ASTM D6286/D6286M-20

Standard Guide for Selection of Drilling and Direct Push Methods for Geotechnical and Environmental Subsurface Site Characterization

SIGNIFICANCE AND USE
4.1 The 1998 edition of this standard was written solely for selection of drilling methods for environmental applications and specifically for installation of groundwater monitoring wells. The second revision was made to include geotechnical applications since many of the advantages, disadvantages, and limitations discussed extensively throughout this document also apply to geotechnical design use such as data collection (sampling and in-situ testing) for construction design and instrumentation. Besides installation of monitoring wells (D5092/D5092M, D6724/D6724M), Environmental investigations are also made for sampling, in-situ testing, and installation of aquifer testing boreholes (D4044/D4044M, D4050).  
4.2 There are other guides for geotechnical investigations addressing drilling methods such as in Eurocode (1, 2)5, U.S. Federal Highway Administration, (3, 4), U.S. Army Corps of Engineers, (5), and U.S. Bureau of Reclamation (6, 7). An authoritative Handbook on Environmental Site Characterization and Ground-Water Monitoring was compiled by Nielsen (8) which addresses drilling methods in detail including the advent of Direct Push methods developed for environmental investigations. Two other major drilling guides have been written by the National Drilling Association (9) and from the Australia Drilling Industry Training Committee (10) and these guides are user for the drillers.  
4.3 Table 1 lists sixteen classes of methods addressed in this guide. The selection of particular method(s) for drilling/push boring requires that specific characteristics of each site be considered. This guide is intended to make the user aware of some of the various drilling/push boring methods available and the applications, advantages, and disadvantages of each with respect to determining geotechnical and environmental exploration. (A) Actual achievable drilled depths will vary depending on the ambient geohydrologic conditions existing at the site and size of drilling/push boring e...
SCOPE
1.1 This guide provides descriptions of various methods for site characterization along with advantages and disadvantages associated with each method discussed. This guide is intended to aid in the selection of drilling method(s) for geotechnical and environmental soil and rock borings for sampling, testing, and installation of wells, or other instrumentation. It does not address drilling for foundation improvement, drinking water wells, or special horizontal drilling techniques for utilities.  
1.2 This guide cannot address all possible subsurface conditions that may occur such as, geologic, topographic, climatic, or anthropogenic. Site evaluation for engineering, design, and construction purposes is addressed in Guide D420. Soil and rock sampling in drill holes is addressed in Guide D6169/D6169M. Pertinent guides and practices addressing specific drilling methods, equipment, and procedures are listed in Section 2. Guide D5730 provides information on most all aspects of environmental site characterization.  
1.3 The values stated in either SI units or inch-pound units (given in brackets) 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 nonconformance with the standard.  
1.4 This guide does not purport to comprehensively address all methods and the issues associated with drilling for geotechnical and environmental purposes. Users should seek qualified professionals for decisions as to the proper equipment and methods that would be most successful for their site investigation. Other methods may be available for these methods and qualified professionals should have flexibility to exercise judgment as to possible alternatives not covered in this guide. The guide is current at the time of issue, but new alternative methods may become available prior ...

General Information

• Status: Published
• Publication Date: 30-Apr-2020
• ICS: 13.080.99 - Other standards related to soil quality
• ICS: 73.100.30 - Equipment for drilling and mine excavation
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.21 - Groundwater and Vadose Zone Investigations

Relations

• Replaces: ASTM D6286-19 - Standard Guide for Selection of Drilling and Direct Push Methods for Geotechnical and Environmental Subsurface Site Characterization
• Effective Date: 01-May-2020
• Refers: ASTM D6914/D6914M-16(2024) - Standard Practice for Sonic Drilling for Site Characterization and the Installation of Subsurface Monitoring Devices
• Effective Date: 15-Mar-2024
• Refers: ASTM D5876/D5876M-17(2024) - Standard Guide for Use of Direct Rotary Wireline Casing Advancement Drilling Methods for Geoenvironmental Exploration and Installation of Subsurface Water-Quality Monitoring Devices
• Effective Date: 15-Mar-2024
• Refers: ASTM D6914/D6914M-16(2024) - Standard Practice for Sonic Drilling for Site Characterization and the Installation of Subsurface Monitoring Devices
• Effective Date: 01-Jan-2024
• Refers: ASTM D5876/D5876M-17(2024) - Standard Guide for Use of Direct Rotary Wireline Casing Advancement Drilling Methods for Geoenvironmental Exploration and Installation of Subsurface Water-Quality Monitoring Devices
• Effective Date: 01-Jan-2024
• Refers: ASTM D3740-23 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Nov-2023
• Refers: ASTM D5778-20 - Standard Test Method for Electronic Friction Cone and Piezocone Penetration Testing of Soils
• Effective Date: 01-Jun-2020
• Refers: ASTM D5088-20 - Standard Practice for Decontamination of Field Equipment Used at Waste Sites
• Effective Date: 01-May-2020
• Refers: ASTM D4403-20 - Standard Practice for Extensometers Used in Rock
• Effective Date: 01-Jan-2020
• Refers: ASTM D4719-20 - Standard Test Methods for Prebored Pressuremeter Testing in Soils
• Effective Date: 01-Jan-2020
• Refers: ASTM D4050-20 - Standard Test Method for (Field Procedure) for Withdrawal and Injection Well Testing for Determining Hydraulic Properties of Aquifer Systems
• Effective Date: 01-Jan-2020
• Refers: ASTM D6598-19 - Standard Guide for Installing and Operating Settlement Points for Monitoring Vertical Deformations
• Effective Date: 01-Nov-2019
• Refers: ASTM D3740-19 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Oct-2019
• Refers: ASTM D6910/D6910M-19 - Standard Test Method for Marsh Funnel Viscosity of Construction Slurries
• Effective Date: 15-May-2019
• Refers: ASTM D4630-19 - Standard Test Method for Determining Transmissivity and Storage Coefficient of Low-Permeability Rocks by In Situ Measurements Using the Constant Head Injection Test
• Effective Date: 01-Feb-2019

Overview

ASTM D6286/D6286M-20: Standard Guide for Selection of Drilling and Direct Push Methods for Geotechnical and Environmental Subsurface Site Characterization provides comprehensive guidance for professionals selecting the most appropriate drilling and direct push techniques for investigating subsurface conditions. Developed by ASTM International, this standard supports both geotechnical and environmental applications such as soil and rock sampling, in-situ testing, and the installation of monitoring wells or instrumentation.

The guide outlines the advantages, disadvantages, and limitations of various drilling and direct push methods, giving practical support for site-specific decision making during subsurface characterization projects. It emphasizes the importance of professional judgment, considering the unique geological, hydrogeological, and project-specific factors at each site.

Key Topics

• Method Selection Criteria: The guide details factors to consider, such as soil and rock types, groundwater presence, contamination concerns, project objectives, and regulatory requirements, impacting the choice between drilling and direct push methods.
• Comparison of Techniques: Sixteen classes of drilling and direct push methods are discussed, with clear explanations of each method’s capabilities, sample types, achievable depths, and suitability for specific conditions.
• Sampling and Testing Needs: Guidance is given for various applications, from standard penetration testing and undisturbed sampling to groundwater monitoring well installation.
• Environmental Considerations: The guide addresses contamination risk, minimization of investigation-derived waste (IDW), and precautions for preserving sample integrity.
• Well Installation and Completion: Includes considerations for casing, grouting, sealing across aquifers, and managing cross-contamination between borehole zones.

Applications

ASTM D6286/D6286M-20 is an essential reference for:

• Geotechnical Site Investigation: Selecting the right methods for acquiring subsurface data to support engineering and construction design, including in-situ soil testing and rock sampling.
• Environmental Investigations: Supporting environmental site assessment (ESA) phases by guiding the installation of groundwater monitoring wells and collection of representative samples without introducing cross-contamination.
• Instrumentation Installations: Assisting the proper selection of drilling or direct push equipment for installing piezometers, inclinometers, settlement points, and other borehole-based monitoring systems.
• Regulatory Compliance: Ensuring investigative activities meet environmental and occupational safety standards as outlined by OSHA and relevant federal, state, and local regulations.

This guide is widely used by geologists, engineers, hydrogeologists, environmental consultants, and contractors to optimize subsurface data reliability while reducing risk and cost in site characterization projects.

Related Standards

To ensure a robust and compliant site investigation, use ASTM D6286/D6286M-20 in conjunction with related standards, including:

• ASTM D5092/D5092M: Design and installation of groundwater monitoring wells.
• ASTM D420: Site characterization for engineering design and construction.
• ASTM D6169/D6169M: Soil and rock sampling in drill holes.
• ASTM D5781, D5782, D5783, D5784, D5872, D5875, D5876: Guides for various drilling techniques for geoenvironmental exploration.
• ASTM D6001 and D6282: Direct push soil and groundwater sampling.
• ASTM D6914: Sonic drilling for site characterization.
• ASTM D1452, D2113: Auger and core drilling for soil and rock.
• OSHA 1910.120: Occupational safety for hazardous waste operations and emergency response.

Practical Value

Implementing ASTM D6286/D6286M-20 enables informed decisions regarding subsurface characterization-resulting in:

• Improved data quality for both geotechnical analysis and environmental risk assessment
• Enhanced safety and regulatory compliance
• Efficient, cost-effective project delivery
• Reduced risk of project delays or costly errors

By aligning site investigation practices with this standard guide, organizations ensure thorough, adaptable, and responsible approaches to subsurface exploration, underpinning successful geotechnical engineering and environmental management outcomes.

Keywords: ASTM D6286, drilling methods, direct push, site characterization, geotechnical investigation, environmental investigation, groundwater monitoring wells, environmental site assessment, subsurface sampling, drilling standard, borehole instrumentation.

