DHB to effect bridge repairs from today

Sep 21, 2013 News

Management of the Demerara Harbour Bridge (DHB) will be attempting a similar pivot changing exercise today that caused the structure to collapse in July 2012.

Arial view of Demerara Harbour Bridge

DHB’s General Manager, Rawlston Adams, at a press conference disclosed that the operation will commence today and conclude tomorrow. Though, the bridge would be open to traffic, vehicles weighing more than 22 tons will be restricted.
To ensure this project is executed properly by staff of the DHB, management is utilizing knowledge from the previous pivot changing exercise at spans 60 and 61 when the jaws on one of the uni-floats that were assembled for the temporary pontoons broke and the pontoons sank.
According to Adams, this exercise seeks to replace the pivots at spans one and two at the eastern end of the structure. He said the pivot change is very critical since the pair was never changed since the bridge was constructed 35 years ago.
The cost of the operation is way in excess of $5M with preparatory works consuming the bulk of the money. Adams said that the pivot is a very small component in the whole scheme of things but is very important.
He disclosed that management was fortunate to find an original pivot of the bridge. This was used as a template by Courtney Benn Construction Services Limited to fashion the six pivots needed on the bridge.
Adams said that preparatory works for this project began about four months ago with dredging of the area to allow for the pontoons to be inserted. This aspect cost in excess of “the hundreds of thousands of dollars” invested in the fabrication of the pivots, he added.
In addition, the two new pontoons that supported the retractor span were relocated to spans one and two to facilitate the pivot change while the large pontoons were removed.
“We are using some single flotation units. The last time we used some small units that the bridge came with, the jaw for that broke. There is no possibility of that happening now. We have discarded them…we eliminated that risk.
“These single unit pontoons have chambers that in case one chamber develops a problem it wouldn’t cause a problem with the entire pontoons” he said.
Adams said DHB has signed a contract with Courtney Benn Contracting Services Limited to erect two pontoons for replacement purposes.
The General Manager related that whilst the operation focuses on the changing of the pivot, it allows employees of DHB that have the expertise to carry out other rehabilitative works. He said during the previous exercise personnel encountered corrosion and were given the opportunity to fix that section of the structure.
According to Adams, this operation is being funded from DHB revenue. With the bridge closing operations to only special crossings it could lose about $60,000 over the period. However, light traffic and retraction for marine traffic would be as per normal and some commuters may not even be aware of what is happening below the bridge, he added.