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a Ti_ ANALYSIS, INC, GROUND ZERO 2291 W. March Lane, Suite 127D Stockton, California 95207 Telephone: (209) 952.3481 Facsimile: (209) 952-9892 November 25, 1996 Ms. Margaret Lagorio San Joaquin County Public Health Services Environmental Health Division P.O. Box 388 Stockton, CA 95201-0388 Subject: Work Plan for Conducting a Limited Subsurface Assessment 8960 W. Walnut Grove Road, Thornton, California Dear Ms. Lagorio: At the request of Mr. Mike Manser of Thornton BP, Ground Zero Analysis, Inc. (Ground Zero) has prepared this work plan to perform a limited subsurface assessment at the subject site (Figure 1). The scope of work includes hand-augering six soil borings and collecting soil and possibly groundwater samples in an effort to assess subsurface conditions in the vicinity of the existing underground storage tanks (USTs). BACKGROUND It is our understanding that three 10,000 gallon USTs are present at the site. The USTs were installed by Stockton Service Station Equipment Company in 1984 and are located beneath the pump islands. The USTs currently store diesel, regular unleaded and supreme unleaded fuels. According to Mr. Manser, leaded gasoline was never stored in any of the USTs. There has been he USTs have leaked. The r otherwise that an of t no indication, from inventory records o Y approximate location and orientation of the USTs are shown on Figure 2. SCOPE OF WORK Ground Zero will advance six borings, one near the ends of each UST, using a hand auger to determine subsurface conditions in the vicinity of the USTs. Groundwater beneath the site is expected to occur at approximately 8 to 10 feet below ground surface (bgs). The borings will be advanced to approximately 10 feet bgs or to the capillary fringe (soil/water interface), whichever is shallowest. Soil encountered during drilling will be identified by a field geologist according to the Unified Soil Classification System. Any odors or discoloration will be noted.