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GRI B I Associates Geological and Environmental Consulting Services November 4, 1999 San Joaquin County Public Health Services / -n Environmental Health Division - 304 E. Weber Avenue, 3`d FIoor Stockton, CA 95202 `-y Attention: Margaret Legorio Subject: Workplan To Conduct Soil and Groundwater Investigation Reid Plastics UST Site 75 West Valpico Road, Tracy, California GA Project No. 129-05-01 Ladies and Gentlemen: Gribi Associates is pleased to present this workplan on behalf of Reid Plastics Group for the underground storage tank (UST) site located at 75 West Valpico Road in Tracy, California (see Figure 1 and Figure 2). This workplan proposes the drilling and sampling of two soil borings at the site using direct-push coring equipment. The goal of this investigation will be to characterize soil and groundwater quality in the vicinity of the former fuel dispenser in order to attempt to obtain regulatory closure for this UST site. SITE BACKGROUND One 12,000-gallon single-walled steel diesel UST was removed from the site by Bowen Construction-Engineering on January 18, 1999. Three soil samples(one sample taken beneath each tank end and one sample taken beneath the middle of the tank) collected by Mr. Jim Gribi, RG, at a depth of about 14 feet below surface grade in native soils contained no detectable levels of Total Petroleum Hydrocarbons as Diesel (TPH-D); Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX); or Methyl-t-butyl Ether(MTBE). Two soil samples were collected beneath the removed fuel dispenser island. One of these samples collected at about three feet in depth contained 2,300 parts per million (ppm) of TPH-D and no detectable BTEX or MTBE constituents. One sample collected at about five feet in depth beneath the removed dispenser contained 1,900 ppm of TPH-D and no detectable BTEX or MTBE constituents. One soil sample collected at about four feet in depth beneath removed product delivery piping contained no TPH-D,BTEX,or MTBE constituents. Approximately 155 cubic yards of soil excavated during UST removal activities were stockpiled in four stockpiles (Stockpiles A through D on Figure 1) based on obvious evidence of hydrocarbon contamination. Stockpiles B and D exhibited obvious evidence of hydrocarbons, and soil samples collected from these stockpiles contained elevated levels of TPH-D, with no significant detection of BTEX or MTBE constituents. With the exception of one soil sample that contained 1,200 ppm of TPH-D, five soil samples collected from Stockpiles A and C contained no significant levels of 1350 Hayes Street,Suite C-14 0 Benicia 0 California 0 94510 0 Phone (707)748-7743 •Fax (707)748-7763