Hazardous Materials In Manchester Water As National Highways Assets Uninspected Since 2007

Watercourses around motorways in Greater Manchester could be filled with hazardous materials as National Highways has failed to inspect runoff interceptors designed to to prevent this since as long ago as 2007 - an oversight that has been compared to the UK’s sewage scandal.

The data was revealed under the Freedom of Information (FOI) Act by National Highways in response to a request to reveal the inspection and maintenance schedules for runoff ponds and interceptors alongside motorways around the Greater Manchester area including the M56, M60 and M62.

A member of the public made the request and passed the responses to NCE.

What is road runoff?

When vehicles are driven, they undergo wear and tear. Solid parts like tyres and brake pads shed tiny particles into the environment. In addition, liquids like fuel, oil and screen wash fall onto highways and are washed into drainage systems.

A significant proportion of these pollutants will exit highways via less managed pathways like gulleys, but some will enter fully managed drainage systems which could feature hard engineering solutions such as oil and water separators and drainage ponds.

Those engineered systems need to be maintained to work properly. The BS EN 858-2:2003 standard for separator systems says separators should “be serviced and maintained as a minimum on a six monthly basis”, according to environmental consultancy Adler & Allan.

Stormwater Shepherds is a not-for-profit working to improve the health of waterways and its director of operations UK Jo Bradley said: “Although this isn’t a mandatory standard in the UK, it is recognised good practice and should be reflected in National Highways’ own maintenance schedules.”

What did the FOI say?

National Highways carries out inspections and maintenance of its runoff interceptors and ponds in Greater Manchester in-house. This is different to its regime for the M25, which NCE previously investigated, where this work is undertaken by to Connect Plus Services.

Regarding its inspections in Greater Manchester, National Highways released data on the most recent inspection and cleanse dates of 35 interceptors and one runoff pond named “Kenworthy Lane Balancing Pond”.

It also identified two interceptors on the A627M between Oldham and Rochdale, but the data on their inspection and cleanse dates was missing.

In its FOI response, National Highways said the spreadsheets it provided “shows the information we hold in Confirm, our asset management database”.

It went on to say: “Please note that the runoff ponds with inspections dating between 2007- 2012 are likely to have been inspected since, but our records are unable to verify this.”

Despite the highways body carrying out the interceptor inspections itself, the FOI response said that for two assets on the A627M the request was refused because “National Highways does not hold this information”. No explanation was provided for why the information was not held.

What did the data reveal?

The data showed 37 interceptors located in Rochdale, Manchester, Bury, Tameside, Stockport and Trafford.

Of the 35 interceptors where dates were available, the last inspection and cleanse dates ranged from 2007 to 2018, but the inspections and cleans were always carried out on the same day.

Seven interceptors were last inspected and cleaned in 2007, meaning they have been left to accumulate runoff for up to 18 years. Cleanses are always recorded to have taken place on the same day as the last inspection.

One was last inspected and cleaned in 2009, seven in 2010, two in 2012, one in 2015, five in 2016, and the remaining 12 with dates listed were last cleaned in 2018 – seven years ago.

National Highways said it last looked at the Kenworthy Lane Balancing Pond in 2022 and did not clean it because it had been cleaned recently.

Visual evidence that the ponds have not been cleaned

While National Highways claimed that “runoff ponds with inspections dating between 2007- 2012 are likely to have been inspected since”, on-the-ground inspection reveals this is in fact unlikely.

Bradley visited one of National Highways’ interceptors between junctions 6 and 7 on the M60 and found it overgrown with evidence of historic fly tipping having taken place.

A photo of a sign which says 'PCD' meaning pollution control device, which is a runoff interceptor, with fly tipping visible in the foreground. Source: Jo Bradley

“You know that they haven’t been emptied for 15 years; we can see that because we can see that the trees have grown up around the manholes and the around the device,” Bradley said.

“And those should have been inspected every six months and emptied when the sediment traps were 80% full. National Highways’ own guidance is every two years as a minimum.”

Explaining how the devices are supposed to work, she said: “Oil/water separators are simply big vessels that rely on residence time. As long as it’s big enough, and it was designed well, the runoff will reside in there when it’s raining for [approximately] six minutes, and some of the sediment will settle out.

“As long as you empty it and clean it and reinstate it, it should still work. It’s very simple physics.”

She also explained how the devices could be returned to their operating function.

“[National Highways] would have to go and find the manholes, and then clear access to the manholes, and then empty the tank.

“After however long it’s been since they emptied this one, it would be tough, because the sediment congeals. It goes really hard because it’s grit and dirt and organic matter. It becomes quite difficult to shift.

“National Highways would have to get a specialist contractor in to empty it. And then it should empty it every two years”, she said.

Environmentalists say runoff mitigation ‘low priority’ for National Highways

Friends of the Earth nature campaigner Paul de Zylva analysed the data shared by National Highways under the FOI Act.

“It’s increasingly clear that on top of the sewage scandal, our rivers and waters courses are also in a poor state due to pollution flowing off the nation’s roads and verges,” de Zylva said.

“This ‘road run-off’ includes engine oil, brake dust and fluid, and heavy metals from vehicles. These toxins often combine with tiny rubber particles from eroded tyres and microplastics from discarded litter - particularly take away food packaging.

“Over time, these pollutants get blown and washed into rivers and waterways near to roads, where they’re carried far and wide. Unfortunately, this seems to be a low priority for our highways authorities and the Environment Agency, as the lack of inspections reflect.”

National Highways commits to ‘reactive maintenance’ only

A spokesperson from National Highways said: “National Highways is committed to improving water quality, and our Water Quality Plan sets out a high-level programme of work to address all our high-risk outfalls by 2030.

“Our planned approach for Greater Manchester in 2025/26 is to inspect each interceptor annually and for reactive maintenance to be instructed on a needs basis following the inspection.”

In August 2024, WSP was appointed to the role of technical partner on National Highways’ Water Quality Plan.

The Water Quality Plan aims to “improve knowledge around water run-off from the strategic road network and mitigate the environmental impact of high-risk outfalls as part of National Highways’ Environmental Sustainability Strategy”, according to the consultancy.

WSP said it would be supported by Mott MacDonald, Ramboll and Aecom to carry out the work.  “Working alongside our partners, WSP will provide strong programme management and delivery arrangements to March 2025, with scope to continue to 2030,” it said at the time of its appointment.

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