RAB Consultants undertook a Flood Risk Assessment for the proposed construction of a Bedford Academy on the site of the former John Bunyan School, for Bedford Borough Council. A conceptual drainage design was required due to the size and scale of the proposed development.
The school was to be located on high ground with the northern half of the site sloping towards a road and the southern half sloping to a water course. Due to the arrangement of the school it was not possible to drain the whole site to either the north or south without pumping water over the high point. For this reason the surface water drainage design effectively divided the site into two, as the ground would naturally drain. The use of soakaways was not suitable due to the size of the impermeable areas, the available space and the proximity of the river.
The northern aspect, which constituted mainly car parking, was designed with pervious surfaces to enable infiltration and an attenuation system linked to the public sewer system to manage any remaining water. The attenuation system constricted the flow entering the surface water sewer system in line with the requirements of the local water authority.
The southern aspect drained the main building and sports courts. The sports courts were designed with pervious surfaces. The main buildings drained to an attenuation pond along with any excess water from the sports courts. Runoff was conveyed by a swale with a fore-bay cascading into the main pond to promote water purification.
Our assessment formed part of a business case applying for funding under the governments “Building Schools for the Future” programme.
Planning permission was granted and the school was constructed ready for the arrival of the first group of students in 2012.