The longest tunnel in Oregon is composed of two parallel tunnels, known as bores, which traverse the Tualatin Mountains. These tunnels play a vital role in extending the light rail service from downtown Portland to the cities of Beaverton and Hillsboro, serving the Red Line and Blue Line of the Metropolitan Area Express (MAX), the Portland area’s metro system. Within this extensive tunnel network, there is a single station in operation.
Construction of Oregon’s longest tunnel began after a meticulous planning phase of at least five years. In 1993, work commenced on the west side of the route, while the east side construction began a year later in 1994. The excavation on the west side involved the controlled use of explosives to tunnel into the mountainside, while on the east side, a powerful boring machine was employed.
However, the presence of loose rock beneath the mountain posed an unforeseen challenge, causing a nine-month delay as engineers sought solutions to overcome the impediment. Ultimately, a specialized cement was injected ahead of the boring machine to stabilize the crumbling rock, enabling progress.
The construction process was not without its complications. Challenges included managing the noise generated by the explosives, legal action to prevent the tunnel from passing beneath a cemetery (which was eventually resolved through an easement), and an incident where a congressional staffer slipped in muck during a tunnel inspection, leading to an ethics investigation following the reimbursement for her damaged suit.
Despite these hurdles, the east and west tunneling projects successfully met in December 1995, and the tunnel officially commenced operation in September 1998. Oregon’s longest tunnel spans a length of 2.9 miles, with each bore boasting a diameter of 21 feet. Trains navigate the entire length of the tunnel in approximately 5 minutes, including a stop at Washington Station, the sole station situated within the tunnel. During this brief journey, passengers traverse ancient basalt rock dating back up to 16 million years.
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Notably, Washington Station, located within the Robertson Tunnel, claims the distinction of being one of the deepest train stations in the western hemisphere and the seventh-deepest globally. Plunging 260 feet below ground, the station facilitates passenger access via two high-speed elevators that swiftly transport them to and from the surface.
The elevator ride, equivalent to ascending or descending a 26-story building, takes approximately 25 seconds. Symbolically, these two elevator stops are aptly labeled “The Present” and “16 million years ago,” marking the remarkable transition from the tunnel’s geological strata to the contemporary world above.