Dredgers are here again

The excavator lifts another scoopful of mud from the bottom of the River Aura and dumps it on the barge waiting next to it. Once the barge is full, a tugboat will take it to the Lauttaranta district on Hirvensalo island.

The work has continued in the same way since January. The movements need to be repeated countless times before the project is ready on the River Aura. After that, sometime in April, dredging will commence in the Port and its fairways.

“The River Aura is dredged above all to allow the access of the participants of the Tall Ships Races to Turku in the summer. The dredging of the Port will ensure that the harbour basins and fairways have the promised draught for vessel traffic”, says Markku Alahäme, Technical Director of the Port of Turku.

The dredging of the River Aura is the responsibility of the City, while the Port takes care of the dredging of the harbour basin and fairways.

“The Port’s area starts at the quays towards the sea approximately where m/s Bore is moored. On the River Aura it’s a very fine line”, Mr Alahäme says.

Dredging masses are put to use

In Lauttaranta, the dredging masses are used to raise the ground level in order to be able to build a residential area there in the future.

Two new disposal pools have been built in the Lauttaranta district for this year’s dredging. Water is removed from the dredging masses and they are stabilised, which increases their bearing capacity.

“We expect that some 45,000 cubic metres of dredging masses will accumulate from the River Aura and under 20,000 cubic metres from the harbour basin and fairways.”

The River Aura was last dredged in 2008–2009. The last maintenance dredging in the Port was implemented in 2018. In the future, the plan is to carry out maintenance dredging in the Port at intervals of around five years.

“According to a follow-up study, the River Aura carries annually around 30,000 cubic metres of clay from its upper reaches to the Port and its fairways.”

Archaeologists follow up on the dredging

The dredging of the Port fairways will start in the Pansio fairway, and next up is the inner harbour fairway leading to the tip of the Ruissalo island. Mr Alahäme says that the project will be finished by the end of the summer.

The dredging will also be followed up by archaeologists, in case something historically valuable is found at the bottom of the River Aura, in the Port or on the fairways. In 1971, the remains of a Dutch ship from the 18th century, known as the Pikisaari wreck, were found in the fairway.

“The contractor uses a screen through which the dredging masses are lowered and which will stop any bigger items. But I don’t think that anything will be found at least in the Port areas, as it has been dredged so much in earlier times.”

There is just one more thing to check. Surely there is no risk that the performers at the Ruisrock festival in July would be accompanied by a rhythm section of dredgers?

“The work will be scheduled in such a way that there is no such risk”, Markku Alahäme says and chuckles.

Text: Matti Välimäki
Photos: Ilari Välimäki