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: r Emcon 1433 North Market Boulevard •Sacramento California 95834-1;43 . (916)928-3300• Fax(916)928-3341 •J January 29, 1996 Project 0805-114 04 Mr Kyle y e Christie REGEI V EU ARCO Products Company ,SAN 3 01996 P O Box 612530 San Jose, California 95161 ENVIRONMENTAL HEALTH PERMIT / SERVICES Re: Fourth Quarter 1995 Status Report for ARCO Service Station No 2130, Located at 7906 North El Dorado Street, Stockton, California Dear Mr Christie At the request of ARCO Products Company (ARCO), EMCON has conducted an environmental investigation and is currently operating a remediation system at the subject site (see Figure 1) This status report includes information for the fourth quarter of 1995 on subjective and laboratory analysis of groundwater samples collected from each monitoring well, measurements of groundwater elevations m each monitoring well, evaluation of the groundwater gradient, and performance data for the soil vapor extraction (SVE)/air sparge (AS)remediation system. BACKGROUND Environmental work performed at the site has included dnlhng 19 soil borings on site and 5 borings off site Ten vapor extraction wells (VW-1 through VW-10) were installed on site Five groundwater monitoring wells were installed on site (MW-l through MW-5), and five were installed off site (MW-6 through MSV-10). One air sparge well (AS-1) and 3 air sparge monitoring points (MS-1 through MS-3) were installed on site. During construction of well MW-9, cement slurry was accidentall) introduced into the slotted screen The well was destroyed and another boring was drilled near well MW-9 and converted to a monitoring well (MW-10). Well locations are shown on Figure 2 During October 1993, in association with the replacement of the underground storage tanks and product delivery lines, RESNA Industries (RESNA) of Rancho Cordova, California, observed Triangle, Inc., of Sacramento, California, excavate trenches and install horizontal piping for use during site remediation. In June 1994, RESNA prepared and submitted a problem assessment report (PAR) and a final remediation plan (FRP) to the county and state regulatory agencies The reports indicated additional remedial wells were required and should include additional air sparge wells, a monitoring air sparge well, and vapor extraction wells. Residual hydrocarbons were detected in soil to groundwater (approximately 60 feet below ground surface) near the existing tanks, but only relatively low concentrations were detected in soil samples collected from the other on-site borings Gasoline hydrocarbons were not detected in the off-site soil borings. Dissolved SAC1N TW805s08051140 4GS-95\pn i