COMPLIANCE INFO_1991-2006 - Laserfiche WebLink

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SLUDGE CHARACTERIZATION A composite sample of dried,stabilized sludge was also collected on September 13, 1993 and analyzed by A& L Laboratories for nutrients and total and water soluble metals as outlined in the SAP. These results, along with allowable levels for metals according to the new 503 Rules are summarized in Table 1B. The results indicate non-detectable to very low levels of water soluble metals (STLC) and low levels of total acid soluble metals (TTLC) in the sludge. Levels are well below applicable Title 22 and 503 regulatory limits. This year's sludge analysis indicates a more nutrient rich mix with total nitrogen levels of 3.96 percent, compared to a 1992 total nitrogen of 2.846 percent (Table 2B). Salt levels are moderate in the sludge, but as the sludge is applied to a sandy soil with relatively high irrigation water applications,there is little concern over long-term salt build-up. Low levels of PCB's (EPA 8080)were detected in the 1993 sludge at .43 mg/kg(alchlor 1242). The allowable title 22 level for PCB's is 50 mg/kg. There are no specific regulatory levels for PCB's in the 503 Rules. Overall the sludge can be considered a non-hazardous solid waste suitable for use as an agricultural amendment. PROPOSED SLUDGE APPLICATION PROGRAM The City proposes to apply approximately 856,732 lbs.(dry weight)(or 428.4 tons) of air dried sludge on 31 acres in Field 3. (Based on 1,462 cubic yards of sludge with a dry density of 586 lbs/yard.) This equates to an annual application rate of about 13.8 tons/acre (294 lbs. available N/acre). Calculations of N loading rates and crop requirements are provided in Appendix B. Sludge application would occur during a four to six week period in late October and early November. The sludge would be disced into the surface soil layers within 48 hours of sludge application. The proposed application rate is well within the agronomic requirement of 500 lbs. N/acre, or for this sludge,21.28 tons/acre. Since both total and soluble metal levels in the sludge and soils are relatively low, initial sludge application rates are governed by nutrient levels in the sludge and agronomic crop demand(chiefly nitrogen requirement). Available phosphorous levels in the sludge are moderate and are not the determining factor in the application calculations for this sludge. The recommended crop is alfalfa, selected because of its high nitrogen demand and high consumptive water use, important for wastewater application. Properly managed field corn could also be considered if application rates are reduced about 20 percent. Nutrient requirements and consumptive water demand for alfalfa and other crops common to the area are summarized in Table 3. The agronomic requirement information was supplied by Mr. Mick Canavaria, San Joaquin County U.C. Extension row crop specialist, based on recent research on agricultural land application of wastewater treatment plant sludge completed at U.C. Davis and U.C. Riverside. METALS LOADING ANALYSIS A cumulative metals loading analysis was completed by Montgomery Engineers in the March 1992 Sludge Management Plan Update. Their report indicates extensive remaining capacities for metals with the lowest remaining capacity for copper (78 percent) of about 20 years. Because of the very low levels of metals present in the sludge and the extensive remaining soil capacity, initial screening analyses indicated metals need not be used as a determining factor in the sludge application rate calculations. A Cumulative Pollutant Loading Rate(CPLR) update for metals will be completed and submitted with the Post-Application Report. _ 3 _ 93060PA.RPT