Dredging danger away

“In over 20 years of working with pollution incidents on canals, I’ve never known anything like it,’ explains Karen Jackson, our national Waste and Contamination Officer. “We’re used to dealing with many pollution incidents such as oil spills, agricultural run-off or contamination from fires on waterside property, where we know exactly what we need to do.

But with 4,000 litres of contaminant, including highly toxic sodium cyanide and zinc cyanide leaking into the canal from a local factory, this was unprecedented – a new level of risk to public health and devastating to the local ecosystem. Many more people were involved, from the police to the fire service; from local councils to the Environment Agency.”

But in the midst of the incident, Karen says our charity acted decisively, quickly closing 12 miles of canal to boaters and the public while it was assessed by the Environment Agency, before damming off one kilometre of what proved to be the contaminated stretch.

“Initially, we took a very precautionary approach,” says Karen, “while the public health risk from what’s known as ‘free cyanides’ could be established. These ‘free’ molecules can be particularly unstable, reactive and dangerous to both humans and wildlife.”

Indeed, in the early days of the spill, there wasn’t anything that could be done to prevent the mortality of over 90kg fish which were recovered from the canal. Thankfully, no people were harmed. By containing the spill so quickly, we managed to stabilise most of the contaminants in the silt along that one kilometre stretch and were able to reopen parts of the canal where it had been proven safe to do so.

In the months that followed, the Environment Agency continue to investigate the company identified as the source of the pollution. Although all the legal and financial issues are still to be resolved, the dredging programme, at least, has been paid for by loss adjusters appointed by the polluters.

As Karen explains, months of testing have made it increasingly clear that this expensive work was essential. “The canal water has been regularly tested, and as you might expect, the chemicals in the water have begun to break down and be less harmful.

“Attention has now moved to the sediment. Although much of the cyanide was in a non-soluble form, it could easily be released by changes to water chemistry or disturbance by boat traffic. It would be too much of a risk to leave the contaminated silt in place, so over the last three weeks, the most contaminated silt has been dredged and taken by sealed wagons to a waste treatment site to be stabilised and later disposed.”

Karen says that’s not such an unusual thing for us on canals. Whilst the water quality in canals is better than at any time in history for them to become such vital wildlife corridors in our towns and cities, the Industrial Revolution, with its former heavy canal-side industry, has left us with a legacy of contamination to this day. In fact, around 10-15% of the material we dredge can be classified as hazardous waste and needs to be transported significant distances to these specialised treatment centres. That’s part of the reason why so many of our dredging operations are so carefully planned, costed, and monitored.

But now, at least in Walsall, there’s hope that the canal can reopen, and wildlife can begin to recover once this dredged stretch is shown to be safe again. More testing and a full ecological assessment will be needed before we decide on the next steps, but as Henriette Breukelaar, the regional director, commented:

“The dredging of the Walsall Canal…is a major milestone in the canal’s recovery since the spillage in 2024. But although the company involved is paying for the dredging operation, it’s still costing our charity around half a million pounds, covering staff time, dam installation, materials, contractors, and lab testing. A huge amount of resource has been diverted from other essential activities that keep the region’s canals open and safe.

“We are grateful for the support of our partners and the generosity of the public, particularly those who contributed to the Crowdfunder, which raised £25,000. This will help ensure the canal remains a vital part of the local community and, hopefully soon, can fully reopen.”