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' MEDIATION TESTING ST NG AND DESIGN March 29 , 1993 -INTRODUCTION ' At the request of Ultramar, Inc (Ultramar ) , Remediation Testing and Design (RTD ) conducted limited soil gas screening (LSGS ,' and vacuum ' extraction feasibility testing (VEFT ) on March 17 and 18 , 1993 , at the former Beacon Station # 494 located at 2385 East Fremont Street in Stockton, California. Figure 1 shows the general location of the site The testing was conducted to evaluate the shallow nydrocarbon ' .impacts located near the former underground storage tanks (USTs ) and to determine the effectiveness of using vacuum extraction as a remediation option for soils This report includes a brief ' description of the sub3ect site and presents, the procedures , results , and conclusions of the field testing BACKGROUND The site is located in the Central. Valley approximately 10 males east ' of the San Francisco Bay Delta The city of Stockton is a shipping port and serves local agricultural activities . Surface elevation at the site is approximately 20 feet above mean sea level The Calavaras River lies two miles to the north and the San Joaquin River lies thiee miles to the east of the site. The subDect property formerly contained three ten thousand gallon USTs Previous environmental investigations indicated gasoline impacts to soil and groundwater Depth to groundwater at the site is approximately 75 feet belot* grade Groundwater elevations measured at the site indicate a general flow direction to the northwest The stratigraphy at the site generally consists of silts and clays with localized sandy units These sandy units generally occur from 30 to ' 35, 50 to 57 and 64 to 69 feet below grade The vacuum extraction wells at the site are screened opposite these more transmissive sandy zones PROCEDURES Soil Gas Screening A LSGS was conducted using nine vapor probes installed for the investigation, four existing monitor wells , and eight existing vapor recovery wells In ' order to install the vapor probes , a permit front San Joaquin County Public Health Services , Environmental Health Division (PHS/EHD) was obtained by RTD on the behalf of Ultramar A copy of the permit and all regulatory correspondence is contained in Appendix, A. Figure 2 is a detailed site plan showing the location of all probes and wells The vapor probes are constructed of 3/4-inch diameter, schedule-80 , carb,_n steel pipe Each probe contains a 36- inch range of drilled perforations at ,one end with a forged drive point All probes were s-.eam cleaned prior to transport to the site The probes were installed using a pneumatic drive hammez to total. ' depths ranging from 13 to 1' feet below grade. Probe locations were 1 1