ASTM D5978/D5978M-16(2024)

Standard Guide for Maintenance and Rehabilitation of Groundwater Monitoring Wells

SIGNIFICANCE AND USE
4.1 The process of operating any engineered system, such as monitoring wells, includes active maintenance to prevent, mitigate, or reverse deterioration. Lack of or improper maintenance can lead to well performance deficiencies (physical problems) or sample quality degradation (chemical problems). These problems are intrinsic to monitoring wells, which are often left idle for long periods of time (as long as a year), installed in non-aquifer materials, and installed to evaluate contamination that can cause locally anomalous hydrogeochemical conditions. The typical solutions for these physical and chemical problems that would be applied by owners and operators of water supply, dewatering, recharge, and other wells may not be appropriate for monitoring wells because of the need to minimize their impact on the conditions that monitoring wells were installed to evaluate.  
4.2 This guide covers actions and procedures, but is not an encyclopedic guide to well maintenance. Well maintenance planning and execution is highly site and well specific.  
4.3 The design of maintenance and rehabilitation programs and the identification of the need for rehabilitation should be based on objective observation and testing, and by individuals knowledgeable and experienced in well maintenance and rehabilitation. Users of this guide are encouraged to consult the references provided.  
4.4 For additional information see Test Methods D4412, D5472/D5472M, D7726 and Guides D4448, D5254/D5254M, D5521/D5521M, D5409/D5409M, D5410 and D5474.
Note 1: The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results...
SCOPE
1.1 This guide covers an approach to selecting and implementing a well maintenance and rehabilitation program for groundwater monitoring wells. It provides information on symptoms of problems or deficiencies that indicate the need for maintenance and rehabilitation. It is limited to monitoring wells, that are designed and operated to provide access to, representative water samples from, and information about the hydraulic properties of the saturated subsurface while minimizing impact on the monitored zone. Some methods described herein may apply to other types of wells although the range of maintenance and rehabilitation treatment methods suitable for monitoring wells is more restricted than for other types of wells. Monitoring wells include their associated pumps and surface equipment.  
1.2 This guide is affected by governmental regulations and by site specific geological, hydrogeological, geochemical, climatological, and biological conditions.  
1.3 Units—The values stated in either inch-pound units or SI units presented 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 non-conformance with the standard.  
1.4 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D 6026, unless superseded by this standard.  
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.  
1.6 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...

General Information

• Status: Published
• Publication Date: 31-Dec-2023
• ICS: 13.060.10 - Water of natural resources
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.21 - Groundwater and Vadose Zone Investigations

Relations

• Replaces: ASTM D5978/D5978M-16 - Standard Guide for Maintenance and Rehabilitation of Groundwater Monitoring Wells
• Effective Date: 01-Jan-2024
• Referred By: ASTM D6771-21 - Standard Practice for Low-Flow Purging and Sampling Used for Groundwater Monitoring
• Effective Date: 01-Jan-2024

Overview

ASTM D5978/D5978M-16(2024), “Standard Guide for Maintenance and Rehabilitation of Groundwater Monitoring Wells,” is a critical international standard developed by ASTM International. This guide establishes best practices for selecting, implementing, and maintaining maintenance and rehabilitation programs specifically designed for groundwater monitoring wells. Monitoring wells play an essential role in evaluating groundwater quality, hydraulic properties, and the extent of contamination for environmental compliance or remediation monitoring. Due to the unique requirements of groundwater monitoring, maintenance must be tailored to avoid altering subsurface conditions, ensuring accurate data collection over the lifespan of each well.

Key Topics

• Maintenance Planning and Execution

  • The guide emphasizes that monitoring well maintenance is highly site- and well-specific.
  • Maintenance actions must prevent, mitigate, or correct physical or chemical deterioration that may compromise well functionality or the quality of groundwater samples.
  • Detecting well performance deficiencies through objective observation and testing is recommended, ideally performed by experienced personnel.

