Case Studies

Drainage and Infrastructure, Distillery Lane, Colchester

Infrastructure

CLIENT: Barratt East Counties

Tamdown were awarded this contract by Barratt Eastern Counties to construct residential housing and flats on the site of a former Victorian Laundry. The site is adjacent to a large confined lake, which had been used to feed the laundry works. The contract was secured on a negotiated basis and the works comprised the construction of 200 houses and some 100 flats on pile and ground beam foundations. The works also included three undercroft car parks with associated road and sewer infrastructure works, Section 278 Works, and all associated external works. Demolition works were carried out under a separate contract.

The ground conditions and in particular the high water table associated with the lake coupled with the requirement for a deep sewer system (up to 7m deep), posed a particular design and construction challenge. 

The restrictions imposed on surface water discharge to the nearby River Colne resulted in the need for a substantial on-site surface water retention system. A vessel of 140,000 litre capacity was therefore designed for incorporation into the works. This was achieved by installing a 25 x 6 x 5m deep temporary sheet piled cofferdam, incorporating one level of walings, with the base concrete acting as a second prop. Two high capacity pumps and a 300mm rising main (to suit a flow rate of 112 litres per second) were installed to discharge the stored water back to the existing lake, as a permanent solution.

Additional challenges included maintaining access and services to an existing occupied retained property within the site, surface and groundwater management, maintaining the existing main sewer system across the site and the excavation and removal of contaminated material within the existing ground.