Placing 25 t siphon pipes on a dam face

How we placed three 25 t siphon pipes on a reservoir embankment that no crane could reach and that could not carry heavy lifting loads.

Bewl Water, the largest reservoir in the South East of England, needed a new emergency drawdown system as part of Southern Water’s dam safety upgrade, delivered with CMDP+. The system is three large steel siphon pipes, each around 25 t, that can lower the reservoir quickly if heavy rainfall ever threatens the dam.

A crane could lift the pipes into the water but could not reach their final position on the embankment, and the embankment itself could not carry heavy lifting loads. Working with GPS MACS, we designed the temporary works for that final stage. Each pipe was floated to the site, drawn up the embankment on a rail-guided trolley and set by a gantry frame at the crest, keeping the load off the dam and holding alignment to within a millimetre.

The system worked whatever the water level on the day, travelled on standard trailers and was assembled on site. The new drawdown system lets the operator lower the reservoir by up to 5 m in five days.