The City of Fort Collins (Colorado) recently completed construction of a tunnel underneath BNSF Railway tracks to connect more than 30 miles of trails. The prospect of tunneling under an active rail line is a pretty big deal, and the railroad had strict requirements. The original concept of the tunnel was modified by the contractor and their engineer to utilize secant pile retaining walls to allow the construction of the portals closer to the rail line and decreasing the overall tunnel length. The tunnel was constructed by BT Construction and Lithos Engineering was their design engineer. Yenter construction was responsible for the retaining walls, including segments of sheet pile wall used to start things off. Anderson Drilling constructed the shafts for the secant pile wall and for the thrust wall. Read more about the project at TBM.
The Port Authority of Allegheny County (Pittsburgh, Pennsylvania) has a major transit improvement project dubbed the North Shore Connector. Its main components are twin bored tunnels 1.2 miles long that will connect the Port Authorityâ€™s Light Rail Transit system, the T, 1.2 miles from the Gateway Subway Station underneath Stanwix Street and the Allegheny River to the North Shore. It will travel under the river and provide three new stations and allow for future improvements beneficial to future development and continued downtown revitalization. The $435 million project is making news recently for cost increases, drawing comparisons to Bostonâ€™s Big Dig much to the dismay of the Port Authority. Read on for project maps, links and more info.