TM 5-815-5/AFM 88-5, Chap 6/NAVFAC P-418
portance if the well screen fully penetrates the aqui-
and adjacent piezometers, and (e) some means for accu-
fer; of course, the derived permeability for this case is
rately measuring the flow from the well.
actually kh. If the formation is stratified and kh > kv,
a. Test and observation wells. The test well should
and the flow to the well is gravity in nature, the com-
fully penetrate the aquifer to avoid uncertainties in-
puted permeability k would be <kh and >kv.
volved in the analysis of partially penetrating wells,
(3) Marked changes of well or aquifer perfor-
and the piezometers should be installed at depths
mance during a nonequilibrium test indicate that the
below any anticipated drawdown during the pumping
physical conditions of the aquifer do not conform to
test. The number, spacing, and arrangement of the ob-
the assumptions made in the development of the
servation wells or piezometers will depend on the char-
formula for nonsteady flow to a well. However, such a
acteristics of the aquifer and the geology of the area
departure does not necessarily invalidate the test data;
(figs. C-2 and C-3). Where the test well is located ad-
in fact, analysis of the change can be used as a tool to
jacent to a river or open water, one line of piezometers
better determine the flow characteristics of the aqui-
should be installed on a line perpendicular to the river,
fer.
one line parallel to the river, and, if possible, one line
C-2. pumping test equipment and proce-
away from the river. At least one line of piezometers
dures. Determination of k from a pumping test re-
should extend 500 feet or more out from the test well.
quires: (a) installation of a test well, (b) two, and pref-
The holes made for installing piezometers should be
erably more, observation wells or piezometers, (c) a
logged for use in the analysis of the test. The distance
suitable pump, (d) equipment for sounding the well
from the test well to each piezometer should be meas-
U.S. Army Corps of Engineers
Figure C-2. Layout of piezometers for a pumping test.
C-2
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