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r , U � APPENDIX STANDARD PROCEDURES FOR SOIL VAPOR SAMPLING (Toxichem Management Systems, Inc.) FIELD PROCEDURES (HAND-AUGER HOLES) • If warranted,underground utility locator should scan proposed boring locations and in all cases Underground Service Alert should be notified for utility service clearance. • If appropriate, surface slab should be cored by a concrete coring subcontractor, vacuuming up all excess water. • Pre-cleaned 2-inch diameter hand auger should be used to advance each boring to standard depth of 5 feet below ground surface(bgs), unless site-specific work plan calls for alternate depth(s). • At least one representative sample for the project should be submitted for physical property testing, so each hole should have soil retained for consideration in this selection. • The vapor points should be installed by placing approximately 1 to 2 inches of clean sand in the bottom of each bore-hole utilizing a tremmie pipe,then placing the stainless steel expendable vapor tip affixed with stainless steel screen with affixed TeflonTM tubing on the sand. Additional sand should then be placed via tremmie to create approximately a 6-inch sand pack interval around the vapor tip as the tremmie hosting the TeflonTM tubing is withdrawn. Approximately 1 to 2-inches of granular bentonite(such as BensealTM) should be placed on top of the sand pack, also via tremmie pipe. Then granular bentonite hydrated with water at a 50/50 ratio should be placed in the borehole. Hydrated bentonite should extend up to the ground surface to ensure a tight seal. The TeflonTM tubing should be capped with a Swagelok valve in preparation for sampling. An equilibrium time of at least 8 hours should ideally be allowed prior to sampling. • The soil vapor sampling set-up for each temporary well should be as follows: The tubing is affixed to a sample shut-off valve, a 167 milliliters-per-minute flow regulator inclusive of particulate filter,then to a "T"fitting. One end of the"T"is connected to the sampling summa canister. The other end of the"T"is affixed to a purge shut-off valve,a vacuum gauge and a 1-liter summa canister utilized for purging. • A 10-minute minimum vacuum tightness test should be performed on each temporary vapor point by applying and monitoring a vacuum(utilizing the 1-liter summa canister)and maintaining a closed position on the sample shut-off valve on the down hole side of the sampling manifold. When gauge vacuum is maintained for 10 minutes without any noticeable decrease,purging of three volumes of air from the tubing and borehole should be performed. Three purge volumes of au can be verified by the calculated pressure drop in the ]-liter summa canister utilized for purging. Pagel of 2