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' 1.0 INTRODUCTION This Work Plan has been prepared at the request of Mr Craig Ogata, Director of Facilities Management, for the County of San Joaquin under Purchase Order No 148-440690-1 The proposed scope of work includes environmental site investigation tasks, as reviewed with the San Joaquin County Public Health Services Environmental Health Division (PHS-EHD) 1 1 Site and Subsurface Description The site is located at 392 South Moffat Boulevard in the city of Manteca (San Joaquin County), ' California (Figure 1) The property Is an active agricultural commissioner's office Three, 1,000- gallon capacity, underground fuel storage tanks (UST) existed in the southeast portion of the site ' (Figure 2) The northern and southern former USTs (Tanks 1 and 3)were used to store weed oil (I e , diesel fuel) The center UST (Tank 2) was used to store unleaded gasoline ' The site is flat and at an elevation of approximately 35 feet above mean sea level During UST removal, the PHS-EHD inspector noted that sod encountered during excavation was sandy to a depth of 10 feet below ground surface (bgs) The excavation did not encounter free groundwater As in wells from nearby sites, first groundwater at the subject site is likely present at a depth of approximately 15 feet bgs 12 Previous Work ' On November 1, 1988, three (3), 1,000-gallon capacity, USTs and associated product piping and dispenser island equipment were removed from the site by Telford & Hall During UST ' removal, the PHS-EHD inspector noted the presence of corrosion and holes in all three tanks and "prevalent odor" during excavation of the northern weed oil tank ' One soil sample was collected from beneath each UST at a depth of 10 to 10 5 feet bgs and analyzed for Total Extractable Petroleum Hydrocarbons (TEPH), Total Volatile Petroleum ' Hydrocarbons (NPH), and benzene, toluene, ethylbenzene and xylenes (BTEX) by Canonie Environmental Services Corporation Laboratory results indicated that concentrations of ' petroleum hydrocarbons were detected In soil samples collected from beneath the northern and central USTs Concentrations of petroleum hydrocarbons Included 9,900 parts per million (ppm) TEPH beneath the northern weed oil UST and 18 ppm NPH from beneath the central gasolene ' UST Petroleum hydrocarbons were not detected in the soil sample collected from beneath the southern weed oil UST Work Plan,Environmental Site Investigation Ramage Environmental 392 South Moffat Blvd,Manteca California June 18 1997 2