Billings is Montana’s largest city, home to about 120,000 people in the metro area, and it sits right along the Yellowstone River — the longest undammed river in the lower 48 states. It’s also the heart of Montana’s petroleum refining industry, with multiple refineries lining the corridor east of downtown. That combination of a major drinking water source and heavy industrial activity creates a water quality story worth understanding.
Refinery Row
The Billings area has been refining crude oil since the early 1900s. Today, two major refineries operate in the area: the CHS Laurel Refinery (technically in nearby Laurel) and the ExxonMobil Billings Refinery. Together, they process hundreds of thousands of barrels of crude oil daily, primarily from the Bakken formation in North Dakota and Montana, as well as Canadian sources delivered via pipeline.
Petroleum refining generates a range of contaminants that can affect water quality. The primary concerns include:
- Benzene, toluene, ethylbenzene, and xylene (BTEX) — volatile organic compounds that are components of petroleum and can contaminate groundwater
- Polycyclic aromatic hydrocarbons (PAHs) — formed during petroleum processing and combustion
- Heavy metals including lead, chromium, and vanadium
- Hydrogen sulfide and sulfur compounds — byproducts of refining sour crude
The Montana Department of Environmental Quality (DEQ) and the EPA regulate refinery discharges through the National Pollutant Discharge Elimination System (NPDES) permit program. Both refineries hold permits governing what they can discharge and at what concentrations.
Historical Contamination
The decades of refinery operation in Billings have left their mark on the local environment. The ExxonMobil Billings Refinery has an active groundwater remediation program addressing petroleum contamination in the shallow aquifer beneath and adjacent to the facility. According to Montana DEQ records, this remediation has been ongoing for years, with monitoring wells tracking the extent and concentration of contaminants in groundwater.
The Lockwood Solvent Groundwater Plume, located east of Billings in the Lockwood area, is another significant contamination site. While not exclusively refinery-related, this plume of chlorinated solvents — primarily trichloroethylene (TCE) and perchloroethylene (PCE) — contaminated private wells serving residential properties. The EPA conducted investigations and remediation, and affected residents were connected to public water supplies.
There’s also the legacy of the old Conoco refinery site (now inactive) and various pipeline incidents over the decades. In 2011, an ExxonMobil pipeline ruptured and spilled an estimated 63,000 gallons of crude oil into the Yellowstone River near Laurel, just upstream of Billings. While the acute contamination was addressed, pipeline spills are a recurring concern along the river corridor.
Billings’ Drinking Water
The City of Billings Public Utilities Department draws its drinking water from the Yellowstone River, treating it at the Billings Water Treatment Plant. The plant uses conventional treatment processes including coagulation, sedimentation, filtration, and disinfection.
According to the city’s Consumer Confidence Reports, Billings’ treated water meets all EPA primary drinking water standards. The utility tests for a broad range of contaminants including volatile organic compounds, inorganic chemicals, and disinfection byproducts.
One challenge specific to the Yellowstone River source is turbidity — cloudiness caused by suspended sediment. Spring runoff from snowmelt in the Yellowstone watershed can dramatically increase turbidity levels, requiring the treatment plant to adjust its processes. While turbidity itself isn’t a health hazard, it can interfere with disinfection effectiveness and sometimes triggers temporary boil advisories if treatment capacity is exceeded.
The city has invested significantly in treatment plant upgrades over the years to handle varying raw water quality. But the reality of drawing from a river that flows through agricultural land, past refineries, and through a growing urban area means the treatment plant has to deal with a complex mix of potential contaminants.
Groundwater Concerns
Not everyone in the Billings metro area is on public water. Residents in unincorporated Yellowstone County, particularly in areas like Lockwood, the Heights, and rural communities south and west of town, may rely on private wells.