Standards Content (Sample)

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.
Designation: D6286/D6286M − 20
Standard Guide for
Selection of Drilling and Direct Push Methods for
Geotechnical and Environmental Subsurface Site
Characterization
This standard is issued under the fixed designation D6286/D6286M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* judgment as to possible alternatives not covered in this guide.
The guide is current at the time of issue, but new alternative
1.1 This guide provides descriptions of various methods for
methods may become available prior to revisions. Therefore,
site characterization along with advantages and disadvantages
users should consult with manufacturers or producers prior to
associated with each method discussed. This guide is intended
specifying program requirements.
to aid in the selection of drilling method(s) for geotechnical
and environmental soil and rock borings for sampling, testing, 1.5 This standard does not purport to address all of the
and installation of wells, or other instrumentation. It does not safety concerns, if any, associated with its use. It is the
address drilling for foundation improvement, drinking water responsibility of the user of this standard to establish appro-
wells, or special horizontal drilling techniques for utilities. priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.2 This guide cannot address all possible subsurface con-
1.5.1 Drilling operators generally are required to be trained
ditionsthatmayoccursuchas,geologic,topographic,climatic,
for safety requirements such as those of construction and
or anthropogenic. Site evaluation for engineering, design, and
environmental occupational safety programs dictated by
construction purposes is addressed in Guide D420. Soil and
country, regional, or local requirements such as the US. OSHA
rock sampling in drill holes is addressed in Guide D6169/
training programs. Drilling safety programs are also available
D6169M. Pertinent guides and practices addressing specific
from the National DrillingAssociation (NDA4U.com) or other
drilling methods, equipment, and procedures are listed in
country drilling associations.
Section 2. Guide D5730 provides information on most all
aspects of environmental site characterization. 1.6 This guide offers an organized collection of information
or a series of options and does not recommend a specific
1.3 The values stated in either SI units or inch-pound units
course of action. This document cannot replace education and
(given in brackets) are to be regarded separately as standard.
experienceandshouldbeusedinconjunctionwithprofessional
The values stated in each system may not be exact equivalents;
judgment. Not all aspects of this guide may be applicable in all
therefore,eachsystemshallbeusedindependentlyoftheother.
circumstances. This ASTM standard is not intended to repre-
Combining values from the two systems may result in noncon-
sent or replace the standard of care by which the adequacy of
formance with the standard.
a given professional service must be judged, nor should this
1.4 This guide does not purport to comprehensively address
document be applied without consideration of a project’s many
all methods and the issues associated with drilling for geotech-
unique aspects. The word “Standard” in the title of this
nical and environmental purposes. Users should seek qualified
document means only that the document has been approved
professionals for decisions as to the proper equipment and
through the ASTM consensus process.
methods that would be most successful for their site investi-
1.7 This international standard was developed in accor-
gation. Other methods may be available for these methods and
dance with internationally recognized principles on standard-
qualified professionals should have flexibility to exercise
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
ThisguideisunderthejurisdictionofASTMCommitteeD18onSoilandRock mendations issued by the World Trade Organization Technical
and is the direct responsibility of Subcommittee D18.21 on Groundwater and
Barriers to Trade (TBT) Committee.
Vadose Zone Investigations.
Current edition approved May 1, 2020. Published May 2020. Originally
approved in 1998. Last previous edition approved in 2019 as D6286 – 19. DOI:
“Drilling Safety Guide,” National Drilling Federation, Columbia, SC, 1985, p.
10.1520/D6286_D6286M-20. 36.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6286/D6286M − 20
2. Referenced Documents mental Exploration and Installation of Subsurface Water-
3 Quality Monitoring Devices
2.1 ASTM Standards:
D6001 Guide for Direct-Push Groundwater Sampling for
D420 Guide for Site Characterization for Engineering De-
Environmental Site Characterization
sign and Construction Purposes
D6151/D6151M Practice for Using Hollow-StemAugers for
D653 Terminology Relating to Soil, Rock, and Contained
Geotechnical Exploration and Soil Sampling
Fluids
D6169/D6169M Guide for Selection of Soil and Rock Sam-
D1452/D1452M Practice for Soil Exploration and Sampling
pling Devices Used With Drill Rigs for Environmental
by Auger Borings
Investigations
D2113 Practice for Rock Core Drilling and Sampling of
D6429 Guide for Selecting Surface Geophysical Methods
Rock for Site Exploration
(Withdrawn 2020)
D2488 Practice for Description and Identification of Soils
D6910/D6910M Test Method for Marsh Funnel Viscosity of
(Visual-Manual Procedures)
D3740 Practice for Minimum Requirements for Agencies Construction Slurries
D6914/D6914M Practice for Sonic Drilling for Site Charac-
Engaged in Testing and/or Inspection of Soil and Rock as
Used in Engineering Design and Construction terization and the Installation of Subsurface Monitoring
D5088 Practice for Decontamination of Field Equipment
Devices
Used at Waste Sites
2.2 Geotechnical Sampling, In situ Testing, and Instrumen-
D5092/D5092M Practice for Design and Installation of
tation in Drill Holes:
Groundwater Monitoring Wells
D1586/D1586M Test Method for Standard Penetration Test
D5608 Practices for Decontamination of Sampling and Non
(SPT) and Split-Barrel Sampling of Soils
Sample Contacting Equipment Used at Low Level Radio-
D1587/D1587M Practice for Thin-Walled Tube Sampling of
active Waste Sites
Fine-Grained Soils for Geotechnical Purposes
D5730 Guide for Site Characterization for Environmental
D2573/D2573M Test Method for Field Vane Shear Test in
Purposes With Emphasis on Soil, Rock, the Vadose Zone
4 Saturated Fine-Grained Soils
and Groundwater (Withdrawn 2013)
D3550/D3550M Practice for Thick Wall, Ring-Lined, Split
D5753 Guide for Planning and Conducting Geotechnical
Barrel, Drive Sampling of Soils
Borehole Geophysical Logging
D4403 Practice for Extensometers Used in Rock
D5778 Test Method for Electronic Friction Cone and Piezo-
D4428/D4428M Test Methods for Crosshole Seismic Test-
cone Penetration Testing of Soils
ing
D5781/D5781M Guide for Use of Dual-Wall Reverse-
D4719 Test Methods for Prebored Pressuremeter Testing in
Circulation Drilling for Geoenvironmental Exploration
Soils
and the Installation of Subsurface Water Quality Monitor-
D6519 Practice for Sampling of Soil Using the Hydrauli-
ing Devices
cally Operated Stationary Piston Sampler
D5782 Guide for Use of Direct Air-Rotary Drilling for
D6598 Guide for Installing and Operating Settlement Points
Geoenvironmental Exploration and the Installation of
for Monitoring Vertical Deformations
Subsurface Water-Quality Monitoring Devices
D6635 Test Method for Performing the Flat Plate Dilatom-
D5783 Guide for Use of Direct Rotary Drilling with Water-
eter
Based Drilling Fluid for Geoenvironmental Exploration
D7299 Practice for Verifying Performance of a Vertical
and the Installation of Subsurface Water-Quality Monitor-
Inclinometer Probe
ing Devices
D5784 Guide for Use of Hollow-Stem Augers for Geoenvi-
2.3 Sampling, Testing, and Installations in Drill Holes:
ronmental Exploration and the Installation of Subsurface
D4700 Guide for Soil Sampling from the Vadose Zone
Water Quality Monitoring Devices
D4044/D4044M Test Method for (Field Procedure) for In-
D5872 Guide for Use of Casing Advancement Drilling
stantaneous Change in Head (Slug) Tests for Determining
Methods for Geoenvironmental Exploration and Installa-
Hydraulic Properties of Aquifers
tion of Subsurface Water Quality Monitoring Devices
D4050 Test Method for (Field Procedure) for Withdrawal
D5875/D5875M Guide for Use of Cable-Tool Drilling and
and Injection Well Testing for Determining Hydraulic
SamplingMethodsforGeoenvironmentalExplorationand
Properties of Aquifer Systems
Installation of Subsurface Water Quality Monitoring De-
D4630 Test Method for Determining Transmissivity and
vices
Storage Coefficient of Low-Permeability Rocks by In Situ
D5876/D5876M Guide for Use of Direct Rotary Wireline
Measurements Using the Constant Head Injection Test
Casing Advancement Drilling Methods for Geoenviron-
D6282/D6282M Guide for Direct Push Soil Sampling for
Environmental Site Characterizations
D6724/D6724M Guide for Installation of Direct Push
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Groundwater Monitoring Wells
Standards volume information, refer to the standard’s Document Summary page on
D6725/D6725M Practice for Direct Push Installation of
the ASTM website.
4 Prepacked Screen Monitoring Wells in Unconsolidated
The last approved version of this historical standard is referenced on
www.astm.org. Aquifers
D6286/D6286M − 20
D6907 PracticeforSamplingSoilsandContaminated Media 4. Significance and Use
with Hand-Operated Bucket Augers
4.1 The 1998 edition of this standard was written solely for
D7242/D7242M Practice for Field Pneumatic Slug (Instan-
selection of drilling methods for environmental applications
taneous Change in Head) Tests to Determine Hydraulic
and specifically for installation of groundwater monitoring
Properties of Aquifers with Direct Push Groundwater
wells. The second revision was made to include geotechnical
Samplers
applications since many of the advantages, disadvantages, and
D7352 Practice for Volatile Contaminant Logging Using a
limitations discussed extensively throughout this document
Membrane Interface Probe (MIP) in Unconsolidated For-
also apply to geotechnical design use such as data collection
mations with Direct Push Methods
(sampling and in-situ testing) for construction design and
D7648/D7648M Practice for Active Soil Gas Sampling for
instrumentation. Besides installation of monitoring wells
DirectPushorManual-DrivenHand-SamplingEquipment
(D5092/D5092M, D6724/D6724M), Environmental investiga-
D8037/D8037M PracticeforDirectPushHydraulicLogging
tions are also made for sampling, in-situ testing, and installa-
for Profiling Variations of Permeability in Soils
tion of aquifer testing boreholes (D4044/D4044M, D4050).
4.2 There are other guides for geotechnical investigations
3. Terminology
addressing drilling methods such as in Eurocode (1, 2) , U.S.
3.1 Definitions:
Federal Highway Administration, (3, 4), U.S. Army Corps of
3.1.1 Fordefinitionsofcommontechnicaltermsusedwithin
Engineers, (5), and U.S. Bureau of Reclamation (6, 7).An
this guide, refer to Terminology D653.
authoritative Handbook on Environmental Site Characteriza-
3.2 Definitions of Terms Specific to This Standard: tion and Ground-Water Monitoring was compiled by Nielsen
(8) which addresses drilling methods in detail including the
3.2.1 borehole wall, n—refers to the naturally-occurring
advent of Direct Push methods developed for environmental
soil(s)/rock(s) surrounding the borehole.
investigations. Two other major drilling guides have been
3.2.2 kelly bar, n—in drilling, a formed or machined section
written by the National Drilling Association (9) and from the
of hollow drill steel used in rotary drilling, which is joined
Australia Drilling Industry Training Committee (10) and these
directly to the swivel at the top and to the drill pipe below.
guides are user for the drillers.
3.2.2.1 Discussion—The flats or splines of the kelly bar
4.3 Table 1 lists sixteen classes of methods addressed in this
engage the rotary table so that the rotation of the rotary table
guide. The selection of particular method(s) for drilling/push
turns the kelly bar, which in turn, rotates the drill pipe and the
