Is Boulder, MT Tap Water Safe to Drink?
Graded B+ — but Copper was detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
81.7/100
waterverge.com Boulder, MT — Water Quality Report
Boulder's drinking water received a grade of B+ (81.7 out of 100), indicating good water quality. The city's 1 water system serves approximately 1,400 residents using groundwater.
Lead levels were measured at 0.0 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program.
The system has 87 violations on record, including 6 health-based violations. 12 remain unresolved.
What to know about Boulder's water
Boulder ranks #33 out of 115 cities in Montana for water quality, placing it mid-range in the state.
Boulder relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff.
As a small community water system, Boulder may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Boulder, MT water safe to drink?
Boulder's drinking water has significant quality concerns based on EPA testing data. With a grade of B+ (81.7/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 1,400 residents using groundwater (wells).
Recent water quality updates for Boulder
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Boulder's water quality assessment. Grade: B+ (81.7/100).
Contaminants: TTHM, Total Haloacetic Acids (HAA5).
1 health-based. Contaminants: Surface Water Treatment Rule.
Contaminants: Revised Total Coliform Rule.
Federal disaster declaration (FEMA DR-4172). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-3253). Hurricane event — may have impacted local water infrastructure.
Key contaminant findings
Based on the most recent EPA sampling data for Boulder's water supply.
Well within EPA limits.
Exceeds EPA action level. Copper can leach from household plumbing — flush taps for 30 seconds before drinking.
Violation history
Boulder's water system has 87 total violations on record, including 6 health-based violations. 12 remain unresolved. 3 violations were issued in the last 5 years.
Flood & environmental risk
Jefferson County has experienced 4 federally declared disasters since 1975. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies. Local water sources include Boulder River Near Boulder.
Where does Boulder's water come from?
Boulder's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 1,400 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Boulder River Near Boulder (river).
What Boulder residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Boulder's water.
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Boulder's area has a history of flooding. After severe weather, watch for boil water advisories from your local utility.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Drought conditions
D2 — severe droughtJefferson County is currently in D2 (severe drought) per the U.S. Drought Monitor (week of May 5, 2026). Drought can elevate disinfection-byproduct (TTHM/HAA5) levels and taste/odor issues as utilities draw from lower reservoirs.
Source: U.S. Drought Monitor, updated weekly by NDMC, USDA, and NOAA.
Flood & disaster history
Jefferson County has experienced 4 federally declared disasters since 1975. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Recommended water filters
Based on contaminants detected in Boulder's water supply, we recommend the following filter types.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 0.0 | 15 | ppb | Inorganic | Safe |
| Copper (90th percentile) CopperInorganic A metal that enters drinking water mainly through corrosion of copper plumbing. Small amounts are essential for health, but excess levels are harmful. Health EffectsGastrointestinal distress (nausea, vomiting, diarrhea) at short-term high levels; liver and kidney damage from long-term exposure. EPA Limit1.3 mg/L action level Common SourcesCorrosion of copper household plumbing, erosion of natural deposits. | 1.40 | 1.3 | mg/L | Inorganic | Over Limit |
Lead level trend (90th percentile)
Copper level trend (90th percentile)
See how Boulder compares by contaminant
Explore where Boulder ranks among all Montana cities for specific contaminants.
Water source & infrastructure
Where Boulder's water comes from
Boulder's drinking water is drawn from underground aquifers through wells.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals.
Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds.
The system is operated by local government ownership and serves approximately 1,400 people through 1 water system.
Water bodies near Boulder
Boulder is located near 1 notable water body. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Boulder
| System Name | PWSID | Population | Source |
|---|---|---|---|
| BOULDER CITY OF | MT0000158 | 1,400 | GW |
How Boulder compares
Full Montana rankings →Boulder's score of 81.7/100 is above the average of 45/100 among major Montana cities. It outscores 9 of 10 nearby cities.
Nearby cities
View Montana rankings →About Boulder, MT
Wikipedia →Boulder is a town in and the county seat of Jefferson County, Montana, United States. It is on the north bank of the Boulder River between Butte and Helena, slightly east of the Continental Divide, at the intersection of Interstate 15 and Montana Highway 69. The population was 1,201 at the 2020 census. It is part of the Helena Micropolitan Statistical Area, which includes all of Lewis and Clark and Jefferson counties; its population is 83,058 according to the 2020 Census.
Learn more about your water
Guides and resources related to Boulder's water quality findings.
Explore water quality across Jefferson
Frequently asked questions
Is Boulder, MT tap water safe to drink?
Boulder's water quality earned a grade of B+ (81.7/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #33 out of 115 cities tested in Montana.
What contaminants are in Boulder's water?
Lead was measured at 0.0 ppb (90th percentile). 87 violations are on record.
How is Boulder's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Boulder?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Boulder's water come from?
Boulder's water is sourced from Groundwater. The city has 1 water system serving approximately 1,400 residents.
What health violations has Boulder's water system had?
Boulder has 6 health-based violations on record. The most recent violation was recorded in January 2024. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 12 violations remain unresolved.
Is Boulder's groundwater at risk of contamination?
Boulder uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 87 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Boulder's water compare to other cities?
Boulder ranks #33 out of 115 cities in Montana (better than 71% of state cities) and #7361 out of 15744 cities nationally (53th percentile). The grade of B+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Boulder's small water system affect quality?
Boulder's system serves approximately 1,400 residents. Small community water systems (under 3,300 people) may have fewer financial resources for infrastructure upgrades and advanced treatment technologies. However, they are held to the same EPA drinking water standards as larger systems. This system has 87 violations on record.