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Soil Vapor Sampling SOP Page 5 of 11 Stantec Rev. 1.0 Apr 2019 manufacturer-supplied silicon sleeve then driven through the concrete slab using a previously drilled small diameter hole. The installer should follow the Cox-Colvin standard operating procedures except that use of water and the water dam for seal check should never be used. 7.0 EXTERIOR SOIL VAPOR PROBE INSTALLATION Semi-Permanent Probe Installation Soil vapor probes will be installed to the required depth below ground surface (bgs). Each soil vapor probe location will be completed using a 3-inch diameter hand auger (for shallow probes where utility clearance is needed) or direct-push techniques (e.g., Geoprobe) to advance the borehole to the target depth. Following drilling, a soil vapor probe will be installed and constructed at each location as follows. • Approximately six inches of#3 sand will be placed at the bottom of the borehole. • A stainless-steel soil vapor implant, consisting of a stainless-steel screen will be attached to '/4-inch outside diameter Teflon° tubing and centered into the borehole at a depth of five feet bgs. • The annular space will be then filled with sand to 6 inches above the vapor implant. • Approximately six to twelve inches of dry granular bentonite will be placed immediately above the sand pack. The annulus above the dry bentonite will be filled with hydrated bentonite, placed in four-inch lifts, to two inches below the surface. • The top two inches of the borehole will be filled to grade with cement grout. • The soil gas probe will be completed with a ball valve. • Use of a hand auger will greatly disturb subsurface soil and as such one week is recommended for subsurface equilibration to occur prior to sample collection. Follow individual state guidance regarding equilibration times for probe installations using direct push or hollow-stem auger. Note: Use of air rotary or rotosonic drilling may require longer equilibration times. Mud rotary drilling is never acceptable for soil gas probe emplacement. Note: for soil gas probes installed at a depth greater than 15-feet bgs, a down-hole tubing support rod (centralizer) should be used to ensure that the probe is placed at the correct depth. Small diameter PVC pipe, closed at both ends, is commonly used and the probe and tubing are affixed to the exterior of the pipe. THIS INFORMATION FOR AUTHORIZED COMPANY USE ONLY STANTEC CONSULTING