Saddle Road is shutting down to remove Maunakea observatory. But when?

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The Caltech Submillimeter Observatory that houses a 10.4 meter diameter telescope near the summit of Maunakea on the Big Island is on track to be decommissioned this year. Photo Courtesy: California Institute of Technology

Physical removal of the Caltech Submillimeter Observatory on Maunakea on Hawai‘i Island will begin in late spring.

Extensive planning and permitting for the decommissioning and removal have been underway for several years.

“Over the winter, we finalized plans and prepared permitting applications to remove the telescope and transport it from the mountain,” said Caltech physics professor and Caltech Submillimeter Observatory Director Sunil Golwala.

“To transport the main mirror of the telescope to the harbor will require several road closures,” Golwala continued. “We are alerting state, county, and University of Hawai‘i agencies and the community at each step.”


Caltech has been in contact with Hawai‘i Department of Transportation, Hawai‘i County Police Department, and County of Hawai‘i Department of Public Works about road permitting requirements for transporting the telescope’s 34-foot diameter primary mirror to Kawaihae Harbor. A practice run with a dummy mirror is planned to verify procedures and identify potential issues. The removal process, including the practice run, will take place over six weeks.

The first part of the practice run, on two consecutive days, will be between the Maunakea summit and Daniel K. Inouye Highway, also known as the Saddle Road. A nine-day window is set for this stage to allow flexibility for adverse summit weather conditions.

The entire route will not be closed at one time, but in sections over several days. Photo Courtesy: Caltech

The first day will involve the daytime transport of the dummy mirror from the summit to the Maunakea Visitor Information Station. The Mauna Kea Access Road between the summit and the Visitor Information Station will be closed to all motorists for approximately seven hours.

On the second day, the dummy mirror will be moved from the Visitor Information Station to a staging area near the intersection of the Mauna Kea Access Road and Inouye Highway. The Mauna Kea Access Road will be closed between Inouye Highway and the Visitor Information Station for approximately two hours. There will be a brief closure of Inouye Highway to permit the transport to move from the Mauna Kea Access Road to the old Saddle Road junction about a half-a-mile to the west.


The second part of the practice run will be on two consecutive nights. The specific nights will be determined and publicized in the near future. On the first night, the transport will travel from the staging area to a contractor yard near the bottom of Waikoloa Road in Kohala. On the second night, it will continue to Kawaihae Harbor.

These nighttime trips will start about 10 p.m. and will be completed by 5 a.m. They will require intermittent closures of eastbound and southbound traffic on Inouye Highway, Highway 190, Waikoloa Road, Queen Ka’ahumanu Highway, and Kawaihae Road. Traffic in the westbound and northbound directions will be subject to traffic control and reduced speeds, but there will be opportunities to pass the transport.

The actual removal of the telescope’s primary mirror will follow the same pattern. The mirror will be transported from the summit of Maunakea to the Visitor Information Station and then to the same staging area on two consecutive days during a 16-day window approximately one week after the practice run reaches Kawaihae. Again, these dates are flexible to allow for adverse weather. The second part of the transport, from the staging area to Kawaihae Harbor, will occur on two consecutive nights, with specific dates to be publicized in the near future.

Organizers say the goal of this early notification, before dates are fixed, is to provide notice for motorists to plan for these closures and to seek feedback on potential conflicts with other activities. Feedback can be directed to Simon Radford at, (808) 333 4871.


“Other telescope parts will be taken down from the summit as weather permits,” said Golwala. “As those parts are smaller, no road closures will be required.”

Once the telescope is removed, Goodfellow Bros., a general contractor, will begin dismantling the buildings that housed the CSO telescope and will begin the full restoration of the site. Caltech anticipates that decommissioning and restoration will be completed during 2023.

The cost of deconstruction and restoration is expected to exceed $4 million.

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