01The verdict: is Fort Thompson water safe?
Fort Thompson's drinking water has significant quality concerns based on EPA testing data. With a grade of C (64.8/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 3 water systems serve approximately 1,567 residents using surface water (rivers, lakes, or reservoirs).
16 unresolved violations on record
EPA records show open compliance items for this system. Most are administrative, but unresolved items are worth watching.
See what was cited ↓Lead is well under the limit
90th-percentile lead is 0.2 ppb — beneath the 15 ppb federal action level and under the 5 ppb watch threshold.
See the trend ↓13 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 ↓Fort Thompson's drinking water received a grade of C (64.8 out of 100), indicating fair water quality. The city's 3 water systems serve approximately 1,567 residents using surface water.
Lead levels were measured at 0.2 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 351 violations on record, including 17 health-based violations. 16 remain unresolved.
Fort Thompson ranks #119 out of 137 cities in South Dakota for water quality, placing it among the lowest-rated 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, Fort Thompson may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities. The system has seen 13 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
02What's in Fort Thompson's water
Every contaminant flagged in Fort Thompson, 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.
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. | 0.2 | 15 | ppb | Inorganic | Safe |
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
03Fort Thompson'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 351 violations on record, including 17 health-based violations. 16 remain unresolved.
4 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 2.3 ppb since 2004. Latest reading: 0.66 ppb (2025) — 4% of the action level. Sampled at higher-risk homes (90th percentile).
04Where Fort Thompson's water comes from
Fort Thompson'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.
3 systems
3 water systems (1 wholesaler), operated under native american ownership.
1,567 people
Residents served across Fort Thompson'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 native american ownership and serves approximately 1,567 people through 3 water systems.
| System name | PWSID | Population | Source |
|---|---|---|---|
| FORT THOMPSON WATER SYSTEM | 084690440 | 1,357 | Surface Water |
| CROW CREEK SIOUX TRIBE WATER SYSTEM | 084690439 | 130 | Purchased Surface Water |
| BIG BEND WATER SYSTEM | 084690438 | 80 | Groundwater |
Water bodies near Fort Thompson
As a surface-water system, these water bodies may directly influence Fort Thompson's drinking water supply.
05Pressure on Fort Thompson'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
9 federal disaster declarations on record for Buffalo County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
06How Fort Thompson compares
Scores for nearby South Dakota cities on one line, with the average marked.
dashed line = South Dakota average (66/100)
Fort Thompson scores 64.8/100 — on par with the South Dakota average of 66/100. It outscores 5 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
07What to do at home
Steps matched to what testing actually found in Fort Thompson's water — not generic advice.
A basic carbon filter still helps
Fort Thompson's water meets federal standards, but a simple carbon filter improves taste and adds a margin of safety against short-term issues.
Compare tested filters →Read your utility's annual report
Every utility must publish a yearly Consumer Confidence Report with its own testing results. It pairs well with the independent data on this page.
How to read a CCR →Watch for Fort Thompson 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 Fort Thompson, SD tap water safe to drink?
Fort Thompson's water quality earned a grade of C (64.8/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #119 out of 137 cities tested in South Dakota.
What contaminants are in Fort Thompson's water?
Lead was measured at 0.2 ppb (90th percentile). 351 violations are on record.
How is Fort Thompson'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 Fort Thompson?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Fort Thompson's water come from?
Fort Thompson's water is sourced from Surface water. The city has 3 water systems serving approximately 1,567 residents.
What health violations has Fort Thompson's water system had?
Fort Thompson has 17 health-based violations on record. The most recent violation was recorded in January 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 16 violations remain unresolved.
How does Fort Thompson's water compare to other cities?
Fort Thompson ranks #119 out of 137 cities in South Dakota (better than 13% of state cities) and #11437 out of 15382 cities nationally (26th percentile). The grade of C reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.