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INFORMATION SHEET MUSCO FAMILY OLIVE COMPANY AND THE STUDLEY COMPANY WASTEWATER TREATMENT FACILITY SAN JOAQUIN COUNTY Discharge Specifications B.4 through B.6 These specifications are required to address nuisance odor conditions that have been documented at the facility. The Discharger proposed the Specifications found in B.5. Effluent Limitation C.1 Loading limits are needed because excessive loading of nondegradable solids can result in exceeding the capacity of the cropped land application areas to take up the solids and subsequent groundwater degradation. To determine the appropriate concentration limits for the wastewater, staff reviewed the Designated Level Methodology for Waste Classification. Because the discharge is planned to continue indefinitely, the use of an attenuation factor is not appropriate because all the attenuation processes will become saturated over time. Therefore, the effluent limits are set by the background groundwater quality. Monitoring wells MW-1 and MW-8 are likely the most representative of water quality that has not been impacted by the waste stream. The effluent limits were calculated by adding one standard deviation to the average concentration and then rounding up. The resulting effluent limitations are 1,500 mg/1 of TDS, 150 mg/l of chloride, and 290 mg/1 of chloride. Effluent Limitation C.2 Loading limits for nitrogen are required because excessive loading of nitrogen can result in a build up of nitrogen in the soil column and eventual leaching to groundwater. The Discharger has presented a plan to crop the land application areas to remove all applied nitrogen. Because crop health in land application areas has historically been poor, the crop may not be able to take up all the applied nitrogen. Limiting total nitrogen loading to the agronomic rate for the crop ensures that all available nitrogen is taken up by the crop and not available to leach to the water table. Because there is no site-specific data to determine the denitrification potential in the vadose zone, staff have selected a conservative approach which is based on the assumption that 100%of the total nitrogen applied is ultimately available for plant uptake or leaching. This approach is appropriate until the Discharger completes a more definitive study of groundwater quality and site-specific nitrogen uptake rates. Effluent Limitation C.3 Loading limits for BOD are needed because excessive loading can deplete soil oxygen and cause anaerobic conditions. Anaerobic degradation of organic matter can cause severe nuisance odors and promote incomplete biodegradation, thereby allowing dissolved organic material to percolate through the unsaturated zone into groundwater. Anaerobic decomposition of organic wastes also creates organic acids that decrease soil pH. A low pH environment can cause excessive leaching of metals in the soil into underlying groundwater. This Discharge Specification prescribes a maximum BOD loading of 300 lbs/acre on any one day, and 100 lbs/acre/day as a 7-day (weekly) average. The weekly average loading limit of 100 lbs/acre/day is based on U.S. Environmental Protection Agency Publication (USEPA) guidelines provided in Pollution Abatement in the Fruit and Vegetable Industry— Wastewater Treatment (USEPA 625/3-77-0007) (hereafter Pollution Abatement). Although the RWD states that the yearly average BOD loading will be less than 70 lb/ac/day, a review of the most recent self-monitoring report (May 2002) shows that the Discharger may not be able to meet the daily or weekly limitations. The Discharger has already proposed