• Types of Well Deficiencies

  • Physical deficiencies: Infiltration of sand, silt, clay; low yield; well plugging; loss of production; physical damage; collapse.
  • Sample quality degradation: Caused by chemical encrustation, biofouling, corrosion, and changes in turbidity or the presence of fine particles.

• Rehabilitation Methods

  • Focuses on site-appropriate methods, largely favoring physical over chemical treatments to minimize impact on groundwater chemistry.
  • Redevelopment and restorative maintenance strategies are covered, aimed at recovering or improving well performance without introducing contaminants.

• Monitoring and Record-Keeping

  • Provides a framework for routine inspection, performance benchmarking, and documentation of all maintenance and rehabilitation activities.
  • Highlights the need for thorough record-keeping for regulatory compliance and long-term performance tracking.

Applications

Groundwater monitoring wells are a cornerstone for environmental site assessments, resource management, and regulatory compliance in industries such as environmental consulting, mining, landfills, water supply, and remediation projects. Adherence to ASTM D5978/D5978M is especially beneficial for:

• Regulatory agencies overseeing groundwater quality programs.
• Site owners and operators responsible for contaminated site management, who must ensure data integrity while monitoring remediation progress.
• Environmental consultants and field technicians performing routine well inspections, maintenance, and sampling.
• Engineers and contractors involved in the design, installation, and operation of groundwater monitoring systems.

Proper application of this standard ensures:

• Preservation of well integrity, maximizing service life and data reliability.
• Prompt detection and remediation of performance issues that could bias sampling or endanger nearby groundwater resources.
• Minimization of downtime or the need for costly well replacements by employing preventative maintenance strategies.
• Compliance with governmental regulations and industry best practices for groundwater monitoring.

Related Standards

Groundwater monitoring well maintenance is intertwined with several other ASTM standards that provide additional guidance on complementary activities:

• ASTM D5092/D5092M: Design and Installation of Groundwater Monitoring Wells
• ASTM D5521/D5521M: Development of Groundwater Monitoring Wells in Granular Aquifers
• ASTM D4448: Sampling of Groundwater Monitoring Wells
• ASTM D4412: Test Methods for Sulfate-Reducing Bacteria in Water
• ASTM D5472/D5472M: Determining Specific Capacity and Estimating Transmissivity at the Control Well
• ASTM D5254/D5254M: Data Elements to Identify a Groundwater Site
• ASTM D5409/D5409M, D5410, D5474: Sets of Data Elements for Groundwater Site Description

Consulting these related standards can improve the effectiveness and compliance of a well maintenance program, supporting robust groundwater monitoring systems that provide consistent, high-quality data.

Keywords: groundwater monitoring well, well maintenance, well rehabilitation, groundwater sample quality, monitoring well performance, ASTM D5978, groundwater standard, environmental monitoring, well inspection, well redevelopment.

