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California regional eater Quality Control Board 1 r , Central Valley Region . Steven T.Buller,Chair Winston 11. llickos Cray Davis Scercrnn;ior Sacramento Main Office invcmor Emimnmrmal Inianet Add=: httpolw^.v -s b.=.gov/-�gcb5 Pmrceunn 3473 Routim Road.Suitc A.Saerammto,Caliromiu 9SE27-3003 - Phone(916)-255-3000•FAX(916)255.3015 16 December 1999 Mr. Jon Crawford Public Works Director City of Lathrop 16775 Howland Road, Suite 1 Lathrop, CA 95330 REVIEW OF REPORT OF WASTE DISCHARGE AND REQUEST FOR ADDITIONAL INFORNLATION, CITY OF LATHROP, SAN JOAQUIN COUNTY A report of waste discharge (RR'D)was submitted by the City of Lathrop (City) on 13 August 1999,to the Regional Water Quality Control Board (Board). The City is requesting a new National Pollutant Discharge Elimination System (NPDES)permit for a wastewater treatment plant expansion to accommodate future development. We met with you, other City representatives, Califia Development Group, and Libbey Owens Ford Company on 17 November 1999 to discuss the difficulties that lie ahead for permitting a new discharge to the San Joaquin River, an impaired surface water body. The Sacramento-San Joaquin Delta is impaired due to low dissolved oxygen, salts,mercury,persistent organochlorine pesticides, diazinon, chlorpyriphos,DDT, and unknown toxicity. Studies to determine Total Maximum Daily Loads (TMDLs)for these constituents are not yet complete. Therefore,pc utant load allocations for individual dischargers have not been determined. In addition, other constituents may require effluent limits if they cause or have reasonable potential to cause or contribute to an excursion above a water quality objective. An interpretation of the regulations is that any new NPDES permit must include stringent effluent limitations to ensure no increase in loads to the Delta. However, growth in the area is inevitable, and the City's proposed tertiary treatment facility will cause less impact on the beneficial uses of the Delta than an increase in secondary discharge from an existing facility. In addition,the.City has indicated a willingness to maximize land disposal to the extent feasible and to discharge only highly-treated effluent at times of the year when the receiving water has assimilative capacity. These were two significant factors in our decision to agree to proceed with drafting an NPDES permit for the City. To begin drafting a NPDES permit,Board staff require information showing that a new discharge to the river will not cause or contribute to an impairment. The City must provide an estimate of the quantity and quality of the proposed discharge and a determination of the impact of each constituent in the discharge on Delta waters,particularly for constituents on the 303(d) list. A determination will then be made on what discharge can be allowed under federal and state law. We must emphasize that there is no guarantee that the Board will adopt an NPDES permit once it is drafted. In addition, if the Board adopts !`.7:l----:.-