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TRACY WWTP-TASK 14 TOS MONRORING WFL L INSWT"WORK PLAN Two of the sludge drying beds (Beds 4 and 5)now are asphalt-lined to evaluate potential improvement in sludge drying time. Pavement consists of seven inches of aggregate base overlain by four inches of asphaltic concrete. Operation of the paved beds is similar to the sand-lined beds,with both decanting of supernatant and evaporation to remove water. Biosolids Storage Area The biosolids storage area is located immediately north of the sludge drying beds. Periodically,dewatered biosolids are removed from the drying beds and stored in the plant's emergency storage pond. Hauling companies are hired about once per year to remove accumulated solids from the storage area. The solids are hauled offsite and applied as soil amendment to agricultural land or used as alternative daily cover at solid waste landfills. Lined Pretreatment Lagoons Two lined pretreatment lagoons are located immediately east of the sludge drying beds and biosolids storage area. These lagoons receive wastewater from the Leprino Foods facility through a dedicated pipeline. Each lagoon is 100 by 150 by 25 feet The lagoons are each lined with a reinforced rubber geotextile material(ethylene propylene diene monomer- EPDM-or neoprene),protected by a layer of rip rap. The freeboard in the ponds is maintained at over 3 feet. The biochemical oxygen demand(BOD)of the water entering the lagoons is high (approximately 4,000 mg/L). Waste within the pretreatment ponds is aerated using a coarse bubble aeration system and nitrogen in the form of urea is added to provide a proper nutrient balance.The ponds act as completely-mixed aeration basins.The air and nutrients promote growth of bacteria that consume BOD in the wastewater. After treatment, 130D is about 300 to 400 mg/L. Treated wastewater from the pre-treatment lagoons then is transferred to the holding ponds for additional treatment. Proposed Monitoring Well Locations Sampling of the Spreckels Sugar monitoring well located immediately downgradient of the Sludge Drying Beds and the Biosolids Storage Area(WP-1)do not indicate that groundwater quality has been impacted by these facilities(CH2M HILL 2005). Additionally, the Lined Pretreatment Lagoons are constructed partially above grade to enable visual observation of potential leakage(CH2M HILL 2005). The City is proposing to install additional monitoring wells to comply with the waste discharge requirements(WDR) terms proposed by the CVRWQCB. Historical data indicates the direction of groundwater flow in the shallow unconfined aquifer is to the north(Figure 3),which is consistent with the gradient direction observed based on the holding pond monitoring well data(CH2M HILL 2005). This information and the location of City-owned property were used to determine proposed monitoring well locations. The City is proposing to install three monitoring wells downgradient of the facilities for which the CVRWQCB has requested monitoring(Figure 5).Two sites(Sites A and B)are located immediately downgradient of the three facilities and the third is upgradient(Site Q. OddM 31,2007 3