Sunday, February 8, 2009

The proposed Hope Canal is not the best option to drain the conservancy.

Stabroek News letter, 13 January 2009. The proposed Hope Canal is not the best option to drain the conservancy.

Dear Editor,
I refer to the President’s recent announcement to construct the Hope Canal to prevent water being released from the EDWC to the Mahaica Creek that causes flooding to the residents.

Extensive studies in the ’60s were carried out by the Hydraulics Division to determine the best location to drain the EDWC and it was determined that the Land of Canaan Sluice (LOC) was the best location and option since an Atlantic relief would likely be subject to some tidal lock which be undesirable for a spillway operation, ie the discharge sluice at the sea wall end could only work on a tidal basis some 6 hours a day discharging a pittance daily.

The LOC, built in the ’60s, is a 5-door high sill sluice, and can discharge 2000 cusecs working on a 24-hour basis independent of the tide, and was built specially to drain the EDWC. Since 1970 the conservancy has not been maintained, and today has reached a critical stage of siltation and vegetation inhibiting its storage capacity.

The proposed works related to the Hope Canal would be extensive. The canal has to be a high level canal with some 80 ft bed width, some 10 miles long - not 6 miles according to the President – and would require the construction of 2 large sluices at the EDWC and through the existing sea defences, several bridges over the canal, a bridge at the roadway, access roads, etc. The canal and outlet has to be designed to discharge at least 2000 cusecs.

I doubt very much whether the inlet sluice at the conservancy can provide 2000 cusecs from the EDWC at the moment, due to its silted state. Extensive modelling and dredging works have to be carried out to obtain the 2000 cusecs required from the EDWC.

The cost in my opinion would far exceed the $3B quoted by the President. I doubt whether Guyana has the local engineering expertise to design and construct such a project.

I would suggest the government as a cheaper alternative improve the capacity of the LOC which is only operating around 40% efficiency, by redesigning and re-constructing the inlet channel and canal inlet and also awaiting the studies and modelling works to be undertaken shortly for the EDWC (reference an article in GC, 11.1.09) and then and carry out the works recommended by the consultants if feasible.
The release of water from the EDWC via the Maduni and Lama sluices cannot cause the flooding in the Mahaicony/Abary areas, only in the Mahaica area.

I started the MMA scheme and designed and supervised the construction of the 7-door Abary Control Sluice. Information was passed on to the authority that the sluice must release a certain amount of water daily so as to keep the Abary River alive. This was how the scheme was designed. Water to this date some 30 years later still has not been released, resulting in the Abary becoming so silted for some 45 miles from the conservancy to its mouth, that it would be impossible to dredge it to bring it back alive. The sluice also appears to be non functional.

Over the last few years the writer wrote several letters about this problem only to be responded to by the authority that the river was alive and free flowing with water.

The bottom line is the Abary River cannot carry its share of the drainage load and hence the water has nowhere to go but to the Mahaicony, resulting in constant flooding whenever there is heavy rainfall.
Continuation of the scheme as proposed by the President would not prevent this from happening, and could make matters worse by silting the Mahaicony as well if the second stage is similarly maintained as the first.
Yours faithfully,
Malcolm Alli
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