01The verdict: is St Maries water safe?
St Maries's drinking water has significant quality concerns based on EPA testing data. With a grade of B- (73.3/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 5 water systems serve approximately 4,561 residents using surface water (rivers, lakes, or reservoirs).
Copper is over its legal limit
Measured at 1.74 mg/L against the EPA Action Level of 1.3 mg/L. The ledger below shows how far over — and which filter removes it.
See the measurement ↓Lead is well under the limit
90th-percentile lead is 4.0 ppb — beneath the 15 ppb federal action level and under the 5 ppb watch threshold.
See the trend ↓2 violations in the last five years
Recent compliance history is the best predictor of future problems — the year-by-year record is below.
See the record ↓St Maries's drinking water received a grade of B- (73.3 out of 100), indicating fair water quality. The city's 5 water systems serve approximately 4,561 residents using surface water.
Lead levels were measured at 4.0 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 129 violations on record, including 17 health-based violations. 11 remain unresolved.
St Maries ranks #70 out of 139 cities in Idaho for water quality, placing it mid-range in the state. The city draws from surface water sources, which are more susceptible to seasonal runoff and agricultural contamination, requiring extensive multi-barrier treatment including coagulation, filtration, and disinfection.
02What's in St Maries's water
Every contaminant flagged in St Maries, on one shared scale: distance to its own legal limit. The red line is the limit — anything past it is out of compliance, and the closer a bar gets, the less headroom the system has.
Over Limit — EPA Action Level: 1.3 mg/L
Exceeds the EPA action level. Copper leaches from household plumbing — flush taps for 30 seconds before drinking, and consider a certified filter.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. | 4.0 | 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. | 1.74 | 1.3 | mg/L | Inorganic | Over Limit |
Cities ranked by 90th-percentile lead PF PFAS in Idaho
Cities ranked by compounds detected Cu Copper in Idaho
Cities ranked by 90th-percentile copper
03St Maries's ten-year track record
Each box is one year. A green check means no EPA violations; a numbered badge counts that year's violations — red if any were health-based, amber if they were monitoring or paperwork issues. The system has 129 violations on record, including 17 health-based violations. 11 remain unresolved.
5 of the last ten years were clean. The numbered years had EPA violations — red when any were health-based, amber when they were paperwork or missed-testing issues.
▼ Down 9 ppb since 1998. Latest reading: 1 ppb (2025) — 7% of the action level. Sampled at higher-risk homes (90th percentile).
▼ Down 0 mg/L since 2003. The latest reading (1.7 mg/L, 2004) is over the action level. Sampled at higher-risk homes (90th percentile).
04Where St Maries's water comes from
St Maries's drinking water comes primarily from surface water sources such as rivers, lakes, or reservoirs.
Surface Water
Rivers, lakes, or reservoirs — more exposed to runoff, agriculture, and seasonal swings than groundwater.
Local treatment
Multi-barrier treatment: coagulation, sedimentation, filtration, and disinfection to meet EPA standards.
5 systems
5 water systems, operated under local government ownership.
4,561 people
Residents served across St Maries's service area.
Surface water systems require multi-stage treatment including coagulation, sedimentation, filtration, and disinfection to meet EPA Safe Drinking Water Act standards. These sources can be impacted by seasonal changes, stormwater runoff, upstream agriculture, and industrial discharge. The system is operated by local government ownership and serves approximately 4,561 people through 5 water systems.
| System name | PWSID | Population | Source |
|---|---|---|---|
| ST MARIES CITY OF | ID1050024 | 4,173 | Surface Water |
| COTTONWOOD POINT WATER ASSN | ID1050008 | 151 | Groundwater |
| EMIDA WATER AND SEWER ASSOCIATION | ID1050009 | 95 | Groundwater |
| EVERGREEN TERRACE WATER ASSOCIATION | ID1050010 | 85 | Groundwater |
| CASSANDRA HILLS OWNERS ASSN | ID1050004 | 57 | Groundwater |
Water bodies near St Maries
As a surface-water system, these water bodies may directly influence St Maries's drinking water supply.
05Pressure on St Maries's watershed
Outside forces that shape what reaches the treatment plant. None of these is a verdict on the tap by itself — but each adds pressure worth knowing about.
Flood & storm history
4 federal disaster declarations on record for Benewah County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
Drought
Benewah County is in D2 (severe drought) per the U.S. Drought Monitor (week of Jul 2026). Drought can raise disinfection-byproduct levels and taste/odor issues as utilities draw from lower reservoirs.
06How St Maries compares
Scores for nearby Idaho cities on one line, with the average marked.
dashed line = Idaho average (43/100)
St Maries scores 73.3/100 — above the Idaho average of 43/100. It outscores 10 of 10 nearby cities. Full Idaho rankings →
33.6 / 100FMeridian, ID
42.9 / 100FNampa, ID
41.8 / 100DIdaho Falls, ID
46.6 / 100FCaldwell, ID
38.5 / 100FPocatello, ID
42.5 / 100
Compare all cities in the county — grades, violations, and contaminant data side by side.→
07What to do at home
Steps matched to what testing actually found in St Maries's water — not generic advice.
Filter drinking & cooking water
NSF-certified water filter. Copper exceeds the EPA action level of 1.3 mg/L
Compare tested filters →Flush taps & check your service line
Lead leaches from pipes as water sits. Run cold water 30 seconds before drinking (especially mornings), and ask the utility whether your address still has a lead service line.
Lead risks explained →Watch for St Maries alerts
This area has a history of flood declarations — after severe weather, watch for boil-water advisories from the utility, and check the live alerts on this page.
All water alerts →Frequently asked questions
Is St Maries, ID tap water safe to drink?
St Maries's water quality earned a grade of B- (73.3/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #70 out of 139 cities tested in Idaho.
What contaminants are in St Maries's water?
Lead was measured at 4.0 ppb (90th percentile). 129 violations are on record.
How is St Maries'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 St Maries?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does St Maries's water come from?
St Maries's water is sourced from Surface water. The city has 5 water systems serving approximately 4,561 residents.
What health violations has St Maries's water system had?
St Maries has 17 health-based violations on record. The most recent violation was recorded in April 2024. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 11 violations remain unresolved.
How does St Maries's water compare to other cities?
St Maries ranks #70 out of 139 cities in Idaho (better than 50% of state cities) and #9970 out of 15382 cities nationally (35th percentile). The grade of B- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.