Caltech Submillimeter Observatory Site Decommissioning Plan Approved by Maunakea Management Board

Caltech's draft Site Decommissioning Plan (SDP) to remove the Caltech Submillimeter Observatory (CSO) and restore the site was unanimously approved by the Maunakea Management Board (MKMB) on March 2, 2021.

CSO is one of the first two observatories on the mountain to undertake the decommissioning process, along with the University of Hawai‘i Hoku‘kea telescope. CSO is the first to submit its SDP for review. Caltech hopes to have its plans approved by early 2022, which would enable the physical deconstruction and restoration to begin by summer 2022. MKMB is a board of community volunteers that advises the University of Hawai‘i's Office of Maunakea Management, which oversees the Maunakea Science Reserve.

"We thank the many members of the Hawai‘i Island community who contributed to CSO's years of ground-breaking work," Caltech physics professor and CSO director Sunil Golwala says.

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 radio 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. During its operational period, which ended in 2015, the telescope was used by researchers, including more than 200 students, to open a new submillimeter window on the universe. All of the astronomical instruments were removed from the facility in 2015.

"It was Caltech's privilege to operate CSO on Maunakea and an honor to continue our relationship with the mauna and its people through this decommissioning effort and Caltech's participation in other astronomy projects," Golwala added. "Caltech will continue to carefully consider community input as it seeks further approvals of the CSO decommissioning project."

As the next step in the process, mandated by the State of Hawai‘i Department of Land and Natural Resources, a draft Environmental Assessment (EA) that evaluates and discloses the impacts of the implementation of the Site Decommissioning Plan is being prepared. The draft EA is expected to be available by summer and will be subject to a 30-day public comment period.

These four options will be considered in the EA:

• Complete removal/full restoration (Caltech's preferred alternative);
• No action. (An alternative that is a requirement of the EA);
• Complete removal/moderate restoration;
• Partial removal/moderate restoration.

The SDP describes the current condition of the site; how the facility, its infrastructure, and all improvements will be deconstructed and removed, and how the site will be restored. Caltech is financially responsible for decommissioning. The final SDP will be revised based on feedback from the Maunakea Management Board and the Center for Maunakea Stewardship (CMS).

Caltech commissioned several studies to inform its analysis of the alternatives. These studies included an archeological assessment, a cultural impact assessment, a hydrogeological evaluation, a biological inventory, a biological setting analysis, and a traffic analysis.

In addition to these studies, Caltech undertook two sets of meetings with key government, community and business leaders to solicit concerns and obtain feedback on the alternatives. The first set of meetings occurred in early 2018 and the second in early 2020.

Caltech hopes that the Final Environmental Assessment is accepted and a Conservation District Use Permit (CDUP) is granted in early 2022, which would enable Caltech to begin the final phase of deconstruction and restoration in the summer of 2022.