Standard Guide for Selection and Documentation of Existing Wells for Use in Environmental Site Characterization and Monitoring

SIGNIFICANCE AND USE
This guide describes a general approach for the use of existing wells in environmental investigations with a primary focus on the subsurface and major factors affecting the surface and subsurface environment.
Existing wells represent a valuable source of information for subsurface environmental investigations. Specific uses of existing wells include:
Well driller logs provide information on subsurface lithology and major water-bearing units in an area. Existing wells can also offer access for downhole geophysical logging for stratigraphic and aquifer interpretations. Examples include natural gamma logs in cased wells and an entire suite of methods in uncased bedrock wells (see Guide D5753). This information can assist in developing the preliminary conceptual model of the site.
Well tests using existing wells may provide information on the hydrologic characteristics of an aquifer.
Monitoring of water levels in existing wells, provided that they are cased in the aquifer of interest, allow development of potentiometric maps and interpretations of groundwater flow directions.
Existing wells are the primary means by which regional drinking water quality is evaluated and monitored.
Existing wells may assist in the mapping of contaminant plumes, and in ongoing monitoring of groundwater quality changes at the site-specific level.
Data from existing wells should only be used when characteristics of the well have been sufficiently documented to determine that they satisfy criteria for the purpose for which the data are to be used.
SCOPE
1.1 This guide covers the use of existing wells for environmental site characterization and monitoring. It covers the following major topics: criteria for determining the suitability of existing wells for hydrogeologic characterization and groundwater quality monitoring, types of data required to document the suitability of an existing well, and the relative advantages and disadvantages of existing large- and small-capacity wells.
1.2 This guide should be used in conjunction with Guide D5730, that provides a general approach for environmental site investigations.
1.3 This guide does not specifically address design and construction of new monitoring or supply wells. Refer to Practices D5092 and D5787.
1.4 This guide does not specifically address groundwater sampling procedures. Refer to Guide D5903.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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.  
1.7 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This guide cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This guide 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 guide 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.

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Publication Date
31-Jul-2010
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ASTM D5980-96(2010)e1 - Standard Guide for Selection and Documentation of Existing Wells for Use in Environmental Site Characterization and Monitoring
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation: D5980 − 96(Reapproved 2010)
Standard Guide for
Selection and Documentation of Existing Wells for Use in
Environmental Site Characterization and Monitoring
This standard is issued under the fixed designation D5980; 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.
ε NOTE—The units statement in 1.5 was revised editorially in August 2010.
1. Scope professional service must be judged, nor should this guide be
applied without consideration of a project’s many unique
1.1 This guide covers the use of existing wells for environ-
aspects. The word “Standard” in the title of this document
mental site characterization and monitoring. It covers the
means only that the document has been approved through the
following major topics: criteria for determining the suitability
ASTM consensus process.
of existing wells for hydrogeologic characterization and
groundwater quality monitoring, types of data required to
2. Referenced Documents
document the suitability of an existing well, and the relative
2.1 Pertinent guides addressing specific information neces-
advantages and disadvantages of existing large- and small-
sary to utilize existing wells for hydrologic and water-quality
capacity wells.
data for environmental site characterization. A comprehensive
1.2 This guide should be used in conjunction with Guide
listofguides,standards,methods,practices,andterminologyis
D5730, that provides a general approach for environmental site
contained in Guide D5730. Other guidance documents cover-
investigations.
ing procedures for environmental site investigations with
1.3 This guide does not specifically address design and
specific objectives or in particular geographic settings may be
construction of new monitoring or supply wells. Refer to
available from federal, state, and other agencies or organiza-
Practices D5092 and D5787.
tions. The appropriate agency or organization should be
contactedtodeterminetheavailabilityandmostcurrentedition
1.4 This guide does not specifically address groundwater
of such documents.
sampling procedures. Refer to Guide D5903.
2.2 ASTM Standards:
1.5 The values stated in SI units are to be regarded as
D653 Terminology Relating to Soil, Rock, and Contained
standard. No other units of measurement are included in this
Fluids
standard.
D4750 Test Method for Determining Subsurface Liquid
1.6 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) (Withdrawn 2010)
responsibility of the user of this standard to establish appro-
D5092 Practice for Design and Installation of Groundwater
priate safety and health practices and determine the applica-
Monitoring Wells
bility of regulatory limitations prior to use.
