Footbridge workshop shows three concepts
Dan Bannon of Baker Design Consultants presented footbridge reconstruction concepts to Boothbay Harbor selectmen and the public in a workshop July 12. The workshop is the second of two seeking public input for the design and feature. The first was in November.
Bannon went through much of the same information – the bridge's history, physical features and functionality, and reasons it needs replacement – its age, condition, limited structural capacity, defective swing span, flood risk and code compliance issues.
“We recognize that the bridge has been here for a long time and is an important part of the history of the town,” said Bannon. “We want to make sure any designs we're proposing respect the history of this location.”
All three reconstruction concepts address the issues.
Looking at location and alignment, Bannon said the three designs introduce concepts that received interest during the November workshop. The first concept is a straight-across bridge with a crescent lookout on either side of the footbridge house. The second features an "S" shape, one curve toward the inner harbor on the west side, the other curve toward the outer harbor on the east side, with a circular lookout on either side of the footbridge house. The third concept curves away from the outer harbor with a crescent lookout on either side of the footbridge house.
All three concepts replace the existing 40 or so spans of pilings with about half as many steel pilings anchored in the ledge below the water.
“The steel piles lends itself well to the subsurface conditions that exist there because with timber piles, well, there's nothing really there to drive them into,” said Bannon. “The existing timber piles are just pinned to ledge. That's not a very good condition for resisting uplift force that can happen from icing and high water.”
The walkability will also improve with the concepts as the width of the bridge will increase from the current seven feet to ten feet, “bringing it in line with what bridge design standards would recommend,” said Bannon.
The height of the superstructure, at the top of the deck, will increase by 4.6 feet which puts the bridge at one foot above base flood elevation as per the town's floodplain management ordinance. Bannon said cost estimates range between $2.1 and $2.4 million not counting if Boothbay Harbor decides to make the structure movable for larger marine vessels to access the head of the harbor.
“A movable span will be significantly more expensive in terms of upfront cost and ongoing maintenance cost … With a project of this magnitude, it would probably be in the town's best interest to design in such a way that the structure have the longest lifespan.”
Boothbay Harbor resident Mike McBride said he would like to see option two or three, but stressed that the need for a movable bridge seems unlikely.
“I would think that we could work with the Coast Guard to have that changed on the charts if that's what we wanted to do.”
Chair Wendy Wolf said that was the type of input from the public input the board wants to hear as the process for replacement moves forward.
Some concern was raised over access during construction. Bannon said the bridge would be built during winter with the spans prefabricated offsite and likely brought in by barge. The bridge will likely be out of service for several months during construction as the old bridge is dismantled and the new one is installed.
The public fell to one side or another on some of the concepts. Ken Fitch said he feels strongly the bridge should be straight with timber pilings while Dimsie McBride said the town needs to look to the future and get on board with steel pilings.
Said McBride, “We want this to be around for a long time and you mentioned the difference between wood and steel, that you can make it much more secure with the steel and it has better longevity and less maintenance. Wood has always been used in the past because that's what they had … We really need to look at what technology has for today.”
Norm Pierce favored simplicity.
“Having spent more than 60 years on that waterfront viewing the timber piles – we need to stick to the KISS principle … Straight bridge, simple as possible. We've got to maintain it for 70 years after it's built and it will be built by the lowest bidder more than likely.”