ASTM D4750-87(1993)e1
(Test Method)Standard Test Method for Determining Subsurface Liquid Levels in a Borehole or Monitoring Well (Observation Well)
Standard Test Method for Determining Subsurface Liquid Levels in a Borehole or Monitoring Well (Observation Well)
SCOPE
1.1 This test method describes the procedures for measuring the level of liquid in a borehole or well and determining the stabilized level of liquid in a borehole.
1.2 The test method applies to boreholes (cased or uncased) and monitoring wells (observation wells) that are vertical or sufficiently vertical so a flexible measuring device can be lowered into the hole.
1.3 Borehole liquid-level measurements obtained using this test method will not necessarily correspond to the level of the liquid in the vicinity of the borehole unless sufficient time has been allowed for the level to reach equilibrium position.
1.4 This test method generally is not applicable for the determination of pore-pressure changes due to changes in stress conditions of the earth material.
1.5 This test method is not applicable for the concurrent determination of multiple liquid levels in a borehole.
1.6 The values stated in inch-pound units are to be regarded as the standard.
1.7 This standard does not purport to address all of the safety problems, 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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e1
Designation: D 4750 – 87 (Reapproved 1993)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Determining Subsurface Liquid Levels in a Borehole or
Monitoring Well (Observation Well)
This standard is issued under the fixed designation D 4750; 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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Section 11 was added editorially in September 1993.
1. Scope 3.1.2 earth material—soil, bedrock, or fill.
3.1.3 ground-water level—the level of the water table sur-
1.1 This test method describes the procedures for measuring
rounding a borehole or well. The ground-water level can be
the level of liquid in a borehole or well and determining the
represented as an elevation or as a depth below the ground
stabilized level of liquid in a borehole.
surface.
1.2 The test method applies to boreholes (cased or uncased)
3.1.4 liquid level—the level of liquid in a borehole or well
and monitoring wells (observation wells) that are vertical or
at a particular time. The liquid level can be reported as an
sufficiently vertical so a flexible measuring device can be
elevation or as a depth below the top of the land surface. If the
lowered into the hole.
liquid is ground water it is known as water level.
1.3 Borehole liquid-level measurements obtained using this
3.1.5 monitoring well (observation well)—a special well
test method will not necessarily correspond to the level of the
drilled in a selected location for observing parameters such as
liquid in the vicinity of the borehole unless sufficient time has
liquid level or pressure changes or for collecting liquid
been allowed for the level to reach equilibrium position.
samples. The well may be cased or uncased, but if cased the
1.4 This test method generally is not applicable for the
casing should have openings to allow flow of borehole liquid
determination of pore-pressure changes due to changes in
into or out of the casing.
stress conditions of the earth material.
3.1.6 stabilized borehole liquid level—the borehole liquid
1.5 This test method is not applicable for the concurrent
level which remains essentially constant with time, that is,
determination of multiple liquid levels in a borehole.
liquid does not flow into or out of the borehole.
1.6 The values stated in inch-pound units are to be regarded
3.1.7 top of borehole—the surface of the ground surround-
as the standard.
ing the borehole.
1.7 This standard does not purport to address all of the
3.1.8 water table (ground-water table)—the surface of a
safety problems, if any, associated with its use. It is the
ground-water body at which the water pressure equals atmo-
responsibility of the user of this standard to establish appro-
spheric pressure. Earth material below the ground-water table
priate safety and health practices and determine the applica-
is saturated with water.
bility of regulatory limitations prior to use.
3.2 Definitions:
2. Referenced Documents
3.2.1 For definitions of other terms used in this test method,
see Terminology D 653.
2.1 ASTM Standards:
D 653 Terminology Relating to Soil, Rock, and Contained
4. Significance and Use
Fluids
4.1 In geotechnical, hydrologic, and waste-management
3. Terminology
investigations, it is frequently desirable, or required, to obtain
information concerning the presence of ground water or other
3.1 Definitions of Terms Specific to This Standard:
liquids and the depths to the ground-water table or other liquid
3.1.1 borehole—a hole of circular cross-section made in soil
surface. Such investigations typically include drilling of ex-
or rock to ascertain the nature of the subsurface materials.
ploratory boreholes, performing aquifer tests, and possibly
Normally, a borehole is advanced using an auger, a drill, or
completion as a monitoring or observation well. The opportu-
casing with or without drilling fluid.
nity exists to record the level of liquid in such boreholes or
wells, as the boreholes are being advanced and after their
This test method is under the jurisdiction of ASTM Committee D-18 on Soil completion.
and Rock and is the direct responsibility of Subcommittee D18.21 on Ground Water
4.2 Conceptually, a stabilized borehole liquid level reflects
and Vadose Zone Investigations.
the pressure of ground water or other liquid in the earth
Current edition approved Nov. 27, 1987. Published January 1988.
material exposed along the sides of the borehole or well. Under
Annual Book of ASTM Standards, Vol 04.08.
