Geosynthetics August/September 2021 - 21

Case Study
Geosynthetic portable
cofferdams for civil
construction applications
By Brian Fraser and Mike Neal
C
offerdams are an enclosure built within or across a body of water to
allow the enclosed area to be dewatered. This creates a dry working
environment so construction can be carried out properly and safely.
Typical cofferdams are welded-steel structures consisting of sheet piles,
wales or cross braces, and are normally dismantled after construction.
However, new portable or temporary geosynthetic cofferdam systems
provide an effective alternative. These systems come in a variety of different
designs, materials and installation methods and provide a more
economical solution for temporary site dewatering versus conventional
structural cofferdams. Portable geosynthetic cofferdams are typically
lighter-weight modular systems produced from geomembrane and geotextile
fabrics. They limit the impact of construction-generated silt and
sedimentation when excavating in submerged or dredging areas, which
lessens the environmental impact. Most systems are also modular in
design, allowing for bends and turns in the project waterway. They can
also be installed and removed more quickly than standard structural
cofferdams, which makes them more cost-effective. Properly handled,
these dams can also be drained and reused, eliminating the need to
purchase a new dam for different projects in some instances. Common
applications for geosynthetic portable cofferdams include dewatering
for bridge foundations, dam repairs, pipeline crossings, irrigation canal
repairs, and shoreline construction and restoration. Smaller-diameter
geosynthetic dams are also used extensively for flood control barriers.
Figures 1, 2 and 3 show the installation of and some applications of
geosynthetic cofferdams.
For this article, the cofferdam system produced by the manufacturer
consists of two geomembrane tubes contained by a high-strength woven
geotextile outer tube. The two inner tubes are filled with water, which
creates a stable, nonrolling water-controlled structure. A center baffle
PROJECT HIGHLIGHTS
KILISUT HARBOR, WASH.,
COFFERDAMS
OWNER
Washington State Department
of Transportation
LOCATION
Kilisut Harbor, Wash.
CONTRACTOR
Seton Construction
DESIGN ENGINEER
Cardno Inc.
GEOSYNTHETICS PRODUCT
Aqua Dam Cofferdam
GEOSYNTHETICS MANUFACTURER
Layfield
Brian Fraser, MBA, is vice president
of Layfield Geosynthetics in
Lakeside, Calif.
Mike Neal is senior project manager
at Layfield USA in Eugene, Ore.
All figures courtesy of the authors.
www.GeosyntheticsMagazine.com
21
http://www.GeosyntheticsMagazine.com

Geosynthetics August/September 2021

Table of Contents for the Digital Edition of Geosynthetics August/September 2021

Geosynthetics August/September 2021 - Cover1
Geosynthetics August/September 2021 - Cover2
Geosynthetics August/September 2021 - 1
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Geosynthetics August/September 2021 - Cover3
Geosynthetics August/September 2021 - Cover4
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