One of the first Sustainable Drainage Systems in the UK to demonstrate a full management train for development runoff — and still going strong despite minimal maintenance. This SuDS landscape combines beautiful wildlife habitat zones with more formal water features to create a peaceful oasis for weary travellers yet at the same time deal with polluted runoff from car & lorry parks and a fuel filling station.
the client: Welcome Break
site area: 34 Hectares
return period: 1 in 25 storm return period
discharge destination: Hopwood Stream
discharge flow rate: 5L/sec/Ha
techniques used: Open wetland systems are protected by pretreatment features including filter strips, treatment trenches or separators to reduce pollution or silt loading and prevent catastrophic damage in the event of spillage.
Robert Bray Associates were commissioned to pioneer a SuDS scheme that would serve this busy motorway service area. Hopwood Motorway Service Area is located on the M42 motorway near Bromsgrove and includes amenity services, car parks, coach parks, and a fuel filling station. However the site was also enclosed in a series of planted banks and falls northwards to the Hopwood Stream, which eventually flows to the River Arrow.
Although designed before the publication of formal SuDS design guidance, this system demonstrates the use of the SuDS ‘Management Train’, treatment stages and the use of SuDS to provide both amenity and wildlife benefits.
The performance of the site was extensively monitored during the first year of operation showing that all expected benefits were delivered, plus some that were unexpected such as minimal silt accumulation and low maintenance costs. The SuDS management costs for the whole system are now less than the cost of managing one oil interceptor.
The site continues to provide effective management of runoff from large areas of hard surfaces, delivering a controlled flow of clean water to the Hopwood Stream at modest cost over a decade after installation.
The client, Welcome Break, required an affordable system that provided an attractive setting and added amenity to the service area. We worked closely with the client and their design and construction teams to introduce what was, at that time, a very new approach to stormwater management. The continuing high performance of this scheme after 15 years, despite minimal maintenance, is testament to our belief in delivering systems that are easy to understand and maintain.
As well as serving a valuable flood and water quality function, the landscape and Sustainable Drainage System are designed to provide an attractive environment for the service area with SuDS features providing visual amenity as well as delivering valuable wildlife habitat.
There are two main sub-catchments : the HGV park and the rest of the site. This area is subdivided again into fuel & coach parking, car parking and amenity areas. Each part of the site collects runoff in different ways but treats the first 10mm ‘first flush’ in stone treatment trenches, a grit/oil separator to the coach park and filling station, whilst roof water flows directly to a feature pond adjacent to the amenity building food hall and external decked seating area.
Water flow is conveyed at the surface wherever possible to balancing ponds that discharge through flow controls to a small stilling area, before clean water flows into the adjacent stream at a greenfield rate of runoff (5L/sec/ha). Areas considered to pose a pollution risk to the environment have used the management train concept in full to ensure good water quality and to deal with unforeseen spillage events. The HGV park and the fuel filling area, coach park and service yard pose a serious pollution risk and have an extended management train. The car park and amenity building roof water were considered less likely to cause pollution and therefore have progressively shorter treatment systems although the concept is applied generally to provide insurance against unforeseen spillage events.
Runoff from the HGV park is directed to a tributary of the Hopwood Stream via the Wildlife Reserve to enhance a pre-existing wetland and help sustain base flow in the watercourse. Open wetland systems are protected by pretreatment features, including filter strips, treatment trenches and separators, to reduce pollution or silt loading and prevent catastrophic damage in the event of spillage.