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SECOND QUARTERLY GROUNDWATER MONfTCHNG REPORr OF 1992 1605 South EI Dorado Street Stockton Caktornla 1.0 INTRODUCTION This report documents the results of the second quarterly groundwater monitoring for 1992 conducted by Aegis Environmental, Inc (Aegis), at the Exxon Company, U S A (Exxon), inactive service station located at 1605 South El Dorado Street in Stockton, California (Figure 1) The monitoring included collection of monthly depth-to-groundwater measurements and quarterly groundwater 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 2 0 SITE DESCRIPTION I The subject site is located between South El Dorado and Center Streets in the City of Stockton, San Joaquin County, California (Figure 1) The site is situated in a commercial/residential/light industrial area of southern Stockton The site is bounded on the north by East 2nd Street, on the east by South EI Dorado Street, on the south by a car wash facility, and on the west by Center Street The Exxon site is an inactive service station that previously retailed leaded and unleaded gasohnes The station's current facilities include a building and three inactive underground storage tanks (UST) with associated product piping The three UST are located immediately south of the dispenser islands on the southern half of the site The type of construction and installation dates of the UST are unknown Figure 2 shows the location of the site's aboveground and underground features I 30 BACKGROUND On February 5, 1991, a ground penetrating radar (GPR) surrey was performed by NORCAL Geophysical Consultants, Inc , of Petaluma, California The survey was I 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 I existing UST basin (Figure 2) The actual vertical depth penetrated by the borings was approximately 53 feet below surface Soil samples collected from the two borings were analyzed for total petroleum hydrocarbons (TPH), as gasoline, benzene, toluene, ethylbenzene,total 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 Assessment Results Report," dated March 5, 1991 1 I 91-044A QMR 1 I