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RUG-05-1994 16:10 FROM Public Works TO 94640138 P.01 State of CA-CWW(?CB-(914)255-3030(wti fx set-up)-Crewed:20 MV 1994 13:47- Page 1 of 1 M________-.__________________________.- i rd INFORMATION SHSEI' CITY OF LATHROP CROSSROADS SANITARY CORPORATION AUG 0 8 1994 LATHROP INDUSTRIAL WASTEWATER TREATMENT PLANT SAN JOAQUIN COUNTY ENVIRONMENTAL HEALTH PERMIT/SERVICES The City of Lathrop proposes to build and operate a wastewater collection,treatment,and disposal system, and will ultimately provide sewerage service to a 500 acre commercial, warehousing, and light industrial development. The treatment plant will be designed and constructed to handle the ultimate `build-out' flow of 0.6 mgd. The treatment plant and disposal ponds are to be built on land owned by Crossroads Sanitary Corporation. Wastewater is anticipated to be similar in nature to domestic wastewater. The treatment system will include an extended aeration activated sludge process(Schreiber process),then chlorination,as needed, prior to being discharged to a designated disposal area. The disposal area will consist of disposal ponds that will be constructed based on the following anticipated disposal needs: Phase MQuthly_A S_Ruut PondDisl .area ph areQtpasifyEmm_rt-un 1 0.2 mgd 7.2 acres 5 years II 0.4 mgd 14.2 acres 10 years III 0.6 mgd 21.1 acres 15 years These Waste Discharge Requirements will allow discharge and disposal for the anticipated flows associated with the Phase I construction efforts only. Sludge will be dewatered by vicuum-assisted drying beds, and is proposed to be disposed by land application. The treatment plant area has very shallow ground water,and 6 domestic wells within 1000 feet of the facility. These conditions raise concern regarding pathogen transmission and nitrate contkentrations in the ground water,as well as potential problems with pond disposal capacity. In order to prevent pathogen transmission, the City proposes to chlorinate the wastewater prior to discharge into the disposal ponds if total colifban organisms exceed 2.2 MPNI100ml in groundwater. Discharge Specifieatiou B.4.contains limits of 30 mg/l each for BOD and suspended solids, in order to enable the chlorine to effectively kill pathogens. Filtration through the soil column should further reduce coliform concentrations, Ground water will be monitored for total coliform to evaluate compliance,and purgeable halocarbon analyses will evaluate if any tribalomethane compounds are generated from the chlorination process, To address the nitrogen concerns,the City proposes to meet an average discharge limit of 10 mgll total nitrogen(as N). Ground water Lin-4tation D.1.prohibits wastewater from causing a statistical increase over background concentrations. Discharge monitoring for total nitrogen and ground water monitoring for nitrates will be conducted to assess compliance. Provision E.14. requires verification monitoring followed by investigation and remedial action for any violations of ground water limitations. Finally, Discharge Specification S.S.requires a minimum of five feet of separation be maintained between the bottom of the disposal ponds and the highest elevation of ground water,and Discharge Specification B.B.requires adequate capacity be maintained to accommodate wastewater flows. Technical reports are required to be,submitted that detail how these specifications will be met. Post-H"Fax Note 7671 $s qr.( Vi a► To KAJAAlFtum f L�Jr— CofOairt. PMrM4 Phmeit�7O^�(.LJ 7.� Fax Y ` t h Fax n