POLARIS (PUPS) was an underground experiment to observe seismic signals at depth in very hard rock.
[1][2] In addition to academic research, the observational data collected by the POLARIS system was used by the Canadian National Data Centre (CNDC) for earthquake, and nuclear explosion (see Partial Nuclear Test Ban Treaty) monitoring.
[3] The name POLARIS is an acronym for Portable Observatories for Lithospheric Analysis and Research Investigating Seismicity.
Although accessed through an active mine, the laboratory proper is maintained as a class-2000 cleanroom, with very low levels of dust and background radiation.
SNOLAB's 2070 m (6800 feet) of overburden rock provides 6010 metre water equivalent (MWE) shielding from cosmic rays, providing a low-background environment for experiments requiring high sensitivities and extremely low counting rates.