Bury St Edmunds Compiegne Way flooding: Results of council investigation revealed
Recommendations have been drafted in a bid to solve ongoing flooding on a major route in Bury St Edmunds.
The A143 Compiegne Way repeatedly floods following heavy rainfall causing widespread disruption for residents and businesses in the town.
It was closed for nearly four weeks in January due to flooding and the road was most recently waterlogged on Saturday.
Suffolk County Council fast tracked an investigation to identify the sources of the flooding and likely causes as well as recommend short, medium and long term actions.
The report, due to be published next week but seen by SuffolkNews, said the repeated flooding was linked to surface water and groundwater sources, with water rising faster than the pumping system can cope with.
Water is pumped via a 1km pipeline to the River Lark, where the outfall sits below peak water levels which also hinders the pumping operation.
Matt Hullis, head of environment strategy, said the pump system works as is designed but there was too much water.
“You’ve basically got the taps on and you’re pumping out slower than the water is coming in,” he said.
“The system works but it’s looking at other ways of stopping as much water getting to that location to allow the existing pumps to work.
“You can’t stop the groundwater because that would involve massive pumps pumping all the water out the surrounding chalk way.
“The other thing you can do is stop the surface water.
“Can we intercept those flows coming down the roads and off the fields and stop it getting to that low point?
“The obvious question is why don’t you put a bigger pump in? Pumps are fundamentally a poor way of managing drainage because you have to constantly maintain them and they cost a lot of money to run.
“Here we have a massive problem with silt because of the type of traffic. A pump full of silt doesn’t work very well so you have to constantly clean it.
“You have to look at other ways of stopping as much water getting down there but we have our hands tied because it’s a low point and it’s got chalk which holds an awful lot of water.
“Groundwater levels are at exceptional high levels so a little bit of rain tops it up again.
“We’re maintaining the system we’ve got as well as we can and there’s been a lot of investment in that and now we’re looking at ways to try and reduce the amount of water that ends up at that low point.”
Groundwater has been sitting at or just below the road surface with water reported in the drainage network even after no rainfall, the report said.
There is no natural point of discharge for the water and high levels of silt from HGVs carrying beet to British Sugar combined with a change to highway maintenance results in very frequent pump burnout.
The report said: “Whilst the lack of maintenance has been considered by many to be the main cause of the flooding, given that the system was cleansed and pumps replaced in January 2024, and the road closed again due to flooding less than a month later in February 2024, it is clear there are other more significant factors at play.”
It also highlighted a large catchment of 1.6km of highway relying exclusively on pumped drainage, with any pump failure resulting in significant impacts.
An assessment of the nearby reservoir owned by British Sugar found no evidence of leaks and although some water naturally dissipates to the ground, it has a ‘minor impact at most on the flooding and far outweighed by the shallow groundwater issues’.
Short term actions recommended in the next 12 months include extending the pump design life and reducing pollution to the River Lark by replacing filter drains, changing the maintenance regime to include proactive maintenance for the most heavily silt laden section of the highway and treatment upstream of the pumps.
They will also look at increasing the frequency of street cleansing.
In the medium term, they would look at commissioning a ground investigation to confirm underlying geology and installing boreholes to monitor groundwater levels to prepare for flooding.
Other medium term actions to be considered are reducing highway catchment relying on the pumped system by diverting the most westerly section of Compiegne Way directly to the river via suitable pollution mitigation.
Roadside ditches could also be added as well as lifting the level of the outfall to the River Lark to reduce times when pumps cannot operate at full capacity.
Investigations for the medium term actions could start in the next 12 months or so.
Long term actions with significantly greater timescales and budget demands include raising the level of the road above ground water level to prevent it being subject to flooding frequently and rerouting traffic on Compiegne Way to prevent it being displaced onto local roads during flooding.
Another recommendation would be to increase pump and network capacity which the report said should only be considered as a last resort as pumping groundwater into the River Lark via a highways drainage network was not a sustainable long term solution.
The council has already cleared the road of excess water and silt to access the drains for remedial works and cleaned the drains, replaced pumps and repaired the road surface.
Mr Hullis said his team produced the report as independent engineers looking at what’s possible.
“We’re writing about things that could happen that have the potential to reduce flood risk in this location but what this isn’t is a list of things we’re going to work through and deliver all of them,” he said.
“That would be dependent on available resources, time and competing constraints.
“This is a list of possible things that could happen if the responsible risk management authority is able to fund them and prioritise them amongst all the other things they’ve got to do.
“To be frank some of these things may never happen. Others are essentially no-brainers that we should get on and do as quickly as possible. Some have been done already.
“The shorter term ones are things we feel that people have the capacity to do and are likely to be able to deliver reasonably quickly.”
A Freedom of Information request into repairs carried out in Compiegne Way found that in 2019, the replacement of a filter drain, new signs, posts and crash barrier works as well as pump repairs and replacement cost £547,998.82.
Jo Churchill, former MP for Bury St Edmunds, previously told SuffolkNews that last year, a colossal amount of work was carried out with new pumps installed and desilting, costing about £550,000.