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: D5978/D5978M − 16 (Reapproved 2024)
Standard Guide for
Maintenance and Rehabilitation of Groundwater Monitoring
Wells
This standard is issued under the fixed designation D5978/D5978M; 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.
INTRODUCTION
This guide for maintenance and rehabilitation promotes procedures appropriate to groundwater
monitoring wells installed to evaluate the extent and nature of contamination, progress of remediation,
and for long-term monitoring of either water quality or water level.
1. Scope responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.1 This guide covers an approach to selecting and imple-
mine the applicability of regulatory limitations prior to use.
menting a well maintenance and rehabilitation program for
1.6 This guide offers an organized collection of information
groundwater monitoring wells. It provides information on
or a series of options and does not recommend a specific
symptoms of problems or deficiencies that indicate the need for
course of action. This document cannot replace education or
maintenance and rehabilitation. It is limited to monitoring
experience and should be used in conjunction with professional
wells, that are designed and operated to provide access to,
judgment. Not all aspects of this guide may be applicable in all
representative water samples from, and information about the
circumstances. This ASTM standard is not intended to repre-
hydraulic properties of the saturated subsurface while minimiz-
sent or replace the standard of care by which the adequacy of
ing impact on the monitored zone. Some methods described
a given professional service must be judged, nor should this
herein may apply to other types of wells although the range of
document be applied without consideration of a project’s many
maintenance and rehabilitation treatment methods suitable for
unique aspects. The word “Standard” in the title of this
monitoring wells is more restricted than for other types of
document means only that the document has been approved
wells. Monitoring wells include their associated pumps and
through the ASTM consensus process.
surface equipment.
1.7 This international standard was developed in accor-
1.2 This guide is affected by governmental regulations and
dance with internationally recognized principles on standard-
by site specific geological, hydrogeological, geochemical,
ization established in the Decision on Principles for the
climatological, and biological conditions.
Development of International Standards, Guides and Recom-
1.3 Units—The values stated in either inch-pound units or
mendations issued by the World Trade Organization Technical
SI units presented in brackets are to be regarded separately as
Barriers to Trade (TBT) Committee.
standard. The values stated in each system may not be exact
2. Referenced Documents
equivalents; therefore, each system shall be used independently
of the other. Combining values from the two systems may
2.1 ASTM Standards:
result in non-conformance with the standard.
D653 Terminology Relating to Soil, Rock, and Contained
Fluids
1.4 All observed and calculated values shall conform to the
D3740 Practice for Minimum Requirements for Agencies
guidelines for significant digits and rounding established in
Engaged in Testing and/or Inspection of Soil and Rock as
Practice D 6026, unless superseded by this standard.
Used in Engineering Design and Construction
1.5 This standard does not purport to address all of the
D4044/D4044M Test Method for (Field Procedure) for In-
safety concerns, if any, associated with its use. It is the
stantaneous Change in Head (Slug) Tests for Determining
Hydraulic Properties of Aquifers
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. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Jan. 1, 2024. Published January 2024. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1996. Last previous edition approved in 2016 as D5978 – 16. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D5978_D5978M-16R24. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5978/D5978M − 16 (2024)
D4412 Test Methods for Sulfate-Reducing Bacteria in Water comparisons at later times. Desired level of well performance
and Water-Formed Deposits can vary depending on the design objectives.
D4448 Guide for Sampling Ground-Water Monitoring Wells
3.2.3 well preventive maintenance, n—any well mainte-
D4750 Test Method for Determining Subsurface Liquid
nance action that is initiated for the purpose of meeting some
Levels in a Borehole or Monitoring Well (Observation
preestablished rule or schedule that applies while well perfor-
Well) (Withdrawn 2010)
mance is still within preestablished ranges.
D5088 Practice for Decontamination of Field Equipment
3.2.4 well reconstructive maintenance, n—any preventive or
Used at Waste Sites
rehabilitative well maintenance action involving the replace-
