18 Jan 2010
The Howfield to Chilham Water Main Project will carry water from extraction boreholes at Howfield to Chilham as part of a scheme to provide potable water to thousands of homes in the mid Kent area. Over 6km of 450mm pipeline is being installed for the scheme.
The route of the new pipeline took it under the Ashford to Ramsgate main railway. South East Water’s main contractor, Clancy Docwra contracted us to install two 40 metre long, 500mm ID microtunnels using Naylor Denlok clayware. The location of the works, some 40 metres from the boreholes, the railway, a high water table and fishing lakes all around the site meant that microtunnelling was the least risk method for the pipe installation.
We chose an Iseki TCC Unclemole microtunnelling machine and solids separation system to undertake the bores in mixed ground of clayey, sandy, flint gravels. We designed and constructed thrust walls and entry and exit eyes to allow for safe exit and entry into the pits. We worked from sheet piled coffer dams to a depth of 5 mtrs below the water table.
A series of three inch submersible pumps and settlement tanks were used to deal with ground water inflow into the coffer dams. Chalk was encountered under the railway tracks but the microtunnelling machine coped well and installed an average of 20 mtrs of 500mm ID Naylor Denlok clayware per shift.
The project had its share of health, safety and environmental challenges, including South East Water’s boreholes only 40 metres away, fishing lakes all around the site, the constraints of working under an operational high speed railway, a high water table and the demands of confined space working.
The existing 25” cast iron rising main carries sew...
Perco - Specialists In Trenchless Technology
