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08 May 2008 AGE-NC Project No. 98-0465 Page 5 of 6 4.0. FIELD PROCEDURES All field procedures will be overseen by an AGE representative under the supervision of a California Professional Geologist.Procedures for the advancement/destruction of soil probe borings,soil vapor sampling, equipment decontamination and sample shipment are outlined below. 4.1. PROBE BORING ADVANCEMENT Each probe boring will be advanced to a depth of approximately five feet bsg using a van-mounted Geoprobe 5400 direct-push probing unit equipped with 1.25-inch, stainless steel, hollow probing rods. The Geoprobe rods are advanced using a hydraulic hammer to drive the attached soil vapor sampling tool to specified depths. 4.2. COLLECTION OF SOIL VAPOR SAMPLES Soil vapor samples will be obtained at a depth of approximately four to five feet bsg in each boring. Samples will 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 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, 1/4-inch diameter disposable polyethylene tubing is then attached to a tubing adapter equipped with an O-ring to ensure a vacuum-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. Above ground,the surface around the soil vapor sampler will be sealed with a bentonite sealant to prevent ambient air intrusion. It is recommended that at least 20 minutes elapse prior to sample collection to allow the bentonite to form a seal and equilibrate to probe/sampling location.To ensure that a reliable soil-vapor sample is collected with no ambient air breakthrough down the probe rod, AGE will apply an appropriate amount of isopropyl alcohol (approximately 6 to 8 ounces) to adequately wet a cotton towel;the wetted towel will be completely wrapped around the base of the probe rod where it contacts the surface and the bentonite seal. The end of the polyethylene tubing is attached by a two-way inlet port to a Tedlar bag 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 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. Advanced GeoEnvironmental,Inc.