D5254 Practice for Minimum Set of Data Elements to
1.7 This guide offers an organized collection of information
Identify a Ground-Water Site
or a series of options and does not recommend a specific
D5408 Guide for Set of Data Elements to Describe a
course of action. This guide cannot replace education or
Groundwater Site; Part One—Additional Identification
experienceandshouldbeusedinconjunctionwithprofessional
Descriptors
judgment. Not all aspects of this guide may be applicable in all
D5409 Guide for Set of Data Elements to Describe a
circumstances. This guide is not intended to represent or
Ground-Water Site; Part Two—Physical Descriptors
replace the standard of care by which the adequacy of a given
D5410 Guide for Set of Data Elements to Describe a
1 2
This guide is under the jurisdiction of ASTM Committee D18 on Soil and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Rockand is the direct responsibility of Subcommittee D18.21 on Groundwater and contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Vadose Zone Investigations. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Aug. 1, 2010. Published September 2010. Originally the ASTM website.
approved in 1996. Last previous edition approved in 2004 as D5980–96(2004). The last approved version of this historical standard is referenced on
DOI: 10.1520/D5980-96R10E01. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D5980 − 96 (2010)
Ground-Water Site;Part Three—Usage Descriptors 4.2.2 Well tests using existing wells may provide informa-
D5474 Guide for Selection of Data Elements for Groundwa- tion on the hydrologic characteristics of an aquifer.
ter Investigations 4.2.3 Monitoring of water levels in existing wells, provided
D5521 Guide for Development of Groundwater Monitoring thattheyarecasedintheaquiferofinterest,allowdevelopment
Wells in Granular Aquifers ofpotentiometricmapsandinterpretationsofgroundwaterflow
D5730 Guide for Site Characterization for Environmental directions.
Purposes With Emphasis on Soil, Rock, the Vadose Zone 4.2.4 Existing wells are the primary means by which re-
and Groundwater (Withdrawn 2013) gional drinking water quality is evaluated and monitored.
D5753 Guide for Planning and Conducting Borehole Geo- 4.2.5 Existing wells may assist in the mapping of contami-
physical Logging nant plumes, and in ongoing monitoring of groundwater
D5787 Practice for Monitoring Well Protection quality changes at the site-specific level.
D5903 Guide for Planning and Preparing for a Groundwater
4.3 Data from existing wells should only be used when
Sampling Event
characteristicsofthewellhavebeensufficientlydocumentedto
D5978 Guide for Maintenance and Rehabilitation of
determine that they satisfy criteria for the purpose for which
Groundwater Monitoring Wells
the data are to be used.
D5979 Guide for Conceptualization and Characterization of
Groundwater Systems
5. General Considerations in Selection and Use of
Existing Wells
3. Terminology
5.1 Selection and use of existing wells should take place in
3.1 Definitions:
the context of a conceptual framework consisting of a descrip-
3.1.1 Except as noted below, all definitions are in accor- tion of the system, including, as necessary, physical and
dance with Terminology D653:
cultural characteristics, such as climate, hydrology, ecology,
physiography, population, water use and land use, and hypoth-
3.1.2 aquifer, n—a geologic formation, group of formations,
or part of a formation that is saturated and is capable of eses about processes of interest that occur within that system.
A step-wise approach for conceptualization and characteriza-
providing a significant quantity of water (see Practice D5092).
tion is a direct approach to develop the framework for
3.1.3 monitoring well (observation well), n—a special well
Hydrologic Systems as described in Kolm (1) , (see Guide
drilled in a selected location for observing parameters such as
D5979). Conceptualization of hydrologic and regional ground-
liquid level or pressure changes or for collecting liquid
water quality systems can be formulated using the methods
samples. The well may be cased or uncased, but if cased, the
outlined in Alley (2). The framework is reviewed and refined
casing should have openings to allow flow of borehole liquid
by an iterative process of data collection and analysis, testing
into or out of the casing.
hypotheses with data collected, and identifying data needs to
3.1.4 observation well, n—for the purposes of this guide, an
further revise the framework. Refinement must be made within
existing well constructed for other purposes that is also used to
the limits established by the accuracy, precision, and complete-
measure water levels and to collect groundwater quality
ness of the data. Methods for data collection are selected that
samples. Observation well may be referred to as “well” in this
will provide data appropriate for testing hypotheses which
guide.
evaluate the conceptual framework.
3.1.5 supply (production) well, n—well primarily installed
5.2 Well design and installation can critically affect the
for public supply, irrigation, and industrial use. Supply wells
quality of water level measurements and groundwater samples.
may be used as an observation well.
