John Hart Dam Tunnel Portal Shoring

Project Description

A portion of the John Hart Dam Generating Station Replacement Project includes a bored tunnel to divert a large water line. Originally, the two tunnel portals were designed with sheet pile shoring walls to allow for an approach excavation to bedrock. However, prior to construction of the sheet pile walls it was determined that the soil conditions were too hard to drive sheet piles. SWC was subcontracted by the design-build general contractor to help design and then install permanent soil nail and shotcrete walls to replace the sheet pile walls. As the schedule was now critical, SWC worked with the design engineers to help minimize costs and delays. Prior to completion of the design, quantities were estimated and the long lead-time items were ordered. By the time the first round of materials arrived on site, SWC mobilized and began installation. SWC coordinated work between the two portal locations together with the excavation and general contractors to help minimize project delays. Variable soil conditions made this a difficult project for all involved, but in the end SWC successfully completed our scope of work within budget.