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i 06 April 2009 AGE-NC Project No. 02-0962 Page 3 of 4 3.0. FIELD PROCEDURES All field procedures will be overseen by an AGE representative under the supervision of a California Professional Geologist. Procedures for soil-gas vapor sampling are included below. 3.1. SOIL-GAS PROBE BORING ADVANCEMENT AND SAMPLING Each probe boring will be advanced to a maximum depth of 5 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. Soil vapor samples will be obtained at depths of approximately 5 feet bsg in each boring. Samples will be collected using a Geoprobe soil vapor assembly. An expendable vapor point will be placed into a poin holder at the bottom of an assembly of 1.25-inch diameter hollow drive rods.The assembly will hen 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 extracte .A single use,'/4-inch diameter disposable polyethylene tubing is then attached to a tubing adapter uipped with an O-ring to ensure a vacuum- tight seal. The adapter assembly is then lowered througi the center of the Geoprobe hollow drive rods to the specified depth and secured by threading int 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.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(1 g 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.71he 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 Tedlw bag,which inflates,allowing the soil vapor sample to enter directly into the bag via the inlet port. I Vhen the sample is collected,the negative pressure in the chamber is reduced and the sample bag i sealed,labeled,log on a chain-of-custody form,and place into a dry cooler(room temperature). S lbsequently,all of the collected soil vapor samples will be delivered to a State-certified laborato for analysis of the chemical constituents listed in Section 2.2. After collection of the sample, soil vapor from the pol ethylene tubing will be monitored for the presence of volatile organics using a photo-ionization d tector(PID)pre-calibrated to isobutylene. Admnce+d GmEnvironmental,Inc.