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1 JAMES M. MONTGOMERY, CONSULTING ENGINEERS, INC. TECHNICAL MEMORANDUM CITY OF MANTECA WASTEWATERUALITY CONTROL FACILITY Q C Y SLUDGE MANAGEMENT PLAN UPDATE Subject: Sludge Management Plan Date: March 31, 1992 Prepared by: Ramesh Babu File No.: 912.0420 Reviewed by: Keith Conarroe PURPOSE The purpose of this technical memorandum (TM) is to reevaluate the City of Manteca's (City) sludge management plan in accordance with Item 6 of the City's Waste Discharge Requirement Order No. 91-110. The TM presents the sludge production data, sludge characteristics, description of sludge disposal operations, and a sludge monitoring program. Effluent nitrogen and metals loading rates on the agricultural land is also discussed. FINDINGS AND CONCLUSIONS A summary of the findings and conclusions of the sludge management plan is presented as follows. • A total of 303 acres is available for effluent disposal. Of the total acreage,only about 210 acres is available for sludge disposal. A local farmer utilizes the land to cultivate barley, corn and alfalfa. • Based on historical data,nitrogen loads from sludge application is substantially below crop nitrogen uptake requirements. Therefore, land application of sludge is within agronomic rates. • The nitrogen contribution from the effluent exceeds the crop nitrogen requirements. Therefore, land application of effluent should be reduced to maintain a balance with crop nitrogen requirements. An annual nitrogen balance would assist in determining the amount of effluent that can be land applied in the following year. • Based upon sludge and effluent application beginning in 1984, copper is the limiting metal in determining the capacity of existing land for sludge disposal. Comparison of applied copper loads with EPA's cumulative pollutant loading rates, indicates that 78 percent of the land's copper assimulative capacity is available for future sludge and effluent application.