was used for the first time, to protect the city from Hurricane Isaac. By June 2013, all major construction had been completed. Construction The COE accomplished this project via the design-build delivery method. The main barrier consists of 1,271 concrete piles across and long, weighing 96 tonnes each. Behind those piles, steel piles are driven at an angle of 2 horizontal to 3 vertical. The steel piles are 288 feet long and are installed in two sections, with the lower 158-foot section driven and the upper 130-foot section fitted on top and welded in place. A precast concrete pile cap is placed on top of the steel batter piles and concrete plumb piles to join them. Two gates were constructed in the Gulf Intracoastal Waterway navigation channel. One gate is closed with two sector gate leaves, the other gate with a barge swing gate, comparable to a caisson. In the Bayou Bienvenue navigation channel, a vertical lift gate was installed for use with recreational craft and shrimpers. Features Typical flood wall and the MRGO closure flood wall (over a mile long) 150-foot wide navigable floodgate on the GIWW—a steel sector gate (42 feet tall) 150-foot wide navigable bypass floodgate on the GIWW—a concrete barge swing gate 56-foot wide navigable floodgate on Bayou Bienvenue—a steel lift gate Concrete T-walls on land, at the north and south ends of the Lake Borgne barrier Approach walls at the GIWW sector gate and the Bayou Bienvenue gate Navigation gate in the Seabrook vicinity Marsh enhancement with dredged organic material - As organic material is dredged from waterways in preparation for new construction, it will be deposited in nearby wetlands habitats to enhance environmental conditions Engineering COWI Marine North America, formerly Ben C. Gerwick, Inc., provided the detailed designs and drawings for The main barrier, including the flood wall and the MRGO closure The GIWW sector gate monolith walls and foundation The GIWW bypass concrete barge swing gate The GIWW bypass concrete barge swing gate mechanical operating systems Approach walls at the GIWW sector gate Scour stone protection for the barrier and gates INCA (now TETRA TECH, INC.) provided the detailed designs and drawings for: GIWW Sector Gate GIWW Bypass Approach Walls Bayou Bienvenue Lift Gate Monolith Bayou Bienvenue Tower and Bridge Bayou Bienvenue Lift Gate (with Waldemar Nelson) Bayou Bienvenue Approach Walls Sources External links US Army Corps of Engineers New Orleans District Web