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borehole is capped with an equivalent thickness of asphalt or concrete patch to match finished grade. Soil Vapor Well Installation The borehole is advanced to the desired sampling depth using a 4 or 6-inch diameter hand auger. The soil vapor probe is attached a length of Tygon or Nylaflow® tubing that is at least two feet greater than the total depth of the borehole with a closed Swagelok® type valve attached to the opposite end. The vapor probe is set at a depth approximately 6 inches above the total depth of the borehole in a #3 Monterey Sand (or the equivalent) filter pack that is at a minimum of one foot thick. A half-foot thick layer of granulated bentonite is placed above the filter pack and hydrated. The soil vapor point is completed to the surface with neat cement grout mixed at a ratio of 6 gallons of water per 94 pounds of cement. A traffic rated well box is set in concrete, flush with the ground surface. The excess length of Teflon® tubing with the Swagelok® type valve is coiled up inside the well box. Soil Vapor Sampling Soil vapor sampling is performed after a minimum time duration of 48 hours, to allow the neat cement grout to cure, and to allow the subsurface vapor concentrations disturbed during installation activities to equilibrate. Soil vapor sampling will not be performed if a significant precipitation event (>0.5-inch of rainfall) has occurred in the previous five days. The sampling apparatus consists of a 6-liter (L) Summa canister for system purging and a 1-L Summa canister for vapor sample collection connected via a manifold to a vacuum gauge, a -33 flow regulator, a filter, and a ball valve. The laboratory prepares the Summa canisters with an initial vacuum of -30 inches of mercury (inHg). The sampling apparatus is assembled and a leak check performed prior to mobilization to the field. Once the sampling apparatus is assembled in the field, Teflon® tubing is attached to the down-hole side of the filter and connected to the Swagelok® type valve on the soil vapor sampling point. The leak check is performed by closing the system at the down-hole side of the filter (placing the ball valve in the closed position) and opening the valve on the purge Summa canister. The valve on the purge Summa Canister is immediately closed once a vacuum registers on the attached gauge. If the vacuum is maintained over a ten-minute period, the apparatus passes the leak check. The apparatus is leak checked again. Once the apparatus passes the field leak check, at least one system volume of air is purged from the system for soil vapor wells and at least three system volumes of air are purged for sub- slab vapor probes. The system volumes are determined by adding together the volume of the airspace within the Tygon or Nylafow® tubing, the volume of the airspace within the manifold, and the annular space surrounding the vapor point (for soil vapor wells). This system volume is used to calculate the vacuum pressure drop that will occur during the purging of at least one system volume. Stantec