Dewatering Plan Successful for Palm Beach Mall Renovation

1. 40 Utility Contractor | September 2007
W
hen the Palm Beach, Fla., area was growing
into the north end of the county, it became
apparent that a new shopping venue was
required. After all, these residents wouldn’t
want to travel all the way to the Island of Palm Beach to
shop at Sak’s Fifth Avenue or Nordstrom.
Pepper-Southern General Contractors of Atlanta was
hired by the owner (Forbes-Cohen Florida Properties) in
1988 to construct the new project, calling in Griffin
Dewatering to provide the proper methods and materials
to be utilized when dewatering the proposed structure’s
footings.
The proposed footings were designed to support both
floor slabs and structural columns, as well as the new
glass enclosed central elevator and adjacent water fea-
tures and fountains. The work was successfully conclud-
ed in 1999 and the mall opened with great success.
But now 19 years later, some of the shine is gone, the tile
grout is stained, the elevator is old and it’s time to give
the mall a facelift.
Flash forward to 2007, when the Ft. Lauderdale, Fla.,
office of Whiting-Turner General Contractors hired
Griffin Dewatering of South Florida to provide a work-
able dewatering plan to facilitate the demolition of old,
construction of new and maintain a “low profile” to
accommodate everyday mall business. Griffin com-
menced its portion of the project in April.
The Project
Griffin’s contract for services included dewatering of
excavated areas where the new Grande Fountain,
its control vault and the new elevator are to be
constructed. The problems that Griffin had to solve
were essentially three-fold. First it had to provide an
appropriate dewatering plan to facili-
tate excavation and placement of
underground plumbing lines, concrete
structures and fountain/pool shell.
In addition, the dewatering process
had to be environmentally compatible
so as not to disturb daily business of the
neighboring stores and eateries. As part
of its dewatering plan, it also had to face
challenges involving limited availability
of a disposal location for dewatering
effluent, in addition to working only at
night and after hours.
The solution was to first install a
perimeter wellpoint/wick point system
with one 12 in. x 15 ft long (or approx-
imately 7 ft below excavation bottoms)
screened and wicked wellpoints at 48 in.
+/- centers/horizontally. This procedure
minimized or eliminated soil movement
from adjacent existing footings and
Griffin was hired to provide a workable dewatering plan to facilitate the
“facelift” of a swanky mall in Palm Beach — all while maintaining a low
profile to accommodate everyday mall business.
Dewatering Plan Successful for Palm Beach Mall Renovation
By Terry Aylward

3. slabs by reducing hydrostatic groundwater pres-
sure to a point well below the excavated areas.
The dewatering pump was electrically powered
and placed in an enclosed box, thus noise level
was well below any audible level in the work area.
A typical wellpoint pump’s vacuum system is
mineral oil lubricated and sealed thereby emitting
hydrocarbon vapor during the cooling and sealing
process.
In this case, Griffin South Florida called upon
Griffin Southwest & Griffin Pump & Equipment
for an appropriate size of electrically powered well-
point pump with a water cooled/sealed vacuum
pump. It just so happened that a newly refurbished
Griffin model 4NCRE with a Travini vacuum pump
was available and suited this project perfectly.
The size was right to be placed inside the mall
(transported through service corridors), the
motor size worked with the available three phase power
and the general contractor installed a flexible steel
exhaust line to the adjacent ceiling fans to vent any water
vapor or groundwater odor.
For disposal of dewatering effluent, a floor drain was
available but only in 3-in. ID. This constituted a problem
as the anticipated dewatering effluent yield was on the
order of 500 gpm. Griffin installed a 300-ft long by 6-in.
ID discharge line under the existing floor slab (tile was
cut and replaced), through a service corridor and into an
outside service area where a 2,500-gal weir-type settling
tank aerated the groundwater prior to its disposal into the
on site drainage system.
The night work was the easy part, consisting on a shift
that started at 9:30 p.m. and concluded at 6 a.m. The dis-
charge line is to remain in place for future use by the owner
when draining or servicing the new water features. In the
end, the project has been considered a hugely successful
and Whiting-Turner expects work to be completed by
September.
TTeerrrryy AAyyllwwaarrdd is marketing manager for Griffin Dewatering, based
in Houston.
42 Utility Contractor | September 2007
Challenges included a limited locations for disposal of dewatering
effluent, in addition to working only at night and after hours.