boring requires that specific characteristics of each site be
rotary bit.
considered. This guide is intended to make the user aware of
3.2.3 mud rings, n—in drilling, soil or rock cuttings that
someofthevariousdrilling/pushboringmethodsavailableand
form a ring or rings on the drill rod(s) during a rotary-drilling
the applications, advantages, and disadvantages of each with
method, and as such, prevent drill cuttings from being carried
respect to determining geotechnical and environmental explo-
up and out of the borehole.
ration.
3.2.3.1 Discussion—These rings can cause drill rods to
4.3.1 On Table 1, practically all methods allow for coring,
become stuck in the borehole if sufficient drilling fluid is not
but some are much more efficient than others. Some drilling
injected or pumped downhole to keep the cuttings fluid so that
systems such as hollow-stem augers or wireline coring allow
the ring(s) cannot form on the drill rods and block the cuttings
forpracticallycontinuouscoringwithminimaltimeforswitch-
return as drilling progresses.
ing barrels while other drilling methods require the whole
3.2.4 orange-peel bucket, n—in drilling, a bucket-type
drillingequipmentberemovedfromthehole.Aprimeexample
device, somewhat elliptical in shape resembling an orange
is the rate of rock coring using fluid rotary and conventional
peel, that is lowered down the borehole and used to remove
core barrels versus wireline rock coring. Wireline line rock
boulders from the bottom of a borehole.
coring is fast with long continuous runs whereas fluid rotary
requiresmore“triptime”toaddandremoveshorterlengthcore
3.2.5 unconsolidated geologic materials, n—in
barrels using drill rods. Table 1 delineates methods where
groundwater, geology, or hydrogeology, a loosely aggregated
coring is possible, and in general, by either continuous (c) or
solid (particulate) material of geologic origin (soil, sediments,
incremental (i) sampling.
etc.).
4.3.2 Sampling for environmental contaminants in soil,
3.2.5.1 Discussion—Groundwater hydrologists, and
unconsolidated formations or groundwater often requires spe-
geologists, use the terms unconsolidated formations, deposits,
cial considerations. In many environmental applications the
sediments, units, materials, etc., to refer to the general term
use of drilling fluids (air, water, mud or foam) is often
“soil” including other soils (alluvium, glacial till, etc.) as
discouraged or even prohibited as these fluids may dilute the
defined in D653. These terms are often found in groundwater
analytes of interest or even introduce analytes of concern not
standards applied to aquifers. Unconsolidated materials are
previously present (see 5.4).
non-lithified, typically lacking cementation of individual par-
ticles (clay, silt sand, gravel, etc.). The term “unconsolidated”
should not be confused with geotechnical terms of the degree
of soil consolidation (over, normally, under-consolidated) as
The boldface numbers in parentheses refer to the list of references at the end of
defined in D653. this standard.
D6286/D6286M − 20
TABLE 1 Drilling Selection Guide
Typical
Type of Typical Range of Coring
Drilling Casing Samples Reference
Drilling Method Material Depth, Borehole Possible
B
Fluid Advance Obtainable Section
A C
Drilled in m [ft] Sizes, in (see 4.3.1)
cm [in.]
Power auger none, water, soil, weathered
yes <45 [150] 12.7-55 [5-22] S, F Yes(c) 6.2
(Hollow-stem) mud rock
Power auger soil, weathered
none no <45 [150] 5-25 [2-10] S Yes(i) 6.3
(Solid-stem) rock
none, water
soil, weathered
Power bucket auger (below water no <45 [150] 45-120 [18-48] S Yes(i) 6.4
rock
table)
<20 [70] (above
Hand auger none no soil 5-15 [2-6] S Yes(i) 6.5
water table only)
Direct fluid rotary water, mud yes soil, rock >300 [1000] 5-90 [2-36] S, R Yes(i) 7
none, water, soil, rock,
Sonic (vibratory) yes <150 [500] 10-30 [4-12] S, R, F Yes(c) 8
mud, air boulders
Typical 15-30
soil, weathered [50-100]
Direct-push technology none yes 3.8-15 [1.5-6] S, F Yes(c) 9
rock Maximum
60 [200]
Air rotary, soil, rock,
air, water, mud yes <600 [2000] 5-40 [2-16] S, R, F Yes(c) 10.3
Casing-advancer boulders
Reverse circulation,
air, water, foam yes soil, rock >300 [1000] 30-90 [12-36] S, R, F Yes(i) 12
air rotary
Reverse circulation,
water, mud yes soil, rock <600 [2000] 30-90 [12-36] S, R, F Yes(i) 12.3
fluid rotary
S, R, F (F–below
Cable tool water yes soil, rock <1500 [5000] 10-60 [4-24] Yes(i) 13
water table)
Jet percussion water no soil <15.0 [50] 5-10 [2-4] S no 14
Jetting water yes soil <15 [50] 10 [4] S no 14
A
Actual achievable drilled depths will vary depending on the ambient geohydrologic conditions existing at the site and size of drilling/push boring equipment used. For
example, large, high-torque rigs can drill to greater depths than their smaller counterparts under favorable site conditions. Boreholes drilled using air/air foam can reach
greater depths more efficiently using two-stage positive-displacement compressors having the capability of developing working pressures of 12 to 17 kPa [250 to 350 psi]
and 14 to 21 m /h [500 to 750 cfm], particularly when submergence requires higher pressures. The smaller rotary-type compressors only are capable of producing a
maximum working pressure of 6 kPa [125 psi] and produce 14 to 34 m /h [500 to 1200 cfm]. Likewise, the rig mast must be constructed to safely carry the anticipated
working loads expected. To allow for contingencies, it is recommended that the rated capacity of the mast be at least twice the anticipated weight load or normal pulling
load.
B
Soil = S (Cuttings), Rock=R(Cuttings), Fluid=F(some samples might require accessory sampling devices to obtain).
C
I = Incremental sampling, C = continuous sampling.
4.4 This guide is most often used in conjunction with Guide soil sampling (D6282/D6282M), well installation (D6724/
D6169/D6169Monsoilandrocksamplingbecausesamplingis
D6724M, D6725/D6725M) and aquifer testing (D7242/
the primary activity during drilling/push borings. There are D7242M).
several guides that deal with individual drilling methods (see
4.5 Predominant or Typical Drilling/Push Boring Methods
Guides D5781/D5781M, D5782, D5783, D5784, D5872,
Used for Geotechnical and Environmental Applications:
D5875/D5875M, and D5876/D5876M) and how to the com-
4.5.1 Geotechnical Investigations in Soils (unconsolidated
plete them for water quality monitoring well installations (see
deposits)—The most commonly used drilling methods for
Practice D5092/D5092M). Practices on hollow-stem auger
geotechnical exploration are fluid rotary drilling when ground-
(D6151/D6151M) and sonic drilling (D6914/D6914M) were
water is present. Hollow-stem auger drilling is also frequently
written for both geotechnical and environmental purposes and
usedespeciallyinaridregionswhereintroductionoffluidsisto
address sampling methods. Practice D2113 on rock core
be avoided in unsaturated soils.
drilling includes sampling methods.
4.5.2 Environmental Investigations in soils (unconsolidated
4.4.1 This guide covers direct push methods that are only
used to make open holes for testing and sampling. This most deposits)—Most of these investigations are focused on soil
contamination or, groundwater quality investigations so intro-
often accomplished using dual tube systems and using the
tubes for access of the subsurface for water sampling, D6001, duction of drilling fluids is not desirable and methods which
D6286/D6286M − 20
generate minimal waste are highly favored. Direct Push meth- mustbeconsideredbythegeologist/hydrologistorexperienced
ods were developed because they develop minimal investiga- driller before a drilling/push boring method is selected. Devel-
tive derived waste (IDW). Sonic methods are frequently used opment of a Conceptual Site Model (CSM) of significant soil
and generate minimal IDW but large cores. Hollow-stem and rock masses and groundwater conditions within a given
augers and fluid rotary are used yet they generate large site should be described and defined, both vertically and
amounts of IDW. horizontally,beforedrilling.Siteplanningrequiresareconnais-
4.5.2.1 Atmostenvironmentalsiteshazardouscontaminants sance site investigation that considers access to the site and
are present in the subsurface. Because of this fact any drill conditions for setting up the drilling/push boring equipment
cuttings or drilling fluids returned to the surface should be (1-8). The extent of site characterization and specific methods
properly handled, contained and stored (drums or roll-off bins, used will be determined by study objectives. Study objectives
etc.) for sampling and laboratory analysis. Laboratory analyses also will affect the type and complexity of data collected.
may be required to verify that hazardous contaminants are not Sources of data that may be useful during initial site evaluation
present above regulatory action levels prior to proper disposal. include, but are not limited to, topographic maps, aerial
If concentrations of hazardous chemicals in cuttings or waste photography, satellite imagery, information from reconnais-
drilling fluids exceed regulatory action levels the waste may sance drilling/push borings, borehole geophysical-log data,
require treatment before disposal or may need to be properly geologic maps and reports, statewide or county soil surveys,
disposed in a hazardous waste landfill. Review pertinent water-resource reports, well databases, and mineral-resource
regulationsbeforedrilling/pushboringtomaintaincompliance. surveys covering the proposed project area. Available reports
The generation of contaminated waste drill cuttings and fluids of surface and subsurface investigations of nearby or adjacent
significantly increase the potential for worker exposure to projectsshouldbeconsideredandtheinformationapplicableto
hazardous contaminants. Review pertinent regulations (such as the current project evaluated and applied if determined reliable
OSHA 1910.120, etc.) to maintain compliance with worker andbeneficial.Atanysitereviewnearby,availableboringsand
safety and monitoring requirements. discuss drilling/push boring methods with local contractors
4.5.3 Rock, Weathered Rock, and Coarse Cobble Boulder experienced with the geologic conditions.
Drilling—Wireline rock coring is used in competent rock and
5.2 Once the desk studies and field reconnaissance are
results in the best core recovery. For coarse grained unconsoli-
performed, onsite explorations are normally phased using
dated deposits and weathered bedrock samples are very diffi-
subsurface screening methods to refine the CSM before final
cult to recover and, rotary air drill through drive casing
selection of drill hole locations. Site-specific surface geophysi-
advancers are often used and require larger drills. Larger sonic
cal surveys (D6429) (11-15), direct-push soil or water sam-
drills can also drill and recover rock and boulder formations.
pling (D6282/D6282M, D6001), hydraulic profiling (D8037/
4.5.4 Sonic drilling methods have increased in use for both
D8037M), cone penetrometers (D5778), dynamic cone
geotechnical and environmental explorations. The method
penetrometers, or solid stem power augers (D1452/D1452M)
offers very rapid continuous coring with the ability to drill
can be performed in grid patterns across the site to refine the
difficult formations with large diameter equipment.
stratigraphy of the geology at the site and may detect problem
4.5.5 Shallow hand auger (D4700) is used for both disci-
areas for targeting with drilling/push boring and sampling.
plines but in most cases hand applications are used as part of
Surface geophysical methods, such as seismic surveys and
initial site surveys prior to drilling/push boring or just for
electrical-resistivity imaging and electromagnetic-conductance
characterization of shallow soil sampling. Hand auguring is
surveys, can be valuable particularly when distinct differences
verylaborintensiveandhasalmostbeenabandonedinfavorof
in the properties of contiguous subsurface materials are indi-
using direct push equipment.
cated (16, 17). When free product petroleum fuels are present
NOTE 1—The reliability of data and interpretations generated by this
in the subsurface, membrane interface probe (D7352), or
