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Guide for Characterization of Sites Contaminated with Energetic Materials
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APPENDIX D: BOREHOLE DRILLING
Guide:
1. Review of historical borehole records
2. Site clearance
3. Mechanical drilling
Borehole Drilling and Soil Sampling
The local stratigraphy of the site is first determined by examining the log-
book of existing boreholes (typically available from the Department of Environ-
ment). The thickness of unconsolidated material can then be assessed. The pro-
posed boreholes and monitoring wells are located taking into account the geology
and the topography of the site. Hydrogeologists should be involved at this step to
evaluate the direction of groundwater flow and the likely extent of the potential
contaminant plume. Once drilling locations have been sited, a level 2 clearance
must be obtained prior to positioning the equipment. The drilling depth of the
boreholes is defined on-site depending on the observations made from the first
drilling.
For soil sampling, a hollow-stem auger or geoprobe is used to drill a bore-
hole. These drilling devices are often equipped with a split spoon or lined core
barrel sampler to collect a cylindrical segment of the subsurface soil profile. For
each borehole, a well log should identify all geologic formations present in the
unconsolidated material. Initial borehole diameter in unconsolidated material
should be large enough to allow the installation of 5-cm (2-in.) monitoring wells.
A good subsurface sampling procedure consists of collecting soil cores at
intervals of 1.5 to 2.0 m and analyzing the soils using the colorimetric test kits
(Appendix H). If contaminated, further analysis by US EPA Method 8330 or
8095 should be carried out. This way, a three-dimensional map may be con-
structed and a more comprehensive understanding of the contamination on the
site is obtained. The down-hole equipment is decontaminated by immersing it in
a hot water barrel and by cleaning it with high-pressure steam. In addition, ace-
tone should be sprayed on the core barrel sampler to remove the last traces of
explosives, followed further by spraying with distilled water.
Monitoring Well Installation
Wells required for subsurface sampling should be drilled by contractors who
specialize in contaminated site assessment. Nested wells with 24 m depth levels
can be used to establish the contaminant profile, but frequently only a single
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