01The verdict: is Eureka water safe?
Eureka's drinking water has significant quality concerns based on EPA testing data. With a grade of B (79.4/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 813 residents using surface water (rivers, lakes, or reservoirs).
Copper is over its legal limit
Measured at 2.00 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 ↓1 violation 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 ↓Eureka's drinking water received a grade of B (79.4 out of 100), indicating good water quality. The city's 1 water system serves approximately 813 residents using purchased 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 11 violations on record, including 4 health-based violations. 5 remain unresolved.
Eureka ranks #98 out of 137 cities in South Dakota for water quality, placing it below average 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. As a small community water system, Eureka may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
02What's in Eureka's water
Every contaminant flagged in Eureka, 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. | 2.00 | 1.3 | mg/L | Inorganic | Over Limit |
Cities ranked by 90th-percentile lead PF PFAS in South Dakota
Cities ranked by compounds detected Cu Copper in South Dakota
Cities ranked by 90th-percentile copper
03Eureka'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 11 violations on record, including 4 health-based violations. 5 remain unresolved.
8 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 7 ppb since 1993. Latest reading: 4 ppb (2024) — 27% of the action level. Sampled at higher-risk homes (90th percentile).
1.8mg/L(1995)
One sampling round on record — 142% of the 1.3mg/L EPA action level. Sampled at higher-risk homes (90th percentile).
04Where Eureka's water comes from
Eureka's drinking water comes primarily from surface water sources such as rivers, lakes, or reservoirs.
Purchased Surface Water
Rivers, lakes, or reservoirs — more exposed to runoff, agriculture, and seasonal swings than groundwater.
Wholesale supplier
Multi-barrier treatment: coagulation, sedimentation, filtration, and disinfection to meet EPA standards.
1 system
1 water system, operated under local government ownership.
813 people
Residents served across Eureka'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 813 people through 1 water system.
| System name | PWSID | Population | Source |
|---|---|---|---|
| EUREKA | SD4600121 | 813 | Purchased Surface Water |
05Pressure on Eureka'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
6 federal disaster declarations on record for McPherson County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
06How Eureka compares
Scores for nearby South Dakota cities on one line, with the average marked.
dashed line = South Dakota average (66/100)
Eureka scores 79.4/100 — above the South Dakota average of 66/100. It outscores 6 of 10 nearby cities. Full South Dakota rankings →
58.2 / 100FRapid City, SD
38.7 / 100FAberdeen, SD
41.8 / 100AWatertown, SD
91 / 100FPine Ridge, SD
43.2 / 100DBrookings, SD
46.2 / 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 Eureka'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 Eureka 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 Eureka, SD tap water safe to drink?
Eureka's water quality earned a grade of B (79.4/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #98 out of 137 cities tested in South Dakota.
What contaminants are in Eureka's water?
Lead was measured at 4.0 ppb (90th percentile). 11 violations are on record.
How is Eureka'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 Eureka?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Eureka's water come from?
Eureka's water is sourced from Purchased surface water. The city has 1 water system serving approximately 813 residents.
What health violations has Eureka's water system had?
Eureka has 4 health-based violations on record. The most recent violation was recorded in October 2023. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 5 violations remain unresolved.
How does Eureka's water compare to other cities?
Eureka ranks #98 out of 137 cities in South Dakota (better than 28% of state cities) and #8182 out of 15382 cities nationally (47th percentile). The grade of B reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Eureka's small water system affect quality?
Eureka's system serves approximately 813 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 11 violations on record.