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Technical Memorandum Stockton Delta Water Supply Project Well Demolition an • Sanitary System Approval To: Tim O'Brien, California Central Valley Regional Water Quality Control Board From: Greg Lindstadt, P.E. Date: August 20, 2010 INTRODUCTION The City of Stockton's Delta Water Supply Project Water Treatment Plant(DWSP WTP)located at 11373 N. Lower Sacramento Road,Lodi,CA has been the topic of previous memos, addressing the solids settling and drying basins and existing groundwater quality. On July 27,2010,The California Central Valley Regional Water Quality Control Board (CVRWQCB)issued a letter with the determination that the small amount of wastewater that may be discharged from these basins is unlikely to affect the groundwater quality. This memorandum provides information on existing wells at the site that must be appropriately abandoned and demolished to make way for new facilities. This memorandum also provides information on the anticipated sanitary wastes to the planned on-site septic tank and leachfield system. This information was requested by the CVRWQCB to assist in confirming the appropriate review and approval of the well abandonment and sanitary system. DESCRIPTION OF FACILITIES Attached Figure 1 provides an overview of the new WTP site. Indicated on this figure are the locations of three existing wells that require abandonment, and the location of the planned septic tank and leachfield facilities. Wells There are three existing wells that require abandonment and demolition to protect the groundwater and make way for construction of WTP facilities. A brief description of each well follows. Monitorina Well The monitoring well is a piezometer well remaining from the geotechnical investigations.This piezometer well was drilled to a depth of 82 feet and constructed with a 2-inch casing. This monitoring well was developed to remove fine silt from the well bore and filter pack and increase the hydraulic radius,and was used to sample groundwater quality for the anti-degradation analysis. The monitoring well development report,with field logs,was provided to the CVRWQCB for reference as part of the anti-degradation analysis.