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11 September 2020 Advanced AGE Project No. 20-6107 Environmental Page 4 of 6 3.1.2 Grab Groundwater Sampling Grab groundwater samples will be collected from borings B1, B2, and B5 to assess the lateral extent of petroleum hydrocarbon impact to groundwater. For collection of grab groundwater samples, soil borings will be advanced to the top of the groundwater table as identified by collection of a saturated soil sample. Once groundwater has been encountered, a Geoprobe (or similar) push -driven water sampling device will be advanced four feet into the water -bearing zone. Grab groundwater samples will be collected using a Geoprobe water sampling assembly fitted with a pre -cleaned, one -inch diameter 0.01 -slotted temporary well screen. Each groundwater sample will be extracted by dedicated disposable polyethylene tubing through the hollow center of the push rods into the screen section. Samples will be analyzed for the constituents listed in Section 2.3. and will be collected into laboratory -supplied, preserved 40 -ml VOA vials, 1 -liter unpreserved amber bottles, and 250 -ml polyethylene containers preserved with nitric acid. Appropriately sealed and labeled samples will be placed in a chilled container under ice and transported under chain -of -custody procedure to an ELAP-certified laboratory. Each sample container will be labeled with sample designation, time, date and sampler's initials. 3.1.3 Soil -Vapor Sampling & Analysis At each of the two (2) proposed soil -vapor sampling locations, borings will be advanced to 5 feet bsg using a three-inch diameter hand auger. Once the total depth is reached a semi-permanent soil -vapor sampling well will be installed within the boring. The temporary sampling point will consist of 7 feet of %-inch Teflon tubing and a sampling tip (generally inert ceramic stone). Prior to installing the tubing and sampling stone, #2/12 sand will be poured in the annuals of the boring for the sample tip to rest on. The tubing and sampling tip will then be lowered to a depth of five feet bsg and one foot of #2/12 sand will be poured around the tip to create a filter pack. Above the sand, one foot of dry granular bentonite will be placed to a depth of 4 feet bsg. Thereafter, hydrated bentonite will be placed from 3 feet bsg to near surface grade to seal each location and prevent ambient air intrusion during sampling. Soil -vapor samples will be collected after allowing a minimum of two hours equalization time following installation of the soil -vapor wells. Prior to soil -vapor sample collection, three calculated volumes of air will be purged utilizing a 6 -liter purge canister and manifold, calibrated to 200 milliliters per minute (ml/min). One -liter Summa® sampling canisters will be used to collect soil -vapor samples for TO -15 analysis. Sampling and purge canisters will be connected together with a dedicated and serialized sampling inlet manifold. The sampling inlet manifold consists of a vapor -tight valve; a particulate filter; a flow restrictor calibrated to 200 milliliters per minute (ml/min); a stainless-steel tee -fitting; two vacuum gauges at either end of the flow controller and connections for both purge and sampling canisters (manifold assembly). The manifold assembly will be attached to the'/4-inch Teflon® tubing from the soil -vapor well. The purge