Dear Editor,
I refer to the government’s proposal to build a two-lane each way bridge across the Demerara River using reinforced concrete.
First of all this structure cannot be built in reinforced concrete on account of the spans required. The central span which has to be 50 metres above high water and the span 100 metres to enable ships to pass under would have to be a steel truss arch design or prestress beams. In addition the soil-bearing structure would not be able to support the loadings emanating from the loadings on the bridge.
On the coastland you have to deal with soft clays and mud. There is a layer of stronger clay known as coropina clay below the soft material, but its strength would not be suitable to support the bridge loadings. These types of bridges are normally supported on rock foundation.
The estimated cost to build the bridge in the region of US$250-300M proposed by Mr Adams, GM of the Harbour Bridge is also ridiculously low for the 2.25 km bridge.
Let’s assume a developer is interested in building the bridge on a BOT system for an assumed US300M. Using a figure of 2000 cars a day crossing the bridge and paying a one way toll to cross the river it will cost the developer over a period of 4 years $330M to build the bridge using a figure of 7% interest rate.
Using a capital recovery factor he will need an annual cost of revenue of US$28.32 a year over a period of 25 years. The total annual cost including operation and maintenance works out to be US$31.32M per year.
From the calculations above vehicles crossing the bridge one way would have to pay a cost of US$43 per day, ie G$8600.00 a day ‒ a ridiculous cost indeed for the poor travelling public in Guyana to bear.
People will resort to using small boats to cross the river. Guyana is a poor country with a small population where 90% of the people live on the low-lying coastlands, and it would have been far cheaper for consumers and cars to traverse the river using the ferries as was the case during colonial times.
I feel Mr Adams, manager of the Demerara Harbour Bridge should have done his homework calculating costs, etc, before venturing to ask developers to build the bridge on a BOT system.
Yours faithfully,
M Alli
