Colorado Gov. John Hickenlooper will not protest a Trump administration effort to allow oil and gas drilling on 18,000 acres near the Great Sand Dunes National Park, even though Democratic state lawmakers and environmentalists are challenging the plan.

Hickenlooper, a two-term Democrat and former energy industry geologist, initially expressed concerns and planned to send a letter opposing the federal Bureau of Land Management’s plan to auction mineral rights on 11 parcels, one of which critics say is within a mile as the crow flies from the dunes.

“Obviously, I’m not excited about it,” he told reporters March 13. “And I am concerned about it and plan to look into it.”

But the governor since softened his stance — and allowed Friday’s deadline for public comment to pass without an objection — because he learned that the energy development would take place on the eastern side of the Sangre de Cristo Mountains, not on the western side, where the dunes are located.

Jacque Montgomery, a spokeswoman, said the governor asked his administration to evaluate the maps and “closely monitor the situation,” but ultimately decided against sending a letter of protest after he learned more details about the proposal.

The state Senate Democratic caucus reached the opposite conclusion. In a letter sent Friday to the BLM’s acting Colorado director, the 16 lawmakers wrote that “the federal push to auction off pristine public lands is a threat to communities in southern Colorado.”

The letter expresses concern that the proposed drilling would be visible from the peaks above the park, and the noise, pollution and lights from the operations would “poison our dark night skies, disrupting the solitude.”

But state Senate President Kevin Grantham, whose district is near the area in question, said the drilling operations would benefit the region.

“The operations are clean, they are quiet — all you have to do is visit them to see it,” he said in a recent interview. “It would be good for the economy down there, and they need some boost down there.”

Environmental advocacy organizations issued warnings about the mineral rights auction on the final day for public comment, with the Sierra Club in Colorado blasting the idea of “sacrificing these places, the wildlife there, history and opportunities to an outdated vision of energy independence.”

Ten of the 11 parcels scheduled for auction this summer are within eight miles of the sand dunes, according to environmentalist and maps of the project. It follows efforts by U.S. Interior Secretary Ryan Zinke to promote energy development on federal lands.