Freedom of Information Request: What CDC Really Said About West Adderbury Flood Risk

You may remember that back in August we reported that West Adderbury Residents Association (WARA) had written to Adderbury Parish Council (APC) regarding residents’ concerns about a potential flood risk to homes in Tanners Lane, Round Close Road and Horn Hill Road caused by work carried out by APC on the Milton Road field.

This risk is the result of APC installing a drainage (infiltration) basin which is far smaller than the basin approved by CDC’s engineers.  An infiltration basin is designed to capture and store rainwater, before discharging it gradually into local water courses and underground drains.

Mrs Diane Bratt, Chair of APC, replied to WARA on 21 August 20 (see email below) by saying that:

“The infiltration basin currently in place is acceptable to CDC”.

A similar statement was made by the Parish Council in the October 2020 issue of the Contact magazine, in which APC claims that:

“The PC does have CDC’s agreement on everything we’ve done so far” and “Everything has been done within the planning permissions granted”.

[This second statement appears to be factually incorrect, since CDC have confirmed in writing that APC have in fact breached conditions 8 and 18 of the planning permission.]

The statements by Mrs Bratt and APC that all was well between APC and the District Council appeared to contradict the information being given to West Adderbury residents by CDC.  Rather than confirming that the current drainage scheme was “acceptable”, CDC officers were saying that CDC has written to APC regarding installing the correct drainage scheme, but has had no response.

To clarify the situation, a Freedom of Information request was submitted to obtain written communications between CDC and APC on the subject of the drainage scheme to be implemented for the Milton Road field (you can read more about why this scheme is so important here).

The documents obtained via the Freedom of Information request show (see 28-07-2020 Emails to Parish Council Clerk and 31-07-2020 Emails to Parish Council Chairman) that CDC officer Sean Tilbury wrote to Mrs Diane Bratt on 28 July 2020.

In his email, Mr Tilbury says:

“Following completion of the pitch drainage works, new concerns were raised to the District Council alleging that the works were not in accordance with the approved plans and that they increased flood risk.

The current basin measures about 4m in diameter by about 750mm deep.  The approved infiltration basin has significantly greater capacity at approximately 25m in diameter.

Now that the pitch drainage has been installed, water will much more readily pass through the surface and be readily intercepted by the under-drains.  The pitches will behave much more in the manner of an impermeable surface and concentrate flows to the swale.

Therefore, there is now a greater flood risk downstream than there was when the field was pasture or arable.  For this reason it is important that the basin is completed.

I sought advice from a drainage engineer and he advised that the full-sized basin should be completed before the onset of Autumn to mitigate avoidable flood risk.

The final thing I noted was that the current basin has 2 inlets when only one was approved and 1 outlet, none of which were approved”.

Sean Tilbury goes on to clarify that the lack of a full-size basin does not appear to be a breach of planning control, as condition 3 only has to be implemented prior to the completion of the development.  However, he also points out that the “current drainage basin is not authorised“.

This email does seem to contradict Mrs Bratt’s statement to WARA that the current infiltration basin is “acceptable to CDC”.

Sean Tilbury makes it clear that the current infiltration basin is too small and increases flood risk downstream, and that the approved, full-sized basin should be completed before the onset of Autumn.

Incidentally “downstream” in this case means houses and property in West Adderbury, in particular, in Tanners Lane, Round Close Road and Horn Hill Road, which previously suffered severe flooding when the underground field drain into which the Parish Council’s infiltration basin discharges became blocked.

How does Mrs Bratt respond to Mr Tilbury’s email?  Did she promise to take immediate action to install the full-sized basin so that West Adderbury residents would no longer be at risk from flooding?  Failing this, did she promise to look into the situation and take action if necessary?


Despite the fact that Sean Tilbury is a planning officer for the District Council, and despite the fact that he says he has “sought advice from a drainage engineer”, in her email of 30 July 2020 Mrs Bratt simply disagrees with him (see 31-07-2020 Emails to Parish Council Chairman) and states that “there is no increased risk of flooding downstream“.

Mrs Bratt also states that “With reference to the infiltration basin, the size required by the FEDS-220021-002-A site plan … is designed for both the pitch area and the MUGA.  As there is currently no requirement to drain the MUGA (there being none) there is therefore no requirement for the basin to be at full capacity”.

This statement is important as it clearly shows that Mrs Bratt recognises that the infiltration basin installed by APC is not the approved basin required by the site plan and that it has lower capacity than the approved basin.

