A northeast contractor was tasked with constructing a new private commercial boat ramp that could provide a safer and more efficient alternative to launch different sizes of watercraft. The project would be located on a harbor near a busy airport. The project would require an excavation cut 195-ft long, 79-ft wide, and depths ranging from 2-ft to 25-ft. The soil type presented would vary according to the excavation’s depth. The first 10-ft of soil was composed of sandy silt followed by a solid layer of stiff clay that transitioned to a layer of loose sandy soil.
The initial phase of construction would require pumping water out of a predetermined work area so that the contractor could control and sufficiently dry the excavation, this would allow workers to pour the foundation structure of the concrete ramp. In order to perform the initial phase of the project, the contractor needed to install a site-specific system that could address several challenges that the site presented. The system would have to work well when addressing water and have the strength to withstand the aggressive tidal waves caused by sudden and rapid weather patterns. In addition, the location of the work area was in close proximity to an operational airport. The contractor would require a protective system with a minimal installation approach that could avoid any conflict with commercial and private aircraft landing restrictions.
As the contractor evaluated the challenges that the site presented, it became evident that a more comprehensive approach to the excavation and shoring expertise would be needed. The contractor contacted NTS to discuss the project and establish a game plan for the site. After reviewing a few options for the project, the contractor selected a system of steel sheeting supported by proprietary, high-strength internal hydraulic braces. The tight sheeting specified by the engineering plan would provide a barrier to water seeping into the excavation to support pumping operations. The engineered hydraulic bracing was specifically engineered to support the unique pressures exerted as a result of the system’s location.
The installation of the system 80 began by driving steel sheets to a predetermined depth with the use of a crane and vibratory hammer. Beams were welded together on the open end of the bracing pit. Walers were then bolted together and suspended from the walls of the steel sheeting with chains pinned at the corners. Hydraulic pressure was applied to expand the braces to the inside dimensions of the excavation. Once the internal hydraulic bracing was set along the perimeter of the excavation, large cross struts were assembled on the ground and lifted into place, and bolted to the hydraulic waler. Hydraulic pressure was applied to expand the struts to the span needed to support the loads across the pit. The contractor was highly impressed with how well the engineered system handled the water, the expertise of NTS’s team of engineers, and the overall support provided by NTS on this unique, complex project.