D 4750
suitable conditions, the borehole liquid level and the ground- ence point. Establish and identify a reference point at or near
water, or other liquid, level will be the same, and the former the top of the borehole or a well casing. Determine and record
can be used to determine the latter. However, when earth the distance from the reference point to the top of the borehole
materials are not exposed to a borehole, such as material which (land surface). If the borehole liquid level is to be reported as
is sealed off with casing or drilling mud, the borehole water an elevation, determine the elevation of the reference point or
levels may not accurately reflect the ground-water level. the top of borehole (land surface). Three alternative measure-
Consequently, the user is cautioned that the liquid level in a ment procedures (A, B, and C) are described.
borehole does not necessarily bear a relationship to the
NOTE 1—In general, Procedure A allows for greater accuracy than B or
ground-water level at the site.
C, and B allows for greater accuracy than C; other procedures have a
4.3 The user is cautioned that there are many factors which
variety of accuracies that must be determined from the referenced
can influence borehole liquid levels and the interpretation of
literature (2-5).
borehole liquid-level measurements. These factors are not
7.2 Procedure A—Measuring Tape:
described or discussed in this test method. The interpretation
7.2.1 Chalk the lower few feet of tape by drawing the tape
and application of borehole liquid-level information should be
across a piece of colored carpenter’s chalk.
done by a trained specialist.
7.2.2 Lower a weighted measuring tape slowly into the
4.4 Installation of piezometers should be considered where
borehole or well until the liquid surface is penetrated. Observe
complex ground-water conditions prevail or where changes in
and record the reading on the tape at the reference point.
intergranular stress, other than those associated with fluctua-
Withdraw the tape from the borehole and observe the lower
tion in water level, have occurred or are anticipated.
end of the tape. The demarcation between the wetted and
unwetted portions of the chalked tape should be apparent.
5. Apparatus
Observe and record the reading on the tape at that point. The
5.1 Apparatus conforming to one of the following shall be
difference between the two readings is the depth from the
used for measuring borehole liquid levels:
reference point to the liquid level.
5.1.1 Weighted Measuring Tape—A measuring tape with a
weight attached to the end. The tape shall have graduations that NOTE 2—Submergence of the weight and tape may temporarily cause a
liquid-level rise in wells or boreholes having very small diameters. This
can be read to the nearest 0.01 ft. The tape shall not stretch
effect can be significant if the well is in materials of very low hydraulic
more than 0.05% under normal use. Steel surveying tapes in
conductivity.
lengths of 50, 100, 200, 300, and 500 ft (20, 30, 50 or 100 m)
NOTE 3—Under dry surface conditions, it may be desirable to pull the
and widths of ⁄4 in. (6 mm) are commonly used. A black metal
tape from the well or borehole by hand, being careful not to allow it to
tape is better than a chromium-plated tape. Tapes are mounted
become kinked, and reading the liquid mark before rewinding the tape
on hand-cranked reels up to 500 ft (100 m) lengths. Mount a
onto the reel. In this way, the liquid mark on the chalked part of the tape
slender weight, made of lead, to the end of the tape to ensure is rapidly brought to the surface before the wetted part of the tape dries.
In cold regions, rapid withdrawal of the tape from the well is necessary
plumbness and to permit some feel for obstructions. Attach the
before the wet part freezes and becomes difficult to read. The tape must be
weight to the tape with wire strong enough to hold the weight
protected if rain is falling during measurements.
but not as strong as the tape. This permits saving the tape in the
NOTE 4—In some pumped wells, or in contaminated wells, a layer of oil
event the weight becomes lodged in the well or borehole. The
may float on the water. If the oil layer is only a foot or less thick, read the
size of the weight shall be such that its displacement of water
tape at the top of the oil mark and use this reading for the water-level
causes less than a 0.05-ft (15-mm) rise in the borehole water
measurement. The measurement will not be greatly in error because the
level of the oil surface in this case will differ only slightly from the level
level, or a correction shall be made for the displacement. If the
of the water surface that would be measured if no oil was present. If
weight extends beyond the end of the tape, a length correction
several feet of oil are present in the well, or if it is necessary to know the
will be needed in measurement Procedure C (see 7.2.3).
thickness of the oil layer, a water-detector paste for detecting water in oil
5.1.2 Electrical Measuring Device—A cable or tape with
and gasoline storage tanks is available commercially. The paste is applied
electrical wire encased, equipped with a weighted sensing tip
to the lower end of the tape that is submerged in the well. It will show the
on one end and an electric meter at the other end. An electric
top of the oil as a wet line and the top of the water as a distinct color
circuit is completed when the tip contacts water; this is
change.
registered on the meter. The cable may be marked with
7.2.3 As a standard of good practice, the observer should
graduations similar to a measuring tape (as described in 5.1.1).
make two measurements. If two measurements of static liquid
5.1.3 Other Measuring Devices—A number of other record-
level made within a few m
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