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I EC®n Associates 1433 North Market Boulevard • Sacramento California 95834 1943 • (916)928-3300• Fax(916)928-3341 April 27, 1995 Project 0805-140 02 Mr Kyle Christie ARCO Products Company 1 ,g 5 P O Box 5811 San Mateo, California 94402 Re First Quarter 1995 Status Report for ARCO Service Station No 0548 at 1 1612 Hammer Lane, Stockton, California r Dear Mr Christie At the request of ARCO Products Company (ARCO), EMCON is conducting an environmental investigation at the subject site (see Figure 1) We have prepared this status report on the work conducted during the first quarter 1995, which included measuring depth to groundwater, collecting groundwater samples from the wells for subjective and laboratory analyses, and calculating the groundwater gradient and direction of groundwater flow beneath the site BACKGROUND From December 1990 through November 1993, RESNA Industries ([RESNA] formerly Applied GeoSystems) observed the drilling of 21 borings (B-1 through B-21) and the installation of 5 on-site groundwater monitoring wells (MW-1 through MW-5), 1 off-site groundwater monitoring well (MW-6), and 4 vapor extraction wells (VW-1 through VW-4) (RESNA, June 26, 1992, Report 30004-4, RESNA, June 21, 1993, Report 30004-8, and RESNA, May 11, 1994, Report 30004-8) The locations of soul borings, wells, and other site features are presented in Figure 2 Residual hydrocarbons were analytically identified in soul samples collected from the borings near the tank cavity Low concentrations of hydrocarbons were detected in soli samples collected from borings near the dispenser islands During drilling of soil boring B-18, a product line was accidentally fractured and product leaked into adjacent soil RESNA collected a soil sample from 6 feet below the product line (S-6-PL1), gasoline hydrocarbons were detected in this sample RESNA began monitoring the groundwater in wells MW-1 through MW-4 on October 30, 1991 (RESNA, June 26, 1991, Report 30004-4) Well MW-5 was added to I the monitoring program in March 1993 Dissolved hydrocarbons have been detected in monitoring wells MW-I and MW-5 since monitoring began In March 1992, EA Engineering, Science and Technology (EA) observed removal of the oil-water separator/clarifier (EA, August 1992, Report 80633 01) EA collected one soil sample from beneath the former oil-water separator and one sample from the concrete Analytical results from the soil samples indicated that oil and grease (quantified as total oil SAON 1PJON0805108051400 2AL-941drm n