TM 5-815-5/AFM 88-5, Chap 6/NAVFAC P-418
measure well flow. Certain wells shall be provided
quacy of the deep-well system will be evaluated on the
with a tee and blind flange for connection of an 8-inch
basis of the pumping test made upon completion of
discharge hose in event of damage or failure of the
unwatering of the excavation, for a Red River stage of
main discharge header pipe. The Contractor shall con-
elevation 60 feet. If at the end of the pumping test, an
struct splash facilities for discharge water at the
analysis of the data by the Contracting Officer or his
dredge channel. The Contractor shall maintain the dis-
C.O.R. indicates the system to be adequate, it will be
charge splash facilities so as to prevent erosion or dam-
approved; if the dewatering well system appears to be
age to the channel slopes and to modify such if found
inadequate, for a design Red River stage of elevation
necessary.
60 feet, the Contracting Officer will direct the Con-
tractor to install additional dewatering wells, pumps,
(7) Pumping test on the dewatering systems.
(a) After the deep-well dewatering system is
engines, and necessary pertinent piping and fittings
completely installed, a pumping test shall be made on
for which he will be compensated as an extra.
the entire system by pumping all the wells at the same
(e) If it appears, while unwatering the Phase I
time at a constant pump speed or flow rate for each
excavation and the second pumping tests on the deep-
well, the pumping rate to be determined by the C.O.R.
well system, that the groundwater table in the top
prior to the test. If the selected pumping rate lowers
stratum has not been adequately lowered by the speci-
the water level in any well below the pump bowl, the
fied jet-eductors wells and pumping the deep-well sys-
engine speed shall be reduced or the discharge valve
tem, the Contractor shall install whatever additional
partially closed so that the water level in that well is
jet-eductor wells, pumps, and piping considered neces-
sary by the C.O.R. for which he will be compensated as
not lowered below the pump bowl.
(b) This test, the first, shall be made prior to
an extra.
starting to unwater the Phase I excavation. The wells
e. Jet-eductor well system.
shall be pumped continuously for at least 24 hours and
(1) Scope. The work provided for herein consists
for not more than 48 hours as required by the C.O.R.
of furnishing all labor, material, equipment, and tools
The Contractor shall have previously installed the M
to install, develop, and test pump the jet-eductor wells
piezometers around the perimeter of the excavation,
to be installed around the perimeter of the excavation
the R, S, and T piezometers on lines out from the exca-
at the locations shown on the drawings and as speci-
vation, and provision has been made to measure the
fied herein.
flow as shown on the drawings and specified herein.
(2) Design. The jet-eductor wells to be installed on
the upper berm around the excavation at elevation 28
The C.O.R. will keep a systematic record of discharge
throughout the test period and will record the water
to 34 feet are to intercept the seepage from silt, sandy
silt, silty sand, and sand strata which are penetrated in
level in the piezometers and wells immediately prior to
commencing the test and at certain intervals thereaf-
some areas by the outer excavation slopes. The pur-
ter. The pumping test shall be conducted under the
pose of the jet-eductor wells is to lower the groundwa-
general direction of the C.O.R. with the Contractor be-
ter table below the slopes of the main excavation and
ing responsible for actual operation of the system.
to prevent any detrimental raveling or instability of
(c) If an analysis of the pumping data by the
the slopes caused by seepage. The jet-eductor wells
Government indicates probable adequacy of the sys-
shown on the contract drawings and as specified here-
in have been designed to lower the groundwater table
tem, the Contractor may start unwatering the Phase I
excavation while continuing to operate the dewatering
in the upper silts and sands to within about 2 or 3 feet
well system so as to maintain the groundwater table in
of the contact with any underlying impervious
the deep sand formation, as indicated by the M piez-
stratum where shown on the drawing. However, other
ometers installed around the top of the excavation, 3
reaches of the outer excavated slopes than shown on
to 5 feet or more below the water level in the excava-
the drawings may require dewatering or drainage. If
observations indicate the need for dewatering other
tion.
(d) After the Phase I excavation is unwatered,
reaches of the outer slopes, the Government will
all wells shall be pumped at a constant rate to be pre-
design the supplemental jet-eductor wells and system
scribed by the C.O.R. for at least 48 hours and not
and furnish the design to the Contractor for installa-
more than 120 hours, as determined by the C.O.R., as
tion. The Contractor will be reimbursed for the cost of
a further check on the adequacy of the dewatering well
any supplemental wells, jet-eductor pumps, and piping
system with the excavation unwatered. As during the
when completely installed and ready for operation, as
first test, the rate of flow from each well and the en-
an extra. The Contractor shall be fully responsible for
tire system shall be measured throughout the test pe-
controlling the groundwater table and seepage from
riod, and the water level in the M, R, S, and T piezom-
and below the main excavated slopes as specified
eters and in the dewatering wells will be measured and
herein, and for proper installation, operation, mainte-
recorded at certain intervals during the test. The ade-
nance of the specified jet-eductor wells, and any sup-
G-17
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