COMPLIANCE INFO_1990-1998 - Laserfiche WebLink

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CITY OF TRACY 4 30 August 1990 SLUDGE MANAGEMENT PLAN JULY 1990 SLUDGE CHARACTERISTICS The Report states that about 9000 dry tons of sludge is stockpiled in the sludge drying beds and in an inactive oxidation pond near the plant. The sludge has been stored in these areas at the WWTP since disposal to Corral Hollow Landfill was discontinued in 1987. Also, sludge samples were collected during 1986 to 1989 from the plant's sludge holding tank, sludge drying beds, sludge stockpile. The results of these analyses were submitted to the Department of Health Services which classified the sludge as a nonhazardous waste. The annual sludge production from the WWTP from 1988 through 2008 is presented in Table 4 of the Report. CONSTITUENT LOADINGS AND APPLICATION AREA REQUIREMENTS Nutrient analyses made on the sludge in 1988 indicate that nitrogen is the determining constituent in developing a sludge application rate. Among the nutrients in the sludge, nitrogen is the most mobile and must be properly managed to minimize leaching as nitrate. Since only a portion of organic nitrogen in the sludge is available to the plant during the year it is applied, the objective is to match the plant-available nitrogen in the sludge to the crop's annual nitrogen requirement. Based on the estimated net available nitrogen in the sludge, 35 pounds/tons, the annual crop nutrient and sludge loadings for the crops currently grown by K & L Farms (plus corn) are shown in Table 8. Tables 9 and 10 of the Report show the sludge loading rates for a typical crop rotation and the projected sludge production and required acreage for disposal . Concentrations of metals in the sludge and cumulative loadings limits allowed by the EPA were used to determine the allowable annual metal and sludge loadings for a site life of 20 years (see Table 10 of the Report. From the above information, zinc was determined to have the limiting loading rate for metals which would restrict the average annual sludge loading rate to a maximum of 18 dry tons/ acre. However, this loading rate is less restrictive than the nitrogen loading rate which the loading limits of 2.1 to 11 dry tons/acre based on crop nitrogen requirements. Records of sludge application to each field will be kept and ongoing monitoring of sludge quality will be conducted to ensure that the annual and cumulative loading limits are not exceeded. SITE OPERATIONS PLAN Since one objective was to demonstrate the value of sludge as a resource to farmers, the City proposes to integrate sludge application into the K & L Farms cropping system with a minimum of new operational constraints. Crop selection and management have been adjusted to meet Department of Health Services regulations and guidelines. The Plan states that the crops will be fertilized with sludge and chemical fertilizers and irrigated to meet crop needs. Irrigation runoff from the sludge application site as well as the entire farm is captured and recycled. The Report states that the runoff control is an important means for water conservation for the farm operation and should protect the San Joaquin River water quality from site runoff. The Report states that K & L Farms will be responsible for the management and operation of the farming efforts while the City will be responsible for sludge transport,