Complex Project Requires Slide Rail Shoring System

November 2009 Vol. 64 No. 11
Chris Acord is the construction manager for Pipeline Utilities Inc.

The final complicating issue was the large pipe that needed to be installed. For comparative purposes, a standard trench shield may yield about 65 inches of vertical pipe clearance under the pipe spreaders. The larger of this new pipe being installed would require up to 102-inches of vertical clearance, clearly in excess of the conventional pipe clearances for most systems.

All of these factors culminated into a very challenging project and one in which the contractor would have to rely heavily on the fact that the chosen shoring supply firm would have to perform as promised. Pipeline Utilities Construction Manager Chris Acord knew the project would require a demanding shoring system.

Acord said, "we knew early on that with this project’s depth, soil conditions, pipe size and time schedule, the standard trench box shoring was just not going to be an option. We felt that the contractor that came up with the best shoring solution was probably going to get this project. We have relied on Coble Trench Safety for our shoring needs for many years and brought them onto this project early in the bid process. They recommended looking at a slide rail system from the very beginning and that is what we ended up going with.”

Solution
Coble Trench Safety Specialists Brett Sondergard and John Knighten met with Pipeline Utilities very early in the bid phase for this project and looked at all parameters surrounding the project. A plan was put in place with accurate costs that would be needed before the bid. As always, the plan could be subject to change. However, it provides a reasonable approximation of the shoring cost as well as other costs such as an appropriately-sized excavator to work with the shoring system. During these initial meetings, a wide range of alternatives were discussed. For example, steel trench shields could be modified with steel arch spreaders to achieve the needed pipe clearance of 102 inches; however, this system would require significant engineering to determine the viability of the system at the required depth, as well as the issues that would be created involving the weight of this type of system.

After discussing a number of alternatives, a combination of linear slide rail system and pit style slide rail with steel sheeting guides became apparent as the best way to shore the excavation.