practice is dependent on the competence of the personnel performing it
high-resolution fluorescence logging with induced fluores-
andthesuitabilityoftheequipmentandfacilitiesused.Agenciesthatmeet
the criteria of Practice D3740 generally are considered capable of cence or optical image probes can be used to identify depths
competent testing. Users of this practice are cautioned that compliance
and locations to target for sampling by drilling/push boring
with Practice D3740 does not assure reliable testing. Reliable testing
methods (18, 19).
depends on several factors and Practice D3740 provides a means of
5.2.1 The odds of detecting certain critical geologic features
evaluating some of these factors.
of interest on large sites are greatly improved using screening
Practice D3740 was developed for agencies engaged in the testing,
inspection, or both, of soils and rock. As such, it is not totally applicable
methodspriortodrilling/pushboringandcanbeusedtoreduce
to agencies performing these field practices. Users of this test method
the amount of expensive drill holes. Fig. 1 shows the number
should recognize that the framework of Practice D3740 is appropriate for
of drill holes and the probability of detecting several types of
evaluating the quality of an agency performing drilling. Currently, there is
geologic features at a 260 ha [640-acre, 1 square mile] site (8).
noknownqualifyingnationalauthoritythatinspectsagenciesthatperform
this test method. There is training and certification for drillers that are Without screening methods using geophysics and low-cost
normally required for critical installations such as water well drilling
probing or drilling/push boring methods, some geologic fea-
(NGWA, NDA).
turescouldbetotallymissedevenwith100drillholes.Further,
thescreeningmethodscanbeusedtoreducetheamountofdrill
5. Program Planning and Drilling/Push Boring
holes and target them on critical layers.
Considerations
5.1 All factors affecting both surface and subsurface envi- 5.3 Geotechnical Considerations—Drilling/push boring ac-
ronment at a specific site requires professional judgment and tivities for geotechnical investigations include sampling (both
D6286/D6286M − 20
The probability of finding many types of subsurface geologic features using borings alone is fairly low.The use of supportive studies such as surface geologic mapping,
aerial photo interpretation, and surface and borehole geophysics can greatly improve the chances of successfully mapping the subsurface. Without a complete and
accurate map of the subsurface, site models can be misleading.
FIG. 1 Probability of Finding Geologic Features Using Only Drill Holes on a Large Site (8)
disturbed or intact for laboratory testing), in situ testing, and push equipment has the potential to perform many different
installation of monitoring devices such as piezometers (obser- in-situ tests as drilling progresses (2.3). Groundwater monitor-
vation wells), or inclinometers (seeASTM procedures cited in ing wells using drilling/push boring methods in this standard
2.2). Ideal drilling/push boring methods often are dictated by are designed and installed in accordance with D5092/D5092M
soil or rock types and the likelihood of the method to disturb anddirectpushwellsareinstalledwithaccordancewithASTM
soils ahead of the drilling operation, but more importantly is D6724/D6724M and D6725/D6725M for prepacked wells.
thepresenceofgroundwater.Fluidrotarydrillingpredominates
5.4.1 If the monitoring well also is to be sampled for water
in humid areas with shallow groundwater, whereas in arid
quality during the fluid drilling process, the possible damage
areas, the hollow-stem auger is more commonly used. With
and subsequent aquifer contamination caused by drilling-fluid
unsaturated soils in arid regions it may not be desirable to use
invasion of the borehole wall that may occur during drilling
fluid drilling methods that could wet soil samples prematurely
must be considered. Drilling-fluid invasion of the borehole
ahead of laboratory testing of samples. A common drilling/
wall normally results from the use of a poorly-controlled and
push boring test is the standard penetration test (D1586/
improperly-designed drilling-fluid program. Drill fluids are
D1586M) and only certain drilling/push boring methods are
designed to coat and partially penetrate the wall of the drill
suitable. When drilling in hydraulic structures such as dams
hole to stabilize the boring. Water used as a drilling fluid or to
and levees, drill methods should be selected that minimize the
prepare drilling muds must be tested to verify it is clean and
potential for hydraulic fracturing (see 5.6.2). Air drilling
free of the contaminants of interest or other potential contami-
should not be used in impervious cores of dams and levees.
nants not present at the site. Often, municipal water is
chlorinated and as such could contain trihalomethanes which
5.4 Environmental Considerations—Environmental
are regulated contaminants in groundwater.
drilling/push boring is primarily for the collection of samples
and installation of groundwater monitoring wells (see stan- 5.4.2 The project manager should review the project work
dards listed in 2.3).An authoritative reference for well drilling plan, sampling plan and quality assurance plan prior to
and installation can be found in groundwater and wells (20). selectionofthedrilling/pushboringmethod(s)tobeusedatthe
Environmental considerations include preservation of sample facility under investigation to assure the proper drilling and
representativeness for chemical contamination, aquifer sampling practices are used to meet specified project require-
integrity, and reduction in waste (IDW). Drilling/push boring ments.While some drilling/push boring practices may be more
methods that do not use fluids are most often used and time efficient if they yield non-representative samples then the
measures are taken given in 5.4.1 below. Direct push and sonic resulting geological, water quality and analytical results may
methods using no fluids and generate minimal waste (IDW) be inaccurate and misleading for the purposes of an environ-
and provide the borehole wall protection with casings. Direct mental investigation. This could result in the development of
D6286/D6286M − 20
an inaccurate (CSM) and remediation action, and significant an aquitard or impermeable confining layer of material is
lifetime cost increases to achieve site closure for contaminated drilled through, using any drilling/push boring method or a
facilities. combination thereof, the following technique is suggested,
particularly when drilling under saturated conditions. The
5.4.3 Dry Drilling/Push Boring Methods Preferred—
impermeablematerialshouldbedrilledintobutnotcompletely
Drilling/pushboringmethodsthatdonotuseadrillingfluidare
through. Casing should be installed into the impermeable
preferable because they preclude possible aquifer contamina-
material and pressure cemented/grouted into place with the use
tion from such fluids. Direct push methods for monitoring well
of centralizers. After the cement/grout has adequately cured,
installation minimize or preclude the use of drilling fluids.
the material remaining in the casing can be drilled out.
Other drilling methods that normally preclude the use of
Boreholegeophysicalmethods(see
D5753)thencanbeusedto
drilling fluids include hollow- and solid-stem auger drilling,
evaluate the seal between the borehole annulus and the wall of
hand auger drilling (only an effective shallow-drilling method
the casing. After an acceptable seal has resulted, drilling
whenusedtodrillabovethewatertable),bucketaugerdrilling,
completely through the confining layer can be done. Continue
resonant sonic-drilling method, and cable-percussion drilling
drilling/sampling/coring operations until the desired borehole
methods. Methods that normally require the use of a drilling
depth has been reached. If other confining layer(s) are to be
fluid for drilling include jet-wash and jet-percussion drilling,
drilled in the same borehole, the above technique(s) can be
reverse-circulationdrilling,andfluid-andair-rotarydrilling.In
followed. The next casing installed should be the next smaller
cases where drilling-fluid loss occurs during drilling, estimates
size to the previously-installed casing (21).
of the amounts of fluid loss and depth(s) of these occurrences
in the borehole should be documented. Drilling-fluid loss data 5.4.5 Casing advancers are often used in coarse grained
may be useful in planning well-development techniques to be depositsandweatherbedrock.Ifthetendencyofthismethodis
useduponcompletionoftheborehole.Anothercrucialfactorto to over ream the hole, contamination may move along the
be considered when evaluating this data is well-screen place- casingduringdrilling.Airrotarydrillingshouldnotbeusedfor
ment. most environmental investigations, especially when Volatile
Organic Compounds (VOCs) are under investigation or con-
5.4.3.1 Use of Dry drilling/Push Boring Methods Below the
taminants effected by changes in Oxidation Reduction Poten-
Water Table—Dry drilling/push boring methods such as direct
tial (ORP) are under investigation.Air rotary drilling can strip
push, sonic, and hollow-stem augers all suffer from problems
VOCs from the formation and groundwater resulting in low
when used below the water table, especially in sands which are
biased analytical data for environmental investigations.
the target aquifers for testing or well placement. Sand below
Additionally, air rotary drilling can and has contaminated
the water table can be unstable and heave into the casings. In
formations with compressor oils or VOCs present in the local
these cases, and if permitted, in the work plan water may have
ambient atmosphere. Air rotary drilling can also fracture the
to be added to stabilize water levels in the boring (5.4.1). The
surrounding ground mass if circulation is lost.
alternative is to retract casings which may have further
disturbance to the base of the boring.Any borings with casing 5.4.6 Ultimately, selection of a drilling/push boring method
left overnight will likely fill with groundwater to the level of from several possible methods must be made only after
the groundwater table and provisions may have to be made to weighing all of the advantages and disadvantages of each
remove this water via bailing or air lifting prior to well method against data-collection objectives. In some cases, a
installation or resumed sampling if required in the work plan. drilling/push boring method that minimizes the potential for
Alternately, the water in the casing may have to remain and subsurface contamination by the drilling process might limit
createabalancewiththeexistingaquiferduringtheresumption the types of other data that can be collected, for example,
of drilling activities. borehole-geophysical data (5.9), from the well. For example,
fluid-rotary drilling methods are good drilling methods to use
5.4.4 Use of Cased Methods—Drilling/push boring methods
for determining subsurface lithologic characterization because
that advance the casing as drilling proceeds are very effective
most borehole electric and sonic geophysical-logging tools
methods to minimize the effects of groundwater migration
require uncased fluid-filled boreholes
alongthecasingandcanmaintainsealacrossmultipleaquifers.
Dual tube direct push equipment, sonic drilling, casing ad- 5.4.7 Selection of a drilling method must consider all
vancer methods (10.3) and reverse circulation all advance aspects of monitoring-well installation, including casing mate-
casings continuously during the drilling process. Hollow-stem rials and composition, screen(s), subsurface monitoring equip-
augers provide a stable inner casing but allow mixing of soil ment and installation(s), grouting materials and placement
and water on the auger flights. Incremental open hole drilling procedure(s), as well as any other plans for well completion
and sampling such as fluid rotary drilling may require tele- and development. For example, when a drilling/push boring
scoped casing (5.4.4.1) to seal off multiple aquifer zones method is used that might affect groundwater chemistry, the
