Billings, Montana — population roughly 120,000 — is the largest city in a state known for clean water and big sky. The city draws its drinking water from the Yellowstone River, the longest free-flowing (undammed) river in the contiguous United States. That sounds like an environmental victory, and in many ways it is. But Billings sits in a stretch of the Yellowstone Valley where petroleum refining, coal mining legacy, and intensive agriculture converge — and that combination creates water quality dynamics that residents should understand.
The Yellowstone River: Free-Flowing but Not Pristine
The Yellowstone River begins in Yellowstone National Park and flows roughly 670 miles northeast through Montana before joining the Missouri River in North Dakota. By the time it reaches Billings, the river has left the mountains and entered the agricultural and industrial heartland of central Montana.
Billings’ water treatment plant draws raw water from the Yellowstone and treats it through a conventional process: coagulation, flocculation, sedimentation, filtration, and disinfection with chlorine. The treated water serves the city and several surrounding communities.
The Yellowstone’s water quality at Billings is generally good — it’s a large, dilute river with strong flow for most of the year. But spring runoff brings elevated turbidity and sediment, and late-summer low flows can concentrate contaminants. The river also carries the accumulated impacts of upstream land use: livestock grazing, irrigated agriculture, and small-town wastewater discharges.
Refinery Row
What makes Billings unusual among Montana cities is its concentration of petroleum refining. The city is home to two major refineries — CHS (formerly Cenex) and ExxonMobil (Billings Refinery) — that process crude oil from the Bakken formation, Wyoming’s Powder River Basin, and Canadian sources.
These refineries have operated for decades, and their presence creates both air quality and water quality concerns. Historical spills, leaks, and industrial discharges have left contaminated soil and groundwater at various locations in the Billings area. The Montana DEQ has overseen cleanup activities at several petroleum-contaminated sites in and around the city.
The Yellowstone River itself has been impacted by refinery incidents over the years. In 2011, an ExxonMobil pipeline ruptured near Laurel (just upstream of Billings), spilling an estimated 63,000 gallons of crude oil into the Yellowstone during summer flooding. The spill contaminated approximately 70 miles of riverbank and raised acute concerns about drinking water quality downstream. Billings’ water treatment plant temporarily shut down its river intake as a precaution.
While the 2011 spill was cleaned up and the pipeline replaced, it highlighted the vulnerability of a city that draws drinking water from a river that’s also a petroleum transportation corridor. Multiple pipelines cross the Yellowstone in the Billings area, and the risk of future incidents — while managed — isn’t zero.
Coal Mining Legacy
The Billings area sits near significant coal deposits, and coal mining has been part of the regional economy for over a century. While large-scale surface mining is concentrated further east in the Powder River Basin, smaller historical coal operations near Billings have left their mark on local groundwater.
Coal mining can produce acidic drainage that mobilizes heavy metals like selenium, arsenic, and iron. In the Yellowstone Valley, some monitoring wells have shown elevated selenium levels associated with naturally occurring deposits and historical mining activity. Selenium is regulated by the EPA at 50 micrograms per liter in drinking water, and levels in Billings’ treated water have been within compliance.
The coal industry’s broader impact on Billings’ water is less about direct contamination and more about the cumulative effect of energy development on the Yellowstone Basin. Coal bed methane extraction, which boomed in Montana’s portion of the Powder River Basin in the 2000s, generated large volumes of produced water that was sometimes discharged into tributaries of the Yellowstone — raising concerns about sodium, TDS, and other constituents in the river system.
Agricultural Runoff
Agriculture is the dominant land use in the Yellowstone Valley surrounding Billings. Irrigated crops, dryland farming, and cattle ranching all contribute to nonpoint source pollution in the river and its tributaries.
Nitrate from fertilizer, bacteria from livestock operations, and sediment from eroding fields and streambanks all end up in the Yellowstone. During irrigation season, return flows from agricultural fields carry elevated levels of dissolved solids and agricultural chemicals back to the river.
Billings’ water treatment plant monitors for agricultural contaminants and consistently produces water that meets EPA standards. But the source water quality varies with season and weather, requiring the plant to adjust treatment in response to changing conditions.
What Billings Residents Can Do
Review the annual water quality report. The City of Billings publishes Consumer Confidence Reports with detailed contaminant data. It’s the best source for understanding what’s actually in your tap water.
If you’re on a private well, test annually for bacteria, nitrates, and any contaminants associated with your area’s land use history. Wells near former mining sites, agricultural land, or petroleum facilities should be tested for metals and hydrocarbons as well.
Flush your tap. If your home has older plumbing, run the cold water for 30 seconds to two minutes before drinking or cooking — especially first thing in the morning. This clears water that may have picked up lead or copper from aging pipes.
Consider point-of-use filtration. A good activated carbon filter removes chlorine taste and many organic contaminants. For more comprehensive protection — including nitrate and dissolved metals removal — a reverse osmosis system is the gold standard for residential treatment.
If you’re concerned about your water quality, a certified water treatment professional can test your water and advise on solutions.