Severn Trent has completed a £1.4 million “unique flood alleviation” scheme in Gloucestershire using “innovative underground technology”.

The scheme in Slimbridge saw Severn Trent’s engineers applying “flood grout” to 600 metres of sewer pipes as part of a UK trial of the method.

Flood grouting is a method which uses two different grout materials, which are inserted into the sewers in stages.

The grout flows through the damaged sections of pipe, into the surrounding soil particles and then hardens around the sewer pipe when the two grout materials mix together.

The technique gives a “near-perfect” water tightness and seals any defects, while also stopping any groundwater from leaking into the network.

Along with construction partner NMCN, the water company renovated 1.4km of sewer pipes and also installed additional tank sewers to protect the local area from flooding.

Ian Woodward project manager at Severn Trent, said: “Slimbridge is an area which is prone to flooding and we’ve seen problems in the past where ground water has mixed with sewage.

“It was the perfect location for the trial and we renovated 1.4km of pipes in three separate phases, with 600m of those being used for the flood grouting trial.”

As well as trialling the flood grout technique, the project also involved using other traditional trenchless technologies, including sewer lining, to renew the ageing sewer pipes.

Woodward added: “The initial findings are really positive. Monitoring of both the local sewage pumping station and the ground water levels in Slimbridge is showing that the grouting has been successful in keeping ground water out of the sewers in a really vulnerable area.”

The company said that following the early findings from the work in Slimbridge, flood grouting is a method it will consider using in the future to address similar ground water infiltration problems.

Severn Trent says it will continue to monitor the effectiveness of the trial over the coming months, during which time the ground water levels will vary.

What to read next