Biddenham residents living next to a new housing development off Bromham Road say they are still concerned about future flood risk, months after first raising concerns about water runoff during construction.
Concerns about how the development, called Chariot Fields, would drain were first reported by the Local Democracy Reporting Service (LDRS) in October, when a neighbouring resident said water had begun flowing toward their property after the creation of a temporary access track and changes to ground levels.
Martin Shaw, who lives opposite the development, believes the drainage system planned for the 57 new homes is too small.
“This system is going to fail,” he said. “It is just a matter of time… and when it does, the residents of this site will have to pay for any repairs and/or replacements because the developers have purposely kept roads private to allow a drainage scheme to come forward, which the council would never have accepted if the roads were adopted.”
Read: Locals raise concerns over Biddenham development drainage
Bedford Borough Council is the Lead Local Flood Authority (LLFA) for its area, meaning its flood officers are responsible for assessing surface-water drainage and ensuring that proposed systems do not increase flood risk.
In March 2025, the LLFA issued a detailed objection to the site’s drainage plan.
The objection was written by the council’s flood investigation officer, Ollie Ewington, who highlighted several issues, including:
- Highways will not adopt the highway with an underground SuDS crate system
- A shortfall in surface-water storage volume, including an undersized storage attenuation basin
- The risk that the system would be unable to drain during periods of high river levels
- The accessibility and long-term maintainability of underground components
- Concerns that the access-road levels could direct water toward 112 and 112A Bromham Road if the system exceeded capacity or became blocked
The memo also warned that when the River Great Ouse bursts its banks, the proposed outlet level for the site could be fully submerged, preventing any discharge until water levels fell again.
New drainage design
Following those objections, Cala Homes submitted a revised drainage design.
In June, the LLFA confirmed it was satisfied that the updated scheme addressed the technical issues.
The approved design now includes:
- A non-return valve to stop floodwater from backing up from the River Ouse into the development’s surface-water storage system
- Redesigned underground storage using large-diameter pipes for improved maintenance access, although only parts of the system have been redesigned this way. Underground plastic storage crates are still present within the design
- Highway drainage is intended to divert excess flows away from neighbouring homes
The LLFA concluded that “the redesign of the surface water drainage/SuDS is now acceptable” and raised no objection to Condition 14 (a planning condition set when planning was approved) being discharged.
SuDS, or Sustainable Drainage Systems, are designed to store rainwater on site and release it slowly to reduce the risk of flooding.
Despite the redesign, Mr Shaw said he remains concerned about performance during extreme weather, particularly during prolonged periods of high river levels or intense rainfall.
Read: Biddenham local ‘throws mud’ at Council over construction work
He said the redesign does not address the LLFA’s previous objections and argues that the approved design shows the receiving watercourse sits higher than the surface-water sewer connection during high river levels.
Mr Shaw also points to drawings which he says indicate a surface-water connection into a partially full sewer.
He disputes whether the attenuation basin being constructed matches the storage volume shown on the approved drainage drawings.
Cala Homes says the basin is being delivered in accordance with the LLFA-approved design.
Mr Shaw said the non-return valve added to the surface-water sewer connection can remain shut during higher river peaks because it sits below the receiving watercourse at those times.
Cala said this is intentional design, with water held on site during high river levels and released once levels fall, in line with the LLFA-approved plans.
Mr Shaw argues this means the system will be unable to discharge during prolonged high river levels, increasing flood risk on site and for neighbouring properties.
He said the drainage system is therefore “incorrect and undersized” and will struggle to cope with the development’s surface water run-off.
“Gone around in circles”
“The council’s own objection to the reserved matters application detailed that the LLFA noted the attenuation basin should be positioned within Flood Zone One,” Mr Shaw added, “Which would then increase the height of the surface-water sewer connection, allowing the site to drain correctly.
“This was the correct stance to take, although this fell away once the planning received approval through a public inquiry process.
“During that process, the council did not defend the drainage objection. The drainage was then approved through a condition set within the outline approval for the site.”
When raising these concerns with the council, he said he feels “we have basically gone around in circles” with the drainage issue.
Mr Shaw said he had issued a formal complaint about the drainage design to the council, but that his complaint was dismissed and the council did not respond to or comment on the design flaws he raised.
He said he believes the council has “purposely avoided answering” these issues, adding that the points he has raised are basic engineering, yet the LLFA has still approved the design.
Mr Shaw said temporary construction arrangements, which he had previously warned the council about, have already resulted in run-off reaching driveways, as previously reported by the LDRS, and he fears the permanent system could be tested as the climate becomes wetter.
“All we have been asking is that the council ensures this drainage scheme doesn’t flood us – during construction or once the development is finished,” he said.
Both Cala and the council (in correspondence with Mr Shaw) say that the final drainage system meets the technical requirements.
A spokesperson for Cala Homes said: “The attenuation basin is being delivered in accordance with the drainage system approved by the Lead Local Flood Authority and has been independently reviewed by two engineering consultants, both of whom support the proposals.”
Cala said final “as-built” drainage verification drawings have not yet been submitted to the LLFA, adding that construction is being carried out in accordance with the approved plans.
The council did not respond to a request for comment.
Mr Shaw said he will continue to monitor how the development interacts with neighbouring homes once construction progresses.
By John Guinn
Local Democracy Reporter
