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F 4 Stantec Vin/ SECOND QUARTER 2009 OPERATIONS MAINTENANCE AND MONITORING REPORT SHOP 10 MAINTENANCE STATION Introduction �. July 31, 2009 �. 1.0 Introduction V This report has been prepared by Stantec Consulting Corporation (Stantec)to present the results of the Second Quarter 2009 groundwater monitoring and air sparge/soil vapor extraction treatment system r (ASISVETS) operation at the Caltrans Shop 10 Maintenance Station located at 1603 South B Street in Stockton, California. The work was performed in general conformance with the Stantec work plan entitled, "Air Sparge/Soil Vapor Extraction Treatment System (AS/SUETS) Installation, Quarterly Groundwater Monitoring and Reporting, Caltrans Shop 10 Maintenance Station, 1603 South B Street in Stockton, California,"dated May 24, 2005, (Work Plan) and the most current health and safety plan (HASP). This report was prepared in accordance with Caltrans Contract 06AI361, Task Order No. �. 06A 1361-02. 1.1 PROJECT LOCATION AND HISTORY The Caltrans Shop 10 Maintenance Station (the Site) is located at 1603 South B Street adjacent to the a� District Office located at 1976 E Charter Way at the corner of Charter Way and B Street in the City of Stockton, California (Figure 1). The Site occupies approximately four acres including a two-story office building and temporary permit building, parts warehouse, and maintenance shop (Shop 10). Outside V areas for truck washing and water treatment, machining, and highway maintenance equipment storage exist in the southwestern portion of the property (Figure 2). Several underground storage tanks (USTs) �. were previously removed and monitoring wells have been installed and are currently in use at the Site to monitor groundwater quality. The property is owned by Caltrans and is used for the storage and maintenance of state vehicles and highway maintenance equipment. In 1978, one 5,000-gallon UST with unknown contents was reportedly removed from the Site due to a detected leak. In 1989, three 5,000-gallon gasoline USTs, one 5,000-gallon diesel UST, and one 1,000- gallon waste oil UST were removed from the Site. Between 1987 and 1996, 25 groundwater monitoring wells and 2 vapor extraction wells (VM-1 and VM-2) were installed at the Site to assess the vertical and lateral extent of contamination. Thirteen of the monitoring wells were destroyed and the remaining twelve �.• groundwater wells are currently included in the groundwater monitoring program. The Site has been on a quarterly groundwater monitoring schedule since 1990 and will continue on a semi-annual basis with the next sampling event occurring in December 2009. The groundwater flow direction beneath the Site varies �. from northeast to southeast. Remedial action was required by the San Joaquin County Environmental Health Department(SJCEHD) to clean up residual soil-and groundwater-impacted areas remaining after UST removal and limited over- excavation per a Remedial Action Plan (RAP) prepared in 1992. Construction of an ASISVETS was completed and initial startup occurred December 1, 2005. V V js k%usl329-f011secorYproject-051caltranslstockton-shop 101om8m and gw reporling5200%2nd qtr 2009%g2_09 omm_lnl,doe 1-1