The state of a reservoir could lead to flooding and a risk of life if it is not upgraded.

Kionslieu Reservoir, near Foxdale, has been around for nearly 200 years but work needs to be carried out to ensure it does not breach and flood homes in the area.

Following a formal inspection carried out by experts in 2017, the Department of Environment, Food and Agriculture (DEFA) was left with a stark choice to either decommission and get rid of the reservoir or upgrade it.

DEFA has now submitted a planning application to carry out the upgrade work but it could be hampered by unexploded devices from the Second World War.

In the planning statement DEFA says: ‘The Victorian-era reservoir has served the local community for nearly 200 years. However, recent inspections have shown that its structures need bringing up to modern standards.

‘The proposed works will improve dam safety by reshaping the banks, installing new pipes and an overflow system and restoring the public footpath. Once complete, the improvements would allow water levels to be safely increased.’

The work is expected to begin in summer 2027, subject to planning approval.

The planning statement continued: ‘Inspections of the reservoir carried out in 2017 and in 2023 have identified significant shortcomings in the overflow arrangements for the reservoir and the condition of the two dams that impound the reservoir.

‘Following stakeholder consultation, it has been concluded that the reservoir should be retained, returning it to its original form, with the necessary improvement works carried out.

‘The condition of the reservoir at present is such that it cannot continue to function without significant risk of flood and contamination spread.

‘The potential damage to downstream property and the prevailing risk to life is considered to represent overriding national need in this case which can only be addressed by either de-commissioning (removing) the reservoir or carrying out the necessary remedial and improvement works.’

The proposed retain scheme will return the reservoir, currently at a temporarily reduced water level, to its original form. The work will involve strengthening or building new embankments and pipe work.

But the work will be complicated by the potential presence of historic explosive devices.

The planning statement says: ‘It is known that the area around the reservoir and the reservoir itself have been used historically for military training exercises.

‘A report [from December 2022] confirmed that the site had been used for live-fire amphibious assault training during World War II, but had not been used for such activities since.’

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.

The planning statement concluded by saying: ‘The reservoir is in a poor condition and presents a significant risk in terms of reservoir failure and the potential for inundation flooding to occur downstream. Properties within Foxdale village are most at risk.

‘Significant improvement works will help to ensure the long-term integrity of the impounding embankments, thereby assuring the safety of people and property downstream of the site by minimising the risk of reservoir failure.’

The application will be considered by planners in due course.