COMPLIANCE INFO_1991-2006 - Laserfiche WebLink

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iR'... ...r.......... a w.rl.aw.v..sA..`w..w.srdmeW.w'..•4..J.Li.0✓....�....... .. .. .. , n C SLUDGE CHARACTERIZATION A composite sample of dried,stabilized sludge was also collected on September 8, 1992 and analyzed .for nutrients and total and water soluble metals as outlined in the SAP. ` The results along with allowable levels for metals are summarized in Table 4. The results indicate non-detectable levels of water soluble metals (except copper and zinc) and very low levels of total acid soluble metals in the sludge. This years sludge analysis indicates a more nutrient rich mix with total nitrogen levels of about 2.846%, compared to a 1991 total nitrogen of .85% (Table 4). 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 surprisingly detected in the 1992 sludge at 6.8 mg/kg (chiefly alchlor 1260). The allowable title 22 level for PCB's is 50 mg/kg. Overall the sludge can be considered a non-hazardous solid waste suitable for use as an agricultural amendment. PROPOSED SLUDGE;APPLICATION PROGRAM' w N The City proposes to apply approximately-.586,000. lbs: (dry weight) of air dried sludge on 30 acres in fields 7 and 10. (Based on 1,000:cubic yards of sludge with a dry density of S86 lbs/yard.) This equates to anannual application rate of about 9.8 tons/acre(I 10 lbs.available N/acre)*. Calculations of N loading rates and crop requirements are provided in App endix'A. Sludge,ap plication would occur during-,a 4 to 6 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 SOO lbs:N/acre,or for this sludge,21 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). The recommended crop is alfalfa,selected because of its"high nitrogen demand and high consumptive water use, important-for wastewater application.--Nutrient requirements and consumptive water demand for alfalfa and other crops common to the area are summarized below. 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. AGRONOMIC REQUIREMENTS N P B CONSUMPTIVE REQUIREMENT REQUIREMENT REQUIREMENT WATER USE CROP (lbs/acre) (lbs/acre) (lbs/acre) (inches) Alfalfa 500 90 360 48 Grain Corn 250 100 100 38.5 Silage Corn 250 105 105 27 Wheat 150 60 160 24 Barley 100 60 160 20 - 3 -