Type of works: landmark highway drainage scheme delivers sustainable benefits for local authority.
A new highway drainage scheme in Lancashire is believed to be the first SUDS (Sustainable Urban Drainage System) in the country to be fully adopted by a local authority. Installed on the new 2km link road between the former Royal Ordnance munitions works in Chorley and the main A49, the scheme integrates the benefits of award winning KerbDrain® system, developed by drainage specialist, ACO Technologies, to improve installation time, drainage performance and overall cost effectiveness.
The 395 acre former Royal Ordnance munitions works is one of the largest brown field development sites in the country. Acquired by developers Redrow and Barratt in winter 2000, plans were granted to transform site into an environmentally sustainable urban village with an investment of over £400m. Called Buckshaw Village, the first phase of industrial units and homes together with the new link road is now complete.
The adopted drainage design introduces swales on both sides of the carriageway. Each has a depth of between 400 and 800mm and an effective width of 2.5m. The profile provides the required attenuation and groundwater recharge characteristics to cope with the surface run-off from a 100 year storm. Seeded with a hard-wearing grass, the velocity of the water is minimised and the primary filtration improved within the swale by maintaining a cut length of 50mm.
A critical element of the design is the method used to control the flow of run-off into the swale, says Steve Openshaw, Technical Manager at Redrow. We needed a system that would be easy to install and maintain, minimise visual impact and not require any additional excavation within the proposed swale. It would also need to allow surface water to return to ground as close to the point at which it fell a vital criteria for SUDS.
ACOs KerbDrain® system a versatile combined kerb and drainage channel manufactured in a single unit from polymer resin concrete was selected to provide this vital link between carriageway and swale. The KerbDrain® units have the same profile as an HB1 kerb stone but are 60% lighter and have 50% greater impact resistance than a standard kerb. Twin inlets on the front face provide continuous surface drainage along its entire length and on the back face two punch out sections allow outlets to be positioned at any point along an installed run. A further advantage for the Buckshaw Village link road came from the system being manufactured in two sizes. The smaller KerbDrain® Kompact unit has the same above ground profile but a reduced overall height of just 305mm. Originally developed to ease installation around utility services, the effective raised height of the rear outlets meant that the depth of the swale could be reduced minimising excavation, reducing visual impact and speeding up installation.
The flexibility of KerbDrain® meant that we could adapt the outlet configurations easily to suit the landscaping, place rodding access points to ease maintenance and install the overall system far quicker and far more cost effectively than we had anticipated all factors that have helped in winning adoption of the final scheme, says Steve Openshaw. This access road is just the first of many sustainable development schemes that will be introduced across the site to create a completely harmonised residential, commercial and leisure environment.