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22 November 2023 AdvancedGeo Project No. 23-7523 An Employee-Owned Company Page 3 of 7 � from approximately 14.75 to 15 feet bsg, for the vapor implant to be placed upon. Once the sand pack at the base of the borehole was in place, a 1/4-inch diameter, 2-inch-long polyethylene soil-vapor implant and approximately 17 feet of inch Teflon® tubing were lowered to the bottom of the boring. Once the sand, tubing and vapor implant were in place, filter pack of #2/12 sand was added from the bottom of the borehole to approximately 14 feet bsg. Following placement of the filter pack, approximately one foot of dry-granulated bentonite was placed atop of the filter pack from 13 to 14 feet bsg. Thereafter, granulated bentonite was hydrated to a depth of 10 feet bsg for the start of the second soil-vapor sampling point. The second implant was installed by placing #2/12 sand was placed atop the bentonite to a depth of 9.75 to 10 feet bsg. Once the sand pack at the base of the borehole was in place, a '/4-inch diameter, 2-inch-long polyethylene soil-vapor implant and approximately 12 feet of inch Teflon®tubing were lowered to the bottom of the boring. Once the sand, tubing, and vapor implant were in place, filter pack of #2/12 sand was added from the bottom of the borehole to approximately 9 feet bsg. Following placement of the filter pack, approximately one foot of dry-granulated bentonite was placed atop of the filter pack from 8 to 9 feet bsg. Thereafter, granulated bentonite was hydrated to a depth of 5 feet bsg for the start of the third soil-vapor sampling point. Once the bentonite reached the desired depth of 5 feet bsg the third implant was installed by placing #2/12 sand was placed atop the bentonite to a depth of 4.75 to 5 feet bsg. Once the sand pack at the base of the borehole was in place, a '/4-inch diameter, 2-inch- long polyethylene soil-vapor implant and approximately 7 feet of '/4 inch Teflon® tubing were lowered to the bottom of the boring. Once the sand, tubing, and vapor implant were in place, filter pack of #2/12 sand was added from the bottom of the borehole to approximately 4 feet bsg. Following placement of the filter pack, approximately one foot of dry-granulated bentonite was placed atop of the filter pack from 3 to 4 feet bsg. Thereafter, granulated bentonite was hydrated to near surface grade to seal the borehole from ambient air intrusion. Following a minimum of two-hours (direct push borings) or 48-hours (hand auger borings on interior of building) of equalization, a pump calibrated to 200 milliliters per minute (ml/m) was used to purge each sampling point. A total of three pre-calculated volumes were removed from each sampling point prior to sample collection. Field sampling sheets documenting the purging times and volumes are included in Appendix A. Once purging was completed, one-liter Summa canisters, with attached flow restrictors calibrated to 150 to 200 milliliters per minute (ml/min), were connected to the '/4-inch Teflon® tubing from the vapor well and the canister was opened. Thereafter, each soil- vapor sampling point was isolated from ambient air by enclosing the soil-vapor point, tubing, and canister assembly in a plastic shroud. Helium gas was infused into the shroud and was measured using a helium meter to verify that an 18 to 25% concentration of helium was introduced and maintained in the shroud. The initial pressure and time were recorded on soil-vapor sampling field logs (Appendix A). The sample canister valves were