Minister of Works Arden McLean thinks George Town needs a central sewerage system.
‘It will be a very, very expensive undertaking, albeit one that is needed,’ Mr. McLean told the Finance Committee recently.
Such a sewerage system will not be built any time soon, however.
‘In the short to medium term, we can suffice with the system we currently have,’ he said. ‘But I think we need to look in the next 10 to 15 years to having a central sewerage system in George Town.’
Water Authority Director Gelia Frederick-van Genderen could not say how much constructing a sewerage system in George Town would cost, even if done now.
‘In the absence of preliminary investigations, a preliminary design, and/or even an estimate of the initial area the collection system is to cover, it is extremely difficult to give a reasonable estimate of the construction cost,’ she said. ‘In any event sewerage systems are much more expensive to construct than water distribution systems due to the increased depth and larger pipes, lift/pump stations, manholes etcetera, and the construction costs for a collection system for downtown George Town alone are likely to be in excess of CI$15 million.’
Grand Cayman only has a sewerage system for the West Bay Beach area. That system, which was built in the late 1980s out of clay pipe, has developed many cracks.
Mrs. Frederick-van Genderen said there is no leakage out of the pipes, but that there is infiltration of saline groundwater into the sewers. The infiltration causes the sewage treatment plant to have to process more sewage on a daily basis than it really needs to.
‘We have funds approved for the 07/08 fiscal year to address the problem of saline groundwater infiltrating the sewerage system using slip-lining technology,’ she said.
With the slip lining process, a smaller diameter pipe liner is slid inside the existing pipe. The method requires minimal excavation.
Any future sewerage system on Grand Cayman would use materials other than clay, most likely PVC or high-density polyethylene, Mrs. Frederick-van Genderen said.
Building a sewerage system here has difficulties because of Cayman’s water table.
‘We have a high water table,’ Mrs. Frederick-van Genderen said. ‘This is a challenge, especially if open trenches are used. It is difficult to pump the trench dry in order to properly bed and lay pipes.’
Parts of the West Bay Beach Sewerage System had to be laid with SCUBA divers because the contractor could not pump out the groundwater from the trenches, Mrs. Frederick-van Genderen said.
The elevation in George Town is higher compared to the West Bay Beach area, but not high enough to eliminate the problem.
‘The majority of the sewerage system [in George Town] will have to be installed below groundwater table, therefore the construction of a sewerage system would pose similar challenges as for the West Bay Beach Sewerage System,’ Mrs. Frederick-van Genderen said, adding that there would also be physical challenges such as narrower roads, more traffic, more underground utilities, and the works affecting more businesses in George Town.
One thing that is already in place for the eventuality of a sewerage system in George Town is the sewage treatment plant.
‘Capacity of this phase [of the sewage treatment plant] is 2.5 million gallons per day,’ said Mrs. Frederick-van Genderen. ‘We currently receive about 1.5-1.8 MGD. The plant is also expandable in phases to 10 MGD when the need arises.’
Mr. McLean
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