Geosynthetic portable cofferdams for civil construction applications curtain is installed for stability, reducing movement or tipping as a result of hydrodynamic loading. The local water source is normally used to fill the inner tubes of the dam. This cofferdam system was first introduced in the early 1990s and is constructed in a range of sizes from 4-16-foot (1.2-4.9-m) diameter in standard 100-foot (30-m) and 200foot (61-m) lengths. Special connecting collars are used to join the dams during installation. Standard fill and drain ports are installed into each dam. Installation of the dams requires trained technicians and equipment and can be far more difficult in moving water applications than slow or still water projects. Special patch kits and repair techniques are used in the event the dams are punctured during the installation or in application. Figure 4 shows the modular capabilities of the portable cofferdams. FIGURE 2 Installation of 6-foot (1.8-m) cofferdams in Eagle River, Colo. Design and engineering This section summarizes the system stability and engineering needs of waterfilled manufacturer's dams. System stability is critical to the successful use and installation of portable cofferdams. The basic principle behind the water-filled dam system incorporates a dual inner tube system with a center baffle to stabilize the structure. The safety factor against sliding depends greatly on the coefficient of friction of the material that the dam is sitting on. In this case, where it is sitting on a wet grass surface, the coefficient of friction used is 0.20 (Noon 1994). The factor of safety against sliding is 1.33 when 24 inches (61 cm) of water is being held back. As the water builds on one side of the dam, the inner tubes prevent rolling, and the dam behaves as a solid barrier. Engineering designs with properly FIGURE 3 U.S. Army Corps of Engineers 10 × 8-foot (3.0 × 2.4-m) cofferdam in Baytown, Texas 22 Geosynthetics | August September 2021 calculated safety factors are required based on individual manufactured