Standard Recommended Practice for
Decommissioning Geotechnical
Exploratory Boreholes
AASHTO Designation: R 22-97 (2005)
INTRODUCTION
The preservation of groundwater resources is a very important issue in the design, construction, and maintenance of the highway infrastructure system.
Most projects require some type of on-site subsurface geotechnical investigation to properly design the facilities.
These investigations typically involve progressing smaller diameter (<200 mm) exploratory boreholes up to depths of approximately 60 m.
In some instances cone penetrometers or instrumentation devices such as piezometers, monitoring wells, and vane shear tests are used to obtain subsurface information.
By progressing exploratory boreholes which may penetrate the water table, a conduit for surface and subsurface aquifer cross contamination may be introduced.
In situations where the investigation may lead to the contamination of groundwater resources, it would be prudent to properly abandon the borehole.
Construction of a borehole seal during decommissioning can add significantly to the time, material, and labor costs of geotechnical exploratory boreholes.
Some states have regulations which mandate that all geotechnical exploratory boreholes must be sealed. When that is the case,
this recommended practice is of limited use, and the reader should consult references pertaining to borehole sealing.
If borehole sealing mandates are not in effect, this recommended practice may provide some guidelines as to which boreholes should be sealed, as well as the
procedures involved in this determination.
Click below to download AASHTO Designation: R 22-97 (2005) pdf free
Click here to download AASHTO Designation: R 21-96 (2004) pdf free download
