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01 U D 3164 Gold Camp Drive Suite 200 Delta Rancho Cordova,CA 95670.6021 //. Consultants, ,Inc. JUL 1 4 2000 U.S.A. Consultants,l .L 9161638-2085 FAX:9161638-8385 ENVIRONMENT HEALTH PERMIT/SERVICES July 14,2000 Ms. Carol Oz San Joaquin County, Public Health Services Environmental Health Division 304 East Weber Ave., Third Floor Stockton, CA 95202 Subject: Work Plan for Additional Groundwater Assessment and Feasibility Testing ARCO Station 2186 3212 North California Street Stockton, California Dear Ms. Oz: I Delta Environmental Consultants, Inc. (Delta) is submitting this work planito further assess the extent of petroleum hydrocarbons in groundwater and to conduct a feasibility study for the Atlantic Richfield Company (ARCO) facility, located at 3212 North California Street (Figure 1). This work plan supereedes the previous work plan prepared and submitted by the IT Group(February 10, 2000). The proposed scope of work involves installation of three offsite groundwater monitoring wells and conducting a vapor extraction feasibility test. This work plan also includes information recently acquired regarding the location of water supply wells near the subject site-which had not been previously identified. Because of this new information, the quantity and locations of the monitoring wells have been revised from the February 10, 2000 work plan. SITE BACKGROUND The site is currently an active ARCO service station. The facility configuration is shown,of figure 2. J In August and September 1995, EMCON observed the drilling of six vertical soil borings (B-1, B-3 through B-5, B-7 and B-8) and two 45 degree angle borings (B-2 and B-5). Three of the borings (B- 1, B-4 and .B-5) were converted to groundwater monitoring wells (MW-1 through MW-3), and three of the borings (13-3, B-7 and B-8) were converted to dual completion vapor extraction wells (VW-1 through VW-3). In October 1996, EMCON observed the drilling of boring B-9. The boring was converted to groundwater monitoring well MW-4. } In June 1999, the former gasoline underground storage tank (UST) and associated dispensers and piping were replaced. The former UST complex consisted of two 10,000-gallon and one 8,000- gallon single-wall fiberglass tank. The 8;000-gallon UST formerly stored super unleaded gasoline and the two 10,000-gallon USTs formerly stored regular unleaded gasoline. The gasoline UST fill ports were located at the northern ends of the tanks. Fiberglass piping located at the northern ends of Providing a Competitive Edge - r