TM 5-815-5/AFM 88-5, Chap 6/NAVFAC P-418
ditional jet-eductor wells may be required to control
c. General. The dewatering systems shall be in-
seepage from other sections of the slopes around the
stalled, operated, and maintained so as to reduce the
excavation. As shown by the boring logs and subse-
artesian pressure in the sand formation below the ex-
quently referenced reports, the stratification of the
cavation, and control seepage from any excavated
top stratum soils above the deep sands is erratic (more
slopes or into the bottom of the excavation as specified
so in some areas than others). The deep wells and jet-
below, so that the work covered under this contract
eductor wells, subsequently installed around the top or
can be accomplished in stable areas free of water and
upper berm for the excavation, may or may not com-
without heaving of soil strata overlying the sand aqui-
pletely dewater or stabilize all slopes or areas in the
fer within the cofferdammed area.
(1) Dewatering requirements. Construction de-
bottom of the excavation. Dewatering facilities for
watering to be performed by the Contractor shall con-
control of groundwater in the lower part or bottom of
sist of:
the excavation, if required, shall be designed by the
(a) Dewatering lock and dam excavation by
Contractor subject to approval of the Contracting Of-
ficer. Facilities for unwatering the Phase II excava-
pumping from deep wells; jet-eductor wells; and any
tion, and controlling and sump pumping surface wa-
other supplemental groundwater control facilities if
required.
ter, shall be designed by the Contractor.
(b) The Contractor shall submit for approval by
(b) Unwatering the Phase I excavation.
the C.O. within 15 calendar days after receipt of No-
(c) Testing adequacy of deep-well system prior
to and after unwatering the Phase I excavation. Eval-
tice to Proceed complete information regarding meth-
uation of the adequacy of the jet-eductor system after
ods and equipment he or she proposes to utilize for in-
unwatering the excavation.
stalling the jet-eductor wells and pumping the dewa-
(d) Controlling and removing of surface water
tering wells required by these specifications. The Con-
falling into the excavation.
tractor shall at the same time submit detailed design
The dewatering systems for Phase II excavation for
data and drawings for the system he or she plans for
controlling surface water and unwatering the excava-
the lock and dam shall be constructed in accordance
with the details shown on the drawings and the re-
tion for the Phase I work. The material to be submitted
quirements herein specified. The dewatering systems
shall include, but not necessarily be limited to, the fol-
shall be installed and operated by the Contractor to
lowing: capacities and characteristics of all well and
control seepage from any excavated slopes or the bot-
jet-eductor pumps, engines, gear heads, flexible cou-
tom of the excavation so as to assure a stable work
plings, and standby equipment; description of equip-
area at grade and prevent raveling or sloughing of ex-
ment and procedures he or she proposes to use for in-
cavated slopes, and to lower the hydrostatic water lev-
stalling the dewatering wells, jet-eductor wells, and
el in the deep underlying sand formation so that as the
any supplemental dewatering facilities, if required, in
excavation progresses the piezometric heads and
the bottom or lower part of the excavation; calcula-
groundwater table are maintained at least 5 feet below
tions and drawings of dikes, ditches, sumps, pumps,
the bottom of the excavation and 3 feet below the
and discharge piping for unwatering the Phase I exca-
slopes at all times, as measured by construction pie-
vation and for controlling surface water; and a de-
zometers. After the hydrostatic water level in the deep
tailed description of his or her procedures and plans
sand formation has been lowered to the required levels
for supervising the installation, operation, and mainte-
beneath the excavation, it shall be maintained at the
nance of the dewatering systems to insure that the sys-
required elevations so that all testing and construction
tems are installed as specified herein and that they are
operations can be performed in the dry without inter-
operated and maintained so as to preserve the systems
ruption.
in first class working conditions subject to normal
(2) Design of dewatering systems. The (dewater-
wear, throughout the life of this contract.
ing) well system has been designed to lower the hydro-
(c) Approval by the Contracting Officer of the
static water level to elevation -26.0 feet in the deep
plans and data submitted by the Contractor shall not
sand formation beneath the excavation for the dam
relieve the Contractor from the responsibility for con-
and to elevation - 35.0 feet beneath the lock (or below)
trolling surface water, seepage, and artesian head and
with a river stage at elevation 60.0 feet, with as many
groundwater levels in the excavated areas as, and to
as two to five well pumps off depending on their loca-
the extent, specified herein.
tion.
(3) Responsibility. The Contractor shall be fully
(a) The jet-eductor wells (indicated by borings
responsible for furnishing, installing, operating, and
made in and around the excavation) have been de-
maintaining the dewatering and jet-eductor well sys-
signed to drain semipervious soils in the top stratum
tems, as specified, and any other seepage and surface
to prevent or minimize any detrimental seepage from
water control systems required for control of ground-
the (main) excavated slopes around the excavation. Ad-
water as herein specified. However, any jet-eductor or
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