Installing VECTOR Technology requires no special drilling systems, techniques, materials, or regulations. All that is required is hollow drill pipe through which the probe can be lowered. In the past, clients have used track as well as truck-mounted hollow stem augers (of varying diameters) and truck mounted rotosonic rigs. Mud-rotary units have been used, however, the last 10 feet of the borehole must be drilled in the absence of drilling muds to assure the absence of pore-clogging muds within the borehole. The probe is installed much like a 2" dia. pieziometric sampling point: a borehole is made, the PVC pipe is lowered through the drill stem, the drill stem is pulled out, the formation collapses around the PVC pipe, and the rig is removed.
What drilling technique is used will, of course, depend on the depth and lithology to be encountered. How the borehole is completed will also depend on local regulations as well as what contaminants are to be expected.
A typical installation into a fine sand unit 20 feet thick, 100 feet BGS contaminated with VOCs will require you to provide a 6"- 8" diameter hollow stem auger rig, standard decontamination equipment if brought from another contaminated borehole, enough bentonite grout above the probe to isolate contaminated groundwater, a metal manhole, a concrete pad, and about half a day of work with allowances for unforeseen delays.
The depth of installation must be known beforehand as must the expected lithology. The probe must not be installed in silts and/or clays, nor must it be installed in very coarse glacial tills and outwash materials. The probe will not work as specified if it installed in consolidated materials such as bedrock, breccias, It is always recommended that the installation depth be ultimately sampled with a split-spoon sampler to assure correct lithology.
The probe should also be installed with at least 4' of saturated overburden above the sensor surface. Additionally, the probe must be installed in saturated materials that will collapse around the sensor surface following removal of the drill from the borehole. Where a collapsing borehole is not likely, the installation may be backfilled with a clean, sorted sand of appropriate sieve size. More information in Questions and Answers: Installation.
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