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/ ._44a, 0 a' CENTRAL VALLEY REGIONAL WATER QUALITY CONTROL BOARD INSPECTION REPORT 4 January 1994 DISCHARGER: City of Manteca LOCATION & COUNTY: City of Manteca, San Joaquin County CONTACT(S): Warren Shannon (209) 239-8460 INSPECTION DATE: 13 December 1993 INSPECTED BY: Michael Mosbacher ACCOMPANIED BY: Warren Shannon OBSERVATIONS/COMNTi BENTS: City of Manteca owns 283 acres of farm land adjacent to their waste water treatment plant (WWTP). Approximately 210 acres of the farmland acreage is available for landspreading Manteca's air-dried, anaerobically digested WWTP sludge. The landspread sludge is utilized as a soil amendment for various crops grown in the fields. During the summer growing season, April through October, Manteca also utilizes their WWTP's effluent for irrigation water. In late October we received City of Manteca's sludge pre-application report, requesting approval to spread approximately 428 tons of sludge on Field 3. The sludge loading rate proposed for application to the 31 acres of Field 3, was 13.8 tons per acre and alfalfa was the proposed crop to be planted. According to the Pre-Application Report alfalfa has a nitrogen demand of 500 lbs per acre during the growing season. Manteca's sludge analyses have shown the sludge to have an available nitrogen content of approximately 21.3 lbs per ton. At the proposed application rate (13.8 tons) this equates to 294 lbs of available nitrogen per acre, which is well within the allowable loading for alfalfa(500 lbs/acre). Approval of Manteca's sludge pre-application report was given in early November. At the time of my inspection, sludge had already been spread and tilled-in on Field 3. Mr. Shannon indicated) the actual tonnage applied to Field 3 was more like 17.9 tons per acre. Based on the actual tonnage applied to the field the new available nitrogen will be approximately 381 lbs per acre (21.3 lbs N/ton x 17.9 ton/acre). Also,the actual crop that ended up being planted in field 3 was Red Killion Clover as compared to the alfalfa identified in the Sludge Pre-application report. According to the table entitled Plant Food Utilization by Various Crops found in the Western Fertilizer Handbook, the nitrogen uptake for clover-grass is 300 lbs/acre. Wastewater application may have to be reduced or eliminated during the summer growing season to avoid exceeding the clover's agronomic rate (245 lbs./acre from waste water+ 381 lbs./acre from the sludge = 626 lbs of available N). The San Joaquin Irrigation District Drainage Ditch/Canal runs between and along the north west perimeter of Manteca's fields and appears to flow from south to north. At the time of my inspection the canal had running/standing water. The irrigation district has not been discharging water to the canal since the end of the growing season. Mr. Shannon felt the water in the ditch was probably subsurface field drainage. According to Manteca's Sludge/Wastewater Management Plan surface water run-off from the Manteca fields cannot flow into the canal. As part of this inspection I performed a review of the monitoring files. Based on this review, it appears the storm water runoff/irrigation monitoring results in the Semi-Annual Report (Jan -Jun `93) for the sludge spreading operations are the monitoring results from the San Joaquin River's R-1 and R-2. As of REVIEWED BY: I I