separated by confining units. well development required to remove artifacts of the drilling
can be intensive, time consuming, and affect water chemistry.
5.4.4.1 Sealing Across Aquifers in Open Hole Drilling –
Telescoping—The practice of incremental open hole drilling/ 5.4.8 The planning of the type(s) of drilling/push boring
push boring and sampling in uncased borings, using temporary equipment to be used on the project should include sampling
casings through separate aquifers, can result in cross- requirements and well-completion requirements consider-
contamination. To avoid or minimize the possibility of bore- ation(s).Forinstance,groutingandplacementofwellscreen(s)
hole cross-contamination or leakage from occurring whenever are common well-completion requirements, and the ability to
D6286/D6286M − 20
accomplish either of these is dependent greatly on the type of ing of the drilled materials if too high of drilling rate or
equipment used. The accomplishment of satisfactory hole- circulation pressure is applied.
abandonment procedures, as well as the ease at which any
5.6.2 Hydraulic Fracturing—Geotechnical drilling for wa-
drilling/push boring equipment can be decontaminated are also
terretaininghydraulicstructuressuchasdamsorleveesshould
important factors to be considered. It is standard procedure to becarefullyselectedtoavoidpotentialforhydraulicfracturing.
havetocleanequipmentpriortoentranceandexitfromthesite
Drilling methods using fluids or air have potential to hydrau-
as well as decontamination of sampling and installation equip- lically fracture soils if poor drilling practice or the formation
ment during drilling operations using procedures given in
leadstocirculationblockage.Forwaterretainingstructuresdry
D5088 and D5608. drilling methods such as hollow-stem augers or sonic drilling
are preferred and fluid and especially air drilling are to be
5.5 Drill Hole Diameter—Drilling depth and borehole di-
avoided. Air drilling has been banned in impervious cores of
ameters shown in Table 1 are nominal values for the method
dams (25).
and may vary for specific cases or conditions. Drill hole
5.7 Drilling Methods – Fluid/Water Drilling:
diameter is probably the most important consideration for
selection or drilling/push boring methods. 5.7.1 Fluid/water drilling methods are commonly used for
geotechnical boreholes and are often preferred for these
5.5.1 Geotechnical Considerations—Drill hole diameter di-
drilling programs. Conversely, fluid drilling is typically
rectly affects sample quality with larger diameters yielding
avoided when possible for environmental borings and moni-
higher quality samples using most all sampling methods,
toringwellinstallations.Drillingfluidscansignificantlyimpact
disturbed or intact. The majority of geotechnical work requires
thewaterqualityofthetestorinstallationlocationcausingbias
a minimum borehole inside diameter of 100 mm [4 in.] for
in basic water quality parameters such as specific conductance,
soils. Intact sampling of soils for laboratory testing are greatly
dissolved oxygen, pH and ORP conditions. Accurate determi-
improved by using 150 mm [6 in.] boreholes (D1587/
nation of these parameters can be vital to understanding the
D1587M). For rock coring, NQ3 is often used for mineralogi-
contaminantdegradationprocessesoccurringintheaquiferand
calinvestigationsbutthelargerHQ3andPQ3sizeyieldsbetter
to designing an effective remediation program. Additionally,
cores and allows for water testing.
drilling fluids can dilute the observed concentration of hazard-
5.5.2 Environmental Considerations—The diameter of the
ous contaminants present at the facility or accidentally add
borehole and the well casing for conventionally drilled filter
contaminants to the formation exacerbating the existing prob-
packed monitoring well should be selected so that a minimum
lem. The use of drilling fluids should be avoided for environ-
annular space of 2 in. [50 mm] is maintained between the
mental borings when possible.
inside diameter of the casing and outside diameter of the riser
5.7.2 Water without additives is not effective as a drilling
to provide working space for a tremie pipe (Practice D5092/
fluid for two reasons, first, it does not have any cuttings-
D5092M). Special procedures in D6724/D6724M and D6725/
carrying capacity, having a Test Method D6910/D6910M
D6725M address methods to place groundwater monitoring
Marsh-funnel viscosity of only 26 s, and secondly, it does not
wells in small diameter direct push equipment with much
possess any gel-strength properties for building a mud rind on
smaller annulus. Generally, environmental sampling does not
the borehole wall, allowing for borehole wall collapse, differ-
require physically intact samples where larger diameters are
ential sticking of the drill tools to the borehole wall, and
required. Direct push equipment has now reached capabilities
creation of “draining chimneys” due to fluid invasion and
with double tube system that exceed 100 mm [4 in.] inside
internal erosion of the borehole wall (26).Also, water contain-
diameters but often are used in smaller sizes.
ing only natural clays should not be used as a drilling mud.
5.6 Drilling – Damage by Poor Drilling Procedures – This fluid mixture, containing only natural clays and water,
Hydraulic Fracturing:
will make only a heavy, clay-laden fluid that will not have the
capacity (viscosity) to carry the drill cuttings up-hole and will
5.6.1 If drilling methods are not properly performed, poor
not make a thin mud rind on the borehole wall to inhibit its
quality samples, borehole damage, or poor-quality monitoring-
collapse (lack of gel strength). Instead, it will allow washouts
well installation(s) may result. It has been shown that improper
of the borehole wall, fluid and clay penetration into the
drilling, particularly when drilling in unconsolidated materials
borehole wall, and perhaps, cause differential sticking and loss
(soils), can cause borehole damage. Preferential seepage paths
of the drill tools in the borehole. Channeling and chimneys of
can be formed close to the borehole by washing fine particles
sand also can result in the borehole wall allowing preferential
and creating “draining chimneys” that can be very difficult to
seepage paths close to the borehole.
seal (22-24).Drillingdamagestotheboreholeusuallyaremore
severe in boreholes drilled in unconsolidated materials than 5.7.3 When using a drilling method that requires use of a
those occurring in boreholes drilled in consolidated materials drilling fluid, it is recommended that a controlled drilling-fluid
(rock).Although documentation of these occurrences is rare, it program be employed in order to minimize possible drilling-
doesoccur.Occurrencesofthisnatureareprobablyduetopoor fluid invasion effects on the borehole and cores obtained (26).
drilling-fluid control, poor drilling practice by an inexperi- Auger drilling tends to smear fine-grained sediment cuttings
enced driller. Damage
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6286 − 19 D6286/D6286M − 20
Standard Guide for
Selection of Drilling and Direct Push Methods for
Geotechnical and Environmental Subsurface Site
Characterization
This standard is issued under the fixed designation D6286;D6286/D6286M; the number immediately following the designation indicates
the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This guide provides descriptions of various methods for site characterization along with advantages and disadvantages
associated with each method discussed. This guide is intended to aid in the selection of drilling method(s) for geotechnical and
environmental soil and rock borings for sampling, testing, and installation of wells, or other instrumentation. It does not address
drilling for foundation improvement, drinking water wells, or special horizontal drilling techniques for utilities.
1.2 This guide cannot address all possible subsurface conditions that may occur such as, geologic, topographic, climatic, or
anthropogenic. Site evaluation for engineering, design, and construction purposes is addressed in Guide D420. Soil and rock
sampling in drill holes is addressed in Guide D6169D6169/D6169M. Pertinent guides and practices addressing specific drilling
methods, equipment, and procedures are listed in Section 2. Guide D5730 provides information on most all aspects of
environmental site characterization.
1.3 The values stated in either SI units or inch-pound units (given in brackets) 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 nonconformance with the standard.
1.4 This guide does not purport to comprehensively address all methods and the issues associated with drilling for geotechnical
and environmental purposes. Users should seek qualified professionals for decisions as to the proper equipment and methods that
would be most successful for their site investigation. Other methods may be available for these methods and qualified professionals
should have flexibility to exercise judgment as to possible alternatives not covered in this guide. The guide is current at the time
of issue, but new alternative methods may become available prior to revisions. Therefore, users should consult with manufacturers
or producers prior to specifying program requirements.
1.5 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.
1.5.1 Drilling operators generally are required to be trained for safety requirements such as those of construction and
environmental occupational safety programs dictated by country, regional, or local requirements such as the US. OSHA training
programs. Drilling safety programs are also available from the National Drilling Association (NDA4U.com) or other country
drilling associations.
1.6 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 and 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.
1.7 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.
This guide is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.21 on Groundwater and Vadose
Zone Investigations.
Current edition approved Oct. 1, 2019May 1, 2020. Published November 2019May 2020. Originally approved in 1998. Last previous edition approved in 20122019 as
D6286 – 12.D6286 – 19. DOI: 10.1520/D6286-19.10.1520/D6286_D6286M-20.
“Drilling Safety Guide,” National Drilling Federation, Columbia, SC, 1985, p. 36.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6286/D6286M − 20
2. Referenced Documents
2.1 ASTM Standards:
D420 Guide for Site Characterization for Engineering Design and Construction Purposes
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D1452D1452/D1452M Practice for Soil Exploration and Sampling by Auger Borings
D2113 Practice for Rock Core Drilling and Sampling of Rock for Site Exploration
D2488 Practice for Description and Identification of Soils (Visual-Manual Procedures)
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in
Engineering Design and Construction
D5088 Practice for Decontamination of Field Equipment Used at Waste Sites
D5092D5092/D5092M Practice for Design and Installation of Groundwater Monitoring Wells
D5608 Practices for Decontamination of Sampling and Non Sample Contacting Equipment Used at Low Level Radioactive
Waste Sites
D5730 Guide for Site Characterization for Environmental Purposes With Emphasis on Soil, Rock, the Vadose Zone and
Groundwater (Withdrawn 2013)
D5753 Guide for Planning and Conducting Geotechnical Borehole Geophysical Logging
D5778 Test Method for Electronic Friction Cone and Piezocone Penetration Testing of Soils
D5781D5781/D5781M Guide for Use of Dual-Wall Reverse-Circulation Drilling for Geoenvironmental Exploration and the
Installation of Subsurface Water Quality Monitoring Devices
D5782 Guide for Use of Direct Air-Rotary Drilling for Geoenvironmental Exploration and the Installation of Subsurface
Water-Quality Monitoring Devices
D5783 Guide for Use of Direct Rotary Drilling with Water-Based Drilling Fluid for Geoenvironmental Exploration and the
Installation of Subsurface Water-Quality Monitoring Devices
D5784 Guide for Use of Hollow-Stem Augers for Geoenvironmental Exploration and the Installation of Subsurface Water
Quality Monitoring Devices
D5872 Guide for Use of Casing Advancement Drilling Methods for Geoenvironmental Exploration and Installation of
