The repair work at the EC$600 million port being built in Kingstown is “an easy fix” but will be time-consuming, says Lenski Douglas, an engineer who is the project’s coordinator.
He, however, warned that the problem, where 30% of the piles along the quay walls have declutched — resulting in the loss of reclamation material and large pools of sea water inside the quay wall — will appear to get worse even as it is being fixed.
The port is being built on land reclaimed by depositing sand into the sea in Kingstown, then driving piles into the seabed to contain the sand before compacting it.
However, in February, photos began emerging on social media showing large pools inside the concrete quay wall.
Prime Minister Ralph Gonsalves then announced that some of the sheet piles had declutched, resulting in the loss of reclamation material.
Speaking on WE FM recently, Douglas explained how the port was being constructed.
“The wall was being constructed of king piles, which are circular, and sheet piles, which have a ‘Z’ profile. Those serve primarily as infill pieces.”
He explained that because the reclamation was done before the construction of the quay wall, there was excess material on the outside, where the vessels are to berth.
“So, the contractor then, naturally, had to remove the excess material on the outside in order to create enough depth so that the vessels can come alongside. And he had to remove material down to 12 meters below water level,” Douglas said.
He said that the water outside the quay wall must have a clearance of 12.5 metres (41 feet) to accommodate larger vessels without a threat of them running aground.
“So, during that exercise, we realised that material was being lost from on the inside, from on the land side. Obviously, something went wrong,” Douglas said.
“… we realised that what occurred is that between each king pile, there’s a sheet pile and they typically would what you call clutch together. And what has happened is that those clutches, for one reason or the other, … have separated… 30% of the clutches … have separated. The material, therefore, is being lost through those separations…”
‘A standard fix’
Douglas said that the loss of reclamation material was not linked to the structural integrity of the port.
He said that the contractor — Aecon, a Canadian firm — is obligated to deliver to the government of St. Vincent and the Grenadines a port facility that meets the specifications in the contract.
He said the fix has three components.
“And it’s a standard fix. … As a matter of fact, it’s an easy fix in terms of what has to be done. Doing it can be time-consuming and also challenging … You have to first now close those gaps that the material is escaping from.”
He said this will be done by welding steel plates onto each king pile.
“So spanning across where the sheet pile isn’t filled, you weld the plates from one king pile to the other.”
Douglas said the welding was being done by certified divers who have “vast experience, pretty much dealing with the same issue and in a much more rougher environment”.
He said the divers and their company are from the United Kingdom.
“They are executing underwater works just as if you’re on land with these specialised tools,” he said, adding that they will clean the surfaces, put the plates in position, then weld them.
“They would go and do their inspection, measurement, testing. Everything is being done underwater but it’s going to take time,” he said, adding that the divers will be operating up to 20 metres (60 feet underwater.”
The engineer said each diver would be permitted to work in the 20 meters of water for just over one hour at a time.
“So there’s a constant cycle in the interest of the safety of the divers, because it has to be done safely also,” Douglas said.
“So as much as the fix is a standard, or, as mentioned in the manuals, an easy fix — it’s standard — getting it done involves actual humans who have to be working within their own safety parameters.”
Douglas said that everything that is done on site is being recorded in the interest of safety, so it can be monitored above the surface.
He said that at the last count, the welding “was about 16% complete in that section where you have the large depression that … developed.”
Space to be filled with special concrete
Welding the plates will create a cavity between the sheet pile and the welded plate. This space would then be filled with concrete to prevent further loss of reclamation material.
The engineer said that a tube would be inserted into the space created by welding the panel onto the sheet piles.
“And you have to pour that concrete so that the tube remains inserted in the concrete itself. So, as the concrete flows out of the tube, it displaces all of the water above.”
He explained that it is special concrete that would prevent the cement from washing out into the water.
“… you’re going to be using a lot of what is called plasticisers. So, it’s not your normal three-to-one mix that you guys would use a shovel and so on,” Douglas said.
“… you have to reduce the water content of that cement, because you’re going to be placing it in water, you’re going to use a lot of additives to ensure that the drying time is reduced and that the strengths can be achieved after you do your 28-day test — seven-day, 14-day, 28-day tests.”
Douglas said each of these steps will be quality-controlled and done by divers.
“So, you’ll be doing that along that entire front wall in the area where there is observed declutching.”
Improvement to become noticeable in June
He said the public would not see an improvement to the ponding until around June.
“That is because you have to complete the welding, you have to complete the application of the concrete to fill that cavity, therefore restoring the retention capability of the quay wall. But while doing so, the contractor continues to excavate both on land and in the water.”
He said the contractor would also be “trimming the material on the inside.
“And that is done because while you cannot control the initial loss of material through the clutch, as you do the repairs and you excavate, you would expect additional loss, and then that now has to be controlled, done in a controlled manner.”
He explained that the divers can face a differential pressure hazard.
“And if you have water on the inside where there’s that loss of material at a different elevation than on the outside, then it creates a differential pressure, which is a very dangerous diving hazard, which also has to be factored in.
“So, the public will see photos appearing to be worse. But … what you see as looking at being worse for us, it’s actually the fix being applied.”
Affected area to be excavated
He said the contractor has to excavate and make the holes bigger because the loss of material was through the compacted fill.
“And it is possible that once that material is being lost, you can have cavities developing. So, the surface can look good, but the cavities can develop. So, it is prudent that you collapse along that entire quay wall to be certain that you have no cavities along that apron section, which is where the cranes and the containers would eventually land…
“They have to collapse the entire section. … On the land side of the port, you will see more water as the rectification goes along.”
He said other activities continue at the port “and that would not be done if it’s an unsafe, uncontrolled, erratic type of operation.
“So yes, you will see the excavation along the quay wall right along but by the time you get to June thereabout, and hopefully before, you will also see the recompaction (sic) occurring from the side to the fish market and progressing down.”
He said that once recompacting is done, “you get back to your normal scheme of things, of putting down the sub base material, the cement-treated base material, and then you finish your pavement layer.
“Once your pavement layer is then finished, you install your bollards, you install the fenders, you install the ladders, and you get ready for a boat,” Douglas said.
“So, for all intents and purposes, yes, there is an issue. The issue has a standard engineering fix. It is standard. It’s not novel. The issue that occurred is also not a novel situation that occurs when sheet piles are being driven, embedded on both sides with materials.”
Douglas said that while the deadline for the completion of the port has been extended from May to August, it is likely to exceed the Aug. 31, 2025, timeline.