ASTM D5978-96e1
(Guide)Standard Guide for Maintenance and Rehabilitation of Ground-Water Monitoring Wells
Standard Guide for Maintenance and Rehabilitation of Ground-Water Monitoring Wells
SCOPE
1.1 This guide covers an approach to selecting and implementing a well maintenance and rehabilitation program for ground-water 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 The values stated in SI units are to be regarded as the standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:D5978–96
Standard Guide for
Maintenance and Rehabilitation of Ground-Water Monitoring
Wells
This standard is issued under the fixed designation D5978; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Paragraph 1.5 was added editorially October 1998.
INTRODUCTION
This guide for maintenance and rehabilitation promotes procedures appropriate to ground-water
monitoringwellsinstalledtoevaluatetheextentandnatureofcontamination,progressofremediation,
and for long-term monitoring of either water quality or water level.
1. Scope circumstances. This ASTM standard is not intended to repre-
sent or replace the standard of care by which the adequacy of
1.1 This guide covers an approach to selecting and imple-
a given professional service must be judged, nor should this
menting a well maintenance and rehabilitation program for
documentbeappliedwithoutconsiderationofaproject’smany
ground-water monitoring wells. It provides information on
unique aspects. The word “Standard” in the title of this
symptomsofproblemsordeficienciesthatindicatetheneedfor
document means only that the document has been approved
maintenance and rehabilitation. It is limited to monitoring
through the ASTM consensus process.
wells, that are designed and operated to provide access to,
representative water samples from, and information about the
2. Referenced Documents
hydraulicpropertiesofthesaturatedsubsurfacewhileminimiz-
2.1 ASTM Standards:
ing impact on the monitored zone. Some methods described
D653 Terminology Relating to Soil, Rock, and Contained
herein may apply to other types of wells although the range of
Fluids
maintenance and rehabilitation treatment methods suitable for
D1889 Test Method for Turbidity of Water
monitoring wells is more restricted than for other types of
D4044 Test Method for (Field Procedures) Determining
wells. Monitoring wells include their associated pumps and
Instantaneous Change in Head (Slug Tests) for Determin-
surface equipment.
ing Hydraulic Properties of Aquifers
1.2 This guide is affected by governmental regulations and
D4412 Test Methods for Sulfide Reducing Bacteria in
by site specific geological, hydrogeological, geochemical,
Water and Water-Formed Deposits
climatological, and biological conditions.
D4448 Guide for Sampling Ground Water Monitoring
1.3 The values stated in SI units are to be regarded as the
Wells
standard.
D4750 Test Method for Determining Subsurface Liquid
1.4 This standard does not purport to address all of the
Levels in a Borehole or Monitoring Well (Observation
safety concerns, if any, associated with its use. It is the
Well)
responsibility of the user of this standard to establish appro-
D5088 Practice for Decontamination of Field Equipment
priate safety and health practices and determine the applica-
Used at Nonradioactive Waste Sites
bility of regulatory limitations prior to use.
D5092 Practice for Design and Installation of Ground
1.5 This guide offers an organized collection of information
Water Monitoring Wells in Aquifers
or a series of options and does not recommend a specific
D5254 Practice for the Minimum Set of Data Elements to
course of action. This document cannot replace education or
Identify a Ground-Water Site
experienceandshouldbeusedinconjunctionwithprofessional
D5299 Guide for the Decommissioning of Ground Water
judgment.Notallaspectsofthisguidemaybeapplicableinall
Wells, Vadose Zone Monitoring Devices, Boreholes, and
1 2
This guide is under the jurisdiction of ASTM Committee D-18 on Soil and Annual Book of ASTM Standards, Vol 04.08.
RockandisthedirectresponsibilityofSubcommitteeD18.21onGroundWaterand Annual Book of ASTM Standards, Vol 11.01.
Vadose Zone Investigations. Annual Book of ASTM Standards, Vol 11.02.
Current edition approved July 10, 1996. Published November 1996. Annual Book of ASTM Standards, Vol 11.04.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D5978–96
Other Devices for Environmental Activities 3.2.6 well rehabilitation—for the purposes of this guide,
synonymous with well rehabilitative or restorative mainte-
D5408 Guide for the Set of Data Elements to Describe a
nance.
Ground-Water Site; Part 1—Additional Identification De-
3.2.7 well rehabilitative or restorative maintenance—any
scriptors
well maintenance action that is initiated for the purpose of
D5409 Guide for the Set of Data Elements to Describe a
correcting well performance that has moved outside of prees-
Ground-Water Site; Part 2—Physical Descriptors
tablished ranges.
