On and off for six months, a giant underwater vacuum cleaner has been sucking up silt and debris from the seabed near the Tom Clarke Bridge.

Soon it will stop. But in another six months, the vacuuming is due to start again.

The hoover is actually a ship called the Freeway, a “trailer suction hopper dredger”. Sometimes underwater debris gets stuck in its big metal grille, while fine silt and soil flow into its main cargo hold.

Then, the “dredge head” gets lifted onto deck. That’s where Dr Niall Brady, founding director of the Archaeological Diving Company, comes in.

Brady’s job is to oversee and catalogue whatever is unearthed by marine dredging and construction work during the port’s efforts to modernise and grow.

“We look inside the grille to see if there’s anything caught. And there will be ropes and metal and debris – modern stuff. But there will also be archaeological material,” he says.

What They’ve Found

“Welcome to the pump house,” Brady says, opening the doors of an old brown brick building next to the now closed Graving Dock 1, where ships used to be repaired.

Inside is a long workbench covered in cellophane-wrapped bits of metal. Tarpaulins on the floor cover chunks of wood and stone.

There are metal capstans, hydraulic arms taken off the quayside, and a black box generator from a decommissioned generating house “that looks like it walked out of a scene from Frankenstein”, Brady says.

“These are some of the metal pieces that have been lying in the silts, undisturbed, for quite a long number of years,” Brady says, motioning to the workbench.

There are hoops from old wooden barrels, parts of an anchor, and heavy pieces of metal from modern vessels.

They’ve all come up from the first season of “capital dredging” in the seabed in the navigation channel, says Brady.

Capital dredging is when a seabed has never been dredged before. An archaeologist has to be present.

The navigation channel stretches out 10 kilometers from the Tom Clarke Bridge. It’s being dredged as part of the Alexandra Basin Redevelopment Project – and in an effort to make it deeper for the future shipping that’s expected.

Improving capacity is one arm of Dublin Port’s current masterplan. The other is engaging with the city and its heritage, says Lar Joye, the port’s heritage director.

Brady estimates they’ve found 250 artefacts over two seasons of dredging. His job is to recover “all the items of past usage, no matter how recent”, catalogue them, and keep them in stable condition, he says.

Joye says the port and its companies can trace their lineage back to 1707, so there’ll be lots of stories to come across. “It’s not always going to be gold bullion. Sometimes it’s just going to be stone,” he says.

The Millstone Wreck

In the far corner of the pump house, Brady points to the two halves of a large millstone.

They were discovered during the first season of dredging, he says. The stone was recovered from a previously unrecorded shipwreck.

“It’s probably an 18th century cargo ship that would have gone up and down Irish coast bringing things in and out of Dublin,” Brady said.

The millstone is made from an old, red sandstone, Brady says. It’s from a spot on the Hook Head Peninsula in Wexford. The’ve even pinpointed the quarry it came from.

“Since the late 1600s, people have been quarrying that stone to make these, which are then shipped up and down the east coast,” Brady says.

They’re still trying to figure out more about the ship, including its name. For now, they’re calling it the Millstone Wreck.

The vessel was carrying a couple of millstones and foundered just off North Bull Island, says Brady. “She came to rest on the old sandbar, which is the Dublin bar.”

Records show more than 300 vessels that have suffered similar fates, says Brady. “But of those, only 18 are known in specific locations.”

That leaves 282 to find.

“The vessel is more or less intact. The upper decks are gone, but … her whole underside is intact in the soft sediments at the side of the navigation channel,” Brady says.

The pumphouse. Photo by Erin McGuire

For now, the Millstone Wreck is staying put underwater. There’s an exclusion zone around it for its protection.

Sometimes it’s better to leave an artefact be, says Joye. “Once something comes out of the water, it has to be preserved very quickly.”

If that doesn’t happen, rust and decay will set in. “[Y]ou’ll lose a historical object right before your eyes. It’s not pretty to watch,” says Joye.

Bathtubs for Timbers

Outside the pump house are several large metal tanks. In a couple of them, old ships’ timbers marinate in water. Another tank has been drained, its timbers wrapped tightly in cellophane.

They’re waterlogged to keep their integrity, says Brady. “So we study them by removing them and wrapping them, measuring them, photographing them, figuring out what part of a ship they come from. And then using that information to build our story, knit everything together.”

They’ve got to sit down and work out what it all means, says Brady. “We have to create that monster of a jigsaw puzzle.”

All the artefacts recovered are, by default, the property of the state. It’s up to the National Museum of Ireland to decide where they go, Brady says.

In the future, the may end up in a port museum, says Joye. Dublin Port hopes to develop one in the future.

“It’s a vital part of the city’s history, and without it, there was really no need to have Dublin based here. That’s why the Vikings came here. It’s why everyone else came here,” Joye says.

Brady says the finds “demonstrate, unequivocally, how integral the bay and the river are to the growth, development, and prosperity of the city”.

The port’s refurbishment isn’t such a new idea either, he says. Altering it to accommodate larger and larger ships “is precisely the same challenge faced by the fathers of the city” hundreds of years ago, Brady says.

Technology has changed, and the capacity has grown, but the challenges are the same, he says. “How do you ensure all-time, all-weather access up the Liffey for shipping? Because the shipping’s coming, and it’s only getting bigger.”

That story hasn’t changed in over 600 years, he says. “And it’s not going to change in the future either.”

Erin McGuire is a city reporter. Her stories often offer an intimate window into the lives of those we share the city with. You can reach her at erin@dublininquirer.com.

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