Forestry Commission Wales engineers carried out safety work on a reservoir – using cobbles reclaimed from the streets of Bangor and Caernarfon.
They designed a new spillway at Llyn Goddionduon Reservoir in Gwydyr Forest after concerns about the dam were raised by Environment Agency Wales.
The reservoir supplies water to the Army training camp in Capel Curig, where soldiers and cadets from all over Britain and Germany come to take part in exercises over the mountains, forests and rivers of Snowdonia.
However, a survey by the Environment Agency following changes to reservoir safety legislation raised fears that the dam and spillway might not be able to cope with the volume of water in the event of extreme weather.
FC Wales and the Ministry of Defence have joint responsibility for the reservoir, which is a Special Area of Conservation – the highest environmental designation in Europe.
FC Wales civil engineers Peter Oxbury and Rory O’Donnell set about re-designing the dam to make the reservoir safe and retain its sensitive characteristics.
Their solution was to build a new dam comprising a stone-filled basket called a gabion, sealed with a layer of clay, beneath a spillway made from recycled cobbles.
Gavin Queen, FC Wales country civil engineer, said, “The stones were granite cobbles which were originally used to pave the streets of Bangor and Caernarfon before they were all replaced by tarmac.
“The sensitive nature of the site meant the water level had to be maintained and we had to draw on all our professionalism to complete this work to such a high standard.”
As well as making the site safe, engineers also built an access track to the reservoir, enabling the public to enjoy the area.
The work took two weeks to complete and was carried out by north Wales civil engineering contractor Mulcair.
