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Chevron 40 Chevron August 26, 1998 Chevron Pipe Line Company 4000 Executive Parkway,Suite 400 San Raman,CA 94583 P.O.Box 6059 San Raman,CA 94583-0759 Mr. Michael J. Infurna, Jr. San Joaquin County Public Health Services Environmental Health Division 304 East Weber Avenue, Third Floor Stockton, CA 95202 Workplan for Installation of Monitoring Wells Surland Homes Property (Laurelbrook) Tracy, California Dear Mr. Infiuna: Chevron Pipe Line Company(CPL) proposes to install two temporary monitoring wells at the subject site and to collect at least two rounds of groundwater sampling data from the newly installed wells. Results of a soil and groundwater screening event performed on July 8, 1998 indicated the presence of total petroleum hydrocarbons (TPH) characterized as gasoline at 720 micrograms per liter(ug/1), TPH characterized as diesel at 520 ug/l, toluene at 0.7 ug/1, ethylbenzene at 1.6 ug/l, xylenes at 5.4 ug/l, acenaphthene at 1.3 ug/l, fluorene at 3.4 ug/l, pyrene at 0.3 ug/l, and chrysene at 0.2 ug/l in one grab groundwater sample (Reference: Geomatrix Consultants, Inc.'s Soil and Groundwater Investigation and Site Status Report, Surland Homes Property, Tracy, California— August 25, 1998). Because soil particles affected by crude oil may have been present in the sample due to the field techniques used to collect the groundwater sample, CPL proposes to install two temporary monitoring wells for the purpose of confirming the detections. CPL proposes installing the temporary monitoring wells in the same approximate locations of GB-1 and GB-4 (Figure 1). A schematic diagram showing the proposed well construction details for the temporary well is presented in Figure 2. Upon completion, the well will be developed and purged until water quality parameters stabilize. After well development and purging have been completed, a groundwater sample will be collected and analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX) using EPA Method 8020,polyaromatic hydrocarbons (PA-Hs) using EPA Method 8270 SIMS, TPH characterized as gasoline using EPA Method 8015M, and TPH characterized as diesel with silica gel cleanup using EPA Method 8015M. A second groundwater sample will be collected and analyzed for the same constituents approximately 30 days from the first sampling event. Data from both rounds of groundwater sampling will be summarized in a letter report and submitted to your office for review.