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j APPENDIX Procedures for Soil Vapor Sampling (SVC Environmental, Inc.) GENERAL FIELD PROCEDURES • 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. i. • Pre-cleaned 2-3inch diameter augers should be used to advance each boring to a 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 j s " _ testing,.so.each'hole should haVe's "I retainnd�,for consideration m'tliis selection .a • The vapor points should be mst�alledYby placing approximately l'to 2 inches=of clean sand r in the bottom of each bore-hole utilizing a tremie 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 tremie to create approximately a . 6-inch sand pack interval around the vapor tip as the tremie hosting the TeflonTM tubing is withdrawn.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 tremie 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 downhole side of . I the sampling manifold. When gauge vacuum is maintained for 10 minutes without any i noticeable decrease,purging of three volumes of air from the tubing and borehole should be performed. The three purge volumes of air can be verified by the calculated pressure drop in the 1-liter summa canister utilized for purging. _ • - i I i Page 7 of 8 j