Potworks dam dry – but still good option for water storage

Sean Peters, former GIS engineer at APUA, stands beside the water gauge at the Potworks reservoir. Photo taken in spring 2020. (Photo courtesy APUA)
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By Elesha George

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A total of 20.61 inches of rain was recorded in Antigua between January 2020 and August 2020, according to Director of the Antigua and Barbuda Meteorological Service, Dale Destin.

Still, the reservoir at Potworks remains scorched, with only stunted green vegetation covering the land.

The 500-acre earth-filled dam has the capacity to hold one billion gallons of water, but years of drought have left it dry and spillway failures have not been able to harness what little rain may fall.

“Rain dropping directly on Potworks is not going to fill it,” remarked Ian Lewis, water manager at the Antigua Public Utilities Authority (APUA).

He told Observer that water gets into the reservoir via runoff produced by gut rain in the Buckley, Liberta and All Saints areas but in recent times there has not been enough saturated rainfall to cause gut rain.

In fact, APUA has not been able to extract water from Potworks dam since March.

Between January and March, the reservoir stored a mere total of 58.5 million gallons of water – that means that the dam was able to store only six percent of its full capacity.

Lewis explained that the dam stored 22.8 million gallons in January, 21.8 million in February and its lowest amount – 13.9 million gallons – in March.

The biggest challenge to keep water inside Potworks is caused by leaks in the 12-foot tall Willoughby Bay spillway, which is one of two passages for surface water to enter into the dam.

John Bradshaw, a private civil engineer and former water manager at APUA, said his team fixed the spillway twice before he left the company in 2008.

“That spillway has been leaking for many, many years, so although Potworks dam theoretically can hold a billion gallons of water, it would not hold so much because half of it will leak out,” he explained.

If the leakage is fixed, Bradshaw believes that the utility company can get up to five months of additional water from the dam. He however believes that the spillway needs to be completely restructured, noting that the benefits would outweigh the cost of fixing the passage.

Bradshaw said APUA was attempting to solicit technical assistance from the Chinese government to fix the spillway before he left the company, though now he can’t be sure what happened to the initiative.

“We have repaired it twice in my time. We filled the void with concrete and we tried to reinforce them,” he said, but after a year or so the spillway began to leak once more.

According to Bradshaw, a very delicate balance has to be struck to maintain the integrity of the reservoir.

He told Observer that there is not much that can be done since digging past six feet into the ground of the dam will contaminate the water supply, making it salty which would in turn force the company to take up additional costs to desalinate the water.

He added that any cleaning of the dam would have to be monitored to prevent breaking the layer that would expose the sea water and limestone underneath.

To date, the current water manager said that APUA still operates with the broken spillway and, although geo-technical engineers have studied the leak, there has been no permanent fix to the problem to date.

After the dam’s water source was depleted, the APUA turned its attention to the Bendals Valley, where they were able to supply consumers with 300,000 gallons of water daily. That source is now also dried up and the water company has been relying strictly on desalination and ground water.

The reverse osmosis plants that provide the desalination water however require daily maintenance and have to be taken off the grid regularly for cleaning.

While Lewis said there is no silt in the dam, it is still very shallow and it currently harbours organic plants that APUA will remove in order to improve the chances of retaining water when it rains.

While APUA tries to restore a decades-old problem, trucks are hauling millions of gallons of water from the company’s main trucking point at Crabbs Peninsula to help meet the demands of residential and commercial properties who have been reduced to operating off a water scheduling programme.

Lewis shared that APUA has supplied a total of 114,530,091 million gallons of water to water trucks from January to August this year. The highest supply was recorded in March at 1.6 million and in June at 1.9 million gallons.

Water distribution fees can cost customers several hundreds of dollars a journey, based on the amount of water requested and the customer’s location. Both men however agreed that the use of the reservoir is still a viable option in 2020 as it would significantly reduce the cost of water production.

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