Caltech Submillimeter Observatory (CSO) Decommissioning Draft Environmental Assessment Released

Caltech, in cooperation with the Hawai‘i Department of Land and Natural Resources (DLNR), has released its Draft Environmental Assessment and Anticipated Finding of No Significant Impact (DEA/AFONSI) as part of the planning effort required prior to decommissioning the Caltech Submillimeter Observatory (CSO) located near the summit of Maunakea in Hawaii.

CSO, which for nearly three decades operated as one of the world's premier facilities for astronomical research and instrumentation development at submillimeter wavelengths before its instruments were removed in 2015, is one of the first observatories on the mountain to undertake the decommissioning process. The CSO was used by researchers, including more than 200 students, to open a new submillimeter window on the universe.

Upon completion of the regulatory process, Caltech plans to begin removing the observatory and restoring the site, with the deconstruction and restoration beginning summer 2022. CSO will be one of the first observatories removed under the 2010 Decommissioning Plan for Maunakea Observatories.

The DEA, prepared by Caltech's consultant, Planning Solutions, Inc., addresses the potential environmental effects of the proposed decommissioning and considers four options for the process:

• Complete removal/full restoration (Caltech's preferred alternative)
• No action (an alternative that is recommended to be evaluated)
• Complete removal/moderate restoration
• Partial removal/moderate restoration

A copy of the DEA/AFONSI can be found on the CSO public information wiki page.

The DEA and information concerning a companion Conservation District Use Application is expected to be published online after September 8. Once published, the DEA will be subject to a 30-day public comment period.

Public comments can be submitted via email or in writing.

In addition, the public is invited to attend virtual community meetings scheduled for Tuesday, September 28, at 2:30 p.m. Pacific Daylight Time (PDT); Wednesday, September 29, at 7:30 p.m. PDT; and Thursday, September 30, at 9 p.m. PDT. At the meetings, the proposed decommissioning will be described in detail and questions answered informally. Each of the meetings will present the same information.