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Gwydir Reservoirs: The safe management of high-risk reservoirs

Event organised by ICE

16 September 2021
19:30 - 20:30 BST (GMT+1)

This event has now ended

You can catch-up on details or any broadcast and downloads here.


When four legacy-mining dams in Snowdonia were found in urgent need of repair, Natural Resources Wales (NRW) had a legal duty to make them safe or suffer enforcement action. Reservoir failure posed a risk to life or serious injury for people downstream, with criminal, civil and reputational consequences for NRW.

The Gwydir Reservoirs’ scale and location required an innovative approach; employing restorative, environmentally sensitive engineering to upgrade 150-year-old embankments offering flood attenuation whilst constructing new spillways to control flows and reduce risk to life downstream.

NRW anticipated challenges working across remote sites, in one of the highest and wettest areas in Wales, with difficult ground conditions and undocumented mine workings. NRW couldn’t predict a main contractor financial collapse and later Covid19 pandemic, which left NRW facing an unprecedented battle to meet strict regulator deadlines.

The presenters will share their experience on the multi-site project, reflecting on the legislative requirements, the works carried out on the water-retaining structures and how NRW achieved high quality and safety standards during construction whilst temporarily placing the reservoirs at greatest risk of failure. It shall conclude on how such lessons have fed into NRW’s wider reservoir portfolio and the ongoing work to maintain excellence and combat the challenges in the 21st century.

This event is co-badged with the Chartered Institution of Water and Environmental Management (CIWEM) and with the British Dam Society (BDS).

CIWEM logo
British Dam Society logo

For more information please contact:

Felicity White