St Helena : St Helena: PROGRESS ON BASIL READ AND SHG’S WATER DRILLING PROGRAMMES
Submitted by Saint Helena Herald (Public Relations Information Office) 07.07.2012 (Article Archived on 21.07.2012)
Both Basil Read and SHG have been involved in water drilling programmes recently. The needs of each are very different, with Basil Read looking at relatively short term availability of water for airport construction purposes, while SHG is looking at the long term needs of the Island.
WATER DRILLING ON ST HELENA
PROGRESS ON BASIL READ AND SHG’S WATER DRILLING PROGRAMMES
Both Basil Read and SHG have been involved in water drilling programmes recently. The needs of each are very different, with Basil Read looking at relatively short term availability of water for airport construction purposes, while SHG is looking at the long term needs of the Island.
Basil Read
During the peak of construction, approximately 3,000,000 litres of water a day will be needed for the airport project. This water will be made up of fresh water collected from boreholes. Basil Read has recently begun investigations and drilling for water to meet this requirement.
A South African Company, 121 Drilling, has been contracted by Basil Read to carry out their water drilling programme.
The team arrived to the Island on 1st June and began drilling in Rupert’s Valley soon after. Moving on from Rupert’s, two holes were drilled in Fisher’s Valley and the first of five holes was drilled on Prosperous Bay Plain. After five holes have been drilled at Prosperous, the team will be moved to Dry Gut to drill a further five. This work is expected to start in August. Work will reach its peak in March 2013, when the full quantity of water per day will be required.
121 Drilling has been contracted to drill 20 holes in total but this will depend on the quantity of water found. If more holes are needed then the company will drill them.
If the required quantities of water cannot be obtained, Basil Read will need to use desalinated water, which will be a relatively new technology to the Island. As with any new technology, implementation will require investment in infrastructure and personnel, so Basil Read is taking the opportunity at this early stage in the project to explore other sources of water before taking a decision on whether desalination will be required.
Speaking with Deon De Jager, Island Director he said:
“We are on programme to achieve the quantities required at the various stages of construction. The quantities of “fresh” water found will obviously determine the quantity of desalination required – but it is all built into the overall timeframe.
“So far we have found water in most of the boreholes but we have not done any yield testing on the holes as yet. If we do not find the required quantity of water needed for the project, the contract makes provision to use sea water in the inner core of the fill – and the balance will come from desalination.”
Basil Read has a Contractors Environmental Management Plan (CEMP) which addresses the environmental considerations around groundwater extraction, for example, ensuring that found water sources are not depleted. Basil Read is closely following the mitigation measures and controls set out in the CEMP.
Basil Read has been working closely with SHG on their water programme and utilising the technical advice of Subadra, a Water Engineering Company contracted by SHG.
Once the airport project is completed and the boreholes are no longer needed, Basil Read will negotiate with and come to an agreement with SHG to take them over. The Island will therefore benefit in the long-term.
SHG
St Helena Government has also begun drilling for water as part of its DfID funded Water Infrastructure Programme.
Martin Squibbs, Water and Drainage Manager reported:
“A water consultant from Fairhurst was appointed in September 2010 and one of his first tasks was to carry out a Water Resources Study and produce a Water Resources Plan covering the next twenty years. The study looked at predicted changes in water demand on Saint Helena [with and without an airport] and how this demand could be met. The study concluded that there are sufficient existing water sources to meet demand for the next ten years or so, but there is a need to identify new sources to enhance the current sources supplying the Redhill and Hutts Gate Water Treatment Works.”
Traditionally on St Helena, fresh water has been collected from springs and streams and then stored in reservoirs. More recently, boreholes have been drilled and groundwater pumped to the surface. However, because the boreholes have only extended to a depth of about 30 metres, the water can be contaminated by cattle and spillages on the surface.
The current investigation is to look for water at a greater depth and to effectively seal this water to prevent surface contamination.
SHG has a trailer mounted drilling rig that is used to carry out this specialist work. Subadra were contracted by SHG to carry out the drilling and pump testing, supported by staff from SHG’s Water and Transport Divisions.
The plan was to drill six boreholes to a maximum depth of 100 metres and enough materials were brought to Island to achieve this.
Angus Gale of Subadra, arrived on the 1st of June and spent a week carrying out modifications to the drilling rig to achieve the task. Drilling started on Saturday 9th June, soon after Andrew Cassidy, Subadra’s driller, stepped on land at the wharf.
The first borehole was drilled in the area of Ladies Bath, next to Plantation House, but progress was halted by instability within the borehole. The second borehole was drilled in Harpers Valley and reached 92.5 metres, but insufficient water was found to meet requirements. The third borehole was drilled at the existing wellfield site at Willowbank, which supplies Hutts Gate Water Treatment Works, and reached 70 metres. While the bottom 20 metres was in unsuitable ground and has been sealed with a bentonite/cement grout, this is a very promising well which will be further tested for quality and yield.
During this time, SHG and Subadra were working closely with Basil Read and it was agreed by both that to get the best out of the equipment, Subadra would drill in the Shark’s Valley area, which is inaccessible to the larger lorry mounted rig used by Basil Read, whilst Basil Read will use the larger rig to complete at least one borehole in the Plantation area for SHG.
Martin concluded:
“This is an excellent example of the cooperation that is necessary at a remote location like Saint Helena.”
SHG
4th July 2012
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