Emotions have been running high about the plan to build another telescope on Mauna Kea, a mountain on the Big Island that’s already home to a thriving astronomy industry. Hundreds of activists remain at the base of Mauna Kea Access Road and plan to stay to prevent construction trucks from heading up the mountain.

Some who consider the mountain sacred believe adding another structure to be desecration, no matter what that structure is. But many opponents also have concerns about the environmental impact of what would be the world’s largest visible-light telescope.

Courtesy of the Thirty Meter Telescope

Some of the environmental claims raised on social media, like rumors about the TMT being fueled by nuclear power, are false. Other facts are more nuanced or complex than they initially appear.

It doesn’t help that the University of Hawaii has a poor history of managing the mountain. A 1998 state audit found that observatories left trash and old equipment and damaged historical sites and endangered species candidate habitat. The mountain facilities also have a history of chemical and waste spills that include up to 1,000 gallons of sewage overflowing in 2008.

But the university has improved its management of the mountain over the past two decades and the TMT International Observatory, the nonprofit organization behind the TMT, says this project will be a zero-waste facility with minimal impact on the mountain.

Civil Beat examined some of the key environmental questions about the project:

How big will the TMT be?

Civil Beat recently received this question from a reader: “How much more land is intended to be used for the new telescope or are they removing one or two of the old telescopes and using the same pads for the new one? I’ve been told they are taking thousands of more acres? Is this true?”

The TMT is going to be built on a new site, not on top of decommissioned telescopes. The entire project area is expected to take up 5 acres, including the telescope dome, support building and parking lot. The building itself will be 180 feet high and 14 feet below ground level.

Courtesy of the Thirty Meter Telescope

Gordon Squires, vice president for external relations for the TMT International Observatory, says the project site is less visible than the mountain peak would be and isn’t home to any endangered species. The project construction won’t involve dynamite.

The organization’s environmental impact statement acknowledges that the TMT’s construction will disturb some habitat of the wekiu bug, formerly a candidate for the endangered species list. The analysis includes plans to mitigate the impact.

A previous version of this story incorrectly said that the wekiu bug was a former endangered species.

Squires says the TIO also has a plan to decommission the telescope after its lifetime, which is estimated to be 50 years of use.

Currently the state is planning to decommission five telescopes on the mountain. Two have been sitting unused for several years and are in the process of being decommissioned. The remaining 11 observatories are in use and continue to produce scientific data.

What impact — if any — will the TMT have on the Big Island’s aquifer and water supply?

The TMT’s potential effect on the water supply is one of the most commonly voiced environmental concerns by activists.

The state has concluded that the telescope doesn’t pose a risk to the aquifer or Hawaii island’s water supply. This is based on scientists who testified at public hearings and contributed to the environmental analysis of the project.

The closest groundwater wells are 12 miles away and because the project site is thousands of feet above sea level, it’s expected to have no significant impact on natural resources. Here’s Judge Riki May Amano’s description in her ruling approving the TMT’s 2017 permit:

“The groundwater beneath the summit of Mauna Kea is impounded and compartmentalized by subsurface geologic structures. Because the TMT Observatory will use a zero-discharge wastewater system, wastewater will not be released from the TMT Project so no percolation of wastewater will reach the aquifer.

“Moreover, Mauna Kea is comprised of very porous lavas that naturally treat and filter water percolating downward. A discharge on the summit area would be naturally treated and filtered through thousands of feet of the porous lavas, which would remove any contamination from that discharge before reaching any groundwater.

“Contamination of groundwater is extremely remote and very unlikely from the TMT Project. There is no reasonable prospect of an adverse impact on either drinking or coastal waters from the TMT Project.”

Cory Lum/Civil Beat

Here’s why some opponents still have concerns about the impact on drinking water despite the judge’s ruling.

Kealoha Pisciotta, a longtime opponent of the TMT, says that she doesn’t believe scientists know enough about the mountain’s geology to be certain that any potential chemical spills wouldn’t reach the groundwater. She noted that scientists are still discovering new information about where water is located on Hawaii island. The TMT’s environmental impact statement was conducted in 2009 and she thinks there should be a newer analysis done with better experts.

What about chemical spills and hazardous waste?

As far as buildings go, the TMT is taking lots of steps to prevent any emission of waste. Solid waste and hazardous waste produced by existing observatories are already routinely removed from Mauna Kea. The nonprofit behind the TMT has a multi-step plan to ensure the telescope doesn’t pollute the mountain.

“All of our containment vessels are double-walled, all of our waste is removed from the mountain,” says Squires of the telescope. “None of it is discharged up there.”

Unlike previous observatories, the TMT will not use mercury.

Opponents’ concerns about pollution stem from past spills of hydraulic fluid and other chemicals. Some observatories’ generators use diesel fuel, waste oil and coolant such as ethylene glycol.

“In the past, there have been instances in which the cinder was contaminated and then excavated to contain the potential effects of the spill,” the TMT’s environmental statement acknowledges.

But not all spills occurred outdoors. The analysis also says: “The best available information suggests that while mercury spills have occurred, spilled amounts occurred inside during mirror handling activities and were small.”

At Hale Pohaku, where facilities for astronomers and other observatory staff exist, there are three underground storage tanks that hold diesel fuel and gasoline. These exist whether or not the TMT is built, and the project’s environmental analysis says there have never been leaks at these underground storage tanks.

Will the TMT use nuclear power?

No. This is an unfounded claim that’s occasionally floating on social media.

The TMT will rely on Hawaii County’s electric grid, similar to other observatories. There won’t be any nuclear power used on the site at all, and there is no nuclear energy currently used by other telescopes on Mauna Kea.