Such effects apply both to existing wells and to wells specifi-
cally installed for a purpose. The effects of well design and
4. Significance and Use
installation, therefore, need to be considered regardless of
whether existing wells are selected or if wells are specifically
4.1 This guide describes a general approach for the use of
installedforaspecificpurpose.Themostcommonfeatureofan
existing wells in environmental investigations with a primary
existing well that may render it unsuitable for water level
focus on the subsurface and major factors affecting the surface
measurement or water-quality monitoring is that multiple
and subsurface environment.
hydrogeologic units are connected causing water levels and
4.2 Existing wells represent a valuable source of informa-
water-quality parameters to reflect a mixing of multiple hydro-
tion for subsurface environmental investigations. Specific uses
geologic units. Such data cannot be reliably compared with
of existing wells include:
data from wells completed in the individual hydrogeologic
4.2.1 Well driller logs provide information on subsurface units.
lithology and major water-bearing units in an area. Existing
5.3 Major steps in the selection of existing wells for
wells can also offer access for downhole geophysical logging
environmental investigations include: developing specific cri-
for stratigraphic and aquifer interpretations. Examples include
teria for evaluating the suitability of existing wells in relation
natural gamma logs in cased wells and an entire suite of
methods in uncased bedrock wells (see Guide D5753). This
information can assist in developing the preliminary concep-
The boldface numbers in parentheses refer to the list of references at the end of
tual model of the site. this standard.
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D5980 − 96 (2010)
to the objectives of the investigations (see Section 6), conduct- 6.3.5 A well constructed of PVC (polyvinylchloride) with
ing an inventory of existing wells in the area of interest (see glued joints would not be suitable for sampling if the volatile-
8.1), documenting the characteristics of the wells identified in organic compounds of interest in the groundwater also are
the inventory that are relevant to the selection criteria (see8.2), found in the glue used to join the sections of well casing.
and identification of wells that satisfy the selection criteria (see Similarly, a well constructed of steel may not be suitable for
Section 9). the sampling of metals.
6.3.6 Selecting an observation well in an area undergoing
6. Well-Selection Criteria rapid development would be avoided in constructing a network
of wells for evaluating long-term trends in groundwater quality
6.1 Assessing the suitability of existing wells for hydrologi-
because of the possibility of the well being destroyed by later
cal and groundwater quality studies requires development of
development.
specific well-selection criteria. The criteria are based on
considerations of project objectives by defining the problem to
7. General Characteristics of Major Types of Existing
be solved, the conceptual framework, and data-collection
Wells
requirements.
7.1 There are two general categories of existing wells
6.2 Specific Well-Selection Criteria—Specific criteria will
available for hydrologic and groundwater quality studies:
depend on the objectives of the investigation. The following
large- and small-capacity supply or production wells installed
general criteria will apply to most situations:
fordrinking,irrigation,andindustrialuse(see7.2and7.3);and
6.2.1 The well is suitably located for use in relation to the
wells specially designed and installed to monitor hydrologic or
conceptual framework.
water-quality studies, or both (see 7.4). Each type of well has
6.2.2 The well must be completed in the targeted hydrogeo-
its own general advantages and disadvantages.
logic unit or units.
7.2 Large-Capacity Supply Wells—Large-capacity supply
6.2.3 Welldesignandconstructionmustnotbiaswaterlevel
wells are usually developed for drinking water systems that
measurements or water-quality sampling results (see Note 1).
supply multiple households, and for irrigation and industrial
Section7providesinformationonthegeneralcharacteristicsof
purposes.
major types of existing wells.
7.2.1 Advantages:
NOTE 1—Gillham et al. (3), provides information on the suitability of
7.2.1.1 Documentation of well construction commonly is
materials coming in contact with water samples and that table provides
good.
information on the compatibility of well casing materials with different
7.2.1.2 Large-capacity wells generally are well developed
organic contaminants.
and fully purged.
6.2.4 The well is accessible for measurements and sam-
7.2.1.3 Long-term access may be possible, particularly for
pling.
municipal wells.
6.2.5 The well’s maintenance condition may not compro-
7.2.1.4 Large-capacity wells generally provide a larger ver-
mise it as a sampling point; however, there are examples that
tical mix of water in an aquifer or aquifer system than
may compromise it as a sampling point, that is, a cracked
small-capacity wells, and thus can provide a more integrated
casing allowing non-screened water into the well.
measure of regional groundwater quality than small-capacity
wells.
6.3 Examples of Well Selection Criteria—The following are
7.2.1.5 Much of the water produced for irrigation and
illustrative examples of criteria for specific investigation ob-
municipal water is from large-capacity wells equipped with
jectives (see Note 2).
taps which allow a direct sample of the pumped water.
NOTE2—Theseareillustrativeexamplesandshouldnotbeconstruedas
7.2.1.6 Long-term water-quality and quantity data may be
recommended criteria.
available.
6.3.1 A project to determine the quality of potable ground-
7.2.2 Disadvantages:
water might require the following selection criteria: wells
7.2.2.1 Large-capacity wells may not have flow-rate con-
selected must be used for public water supply, must be
trols and a sampling point near the well head.
geographically distributed over the entire aquifer of interest,
7.2.2.2 High pumping rates may entrain artifacts, such as
and must be able to be sampled prior to any water treatment.
colloids or suspended material, into the sample stream.
6.3.2 All
...

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