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CL Properties, VI E37801.02A December 6, 1999 Page 3 4.0 PROPOSED INVESTIGATIVE PROCEDURES This characterization will consist of a field investigation, a laboratory testing program, and preparation of a technical report. This work plan and the activities summarized below are intended to be consistent with the requirements of the SJCEHD. Standard operating procedures (SOPs), relevant to the field and laboratory activities,are described in Appendix A. Specific procedures and deviations to the SOPS which will be used in this work are summarized in the following sections. 4.1 Field Investieation: The field investigation will consist of collecting subsurface soil vapor samples for chemical analyses. 4.1.1 Soil Sampling: Twining proposes to collect subsurface soil vapor samples at the project site from sampling points advanced in two locations: • five sampling points in the estimated former location of the dry cleaners ; and a two sampling points adjacent(across West Sonora Street)to the current dry cleaner facility. The proposed soil sampling points will not be advanced in an easement or right-of-way controlled by a municipal government. Nor will the sampling points be advanced to less than 15 above the estimated groundwater depth. Therefore,municipal permits will not be required for this assessment. An application for a soil boring permit will be submitted to the SJCEHD with this work plan. The soil vapor assessment includes the collection of five soil vapor samples from the vicinity of the former dry cleaning facility located at 513 South Center Street and two soil vapor samples adjacent (across West Sonora Street) from the active dry cleaning facility. The soil vapor sampling points will placed in the vicinity of most likely areas of contamination, including the exterior sewer and subsurface utility trenches. A manually operated slide hammer will be used to drive the sampling rods with a 1 inch expendable sampling tip to the desired depth(three to five feet BSG). The rods will be partially retracted in preparation for sampling. Prior to applying vacuum to the sampling system,hydrated bentonite will be placed within the annular space between the outer diameter of the rods and the sides of the borehole. The purpose of this is to provide additional security against drawing ambient air into the borehole. The sampling points will connected to a vacuum pump with clean polyethylene tubing and an in-line regulator. A maximum gas flow rate of 200 cubic-centimeters per minute will be applied to the vacuum pump to purge the system of residual gas. A minimum of three tubing volumes will be purged prior to sample collection to assure that samples are representative of soil vapors. Samples will then be collected in Tedlar®bags and placed into ice chests containing blue ice for transport to the off-site laboratory. All reusable sampling equipment will be decontaminated before, and between uses, in order to minimize the possibility of cross-contamination. The vapor samples will be analyzed off-site by a state certified and accredited laboratory. Soil vapor samples will be submitted for laboratory analysis. Sample handling procedures are summarized in our SOPS. At least one sample per from each boring will be submitted for analysis. The analytical results for soil vapor samples collected from these sampling points may provide data on the existence of HVOCs. This data will be evaluated to determine if further assessment of the extent of HVOC migration in soil and or groundwater is necessary.