As part of an ongoing pump station rehabilitation project in the Florida Bay area, a nationally recognized contractor was tasked with installing a saddle and valve for a line-tap on an existing 48-inch sanitary sewer force main. The contractor required an excavation cut of 32-ft long, 20-ft wide, and 15-ft deep to perform the upgrades. After examining the soil conditions, the Competent Person on-site classified the sandy, shell, lime rock soil as C-60.
The contractor needed a shoring system with the capability of straddling the existing large sewer line and protecting the surface encumbrances. Under a tight project deadline, the contractor teamed up with the local NTS representative and NTS’s in-house engineering team to devise an action plan. Weighing the contractor’s concerns, the NTS team presented a site-specific shoring solution that involved a double bay slide rail paired with two guide frames and a rolling strut. The contractor’s familiarity with the capabilities and installation process of the slide rail system would ensure the system was installed quickly. Additionally, the slide rail would provide positive pressure keeping the section of the adjacent road stabilized. Two guide frames were utilized as inner panels; steel sheets were inserted through the open channels of the guides and pushed to grade. The guide frames with sheeting would keep the surrounding soil from raveling while allowing the existing sewer pipe to pass through. The rolling strut positioned between the bays ensured uniform panel pressure and kept the slide rail parallel for the project’s duration.
With the site-specific shoring system in place system, the contractor began to install the saddle on the 48-inch force main and the valve on the line for the tap. The newly installed valve would allow a new line to be connected to the existing force main as part of the pump-station retrofit being performed. The saddle would ensure that the 48- inch main was properly supported and affixed to the existing pipe. The contractor was pleased with the site-specific shoring system and met the completion deadline. Not all protective systems are alike and using the proper protective system on a job can be the difference between project delays and cost overruns.