1. 1) Cofferdam
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A cofferdam on the Ohio River near
Olmsted, Illinois, built for the purpose
of constructing the Olmsted Lock and
Dam
A cofferdam during the construction of
locks at the Montgomery Point Lock and
Dam.
Construction
A cofferdam (also called coffer[1]) is an enclosure beneath the water constructed to
allow water to be displaced by air for the purpose of creating a dry work environment.
Commonly used for oil rig construction and repair, bridge and dam work, the
offerdam is usually a welded steel structure that is temporary, typically dismantled
after work is completed. Its components consist of sheeting, wales, and cross braces.
The cofferdam is also used on occasion in the shipbuilding and ship repair industry,
when it is not practical to put a ship in drydock for repair or alteration. An example of
such an application is certain ship lengthening operations. In some cases a ship is
actually cut in two while still in the water, and a new section of ship is floated in to
lengthen the ship. Torch cutting of the hull is done inside a cofferdam attached
directly to the hull of the ship, and is then detached before the hull sections are floated
apart. The cofferdam is later replaced while the hull sections are welded together
again. As expensive as this may be to accomplish, use of a drydock may be even more
expensive. See also caisson.
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2. Naval architecture
A cofferdam may also refer to an insulating space between two watertight bulkheads
or decks within a ship. A cofferdam may be a void (empty) space or a ballast space.
Cofferdams are usually employed to ensure oil or other chemicals do not leak into
machinery spaces. If two different cargoes that react dangerously with each other are
carried on the same vessel, one or more cofferdams are usually required between the
cargo spaces.
The division between the tanks and the hull of a double-hulled vessel is not normally
called a cofferdam, although it carries this function
Design and Construction of a Cofferdam at Former
MGP Site, St. Augustine, FL
Moretrench worked with ThermoRetec of Durham, NC to design and build a
cofferdam adjacent to a former MGP site in St. Augustine, Florida. Following
approval of a Remedial Action Work Plan (RAWP), and entry of the Administrative
Order on Consent (AOC) initiating site work, cofferdam construction began.
Cofferdam construction.
The purpose of the cofferdam was to provide a protective barrier for the Anastasia
River, and its marine life, from potential impacts of remedial activities at the former
MGP site. The cofferdam was built by driving sheet piles along the outer edge of a
marsh area, and placing successive lifts of reinforced geogrid, geofabric, and
compacted soil to build an earthen berm inside the sheet piles. The earth berm
provided the access forthe construction of the next day’s sheeting installation. Sheet
pile joints were sealed with a marine sealant to further minimize movement of water
through the piles.Drainage pipes and valves were installed through the cofferdam to
facilitate drainingof clean water from the marsh during low tides. Turbidity
monitoring results during and following construction were below action
levels.Despite challenges posed by the changing tidal conditions of the river, and the
unstable soil characteristics of the marsh,cofferdam construction was completed on
time and on budget.
MORE TRENCH
Contact Information:
11001 Fern Hill Drive
Riverview, FL 33569
Tel: 813/741-0256
Fax: 813/672-4754
E-mail:
aschuman@mtacfl.com
MORETRENCH
Services
Cofferdam and berm under construction.
Completed cofferdam.
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4. WELCOME TO GROUNDFREEZING
Ground freezing is a technique that has been used extensively for
groundwater control and excavation support in the underground
construction industry for over 100 years.
The process involves the
circulation of a
refrigerated coolant
through a series of
subsurface pipes to
convert soil water to ice,
creating a strong
watertight material. The
material is so strong, in
fact, that it is routinely
used as the only method
of groundwater control
and soil support for the
construction of shafts
hundreds of feet into water-bearing soils.
Most ground freezing systems are quite similar in principal. The
single most important co mponent of a ground freezing system is
the subsurface refrigeration
system, consisting of a series of
refrigeration pipes installed with
various drilling techniques.
Depending upon the application,
the coolant can be brought to
temperatures well below -150
degrees celcius.
Ground freezing can be achieved
by using either a large portable
refrigeration plant or liquid
nitrogen. After the initial freezing
has been completed and the
frozen barrier is in place, the required refrigeration capacity is
significantly reduced to maintain the frozen barrier.
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