Montana’s groundwater quality varies significantly by location. The shallow alluvial aquifer along the Yellowstone River is vulnerable to contamination from surface activities — including agricultural chemicals, septic systems, and industrial operations. Deeper aquifers generally offer better protection but aren’t available everywhere.
The USGS has conducted groundwater studies in the Yellowstone River valley that document the hydrogeology and water quality of the area’s aquifer systems. These studies have found that shallow groundwater near the river tends to reflect surface water quality, while deeper aquifers have different chemical signatures.
For private well owners, the key concern is proximity to known contamination sources. If you’re within a few miles of the refinery corridor and drawing from a shallow well, testing is especially important.
Agricultural Influences
Billings isn’t just a refinery town — it’s also surrounded by irrigated farmland and rangeland. The Yellowstone River valley upstream of Billings supports significant agriculture, and the contributions of farm and ranch operations to water quality shouldn’t be overlooked.
Nitrates from fertilizer application and livestock operations can leach into groundwater. Montana DEQ has documented elevated nitrate levels in some shallow wells in the Yellowstone County area, particularly in agricultural zones. The EPA’s maximum contaminant level for nitrates is 10 mg/L, and levels approaching that threshold have been found in some private wells.
Pesticides and herbicides used in crop production can also reach groundwater, though detection in Montana’s deeper aquifers has been relatively limited based on USGS monitoring data.
Sediment and nutrient runoff from agricultural land contributes to the Yellowstone River’s water quality challenges, particularly during spring runoff and heavy rain events.
What the Data Shows
Looking at EPA compliance data for Billings’ public water system, the city has maintained a strong compliance record with Safe Drinking Water Act standards. Monitoring data shows:
- Disinfection byproducts (trihalomethanes and haloacetic acids) are detected but remain below MCLs
- No MCL violations for VOCs or petroleum-related compounds in treated water
- Nitrate levels in treated water are well below the MCL
- Lead and copper testing under the Lead and Copper Rule has not triggered action level exceedances in recent testing rounds
The EWG Tap Water Database notes the presence of various contaminants detected at levels below legal limits but above EWG’s more stringent health guidelines. This is common across most US water systems — EWG’s benchmarks are based on the latest health research and are often significantly lower than enforceable EPA standards.
What Residents Can Do
If you’re on Billings public water:
- Review the annual Consumer Confidence Report from Billings Public Utilities. It details what was tested and what was found.
- If you live in an older home (pre-1986), consider testing for lead at your tap. Lead contamination typically comes from household plumbing, not the water source itself.
- A point-of-use filter certified for your contaminants of concern can provide an additional layer of protection.
If you’re on a private well:
- Test annually for bacteria (total coliform and E. coli), nitrates, and basic water chemistry.
- If you’re near the refinery corridor or known contamination sites, add VOC testing to your panel. Ask your lab specifically about BTEX compounds.
- Montana DEQ’s Ground Water Assessment Program can provide information about groundwater quality in your area.
- If you’re in the Lockwood area, check with the county about connection to public water if you haven’t already.
Water Treatment Options
For petroleum-related contaminants like BTEX compounds:
Activated carbon filtration is effective at removing many VOCs including benzene and other petroleum compounds. Both whole-house and point-of-use systems are available. Look for NSF/ANSI 53 certification for VOC removal.
Air stripping can remove volatile compounds from water by exposing it to air, which causes VOCs to evaporate. This is more commonly a municipal-scale treatment but point-of-entry systems exist for residential use.
Reverse osmosis removes a broad range of contaminants including heavy metals, nitrates, and some organic compounds.
For nitrate contamination, reverse osmosis and ion exchange systems are the most effective residential treatment options. Standard carbon filters don’t remove nitrates.
The Yellowstone River is a remarkable water resource — but sharing a watershed with refineries, farms, and a growing city means treatment and testing aren’t optional. They’re how Billings residents ensure that remarkable resource stays safe to drink.
If you’re concerned about your water quality, a certified water treatment professional can test your water and advise on solutions.