Subsurface Water Quality Monitoring Devices
D5875D5875/D5875M Guide for Use of Cable-Tool Drilling and Sampling Methods for Geoenvironmental Exploration and
Installation of Subsurface Water Quality Monitoring Devices
D5876D5876/D5876M Guide for Use of Direct Rotary Wireline Casing Advancement Drilling Methods for Geoenvironmental
Exploration and Installation of Subsurface Water-Quality Monitoring Devices
D6001 Guide for Direct-Push Groundwater Sampling for Environmental Site Characterization
D6151D6151/D6151M Practice for Using Hollow-Stem Augers for Geotechnical Exploration and Soil Sampling
D6169D6169/D6169M Guide for Selection of Soil and Rock Sampling Devices Used With Drill Rigs for Environmental
Investigations
D6429 Guide for Selecting Surface Geophysical Methods (Withdrawn 2020)
D6910D6910/D6910M Test Method for Marsh Funnel Viscosity of Construction Slurries
D6914D6914/D6914M Practice for Sonic Drilling for Site Characterization and the Installation of Subsurface Monitoring
Devices
2.2 Geotechnical Sampling, In situ Testing, and Instrumentation in Drill Holes:
D1586D1586/D1586M Test Method for Standard Penetration Test (SPT) and Split-Barrel Sampling of Soils
D1587D1587/D1587M Practice for Thin-Walled Tube Sampling of Fine-Grained Soils for Geotechnical Purposes
D2573/D2573M Test Method for Field Vane Shear Test in Saturated Fine-Grained Soils
D3550D3550/D3550M Practice for Thick Wall, Ring-Lined, Split Barrel, Drive Sampling of Soils
D4403 Practice for Extensometers Used in Rock
D4428D4428/D4428M Test Methods for Crosshole Seismic Testing
D4719 Test Methods for Prebored Pressuremeter Testing in Soils
D6519 Practice for Sampling of Soil Using the Hydraulically Operated Stationary Piston Sampler
D6598 Guide for Installing and Operating Settlement Points for Monitoring Vertical Deformations
D6635 Test Method for Performing the Flat Plate Dilatometer
D7299 Practice for Verifying Performance of a Vertical Inclinometer Probe
2.3 Sampling, Testing, and Installations in Drill Holes:
D4700 Guide for Soil Sampling from the Vadose Zone
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
D6286/D6286M − 20
D4044/D4044M Test Method for (Field Procedure) for Instantaneous Change in Head (Slug) Tests for Determining Hydraulic
Properties of Aquifers
D4050 Test Method for (Field Procedure) for Withdrawal and Injection Well Testing for Determining Hydraulic Properties of
Aquifer Systems
D4630 Test Method for Determining Transmissivity and Storage Coefficient of Low-Permeability Rocks by In Situ
Measurements Using the Constant Head Injection Test
D6282D6282/D6282M Guide for Direct Push Soil Sampling for Environmental Site Characterizations
D6724/D6724M Guide for Installation of Direct Push Groundwater Monitoring Wells
D6725/D6725M Practice for Direct Push Installation of Prepacked Screen Monitoring Wells in Unconsolidated Aquifers
D6907 Practice for Sampling Soils and Contaminated Media with Hand-Operated Bucket Augers
D7242D7242/D7242M Practice for Field Pneumatic Slug (Instantaneous Change in Head) Tests to Determine Hydraulic
Properties of Aquifers with Direct Push Groundwater Samplers
D7352 Practice for Volatile Contaminant Logging Using a Membrane Interface Probe (MIP) in Unconsolidated Formations with
Direct Push Methods
D7648D7648/D7648M Practice for Active Soil Gas Sampling for Direct Push or Manual-Driven Hand-Sampling Equipment
D8037D8037/D8037M Practice for Direct Push Hydraulic Logging for Profiling Variations of Permeability in Soils
3. Terminology
3.1 Definitions:
3.1.1 For definitions of common technical terms used within this guide, refer to Terminology D653.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 borehole wall, n—refers to the naturally-occurring soil(s)/rock(s) surrounding the borehole.
3.2.2 kelly bar, n—in drilling, a formed or machined section of hollow drill steel used in rotary drilling, which is joined directly
to the swivel at the top and to the drill pipe below.
3.2.2.1 Discussion—
The flats or splines of the kelly bar engage the rotary table so that the rotation of the rotary table turns the kelly bar, which in turn,
rotates the drill pipe and the rotary bit.
3.2.3 mud rings, n—in drilling, soil or rock cuttings that form a ring or rings on the drill rod(s) during a rotary-drilling method,
and as such, prevent drill cuttings from being carried up and out of the borehole.
3.2.3.1 Discussion—
These rings can cause drill rods to become stuck in the borehole if sufficient drilling fluid is not injected or pumped downhole to
keep the cuttings fluid so that the ring(s) cannot form on the drill rods and block the cuttings return as drilling progresses.
3.2.4 orange-peel bucket, n—in drilling, a bucket-type device, somewhat elliptical in shape resembling an orange peel, that is
lowered down the borehole and used to remove boulders from the bottom of a borehole.
3.2.5 unconsolidated geologic materials, n—in groundwater, geology, or hydrogeology, a loosely aggregated solid (particulate)
material of geologic origin (soil, sediments, etc.).
3.2.5.1 Discussion—
Groundwater hydrologists, and geologists, use the terms unconsolidated formations, deposits, sediments, units, materials, etc., to
refer to the general term “soil” including other soils (alluvium, glacial till, etc.) as defined in D653. These terms are often found
in groundwater standards applied to aquifers. Unconsolidated materials are non-lithified, typically lacking cementation of
individual particles (clay, silt sand, gravel, etc.). The term “unconsolidated” should not be confused with geotechnical terms of the
degree of soil consolidation (over, normally, under-consolidated) as defined in D653.
4. Significance and Use
4.1 The 1998 edition of this standard was written solely for selection of drilling methods for environmental applications and
specifically for installation of groundwater monitoring wells. The second revision was made to include geotechnical applications
since many of the advantages, disadvantages, and limitations discussed extensively throughout this document also apply to
geotechnical design use such as data collection (sampling and in-situ testing) for construction design and instrumentation. Besides
installation of monitoring wells (D5092D5092/D5092M, D6724/D6724M), Environmental investigations are also made for
sampling, in-situ testing, and installation of aquifer testing boreholes (D4044/D4044M, D4050).
D6286/D6286M − 20
4.2 There are other guides for geotechnical investigations addressing drilling methods such as in Eurocode (1, 2) , U.S. Federal
Highway Administration, (3, 4), U.S. Army Corps of Engineers, (5), and U.S. Bureau of Reclamation (6, 7). An authoritative
Handbook on Environmental Site Characterization and Ground-Water Monitoring was compiled by Nielsen (8) which addresses
drilling methods in detail including the advent of Direct Push methods developed for environmental investigations. Two other
major drilling guides have been written by the National Drilling Association (9) and from the Australia Drilling Industry Training
Committee (10) and these guides are user for the drillers.
4.3 Table 1 lists sixteen classes of methods addressed in this guide. The selection of particular method(s) for drilling/push boring
requires that specific characteristics of each site be considered. This guide is intended to make the user aware of some of the various
drilling/push boring methods available and the applications, advantages, and disadvantages of each with respect to determining
geotechnical and environmental exploration.
4.3.1 On Table 1, practically all methods allow for coring, but some are much more efficient than others. Some drilling systems
such as hollow-stem augers or wireline coring allow for practically continuous coring with minimal time for switching barrels
while other drilling methods require the whole drilling equipment be removed from the hole. A prime example is the rate of rock
coring using fluid rotary and conventional core barrels versus wireline rock coring. Wireline line rock coring is fast with long
TABLE 1 Drilling Selection Guide
Typical
Type of Typical Range of Coring
Drilling Casing Samples Reference
Drilling Method Material Depth, Borehole Possible
B
Fluid Advance Obtainable Section
A C
Drilled in m [ft] Sizes, in (see 4.3.1)
cm [in.]
Power auger none, water, soil, weathered
yes <45 [150] 12.7-55 [5-22] S, F Yes(c) 6.2
(Hollow-stem) mud rock
Power auger soil, weathered
none no <45 [150] 5-25 [2-10] S Yes(i) 6.3
(Solid-stem) rock
none, water
soil, weathered
Power bucket auger (below water no <45 [150] 45-120 [18-48] S Yes(i) 6.4
rock
table)
<20 [70] (above
Hand auger none no soil 5-15 [2-6] S Yes(i) 6.5
water table only)
Direct fluid rotary water, mud yes soil, rock >300 [1000] 5-90 [2-36] S, R Yes(i) 7
none, water, soil, rock,
Sonic (vibratory) yes <150 [500] 10-30 [4-12] S, R, F Yes(c) 8
mud, air boulders
Typical 15-30
soil, weathered [50-100]
Direct-push technology none yes 3.8-15 [1.5-6] S, F Yes(c) 9
rock Maximum
60 [200]
Air rotary, soil, rock,
air, water, mud yes <600 [2000] 5-40 [2-16] S, R, F Yes(c) 10.3
Casing-advancer boulders
Reverse circulation,
air, water, foam yes soil, rock >300 [1000] 30-90 [12-36] S, R, F Yes(i) 12
air rotary
Reverse circulation,
water, mud yes soil, rock <600 [2000] 30-90 [12-36] S, R, F Yes(i) 12.3
fluid rotary
S, R, F (F–below
Cable tool water yes soil, rock <1500 [5000] 10-60 [4-24] Yes(i) 13
water table)
Jet percussion water no soil <15.0 [50] 5-10 [2-4] S no 14
Jetting water yes soil <15 [50] 10 [4] S no 14
A
Actual achievable drilled depths will vary depending on the ambient geohydrologic conditions existing at the site and size of drilling/push boring equipment used. For
example, large, high-torque rigs can drill to greater depths than their smaller counterparts under favorable site conditions. Boreholes drilled using air/air foam can reach
greater depths more efficiently using two-stage positive-displacement compressors having the capability of developing working pressures of 12 to 17 kPa [250 to 350 psi]
and 14 to 21 m /h [500 to 750 cfm], particularly when submergence requires higher pressures. The smaller rotary-type compressors only are capable of producing a
maximum working pressure of 6 kPa [125 psi] and produce 14 to 34 m /h [500 to 1200 cfm]. Likewise, the rig mast must be constructed to safely carry the anticipated
working loads expected. To allow for contingencies, it is recommended that the rated capacity of the mast be at least twice the anticipated weight load or normal pulling
load.
B
Soil = S (Cuttings), Rock = R (Cuttings), Fluid = F (some samples might require accessory sampling devices to obtain).
C
I = Incremental sampling, C = continuous sampling.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
D6286/D6286M − 20
continuous runs whereas fluid rotary requires more “trip time” to add and remove shorter length core barrels using drill rods. Table
1 delineates methods where coring is possible, and in general, by either continuous (c) or incremental (i) sampling.
4.3.2 Sampling for environmental contaminants in soil, unconsolidated formations or groundwater often requires special
considerations. In many environmental applications the use of drilling fluids (air, water, mud or foam) is often discouraged or even
prohibited as these fluids may dilute the analytes of interest or even introduce analytes of concern not previously present (see 5.4).
4.4 This guide is most often used in conjunction with Guide D6169D6169/D6169M on soil and rock sampling because sampling
is the primary activity during drilling/push borings. There are several guides that deal with individual drilling methods (see Guides
D5781D5781/D5781M, D5782, D5783, D5784, D5872, D5875D5875/D5875M, and D5876D5876/D5876M) and how to the
complete them for water quality monitoring well installations (see Practice D5092D5092/D5092M). Practices on hollow-stem
auger (D6151D6151/D6151M) and sonic drilling (D6914D6914/D6914M) were written for both geotechnical and environmental
purposes and address sampling methods. Practice D2113 on rock core drilling includes sampling methods.
4.4.1 This guide covers direct push methods that are only used to make open holes for testing and sampling. This most often
