Simmons Point Flood Wall
BackgroundSimmons Point, a waterfront residential community just a few miles from Charleston, needed a solution quick. FEMA remapping of Mt. Pleasant and the surrounding area had recently determined their land a high risk flood zone. The Simmons Point HOA’s mandatory flood insurance was scheduled to increase from $40,000 to over $400,000 a year. Simmons Point needed a water control solution to avoid a permanent and drastic increase in yearly dues.
Project ScopeCMI’s AlumiGuard sheet piling provided a solution for a very similar project just a few miles away from the Simmons Point complex. The Tides, another residential community in Mt. Pleasant, had installed a flood wall a few years ago using AlumiGuard sheet pile and cap. Simmons Point researched the success of the nearby Tides flood wall and elected to build a similar wall of their own. Aluminum sheet piling was chosen for both of these projects as it offers a long life solution while handling heavy loading and requires little to no maintenance once installed. Engineers designed a flood wall composed of over 1000 feet of AlumiGuard sheet pile and cap for Simmons Point. The project hit a few obstacles during the permitting phase as environmental restrictions required that several old oak trees along the project’s flood wall line be kept to meet environmental restrictions and maintain the attractive waterfront setting. In addition, South Carolina’s Ocean and Coastal Resource Management organization prevented crews from trenching to discover and avoid tree root systems along the path of the proposed flood wall. These design hurdles encouraged engineers to be innovative by including small sections of concrete panels supported by H beams which would avoid disturbing the root systems during installation. This modification saved the established oaks but will require yearly maintenance programs as both the steel and the concrete will need thick, continuous coatings to prevent salt water corrosion. The Simmons Point project contained yet another innovative design feature: a custom AlumiGuard gate. This gate when properly closed can perform in drastic flooding scenarios yet also provides pedestrian access when pinned open. Gator’s team of experienced design engineers and aluminum welders fabricated this unique solution.
PerformanceCMI’s marine grade aluminum is a perfect sheet piling material for areas along the central and southern coast. Aluminum’s high strength to weight ratio provides proven flood protection yet makes it an easy material to install. Additionally, aluminum remains cool to the touch even in strong sun and does not corrode in salt water. In fact, aluminum, when exposed to the elements naturally develops a chemical defense system that protects against weathering so it needs little to no maintenance during its long life span. Aluminum’s inherent stiffness and durability are maximized in the extruded profiles that AlumiGuard offers. The Simmons Point project was designed using 22 foot long sheets of PZH 159 AlumiGuard piling along with a small section of 14 foot long PZM 16 sheets. The wall design added additional strength by using AlumiGuard’s SC 9 and SC 15 caps.
ConstructionConstruction was done with a single crew of 4 men driving AlumiGuard sheet piling with a MKT V2 vibratory hammer and 30,000 lb. crawler crane. The soil conditions ranged from sandy/clays to high PI organic clays. The aluminum sheets provided stiffness for quick installation and driven at a rate of 175 feet a day. The design in these sections directed crews to drive steel H beams and attach thick concrete panels between two beams. After the first crew made headway, a second crew was brought in to install the aluminum cap and attach the coated concrete sections.
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