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MONITORING WELL INSTALLATION WORKPLAN City of Stockton Regional Wastewater Control Facility 2500 Navy Drive Stockton,California 1.0 INTRODUCTION In December 2003, sixteen groundwater monitoring wells were installed at the City of Stockton Regional Wastewater Control Facility (RWCF) located at 2500 Navy Drive (Site) in Stockton, California (Figures 1 and 2, Appendix A). The wells were installed in compliance with Waste Discharge Requirements (WDR) Monitoring and Reporting Program (MRP) Order No. R5-2002-0083 issued by the Central Valley Regional Water Quality Control Board(Regional Board) dated April 26,2002.The MRP required commencement of quarterly groundwater monitoring and, after one year's collection of data, an evaluation to determine if the RWCF operations and pond storage is adversely impacting groundwater and if additional monitoring wells are needed. This work plan was prepared by Condor Earth Technologies, Inc. (Condor) at the request of Stephen Gittings of the City of Stockton, Municipal Utilities Department, to propose the construction of two additional monitoring wells based on evaluation of data from the existing monitoring wells. All work conducted by Condor will be under the supervision of a Registered Engineer in the State of California. This work plan includes project background information; a description of the field, laboratory, and reporting procedures proposed to conduct the work; and a project schedule. 2.0 PROJECT BACKGROUND The study area consists of the Stockton RWCF main (i.e. secondary) treatment plant located on Nary Drive, and the tertiary treatment plant and oxidation ponds located west of the San Joaquin River. In December 2003, Geotechnical Consultants, Inc. (GTC) completed sixteen monitoring wells (MW-1 through MW-16) at the Site to monitor the potential impact on groundwater by RWCF operations and evaluate compliance with the City of Stockton's Discharge Permit. Monitoring well installation and development details for MW-1 through MW-16 are provided in GTC's "Well Installation Report, Stockton Regional Wastewater Control Facility, Stockton, Calif.", dated January 2004. GTC conducted quarterly groundwater monitoring of the Site from the Fourth Quarter 2003 through the Third Quarter 2004. GTC concluded that groundwater quality at the perimeter of the RWCF was not significantly degraded compared to the background water quality, although groundwater quality was not of acceptable quality for domestic,municipal, or agricultural use. GTC recommended the following: • That the monitoring program should be modified to eliminate or relocate MW4 because it does not provide a representative groundwater sample. • Construction of one new down gradient well east of the Secondary Treatment Plant to characterize nitrate migration in this area. • The sampling frequency should be modified to twice per year because no significant water quality impacts or temporal trends were observed. Condor began conducting quarterly groundwater monitoring at the Site during the Fourth Quarter 2004.