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L %00 L26 February 2007 AGE-NC Project No. 99-0669 LPage 3 of 4 L 3.0. FIELD PROCEDURES All field procedures will be overseen by an AGE representative under the supervision of a California LProfessional Geologist. Procedures for soil-gas vapor sampling are included below. L3.1. SOIL VAPOR INVESTIGATION PROBE BORING ADVANCEMENT Each probe boring will be advanced to a maximum depth of 5 feet b_sg using a van-mounted L Geoprobe 5400 direct-push probing unit equipped with 1.25-inch, stainless steel, hollow probing rods. The G oe probe ro s are advanced using a hydraulic hammer to drive the attached soil vapor Lsampling tool to specified depths. 3.L L Collection Of Soil Vapor Samples LSoil vapor samples will be obtained at depths of approximately 5 feet bsg in each boring. Samples Lwill be collected using a Geoprobe soil vapor assembly. An expendable vapor point will be placed into a point holder at the bottom of an assembly of 1.25-inch diameter hollow drive rods.The assembly will then be advanced to the specified depth and retracted approximately six to twelve inches in order to disengage the expendable point and expose a column of strata from which soil vapor can be extracted.A single use,'/4-inch diameter disposable polyethylene tubing is then attached to a tubing adapter equipped with an O-ring to ensure a vacuum- L tight seal. The adapter assembly is then lowered through the center of the Geoprobe hollow drive rods to the specified depth and secured by threading into the expendable vapor point holder. LAbove ground,the surface around the soil vapor sampler will be sealed with a bentonite_sealant to � prevent ambiggAk intrusion.The end of the polyethylene tubing is attached by a two-way inlet port L to a Tedlarbag placed inside an SKC Vac-U-Chamber(lung box)vacuum chamber.A vacuum pump attached to a purge port of the vacuum chamber is then used to purge the exposed soil column, through the sampling tubing and inlet port, until approximately three volumes of soil vapor or L ambient air is evacuated through the sampling system. The vacuum chamber is then sealed and the vacuum pump is attached to a vacuum outlet port of the chamber. When vacuum is applied to the chamber,a negative pressure is created around the Tedlar bag,which inflates,allowing the soil vapor Lsample to enter directly into the bag via the inlet port. When the sample is co�lipcted, the negative pressure in the chamber is reduced and the sample bag is sealed,labeled,log�o-fl a chain-of-custody form, and place into a dry cooler(room temperature). Subsequently, all of the collected soil vapor Lsamples will be delivered to a State-certif ed"laboratory for analysis of the chemical constituents LAdvanced GeoEnvirenmental,Ina t L