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California R#ional Water Quality Pontrol Board ;_ ' '-h Central Valley Region Steven T.Butler,Chair Winston H. Gray Davis Secretaryfor og Sacramento Main Office Governor Environmental Internet Address: http://www,swrcb.ca.gov/—mgcb5 Protection - 3443 Routier Road,Suite A,Sacramento,Califomia 95827-3003 Phone(916)255-3000•FAX(916)255-3015 18 July 2000 Mr. Jon Crawford City of Lathrop Public Works Director 16775 Howland Road, Suite One Lathrop, CA 95330 INCOMPLETE REPORT OF WASTE DISCHARGE, PROPOSED WASTEWATER - EVAPORATIONITERCOLA TION PONDS AT CROSSROADS TREATMENT PLANT, SCJ JOAQUIN COUNTY I have reviewed the 28 April 2000 "Summary Report, Geotechnical and Geologic Investigatioxs, "- prepared by Neil O. Anderson &Associates, and the May 2000 "Preliminary Wastewater Inj'&ation-� Ponds and Groundwater Subdrain Design,"prepared by Gary Litton and Siegfried Engineering. The'J reports were prepared as part of a Report of Waste Discharge (RWD) to describe a proposed plan to relocate the existing wastewater evaporation/percolation ponds from their present location to a site approximately 1,500 yards west. The relocation was evaluated as a response to poor percolation rates at the existing ponds. Six hydrologic conditions were evaluated in the reports. All of the conditions require dewatering groundwater beneath the proposed ponds to maintain a five-foot separation between the pond bottoms and the groundwater table. Dewatering flow rates would vary from approximately 0.72 million gallons per day(mgd) to 2.88 mgd. The dewatering activities would capture all of the wastewater percolating into the subsurface plus additional groundwater. The pumped water would then be discharged to the San Joaquin River without additional treatment. However, discharges to surface water require National Pollutant Discharge Elimination System(NPDES)permits and the RWD is determined to be incomplete because the selected alternative allows for wastewater to be discharged to surface waters. This condition results in your proposed wastewater discharge being considered a surface water discharge subject to the NPDES permit requirements. Considering the water quality impairments of the San Joaquin River, obtaining a NPDES permit for your wastewater discharge would be a difficult process due to the wasteload allocations which must be completed to address the impairments. hi addition, Lathrop would probably be required to significantly upgrade the treatment provided. Mr. Gary Litton requested criteria that could be used in evaluating alternate locations for wastewater evaporation/percolation ponds, especially with regard to discharge of"renovated groundwater"to surface water bodies. For permitting purposes, the discharge of water will be considered wastewater if it contains statistically significant concentrations of wastewater constituents. All wastewater constituents, California Environmental Protection Agency Co Recycled Paper