accomplished using dual tube systems and using the tubes for access of the subsurface for water sampling, D6001, soil sampling
(D6282D6282/D6282M), well installation (D6724/D6724M, D6725/D6725M) and aquifer testing (D7242D7242/D7242M).
4.5 Predominant or Typical Drilling/Push Boring Methods Used for Geotechnical and Environmental Applications:
4.5.1 Geotechnical Investigations in Soils (unconsolidated deposits)—The most commonly used drilling methods for
geotechnical exploration are fluid rotary drilling when groundwater is present. Hollow-stem auger drilling is also frequently used
especially in arid regions where introduction of fluids is to be avoided in unsaturated soils.
4.5.2 Environmental Investigations in soils (unconsolidated deposits)—Most of these investigations are focused on soil
contamination or, groundwater quality investigations so introduction of drilling fluids is not desirable and methods which generate
minimal waste are highly favored. Direct Push methods were developed because they develop minimal investigative derived waste
(IDW). Sonic methods are frequently used and generate minimal IDW but large cores. Hollow-stem augers and fluid rotary are
used yet they generate large amounts of IDW.
4.5.2.1 At most environmental sites hazardous contaminants are present in the subsurface. Because of this fact any drill cuttings
or drilling fluids returned to the surface should be properly handled, contained and stored (drums or roll-off bins, etc.) for sampling
and laboratory analysis. Laboratory analyses may be required to verify that hazardous contaminants are not present above
regulatory action levels prior to proper disposal. If concentrations of hazardous chemicals in cuttings or waste drilling fluids exceed
regulatory action levels the waste may require treatment before disposal or may need to be properly disposed in a hazardous waste
landfill. Review pertinent regulations before drilling/push boring to maintain compliance. The generation of contaminated waste
drill cuttings and fluids significantly increase the potential for worker exposure to hazardous contaminants. Review pertinent
regulations (such as OSHA 1910.120, etc.) to maintain compliance with worker safety and monitoring requirements.
4.5.3 Rock, Weathered Rock, and Coarse Cobble Boulder Drilling—Wireline rock coring is used in competent rock and results
in the best core recovery. For coarse grained unconsolidated deposits and weathered bedrock samples are very difficult to recover
and, rotary air drill through drive casing advancers are often used and require larger drills. Larger sonic drills can also drill and
recover rock and boulder formations.
4.5.4 Sonic drilling methods have increased in use for both geotechnical and environmental explorations. The method offers
very rapid continuous coring with the ability to drill difficult formations with large diameter equipment.
4.5.5 Shallow hand auger (D4700) is used for both disciplines but in most cases hand applications are used as part of initial site
surveys prior to drilling/push boring or just for characterization of shallow soil sampling. Hand auguring is very labor intensive
and has almost been abandoned in favor of using direct push equipment.
NOTE 1—The reliability of data and interpretations generated by this practice 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 generally are considered capable of competent testing.
Users of this practice are cautioned that compliance with Practice D3740 does not assure reliable testing. Reliable testing depends on several factors and
Practice D3740 provides a means of evaluating some of these factors.
Practice D3740 was developed for agencies engaged in the testing, inspection, or both, of soils and rock. As such, it is not totally applicable to agencies
performing these field practices. Users of this test method should recognize that the framework of Practice D3740 is appropriate for evaluating the quality
of an agency performing drilling. Currently, there is no known qualifying national authority that inspects agencies that perform this test method. There
is training and certification for drillers that are normally required for critical installations such as water well drilling (NGWA, NDA).
5. Program Planning and Drilling/Push Boring Considerations
5.1 All factors affecting both surface and subsurface environment at a specific site requires professional judgment and must be
considered by the geologist/hydrologist or experienced driller before a drilling/push boring method is selected. Development of
a Conceptual Site Model (CSM) of significant soil and rock masses and groundwater conditions within a given site should be
described and defined, both vertically and horizontally, before drilling. Site planning requires a reconnaissance site investigation
that considers access to the site and conditions for setting up the drilling/push boring equipment (1-8). The extent of site
characterization and specific methods used will be determined by study objectives. Study objectives also will affect the type and
complexity of data collected. Sources of data that may be useful during initial site evaluation include, but are not limited to,
topographic maps, aerial photography, satellite imagery, information from reconnaissance drilling/push borings, borehole
geophysical-log data, geologic maps and reports, statewide or county soil surveys, water-resource reports, well databases, and
D6286/D6286M − 20
mineral-resource surveys covering the proposed project area. Available reports of surface and subsurface investigations of nearby
or adjacent projects should be considered and the information applicable to the current project evaluated and applied if determined
reliable and beneficial. At any site review nearby, available borings and discuss drilling/push boring methods with local contractors
experienced with the geologic conditions.
5.2 Once the desk studies and field reconnaissance are performed, onsite explorations are normally phased using subsurface
screening methods to refine the CSM before final selection of drill hole locations. Site-specific surface geophysical surveys
(D6429) (11-15), direct-push soil or water sampling (D6282D6282/D6282M, D6001), hydraulic profiling (D8037D8037/
D8037M), cone penetrometers (D5778), dynamic cone penetrometers, or solid stem power augers (D1452D1452/D1452M) can be
performed in grid patterns across the site to refine the stratigraphy of the geology at the site and may detect problem areas for
targeting with drilling/push boring and sampling. Surface geophysical methods, such as seismic surveys and electrical-resistivity
imaging and electromagnetic-conductance surveys, can be valuable particularly when distinct differences in the properties of
contiguous subsurface materials are indicated (16, 17). When free product petroleum fuels are present in the subsurface, membrane
interface probe (D7352), or high-resolution fluorescence logging with induced fluorescence or optical image probes can be used
to identify depths and locations to target for sampling by drilling/push boring methods (18, 19).
5.2.1 The odds of detecting certain critical geologic features of interest on large sites are greatly improved using screening
methods prior to drilling/push boring and can be used to reduce the amount of expensive drill holes. Fig. 1 shows the number of
drill holes and the probability of detecting several types of geologic features at a 260 ha [640-acre, 1 square mile] site (8). Without
screening methods using geophysics and low-cost probing or drilling/push boring methods, some geologic features could be totally
missed even with 100 drill holes. Further, the screening methods can be used to reduce the amount of drill holes and target them
on critical layers.
5.3 Geotechnical Considerations—Drilling/push boring activities for geotechnical investigations include sampling (both
disturbed or intact for laboratory testing), in situ testing, and installation of monitoring devices such as piezometers (observation
wells), or inclinometers (see ASTM procedures cited in 2.2). Ideal drilling/push boring methods often are dictated by soil or rock
types and the likelihood of the method to disturb soils ahead of the drilling operation, but more importantly is the presence of
groundwater. Fluid rotary drilling predominates in humid areas with shallow groundwater, whereas in arid areas, the hollow-stem
auger is more commonly used. With unsaturated soils in arid regions it may not be desirable to use fluid drilling methods that could
wet soil samples prematurely ahead of laboratory testing of samples. A common drilling/push boring test is the standard penetration
test (D1586D1586/D1586M) and only certain drilling/push boring methods are suitable. When drilling in hydraulic structures such
as dams and levees, drill methods should be selected that minimize the potential for hydraulic fracturing (see 5.6.2). Air drilling
should not be used in impervious cores of dams and levees.
The probability of finding many types of subsurface geologic features using borings alone is fairly low. The use of supportive studies such as surface geologic mapping,
aerial photo interpretation, and surface and borehole geophysics can greatly improve the chances of successfully mapping the subsurface. Without a complete and
accurate map of the subsurface, site models can be misleading.
FIG. 1 Probability of Finding Geologic Features Using Only Drill Holes on a Large Site (8)
D6286/D6286M − 20
5.4 Environmental Considerations—Environmental drilling/push boring is primarily for the collection of samples and
installation of groundwater monitoring wells (see standards listed in 2.3). An authoritative reference for well drilling and
installation can be found in groundwater and wells (20). Environmental considerations include preservation of sample
representativeness for chemical contamination, aquifer integrity, and reduction in waste (IDW). Drilling/push boring methods that
do not use fluids are most often used and measures are taken given in 5.4.1 below. Direct push and sonic methods using no fluids
and generate minimal waste (IDW) and provide the borehole wall protection with casings. Direct push equipment has the potential
to perform many different in-situ tests as drilling progresses (2.3). Groundwater monitoring wells using drilling/push boring
methods in this standard are designed and installed in accordance with D5092D5092/D5092M and direct push wells are installed
with accordance with ASTM D6724/D6724M and D6725/D6725M for prepacked wells.
5.4.1 If the monitoring well also is to be sampled for water quality during the fluid drilling process, the possible damage and
subsequent aquifer contamination caused by drilling-fluid invasion of the borehole wall that may occur during drilling must be
considered. Drilling-fluid invasion of the borehole wall normally results from the use of a poorly-controlled and improperly-
designed drilling-fluid program. Drill fluids are designed to coat and partially penetrate the wall of the drill hole to stabilize the
boring. Water used as a drilling fluid or to prepare drilling muds must be tested to verify it is clean and free of the contaminants
of interest or other potential contaminants not present at the site. Often, municipal water is chlorinated and as such could contain
trihalomethanes which are regulated contaminants in groundwater.
5.4.2 The project manager should review the project work plan, sampling plan and quality assurance plan prior to selection of
the drilling/push boring method(s) to be used at the facility under investigation to assure the proper drilling and sampling practices
are used to meet specified project requirements. While some drilling/push boring practices may be more time efficient if they yield
non-representative samples then the resulting geological, water quality and analytical results may be inaccurate and misleading for
the purposes of an environmental investigation. This could result in the development of an inaccurate (CSM) and remediation
action, and significant lifetime cost increases to achieve site closure for contaminated facilities.
