We analyzed tap water quality data for hundreds of cities in South Dakota to identify the 25 with the most contaminants exceeding health guidelines. This ranking is based on 2026 data from the EPA and EWG databases.
While all public water systems must meet EPA legal limits, many health experts — including the Environmental Working Group — argue that these legal limits are outdated and don't reflect current scientific understanding of safe exposure levels. The cities below have the widest gap between what's in their water and what's considered safe by modern health standards.
Rankings at a Glance
Hudson, South Dakota
Hudson has 13 contaminants exceeding EWG health guidelines out of 22 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Hudson water report →Ellsworth Afb, South Dakota
Ellsworth Afb has 7 contaminants exceeding EWG health guidelines out of 17 total detected, placing it among the most concerning water supplies analyzed.
See full Ellsworth Afb water report →Rapid City, South Dakota
Rapid City has 7 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Rapid City water report →Bison, South Dakota
Bison has 7 contaminants exceeding EWG health guidelines out of 9 total detected, placing it among the most concerning water supplies analyzed.
See full Bison water report →Sioux Falls, South Dakota
Sioux Falls has 6 contaminants exceeding EWG health guidelines out of 14 total detected, placing it among the most concerning water supplies analyzed.
See full Sioux Falls water report →Aberdeen, South Dakota
Aberdeen has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Aberdeen water report →Pierre, South Dakota
Pierre has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Pierre water report →Webster, South Dakota
Webster has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Webster water report →Groton, South Dakota
Groton has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Groton water report →Ipswich, South Dakota
Ipswich has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Ipswich water report →Eureka, South Dakota
Eureka has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Eureka water report →Warner, South Dakota
Warner has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Warner water report →Leola, South Dakota
Leola has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Leola water report →Herreid, South Dakota
Herreid has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Herreid water report →Bristol, South Dakota
Bristol has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Bristol water report →Frederick, South Dakota
Frederick has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Frederick water report →Roslyn, South Dakota
Roslyn has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Roslyn water report →Conde, South Dakota
Conde has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Conde water report →Eden, South Dakota
Eden has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Eden water report →Bath, South Dakota
Bath has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Bath water report →Grenville, South Dakota
Grenville has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Grenville water report →Doland, South Dakota
Doland has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Doland water report →Bowdle, South Dakota
Bowdle has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Bowdle water report →Java, South Dakota
Java has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Java water report →Redfield, South Dakota
Redfield has 5 contaminants exceeding EWG health guidelines out of 16 total detected, placing it among the most concerning water supplies analyzed.
See full Redfield water report →What We Found: Key Patterns
The most frequently detected contaminants exceeding health guidelines across these cities are Haloacetic acids (HAA5), Total trihalomethanes (TTHMs), Nitrate*. These appear repeatedly across different water systems and regions.
Water quality varies significantly even within the same state, driven by local geology, agricultural activity, and industrial proximity.
Across all ranked cities, 140 contaminant readings exceed EWG health guidelines, but only 0 exceed EPA legal limits. This gap of 140 highlights how legal standards may not fully protect public health — EPA limits haven't been updated for many contaminants in decades.
Full Rankings Table
| Rank | City | State | Detected | Above Guidelines | Above Legal | People Served |
|---|---|---|---|---|---|---|
| 1 | Hudson | SD | 22 | 13 | 0 | 369 |
| 2 | Ellsworth Afb | SD | 17 | 7 | 0 | 0 |
| 3 | Rapid City | SD | 16 | 7 | 0 | 78,836 |
| 4 | Bison | SD | 9 | 7 | 0 | 470 |
| 5 | Sioux Falls | SD | 14 | 6 | 0 | 201,650 |
| 6 | Aberdeen | SD | 16 | 5 | 0 | 31,822 |
| 7 | Pierre | SD | 16 | 5 | 0 | 14,091 |
| 8 | Webster | SD | 16 | 5 | 0 | 1,696 |
| 9 | Groton | SD | 16 | 5 | 0 | 1,380 |
| 10 | Ipswich | SD | 16 | 5 | 0 | 928 |
| 11 | Eureka | SD | 16 | 5 | 0 | 814 |
| 12 | Warner | SD | 16 | 5 | 0 | 452 |
| 13 | Leola | SD | 16 | 5 | 0 | 434 |
| 14 | Herreid | SD | 16 | 5 | 0 | 424 |
| 15 | Bristol | SD | 16 | 5 | 0 | 288 |
| 16 | Frederick | SD | 16 | 5 | 0 | 215 |
| 17 | Roslyn | SD | 16 | 5 | 0 | 162 |
| 18 | Conde | SD | 16 | 5 | 0 | 135 |
| 19 | Eden | SD | 16 | 5 | 0 | 99 |
| 20 | Bath | SD | 16 | 5 | 0 | 75 |
| 21 | Grenville | SD | 16 | 5 | 0 | 48 |
| 22 | Doland | SD | 16 | 5 | 0 | 0 |
| 23 | Bowdle | SD | 16 | 5 | 0 | 0 |
| 24 | Java | SD | 16 | 5 | 0 | 0 |
| 25 | Redfield | SD | 16 | 5 | 0 | 0 |
Frequently Asked Questions
What city has the worst tap water in South Dakota?
Based on 2026 data, Hudson, SD has the most contaminants exceeding EWG health guidelines among the cities we analyzed.
How are cities ranked in this report?
Cities are ranked by the number of contaminants exceeding EWG health guidelines. These guidelines are typically stricter than EPA legal limits and reflect current scientific research on safe exposure levels.
Is my tap water safe if my city isn't on this list?
Not necessarily. Even cities not on this list may have contaminants of concern. We recommend checking your specific water quality using our free water scan tool.
What's the best water filter for contaminated water?
A reverse osmosis (RO) system is the most effective for removing the widest range of contaminants. For whole-home protection, a combination of RO for drinking water and a whole-home filter for showers and baths is recommended.
Related Reports
Data sources: Environmental Working Group (EWG) Tap Water Database, U.S. EPA Safe Drinking Water Information System (SDWIS)
Last updated: April 2026
Methodology: Contaminant levels are compared against both EPA legal limits (Maximum Contaminant Levels) and EWG health guidelines, which are often stricter and based on the latest scientific research.
