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! n 4 4 Echemical, and organic chemical analyses were performed. The arsenic result, I 1 µglL, exceeds the federal primary maximum contaminant level (MCL) for arsenic (i.e., 10 µg/L). The total dissolved solids (TDS) result, 830 mg/L, exceeds the California recommended secondary MCL range for TDS and suggests that salinity could be problematic. The California recommended, upper, and short-term secondary MCL ranges for TDS are 500, 1000, and 1,500 mg/L, respectively. All other results were less than the applicable primary and secondary maximum contaminant levels. The iron concentration was 50 µg/l, and manganese was not detected. The nitrate result, 3 5.1 mglL as NO3, is greater than 50 percent of the nitrate MCL. For reference, water quality data excerpted from the nitrate study document are presented in Appendix A. ,. The City of Lathrop (City) currently faces a variety of groundwater quality issues, including: ; compliance with the federal arsenic MCL, potential saline intrusion, and compliance with the i California secondary MCL for manganese. Historically, arsenic concentrations in water samples from City wells have ranged from 12 �.gIL to 25 µglL [3]. Groundwater TDS concentrations i within the City could be increasing. A groundwater model that was used to support City potable water supply master planning efforts [4] predicted that TDS concentrations at City wells could reach 500 mglL by 2025. At one of the City wells, Well 21, treatment is required for manganese removal. 3.0 DESCRIPTION OF PROPOSED WATER SUPPLY AND TREATMENT SYSTEMS i The proposed KMC water supply and treatment systems will satisfy the small public water system requirements of the SJCEHD, the fire flow requirements of the LMFPD, and applicable state and federal drinking water standards. The water systems will include the following major elements: 1) a potable water supply well, 2) a well with sufficient capacity to satisfy fire-fighting demands, 3) a hydropneumatic storage tank, 4) treatment systems for disinfection and arsenic removal, and 5) a network of distribution piping and valves. Arsenic removal treatment is included based on local groundwater quality information, and may be deemed unnecessary following KMC well water testing. The design capacity of the potable water supply well will be approximately 50 gpm. This capacity, assuming 18 hours of operation per day, will be sufficient to satisfy the estimated potable water demands. The design capacity of the fire-fighting well will be greater than or equal to 3,000 gpm and will comply with LMFPD fire flow requirements. A generator set and automatic transfer switch will be installed to supply emergency power for well and treatment system operation during electrical service interruptions. The capacity of the hydropneumatic tank will be sufficient to prevent excessive starting of pumps. : Treatment systems will be sized to treat water for potable uses only. Water used to fight fires will not be treated. Sodium hypochlorite solution will be injected into raw well water for disinfection. A pre-packaged, modular water treatment system will be provided for arsenic removal. The system will include multiple pressurized vessels filled with adsorptive media. The vessels will be configured in parallel, and the system will be semi-automated. Location of treatment equipment within locked, multi-use structures is anticipated. Treated water will be distributed for use throughout the site. x MTBO 15600 KMC—Water Pre-Application Information 3 n:lmtbOl560olreportslwater pre-applfinal 041907.doc September 2007