5.4.3 Dry Drilling/Push Boring Methods Preferred—Drilling/push boring methods that do not use a drilling fluid are preferable
because they preclude possible aquifer contamination from such fluids. Direct push methods for monitoring well installation
minimize or preclude the use of drilling fluids. Other drilling methods that normally preclude the use of drilling fluids include
hollow- and solid-stem auger drilling, hand auger drilling (only an effective shallow-drilling method when used to drill above the
water table), bucket auger drilling, resonant sonic-drilling method, and cable-percussion drilling methods. Methods that normally
require the use of a drilling fluid for drilling include jet-wash and jet-percussion drilling, reverse-circulation drilling, and fluid- and
air-rotary drilling. In cases where drilling-fluid loss occurs during drilling, estimates of the amounts of fluid loss and depth(s) of
these occurrences in the borehole should be documented. Drilling-fluid loss data may be useful in planning well-development
techniques to be used upon completion of the borehole. Another crucial factor to be considered when evaluating this data is
well-screen placement.
5.4.3.1 Use of Dry drilling/Push Boring Methods Below the Water Table—Dry drilling/push boring methods such as direct push,
sonic, and hollow-stem augers all suffer from problems when used below the water table, especially in sands which are the target
aquifers for testing or well placement. Sand below the water table can be unstable and heave into the casings. In these cases, and
if permitted, in the work plan water may have to be added to stabilize water levels in the boring (5.4.1). The alternative is to retract
casings which may have further disturbance to the base of the boring. Any borings with casing left overnight will likely fill with
groundwater to the level of the groundwater table and provisions may have to be made to remove this water via bailing or air lifting
prior to well installation or resumed sampling if required in the work plan. Alternately, the water in the casing may have to remain
and create a balance with the existing aquifer during the resumption of drilling activities.
5.4.4 Use of Cased Methods—Drilling/push boring methods that advance the casing as drilling proceeds are very effective
methods to minimize the effects of groundwater migration along the casing and can maintain seal across multiple aquifers. Dual
tube direct push equipment, sonic drilling, casing advancer methods (10.3) and reverse circulation all advance casings continuously
during the drilling process. Hollow-stem augers provide a stable inner casing but allow mixing of soil and water on the auger
flights. Incremental open hole drilling and sampling such as fluid rotary drilling may require telescoped casing (5.4.4.1) to seal off
multiple aquifer zones separated by confining units.
5.4.4.1 Sealing Across Aquifers in Open Hole Drilling – Telescoping—The practice of incremental open hole drilling/push
boring and sampling in uncased borings, using temporary casings through separate aquifers, can result in cross-contamination. To
avoid or minimize the possibility of borehole cross-contamination or leakage from occurring whenever an aquitard or impermeable
confining layer of material is drilled through, using any drilling/push boring method or a combination thereof, the following
technique is suggested, particularly when drilling under saturated conditions. The impermeable material should be drilled into but
not completely through. Casing should be installed into the impermeable material and pressure cemented/grouted into place with
the use of centralizers. After the cement/grout has adequately cured, the material remaining in the casing can be drilled out.
Borehole geophysical methods (see D5753) then can be used to evaluate the seal between the borehole annulus and the wall of
the casing. After an acceptable seal has resulted, drilling completely through the confining layer can be done. Continue
drilling/sampling/coring operations until the desired borehole depth has been reached. If other confining layer(s) are to be drilled
in the same borehole, the above technique(s) can be followed. The next casing installed should be the next smaller size to the
previously-installed casing (21).
D6286/D6286M − 20
5.4.5 Casing advancers are often used in coarse grained deposits and weather bedrock. If the tendency of this method is to over
ream the hole, contamination may move along the casing during drilling. Air rotary drilling should not be used for most
environmental investigations, especially when Volatile Organic Compounds (VOCs) are under investigation or contaminants
effected by changes in Oxidation Reduction Potential (ORP) are under investigation. Air rotary drilling can strip VOCs from the
formation and groundwater resulting in low biased analytical data for environmental investigations. Additionally, air rotary drilling
can and has contaminated formations with compressor oils or VOCs present in the local ambient atmosphere. Air rotary drilling
can also fracture the surrounding ground mass if circulation is lost.
5.4.6 Ultimately, selection of a drilling/push boring method from several possible methods must be made only after weighing
all of the advantages and disadvantages of each method against data-collection objectives. In some cases, a drilling/push boring
method that minimizes the potential for subsurface contamination by the drilling process might limit the types of other data that
can be collected, for example, borehole-geophysical data (5.9), from the well. For example, fluid-rotary drilling methods are good
drilling methods to use for determining subsurface lithologic characterization because most borehole electric and sonic
geophysical-logging tools require uncased fluid-filled boreholes
5.4.7 Selection of a drilling method must consider all aspects of monitoring-well installation, including casing materials and
composition, screen(s), subsurface monitoring equipment and installation(s), grouting materials and placement procedure(s), as
well as any other plans for well completion and development. For example, when a drilling/push boring method is used that might
affect groundwater chemistry, the well development required to remove artifacts of the drilling can be intensive, time consuming,
and affect water chemistry.
5.4.8 The planning of the type(s) of drilling/push boring equipment to be used on the project should include sampling
requirements and well-completion requirements consideration(s). For instance, grouting and placement of well screen(s) are
common well-completion requirements, and the ability to accomplish either of these is dependent greatly on the type of equipment
used. The accomplishment of satisfactory hole-abandonment procedures, as well as the ease at which any drilling/push boring
equipment can be decontaminated are also important factors to be considered. It is standard procedure to have to clean equipment
prior to entrance and exit from the site as well as decontamination of sampling and installation equipment during drilling operations
using procedures given in D5088 and D5608.
5.5 Drill Hole Diameter—Drilling depth and borehole diameters shown in Table 1 are nominal values for the method and may
vary for specific cases or conditions. Drill hole diameter is probably the most important consideration for selection or drilling/push
boring methods.
5.5.1 Geotechnical Considerations—Drill hole diameter directly affects sample quality with larger diameters yielding higher
quality samples using most all sampling methods, disturbed or intact. The majority of geotechnical work requires a minimum
borehole inside diameter of 100 mm [4 in.] for soils. Intact sampling of soils for laboratory testing are greatly improved by using
150 mm [6 in.] boreholes (D1587D1587/D1587M). For rock coring, NQ3 is often used for mineralogical investigations but the
larger HQ3 and PQ3 size yields better cores and allows for water testing.
5.5.2 Environmental Considerations—The diameter of the borehole and the well casing for conventionally drilled filter packed
monitoring well should be selected so that a minimum annular space of 2 in. [50 mm] is maintained between the inside diameter
of the casing and outside diameter of the riser to provide working space for a tremie pipe (Practice D5092D5092/D5092M). Special
procedures in D6724/D6724M and D6725/D6725M address methods to place groundwater monitoring wells in small diameter
direct push equipment with much smaller annulus. Generally, environmental sampling does not require physically intact samples
where larger diameters are required. Direct push equipment has now reached capabilities with double tube system that exceed 100
mm [4 in.] inside diameters but often are used in smaller sizes.
5.6 Drilling – Damage by Poor Drilling Procedures – Hydraulic Fracturing:
5.6.1 If drilling methods are not properly performed, poor quality samples, borehole damage, or poor-quality monitoring-well
installation(s) may result. It has been shown that improper drilling, particularly when drilling in unconsolidated materials (soils),
can cause borehole damage. Preferential seepage paths can be formed close to the borehole by washing fine particles and creating
“draining chimneys” that can be very difficult to seal (22-24). Drilling damages to the borehole usually are more severe in
boreholes drilled in unconsolidated materials than those occurring in boreholes drilled in consolidated materials (rock). Although
documentation of these occurrences is rare, it does occur. Occurrences of this nature are probably due to poor drilling-fluid control,
poor drilling practice by an inexperienced driller. Damage can occur by drilling too hastily, and by use of incorrect speeds,
pressures, and other variables controlled by the driller. Any drilling method using a circulating media to control cuttings removal
can cause hydraulic fracturing of the drilled materials if too high of drilling rate or circulation pressure is applied.
5.6.2 Hydraulic Fracturing—Geotechnical drilling for water retaining hydraulic structures such as dams or levees should be
carefully selected to avoid potential for hydraulic fracturing. Drilling methods using fluids or air have potential to hydraulically
fracture soils if poor drilling practice or the formation leads to circulation blockage. For water retaining structures dry drilling
methods such as hollow-stem augers or sonic drilling are preferred and fluid and especially air drilling are to be avoided. Air
drilling has been banned in impervious cores of dams (25).
5.7 Drilling Methods – Fluid/Water Drilling:
5.7.1 Fluid/water drilling methods are commonly used for geotechnical boreholes and are often preferred for these drilling
programs. Conversely, fluid drilling is typically avoided when possible for environmental borings and monitoring well
D6286/D6286M − 20
installations. Drilling fluids can significantly impact the water quality of the test or installation location causing bias in basic water
quality parameters such as specific conductance, dissolved oxygen, pH and ORP conditions. Accurate determination of these
parameters can be vital to understanding the contaminant degradation processes occurring in the aquifer and to designing an
effective remediation program. Additionally, drilling fluids can dilute the observed concentration of hazardous contaminants
present at the facility or accidentally add contaminants to the formation exacerbating the existing problem. The use of drilling fluids
should be avoided for environmental borings when possible.
5.7.2 Water without additives is not effective as a drilling fluid for two reasons, first, it does not have any cuttings-carrying
capacity, having a Test Method D6910D6910/D6910M Marsh-funnel viscosity of only 26 s, and secondly, it does not possess any
gel-strength properties for building a mud rind on the borehole wall, allowing for borehole wall collapse, differential sticking of
the drill tools to the borehole wall, and creation of “draining chimneys” due to fluid invasion and internal erosion of the borehole
wall (26). Also, water containing only natural
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