Underwater breaking at St Germans pumping station
13 October 2011
UK contractor GBM Demolition Services used two 3,800 kg (8,360 lb) Sandvik BR4511 breakers to remove underwater elements of the St Germans pumping station at Wiggenhall St Germans in Norfolk, UK. Originally, the plan was to upgrade and refurbish the station in 2010, but it became clear that the high cost of servicing the 64 year old pumps would not be economically viable. The decision was therefore taken to replace the station - a vital part of the water control on the Great River Ouse - with a new £40 million (US$63 million) facility.
The Lough, Lincolnshire, based company is using the breakers, mounted on a Volvo EC700 and a Komatsu PC450, to remove reinforced concrete at the side of the old station's 2 m (6.6 ft) thick reinforced concrete sluiceways, with the Komatsu also wading into the lagoon to demolish the 2m thick concrete slipways.
Main contractor Costain had used another contractor to demolish the station structures that were above water but selected GBM as the specialist contractor to carry out the underwater part of the demolition work.
According to GBM's contracts manager Alan Kime: ""It was impossible to dam the water supply so we were forced to provide a demolition solution that would work under water. Working under water with a breaker presents all sorts of problems."
"We are using special grease for the breakers and all the hydraulic oil has to be bio-degradable for a start. But the biggest problem is ensuring that water does not enter the hydraulic system through the breaker. This can only be done by operating the breaker with a constant 5 bar pneumatic air supply supplied by mobile compressors, and connected to an air input point designed for underwater applications. But there is always the risk that if the air supply fails, then water will enter the system within seconds and destroy the hydraulics. Sandvik have installed safety cut-off systems for the breakers that sound warnings and isolate the breakers long before any damage could be done. It is a system that clearly works, and allows us to operate the breakers under water with confidence."
The new station has six state-of-the-art pumps capable of moving 100 cubic metres of water per second, and on one test to lower the levels, 150 million litres of water was pumped during a single morning.
