less TSS than background levels in Old River for 9 months out of the year. During the remaining 3 months, the effluent TSS would be higher than background levels in Old River but river flows will be high, providing a high level of dilution. Board staff concurs with the findings. An additional basis for the original 20 mg/l TSS was the close proximity of the plant diffuser to a proposed state park. In 1976, the state withdrew the proposal in favor of Durham Ferry Park on the San Joaquin River. Therefore, the potential for adverse impacts on a recreational state park did not materialize. The Dept. of Fish & Game, and the local and state health departments were con- tacted concerning Tracy's requested relaxation. None expressed objections to the proposed TSS relaxation from 20 mg/l to 30 mg/1 .