The first two observatories of as many as five of the existing 13 that dominate the landscape atop Mauna Kea are expected to be decommissioned by late 2023. Separate draft environmental assessments for the two projects are available for public review and comment through Oct. 8.

One is the Caltech Submillimeter Observatory, built in 1987 by the California Institute of Technology, a partner institution in the planned construction of the controversial Thirty Meter Telescope. The other is the University of Hawaii at Hilo’s Hoku Kea, which was one of the first built on Hawaii’s tallest mountain, which is held sacred by many Native Hawaiians. That facility was built in 1970 by the Air Force and later given to the university.

Both observatories have already closed, and the draft EAs do not anticipate any significant impacts from their dismantling.

However, environmentalists will be taking a close look at possible chemical discharges that may have occurred there over the years and what can be done to mitigate water contamination by the cesspool that served the Caltech observatory. Hoku Kea does not have a cesspool.

“We outlined our concerns regarding the cesspool, which is unlined, had received human excrement but also some other chemicals, and looked at how deep they had flowed as a result of precipitation,” Deborah J. Ward, chairwoman of the Hawaii island group of the Sierra Club of Hawaii, said of her group’s 2015 meeting with an official who started the EA process for Caltech. “That remains one of our concerns.

“The hydrologic system at the summit is not well known and hasn’t been studied,” said Ward, a retired UH professor of natural resources and environmental management. “At the summit of Mauna Kea, there are perched water bodies and dikes that hold water between the layers. There are seeps and water flows out. One seep is being used by (the Army’s Pohakuloa Training Area).

“The water from the top of the aquifers should be clean. When you put human feces into the aquifer at the summit, it’s very offensive to Hawaiians.”

The Caltech draft EA identifies five aquifer systems that connect to the peak of Mauna Kea: Honokaa, Paauilo, Hakalau, Onomea and Waimea. A study in 2019 to assess the potential for groundwater pollution from the cesspool showed there is no direct information on the regional groundwater table below the summit, the draft assessment said. However, studies suggest “the frequency and extent of perched or high-level groundwater bodies is higher than previously anticipated.”

Similarly, the Hoku Kea draft EA shows the Waimea Aquifer System, with an estimated yield of 16,000 gallons of fresh water daily, is beneath its project site. However, “the depth to ground- water at the summit is unknown.”

Later studies in the region between Mauna Loa and Mauna Kea found ground­water at a much shallower depth and a dike-impounded aquifer, the draft report said.

The Hoku Kea document said the decommissioning work could have a substantial adverse effect on traditional, customary and contemporary cultural practices if it unduly restricts or prevents cultural practices from taking place and substantially alters or removes locations where such practices take place; and if noise, traffic and human presence alter those settings.

The assessment said the work would have a temporary impact to cultural practices since it would take roughly five months, but would not disturb any above-ground archaeological properties and would have beneficial impacts to the area by removing the man-made facilities.

Site deconstruction and removal is expected to begin in early March 2023 and take three months, the report said. Restoration would take two months, ending in August 2023.

If the regulatory process goes as planned, Caltech officials anticipate work to begin by next summer to remove their observatory and fully restore the site within 140 working days.

The Sierra Club’s Ward said chemical contaminants were found in a small sampling taken at the site. Her group has asked Caltech to identify what chemicals had been used.

In a contested case in 2003, “We actually asked for chemicals being used. We got 10,000 pages of material safety data sheets,” she said.

There is a list of mercury spills for the comprehensive management plan for Mauna Kea but not at the Caltech site, Ward said.

Caltech physics professor and observatory Director Sunil Golwala said there is no evidence of leakage from the cesspool. In 2009 there was a small hydraulic fluid leak, likely from the hydraulics system that operates the dome, he said.

“It was cleaned up. We need to see if any residual hydraulic fluid leaks occurred during construction,” Golwala said.

The draft EA concludes there is no concern about that, and that the soil under the foundation will likely have a small amount of contamination and that the majority of the site is fill material.

“There is no expectation of any deep-down contamination,” he said. “When we excavate, we will be doing testing as we pull out material.”

Concerns about mercury being dumped into the cesspool were raised, but mercury was never used at the Caltech site, he said. Addressing concerns about whether photographic film-developing chemicals entered the cesspool, Golwala explained that “we never used film.”

Caltech announced the observatory’s decommissioning in 2009, six years before it was closed in 2015. The process will cost $3.5 million, give or take 30%, Golwala said.

“No one had expected the process of taking something down would have taken as long as the process of putting something up,” he said, adding that the process requires time-consuming surveys and extensive documentation, plans and assessments.

The draft EA required a hydrogeological evaluation, a biological inventory and archaeological and cultural impact studies, among others.

The observatory houses the 10.4-meter Leighton Telescope, and Caltech plans to refurbish the instrument and relocate it to Chajnantor, Chile. If that fails due to funding issues, the telescope might be destroyed and its pieces removed, he said.

“We’re trying to complete this as expeditiously as possible.”

Hoku Kea’s decommissioning includes “the safe and proper removal of two buildings and supporting infrastructure, and restoration of the site to its original state, as much as possible.”

UH, which oversees the 11,288-acre Mauna Kea Science Reserve, recently released a draft master plan allowing for no more than nine astronomy facilities on the summit by the end of 2033. In addition to the Caltech and Hoku Kea facilities, two other telescopes, yet to be determined, would be pulled out of operation to meet that deadline.

Should the TMT be built, an additional observatory would need to be taken down and removed.

HAVING A SAY

Caltech Submillimeter Observatory decommissioning

>> Find documents and other information at cso.caltech.edu/wiki/cso/outreach/outreach. The deadline for comment is Oct. 8.

>> Virtual community meetings. Proposed decommissioning will be described in detail and questions answered at 11:30 a.m. Sept. 28, 4:30 p.m. Sept. 29 and 6 p.m. Sept. 30. On the day of the meetings, a Zoom link will become live at the website listed above.

>> Written comments. Email to cso-decom@caltech.edu or mail to Planning Solutions Inc.; Attn: Makena White, AICP; 711 Kapiolani Blvd., Suite 950; Honolulu, HI 96813.

Hoku Kea decommissioning

>> Find documents and other information on the project web page at hokukea.konveio.com. The deadline for comment is Oct. 8.

>> Virtual public meeting. A presentation and question-and-answer session with UH Hilo Center for Maunakea Stewardship Executive Director Greg Chun and other officials is scheduled for 5:30 to 7 p.m. Wednesday. Register for the Zoom session on the project web page.

>> Written comments. Email to jscheffel@ssfm.com or mail to Jennifer Scheffel, SSFM International Inc.; 99 Aupuni St., Suite 202; Hilo, HI 96720.