Monday, April 24, 2017

US-1 Bypass+B&M over Piscataqua River between NH and ME

(Bridge Hunter, Satellite, Aug 2013 Photo, Webcams (if you click a view, then you can play back a time-lapse video of the view))

The official name is the Sarah Mildred Long Bridge. The original bridge was built in 1940 between Portsmouth, New Hampshire, and Kittery, Maine. It was built as part of a bypass to relieve the traffic on US-1 and the 1923 Memorial Bridge. The bridge also supported a Boston & Maine branch to South Berwick, ME. The Guilford Rail System/Pan Am/B&M branch has been cut back and now supports only the Portsmouth Naval Shipyard (95 photos). It also carried the traffic of I-95 across the river between 1960 and 1972 when the Piscataqua River Bridge and turnpike extensions were finally opened to carry road traffic high above the river with three lanes in each direction. The I-95 bridge is the steel arch bridge you see in the background of the following street view.

A replacement bridge was scheduled to be opened in Sept. 2017, but the old bridge was scheduled to be closed in Nov. 1, 2016. The old bridge must have been in really bad shape to plan forcing road traffic to use the interstate after the last the last train crossed it on Dec. 9, 2015. It was "carrying two loaded spent nuclear fuel flasks from Kittery Ship Yard en route to Idaho." [Bridge Hunter] But the lift span broke in August, 2016. Rather than spend the estimated $1 million to repair it, they just closed it a couple of months earlier than originally planed. Design of the new bridge started in 2013 and construction started in January, 2015. [MDOT]

[Wikipedia]

Street View of the building of the piers for the replacement bridge.
In addition to a lift span, the old bridge had a retractable steel girder span for the railroad deck that could let recreational boats pass without stopping road traffic. Because the railroad is used once in a blue moon to transport nuclear material to the ship yard, the retractable span that we see on the left side of the street photo below is normally open. That girder span was designed to raise up and then roll back into the truss. I included the "bridgeRare" label because of this span.

Street View of the retractable girder span as well as the lift span.
Now we turn our attention to the replacement bridge. The new bridge appears to use box girder concrete sections. Note the railroad deck has more piers than the road deck needs. But the extra piers are simple column piers.
MDOT
An artists' view from I-95.
MDOT
The second bullet point below explains why the lift span does not have two decks. The lift span is effectively designed for "street running" and is shared between the two decks. It is, of course, normally at the road deck level.

Key Bridge Attributes
  • New bridge alignment improves marine navigation by straightening the navigational channel, allowing larger ships to access the port and shipyard.
  • With a larger 56’ vertical clearance in its “resting” position, there will be 68% fewer bridge openings.  In the normal operating, “resting” position, the bridge’s lift span is at its middle level, allowing motor vehicles to cross the river. The new bridge’s movable “hybrid” span lifts up to allow passage of tall vessels and lowers to railroad track level for trains to cross.
  • 200’ tall precast concrete towers will support the 300’ long streamlined structural steel box girder lift span.
  • New bridge layout uses eleven (11) fewer piers than the existing bridge, also improving the gateway span leading into downtown Portsmouth by eliminating an existing median pier. 
[MDOT]

The use of one lift span that can carry both road and rail traffic and that can be positioned at three levels --- open, road traffic, and railroad traffic --- also justifies the "bridgeRare" label.

This is the Facebook posting that provided the name so that I could learn about this bridge.

Jim Browne posted
Dinner with a view. [In the case of Jim, the view is the many cranes.]
Justin Classen Sarah Mildred Long bridge I worked there for a year and a half.
Below zooms into the towers and the part of the railroad deck that is not completely obscured by crane barges. I'm sure the lift span is being built offsite and will be floated into place when the towers are ready for it. It looks like the towers are done except for the mechanical enclosure and equipment at the top. It appears from the concept art that the counterweights will be hidden in the towers.
At Facebook resolution






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