SITE INFORMATION AND CORRESPONDENCE

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WASTE DISCHARGE REQUIREML, TS ORDER NO. • 4 CITY OF LATHROP AND METROPOLITAN LIFE INSURANCE COMPANY CROSSROADS TREATMENT PLANT NO. 1, SAN JOAQUIN COUNTY basins into lined storage ponds, converting nearby undeveloped land into bermed wastewater application areas, and installing piping necessary to deliver the treated wastewater to the new land application areas. 18. The three storage ponds when constructed, will provide approximately 121 ac-ft of storage. The ponds were sized to contain wastewater and rainfall with an annual total return period of 100 years. 19. The Discharger has proposed three land application areas totaling 43.8 acres. The land application of wastewater will be performed at agronomic rates. Cropping activities will be performed to maximize the treatment of the wastewater and take up nitrogen and some dissolved solids. 20. Wastewater will not be disinfected prior to land application. All applied wastewater and rainfall which falls on the wastewater storage ponds or land application areas will be contained within the pond or bermed areas. 21. Water will be applied by surface irrigation or sprinkler to irrigate crops at agronomic rates consistent with both the nutrient content of the effluent and the water needs of the crops. The Discharger will supplement recycled effluent with fresh water as needed to maintain crop health. Rainfall and the lower total dissolved solids concentration anticipated from domestic wastewater sources are expected to control dissolved solids concentration in percolate and soil salinity. 22. Land application areas will include a perimeter road on a berm three feet higher than the land application area. 23. The Discharger has completed a water balance for the expanded facility to demonstrate that adequate treatment, storage and disposal capacity is available for a flow rate of 250,000 gpd. The water balance was prepared based on crop water and nutrient needs, quality and quantity of applied water, and application of site historical climate data. The water balance was based on 100-year annual return total rainfall amounts. Site-Specific Conditions 24. Annual precipitation in the vicinity averages approximately 13.31'inches. The meanpan evaporation rate is approximately 41.36 inches per year. All portions of the facility are outside the 100-year flood zone. 25. The facility lies within the San Joaquin Delta Hydrologic Unit Area No. 544.00, as depicted on interagency hydrologic maps prepared by the Department of Water Resources in August 1986. 26. Nine groundwater monitoring wells exist at the wastewater treatment facility and evaporation/percolation ponds. Four additional wells were installed in the proposed land application areas and one well was installed outside the land application areas. Based on boring log data from monitoring wells, shallow soils in the area are described as silty sand with clay lenses. Historically, the evaporation/percolation ponds did not percolate wastewater as anticipated.