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' GROUNDWATER WELL DESTRUCTION AND ' REPLACEMENT WELL INSTALLATION WORK PLAN FOR THE CITY OF MANTECA WASTEWATER ' QUALITY CONTROL FACILITY San Joaquin County,California 1.0 INTRODUCTION ' This Work Plan has been prepared for the abandonment of MW-9E and the installation of a new groundwater monitor well MW-11 at the City of Manteca's Wastewater Quality Control Facility (Facility) located approximately 1 mile west-southwest of the town of Manteca (Figure 1). The Work Plan was prepared by Condor Earth Technologies, Inc. (Condor) at the request of the City of Manteca, Public Works Department(the City). ' The activities described in this Work Plan will facilitate and enhance the Facility's performance of the evaluations required by Provision 8 of the Waste Discharge Requirements (WDRs) Board Order No. R5- 2004-0028 issued by the Central Valley Regional Water Quality Control Board (Regional Board) dated ' 19 March 2004. The primary objective of the work described in this Work Plan is to facilitate farming activities by removing well MW-9E from an active field, and to replace it with a new monitor well on a nearby access road. This Work Plan includes a description of the proposed fieldwork, laboratory analyses, report preparation, and project schedule. The work described in this Work Plan will be conducted under the direct ' supervision of a California Professional Geologist. 2.0 SITE BACKGROUND INFORMATION The City owns and operates a wastewater treatment facility that receives wastewater from the city of Manteca and from a portion of the city of Lathrop. Treated effluent from the facility is either discharged to the San Joaquin River or applied at agronomic rates to land adjacent to the wastewater treatment plant. ' The land application area is approximately 172 acres. Six monitor wells located within and/or downgradient of the land application area have been installed to monitor groundwater quality. One of the wells (MW-9E) is to be destroyed and a new well MW-11 installed in its place. The layout of the ' treatment plant, land application facility,and the monitor wells is shown on Figures 1 and 2. 3.0 GEOLOGY AND GROUNDWATER ' The Facility is located in California's Great Central Valley physiographic province. The valley is filled with Tertiary and Quaternary clastic sediments to depths of greater than 20,000 feet. The Facility is directly underlain by alluvial sediments mapped as the Quaternary Modesto Formation (California Division of Mines and Geology Regional Geologic Map of the San Francisco-San Jose Quadrangle — Map No. 5A published in 1991). The ground surface at the project site ranges from 20 to 25 feet above mean sea level and is generally flat with a slight slope towards the west. The San Joaquin River is a gaining stream and is located approximately 10,000 feet to the west of the Facility. The river flows generally from the south to the north. CONDOR