SITE INFORMATION AND CORRESPONDENCE_1985-2004

Home Browse Search

INFORMATION SHEET ORDER NO. R5-2004-0028 ATTACHMENT A CITY OF MANTECA, CITY OF LATHROP AND DUTRA FARMS WASTEWATER QUALITY CONTROL FACILITY SAN JOAQUIN COUNTY 1 Introduction The City of Manteca and City of Lathrop are currently governed by Order No. 5-01-007,NPDES No. CA0081558, adopted 26 January 2001. The City of Manteca has submitted a Report of Waste Discharge for renewal of this Order and for expansion of the wastewater quality control facility (WQCF). The City of Manteca owns and operates the WQCF that receives wastewater flows from the City of Manteca and some areas of the City of Lathrop. The City of Manteca is responsible for the operation and discharge from the treatment plant,while the City of Lathrop is only responsible for its portion of the wastewater collection system. The City of Manteca leases 150 acres of land from Dutra Farms for application of treated wastewater, therefore Dutra Farms is named in this permit and is responsible for the proper application and management of the wastewater on its land. The City of Manteca, City of Lathrop, and Dutra Farms are hereafter Discharger. The City's treatment process consists of raw influent bar screening, flow metering, and grit removal, followed by primary sedimentation,biofiltration, conventional activated sludge and secondary sedimentation. Secondary effluent is spread over agricultural fields and the excess flows are chlorinated, dechlorinated and discharged to the San Joaquin River. The City of Manteca currently discharges an average of 2.0 mgd of treated domestic and industrial wastewater at agronomic rates to 210 acres of farmland owned by the City adjacent to the treatment plant, and 150 additional acres leased by the city with the excess flows discharged to the San Joaquin River. The flows to agricultural land are required to be maximized to limit the discharges to surface waters. Surface water discharges average 4.89 mgd. The treatment system capacity will be expanded through the addition of primary and secondary treatment units that will be similar to and parallel to the existing units. In addition,nitrification, denitrification, tertiary filtration, and UV disinfection will be added to improve the effluent quality. Only the wastewater that will be discharged to the San Joaquin River will receive tertiary filtration and UV disinfection. The expansion will also include additional sludge digestion and dewatering units, as well as improvements to buildings,pump stations,ponds, and chemical handling. Food processing waste will also be delivered, treated, and land applied separately from the municipal waste collection and treatment system. 2 Dilution The City of Manteca utilizes a side-bank outfall on the eastern bank of the San Joaquin River. The flow in the San Joaquin River can be estimated from the Vernalis gaging station which is approximately 15 miles upstream of the Manteca outfall. There are agricultural diversions and returns between the Vernalis station and the outfall,which will affect flow and water quality. Additionally, Brown Sand discharges approximately 10 cfs of wastewater made up of primarily groundwater infiltrate from the Oakwood Lake impoundment just 50 feet downstream via a side-bank outfall on the same side of the San Joaquin River as that of Manteca's outfall.