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BeBrown and Caldwell _ Consultants ~ r 723 S.Street n q Sacramento MAA Calrfomia 95814 7092 (916)444-0123 FAX(916)4448437 P IMI!I /b ►�Y�GE: March 26, 1993 f Mr Chuck Carmel ARCO Products Company Post Office Box 5811 San Mateo, Califorrua 94402 017-7403-04/1 Subject. First Quarter 1993 Report for ARCO Station 2093, 3425 Tracy Boulevard, Tracy, California: Pilot Program Site 1416 Dear Mr Carmel This report presents water level measurements and results of groundwater sampling performed during the fust quarter of 1993 at ARCO Products Company (ARCO) Station 2093, located at 3425 Tracy Boulevard in Tracy, CaUforrua Site location is shown on Figure 1. Fieldwork was performed by Emcon Associates on January 18 and 19, 1993 This report was prepared under Task Order 2093-93-5 There are seven on-site wells (ATR-1 through ATR-7) and five off-site wells (ATR-8 through ATR-12), as shown on Figure 2 Four of the on-site wells and all of the off-site wells were sampled. One on-sate well (ATR-3) was not sampled because it contained floating product On-site wells ATR-1 and ATR-2 were not sampled because they ii were inadvertently paved over when the station was recently repaved These wells have since been repaired. Field and Analytical Methods Emcon Associates personnel measured depth-to-water and product thickness (if present), purged each well to be sampled, and collected groundwater samples at the site Depth-to- water measurement and a check for floating product were made prior to commencing purging. Prior to sampling, the wells were purged of a minimum of three well volumes or until evacuated using a centrifugal pump or bailer. After purging, each well was sampled using a Teflon bailer All groundwater samples were analyzed for total petroleum hydrocarbons as gasoline (TPH-G), and for benzene, ethylbenzene, toluene, and xylenes (BETX) by U.S. Environmental Protection Agency (EPA) Method 5030/8020/DHS LUFT Field data sheets and the chain-of-custody form are included in Exhibit A. Results The general groundwater flow beneath the site on January 18, 1993,was to the west-northwest under an average hydraulic gradient of 0 004 (Figure 3) A summary of depth-to-water measurements and calculated groundwater elevations is presented in Table 1. Table 2 lists past and present groundwater flow directions and hydraulic gradients for this site. Analytical results of groundwater samples are summarized in Table 3. The complete laboratory report for the sampling event is presented in Exhibit A Figure 4 shows TPH-G me and BETX concentrations for the January 1993 sampling event Figure 5 is a benzene isoconcentration map 7403VtEPCRI SVAM3QrRX r