SIOUX FALLS, S.D. (KELO) — The Oglala Sioux Tribe has drafted a letter to ask the Black Hills Forest Service to withdraw a decision notice on a gold exploration project.

The Jenny Gulch Gold Exploration Project is a year-long drilling project planned near Silver City, South Dakota, in search of gold. In July, the Forest Service issued a decision notice providing the public with 45 days to object to the project. The last day to do so is today, August 22.

Last week, the Oglala Sioux Tribe wrote a letter to oppose the project.

“The Black Hills are sacred to our people,” the letter reads. “We know them as ‘the heart of everything that is.’ The Forest Service has failed to comply with the law and has failed to consider the environmental and cultural impacts of the Project under the National Environmental Policy Act.”

According to the letter, the Forest Service did not consult with the tribe before the environmental assessment or permit, which would be a violation of the National Historic Preservation Act and the National Environmental Policy Act.

The decision notice from the U.S. Forest Service found no significant impact from the project. But the letter from the tribe claims the drilling could impact the Pactola Reservoir and other water in the Black Hills.

According to the notice, the project would drill four dozen holes in the proposed project area.

In addition to potential environmental impacts, the Oglala Sioux Tribe is worried about future projects and “exploitation” of the Black Hills as a result of the gold exploration project.