Milton Road Drainage Further Info

Click here for the Planning Conditions set by Cherwell DC for 18/00220/F (the Parish’s Council’s application for change of use of the Milton Road from agricultural land to  sport/recreation and community use).

Condition 3 of 18/00220/F related to the drainage scheme for the pitches and is copied below. 

3          Prior to the commencement of the development, details of a surface water drainage scheme for the pitch area of the site, which shall accord with the drainage strategy (FEDS – 218041 – Rev A prepared by Forge Engineering Design Solutions Ltd) shall be submitted to and approved in writing by the Local Planning Authority. The scheme shall subsequently be implemented in accordance with the approved details before the development is completed. The scheme shall include:

  • SUDS (Infiltration trench)
  • Detailed drainage layout with pipe numbers
  • Maintenance and management of SUDS features (To include provision of a SuDS Management and Maintenance Plan)

Reason – To ensure satisfactory drainage of the site in the interests of public health, to avoid flooding of adjacent land and property and to comply with saved Policy ENV1 of the Cherwell Local Plan 1996 and Government guidance contained within the National Planning Policy Framework.

Conditions 3 was discharged (i.e. completed) when the Parish Council submitted a drainage strategy, designed by Forge Engineering Solutions, which was approved by Cherwell DC:

Condition 3

The details of the surface water drainage scheme for the pitch area of the site as set out in document titled ‘Phase 1 Sports Pitches SuDS Calculations’ prepared by Forge Engineering Design Solutions Ltd which includes the ‘Infiltration Basin Operation and Maintenance in Accordance with The SuDS Manual 2015’ Plan and drawing numbers FEDS 218132-001_Rev A A (Phase 1 Sports Pitches’ Sustainable Drainage System Layout) and FEDS 218132-002 Rev A (Sustainable Drainage System Details) are considered to be acceptable to ensure satisfactory drainage of the site in the interests of public health and to avoid flooding of adjacent land and property. The applicant is reminded of the need for the scheme to be implemented in accordance with the details hereby approved.

The Parish Council’s contractors began work on the Milton Road site in early May.  It soon became apparent that the contractors were not installing the approved drainage scheme, but were doing something else.

On 10 May 2020, WARA wrote to Cherwell DC to raise concerns that several of the planning conditions under 18/00220/F were being breached.  In particular, WARA pointed out that:

“the works that are currently being executed are beyond the scope of works that are consented within the permission5.  The only drainage works that are consented to be executed are those detailed on Drg no. 218132-001-RevA and drg no. 218132-001-RevA. This is confirmed and these drawings are referenced in the attached copy of Decision Notice for discharge of Conditions 3 and 4.”

Following an investigation, Cherwell DC wrote to the Parish Council on 19 June 2020 to confirm that two planning conditions had indeed been breached.  With regard to the drainage work, Cherwell’s letter said:

“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“.

A further update was received from Cherwell DC on 27 July 2020.  According to the Planning Officer:

“I visited the site last Wednesday to inspect the drainage and I can confirm that the approved infiltration basin has not been implemented as approved.  The current basin, which I can only assume is a temporary measure, does not meet the capacity required and the outlet going offsite is not part of the agreed scheme

I asked a drainage engineer to inspect the basin which he did on Friday.  The completed pitch drainage system is likely to concentrate surface water into the location of the drainage basin.  The current basin is not sufficient to eliminate the risk of flooding during peak rainfall periods by account of its size, however it does serve to alleviate the risk to some extent.  Essentially, while the basin is considerably undersized it is better than there being no basin at all. 

In response to the Drainage Engineer’s findings I am contacting the Parish Council to urge them to implement the approved infiltration basin in full and whilst the Council has no power to enforce a deadline until the condition 3 trigger is met I will recommend that it is completed before Autumn.”

Cherwell DC did indeed contact the Parish Council on 28 July 2020 (see below).  The Parish Council were told that there is now a greater flood risk downstream because the basin installed by the Parish Council is far smaller than the approved basin.  Again, Cherwell DC asked the Parish Council to install the correct basin before autumn.

“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”.

WARA wrote directly to the Parish Council on 16 August 2020 to point out that the approved infiltration basin has not been installed, and to ask when this would be done:

“For your reference we have attached three photographs of the outfall detail that has actually been constructed by DW Clark and two of the consented drawings detailing the design that should have been constructed and implemented in order to discharge condition no. 3 of the planning permission. It is clear from the attachments that the required infiltration basin simply has not been constructed such that the intended attenuation that should have been implemented does not exist. The problem is further exacerbated by DW Clark installing a piped connection (which is not part of the consented drainage scheme) straight in to the ditch in the adjacent field which in turn runs straight to the low lying areas of Horn Hill Road which, as you may know, was the area that was flooded in 2016 following a period of excessive rainfall.

Some of our members have been asking us, as a recognised association who represents them, what we can do to support them and ensure that the drainage associated with the construction of the pitches is implemented in accordance with the planning permission. Some of these members, who are also represented by Adderbury Parish council, live and own properties in low lying areas of the village which are at the greatest risk of flooding.

We and Adderbury Parish Council do have an obligation to communicate with our membership (APC Parishioners) and inform them what Adderbury Parish Council are doing to ensure that their properties are not at risk of flooding as a result of the development that is under construction on Land North of Milton Road, Adderbury. The fact currently is that their properties are at an increased risk of flooding until condition 3 of the planning consent has been fully discharged.

To this end could you please advise us, with timescales, when the corrected drainage scheme will be in place”.

The Parish Council responded on 21 August 2020 by stating that “The infiltration basin currently in place is acceptable to CDC”.  No timescales were provided for installation of the approved infiltration basin (see below).

By 15 October 2020, the Parish Council had still not followed Cherwell’s advice and had not installed the approved infiltration basin. 

David Peckford, the Assistant Director of Planning and Development at Cherwell District Council, sent an email to a West Adderbury resident which confirmed that CDC is not happy with the drainage scheme installed by Adderbury Parish Council.  

Mr Peckford refers in particular to the infiltration basin (drainage pond) that has been installed stating that this basin has less then 15% of the capacity of the approved basin (see below).

The attenuation pond provided so far does not conform with the required scheme. The Council’s Building Control Manager, who also provides advice on flood risk, has visited the site, observed that the swale has not so far been constructed to the consented dimensions and that a high level overflow has been installed from the swale into the adjacent ditch in the form of a short 100mm diameter pipe.

A land drainage consent would be needed for the overflow. To obtain consent, it would be necessary to demonstrate that the overflow would not cause flood risk downstream. Removing the overflow pipe would remove the requirement for land drainage consent but this would not resolve the issue of the undersized swale and the risk of overtopping. Implementing the approved surface water drainage scheme in full would be required to provide satisfactory drainage for the development once completed.

I am copying in the Parish Council so that there is clarity for all parties. May I ask the Parish Council if it could advise of its intentions regarding the completion of the drainage scheme as soon as it is able to do so. I believe it would be helpful if the residents association could also be advised.”

The above provides just a few examples of the correspondence between WARA, Cherwell DC and APC on this issue.  Despite WARA’s efforts and Cherwell’s advice, as of 8 November 2020 the Parish Council has still not implemented the approved drainage scheme.

Why does this matter?  Flooding in West Adderbury previously occurred when the field drain, into which the current infiltration basin drains, became blocked, as explained here:

In the meantime, as shown below, the small basin installed by the Parish Council is not coping at all well with heavy rain.

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