Arsenic in Drinking Water in South Dakota
What residents of South Dakota need to know about arsenic in drinking water — including natural geological sources, private well risk, which utilities have documented violations, and how to remove arsenic from tap water.
Source: EPA SDWIS, South Dakota Department of Agriculture and Natural Resources, USGS · Last reviewed: 2025-01-01
Quick Answer
Is arsenic in drinking water a concern in South Dakota?
Yes. South Dakota has documented arsenic occurrence in the Cretaceous Pierre Shale aquifer system and in the Black Hills' crystalline and volcanic geology in western South Dakota. Multiple South Dakota public water systems have required arsenic treatment. The state's high private well dependency in agricultural areas and the widespread Cretaceous shale geology mean arsenic affects communities across a large portion of the state.
Where does arsenic come from in South Dakota's water?
The Cretaceous Pierre Shale and associated formations that underlie eastern and central South Dakota are the primary arsenic source for much of the state. In western South Dakota, Black Hills mining history (gold in Lead/Deadwood, silver elsewhere) and volcanic geology contribute arsenic from different pathways. The Ogallala Aquifer in southwestern South Dakota also has naturally elevated arsenic similar to Nebraska and Kansas.
What should South Dakota residents know?
Eastern and central South Dakota communities dependent on local groundwater from Cretaceous formations, western South Dakota private well owners near Black Hills mining areas, and Ogallala Aquifer-dependent communities in the southwestern corner of the state should test for arsenic. South Dakota DANR monitors public systems but private wells are unregulated.
Key Facts
| EPA MCL | 10 µg/L (10 ppb) |
| MCLG | Zero |
| Primary source | Cretaceous Pierre Shale (eastern/central SD); Black Hills mining legacy (western SD); Ogallala Aquifer (SW SD) |
| State regulator | South Dakota Department of Agriculture and Natural Resources (DANR) |
| Health effects | Bladder, lung, skin cancer; cardiovascular; diabetes risk |
| Effective treatment | Reverse osmosis (NSF/ANSI 58) or activated alumina |
Why Arsenic Matters in South Dakota
South Dakota's arsenic problem spans the state from east to west through different geological pathways. Eastern South Dakota's Pierre Shale arsenic is similar to North Dakota's, and has affected multiple small community water systems. The Black Hills' gold mining legacy in Lawrence and Pennington counties has added arsenic from Homestake Mine and other historic operations. South Dakota's significant agricultural private well population means a large number of rural residents may face unregulated arsenic exposure.
South Dakota Arsenic Program
South Dakota DANR monitors arsenic under federal SDWIS and has identified the glacial aquifer system and the Madison limestone aquifer in the Artesian Basin as zones with elevated arsenic. Several South Dakota small water systems required treatment after the 2006 MCL change. Private well owners drawing from the Madison aquifer in central South Dakota face the highest arsenic risk.
South Dakota Utilities With Arsenic Violation Records
The utilities listed below have at least one arsenic violation on record in EPA's SDWIS database. Violations may be open or resolved — see individual utility pages for current status and risk level.
How Does Arsenic Get Into Drinking Water?
Arsenic in drinking water is almost always naturally occurring — it leaches from arsenic-bearing rocks and minerals into groundwater over time. New England granite, Southwest volcanic geology, and Upper Midwest glacial aquifers are the primary high-risk formations. It has no taste, odor, or color.
Full arsenic overview — geology maps, health effects, all 50 statesWho Should Pay Closest Attention
Eastern South Dakota communities in Cretaceous shale counties (Gregory, Tripp, Mellette, Todd, Bennett, Lyman, Buffalo, Jerauld, Sanborn, Miner, Hanson), Black Hills area communities near mining districts in Lawrence and Pennington counties, and rural private well users throughout the state face the most relevant arsenic risk.
Private well owners near mining districts or agricultural areas
Residents in states with documented volcanic or geothermal geology
Long-term consumers of water from small groundwater systems
Households in homes built before 1960 with older well casings
Residents whose well water has never been tested for arsenic
Anyone living in a state where bedrock wells are common
How to Check Your Situation in South Dakota
- 1
Identify your water source. If you use a public utility, use the ZIP lookup on this page to find your system and check its compliance record.
- 2
If on public water, review your utility's most recent Consumer Confidence Report (CCR) for arsenic monitoring data. The MCL is 10 ppb — your report should show recent test results.
- 3
If on a private well, order an arsenic test from a South Dakota Department of Agriculture and Natural Resources-certified laboratory. A basic arsenic test costs $15–$40. The state agency website maintains a certified lab list.
- 4
Test your well at the tap — not just at the wellhead. The entire water distribution system within your home can affect water quality.
- 5
If your test shows arsenic above 5 ppb, install certified treatment immediately. If above 10 ppb, do not use the water for drinking or cooking until treatment is installed.
- 6
Retest after installing treatment to confirm it is working as certified. Replace filter media on the manufacturer's schedule — an exhausted filter may not perform as rated.
Treatment Options for Arsenic
Boiling does not remove arsenic — it concentrates it. Standard activated carbon filters (Brita, etc.) do not effectively remove arsenic. Certified treatment is required.
NSF/ANSI Standard 58 — Reverse Osmosis
RO systems certified to NSF/ANSI 58 remove 85–95% of arsenic. Under-sink installation. Most effective for removing multiple contaminants simultaneously. Replace membranes and pre-filters on schedule.
Activated Alumina Filters
Activated alumina is specifically designed for arsenic and fluoride removal. Point-of-use or whole-house options available. Must be certified by NSF International or WQA for arsenic reduction. Requires periodic media regeneration or replacement.
Iron/Manganese Oxidation Filters
Effective for arsenic in iron-rich well water, which is common in the Midwest and New England. Oxidation converts dissolved iron and arsenic to a form that can be filtered out. Best when arsenic is co-occurring with high iron levels.
What does NOT work for arsenic
Standard activated carbon filters (Brita, refrigerator filters, most pitcher filters) do NOT effectively remove arsenic. Boiling concentrates arsenic. Water softeners do not remove arsenic. Only use products with NSF certification specifically for arsenic reduction.
Take Action Now
If you use a private well in South Dakota, test for arsenic — especially if you are in a region with granite, volcanic, or sedimentary geology. A basic arsenic test costs $15–$40 at a state-certified lab.
Public water users: check your utility's Consumer Confidence Report (CCR) for arsenic results. The EPA MCL is 10 ppb — any detection warrants attention.
If arsenic is detected above 10 ppb (or even below it, given MCLG is zero), install an NSF/ANSI 58-certified reverse osmosis system for drinking and cooking water.
Standard carbon filters do NOT remove arsenic — do not rely on a Brita or refrigerator filter for arsenic protection.
Frequently Asked Questions
Related Pages
Arsenic — National Overview
All U.S. utilities with arsenic records
South Dakota State Overview
All utilities and water quality data
South Dakota Well Water Guide
Testing, risks & certified labs for private wells
Reverse Osmosis Guide
Removes 85–95% of arsenic
Best Arsenic Filter Guide
What actually works (carbon doesn't)
PFAS in Drinking Water
The 'forever chemical' contamination overview
All Contaminants
Complete reference library
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.