  The 2021 particle physics community study, known as "Snowmass 2021", has
brought together particle physicists around the world to create a unified
vision for the field over the next decade. One of the areas of focus is the
Underground Facilities (UF) frontier, which addresses underground
infrastructure and the scientific programs and goals of underground-based
experiments. To this effect, the UF Supporting Capabilities topical group
created two surveys for the community to identify potential gaps between the
supporting capabilities of facilities and those needed by current and future
experiments. Capabilities surveyed are discussed in this report and include
underground cleanroom space size and specifications, radon-reduced space needs
and availability, the assay need and other underground space needs as well
timeline for future experiments. Results indicate that future, larger
experiments will increasingly require underground assembly in larger, cleaner
cleanrooms, often with better radon-reduction systems and increased monitoring
capability for ambient contaminants. Most assay needs may be met by existing
worldwide capabilities with organized cooperation between facilities and
experiments. Improved assay sensitivity is needed for assays of bulk and
surface radioactivity for some materials for some experiments, and would be
highly beneficial for radon emanation.
