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INFORMATION SHEET • • - 15 - MUSCO FAMILY OLIVE COMPANY AND THE STUDLEY COMPANY WASTEWATER TREATMENT AND LAND DISPOSAL 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.I 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. The Discharger has requested that the salt limitation be expressed as"dissolved inorganic solids"(DIS) instead of"total dissolved solids" (TDS). TDS consists of both inorganic salts and a volatile component including sugars and carbohydrates. The Discharger indicates that the effluent limit should only apply to the inorganic portion. However, the effluent limitation is expressed as TDS for several reasons. First, if wastewater is overloaded onto the land application areas, then the volatile component may not be fully removed and a DIS value may not fully measure the extent of dissolved solids which are entering the groundwater. More importantly, the water quality criterion is expressed as TDS, not DIS. This Order must be fully protective of the groundwater and therefore the effluent limitation must be expressed as TDS. 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.