TM 5-815-5/AFM 88-5, Chap 6/NAVFAC P-418
pressure on the pump can be varied as the test pro-
ured, and the elevation of the top of each accurately
gresses to keep the rate of flow constant.
determined. Each piezometer should be capped with a
(2) During a pumping test, it is imperative that
vented cap to keep out dirt or trash and to permit
the rate of pumping be maintained constant. Lowering
change in water level in the piezometer without cre-
of the water level in the well will usually cause the
ating a partial vacuum or pressure. The test well and
pumping rate to decrease unless the valve in the dis-
piezometers should be carefully installed and devel-
charge line is opened to compensate for the additional
oped, and their performance checked by individual
head or lift created on the pump. If the pump is pow-
pumping or falling head tests in accordance with the
ered with a gas or diesel engine, changes in tempera-
procedures discussed in chapter 5 of the main text.
ture and humidity of the air may affect appreciably
b. Pumps.
the operation of the engine and thus cause variations
(1) The test pump should be a centrifugal, or more
in the pumping rate. Variations in line voltage may
preferably, a turbine or submersible pump. It should
similarly affect the speed of electric motors and thus
be capable of lowering the water level in the well at
the pumping rate. Any appreciable variation in pump-
least 10 feet or more depending upon the characteris-
ing rate should be recorded, and the cause of the varia-
tics of the formation being tested. The pump should
tion noted.
preferably be powered with an electric motor, or with
(3) The flow from the test well must be conveyed
an engine capable of operating continuously for the
from the test site so that recharge of the aquifer from
duration of the test. The pump discharge line should
water being pumped does not occur within the zone of
be equipped with a valve so that the rate of discharge
influence of the test well.
can be accurately controlled. At the beginning of the
c. Flow and drawdown measurements.
test, the valve should be partially closed so that back
U.S. Army Corps of Engineers
Figure C-3. Section of well and piezometers for a pumping test with gravity flow near well.
C-3
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