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1.0 INTRODUCTION This Interim Remedial Action Work Plan (IRAP) outlines proposed interim remedial action activities to be conducted at the Site known as Joe's Place, located at 15600 South Harlan Road, Lathrop, California(Figure 1). The Site is identified by the San Joaquin County Environmental Health Department local oversight program(LOP) #231585. The Environmental Remediation Group (ERG) is currently collecting data at the Site to evaluate a full-scale system for remediation and to more completely define the lateral and vertical extent of hydrocarbon impact. A Workplan for additional assessment was submitted to the San Joaquin County Environmental Health Department(SJCEHD) on October 23, 2006. As data is collected and evaluated, ERG plans to implement an interim remedial system to mitigate further migration of the methyl-tertiary-butyl ether (MTBE) groundwater plume. This IRAP summarizes the Site setting, site assessment activities,and proposed interim remediation activities. 2.0 SITE SETTING The Site known as Joe's Place is an active service station located south of J Street along South Harlan Road in Lathrop, California(Figure 1 and Figure 2). The Site is bordered to the north by a storage facility and to the east by residences. The west is bordered by Interstate 5 and a vacant lot lies to the south of the property. The Site is currently configured with four automobile fuel dispenser islands, seven fuel dispenser islands for large trucks, four 10,000-gallon diesel fuel aboveground storage tanks (ASTs), one 4,000-gallon diesel fuel underground storage tank(UST), and three gasoline USTs with capacities of 12,000, 10,000, and 4,000 gallons. 2.1 Site Geology and Hydrogeology Previous subsurface investigations indicate that the soil beneath the Site consists of fine-grained soils with three laterally extensive sand strata known as Sand A, Sand B, and Sand C. Sand A begins 5 to 8 feet below ground surface(bgs) and is 3- to 10-feet thick. Sand B begins between 25 to 35 feet bgs and is between 7-to 18-feet thick. Sand C begins between 50 and 65 feet bgs and is between 15-to 25-feet thick. Groundwater is present in each of the three sand layers and is first noted at a depth of 9 to 10 feet bgs.. Monitoring wells MWO-1X and MW-8 are screened in Sand B and all other wells are screened in Sand A. Groundwater flow direction is towards the northeast at a gradient of 0.00075 ft/ft(Figure 3). The pump test results and vertical distribution of contaminants indicate that there is interconnectivity between Sand A and Sand B. 2.2 Contaminants of Concern MTBE is the primary contaminant of concern (COC) in groundwater at the Site. MTBE is a highly soluble compound that does not adsorb well to soil. MTBE is migrating off site to the northeast in the direction of the groundwater gradient. The lateral extent of dissolved MTBE has not been fully characterized. Relatively low concentrations of MTBE have also been detected in MWO-IX and MW-8,the only ERG,0406 Page I IRAP