Opportunity
For a time during the Civil War, City Point, VA was the busiest port in the world, receiving hundreds of ships carrying supplies for the Union Army. Supplies were shipped to the front near Petersburg using the 9-mile City Point Railroad, which began operating in 1838.
In the course of more than 300 mergers, the tiny City Point Railroad grew into the Norfolk and Western Railway, a major rail company famous for manufacturing its own locomotives. It carried freight over the Appalachian Mountains, between ports in Virginia and cities in the Midwest
In 1982, Norfolk and Western merged with Southern Railway to form Norfolk Southern, now a Fortune 500 company. The former Norfolk and Western routes remained important, but tunnels and other obstructions forced double-stack trains crossing the Appalachians to make long detours: via Harrisburg to the north or Knoxville to the south.
To overcome this obstacle and streamline freight transportation, Norfolk Southern created a public-private partnership with the Federal Highway Administration and the states of Virginia, West Virginia, and Ohio. (See video.) Operational constraints required all work to be done in tightly constrained track windows.
Solution
In 2005, Norfolk Southern retained Mott MacDonald as prime consultant responsible for clearance improvements along the route between Walton, VA and Columbus, OH.
Mott MacDonald performed preliminary engineering, final design, and construction support for track lowering and improvements at 34 tunnels, five thru-truss bridges, and two overhead bridges.
Laser car measurements, topographic surveys, geotechnical borings, liner samples, and visual inspections were used to establish the existing baseline conditions and to evaluate the potential for tunnel modifications to provide additional clearance. Preliminary engineering studies were performed to develop a construction cost estimate and schedule for the project.
Mott MacDonald also analyzed the alternative solution of providing double track through one of the existing single-track segments. Preliminary designs were developed to produce the final bidding documents.
The Observational Approach was used to reduce the cost and duration of design phase field investigations to minimize impacts to the operating railroad. An adaptation of the Sequential Excavation Method, this approach requires construction phase monitoring by engineering and inspection staff who are familiar with tunneling and geology.
Outcome
Completed in 2010, the project cleared the way for trains that can carry a double stack of intermodal freight containers. The result is increased capacity, reduced transit time, a route 200 miles (322 kilometers) shorter, and less tractor-trailer traffic. Shipping containers unloaded at Norfolk, VA can now reach Columbus, OH in 24 hours.
Mott MacDonald's use of the Observational Approach allowed construction to be initiated earlier in the project cycle, reducing project delivery time and allowing the client to realize project benefits sooner.
As part of the project, one previously unlined tunnel with a history of rock falls was lined, and extensive improvements were made to drainage and asphalt underlayment was installed at several tunnels to control water infiltration and ballast contamination. These improvements have reduced the need for maintenance and improved the reliability of the corridor.
To preserve the historic and aesthetic qualities of the corridor, existing stone and concrete tunnel portals were preserved at most locations, and historic bridges were minimally modified.