Wimbleball Dam earns 2016 ICE South West civil engineering award

Denver — The Institution of Civil Engineers (ICE) South West recently awarded England’s Wimbleball Dam Grouting Works project its Civil Engineering Project of the Year Award in the over £1 million Re-engineering category. The award celebrates the outstanding civil engineering achievement, innovation and ingenuity around the South West region.

Wimbleball Dam, a 50-meter-high concrete buttress dam constructed in 1978 on the River Haddeo, a headwater of the River Exe in Somerset, is a strategic water resource for South West Water and Wessex Water. Due to increasing leakage beneath the dam, the joint owners, South West Water and Wessex Water, turned to CH2M, to design and supervise the construction of an innovative solution to seal leaks in the dam foundation without taking the dam out of service and complying with strict environmental controls as the dam is located within a National Park. Using a 3D model of the dam body, foundations and drainage, CH2M identified a solution to construct a new grout curtain from the downstream side of the dam to ensure the community’s water supply was not interrupted.

The grout mix was designed specially to cope with the challenging site conditions and included ultrafine cement, hyper-plasticisers, silica fume and accelerators. The techniques applied allowed a new grout curtain to be constructed with lower permeability, increased durability and reduced quantities of grout compared to previous grouting campaigns — resulting in major cost savings. Leakage has been reduced by approximately 70 percent to the lowest recorded rate since construction of the dam.

“The Wimbleball Dam Grouting Works project was highly successful in reducing leakage within difficult and challenging ground conditions,” said Peter Nicol, CH2M Global Water Business Group President. “We are proud that the team’s accomplishments in overcoming a significant technical challenge to ensure the long-term safety of the dam, with minimal impact to the surrounding National Park and water supply, were recognized with this prestigious award.”