Public water system · SD4600229
ActiveOacoma
At a glance
Oacoma (PWSID SD4600229) is an active community water system in Lyman County, South Dakota. It reports serving 391 people through 190 service connections. Its primary water source is surface water, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, 10 are health-based, and the most recent began in June 2014.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
391
Service connections
190
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does Oacoma compare with other water systems in Lyman County?
By EPA's size categories, Oacoma is a very small system (500 people or fewer). Lyman County has 3 active public water systems, and Oacoma is the 2nd-largest of them by population served. Its population served is roughly in line with the county average of 376 people per system, and accounts for 35% of the 1,128 people reported by systems filed under the county. Across South Dakota, the 699 active systems average 1,387 people each. Nationally, the average active community water system reports serving 6,703 people, so Oacoma is well below that figure.
What does “community water system” mean?
A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. South Dakota has 510 active community water systems, 73% of the state's 699 active systems. Surface water means the system draws its water from rivers, lakes, streams or reservoirs. 24 South Dakota systems (3.4%) list surface water as their primary source.
Who owns and regulates Oacoma?
EPA lists Oacoma as owned by a local government. The SD state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 3 of the 3 active systems in Lyman County (100%) are also owned by a local government.
Does Oacoma have drinking water violations?
Of the 12 most recent violations in EPA's records, 10 are health-based, and the most recent began in June 2014. The violations listed here began between October 2004 and June 2014. By type: 8 contaminant level above the legal limit, 2 public notice, recordkeeping or other and 2 required treatment not met. The contaminant or rule involved most often is Total trihalomethanes (TTHM) (6 of them). EPA lists 12 as resolved. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2014-06-14 | Public notice, recordkeeping or otherSanitary Survey (TCR) · code 28 | Not reported | No | Resolved |
| 2013-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2013-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2012-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2012-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Haloacetic acids (HAA5)code 2456 | Yes | Resolved |
| 2012-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2012-04-01 | Required treatment not metTreatment Technique Precursor Removal · code 46 | Carbon, totalcode 2920 | Yes | Resolved |
| 2012-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2012-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Haloacetic acids (HAA5)code 2456 | Yes | Resolved |
| 2012-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2011-06-25 | Public notice, recordkeeping or otherSanitary Survey (TCR) · code 28 | Not reported | No | Resolved |
| 2004-10-01 | Required treatment not metTreatment Technique Precursor Removal · code 46 | Carbon, totalcode 2920 | Yes | Resolved |
The 12 most recent violations in EPA's records, newest first.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
Oacoma: frequently asked questions
Who runs Oacoma?
Oacoma (PWSID SD4600229) is a community water system owned by a local government. It is regulated by the SD state drinking water program.
How many people does Oacoma serve?
Oacoma reports serving 391 people through 190 service connections in Lyman County, South Dakota.
Where does Oacoma get its water?
EPA SDWIS lists this system's primary water source as surface water. Surface water means the system draws its water from rivers, lakes, streams or reservoirs.
Does Oacoma have any drinking water violations?
Of the 12 most recent violations in EPA's records, 10 are health-based, and the most recent began in June 2014. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is Oacoma's water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. Of the 12 most recent violations in EPA's records, 10 are health-based, and the most recent began in June 2014. For current results, consult the system's annual water quality report, EPA ECHO, or the SD state drinking water program.
Where can I find Oacoma's water quality report?
As a community water system, Oacoma must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in Lyman County
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About this data
Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.
Cite as: AquaCensus, “Oacoma, PWSID SD4600229, South Dakota”, https://aquacensus.com/water-systems/south-dakota/oacoma-sd4600229 (data as of October 1, 2026).