Dear Editor,

I refer to the Minister of Agriculture’s request for comments on the Consultant’s Design Report for the Hope Relief Canal Northern Relief (SN, December 20, 2009) as well as comments on the Ministry of Agriculture web site on the subject.

The consultants presented two proposals, one estimated to cost $3.2B. The other proposal that was recommended and accepted was for a 3-door sluice (internal width between doors 16.2 m) at the EDWC end and an 8-door high sill radial gate sluice (internal width between doors 44.2 m) at the sea defence end with a 1 km outfall channel and a bed width of 44.5 m. No approximate cost was provided for this option.

The bed width of the main drainage canal was given as 30 metres. First of all, I cannot see how the bed width of the canal can fit in with the internal width of the sluices which are much larger.

When you take into account the cofferdam required for the 8-door sluice; sea defence protection concrete walls of at least 100 ft, both sides downstream of the outlet sluice; the length of the drainage channel and embankment over 10 kms long; road diversion with a high level prestress bridge at the main roadway; access road for construction; access bridges across the canal, etc, the cost appears to be in excess of $4B.

In addition, the main consultant, Mott Macdonald, recommended that the Cunha and Kofi sluices on the East Bank, long discarded, be put back into operation before construction of the Hope Relief. This will further increase the cost. No mention was made of this in the consultant’s report to the Minister.

Maintenance of the 1 km outfall will further add to the cost. I do not know how the proposed geo-tubes will work. They have never been used in Guyana before. It should be noted that a similar type of construction for the Black Bush Scheme indicates the outfall at Lesbeholden and Mibicuri became silted up shortly after construction.

It appears that the intent is to use the long drainage canal as storage and then release through the 8-door sluice when convenient.

The EDWC was formed to control the water emanating from the Maduni and Lama Creeks. Over the years the outfall to the Mahaica River became silted up similar to the situation at the Abary River for the MMA where the 7-door sluice was also not releasing compensation flows to keep the river channel alive. This is one of the reasons why when you release through the Maduni and Lama Sluices the poor folks along the river are flooded out. In addition, the mouth of the Mahaica River has a sand bar and is silted up as far back upstream as Belmonte and perhaps beyond. Hydographic surveys taken in the ’70s indicate this problem.

Therefore, it makes economic sense to locate the drainage channel at Flagstaff going east. The water level in the EDWC is also the highest at this location. It will also be much shorter in length than the Hope Canal, perhaps ⅔ less in distance. All you need is a sluice at the Mahaica end and to purchase a suction dredge to keep the mouth clear on an annual basis. If there is any flooding it will be minimal, and the people would have to learn to live with it since it is a Mahaica River problem.

The suction dredge can also be used to clear the mouths of the other creeks on an annual basis to improve drainage and can be used to clear the Abary River that has become silted due to reasons stated above. This will alleviate the flooding in the Mahaicony area and also prepare the way to continue with the MMA scheme to the EDWC.

Of course, this is just a suggestion. It is up to the government how they want to proceed.

Yours faithfully,
Malcolm Alli