Mining Milestones: D.C. Circuit Upholds Key Mill Site Flexibility – What’s Next?

By Lucas Narducci, Michael Ford, Jim Allen, and Sukhmani Singh¹

A recent decision by the U.S. Court of Appeals for the D.C. Circuit in Earthworks v. U.S. Department of the Interior has important implications for mining companies operating on public lands. This ruling upholds the Bureau of Land Management’s interpretation of the Mining Law of 1872, which allows multiple mill sites to be located per unpatented mining claim, provided no single site exceeds five acres. Given the essential role that mill sites play in handling waste and other secondary operations associated with mining, the court’s decision offers much needed clarity and operational flexibility for mining companies. As the case continues to evolve, with environmental organizations seeking further review, the outcome could continue to shape the legal landscape for mill site usage in the mining industry.

In June 2024, the U.S. Court of Appeals for the D.C. Circuit, in Earthworks v. U.S. Department of the Interior, reviewed a challenge by environmental organizations to a Bureau of Land Management (“BLM”) rule concerning mill site claims on public lands.² The rule permits multiple mill sites to be located per unpatented mining claim, provided no individual mill site exceeds five acres.³ Mill sites are used for facilities associated with mining operations, such as waste rock and tailings piles, as well as processing facilities.⁴ This space is critical for mines, as unwanted material cannot be disposed of on the mining claim itself. The plaintiffs argued that this interpretation violated the Mining Law of 1872, the National Environmental Policy Act (NEPA), and the Administrative Procedure Act (APA).⁵ The court sided with the BLM and the intervening mining companies, affirming the lower court’s decision in favor of the government.⁶

The court held that BLM’s interpretation of the Mining Law was reasonable.⁷ While the Mining Law of 1872 sets a five-acre limit for individual mill sites, it does not explicitly limit the number of mill sites that can be located per unpatented mining claim.⁸ The court agreed that multiple mill sites could be located for a single mining claim if each site stayed within the five-acre limit.⁹ This interpretation was supported by the agency’s decades-long practice, which had never been challenged, and by the statute’s silence on limiting the number of mill sites.¹⁰ The ruling is the latest word in a partisan back-and-forth reaching back to the Clinton Administration.¹¹

This decision takes on added significance in light of the Rosemont Copper Mine case decided by the Ninth Circuit in 2022.¹² In the Rosemont case, the court rejected the mining company’s claim that longstanding BLM practices permitted the use of federal lands for waste disposal without a separate claim.¹³ The ruling created uncertainty across the industry, as it appeared to limit mining companies’ ability to store waste materials on federal land, potentially increasing costs and complicating operations. However, the D.C. Circuit’s decision in Earthworks helps to alleviate these concerns. By affirming that multiple mill sites, each limited to five acres can be established for waste rock, tailings piles, and other secondary operations, Earthworks reinstates some of the flexibility that the Rosemont case had seemingly curtailed.¹⁴

The environmental organizations have since requested an en banc review of the D.C. Circuit’s decision.¹⁵ Earthworks and the other environmental groups argue that the rule misinterprets the Mining Law of 1872 by allowing unlimited mill sites per unpatented mining claim, contrary to what they believe is a statutory limit of five acres per claim.¹⁶ The petition calls for reconsideration on both NEPA and statutory grounds.¹⁷ Earthworks argues that the BLM’s rule allows for excessive environmental impacts, and that the D.C. Circuit Court misinterpreted the Mining Law.¹⁸ This matter remains pending as the D.C. Circuit has not yet decided whether to grant the petition for en banc review. If the court denies the petition, the case will stand as decided.

The Earthworks decision validates (for now) the use of mill site claims for disposal of the large amounts of waste generated by modern hard rock surface mines on public land. But this solution to the waste disposal issue carries with certain limits and complications. First, mill site claims may not be located on land that contains valuable minerals.¹⁹ Second, in the same way that a mining claim must be perfected by discovery of a valuable mineral within the border lines of the claim, a mill site claim must be perfected by actual occupancy of the claim for mining purposes. A claimant must “use or occupy each two and a half acre portion of a mill site” or risk having the claim reduced to the portion actually in use.²⁰ The second issue presents particular challenges for mine planners, because until the mill site is actually occupied in the course of operations, it cannot be a “valid existing right” that would survive withdrawal of the land for conservation or other purposes (e.g., to preserve sage-grouse habitat, or to protect watersheds.)

While the D.C. Circuit’s ruling in favor of BLM and mining companies represents a victory for the industry, the Earthworks case remains active, with environmental groups petitioning for an en banc review. The ongoing legal developments could lead to further scrutiny of mill site practices and the interpretation of the Mining Law of 1872. However, unless the petition is granted and the decision overturned, the D.C. Circuit’s ruling provides a stable legal foundation for mining companies to continue utilizing multiple mill sites for their operations.