AASHTO R 22-97 (2019)

This standard practice addresses the permanent decommissioning (closure) of the following types of geotechnical exploratory boreholes. it is specifically intended to address the closure in situations in which hazardous material or solid wastes are determined not to be present. Included in the list of geotechnical exploratory boreholes are:

• Boreholes progressed with temporary casing for obtaining soil, rock, and groundwater information;
• Uncased boreholes progressed for obtaining soil, rock, and groundwater information using drilling mud or open-hole techniques;
• Hollow-stem flight auger boreholes;
• Observation wells for monitoring groundwater conditions;
• Instrumentation boreholes (i.e., piezometers, Borros points, etc.);
• Cone penetrometer boreholes; and
• Soil characterization tests (vane shear, dilatometer, etc.).

This practice describes the overall process of decommissioning the holes and, as such, includes a systematic approach to completing the process. The typical steps entail an evaluation of the specific site characteristics and potential problems, a review of available decommissioning options including the null option if applicable, selection of an appropriate sealant, and a method of sealing. Specific requirements for the quality control and performance of the sealed borehole are addressed. Record-keeping requirements are noted.