A listed Victorian dam in west Yorkshire could fail catastrophically if opponents block plans for a replacement spillway, engineers warned this week.
Experts fear that unless work is carried out to replace the Grade II listed dam spillway at Butterley reservoir, there is risk of a catastrophic failure similar to that seen at Ulley dam during the 2007 floods.
“A big flooding event will cause Butterley dam to fail,” warned ICE panel engineer responsible for the repair scheme Andy Hughes.
However, despite these safety warnings, local action group Save Butterley Spillway remains opposed to owner Yorkshire Water’s plans. It claims the water company’s replacement plan has “sidelined” the structure’s historical significance.
But engineers argued that repairs to the spillway were a vital safety matter.
They pointed to the fact that the Butterley spillway is similar to that at Ulley dam near Rotherham, which suffered a near catastrophic collapse following heavy rainfall in 2007 (NCE 5 July 2007). Both dams have spillways across the downstream face.
Consulting/contracting joint venture Mott McDonald Bentley has been commissioned to design a replacement to the existing 91m long, up 13m wide spillway.
The new design is due to be submitted to local authority Kirklees Council “imminently”. It incorporates the existing masonry wall but has a more robust concrete channel. Reusing the masonry, Yorkshire Water said, added £1.2M to the £6M total cost.
Save Butterley Spillway has rejected these plans and vows to oppose the planning application. It has demanded that Yorkshire Water puts forward a scheme that is more sympathetic to the structure’s historic status.
“Yorkshire Water has completely sidelined the status of the spillway as a listed building and given precedence to the Reservoirs Act 1975,” said Save Butterley Spillway member Diane Ellis.
“Both the Reservoirs Act and the listed buildings legislation should be given equal weight in designing a scheme and a scheme which satisfies both pieces of legislation is possible.”
Ellis said Yorkshire Water’s plan to remove the masnonry and replace it with a concrete spillway was not preservation. She added Yorkshire Water “does not have a clue when it comes to understanding our heritage”.
Arup associate director Peter Kelham, an expert in the structural design of dams and part of the team that worked on repairs to Ulley dam, said that while he understood the concerns raised by local opponents, safety should be paramount in decisions about dam maintenance.
“I am sympathetic to the arguments but there are consequences if the work is not done,” he said.
Hughes agreed and pointed out that the existing masonry spillway was unable to withstand a major flood as it was not tied into the embankment and had already suffered serious damage.
“Flooding in 2002 ripped the spillway to bits,” said Hughes.
Butterley Reservoir is 13km south west of Huddersfield, sitting on the border with the Peak District. It is the part of a four reservoir system and the iconic spillway - built between 1891 and 1906 -is listed in the Victorian Society’s 10 most endangered buildings in England and Wales.
Yorkshire Water plans to replace the spillway so the dam can comply with the Reservoir Act 1975. The Act says that a Department for Environment, Food and Rural Affairs must appoint an independent panel engineer to inspect the site every 10 years and to recommend improvements where necessary.
These recommendations must be implemented by law and at Butterley Hughes recommended that the masonry spillway be replaced by a concrete one.
He warned that unless these repairs were carried out, as the panel engineer responsible, he would have to order Yorkshire Water to cut the capacity of Butterley Reservoir, along with three other reservoirs upstream.
The Environment Agency has been more vigilant towards dam safety since the Ulley dam near Sheffield came close to collapse when a similar masonry spillway failed after heavy flooding in 2007.
This event prompted it to issue new masonry spillway assessment guidance in an attempt to better protect infrastructure.
With this in mind, Hughes questioned the appropriateness of applying listed building status to critical infrastructure.
“I do not think listed status should apply to any part of the reservoir,” he said.