The U.S. Environmental Protection Agency is urging the National Science Foundation to consider alternative construction sites for the Thirty Meter Telescope — and possibly a smaller version of the proposed observatory — in its upcoming environmental review of the controversial project.

In comments submitted on the scope of the project, the EPA said it is concerned that constructing the telescope as currently proposed has the potential to result in “disproportionately high and adverse impacts to Native Hawaiians.”

“While the general population would benefit from the project, the negative impacts associated with the project seem to be borne predominantly by local indigenous populations who face existing environmental and social vulnerabilities,” the EPA letter, dated Monday, says.

The federal agency pointed out that Mauna Kea is “an extremely sensitive cultural resource” and urged the NSF to consider in its environmental impact statement “opportunities to avoid, minimize or mitigate any impacts, particularly those identified through community engagement.”

“We strongly recommend that the EIS include a robust analysis of cultural resource, environmental justice and cumulative impacts to evaluate and address the ongoing and historic impacts to Native Hawaiians from activities on and near Mauna Kea,” the letter says.

Veteran TMT foe Kealoha Pisciotta of the Mauna Kea Hui said she was impressed by the EPA’s comments.

“It threw me off a little. I don’t recall them saying much in the past,” Pisciotta said Wednesday. “This appears to be a change, and it could be going in a different direction.”

Monday was the deadline for comments regarding the scope of the NSF’s proposed EIS, designed to help the funding agency determine whether to help finance and operate the proposed TMT.

The science foundation held four scoping meetings on Hawaii island in August in which the proposed $2.65 billion, cutting-edge telescope was sharply criticized by largely Native Hawaiian crowds.

The meetings were the latest in a line of dissent and controversy generated by the proposed Mauna Kea telescope over the better part of a decade. Construction of the project was stopped by protesters in 2015 and 2019 and was put on hold throughout the COVID-19 pandemic.

But with the delay came rising costs, and the price of construction ballooned from an estimated $1.4 billion to what’s now closer to $3 billion. During that period, TMT officials combined forces with the U.S.-led Giant Magellan Telescope, planned for Chile, to form the U.S. Extremely Large Telescope Program. Together they formally asked the NSF for funding.

A year ago the decadal survey report by the National Academy of Sciences Astro 2020 panel recommended that the NSF fund both telescopes to allow viewing time for American astronomers on both projects. The panel recommended that the projects share $1.6 billion.

In regard to the TMT, the NSF’s plan calls for preparing an EIS that complies with the National Environmental Policy Act and conducting a formal consultation with Native Hawaiians as called for in Section 106 of the National Historic Preservation Act.

A draft of the EIS is expected to be ready early next summer, officials said, and the whole process is expected to take at least two years.

However, NSF officials note that a decision not to go forward with an investment in the TMT could be made at any time, including before the environmental review process is over.

As proposed, the TMT would rise 18 stories and be the tallest building on Hawaii island. The mammoth structure would cover 1.44 acres within a 5-acre complex.

In its comments, the EPA encouraged the NSF to include analysis of other locations beyond its proposed site, which is near and just below the 13,796-foot Mauna Kea summit. Other locations to be considered, it said, should be decommissioned telescope sites and other areas already disturbed by development.

The EPA also recommended that other design options be considered to lessen the overall impact of the telescope, including the supporting infrastructure.

The agency also asked the NSF to compare and contrast the environmental impacts for both Mauna Kea and the TMT alternative site in the Canary Islands and even conduct additional studies, if warranted, to produce comparable information for both locations.

“As cultural resources are so important at the Hawaii location, we encourage the NSF to include a comparison of impacts to cultural resources between the Spain and Hawaii locations in addition to any other alternatives identified,” the letter says.

The EPA pointed to recent executive orders by President Joe Biden that direct federal agencies to advance equity and justice for underserved communities, including Native Hawaiian/Pacific islander communities. The orders seek to eliminate barriers to equity and justice for those populations.

The EPA also urged the NSF to align its work with the Mauna Kea Stewardship and Oversight Authority, newly created by the state Legislature, that will assume sole responsibility of the astronomy precinct from the University of Hawaii following a three-year transitional period.

Gov. David Ige recently named his appointments to the 11-member authority, which includes a mix of Native Hawaiians, cultural practitioners and representatives of the state and other institutions, who must still win state Senate confirmation.

In its letter, the EPA said the new oversight authority should be “a critical partner” in the environmental process to ensure the draft EIS, as well as a final decision and any potential construction, would be in line with the authority’s planning efforts, including the future framework for astronomy development.

In its comments, the Office of Hawaiian Affairs urged the NSF to put its environmental review on hold until the direction and intent of the oversight authority is known and formally on the record.

The authority’s three-year transition period is scheduled to begin July 1, assuming all of its members are confirmed.