Mrs Bratt then makes the rather odd statement that “The current basin has been provided in order to investigate the performance of the final basin”.

Mrs Bratt also refers to the letter sent to APC by the District Council on 19 June 2020, in which CDC explicitly states that:

Concerns were raised regarding flooding, although this is not a breach of planning control. Nevertheless a Drainage Engineer has visited the site and does not perceive an increased risk of flooding. I understand that the pitch drainage works are to proceed, which they may do so given the approval of the relevant planning condition. Whilst there is no stipulation relating to the order of which the drainage system is to be constructed, the Council does not recommend the pitch drainage system to be completed until the infiltration basin is also operational to ensure that surface water run-off is not concentrated in a singular location“.

Back in June 2020, Mrs Bratt was therefore advised that in CDC’s opinion, the approved infiltration basin should be installed before the pitch drainage system was completed.

APC ignored this advice.  We know that Mrs Bratt received this advice because she refers to it in her email.

Sean Tilbury responded by email to Mrs Bratt on 31 July 2020.

He states that:

“I note your comment that without the MUGA the basin does not need to be at full capacity.  However, the two pitches cover the significant majority of the total drained area and I would have expected that the majority of the designed capacity would therefore be required.  Approximate calculations put the current basin at less than 15% capacity of the approved basin.

The Council does appreciate that a basin has been provided as it is an improvement over there being no basin at all.  With regards to testing the performance of the basin, this is not something I had envisaged as the basin is required to meet the capacity calculated within the approved FEDS document”.

With regard to the letter of 19 June 2020, Mr Tilbury says:

“When the Drainage Engineer initially visited the site in June he did not perceive a greater flood risk but that was prior to the pitch drainage works being completed.  His assessment then was solely based on the level changes and vegetation removal.  The latest assessment differs as it is in response to the drainage works which he considers to have made a material impact on the way the land drains

I acknowledge your disagreement that there is no greater flood risk downstream and I will forward your reasoning on to the engineer for a response.  The flow rate of water is likely to be greater through the unrestricted outlet pipe than it would be infiltrating through the ground“.

Sean Tilbury’s last email to APC regarding the flood risk to West Adderbury was on 31 July 2020.  No further documents have been provided in response to the FOI request, therefore we must assume that there has been no further written correspondence between APC and CDC on this matter.

To summarise:

On 19 July 2020, Mrs Bratt was informed in writing by CDC that concerns had been raised about flooding in West Adderbury.  She was advised that the approved infiltration basin should be installed prior to completion of the drainage system.

This was not done.

On 28 July 2020, Mrs Bratt was informed in writing that the drainage system installed by APC has caused “a greater flood risk downstream” and that “it is important that the basin [i.e. the approved basin] is completed … before the onset of Autumn”.

This was again not done.

In her email of 30 July, Mrs Bratt states that there is no increased flood risk [it is unclear why Mrs Bratt believes she is more qualified to comment on this than CDC Drainage Engineer] but also confirms that she is aware that the basin APC has installed is smaller than the approved basin.

On 31 July 2020, Mrs Bratt is informed in writing by CDC that the basin APC has installed is less than 15% the capacity of the approved basin and that CDC’s drainage engineer’s assessment that there is a greater flood risk downstream is in fact based on the impact of the drainage works APC have installed.

As far as we know, there has been no response from APC to CDC’s comments and to date no changes have been made to the drainage system.

We are now coming towards the end of October and are certainly beyond the “onset of Autumn”.  Our Parish Council has taken no visible steps to mitigate the risk that it has imposed upon residents of West Adderbury.

Instead, APC have published several statements which suggest that CDC considers their drainage system to be “acceptable” and that the Parish Council has “CDC’s agreement on everything we’ve done so far”.  Based on the email communication between CDC and Mrs Bratt, this does not appear to be true.  Of course, if APC has received written confirmation from CDC that the current infiltration basin is acceptable, we would be glad to receive and publish it.

On 24 August 2020, the Parish Council published a statement on its Facebook page stating:

“More photos of the pitches which are coming along nicely on Milton Road. Also a snap of the infiltration basin doing it’s job – there has been 30mm of rain since the field drainage has been in place and everything is working brilliantly as the basin has hardly been touched”.

The photograph below, taken by a West Adderbury resident in early October, tells a very different story.  Will an infiltration basin that has just 15% of the required capacity – according to the District Council’s qualified Drainage Engineer – make it through the next few months without being overwhelmed during heavy rainfall?

And if it doesn’t, and West Adderbury properties are flooded as a result, who will be to blame?

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