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of hydrated bentonite grout. The borehole should be grouted to the surface with hydrated bentonite. With respect to deep probe construction with multiple probe depths, the borehole should be grouted between probes. One(1) foot of dry granular bentonite should be emplaced between the filter pack and the grout at each probe location. See Figure 2 for more information. 3. The use of a downhole probe support may be required for deep probe construction (e.g., 40 feet bgs for direct push probes). a. Such probe support may be constructed from a one-inch diameter bentonite/cement grouted PVC pipe or other solid rod, or equivalent, allowing probes to be positioned at measured intervals. b. The support should be properly sealed or solid (internally or externally)to avoid possible cross-contamination or ambient air intrusion. c. The probes should be properly attached to the exterior of the support prior to placement downhole. d. Alternative probe support designs should be described in the project workplan. If probe support will not be used for deep probes,justification should be included in the project workplan. 4. Tubing should be properly marked at the surface to identify the probe location and depth. 5. As-built diagrams for probes or wells should be submitted with the soil gas investigation report detailing the well identification and corresponding probe depths. A typical probe construction diagram may be submitted for probes with common design and installation. 6. Unless soil gas probes are removed or decommissioned, probes should be properly secured, capped and completed to prevent infiltration of water or ambient air into the subsurface and to prevent accidental damage or vandalism.For surface completions, the following components may be installed: a. Gas-tight valve or fitting for capping the sampling tube; b. Utility vault or meter box with ventilation holes and lock; c. Surface seal; and d. Guard posts. 01/28/2003 -7-