D5092/D5092M Practice for Design and Installation of
ment of a major component (for example, pump, surface
Groundwater Monitoring Wells
protection).
D5254/D5254M Practice for Minimum Set of Data Ele-
3.2.5 well redevelopment, n—any preventive or rehabilita-
ments to Identify a Groundwater Site (Withdrawn 2019)
tive well maintenance action, taken after start-up, for the
D5299/D5299M Guide for Decommissioning of Groundwa-
purpose of mitigating or correcting deterioration of the filter
ter Wells, Vadose Zone Monitoring Devices, Boreholes,
pack or adjacent geologic formations, or both, due to the well’s
and Other Devices for Environmental Activities
presence and operation over time, usually involving physical
D5408 Guide for Set of Data Elements to Describe a
development procedures, applied in reaction to deterioration.
Groundwater Site; Part One—Additional Identification
Descriptors (Withdrawn 2019)
3.2.6 well rehabilitation, n—for the purposes of this guide,
D5409/D5409M Guide for Set of Data Elements to Describe
synonymous with well rehabilitative or restorative mainte-
a Groundwater Site;Part Two—Physical Descriptors
nance.
(Withdrawn 2019)
3.2.7 well rehabilitative or restorative maintenance, n—any
D5410 Guide for Set of Data Elements to Describe a
well maintenance action that is initiated for the purpose of
Groundwater Site;Part Three—Usage Descriptors (With-
correcting well performance that has moved outside of pre-
drawn 2016)
established ranges.
D5472/D5472M Practice for Determining Specific Capacity
and Estimating Transmissivity at the Control Well
4. Significance and Use
D5474 Guide for Selection of Data Elements for Groundwa-
4.1 The process of operating any engineered system, such as
ter Investigations (Withdrawn 2021)
monitoring wells, includes active maintenance to prevent,
D5521/D5521M Guide for Development of Groundwater
mitigate, or reverse deterioration. Lack of or improper main-
Monitoring Wells in Granular Aquifers
tenance can lead to well performance deficiencies (physical
D5753 Guide for Planning and Conducting Geotechnical
problems) or sample quality degradation (chemical problems).
Borehole Geophysical Logging
These problems are intrinsic to monitoring wells, which are
2.1.1 In addition, ASTM Volume 11.01 on Water (I) and
often left idle for long periods of time (as long as a year),
Volume 11.02 on Water (II) contain numerous test methods and
installed in non-aquifer materials, and installed to evaluate
standards that may be of value to the user of this guide.
contamination that can cause locally anomalous hydrogeo-
D7726 Guide for The Use of Various Turbidimeter Tech-
chemical conditions. The typical solutions for these physical
nologies for Measurement of Turbidity in Water
and chemical problems that would be applied by owners and
3. Terminology operators of water supply, dewatering, recharge, and other
wells may not be appropriate for monitoring wells because of
3.1 Definitions:
the need to minimize their impact on the conditions that
3.1.1 For definitions of common technical terms in this
monitoring wells were installed to evaluate.
standard, refer to Terminology D653.
3.2 Definitions of Terms Specific to This Standard: 4.2 This guide covers actions and procedures, but is not an
3.2.1 well development, n—actions taken during the instal-
encyclopedic guide to well maintenance. Well maintenance
lation and start-up of a well for the purpose of mitigating or planning and execution is highly site and well specific.
correcting damage done to the adjacent geologic formations
4.3 The design of maintenance and rehabilitation programs
and filter materials that might affect the well’s ability to
and the identification of the need for rehabilitation should be
produce representative samples.
based on objective observation and testing, and by individuals
3.2.2 well maintenance, n—any action that is taken for the
knowledgeable and experienced in well maintenance and
purpose of maintaining well performance (see Discussion) and
rehabilitation. Users of this guide are encouraged to consult the
extending the life of the well to provide samples that are
references provided.
representative of the groundwater surrounding it.
4.4 For additional information see Test Methods D4412,
3.2.2.1 Discussion—Maintenance includes both physical ac-
D5472/D5472M, D7726 and Guides D4448, D5254/D5254M,
tions taken at the well and the documentation of those actions
D5521/D5521M, D5409/D5409M, D5410 and D5474.
and all operating data in order to provide benchmarks for
NOTE 1—The quality of the result produced by this standard is
dependent on the competence of the personnel performing it, and the
The last approved version of this historical standard is referenced on suitability of the equipment and facilities used. Agencies that meet the
www.astm.org. criteria of Practice D3740 are generally considered capable of competent
D5978/D5978M − 16 (2024)
and objective testing/sampling/inspection/etc. Users of this standard are
