ACO Water Management’s StormBrixx system has been utilised as part of a SuDS design for exceedance at Telford Co-operative Academy. ACO worked closely with the Project Engineers to develop a multi-functional solution able to manage a 1:100 year flood event, in addition to an uplift of 30% to account for climate change – equating to around 1000m3 of surface water.
The Telford Co-operative Academy’s main building, all-weather sports field and car park form three substantial drainage elements, creating a number of challenges for Telford and Wrekin Council and the Project Contractor Shepherd Construction.
Originally it was planned to connect the surface water drainage to a culverted watercourse. However, a number of problems were identified – the site sits on clay with just 100mm of topsoil, meaning that infiltration had to be ruled out. An alternative approach was required quickly, as any delay to the build would be subject to contractual penalties of £20,000 per week.
With a clear priority focused on surface water quantity, managing water on or near the surface became a design goal, to reduce costs as well as to facilitate easy maintenance. Telford and Wrekin’s engineers turned to ACO and its StormBrixx geocellular stormwater management system was identified as central to delivering the scheme.
The solution involved connecting the drainage to the highway surface water sewer just over 400mm from the site boundary and the design needed to incorporate a number of multi-functional elements, to meet wide-ranging demands.
“The site and its location posed considerable challenges, said Gerrol Jalving, Senior Highway Engineer from Telford & Wrekin Council.
“There was a substantial drop of 3m at 200m from the receiving sewer, yet adjacent contaminated land made deep excavation undesirable. As the run-off flows exceeded a discharge limit of 5l/s, additional attenuation was also required.”
The answer was a shallow depression within the attenuation area, utilising spoil from the main contract. A topographic depression was created with a 1:15 gradient (<7%). This enabled the team to reduce the underground storage to just 175m3 of StormBrixx, meeting a design storm return period of 1:30 whilst avoiding the need for deep drilling.
The depression provides temporary ponding on the surface, with a storage capacity of 800m3, to meet the critical volume of a 1:100 year event. This area also provides an additional amenity for the local community, with a football pitch built over the top.
In addition, this exemplar approach takes into account an uplift of 30% for climate change, with surrounding fields utilised as part of the design for exceedance.
ACO’s StormBrixx system offered the project a number of benefits.
“StormBrixx can be supplied with a concrete chamber for man access and this provided a housing for submersible pumps – set to activate when the water rises above a certain level,” said Peter Bembridge from ACO.
“More importantly, the chamber provides easy man access for a thorough inspection down each of the system’s pathways. As a result, any issues such as the build up of silt or water sitting in the system can be identified and dealt with quickly and efficiently. With the academy having to take responsibility for the drainage maintenance, this was a major consideration.”