D5410 Guide for the Set of Data Elements to Describe a
Ground-Water Site; Part 3—Usage Descriptors
4. Significance and Use
D5472 TestMethodforDeterminingSpecificCapacityand
2 4.1 Theprocessofoperatinganyengineeredsystem,suchas
Estimating Transmissivity at the Control Well
monitoring wells, includes active maintenance to prevent,
D5474 Guide for Selection of Data Elements for Ground-
mitigate, or reverse deterioration. Lack of or improper main-
Water Investigations
tenance can lead to well performance deficiencies (physical
D5521 Guide for Development of Ground Water Monitor-
problems) or sample quality degradation (chemical problems).
ing Wells in Granular Aquifers
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),
Volume11.02onWater(II)containnumeroustestmethods
installed in non-aquifer materials, and installed to evaluate
andstandardsthatmaybeofvaluetotheuserofthisguide.
contamination that can cause locally anomalous hydro-
geochemical conditions. The typical solutions for these physi-
3. Terminology
cal and chemical problems that would be applied by owners
3.1 Definitions: and operators of water supply, dewatering, recharge, and other
3.1.1 Except where noted, all terms and symbols in this wells may not be appropriate for monitoring wells because of
the need to minimize their impact on the conditions that
guideareinaccordancewiththefollowingpublicationsintheir
monitoring wells were installed to evaluate.
order of consideration:
4.2 This guide covers actions and procedures, but is not an
3.1.1.1 Terminology D653,
encyclopedic guide to well maintenance. Well maintenance
3.1.1.2 Guide D5521,
planning and execution is highly site and well specific.
3.1.1.3 Compilation of ASTM Standard Terminology, 7th
4.3 The design of maintenance and rehabilitation programs
Edition, 1990, and
and the identification of the need for rehabilitation should be
3.1.1.4 Webster’s Ninth New Collegiate Dictionary, 1989.
based on objective observation and testing, and by individuals
3.2 Definitions of Terms Specific to This Standard:
knowledgeable and experienced in well maintenance and
3.2.1 well development—actions taken during the installa-
rehabilitation.Usersofthisguideareencouragedtoconsultthe
tion and start-up of a well for the purpose of mitigating or
references provided.
correcting damage done to the adjacent geologic formations
4.4 For additional information see Test Methods D1889,
and filter materials that might affect the well’s ability to
D4412, D5472, and Guides D4448, D5409, D5410 and
produce representative samples.
D5474.
3.2.2 well maintenance—any action that is taken for the
purpose of maintaining well performance (see Discussion) and 5. Well Performance Deficiencies
extending the life of the well to provide samples that are
5.1 Proper well design, installation, and development can
representativeofthegroundwatersurroundingit.Maintenance
minimize well performance deficiencies that result in the need
includes both physical actions taken at the well and the
for maintenance and rehabilitation. Practice D5092 and Guide
documentation of those actions and all operating data in order
D5521shouldbeconsulted.Performancedeficienciesinclude:
to provide benchmarks for comparisons at later times.
sand, silt, and clay infiltration; low yield; slow responses to
3.2.2.1 Discussion—Desired level of well performance can
changes in ground-water elevations; and loss of production.
vary depending on the design objectives.
5.2 Preventable Causes of Poor Well Performance:
3.2.3 well preventive maintenance—any well maintenance
5.2.1 Inappropriatewelllocationorscreenedinterval.These
action that is initiated for the purpose of meeting some
maybeunavoidableifarequirementforsitecharacterizationor
preestablished rule or schedule that applies while well perfor-
monitoring exists,
mance is still within preestablished ranges.
5.2.2 Inappropriate drilling technique or methodology for
3.2.4 well reconstructive maintenance—any preventive or
materials screened,
rehabilitative well maintenance action involving the replace-
5.2.3 Inadequate intake structure design (screen, filter ma-
ment of a major component (for example, pump, surface
terial, and so forth),
protection).
5.2.4 Inappropriate well construction materials. This may
3.2.5 well redevelopment—any preventive or rehabilitative lead to corrosion or collapse,
wellmaintenanceaction,takenafterstart-up,forthepurposeof 5.2.5 Improper construction, operation, or maintenance, or
mitigating or correcting deterioration of the filter pack or combination thereof, of borehole or well, wellhead protection,
adjacent geologic formations, or both, due to the well’s well cap, and locking device,
presence and operation over time, usually involving physical 5.2.6 Ineffective development,
development procedures, applied in reaction to deterioration. 5.2.7 Inappropriate pump selection, and
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D5978–96
5.2.8 Introduction of foreign substances. radiation may contribute to material deterioration (such as
5.3 Physical Indicators of Well Performance Deficiencies enhanced embrittlement). Metals such as nickel or chromium
Include: may be leached from corroding metals. Degradation of plastic
5.3.1 Sand, Silt, and Clay Infiltration—Causes include in- well components may result in a release of monomers (such as
appropriate and inadequate well drilling (for example, auger vinyl chloride) to the environment (see Note 1).
