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CRA STANDARD FIELD PROCEDURES FOR SOIL VAPOR PROBE INSTALLATION AND SAMPLING This document describes Conestoga-Rovers & Associates' (CRA's) standard field methods for soil vapor sampling. These procedures are designed to comply with federal, state, and local regulatory guidelines. Specific field procedures are summarized below. Objectives Soil vapor samples are collected and analyzed to assess whether vapor-phase subsurface contaminants pose a threat to human health or the environment. Direct Push_Method for Soil Vapor Samplingf The direct push method for soil vapor sampling uses a hollow vapor probe which is pushed into the ground, rather than augured. The stratigraphy forms a vapor seal between the surface and subsurface environments, ensuring that the surface and subsurface gases do not mix. Once the desired soil vapor sampling depth has been reached, the field technician installs disposable polyethylene tubing with a threaded adapter that screw into the bottom of the rods. The screw adapter ensures that the vapor sample comes directly from the bottom of the drill rods and does not mix with other vapor from inside the rod or from the ground surface. In addition, hydrated bentonite is placed around the sampling rod and the annulus of the boring to prevent ambient air from entering the boring. The operator then pulls up on the rods and exposes the desired stratigraphy by leaving an expendable drive point at the maximum depth. The required volume of soil vapor is then purged through the polyethylene tubing using a standard vacuum pump. The soil vapor can be sampled for direct injection into a field gas chromatograph,pumped into inert Tedlar bags using a"bell jar"sampling device,or allowed toe__,nter a SUMMA vacuum canister. Once collected,the vapor sample is transported under chain of custody to a state- certified laboratory. The ground�suurface.immediately adjacent to the boring is used as a datum to measure sample depth. The horizontal location of each boring is measured in the field relative to a permanent onsite reference using a measuring wheel or tape measure. Drilling and sampling equipment is washed between samples. with tri-sodium phosphate or an equivalent Environmental Protection Agency (EPA)-approved detergent. Once the sampling is completed,the borings are filled to the ground surface with neat cement. Shallow Soil Vapor Point Method for Soil Vapor Sampling The shallow soil vapor point method for soil vapor sampling utilizes a hand-auger or drill rig to advance a boring for the installation of a soil vapor sampling point. Once the boring is hand-augered to the final depth,a 6-inch slotted probe, capped on either end with brass or Swagelok fittings, is placed within 12 inches of No. Page 1 of 2