A27 Chichester Drainage Scheme - BRE Group
A27 Chichester drainage scheme achieves BREEAM Infrastructure rating of Excellent
Overview
The works on the A27 Chichester Bypass are on a stretch of two-lane dual carriageway with roundabout junctions. This scheme reduced waste by incorporating geocelluar units for soakaways, reducing the need for trench excavation and reducing waste from cut and fill. Trench-less technology also reduced the need for excavation (and therefore waste) during the installation of the link to the pumping station at Whyke Roundabout. |
About National Highways
National Highways, formerly Highways England, manage and improve England’s motorways and major A roads.
Background
The works are located on the A27 Chichester Bypass between the A259 Fishbourne Road roundabout and the A285 Portisfield Way roundabout. The A27 in this location consists of an all purpose two-lane dual carriageway with roundabout junctions except for the B2144 Oving Road which is a signal junction.
Challenges
The works were carried out to renew the existing drainage linear soakaways and bring them back to full operation. This was to help relieve the issue of recurrent flooding along the stretch of road. The existing drainage is by drainage channels to short lengths of carrier drains to linear soakaways. The works also included the construction of a pumping station and the repair of category 3-5 defects following surveys in 2010.
Benefits
Energy Assessment Results: LifeCYCLE assessment identified the following savings.
The majority of the additional carbon in the traditional soakaway is within the concrete drainage pipes that are required, which accounts for the large difference. Over 1,840m of concrete piping was needed, which accounted for 83% of its total capital carbon for the soakaway.
The difference between the Standard total carbon in 2012 to the Geocellular total carbon in 2013 and 2015 is the result of the change to the design and as it evolved the associated carbon was reduced still further.
When comparing the Geocellular total carbon at inception with the geocellular at construction we see that there was an overall percentage drop of 4%. This equates to 17.6 tonnes CO2e. This shows that efforts were made to reduce the total carbon by reducing the construction materials required.
The basic lifecycle analysis for the Geocellular block design indicated that 53% of the carbon emitted was during the initial works over a 50 year life span and it was found that 22% carbon saving could be achieved with the geocellular blocks design.