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i 1.0 INTRODUCTION On behalf of the San Joaquin Count Facilities Management Department, Ramage q Y 9 Environmental has prepared this First Quarter 9999 Groundwater Monitonng Report, for submittal to the San Joaquin County Public Health Services Environmental Health Division (PHSIEHD) and the Central Valley Regional Water Quality Control Board (RWQCB) The Project scope of work was completed in accordance with Ramage Environmental's Work Plan, Monitoring Well Installation and Quarterly Groundwater Monitoring, dated July 1, 1998 1.1 Site Description The Agricultural Commissioner's Office site is located at 503 East 10th Street in the city of Tracy (San Joaquin County), California (Figure 1) The property is an active county office building The site is bordered to the north by Hamilton Alley, a city of Tracy right-of-way, and to the east by a transmission repair shop on private property (Figure 2) The site is flat and mostly paved Three 1,000-gallon ca acit , underground storage tanks (UST) existed in the northeast part of p Y 9 g �. the site The northernmost and southernmost USTs (Tanks 1 and 3) were used to store weed oil (i e , high-sulfur diesel fuel) The center UST was used to store unleaded gasoline 1.2 Previous Work On October 28, 1988, the three 1,000-gallon capacity, USTs and associated product piping and dispenser island equipment were removed from the site by Tilford & Hall During UST removal, the PHSIEHD inspector noted the presence of holes in both weed oil USTs and "extensive contamination" within the limits of the excavation One soil sample was collected from beneath each UST at a depth of 9 to 10 feet below ground surface (bgs) and analyzed for Total Extractable Petroleum Hydrocarbons (TEPH), Total Volatile Petroleum Hydrocarbons (NPH), benzene, toluene, ethylbenzene and xylenes (BTEX), ethylene dibromide and total lead by Canonie Environmental Services Corporation Laboratory results indicated that concentrations of petroleum hydrocarbons were detected in all three soil samples Concentrations of petroleum hydrocarbons included 760 parts per million (ppm) NPH beneath the center UST (Tank 2), 4,700 ppm TEPH from beneath the northern weed oil UST (Tank 1) and 4,800 ppm TEPH from beneath the southern weed oil UST (Tank 3) 3