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WORD PLAN FOR GROUNDWATER EXTRACTION PILOT TEST VALLEY MOTORS 800 East Main Street Stockton, California 1.0 INTRODUCTION Investigation of soil and groundwater contamination at 800 East Main Street(Figure 1) began in 1994,when several borings were drilled to collect soil samples for laboratory analysis of petroleum-range hydrocarbons. Further drilling took place in 1995,and.again in 1996, 1998, 1999, and 2003.At the completion of that work,eight groundwater monitoring wells,one vapor extraction well,one air sparging well,and numerous soil borings and vapor probes had been installed(Figure 2). The results of the investigation were subsequently summarized in a Problem Assessment Report and Foil Remediation f Plan that was prepared in October 2003 and submitted to the San Joaquin County Environmental Health'Department(SJCEHD). A thermal oxidation vapor extraction system was installed at the site in mid-2005,and soil remediation began in December of that year. The remediation system operated until. November 2006,when it was shut down for reasons of cost effectiveness. If further soil remediation was deemed necessary by SJCEHD,Upgradient Environmental recommended removing the vapor extraction unit and replacing it with a regenerative blower and granulated activated carbon canisters for vapor destruction:. Upgradient also recommended that a groundwater extraction test be conducted to determine whether significant reduction in groundwater,contaminant levels could be attained. In subsequent correspondence, SJCEHD indicated that it would consider a proposal to conduct a groundwater,extraction test,but requested'that multiple methods of groundwater extraction be evaluated and submitted to Mr.Infurnas' attention. Two potential methods._ of groundwater treatment were submitted on January 25 in a report entitled Groundwater Remediation Feasibility Sturdy. In a response dated February 8, SJCEHD directed Valley Motors to submit a Work Plan to test the feasibility groundwater extraction 2.0 EXTRACTION WELL INSTALLATION In the feasibility study,Upgradient indicated that two 6-inch extraction wells would probably be sufficient for either of the potential methods of groundwater remediation. ! VM-9 and VM-10 wells will be constructed of 6-inch diameter PVC and screened from 38 to 53 feet.'The wells will.be installed using a hollow-stem auger drilling rig and construction details are presented in Figure 3. Soil samples will be obtained at 5-.foot intervals and screened using a PID. A minimum of two soil samples will be submitted for laboratory analysis. Boring logs will he prepared and submitted with the pilot test ' report. Drill cuttings will be stored in drums on site. Upon completion,the.drums will be transported to a disposal facility. i . 1