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Gb Water Supplier Sets Out Post-Dorian Strategy

Grand Bahama’s water supplier is seeking out new fresh reserves and aiming to revive an old wellfield after virtually all its existing sources were compromised by Hurricane Dorian’s storm surge.

The Grand Bahama Utility Company Limited (GBUC), in a statement, said storm-damaged pumping stations were brought back on line within five to seven days of Dorian’s passage to restore the island’s running water “distribution”.

However, the category five storm compromised the island’s‘supply of fresh salt-free water in Wellfields one, three and six. Some 220 wells in total were impacted, accounting for 35 percent, five percent and 60 percent (respectively) of water being supplied throughout the island.

Wellfields one and three were flooded with four feet of sea water, while Wellfield six was flooded with 21 feet of sea water for a period of 36 hours during and after the storm. The flooding destroyed the entire vertical infrastructure, including utility poles, wires, electrical components, control and motoring systems.

Prior to Hurricane Dorian, tap water provided to the community of Grand Bahama was below 600 ppm (salt particle content per million parts of water). This bettered by a large margin the 1,000 ppm World Health Organisation (WHO) standard for consumption.

Remington Wilchcombe, Grand Bahama Utility Company’s utility engineering manager, said: “Once the flood water had subsided at Wellfields one and six, our team immediately enacted an action plan to restore water supply. An assessment was conducted to determine the impact to the systems.

“One of the wells tested at 25,000 ppm, which is close to the salinity of sea water at 35,000 ppm. Results a few days later revealed that the average reading per well was 8,000 ppm in both Wellfields one and three, and 9,000 ppm in Wellfield six.”

Mechanics were recruited to bring back-up systems into service. Once back-up systems were restored, the Utility Company was able to begin rationing fresh water reserves into the system five days after Dorian.

Simultaneously, the Grand Bahama Utility Company began working with Sanitation Services to conduct clean-up efforts within the wellfields. Grand Bahama Power Company conducted repairs to repair the power systems at wellfields one and six, while the Grand Bahama Shipyard, Bahamas Industrial Technologies, Martin Marietta Aggregates – Bahama Rock and Freeport Container Port all provided technical services, manpower and equipment to return the plant to service.

By September 30, the average salinity reading per well had improved with wellfield one at 4,000 ppm; wellfield three reduced to 2,000 ppm; and wellfield six still showing the highest salinity content of 6,000 ppm.

Mr Wilchcombe said: “In an effort to ensure the speediest process for restoring potable water, we enlisted international services to perform a first phase hydrological study to provide further testing and recommendations relating to the movement, and physical and chemical composition, of the water.”

Water & Earth Sciences conducted a Resistivity Test, which assesses the level of salt water existing in the water lens. The results confirmed that 99 percent of the wellfields were inundated with sea water, which compromised the water quality. Further, it was determined that all of the wellfields had varying layers of salt water, brackish water and fresh water.

A second assessment was conducted by the United Nations Educational, Scientific and Cultural Organisation (UNESCO), which included the areas of Freeport city and East End. The results confirmed findings provided by Water & Earth Sciences that the wellfields had significant sea water incursion.

A third assessment was conducted by Dr Yakov Livshitz from the Hydrological Service of Israel, which again included the areas of Freeport City and East End. His team visited the island to gather samples for testing to determine the porous nature of the limestone, and a detailed assessment to locate fresh water lenses in the current wellfields was carried out.

Flow rates were tested to determine the time frame and restoration rate. Finally, a survey was conducted to find additional fresh water lenses outside of the wellfields to extract or supply fresh water. As a result, fresh water was found in some high elevated areas. However, the capacity is not known at this time.

Geron Turnquest, the Grand Bahama Utility Company’s general manager, said: “A second phase hydrological study must be carried out to validate and confirm the capacity of the fresh water lenses that were found for the development of new wellfield locations.

“The most feasible approach, currently underway, is to bypass various higher salt content wells in wellfield six with additional fresh water reserves further east, and to revive and develop wellfield four, which has been out of service for a number of years.”

The Grand Bahama Utility Company has also discussed the possibility of investing in a reverse osmosis (RO) System. Mr Turnquest said: “We have considered the possibility of introducing a large-scale reverse osmosis system. But we are advised that this presents challenges.

“Despite it being an expensive investment that will impact the cost of water to the consumer, it will also take a minimum of three to four months to develop. By this time we aim to have resolved this salinity issue with new measures in place.

“A reverse osmosis system on this scale would only be needed if the possibility of having no fresh water exists. That said, smaller backup reverse osmosis systems in small modular units are very likely to be part of our plan to provide drinking water in the event of a future hurricane.”

Assessments to date reveal a continuing decline in salinity levels. Wellfield one is now 2,400 ppm, Wellfield three is now ‘potable’ at 500 ppm, and wellfield six is 3,600 ppm. Ian Rolle, the Grand Bahama Port Authority’s president, said: “The GBUC is committed to resolving the issue of salinity levels as a result of the tidal surge.

“The actual water pressure and the volume pumped per day is back up to pre-storm levels, which is reassuring. Key infrastructure works are in progress, and we continue to confer with the experts to bring about the best and speediest return to our pre-storm highest quality fresh water”.

Residents have been advised through public notices that the water can be used for sanitary purposes only and not for consumption. GBPA chairman, Sarah St George, added: “We wish to emphasise that the water is clean and bacteria free. While we work to restore potable water, we have established a partnership between GBPA, GBUC, NEMA and several non-governmental organisations to provide free drinking water to local communities at water distribution sites island-wide.

“We are grateful to our NGO partners, Isra-Aid, Samaritan’s Purse, Mercy Corps, Siemens, Resolve Marine, Water Mission, International Medical Corp, Operators without Borders and ADRA. As salinity levels decrease naturally through rainfall and new wells come on line, we look forward to restoring a potable water supply through the island of Grand Bahama in the near future. We thank everyone in the community for their patience and understanding. We are on the right path to bringing our water back to its erstwhile pristineness.”

Comments

BMW 2 years ago

Now they need to get the airport up and running.

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