AMTK: Proposed $400m Conn River Bridge Unveiled

Amtrak Presents Plans and Preliminary Design for Key Northeast Corridor Crossing, to Replace 113 Year-Old Drawbridge.

Adapted from articles by Cate Hewitt and Gregory, CT Examiner , 14/15.May.2020

12 May, Old Lyme CT – The estimated $400 million project, proposed by Amtrak, would construct a new 1600 ft, 10-span bridge 52 ft south of, approximately parallel to, the existing bridge. The existing bridge carries about 56 trains each day on the Northeast Corridor across the Connecticut River (38 Amtrak intercity trains, 12 Shore Line East commuter trains, and six freight trains) at no more than 45 miles per hour. The lift bridge opens and closes more than 3500 times a year to accommodate marine traffic.

The location of the new bridge, 52 ft to the south, means that the new rail bed only slightly diverges from the existing corridor. The western approach in Old Saybrook will benefit from a substantially shallower curve; to the east the new alignment reconnects to the existing tracks before crossing the Lieutenant River in Old Lyme.

Old Saybrook/Old Lyme CT

Amtrak cites multiple reasons for building a more expensive bridge that will cause disruption in the two coastal towns during contruction. Still functioning reliably under a considerable traffic load, the existing 1907 bridge sure doesn’t owe anyone a nickle. Proposed replacement structure will allow smoother, safer train crossings, and improved marine navigation {ctexaminer.com; annotated by ANRP}.

The proposed design includes nine static spans and one lift span set on nine caisson granite piers, and two sturdier abutments. The channel span is a bascule-style lift bridge (improved type of existing lift span). The current iteration of the design incorporates “low-shoulder” static spans, with only the catenaries standing more than a few feet above the railbed. This contrasts with the existing bridge’s high-humped trusses.

Old bridge was designed for expansion

The existing structure is the oldest movable bridge between New Haven CT and Boston MA {nec.amtrak.com}. Built in 1907, the existing bridge is a two-track, open deck, electrified railroad bridge, 1564 ft long, consisting of seven thru-truss spans, two deck girder spans, and one 158-foot Scherzer-type Rolling Lift span {hardestyhanover.com}.

The existing bridge piers were built wide enough to accommodate an additional two tracks. In theory, Amtrak could build a new bridge on the existing piers while the old bridge continues to function. That approach would be cheaper, and cause minimal disruption on the existing foundation and ROW. Instead, Amtrak is opting for an entirely new structure, and a new alignment of the west approach. Advantages of the more expensive and complex project include reduction in maintenance, a straighter rail alignment, better marine navigation, and contemporary tolerances for geo-seismic activity.

Existing piers were built for two additional tracks (four total) that were never added. {ctexaminer.com; annotated by ANRP}.

Boon to marine navigation

The new bridge will benefit marine navigation through the channel, by increasing clearance and improving vessel control. Vertical clearance in closed position will increase from 18 feet to 24 ft. In open position, vertical clearance will be unlimited for a 90 ft-wide beam, and at least 74 ft for the full 150 ft width of the channel. The existing structure provides 68 ft maximum vertical clearance in the open position.

A 2014 Environmental Assessment of the project identified navigation difficulties wherein an ebb tide current pulls marine vessels into Pier 5 (the west channel pier), due to the existing channel’s off-center location, close to the eastern shoreline. The new bridge design shifts the channel 14.5 ft westward, toward the center of the river. Channel width is also increased from 148 ft to 150 ft.

Long way to go

With a construction schedule currently scheduled for 6 years, from 2024-30. The construction, which will occur over a number of years, is significantly constrained by the lack of easy road access to the site, and likely presents the most concern for local residents in Old Saybrook and particularly in Old Lyme. The current structure will be entirely removed once the new bridge is completed, with only the existing abutments remaining.