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Geosynte& consultants SUGGESTED OPERATING PROCEDURE ' SUB-SLAB PROBE INSTALLATION Geosyntec Consultants, Inc. Last revision: December 2009 1 INTRODUCTION Beneath most concrete floor slabs is a layer of granular fill material (for structural purposes) that is normally relatively permeable to soil gas; therefore, in most cases it is relatively simple to drill through the concrete floor and extract a sample of the sub-slab soil gas via vacuum for chemical analysis. This suggested operating procedure (SOP) describes methods for the installation of sub-slab probes of sufficient quality to assess potential human health risks due to subsurface vapor intrusion to indoor air and subsequent inhalation exposures. 2 SUB-SLAB PROBE DESIGN AND INSTALLATION 2.1 Utility Clearances Underground utilities (water, sewer, electricity, gas, cable, telephone, etc.) should be reviewed prior to any drilling. 2.2 Probe Design and Installation ' Sub-slab probes will be installed within a hole drilled through the concrete floor slab. If the floor is covered with carpet, a flap will be neatly cut in the carpet with a sharp knife and lifted to access the concrete beneath. After all testing is complete; the carpet flap can be re-secured to the floor with an adhesive. If floor tiles are present, they should be cut with a tile-knife and lifted before drilling to avoid chipping to the extent practicable. Holes in the concrete slab will be drilled using a heavy-duty electrical hammer-drill. Two different diameters of drill bits will be needed: 3/4-inch and 1.5-inch. The 3/4-inch bit must be long enough to penetrate the entire floor slab (typically 6 inches,but occasionally up to 12 inches in industrial buildings) and the 1.5-inch bit only needs to be 6-inches in length. The upper two inches of the hole will be drilled using the 1.5-inch diameter bit. Generated dust will be removed from the hole and then the 3/4-inch diameter hole will be drilled through the centre of the hole until it punctures the floor slab and just enters the underlying granular fill materials, but will not continue into the underlying geologic materials. A significant increase in the rate of the drill-bit penetration or decrease in resistance will usually indicate the bottom of the slab. Upon completion of drilling, the sub-slab probe insert will be installed and sealed promptly to minimize any potential air flow into or out of the drilled hole. The probe insert consists of a brass or stainless steel threaded pipe, coupling, and plug and should not extend beyond the bottom of 1 2009.12.03