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Additionally, the draft permit requires the permittee to conduct mechanical in- tegrity testing prior to commencing injection and annually thereafter in order to demonstrate that underground sources of drinking water (USDWs) are being protected. The draft permit requires the permittee to conduct extensive testing of the injection zone, the confining zone, and other formations encountered during the drilling of the well. f. HvdrogeoloQy of Iniection And Confining Zones EPA staff evaluated the subsurface geology of the proposed injection area by analyzing seismic data, well logs, well history reports, published maps, cross sections and reports. 2. PRETREATMENT PRIOR TO INJECTION Process plant waste water will be collected at the raw waste water pump station. Then it will be pumped to the existing preliminary treatment facilities which in- clude a fine rotary screen (0.020 inch openings) to remove coarse particles followed by a dissolved air floatation (DAF) unit for removal of fats, oils, and greases (FOG) and total suspended solids (TSS). Following this treatment the waste water will be further treated by a new activated sludge treatment facility. DAF effluent will be discharged to an equalization basin. The equalization basin will serve to regulate the flow into the activated sludge process and reduce the possibility of shock load- ings. From the equalization basin, waste water will be pumped to the activated sludge system. The activated sludge system will consist of an aeration basin and clarifier. Waste sludge will be aerobically digested and dewatered in sludge drying beds prior to final disposal. Sludge disposal must be approved by the RWQCB. Waste waters from the activated sludge process will be chemically treated with polymers, chlorinated, and filtered through a sand filtration unit. The filtered ef- fluent will be comingled with the extracted, polluted groundwater in a tank prior to being fed into the deep injection well. The proponent does not plan to add a biocide to the treated waste waters. The Agency may permit small modifications from this pretreatment plan without further public comment if required by site conditions. 3. GROUND WATER QUALITY AT THE INJECTION SITE The total dissolved solids (TDS) content of the formation water from the Domengine formation at the proposed injection site is approximately 7500 ppm. Although this aquifer qualifies as an underground source of drinking water under federal law, practically speaking the water is too salty to drink or use for irrigation without treatment, and does not qualify as drinking water under California state law. The waters to be injected have a TDS level of approximately 3500 ppm and are therefore less saline than the existing ground water in the injection zone. 3