SITE INFORMATION AND CORRESPONDENCE

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Workplan for Additional Assessment and Feasibility Testing 2 7-Eleven, Inc Store No 17334 4501 North Pershing Avenue Stockton CA October 17,2001 I Lateral and Vertical Plume Delineation There are three underground storage tank(UST)sites with documented releases located near 7-Eleven 17334:the Cardlock Gasoline Station at 4555 N. Pershing Ave. (100 feet west(upgradient) of the site), a Shell Service Station at 4445 N. Pershing Ave. (crossgradient of the site), and an Exxon Service Station at 4444 N.Pershing Ave. (crossgradient of the site). Exxon's well MW-9 is located on the 7-Eleven site (Figure 2). To better delineate the source area and lateral extent of the 7-Eleven plume (and differentiate it from potential offsite plume areas unrelated to 7-Eleven),one downgradient groundwater monitoring well and a replacement for abandoned well MWA (well MWA R) are proposed to be installed as shown on Figure 2. The wells are proposed to be installed to 25 feet below grade,screened from 5-25 feet below grade. To determine the vertical extent of the plume in the source area, a boring will be drilled near the well MW- 1 R location to depths of 50 feet below grade using Simulprobe (dual-barrel) or hydropunch technology. Existing well MW-56 is screened from 38—40 feet below grade, but does not fully delineate the vertical extent of the dissolved MTBE/hydrocarbon plume (IT Corporation,Third Quarter 2001 Monitoring and Sampling Report,October 1,2001). Health and Safety Plan/Permits The existing site-specific Health and Safety Plan will be used during subsequent drilling operations. The i Health and Safety Plan has been prepared as required by the Occupational Safety and Health Administration (OSHA) Standard"Hazardous Waste Operations and Emergency Response"guidelines (29 CFR 1910.120). The document will be reviewed and signed by all IT Corporation personnel and i subcontractors performing work at the site. II All applicable permits will be obtained prior to field operations. On-site underground utilities will be marked by an underground utility company, and Underground Service Alert(USA)will be:contacted and requested to notify the local utility companies to mark the location of underground utilities surrounding the site. For.offsite drilling, a private utility locating service may also be used. i I 17334SAW.DOC I