The contractor had been tasked with pouring in place a 17-ft square, 17-ft tall lift station for a Northern Virginia power station. The contractor had classified the soil as Type C-60. To complete the project an excavation of 18-ft deep and 30-ft squared would be required. This allowed the contractor to conduct the necessary preparations needed for the lift station to be poured. The site for the lift station was bordered by a road on two sides and had railroad tracks on another side. As a result of the adjacent environment, it was important that the protective system used for soil support would help to mitigate the impact of soil movement throughout the excavation process. The need to pour the lift station in place would also require an open span excavation to provide optimum efficiency for the crew throughout the project.
The contractor contacted NTS to discuss the project. NTS a few potential protective systems that could be used on the project. After a review of the possible systems, the contractor selected a Steel Sheeting Guide Frame System. The Steel Sheeting Guide Frame System was installed by digging a pilot trench and setting 4-ft tall “guides” along the edge of the excavation site. These guides are connected with linear posts that lock the system in place. In this excavation, a reinforcing beam was used along the edge to account for the large open-span area. Once the guide is set at the top, steel sheets are then inserted through open channels within the guides and pushed to grade. Sheets are advanced ahead of the excavator’s cut, so the system provides continuous soil support throughout the excavation process, thus minimizing soil disturbance. The contractor was extremely satisfied with the system, the support offered by NTS and its engineering team in furnishing the necessary documentation to allow the system to be used on this job, which needed to be approved by the power company owning the site given the adjacent structures surrounding the site.