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s Fr `t QUARnmLY GnouNDWATEA motif rMNG PEP= 1605 Louth EI Aorada,StccKon,Callfornla - 1.0 INTRODUCTION 1" This report documents the results of the first quarterly groundwater monitoring conducted by Aegis Environmental,Inc. (Aegis),on October 17, 1991,at the Exxon Company. U.S.A. (Exxon),service station located at 1605 South EI Dorado In Stockton, California(Figure 1). The monitoring included collection of depth-to-groundwater measurements and water samples from the three wells, MW-1, MW-2, and MW-3, located on site (Figure 2). This report is based, in part, on information obtained by Aegis from Exxon, and is subject to modification as newly acquired inforrna6cin may warrant. rig 2.0 SITE DESCRIPTION i a The subject site is located between South EI Dorado Avenue and Center Street in the City i of Stockton, San Joaquin County, California (Figure 1). The site is situated in a 6� commercial/residential/light industrial area of southern Stockton. The site is bound on the north by East 2nd Street, on the east by South El Dorado Avenue, on the south by a car wash facility, and on the west by Center Street. l ; The Exxon service station is presently an active station. The store retails regular-leaded, regular-unleaded, and extra-unleaded gasolines. The station facilities include a building, three dispenser islands, and three underground storage tanks (UST) with associated product piping. The three UST are located immediately south of the dispenser islands on the southern half of th site. The type of construction and the installation dates of the UST are unknown. Figure 2 shows the location of the site's above-ground and i underground features. t ( »: 3.0 BACKGROUND On February 5, 1991, a ground penetrating radar (GPR) survey was performed by NORCAI_ Geophysical Consultants, Inc., of Petaluma, California. The survey was performed in the area of the existing UST basin to locate existing underground facilities -! for avoidance during drilling. Upon completion of the GPR survey, two soil borings were drilled on February 22, 1990, at an angle of 30 degrees from vertical, adjacent to the .j existing.UST basin (Figure 2). The borings were advanced Using an 8-inch-diameter hollow-stern auger. A total of 60 feet of auger was utilized in each boring, with a final sample drive of 18 inches achieving a total depth of 61.5 feet along the 30-degree angle. The actual vertical depth penetrated by the borings was approximately 53 feet below existing grade. Soil samples collected from the two soil borings were analyzed for total r petroleum hydrocarbons (TPH), as gasoline, benzene, toluene, athylbenzene, total I l xylenes(BTEX),ethylene dibromide,1,2-dichloroethane,and total lead. Results of the soil _ boring and sampling were reported by Aegis to Exxon, in a"Pre-Tank Replacement Site - -- s - Assessment-Results-Report, dated March-5;-1991 --- -------- - ---------- tl �i 9t-044CAPT