Hasselt (Brussels Morning Newspaper) – Hasselt’s Molenpoortplein sewer, 8 m deep with 1.7 m pipes, was inspected by diver Xavier Slock (Octopus R&M) after flooding; Fluvius found heavy silt, but pipes remain intact, cleaning planned.
As VRT News reported, residents in Hasselt city centre were surprised yesterday, Nov 15, 2025, when a professional diver descended into a culvert and entered the city’s sewer system. The operation was confirmed by Fluvius and reported by Het Belang van Limburg.
“We received reports of flooding at various locations in Hasselt. A large sewer pipe runs under the city centre, carrying rainwater and wastewater to a collection point. We suspected there was a constriction there, so we decided, together with the city, to have a culvert lowered,”
David Callens of Fluvius said.
What did diver Xavier Slock discover in Hasselt’s sewer after flooding?
Workers were trying to find the source of the recent flooding in the area. The work took place under Molenpoortplein, where the sewer pipes reach a depth of 8 meters. David Callens from Fluvius said the pipes are very large, with a diameter of 1.7 meters. He added that inspecting this part of the sewer is difficult because of the size and depth of the tunnels.
“It is indeed the main sewer that connects the town centre to the water treatment plant in Kuringen,”
adds alderman Laurence Libert (N-VA/Open VLD).
“That pipe hadn’t been inspected for quite some time, and we’ve received reports. We shouldn’t fear major flooding in the town centre. You want to prevent a clogged sewer, which is why we’re conducting this investigation.”
The diver who carried out the work was Xavier Slock, CEO of Octopus R&M, a diving company from Maasmechelen. The company is known for diving into shipping and water treatment projects.
“This was a first for us, too. I never thought I’d be able to do this in the city. It was a great challenge to gain experience.”
“The visibility is zero down there. It’s like feeling your way through your house in the dark. Over the years, we’ve developed techniques to carry out inspections,”
said the diver.
“We also wear chemical suits while diving. These are completely sealed, as we’re diving in heavily polluted water,”
he continues.
“We often dive at water treatment plants at companies where we have to be on the lookout for chemicals. Our helmets are fully equipped with communication equipment and an external air supply.
We get oxygen through an air hose, so we can stay underwater indefinitely. We do carry an oxygen tank for emergencies.”
Fluvius said the inspection quickly showed that a large part of the sewer pipes was silted up.
“This is mainly due to a buildup of debris such as grease and gravel. At one point, there was only an opening of 40 centimetres,”
Callens explains.
“At the first dive site beneath Molenpoortplein, it was mainly accumulated fats. Those are harder to remove,”
says diver Slock.
“At the sewer outlet, right in front of the Holiday Inn Hotel, it was mainly sand and gravel. It reminded me of construction waste.”
“The good news is that the sewer pipes themselves do not need to be replaced.”
David Callens, spokesperson for Fluvius
Sediment had partially blocked the flow and may have caused the recent flooding in Hasselt. David Callens of Fluvius said the problem was under control. He added that finding the blockage early allows the pipes to be cleaned and repaired before more serious damage occurs.
“The investigation shows that the pipes themselves are intact. Fortunately, we don’t need to replace the sewer pipes. We will, however, have to clean them and remove all the sludge.
We won’t wait long for that. We will work with the city to determine how and when we can do that,”
David Callens said.
Alderman Libert said that after the cleaning and maintenance, the sewer system will be able to handle heavy rain and other extreme weather for decades. Octopus R&M, the Maasmechelen diving company that carried out the operation, has seen more requests for similar inspections.
“These requests come from businesses, but also from private individuals and municipal authorities. I think this is mainly due to the high degree of paving.”
“At the same time, large quantities of water sometimes need to be able to drain away in an emergency. For example, at the Flemish Waterway, we hear that over time, more and more silt and sediment settle. That also plays a role, for example, here in Hasselt,”
concludes Slock.
Hasselt has faced flooding problems for years. In July 2021, heavy rain caused serious flooding across the Demer basin, including parts of Hasselt like Stevoort. Authorities said the city narrowly avoided a major disaster. In January 2025, new flooding hit the Spalbeek area, especially on Wijerstraat. The city responded by planning extra retention basins and separating wastewater from rainwater to prevent future problems.
