SITE INFORMATION AND CORRESPONDENCE CASE 2

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• STAFF REPORT .4_ PAT MITCHELL AND CALIFORNIA NATURAL PRODUCTS LATHROP, SAN JOAQUIN COUNTY Rapid Infiltration verses Slow Rate Treatment System The Discharger describes the wastewater application system as a Rapid Infiltration(RI) system. This is in contrast to staffs position that the wastewater be applied in accordance with a typical Slow Rate system. Staff's objections to the RI system are listed below: • The RI system proposed by the Discharger does not include cropping activities to take up wastewater nutrients. • The application rate proposed by the Discharger exceeds any reasonable agronomic usage of crops. . • The wastewater loading rate proposed by the Discharger(600 lbs BOD per acre-day)is likely to create objectionable odors for nearby residents. Residential areas exist within 50 feet to the west and within 400 feet to the east of the land application area. BOD Loading Rate The Discharger states the BOD limits presented in the WDRs are overly restrictive. Pollution Abatement in the Fruit and Vegetable Industry, published by the United States Environmental Protection Agency(US EPA Publication No. 625/3-77-0007) (hereafter Pollution Abatement)is cited by the Discharger as lending support for a loading rate of 6001bs/acre• day. However,the value cited by the Discharger is inappropriate because crops will be grown on the land application area(see nitrogen compound discussion below). Staff believes the appropriate BOD value that should be selected from Pollution Abatement is 100 lbs/acre- day. This value should be protective of groundwater quality and crop health and should not generate nuisance odor conditions. This position is based on the staff's experience and the loading rate guidance for rapid infiltration systems presented in Small and Decentralized Wastewater Management Systems (Crites and Tchobanoglous, 1998) (hereafter Wastewater Management Systems)which states BOD loading beyond 300 lb/acre- day requires careful management to avoid odor production. Wastewater Management Systems states that loading rates for BOD often exceed 100 lb/acre day and occasionally exceed 300 lb/acre- day, odor problems are avoided by providing adequate drying times between wastewater applications and loading rates beyond 4501b/acre• day of BOD should generally be avoided unless special management practices are used. Because of the close proximity of residential areas and the limited land area available for wastewater application,BOD loading rates which require special precautions are not appropriate in this case. Pollution Abatement also states if the BOD loading is too great,the soil will become anaerobic and the crop and treatment process will fail,but that higher loading rates are possible if the site is irrigated for only a few weeks each year and is well maintained. CNP operates 365 days a year, so the application areas will not have the opportunity to rest. Because of the limited land area