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r • Workplan for Additional Subsurface Investigation Fortner P.E.O'Hair Site,1102 South Aurora Street,Stockton,San Joaquin County,California Page 2 BACKGROUND In November 1988, two underground storage tanks (UST)were removed from the subject property. Two additional USTs were removed in February 1994. During the removal process, no soil staining was observed in the vicinity of three of the former UST locations. However, county of San Joaquin Environmental Health Division (County) personnel noted that soil staining and petroleum hydrocarbon odor was present beneath one of the former USTs. Confirmation soil samples were collected from beneath each of the former USTs. None of the confirmation soil samples contained detectable levels of gasoline or gasoline-related constituents. The soil samples were not analyzed for methyl t-butyl ether(MTBE) or the other fuel oxygenates. MTBE and the other fuel oxygenates were not required by the state of California to be analyzed at that time. In April of 1997, the County issued a letter stating that they would not support closure for the site. Apex was contracted by Rexel on December 10, 2001 to prepare this Workplan and bring the site into compliance with all regulatory agencies. INSTALATION OF GEOPROBE® SOIL BORINGS Apex proposes to advance five Geoprobe® soil borings and collect five soil samples and five groundwater samples at the subject site. The locations of the proposed Geoprobe® borings are shown on Figure 3. The borings will be installed to an approximate depth of 14-feet below grade surface (bgs) to evaluate the possibility of petroleum-impacted soil and groundwater at the site. Anticipated depth to groundwater at the site is expected at 12 feet bgs. Apex personnel may modify the total depth of the borings as site conditions warrant. Due to the shallow depth to groundwater at the site(12 feet bgs), one soil sample from each boring will be collected at approximately 10-feet bgs (just above the saturated zone). Soil lithology and visual and olfactory observations will be recorded in the field and used to possibly modify the sample collection interval selection. In addition, all soil samples will be field screened with a photo ionization device (PID). All fieldwork will be conducted in accordance with the Apex Standard Operating Procedures(SOP)included in Appendix B. Soil core sampling will be conducted using 4-foot sections of decontaminated % inch inside diameter (ID)galvanized steel probe pipe. The probe pipe is connected to a I-foot long;'/a inch ID galvanized steel soil core tube. Stainless steel decontamination insert rods are placed through the probe pipe and sampling core. The'probe pipe, soil core, and insert rods are together pneumatically driven to the depth the soil core is desired. The insert rods are removed and the probe pipe and core tube are driven one foot to obtain the soil core sample. The probe pipe containing the soil core sample is removed from the hole and the soil sample is disconnected from the probe pipe. The ends of the core are sealed using Teflon® tape and plastic