Last December, the consortium of consultants CEMCO/ SRK’N joint venture in Association with Mott McDonald presented a draft report, which suggested that a High Level Foreshore Discharge consisting of a shallow outfall channel and a high crested weir (dam) would be the best option to drain water out of the East Demerara Water Conservancy (EDWC) when the water level reaches a threatening level. GAPE, after being invited to scrutinise the proposals in January, issued a report where it expressed its concern that not much emphasis was placed on considering other alternatives of relieving the EDWC in times of excessive rainfall. The body also believes that “the other alternatives should not be so costly.”
GAPE stated that in the conclusions and recommendation section of the Hydrological and Hydraulic Modelling Studies, the consultants noted that “A much shorter relief channel route is possible between Flagstaff and the Mahaica River.” This section said that “it is possible that drainage in Mahaica could be improved in the lower return period events. The Mahaica option would also need maintenance, but that requirement may not be any greater than the maintenance required for the Hope/Dochfour options. The capital cost of the Flagstaff-Mahaica relief route would be significantly lower than that of the Hope/Dochfour relief.” According to GAPE, these statements suggest that “decisions have been made without paying heed to the engineering inputs to guide those decisions.”
The association, in its report, recommended that the Mahaica River be dredged so as to increase its discharge capacity. The proposal by the consultants had noted that “A bar has formed across the mouth of the Mahaica River and this inhibits full tidal drainage in the system.” Further, GAPE has recommended that the Land of Canaan sluice should be investigated to ensure that its design capacity of 2000 cu/secs is achieved. Reports suggest that currently flows of only 800 cu/secs are being achieved which is significantly less than its design capacity.
Additionally, the Engi-neering Association also recommended that the Sea Defence and Hydraulic Structures should include a small pumping unit to facilitate and aid in out-fall clearing. Provision should also be made for a larger pump which can be used during high flood conditions, the engineering body suggested.
The outfall channel at the sea defence location must be maintained regularly so as to prevent Retardation of Water Flows, GAPE suggested, even as it disapproved of the use and selection of the geotube material.
Meanwhile, the body noted that the construction of the Northern Relief Channel and its associated Dam will create empolder conditions on both the eastern side to Mahaica and western side to the Demerara River. According to GAPE, the new dam constructed should be technically sound and safer than the existing Conservancy Dam, which was built over a century ago. Further the body recommended that the dam along the east and west of the new canal should be planted with selected grass to prevent erosion. The grassed dam should also be maintained at regular intervals each year.
Further, the engineering body argued that projected annual maintenance and operating cost should be compiled, given the fact that siltation is expected to take place at the outlet end.
Speaking generally about the project, GAPE said “it is not clear if any financial analysis was done since the report is silent in this area.” Consequently, “it is not clear if the decisions taken are or will be financially justifiable,” the body stated.
Additionally, considering the magnitude of this project, GAPE suggested that an Environmental Impact Assessment be done as well as an Environmental Manage-ment Plan prepared.
The proposed relief channel, which was initially priced at $3 billion, is intended to drain the EDWC into the Atlantic Ocean, thereby serving as a more efficient and less destructive means of releasing water from the conservancy. At the moment, when the EDWC is at a dangerous level, water from the conservancy is drained through the Maduni and Lama sluices and this has caused catastrophic flooding in the Mahaica and Mahaicony areas.
