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i t STATE OF CALIFORNIA—ENVIRONMENTAL POACTION AGENCY PETE WILSON Govemor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— CENTRAL VALLEY REGION °gg 3443 ROUTIER ROAD,SUITE A B SACRAMENTO,CA 95827-3098 M PHONE: (916)255-300036 FAX: (916)255-3015 r- 3 January 1996 Mr. Jim Podesta Deputy Director of Public Works City of Manteca 1001 W. Center St. Manteca,CA 95337 SLUDGE PRE-APPLICATION REPORT FOR BIOSOLIL._ �.,ri.ii ATION TO LAND ADJACENT THE MANTECA WATER QUALITY CONTROL FACILITY (WQCF), SAN JOAQUIN COUNTY We have reviewed your latest Sludge Pre-Application Report dated 7 December 1995. Your proposed rate of biosolids is approved. Manteca's Waste Discharge Requirements Order No. 91-110(WDRs)Effluent Limitation B.2 states the following: B.2 The Discharger shall maximize disposal of effluent to land at agronomic rates at all times. If Manteca's WQCF discharges treated effluent to the river rather than to land because nitrogen requirements of the crops are being met from sludge spreading,then this would be a violation Effluent Limitation B.2. Alternative methods for disposal or use of the sludge exist. In order for us to determine whether Manteca is maximizing its disposal of effluent to land at agronomic rates, we request Manteca submit for our review and approval a Nitrogen Management Plan for the coming growing season. The Plan must indicate the maximum volume of effluent that can be applied to each field and not exceed the agronomic requirements of the crop in the field. The effluent volume to each field must be based upon nitrogen available in the effluent,the type of crop raised, available nitrogen from sludge applications,and any nitrogen fertilizers applied by the farmer. The Nitrogen Management Plan must be submitted to us for review by 1 March 1996. Manteca has proposed relatively high nitrogen application rates by: 1)estimating that the yield for alfalfa and corn from Manteca's fields are 25% above the average yields per acre identified by the Western Fertilizer Handbook(27 November 1995 letter)and 2)double cropping the fields and requesting full nitrogen use rates based on a single annual crop (7 December 1995 letter). Given the existing high nitrate concentrations in the ground water beneath the application fields,the relatively shallow ground water,and the porous soil conditions, we are very concerned about potential for over application of nitrogen. Manteca apparently has no crop yield data to justify an increase in nitrogen use rates above the average listed in the Western Fertilizer Handbook,so we will not approve any applications based upon above-average crop yields. Due to late planting, early harvest,etc.,double cropping fields may result in lower crop yields for each crop than if the crop was grown as the only crop on the land, although the overall productivity of the land(and nitrogen usage)may be higher due to the double cropping.