Failure of an island reservoir would have a catastrophic and life-threating impact on a village’s school, businesses and residents.

The planning committee this week approved vital safety improvement works (25/91205/B) at Kionslieu reservoir outside Foxdale.

An inspection report carried out in 2018 concluded that the reservoir in its current condition has an unacceptably high risk of failure, posing a threat to life in the communities downstream, with Foxdale village most at risk.

It recommended that either significant improvement works be carried out to make the reservoir safe, or that the reservoir be removed.

While the latter would completely remove the risk, significant additional drainage improvements and flood mitigation measures would be needed to address the increased flood risk, a subsequent feasibility study concluded.

Removal of the reservoir would also lead to the loss of an important wildlife habitat.

Consultant reservoir engineer Jon Holland told the planning committee that the failure of the reservoir would pose a threat to life, and it could have a ‘catastrophic impact on homes, business and the primary school in the village’.

He said there was also the risk of lead and zinc contamination from old mine workings.

Built in the early to mid 19th century for the zinc and lead mining industry, Kionslieu no longer functions as an operational reservoir and now acts purely as an amenity lake.

The approved works will improve dam safety by reshaping the banks, installing new pipes and an overflow system. They also include works to improve access on the on Lhoobs and East Foxdale Roads and restoring a footpath.

Once complete, the improvements will allow water levels to be increased after they were lowered as a safety measure in 2019.

With planning consent secured, work is expected to begin in summer 2027.

Planning committee chair Rob Callister said the scheme was ‘desperately needed’ but he and fellow committee member Sam Skelton expressed concern at the time it had taken.

Matthew Warren was the only one to vote against. He questioned the need to retain the reservoir and increase the water level.

‘Are we over-engineering something that could be done another way? he asked.

The upgrade work could be complicated by the potential presence of historic explosive devices.

The area around the reservoir and the reservoir itself were used historically for military training exercises including live-fire amphibious assault training during the Second World War.

A mitigation strategy has been prepared which involves carrying out surveys before work begins with any sediment removed being searched by an Explosive Ordnance Clearance (EOC) engineer.

Recommending DEFA’s application be approved, the planning officer concluded: ‘It is clear that there is overriding need for the works proposed on grounds of public safety. There is no reasonable and acceptable alternative.’

DEFA Minister Clare Barber said securing planning consent was a ‘significant milestone for the project’.

She said: The works will secure the future of Kionslieu reservoir for generations to come, strengthening dam stability, improving flood management, and protecting its environmental and recreational value.’