Stormwater storage is built in
The construction of a new hall of residence at The University of Exeter has incorporated an innovative and space-saving, stormwater storage solution, using Hydro Stormbloc within the foundations of the building.
UPP are delivering the Birks Hall development as part of a £275 million investment programme currently being undertaken by the University of Exeter at its Streatham Campus. By designing a storage tank using Hydro’s Stormbloc modular storage within the foundation structure, consultant engineers Airey & Coles, enabled the redeveloped site to meet strict sustainable drainage requirements.
In line with UPP’s sustainability goals for the development, the Stormbloc was designed to mimic a natural storage pond feature as part of the building construction.
Meeting the challenge
“The challenge was complex,” points out an Airey and Coles spokesman for the project. “The reconstruction of the 3.6 hectare site to create a modern residential hall for 360 students meant runoff from an impervious surface area of 12,800sq m had to be attenuated. The planning requirements were for a maximum 16l/s discharge to the storm sewer, to meet a 100 year event target plus 30% increase to accommodate climate change.”
Additional site constraints were the adjacent arboretum, with numerous established rare species of tree, which could not be disturbed by construction or alteration in surface water drainage patterns.
“The only free space which could economically be used was within the Block H foundations itself,” he continued. “It took some lateral thinking to mimic a natural storage pond feature as part of the building construction, but the modular configuration of the Stormbloc made it quite easy to install.”
The new building is supported on a concrete capping beam over contiguous pile foundations. Additionally, within the outer foundation piles, there are several concrete columns providing secondary support to internal construction.
“Using 3D computer aided design we were able to plan the detailed construction of the Stormbloc around the columns, and even adjust the column locations where required,” he added. “Stormbloc also features an inspection chamber, sited on the perimeter of the main tank, which will allow future access through the tank for maintenance and inspection.”
The total size of the attenuation tank is 24.8m long, 10.4m wide and 1.6m high, providing over 400m³ of storage and comprising 798 full size and 399 half size Stormbloc units. The discharge is via a 159mm Hydro-Brake Vortex Flow Control device.