TM 5-815-5/AFM 88-5, Chap 6/NAVFAC P-418
the dewatering system will be made at the applicable
daily supervision by someone skilled in the operation,
contract lump sum price for "Removal of A-l Test
maintenance, and replacement of system components;
Stand Dewatering System." However, if the Contrac-
at least one spare submersible pump and controls and
tor so elects to sell the installed and operating system
one pressure pump of the same capacity as specified;
to the succeeding Contractor or to dispose of the sys-
and any other work required by the Contracting Offi-
tem in place by other means, as approved by the Con-
cer to maintain the excavation in a dewatered and
tracting Officer, the Contractor shall be relieved from
hydrostatically relieved condition. Dewatering and
the requirements of the specified removal work and no
pressure relief shall be a continuous operation and in-
payment will be made for this item.
terruptions due to power outages, or any other reason,
shall not be permitted. Some responsible person shall
G-5. Example of type B-1 specifications
also monitor the dewatering sump pumping, and
(dewatering and pressure relief).
pumping the relief wells continuously until the suc-
ceeding contractor assumes the responsibility for such,
a. Scope. This section covers furnishing, installa-
and the Contractor has received a written instructive
tion, operation, maintenance, and removal of the jet-
that he or she is no longer responsible for this oper-
eductor wellpoint and pressure relief well systems, as
ation.
subsequently specified in this section; control of any
(2) The Contractor shall also be fully responsible
seepage from the soils above the bottom of the excava-
for any failure of any component of the systems. The
tion not intercepted by the jet-eductor wellpoint sys-
Contractor shall be responsible for all damages to
tem deemed necessary by the Contractor to permit in-
work in the excavation area and for damages to any
stallation of the sheeting shown to grade as specified;
other area caused by failure to maintain and operate
pumping of surface water or seepage through the
the dewatering and pressure relief systems as speci-
sheeting during excavation or after the jet-eductor de-
fied.
watering system is turned off or removed; and install-
ing any additional pressure relief wells, pumps, and
c. Wellpoint and pressure relief systems.
appurtenances, if necessary, to maintain the hydro-
(1) General. The jet-eductor wellpoint system
static water level in the clayey silty sand and sandy silt
specified is to lower the groundwater table adjacent to
(semipervious) stratum (about el 235 1 foot) beneath
the excavation and intercept seepage from the sandy
the excavation at all times.
and gravelly soil above the Cockfield formation (at
about el 253.0 feet) so that excavation and placement
b. Responsibility. The Contractor shall be fully re-
of the wood sheeting and pea gravel backpack can be
sponsible for furnishing, installing, operating, main-
accomplished with minimum difficulty, and with little
taining, and removing all wellpoint, pressure relief,
if any sloughing of the soil from the cut slope. The
and seepage or surface water control systems. How-
wellpoint system combined with a sump ditch between
ever, any pressure relief wells, pumps, piping, and
the sheeting and edge of structural mat when properly
electrical wiring and controls required to lower and
installed, maintained, and pumped should permit plac-
maintain the hydrostatic water level in the semiper-
ing the "mud" mat on foundation soils free of any sur-
vious stratum below the bottom of the excavation, oth-
face water. If the Contractor considers the spacing of
er than the pressure relief system specified, will be
the wellpoints inadequate to accomplish the excava-
paid for as an extra.
tion and placement of the wood sheeting, as specified,
(1) The Contractor shall be responsible for:
he or she should space the wellpoints closer. The well-
(a) Installing and testing the wellpoint and pres-
point system shall remain in continuous operation un-
sure relief systems as specified.
til the excavation has been dug to grade and the "mud"
(b) Dewatering or controlling any seepage from
mat poured. After the "mud" mat has been placed, the
the soils above the bottom of the excavation so that
wellpoint system may be turned off and any seepage
the sheeting may be installed without any significant
through the wood sheeting removed by sump pump-
sloughing of earth during excavation and placement of
ing. After the "A" piezometers for monitoring the
sheeting and pea gravel backpack.
groundwater table above the Cockfield formation and
(c) Maintaining the hydrostatic water level in
the wellpoint system have been installed, the system
the semipervious stratum below elevation 250.0 feet
shall be tested for flow and groundwater lowering pri-
at all times.
or to starting any excavation. The well system is to re-
(d) Maintaining the bottom of the excavation
lieve excess hydrostatic pressure in the semipervious
free of all seepage or surface water until the structural
stratum below the excavation to insure no heave of the
mat has been placed and the waterproofing installed
soil strata above this stratum. It is imperative that no
up to the top of the mat.
heave of the soil strata above the semipervious stra-
(e) Operating, maintaining, and monitoring the
tum occur inasmuch as the building will be founded di-
wellpoint and pressure relief well systems. System
rectly on the foundation soils above this stratum.
maintenance shall include but not be limited to at least
G-4
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