Poplar Farm, Grantham - Surface Water Strategy

THE CHALLENGE

Grantham was awarded Growth Point Status in 2006 following a successful bid by South Kesteven District Council and Lincolnshire County Council for additional funding from the Department of Communities and Local Government. The Poplar Farm site represents about half of the North-West Quadrant within SKDC’s Local Plan, an area allocated to deliver approximately 3,750 new homes as part of the wider Growth Point objectives. Some initial development had taken place at the end of the 1990s but further progress had stalled.

The Poplar Farm site is intended to provide up to 1,800 new homes, a local centre and land for a new primary school.

SYSTRA’S ROLE

SYSTRA provided infrastructure investigation and design services to the landowners, commencing in 2007 with work on an outline planning application and corresponding technical documents. This included investigating the existing land drainage arrangements and identifying a suitable surface drainage approach to serve the site in accordance with requirements of the relevant drainage authorities. The site spreads across a hillside and the ground is generally clayey in nature with a widespread agricultural field drain network. The ground conditions would not support infiltration drainage as an effective site-wide solution and an alternative drainage approach would be needed.

SYSTRA consulted extensively with SKDC, LCC, the Environment Agency and with the local Internal Drainage Board who controlled the stream draining the site. A large attenuation lagoon had been formed as part of the earlier development phase but changes to drainage performance standards and to the development scale meant that this was no longer sufficient for the whole site. SYSTRA devised a series of additional attenuation features to provide additional capacity that would allow a site-wide storm drainage system to serve the development parcels. The strategy was presented as part of the Flood Risk Assessment and Drainage Strategy reports and outline planning permission was granted in 2009.