Colne Valley Viaduct
The viaduct will be 2.2 miles long and cross the Colne Valley Regional Park in Denham. It will pass over the Hillingdon Outdoor Activity Centre (HOAC), the Grand Union Canal, Savay Lake and Moorhall Road. It then crosses several lakes in the Broadwater Lake Reserve as well as the River Colne before crossing the A412 North Orbital Road. The route leaves the viaduct onto the West Hyde Embankment on its way to the Chiltern Tunnel. Denham Water-ski Club has had to build a new clubhouse on the south side of the lake.
There will be a number of construction compounds along the viaduct route. Access to these compounds will be via a temporary haul road which follows the route across the lakes on a series of jetties to the South Tunnel Portal compound and then the slip roads to the M25.