because of faulty grout), corrosion and subsequent failure of
cautioned that compliance with Practice D3740 does not in itself assure
screen and casing, improper casing design, local site
reliable results. Reliable results depend on many factors; Practice D3740
operations, freeze-thaw, or improper chemical or mechanical
provides a means of evaluating some of those factors.
rehabilitation.
Practice D3740 was developed for agencies engaged in the testing
5.3.5 Observation of physical damage or other indicator.
and/or inspection of soils and rock. As such, it is not totally applicable to
agencies performing this practice. However, user of this practice should
recognize that the framework of Practice D3740 is appropriate for
6. Sample Quality Degradation
evaluating the quality of an agency performing this practice. Currently
there is no known qualifying national authority that inspects agencies that 6.1 All of the preceding physical well performance deficien-
perform this practice.
cies can result in sample quality degradation by dilution,
cross-contamination, or entrainment of solid material in water
5. Well Performance Deficiencies
samples. In addition, chemical and biological activity can both
5.1 Proper well design, installation, and development can
degrade well performance and sample quality. Any change in
minimize well performance deficiencies that result in the need
well or aquifer chemistry that results from the presence of the
for maintenance and rehabilitation. Practice D5092/D5092M
well can interfere with accurate characterization of a site.
and Guide D5521/D5521M should be consulted. Performance
6.2 Physical Indicators—Chemical and biological activity
deficiencies include: sand, silt, and clay infiltration; low yield;
that can lead to sample quality degradation include:
slow responses to changes in groundwater elevations; and loss
6.2.1 Chemical Encrustation—Precipitation of calcium or
of production.
magnesium carbonate or sulfate, iron, or sulfide compounds
5.2 Preventable Causes of Poor Well Performance:
can reduce well yield and specific capacity.
5.2.1 Inappropriate well location or screened interval. These
6.2.2 Biofouling (Biological Fouling)—Microbial activity
may be unavoidable if a requirement for site characterization or
can result in slime production and the precipitation of iron,
monitoring exists;
manganese, or sulfur compounds and occasionally other
5.2.2 Inappropriate drilling technique or methodology for
materials, such as aluminum oxides. Biofouling may be ac-
materials screened;
companied by corrosion or encrustation, or both, and can result
5.2.3 Inadequate intake structure design (screen, filter
in reduced specific capacity and well yield. Biochemical
material, and so forth);
deposits can interfere with sample quality by acting as chemi-
5.2.4 Inappropriate well construction materials. This may
cal sieves.
lead to corrosion or collapse;
6.2.3 Corrosion—Corrosion of metal well and pump com-
5.2.5 Improper construction, operation, or maintenance, or
ponents (that is, stainless steel, galvanized steel, carbon steel,
combination thereof, of borehole or well, wellhead protection,
and low carbon steel) can result from naturally aggressive
well cap, and/or locking device;
waters (containing H S, NaCl) or electrolysis. The presence of
5.2.6 Ineffective development;
contaminants contributes to corrosion through contributions to
5.2.7 Inappropriate pump selection; and
microbial corrosion processes and formation of redox gradi-
5.2.8 Introduction of foreign substances.
ents. Non-aqueous phase solvents may degrade PVC and other
5.3 Physical Indicators of Well Performance Deficiencies plastics. Other environmental conditions such as heat or
radiation may contribute to material deterioration (such as
Include:
enhanced embrittlement). Metals such as nickel or chromium
5.3.1 Sand, Silt, and Clay Infiltration—Causes include in-
may be leached from corroding metals. Degradation of plastic
appropriate and inadequate well drilling (for example, auger
well components may result in a release of monomers (such as
flight smearing), improper screen and filter pack, improper
vinyl chloride) to the environment (see Note 2).
casing design or installation, incomplete development, screen
corrosion, or collapse of filter pack. In rock wells, causes
NOTE 2—Naturally aggressive (for metals) waters have been defined as
include the presence of fine material in fractures. The presence
low pH (<7.0), high DO (>2 mg/L), high H S (>1 mg/L), high dissolved
−
of sand, silt, or clay can result in pump and equipment wear
solids (>1000 mg/L), high CO (>50 mg/L), and high Cl content (>500
mg/L). However, local conditions may result in corrosion at less extreme
and plugging, turbid samples, filter pack plugging, or combi-
values. Expression of corrosion is also dependent on materials load.
nation thereof.
