TM 5-815-5/AFM 88-5, Chap 6/NAVFAC P-418
(1) If the specification is to be of Types A-1 and
devices for monitoring performance of the system(s).
A-2 described in paragraph 7-2a(1) and (2), the de-
(f) A plan and schedule for monitoring perform-
sired results should explicitly specify the level to
ance of the system(s).
which the groundwater and/or piezometric surface
(g) A statement that the dewatering system(s)
should be lowered; give recommended factors of safety
has been designed in accordance with the principles
as set forth in paragraph 4-8; require that all perma-
and criteria set forth in this manual.
nent work be accomplished in the dry and on a stable
(h) The seal of the designer.
subgrade; and advise the Contractor that he is respon-
(This type of specification should not be used unless
sible for designing, providing, installing, operating,
the Government or Owner has or employs someone
monitoring, and removing the dewatering system by a
competent to evaluate the report and design submit-
plan approved by the Contracting Officer or the Engi-
ted, and is prepared to insist on compliance with the
neer. This type of specification should note the limita-
above .)
tions of groundwater information furnished since
7-3. Data to be included in specifica-
seepage conditions may exist that were not discovered
tions. All data obtained from field investigations re-
during the field exploration program. It should be
lating to dewatering or control of groundwater made
made clear that the Contractor is not relieved of re-
at the site of the project should be included with the
sponsibility of controlling and disposing of all water,
specifications and drawings or appended thereto.
even though the discharge of the dewatering system
These data should include logs of borings; soil profiles;
required to maintain satisfactory conditions in the ex-
results of laboratory tests including mechanical analy-
cavation may be in excess of that indicated by tests or
ses, water content of silts and clays, and any chemical
analyses performed by the Government. This type of
analyses of the groundwater; pumping tests; ground-
specification should not only specify the desired re-
water levels in each aquifer, if more than one, as meas-
sults but also require that the Contractor provide ade-
ured by properly installed and tested piezometers, and
quate methods for obtaining them by means of pump-
its variation with the season or with river stages; and
ing from wells, wellpoint systems, cutoffs, grouting,
river stages and tides for previous years if available.
freezing, or any other measures necessary for particu-
Borings should not only be made in the immediate vi-
lar site conditions. The method of payment should also
cinity of the excavation, but some borings should be
be clearly specified.
made on lines out to the source of groundwater flow or
(2) Prior to the start of excavation the Contractor
to the estimated "effective" radius of influence. Suffi-
should be required to submit for review a proposed
cient borings should be made to a depth that will de-
method for dewatering the excavation, disposing of
lineate the full thickness of any substrata that would
the water, and removing the system, as well as a list of
have a bearing on the control of groundwater or unbal-
the equipment to be used, including standby equip-
anced uplift pressures. (Additional information on
ment for emergency use. (This plan should be detailed
field investigations and the scope of such are given in
and adapted to site conditions and should provide for
chap 3.) It is essential that all field or laboratory test
around-the-clock dewatering operation.)
data be included with the specifications, or referenced,
(3) Perimeter and diversion ditches and dikes
and that the data be accurate. The availability, ade-
should be required and maintained as necessary to pre-
quacy, and reliability of electric power, if known,
vent surface water from entering any excavation. The
should be included in the contract documents. The
specifications should also provide for controlling the
same is true for the disposal of water to be pumped
surface water that falls or flows into the excavation by
from the dewatering systems. The location and owner-
adequate pumps and sumps. Seepage of any water
ship of water wells off the project site that might be ef-
from excavated slopes should be controlled to prevent
fected by lowering the groundwater level should be
sloughing, and ponding of water in the excavation
shown on one of the contract drawings.
should be prevented during construction operations.
Any water encountered in an excavation for a shaft or
7-4. Dewatering requirements and spec-
tunnel shall be controlled, before advancing the exca-
ifications. The section of the specifications relating
vation, to prevent sloughing of the walls or `boils" in
to dewatering and the control of groundwater should
the bottom of the excavation or blow-in of the tunnel
be prepared by a geotechnical engineer experienced in
face. If the flow of water into an excavation becomes
dewatering and in the writing of specifications, in co-
excessive and cannot be controlled by the dewatering
operation with the civil designer for the project. The
system that the Contractor has installed, excavation
dewatering specifications may be rather general or
should be halted until satisfactory remedial measures
quite detailed depending upon the type of specification
have been taken. Dewatering of excavations for shafts,
to be issued as described in paragraph 7-2.
tunnels, and lagged open excavations should continue
a. Type A specifications.
for the duration of the work to be performed in the ex-
7-2
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