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13 February 1997 AGE-NC Project No. 97-0298 Page 4 of 5 data. 4. Decontaminate sampling equipment in an Alconox solution and rinse with water prior to each sampling run. 5. Obtain soil gas samples at depths of 10 and selectively at 20 feet bsg. Samples will be collected using a Geoprobe soil vapor assembly. 6. An expendable vapor point will be placed into a point holder at the bottom of a string of 1- inch diameter hollow drive rods. The assembly NN•ill then be advanced to the specified depth and retracted between six inches in order to engage the expendable point and expose a column of strata from which soil gas can be extracted. 7. A post run tubing adapter equipped .with an O-ring to ensure a vacuum-tight seal is then attached to a'/4-inch diameter,single use,disposable polyethylene tubing. The sampling tube is then lowered through the center of the hollow drive rods and secured by threading into tine expendable point holder. 8. Above ground, the polyethylene tubing is attached to a stainless steel T-valve. This T-valve is then connected to Vacuum pump contained within the GeoProbe 5400 soil sampling machine. 9. The vacuum pump will then be used to apply a negative pressure to the exposed soil column until approximately three volunes of soil vapor or ambient air is evacuated through the sampling system. 10. At the sampling point, a Tedlar bag will placed into a vacuum chan;ber. The sampling tube will be attached directly to the Tedlar sampling bag,through a collapsible, air tight port. The vacuum chamber is then sealed, a negative pressure is applied to the chamber by the vacuum pump. The Tedlar bag will be filled, allowing the sample to enter directly into the Tedlar bag. On complete collection of the gas sample, the negative pressure in the chamber is reduced, the sampling bag sealed. 11. Upon collection, label each sample, log on chain-of-custody and place into a dry cooler. 12. Soil gas from the polyethylene tubing is then monitored for the presence of volatile organics using a photo-ionization detector (PID) pre-calibrated to isobutylene. 13. Deliver samples to an on-site chemist for direct injection into a State-certified mobile laboratory for analysis by EPA methods 8010 and 8020, which includes all target compounds. 14. Backfill each probe boring on the site to surface grade using Portland Cement.