flight smearing), improper screen and filter pack, improper
NOTE 1—Naturallyaggressive(formetals)watershavebeendefinedas
casing design or installation, incomplete development, screen
low pH (<7.0), high DO (>2 mg/L), high H S (>1 mg/L), high dissolved
corrosion, or collapse of filterpack. In rock wells, causes −
solids (>1000 mg/L), high CO (>50 mg/L), and high Cl content (>500
includethepresenceoffinematerialinfractures.Thepresence
mg/L). However, local conditions may result in corrosion at less extreme
of sand, silt, or clay can result in pump and equipment wear values. Expression of corrosion is also dependent on materials load.
and plugging, turbid samples, filterpack plugging, or combina-
6.2.4 Change in Turbidity—Causes include biofouling and
tion thereof.
intake structure, screen or filter pack clogging or collapse.
5.3.2 Low Yield—Causes include dewatering, collapse or
Increaseinturbiditymaynotalwaysbetheresultofaproblem
consolidation of fracture or water-bearing zone, pump mal-
withthewell.Changesinthepurgingandsamplingprocedures
function or plugging, screen encrustation or plugging, and
and devices used can affect the turbidity of water from a
pump tubing corrosion or perforation.
monitoring well. For example, using a bailer where a pump
5.3.3 Water Level Decline—Causesincludeareaorregional
was previously utilized, or pumping at a higher rate than
water level decline, well interference, and chemical or micro-
previously used could increase turbidity; likewise, pumping a
bial plugging or encrustation of the borehole, screen, or
well that was previously bailed could increase turbidity.
filterpack.
6.2.5 Change in Sand/Silt Content or Particle Counts—
5.3.4 Loss of Production—Usually caused by pump failure,
Causes include biofouling (resulting in clogging or sloughing)
but can also be caused by dewatering, plugging, or well
and intake structure clogging or collapse. Increase in the
collapse.
sand/silt content may not always be the result of a problem
5.3.4.1 WellCollapse—Canbecausedbytectonism,ground
withthewell.Changesinthepurgingandsamplingprocedures
subsidence, failure of unsupported casing (that is, in caves or
and devices used can affect the sand/silt content of water from
because of faulty grout), corrosion and subsequent failure of
a monitoring well. For example, using a bailer where a pump
screen and casing, improper casing design, local site opera-
was previously utilized, or pumping at a higher rate than
tions, freeze-thaw, or improper chemical or mechanical reha-
previously used could increase the sand/silt content; likewise,
bilitation.
pumping a well that was previously bailed could increase the
5.3.5 Observation of physical damage or other indicator.
sand/silt content.
6. Sample Quality Degradation
6.3 Chemical Indicators (Observed in Ground Water
6.1 Alloftheprecedingphysicalwellperformancedeficien- Samples)—Chemical and biological activity that can lead to
cies can result in sample quality degradation by dilution,
sample quality degradation include (see Note 2):
cross-contamination, or entrainment of solid material in water
NOTE 2—Changes in chemical indicators can also be a result of
samples. In addition, chemical and biological activity can both
site-wide changes in hydro-geochemistry.
degrade well performance and sample quality. Any change in
2+ 3+
well or aquifer chemistry that results from the presence of the 6.3.1 Iron (Changes in Total Fe, Fe /Fe , Iron Minerals
and Complexes)—Causes include corrosion, changes in redox
well can interfere with accurate characterization of a site.
6.2 Physical Indicators—Chemical and biological activity potential, and biofouling.
2+ 4+
that can lead to sample quality degradation include:
6.3.2 Manganese (Changes in Total Mn, Mn /Mn , Man-
6.2.1 Chemical Encrustation—Precipitation of calcium or
ganese Minerals and Complexes)—Causes include changes in
magnesium carbonate or sulfate, iron, or sulfide compounds
redox potential and biofouling.
2− 0 2−
can reduce well yield and specific capacity.
6.3.3 Sulfur (Changes in Total S /S /SO , Sulfur Miner-
6.2.2 Biofouling (Biological Fouling)—Microbial activity
als and Complexes)—Causes include changes in redox poten-
can result in slime production and the precipitation of iron,
tial and biofouling.
manganese, or sulfur compounds and occasionally other ma-
6.3.4 Changes in Redox Potent
...
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