Raw Water Systems
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Connect Saint Helena Ltd has a programme of works to ensure the security of the island’s precious water supply. There are several aspects to this programme which include the following:
Reservoirs A reservoir is basically a large dugout or hole in the ground which is lined with a synthetic or man made lining. The island’s only earth dam, namely the Harpers 2 Dam is situated near Francis Plain with an embankment and a concrete lined spillway, which was built directly into a natural stream. Connect Saint Helena Ltd currently have 12 raw water reservoirs, 4 of which are used to supply water for agricultural consumers.
You might wonder what is the capacity of each of these reservoirs? See below details. Red Hill raw water system
Scotts Mill reservoir - 6,690m3
Hutts Gate raw water system
Small Irrigation reservoir - 487m3
Levelwood raw water system
Levelwood reservoir - 3,762m3
Raw water abstraction systems
Raw water abstraction systems are placed at locations where water naturally flows and are built out of stone, concrete and other natural materials. A well designed abstraction system captures as much water as possible and funnels it into pipes and minimises loss. Once collected in this way, the water is gravitated through a network of pipes to the reservoirs. Over the years we have reviewed and redesigned our raw water abstraction systems so that they are now able to collect a higher volume of water. Silt traps have also been added to aid maintenance and reduce the volume of suspended solids entering the system.
Boreholes
Beneath the surface of the ground, there is a network of underground streams or aquifers that mostly contain fresh water. A borehole is where we drill into this network or an aquifer and pump the water to the surface. We currently pump water from and maintain a number of boreholes that feed the Red Hill, Hutts Gate and Levelwood water systems as and when needed. Raw water pipelines
These pipelines carry water from the raw water abstraction systems to the reservoirs. When Connect was formed in 2013 we inherited already aging pipe systems. Since then we have come a long way in renovating, modifying and upgrading these pipe systems so that they can carry a higher volume of water and have a longer lifespan. Raw water collection systems are constantly being improved to make the most of the rainfall we get. Upgrade of raw water pipeline from Leggs Gut to Hutts Gate
The original pipeline from Lower Leggs was installed back in the 1980s to transfer raw water from the Leggs Gut water catchment to the Hutts Gate reservoir. However, when the water catchment at Leggs Gut was upgraded back in 2015, while this did allow more water to be captured, the undersized pipe was not able to cope with the extra flow, thus putting a strain on the pipeline. The existing pipe has airlock issues and has deteriorated due to holes drilled along the pipe to try to resolve this. Approval was given to replace this pipeline and work started in early March. This new water main will include the incorporation of automatic air valves and wash-out valves. Automatic air valves prevent internal pressure build-up in the pipeline which not only minimises damage to the mains, but also reduces operating costs because someone will not need to physically go and operate these valves. This pipeline will also allow us to transfer higher quantities of water with minimal loss.
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