Well Water and Coal-Mine Subsidence in Musselshell County, Montana

How longwall mining dries up wells: the documented mechanism

Longwall mining, the method Signal Peak Energy uses in the Bull Mountains, deliberately lets the mine roof collapse behind the advancing cutting machinery rather than leaving it supported. That controlled collapse causes measurable surface subsidence -- cracking, fissuring, and depression of the ground above each mined-out panel -- and in the Bull Mountains' geology, that subsidence has fractured the perched aquifers and shallow rock-and-soil water systems that area ranchers depend on for stock wells and natural springs. One of the most-cited examples in the public record involves rancher Ellen Pfister's Mountain Spring, historically a water source for her cattle and for wildlife on her land, which went dry as Signal Peak's longwall panels advanced beneath it. This is not a one-off, disputed anecdote -- it is central to multiple lawsuits filed by Earthjustice on behalf of the Bull Mountains Land Alliance, Northern Plains Resource Council, and the Montana Environmental Information Center, arguing that Montana's Department of Environmental Quality has allowed mining to continue without adequately enforcing the water-replacement obligations state and federal strip-mine law require.

Signal Peak's own mining permit lays out both short-term and long-term strategies for restoring water lost to subsidence: hauling water to affected landowners, giving them access to on-site monitoring wells, and impounding snowmelt and rainwater as a longer-term substitute. But research cited in the litigation asserts the mine cannot replace even one percent of the water it actually drains from the surrounding aquifers, and in at least one documented case, DEQ reduced Signal Peak's water-replacement obligations for a specific rancher without first notifying that landowner -- a decision one filing describes as causing a 'meaningful net-loss of usable water.' Whatever the eventual legal outcome, this is a real, checkable regulatory dispute over whether the replacement obligation is being met in practice, not a hypothetical concern raised only by activists.

Where the litigation stands as of this review

This has played out over several years and is still unresolved. In 2023, a federal court halted new federal-coal mining at the site pending a full environmental impact statement examining the mine's effects on ranchers, water sources, and the surrounding environment. In 2024, the same coalition of groups challenged a separate Montana DEQ decision that would have allowed additional coal mining at Bull Mountain Mine. In June 2025, the U.S. Department of the Interior approved a mining-plan modification (the 'AM6' expansion) authorizing roughly 22.8 million tons of additional federal coal and 34.5 million tons of adjacent non-federal coal, extending the mine's operating life by up to nine years. That approval was itself challenged: a new lawsuit filed in early 2026 specifically targets subsidence and land damage from the expansion, and a subsequent appeal contests the AM6 approval on both water and tribal-interest grounds. None of these threads has reached a final resolution as of this writing -- the outcome could still narrow the mine's footprint, force stronger water-replacement commitments, or leave the current approvals largely in place.

What to check before buying land near the Bull Mountains

If a parcel is anywhere near the Bull Mountains mining area, treat proximity to Signal Peak's permitted panels as a real due-diligence item, not background noise. Specifically:

• Ask Montana DEQ's coal-mining permit program for maps showing where Signal Peak's approved and already-mined-out longwall panels sit relative to the specific parcel.
• Ask the seller and neighboring landowners directly whether any wells or springs on or near the property have shown reduced flow, gone dry, or changed in water quality since mining activity began nearby.
• Request any available Montana Bureau of Mines and Geology groundwater-monitoring data for wells in the surrounding area, if such monitoring exists for the parcel in question.
• Ask whether the property, or a water right tied to it, has ever been the subject of a DEQ water-replacement determination, a landowner complaint, or any of the pending federal litigation described above.
• Check current case status directly with Earthjustice, the Bull Mountains Land Alliance, or Northern Plains Resource Council before closing, since this litigation is active and its outcome could change after this page was last reviewed.