Extensive flooding was occurring prior to works downstream of the hospital. The project needed to reduce both total and peak flows. A multi-stage sustainable water treatment system was proposed, combining a number of techniques such as porous asphalt, swales, French drains and attenuation basins.
The site combined the main boulevard for the hospital and terminal for the London Bus Company with SMA as well as porous asphalt for the large car park.
The final pavement solution was specified as 35mm of 10mm Drainasphalt laid on 80mm of 20mm Open Binder. The solution allowed for the effective drainage of surface water at source and was also suitable for worse case storm water scenarios.
Hillingdon NHS Managers were pleased with the project having provided a leading example of sustainable low impact civil design in the UK. When commenting on the performance of the Drainasphalt used, Hillingdon NHS said, “I don’t know why this is not done everywhere”.
A big benefit of using porous asphalt for the Trust was that it essentially eliminated ponding and therefore slipping hazards around cars.
Day & England Stevenson Marsh
Hillingdon NHS Trust
- Flood mitigation surfacing solution
- High quality material meeting specific requirements
- 4050m2 of porous Drainasphalt car park material supplied
- Drainasphalt supplied with Bardon Hill aggregates at a PSV of 60
- Asphalt mixed and delivered at between 160 and 180oC.
We worked with Aggregate Industries to fine tune the specification so everyone was happy that the balance between cost and strength had been achieved.