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May 25, 1989 -2- 89062 D A 5/8-inch outside diameter, hollow, stainless steel sampling probe, with a slotted section on the lower end, will be driven into the subsurface to a depth to be determined on-site. The expected subsurface conditions at the site suggest that soil vapor samples will be collected between 5 and 15 feet in depth. The sampling locations will be based on a regular grid surrounding the UST using 10-foot centers. If the lateral migration is widespread, the grid may have to be stretched to 20-foot centers to find the lateral limits in the time allotted to accomplish this task. The probes will be installed by being driven with a rotary hammer. The soil vapor sample will be drawn from the subsurface up through the hollow soil vapor probe using a peristaltic pump. A vacuum gauge and injection port are connected in series with the peristaltic pump using Teflon tubing an stainless steel attachments. The vacuum gauge is used to monitor blockage of the sample (i.e. , slots often become plugged) and the injection port is used to retrieve the sample. A three-way valve allows the sample to be routed through the photoionization detector (PID) . A sample is collected from the injection port using a gas-tight microsyringe and injected into the PID analyses for total volatile petroleum hydrocarbons. The PID is manufactured by Photovac International (model TIP-1) and is equipped with a 10.6 electron-volt (ev) ultraviolet light source in a PID. The sampling equipment will be decontaminated between samples using a trisodium phosphate (TSP) detergent wash, followed by a tap water rinse. Following completion of the survey, the vapor probe holes will be backfilled with a cement/bentonite slurry and caulked at the surface. TASK 3 - REPORT PREPARATION Prepare a technical report documenting the method of investigation, and findings of the vapor survey including recommendations for additional site assessment as necessary. 1 WT:av/44A