The Civic Centre at Parkside is a public realm scheme including a new Civic Centre, Civic Hall and Library. A fully infiltrating SuDS system has been implemented using permeable surface to manage the rainfall on the site, with overflow and exceedance routes to cater for exceptional rainfall events. All rainwater storage is at the surface within landscape features or underground within voided stone areas
Generally around the site rainwater from roofs is collected either into a sett/ribbed channel or flows directly into a permeable block paving surface where it infiltrates and is collected in pipes within a voided stone sub base. Control structures are located at each of the permeable block car park areas and to the perimeter of the site at the outlets of swales. These prevent unrestricted flow from the system after heavy rainfall and maximise the storage capacity of each feature.
Underdrained swales both hold and clean water from car parks and roofs before the water continues to an existing sewer through a series of infiltration trenches or pipes.
Planted raingardens within the access court take road run-off and contain the water on a day-to-day basis. In exceptional rainfall, the raingardens will overflow to an existing combined sewer through underground pipes.
The whole central courtyard and parking area acts as an infiltration zone, using permeable surfaces, raingardens and channels. At its heart a lower area forms both a social space but also doubles up as a detention basin, holding water in extreme weather events. The key focal point to this space is a solar powered cascade and water rill. This collects water from the surrounding roofs and takes it over a cascade, through a rill and connects to an overflow.
From the new library, rainwater is collected in sett channels and then flows into infiltration planters. Water will then infiltrate into the voided stone base layer
The SuDs design at Parkside contributes to the distinctiveness of the development in key places. The main buildings are accessed through a central courtyard, which forms the focus of the site, with a series of smaller spaces at the entrances to the library and other buildings.
In the courtyard, the solar-powered cascade, rill and outlet pool provide a feature attraction in keeping with the style of the original building, while planting beds and raingarden planters decorate the perimeter. The drainage system that feeds the cascade, combined with the permeable paving, keeps the surface of the social courtyard space free from puddles in wet weather whilst providing a visual and audible highlight, once the sun comes out!!
Infiltration planters to the library entrance provide a visual softening of the block paving at the entrance to the new public library. Sett channels at the library entrance and in the central courtyard provide visual and textural contrast against the paved surface.
The landscape features of the new development are fully dependent on the design of the suds throughout the site, rather than the suds being an afterthought or in conflict with the landscape design.
The design objectives for the suds installation were: to drain surface water away from hard surfaces; to minimise fast runoff to the town sewers during heavy rainfall; and to eliminate runoff of polluted groundwater to watercourses. Each of the five SuDs areas has its own landscape character and functions as an individual drainage sub-catchment
The Car Park: PAH pollution is a concern here. We addressed this by constructing parking bays in geomembrane-lined permeable block paving, thus eliminating runoff of polluted surface water to neighbouring ground and water.
The ‘Triangle’: raingarden planters installed here mitigate the impact of peak flows by collecting the first flush of runoff from the hard surface.
The Civic Court: The cascade receives roofwater via rainwater pipes, and the pool flows out to one of two buried perforated pipes. These pipes collect water that has infiltrated via the permeable paving, and feed into a solid pipe running to a final infiltration point - an underdrained swale. In exceptional rainfall events, overflow from this courtyard zone will run to another area of permeable block paving and then to a tree-lined underdrained swale and infiltration trench.
The Library Entrance: Rainwater pipes pass roofwater into sett channels feeding infiltration planters in the entrance area, while direct rainfall to the ground passes through the permeable block surface to the subsoil. These planters are also set 100mm below surface levels, increasing their storage and attenuation capacity.
The Historic Frontage to the Building: The frontage is preserved, with its mature trees and simple driveway, and existing drainage to the sewer is retained.
Location : Bromsgrove, Worcestershire
Return period Attenuated : 1 in 100y (+30%)
Techniques: Planted raingardens, hardscape detention basins which form social space, underdrained swales, infiltration trench, permeable paving, tarmac areas with voided stone sub base to allow through flow, ribbed and sett channels, short underground connecting pipes, overground paved exceedance routes to convey flows between infiltration structures, water rill and cascade.
Discharge destination : All water dealt with and contained on site. Water overflows in exceptional events to existing combined sewers
Discharge flow rate : 0 at less than the 1 in 48y event
Client : Worcestershire CC & Bromsgrove DC