A contractor was tying in a new development’s sewer and water reclamation systems to the municipal infrastructure and needed to provide its crew with a safe working environment during that process.  The manhole installation and tie-in for this phase of the project would require an excavation depth of approximately 12-ft in a rock, clay soil the Competent Person had classified as Type B.

The project was located in a rural area, with a small road running alongside the excavation site. The installation of the manhole would require an open span area of around 9-ft square to set the manhole structure. The contractor elected to use a stacked set of steel trench manhole shields for this project. Steel manhole shields are designed for these types of infrastructure projects requiring a small, fixed-size open span area as the shield provides solid, four-sided protection, while also allowing access for lines to enter the shield through open ends, or alternatively, cut-outs which are available on some manhole shields.  Since the soil type was a good cohesive “B” soil; the contractor utilized hydraulic vertical shores to provide the necessary soil protection to get the pipe to the manhole shield.  The systems integrated well and allowed the contractor to safely and effectively complete the work. The contractor was extremely satisfied with the condition of the equipment when delivered and the support services offered by National Trench Safety, including very prompt delivery and pick-up of the equipment.