Balancing Portsmouth bridge proves a problem
PORTSMOUTH — The weight difference between the new Memorial Bridge's lift span and counterweights is greater than the Department of Transportation anticipated, according to Keith Cota, project manager for the bridge.
"We are looking at a means of bringing it down to a level we can find acceptable," Cota said Wednesday, noting that Archer Western Contractors has some work to do.
To function most efficiently, the bridge counterweights and lift span have to be nearly perfectly balanced. Right now, the balance is within 10 percent, Cota said. The goal is around four percent, he said.Carol Morris, spokesman for Archer Western Contractors, said Tuesday that the lift span was intentionally made heavier because it is easier to remove weight than to add weight to the span's concrete deck. There is no problem with the concrete, she said.
But Cota said the concern with grinding down concrete is whether the steel rebar reinforcing it is deep enough and the drainage gutters low enough to accommodate the removal. The concern with adding weight to the counterweights is that it puts additional pressure on the cable systems and motors that run the bridge up and down, he said.
As of Wednesday afternoon, Archer Western was still working on the problem.
"We are still waiting for them to come forward with a recommended solution we can accept, but we don't see that as being an element that is going to delay them any further," Cota said.
Morris insisted Wednesday the difference in weight is not a significant problem for the contractor.
"We anticipated a certain level of difference, and they are in the process of fixing it and it is part of the standard process," Morris said.
She expects recommendations to be passed on to the Department of Transportation by Friday, along with a full checklist of the remaining items that need to be done before the bridge can open in mid- to late July.
"I can tell you, it is not something that is creating a big roadblock for Archer Western," Morris said Wednesday. "It is one of many unexpected issues we have had to overcome with this bridge."