KITTERY, Maine — The final design of the new Sarah Mildred Long bridge connecting Portsmouth, N.H., and Kittery via the Route 1 Bypass, is nearing completion.
On Wednesday evening, about 100 people gathered at the Kittery Community Center to learn about the innovative design.
The project is being led by FIGG Engineering and Hardesty & Hanover, a firm that has been building bridges since 1887.
The new Long bridge will feature technologies that have never been used in the United States, but were recently used in a joint Figg/Hardesty & Hanover project in Bordeaux, France.
Construction of the new bridge is scheduled to begin in the fall of 2014 and be complete by late 2017. The bridge is being constructed offline of the existing bridge, which will allow it to remain open for much of the construction process.
Linda Figg said the new design is cost-effective, provides better horizontal clearance and a better approach for marine traffic, while also optimizing space at the New Hampshire Port and preserving Albacore Park on the Portsmouth, N.H., side of the bridge.
It will feature two 12-foot driving lanes with five-foot shoulders on each side that will allow for bicycle access across the bridge for the first time.The new design also opens the center of the bridge, allowing for a 60-foot height under the main lift span in its normal position. It can be raised to 135-feet at mean high water, which is essentially the clearance that exists today.
Currently, boats can pass under a 34-foot retractable span, and the bridge must be lifted with anything taller. Figg said the new design will mean the bridge has to be lifted less often, leading to fewer traffic holdups.
The navigational width will increase from 175 feet of clearance to 250 feet, which will accommodate a 160-foot-wide ship with tugboats on either side.
“Today to get those ships through, you can’t have the tugs on the side, so this provides a lot more security for those ships coming through that wider opening,” said Jay Rohleder, project designer with Hardesty & Hanover.
Rohleder said they are also considering the possibility of using hydro-turbine power for some functions of the bridge and are in discussions with researchers at the University of New Hampshire and the University of Maine. The four individual towers of the bridge will feature open sheaves, or pulleys, on top, allowing people to watch the bridge as it works. The counterweights will be located inside each tower connected with ropes to a machinery room at the base of each tower and will pull the counterweights up or down as the bridge is lifted and lowered.
It will be the first time this design approach is used in the United States.
The towers will be made of reinforced concrete and will have a glass component along the sides drivers see approaching from the north or south and will provide a view of the counterweights moving up and down for those stopped on the bridge.
LED lighting will be used to light the sheaves and the towers, and possibly other aspects of the bridge as well.
Some in attendance asked about providing pedestrian access on the bridge, but Joyce Taylor with the Maine Department of Transportation said they simply do not have the extra money to make that happen.
Maine DOT is leading this project, but the states of New Hampshire and Maine share responsibility of the bridge and will share in the cost of replacing it.