Dear Editor,
It was reported in SN on July 12 that the Minister of Housing and Water and Officials from the National Drainage and Irrigation Authority (NDIA) visited a site on July 9 where a bridge over a drainage channel and linking Diamond to Mocha on the East Bank of Demerara is under construction. The photo accompanying the SN article together with photos in other news media showed two steel sheeting paal-offs on the right and left banks of the channel where the bridge crosses and a number of driven and partially driven piles for the bridge’s abutments. It is troubling as to the purpose for the Government officials visit to this bridge site whose construction is in its very preliminary stage when its progress could have been easily obtained from the supervising engineer’s construction progress reports unless there were problems which necessitated the client’s visit for a determination and/or resolution. The report stated that concrete piles were being driven for the foundation of the bridge’s piers. However, the photos show a mixture of wooden and concrete piles. It was not evident as to whether all the piles were wooden with some of them capped with concrete or a mixture of both.
The steel sheet piling (SSP) driven on the banks of the channel are of insufficient depth to restrain the lateral earth pressures imposed upon them. Hence their displacement towards the center of the channel. The cross bracing done would have helped to restrain any movement of the SSP but they are too flimsy to restrain the forces imposed upon them and if no action is taken their gradual movements could eventually lead to a collapse. The support for this bridge is apparently designed to be carried by friction piles driven into its abutments at an adequate depth into the underlying soil. A lot of bridges worldwide have collapsed over the years because of the loss of support from friction piles because of the loss of material around them due to erosion by water and other means. Hence the visit to this bridge site by the Government officials should have ensured that proper engineering practices are in place during its construction and shoddy methods to build it is not being used to build it as is evident by the photos.
Sincerely,
Charles Sohan
