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). 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 results produced by this guide is dependent on the competence of the personnel performing it and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing. Users of this test method are cautioned that compliance with Practice D3740 does not in itself ensure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.

1.1 This guide covers how dual-wall reverse-circulation drilling may be used for geoenvironmental exploration and installation of subsurface water quality monitoring devices. The term reverse circulation with respect to dual-wall drilling in this guide indicates that the circulating fluid is forced down the annular space between the double-wall drill pipe and transports soil/sediment and rock particles to the surface through the inner pipe.

Note 1: This guide does not include considerations for geotechnical site characterizations that are addressed in a separate guide.

1.2 Dual-wall reverse-circulation for geoenvironmental exploration and monitoring-device installations will often involve safety planning, administration, and documentation. This guide does not purport to specifically address exploration and site safety.

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.