6.7. Site characterization should comprise both surface based investigations and underground investigations. The latter may be undertaken as a precursor to commencing construction of the disposal facility, whereby characterization and in situ experiments could be carried out in an underground laboratory or rock characterization facility at the potential disposal site. Alternatively, underground investigations might be carried out as an integral and early part of disposal construction, in which case authorization for construction (but not operation) is based only on results from surface based investigations. Surface based investigations should include, but not be limited to, remote sensing (e.g. satellite monitoring, aerial photography, seismic surveillance) and airborne surveys, geological and geochemical mapping and sampling of outcropping strata, surface based and borehole geophysical investigations, borehole sampling, logging and hydrogeological testing.