Standard Guide for Use of Dual-Wall Reverse-Circulation Drilling for Geoenvironmental Exploration and the Installation of Subsurface Water Quality Monitoring Devices

Importancia y uso:

4.1 Dual-wall reverse-circulation drilling can be used in support of geoenvironmental exploration and for installation of subsurface water quality monitoring devices in unconsolidated and consolidated sediment or bedrock. Dual-wall reverse-circulation drilling methods allows for the collection of water quality samples at most depth(s), the setting of temporary casing during drilling, and continual sampling of cuttings while drilling fluid is circulating, if warranted or needed. Other advantages of the dual-wall reverse-circulation drilling method include, but are not limited to: (1) the capability of drilling without the introduction of any drilling fluid(s) (for example, drilling mud or similar) to the subsurface; (2) maintenance of borehole stability for sampling purposes and monitoring well installation/construction in poorly-indurated to unconsolidated sediment.

4.1.1 The user of dual-wall reverse-circulation drilling for geoenvironmental exploration and monitoring-device installations should be cognizant of both the physical (temperature and airborne particles) and chemical (compressor lubricants and other fluid additives) qualities of compressed air that may be used as the circulating medium.

4.2 The application of dual-wall reverse-circulation drilling to geoenvironmental exploration may involve soil or rock sampling, or in situ soil/sediment, rock, or pore-fluid testing.

Note 2: The user may install a monitoring device within the same borehole wherein sampling, in situ or pore-fluid testing, or coring was performed.

4.3 The subsurface water quality monitoring devices that are addressed in this guide consist generally of a screened- or porous-intake device and riser pipe(s) that are usually installed with a filter pack to enhance the longevity of the intake unit, and with isolation seals and low-permeability backfill to deter the vertical movement of fluids or infiltration of surface water between hydrologic units penetrated by the borehole (see Practice D5092/D5092M). Since a piezometer is primarily a device used for measuring subsurface hydraulic heads, the conversion of a piezometer to a water quality monitoring device should be made only after consideration of the overall quality and integrity of the installation to include the quality of materials that will contact sampled water or gas. Both water quality monitoring devices and piezometers should have adequate casing seals, annular isolation seals, and backfills to deter cross-communication of contaminants between hydrogeologic units.

Note 3: The quality of the result produced by this standard is dependent on the competence of the personnel performing it and the suitability of the equipment and facility used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some, but not all, of those factors.

Subcomité:

D18.21

Referida por:

D5995-18, D6286_D6286M-20, D6001_D6001M-20, D5092_D5092M-16R24

Volúmen:

04.08

Número ICS:

73.100.30 (Equipment for drilling and mine excavation)

Palabras clave:

down-the-hole hammer (DTH) drilling; drilling; dual-wall reverse-circulation drilling method(s); geoenvironmental exploration; groundwater; percussion-hammer drilling method; triple-wall percussion-hammer drilling method; vadose zone ;