ASTM D5786-95(2000)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D5786–95 (Reapproved 2000)
Standard Practice for
(Field Procedure) for Constant Drawdown Tests in Flowing
Wells for Determining Hydraulic Properties of Aquifer
Systems
This standard is issued under the fixed designation D 5786; 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.
1. Scope 3. Terminology
1.1 This practice covers the methods for controlling draw- 3.1 Definitions—For definitions of terms used in this prac-
down and measuring discharge rates and head to analyze the tice, see Terminology D 653.
hydraulic properties of an aquifer or aquifers.
4. Summary of Practice
1.2 This practice is used in conjunction with analytical
procedures such as those of Jacob and Lohman (1)/(2), and 4.1 This practice describes the field procedures for conduct-
Hantush (3)/(4). ing an aquifer test on a well that is flowing, that is, the head in
the well remains above the top of the well casing. This method
1.3 The appropriate field and analytical procedures for
determining hydraulic properties of aquifer systems are se- involves inducing a constant drawdown and measuring the
varying discharge rate from the control well.
lected as described in Guide D 4043.
1.4 This standard does not purport to address all of the
5. Significance and Use
safety concerns, if any, associated with its use. It is the
5.1 Constant drawdown test procedures are used with ap-
responsibility of the user of this standard to establish appro-
propriate analytical procedures to determine transmissivity,
priate safety and health practices and determine the applica-
hydraulic conductivity, and storage coefficient of aquifers.
bility of regulatory limitations prior to use.
1.5 This practice offers a set of instructions for performing
6. Apparatus
one or more specific operations. This document cannot replace
6.1 Various types of equipment can be used to measure the
education or experience and should be used in conjunction
flow rate of the well. The equipment shall be sized so that it
withprofessionaljudgment.Notallaspectsofthispracticemay
does not constrict the flow rate from the well.
be applicable in all circumstances. This ASTM standard is not
6.2 An apparatus shall be placed on the control well
intended to represent or replace the standard of care by which
discharge line such that the well can be shut in to prevent flow
the adequacy of a given professional service must be judged,
prior to conducting this field procedure and so that the
nor should this document be applied without consideration of
apparatus will not constrict flow from the well when it is
a project’s many unique aspects. The word “Standard” in the
allowed to flow.
title of this document means only that the document has been
6.3 Head measurements can be made using one of the
approved through the ASTM consensus process.
following apparatuses:
2. Referenced Documents
6.3.1 Standpipe—A pipe or piece of well casing may be
installed to extend above the elevation of the discharge. This
2.1 ASTM Standards:
standpipe will also extend above the elevation of the head in
D 653 Terminology Relating to Soil, Rock, and Contained
the control well. This standpipe will allow for direct measure-
Fluids
ment of the water level following methods described in Test
D 4043 Guide for Selection of Aquifer-Test Method in
Method D 4750.
Determining of Hydraulic Properties by Well Techniques
6.3.2 Pressure Measurement—Apressure gage (mechanical
D 4750 Test Method for Determining Subsurface Liquid
gage, manometer, or pressure transducer) may be installed
Levels in a Borehole or Monitoring Well (Observation
below the shut-in mechanism in the control well. Determine
Well)
theheadelevationbyaddingthepressurereading(expressedin
the height of the water) to the elevation of the sensor of the
This practice is under the jurisdiction of ASTM Committee D18 on Soil and
pressure gage.
Rock and is the direct responsibility of Subcommittee D18.21 on GroundWater and
Vadose Zone Investigations.
Current edition approved Sept 10, 1995. Published October 1995.
Annual Book of ASTM Standards, Vol 04.08.
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D5786
6.4 Control Well—This practice requires that water flow 7.2.2 Shut in the Control Well—Completely stop flow from
from a single well. This well, known as the control well, shall the control well prior to conducting the test for a period at least
be drilled and completed such that it transmits water from the as long as the anticipated duration of the flowing portion of the
aquifer (usually the entire thickness of the aquifer) as effi- test.
ciently as possible to reduce head loss between the aquifer and 7.2.3 Discharge from Control Well—Allow the control well
the well. Well development should be as complete as possible to flow at a variable rate. The flow rate will vary naturally to
to eliminate additional production of sediments (aquifer par- maintain a constant drawdown at the control well.
ticles or drill cuttings) and consequent changes in well effi- 7.2.4 Measure Discharge Rate—Measure and record the
ciency during the test. discharge rate frequently during the early phase of discharge;
increase the interval between measurements in a logarithmic
manner as pumping continues.
7. Procedure
7.1 Pretest Procedures:
NOTE 1—Table 1 presents a suggested frequency of discharge measure-
ments.
7.1.1 Select Aquifer Test Method—Develop a conceptual
model of the site hydrogeology and select the appropriate
7.2.5 Measure Water Level—Measure and record the water
aquifer test method according to Guide D 4043. Observe the
levels in nearby wells at a frequency similar as presented in
requirements of the selected test method with regard to
Table 1.
specifications for the control well and observation wells.
7.3 Post-Testing Procedures:
7.1.2 Field Reconnaissance—Make a field reconnaissance
7.3.1 Tabulate water levels, including pre-flowing (shut-in),
of the site before conducting the test to collect as much detail
flowing, and post-flowing levels. For each well or piezometer
as possible on the depth, continuity, extent, and preliminary
record the date, clock time, time since flowing start
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