Caltech Submillimeter
            Observatory California Institute
            of Technology

CSO Releases Draft Environmental Assessment

December 2021: Final Environmental Assessment to be Published for Decommissioning Caltech Observatory from Maunakea  

2021 Dec 08

The California Institute of Technology (Caltech), in cooperation with the Hawai'i Department of Land and Natural Resources (DLNR), has released its Final Environmental Assessment and Finding of No Significant Impact (FEA/FONSI), which was prepared as part of the planning effort required prior to decommissioning of the Caltech Submillimeter Observatory (CSO).
The FEA was prepared by Caltech's consultant, Planning Solutions, Inc. (PSI). It addresses the potential environmental effects of the proposed decommissioning of the CSO. Hawai'i law requires an environmental review due to the use of State land and the need for a Conservation District Use Permit. A copy of the FEA and other planning documents can be found here:

"The FEA addresses the comments submitted by the public in response to the Draft Environmental Assessment, which was released on September 8, 2021," said Caltech physics professor and CSO Director Sunil Golwala.  Nearly 20 comments were received during the comment period.

The State Environmental Review Program will publish the FEA on December 8, 2021, in The Environmental Notice. The FEA will also be available online at
DLNR continues to process Caltech's Conservation District Use Application. If the regulatory process is completed as currently anticipated, Caltech aims to begin removing the observatory and restoring the site by Summer 2022. It will be the first observatory removed under the 2010 Decommissioning Plan for Maunakea Observatories. "We hope that a Conservation District Use Permit is granted in early 2022, which would enable Caltech to begin the deconstruction and restoration on schedule," said Golwala.
The CSO was formerly one of the world's premier facilities for astronomical research and instrumentation development at submillimeter wavelengths.
The CSO's 10.4-meter submillimeter telescope, which came online in 1987 for use in research by astronomers at Caltech and other institutions, is housed in a compact dome near the summit of Maunakea. The telescope was used by researchers, including almost  200 student and postdoctoral researchers, to open a new submillimeter window on the universe. A summary of CSO's contributions to astronomy and astronomical instrumentation are available here: All the astronomical instruments were removed from the facility in 2015.

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