Cherwell District Council
Planning and Development Services
Bodicote House
White Post Road
Bodicote
Banbury
OX15 4AA

	

Our ref:	WA/2011/109141/02-L01
Your ref:	10/01491/REM

Date:		11 February 2011

Dear Ms Griffiths

DISCHARGE OF CONDITION 12 OF 06/00967/OUT FOR PARCEL KM2.    
KM2 DEVELOPMENT SITE, KINGSMERE DEVELOPMENT, MIDDLETON STONEY ROAD, BICESTER, OXFORDSHIRE.       

I refer to the emails dated 21 and 31 January, 07, 08, 09 and 10 February 2011 from Brookbanks Consulting and Bovis Homes.

The emails contain:

•	Microdrainage calculations
•	Drawing BICE_5_510 Rev H, dated 31/01/11, produced by Bovis Homes

From a surface water flood risk perspective the submitted details a sufficient enough to meet the requirements of condition 12 of 06/00967/OUT. 

The Design Code states that the ‘Developer must undertake full scale permeability tests throughout the development parcel to evaluate the infiltration rates across the parcel’. This has not been carried out as part of the design of the drainage system for this parcel and the drainage design is based on the findings of the site wide ground investigation by WSP in 2007. This would normally be unacceptable, but we are willing to accept this approach for this parcel because one of the trial pits included in the WSP investigation was located on the edge of this development parcel. Ideally, there should be more than one trial pit within the parcel, but a precautionary infiltration rate has been used (significantly lower than that obtained from the relevant trial pit) to allow for variance in permeability across the parcel.
 
In accordance with the design code, the proposed drainage system will infiltrate all water within the parcel during storm events up to and including the 1 in 10 year storm event and overflow into the site wide network during larger events. The system will not flood during storm events up to and including the 1 in 100 year event with an allowance for climate change.
 
We have been made aware that there may be issues with adoption of the swale on this plot. If the swale must be omitted from the design we request to be consulted on the amended design.
 
We will expect full scale permeability tests to be carried out for other development parcels in the future.

Yours sincerely

Ms Michelle Kidd
Planning Liaison Officer

Direct dial 01491 828455
Direct fax 01491 834703
Direct e-mail michelle.kidd@environment-agency.gov.uk

cc Bovis Homes Ltd