5.3.2 Low Yield—Causes include dewatering, collapse or 6.2.4 Change in Turbidity—Causes include biofouling and
consolidation of fracture or water-bearing zone, pump mal- intake structure, screen or filter pack clogging or collapse.
function or plugging, screen encrustation or plugging, and Increase in turbidity may not always be the result of a problem
pump tubing corrosion or perforation or clogging. with the well. Changes in the purging and sampling procedures
5.3.3 Water Level Decline—Causes include area or regional and devices used can affect the turbidity of water from a
water level decline, well interference, and chemical or micro- monitoring well. For example, using a bailer where a pump
bial plugging or encrustation of the borehole, screen, or filter was previously utilized, or pumping at a higher rate than
previously used could increase turbidity; likewise, pumping a
pack.
5.3.4 Loss of Production—Usually caused by pump failure, well that was previously bailed could increase turbidity.
but can also be caused by dewatering, plugging, or well 6.2.5 Change in Sand/Silt Content or Particle Counts—
collapse. Causes include biofouling (resulting in clogging or sloughing)
5.3.4.1 Well Collapse—Can be caused by tectonism, ground and intake structure clogging or collapse. Increase in the
subsidence, failure of unsupported casing (that is, in caves or sand/silt content may not always be the result of a problem
D5978/D5978M − 16 (2024)
with the well. Changes in the purging and sampling procedures monitored and evaluated (see Sections 6 and 7), and a
and devices used can affect the sand/silt content of water from decision-making process on how to proceed to address prob-
a monitoring well. For example, using a bailer where a pump lems as they occur.
was previously utilized, or pumping at a higher rate than
7.2.2.1 The decision-making process should include, as a
previously used could increase the sand/silt content; likewise,
minimum, who will make the decisions based on what criteria,
pumping a well that was previously bailed could increase the
a set of alternatives such as establishing a program of preven-
sand/silt content.
tive treatment, replacing components on an as-needed basis,
and how to proceed if more intrusive rehabilitation or decom-
6.3 Chemical Indicators (Observed in Groundwater
missioning is needed. This decision-making process should be
Samples)—Chemical and biological activity that can lead to
triggered if there are changes in condition or performance
sample quality degradation include (see Note 3):
detected in routine monitoring that show deterioration or the
NOTE 3—Changes in chemical indicators can also be a result of potential to affect the well’s ability to provide acceptable
site-wide changes in hydro-geochemistry.
information. The decision-maker must decide what the stan-
2+ 3+
dards are and the importance of detected changes. It is
6.3.1 Iron (Changes in Total Fe, Fe /Fe , Iron Minerals
understood that there is no single level of performance or
and Complexes)—Causes include corrosion, changes in redox
maintenance standards that exists or is possible due to the
potential, and biofouling.
individual character of wells and site conditions.
2+ 4+
6.3.2 Manganese (Changes in Total Mn, Mn /Mn , Man-
7.2.3 In setting the goal(s) for an acceptable level of
ganese Minerals and Complexes)—Causes include changes in
performance, the users of this guide should keep in mind what
redox potential and biofouling.
is possible in a given situation and evaluate whether desired
2− 0 2−
6.3.3 Sulfur (Changes in Total S /S /SO , Sulfur Miner-
standards can be met. The decision process should include
als and Complexes)—Causes include changes in redox poten-
personnel with special knowledge or skill in well maintenance
tial and biofouling.
and rehabilitation, especially field or contractor personnel with
6.3.4 Changes in Redox Potential (Eh)—Causes include
direct experience in these activities. The well owner or
microbial activity and changes in O , CH , CO , N, S, Fe, and
2 4 2
responsible party should be informed of the preventative
Mn species present in the system.
maintenance program and its goals.
6.3.5 Changes in pH—Causes include corrosion; microbial
7.3 Maintenance Program Design—The design of a main-
activity; dissolved gases such as oxygen, carbon dioxide, and
tenance program should incorporate all available information
hydrogen sulfide; and encrustation.
about site-specific factors that could cause sand, silt, or clay
6.3.6 Changes in Conductivity—Causes include changes in
infiltration, sample turbidity or alteration, corrosion, or clog-
total solids content, microbial activity, and corrosion.
ging. Such information can include biological activity, redox
6.3.7 Changes in the Type and Concentration of Gases—
potential, pH, conductivity, alkalinity, and major ions present
Dissolved oxygen, carbon dioxide, nitrogen, hydrogen sulfide,
in the groundwater. Hydraulic performance and water chemis-
...