The Underground Research Laboratory was a test site for deep geological repository of nuclear waste operated by Atomic Energy of Canada Limited's (AECL's) Whiteshell Laboratories near Lac du Bonnet in Manitoba, Canada. The site was built inside a large granite batholith, typical of the Canadian Shield. The site was selected in 1980, construction began in 1982 and it opened in 1985. No radioactive material was stored at the site, it was used purely for measurements of water exchange, rock movement, and other issues that would affect the safety of such materials. The site was also used by a variety of international users. As part of the wider wind-down of AECL activities, the decision was made to close the URL in 2003. Cleanup work began in 2006 and completed in 2010. The site continues to host a single international experiment measuring water leakage through a massive clay plug.