PlainEnviro

Health-Based Drinking Water Violation Records by State and Category

206,335 health-based violation records joined to 49,190 active community water systems, with Texas holding the largest raw count (35,614 - 17.3% of this extract). Source: EPA SDWIS.

Research period:

Research Question

Where do health-based EPA Safe Drinking Water violation records in PlainEnviro's extract concentrate by state, and which health-based regulatory categories account for the largest share?

Methodology

The upstream fetch requests only VIOLATION records where EPA's IS_HEALTH_BASED_IND equals Y. Those rows are joined by PWSID to PlainEnviro's active community-water-system inventory and grouped by state. State totals are stored in precomputed.json under states[].num_violations; the category chart queries the same joined scope at request time. Contaminants remain exact EPA codes because this extract does not carry authoritative contaminant names.

Findings

Top 12 states by health-based SDWIS record count

health-based records

What this shows Raw record totals mix system-inventory size, historical duration, compliance status, and water-quality conditions; counts alone do not rank one state's water as safer than another's.

Source EPA Safe Drinking Water Information System Federal Reports As of current quarter

Violation category breakdown (national)

MCL = Maximum Contaminant Level exceedance; TT = Treatment Technique failure; MRDL = Maximum Residual Disinfectant Level

health-based records

What this shows This chart describes the health-based records in the joined extract only; it excludes monitoring and reporting records.

Source EPA SDWIS water_violations table aggregated As of current quarter

National scope

PlainEnviro's active community-water-system inventory contains 49,190 systems. Its health-based SDWIS extract has 206,335 joined violation records across the historical periods present in the database. The fetch is restricted upstream to records EPA flags as health-based; monitoring and reporting violations are not included.

Top 12 states by health-based SDWIS record count

State-level concentration is highly skewed. Texas alone accounts for 17.3% of the joined health-based records in this extract (35,614 of 206,335), followed by Oklahoma with 29,183 (14.1%). The top 12 states together account for the large majority of recorded SDWIS violations.

Rank State Health-based records Water systems Share of US total
1 Texas (TX) 35,614 4,587 17.3%
2 Oklahoma (OK) 29,183 883 14.1%
3 California (CA) 18,087 3,077 8.8%
4 Louisiana (LA) 14,611 835 7.1%
5 New Mexico (NM) 8,105 590 3.9%
6 Missouri (MO) 6,530 1,666 3.2%
7 Arkansas (AR) 5,991 667 2.9%
8 Colorado (CO) 5,562 1,109 2.7%
9 New York (NY) 5,526 2,201 2.7%
10 Pennsylvania (PA) 5,368 1,787 2.6%
11 Arizona (AZ) 5,174 956 2.5%
12 Alaska (AK) 4,828 404 2.3%

Source: PlainEnviro aggregation of the EPA SDWIS health-based extract joined to active community water systems. Each row links to the full state environmental profile; see the methodology above for scope and limitations.

How to read state-level differences

Cross-state record counts mix several signals that need separating before drawing conclusions about drinking water safety:

  1. Inventory size. Texas has roughly 4,587 regulated water systems (largest in the US); Oklahoma operates a smaller inventory but with high violation density per system. Per-system normalization is essential before claiming one state's water is "worse" than another's.
  2. Historical duration and status. A state total can contain multiple periods for the same system, including records that later returned to compliance.
  3. Population structure. A raw count does not distinguish a small system from one serving a large population, so it should not be interpreted as population risk.

Why this matters for community health

MCL records indicate that a regulated contaminant exceeded an enforceable threshold during the applicable compliance period. Treatment-technique records concern a required treatment process, and MRDL records concern a maximum residual disinfectant level. The chart above computes the category split directly from the current joined extract. A historical record alone does not establish that water delivered today is unsafe.

What this analysis cannot tell us

This is a historical health-based record count, not a current safety or compliance score. Monitoring and reporting violations are absent from the extract. Counts are not normalized for population, number or size of systems, violation duration, severity, reporting practice, or return-to-compliance status. The active-community-system join excludes records that do not match that inventory, and private wells are outside SDWIS jurisdiction.

Glossary of regulatory terminology

Maximum Contaminant Level (MCL)
Enforceable health-based ceiling concentration set under Safe Drinking Water Act section 1412, factoring analytical detection capability, treatment feasibility, and benefit-cost considerations alongside protective health benchmarks.
Maximum Contaminant Level Goal (MCLG)
Aspirational non-enforceable concentration at which no known or anticipated adverse health effects occur, allowing an adequate margin of safety. MCLGs for known carcinogens are typically zero.
Treatment Technique (TT)
Required process or procedure (rather than a numerical concentration limit) used when accurate measurement of a contaminant is infeasible. Examples include the Surface Water Treatment Rule's filtration and disinfection requirements.
Tier classification
Three-level public notification scheme: Tier 1 acute violations require immediate notice within 24 hours, Tier 2 requires notification within 30 days for non-acute violations posing health concerns, Tier 3 covers monitoring violations resolved through annual Consumer Confidence Reports.
Action Level (AL)
Lead and Copper Rule construct triggering corrosion control treatment, source water review, and public education when 10 percent of household tap samples exceed the established threshold (15 micrograms per liter for lead, 1.3 milligrams per liter for copper).

Discussion: Safe Drinking Water Act enforcement, contaminant classification, regulatory adequacy

The Safe Drinking Water Act of 1974 established the federal framework for regulating public water systems and the contaminants present in their distributed drinking water. The Environmental Protection Agency promulgates Maximum Contaminant Levels (MCLs) under SDWA Section 1412, enforceable standards that water systems serving more than twenty-five people for more than sixty days per year must meet. Maximum Contaminant Level Goals (MCLGs) - non-enforceable health-based aspirational targets, are typically set lower than MCLs because of treatment-feasibility constraints and analytical detection limits. The 1996 amendments introduced the Contaminant Candidate List process and required risk-based prioritization, with Unregulated Contaminant Monitoring Rule cycles every five years informing future regulatory decisions.

Violations fall into three principal categories: maximum contaminant level (MCL) violations involving exceedances of the regulatory standard; treatment technique violations for failures to apply required treatment processes such as filtration or disinfection; and monitoring and reporting violations covering procedural lapses. EPA's Safe Drinking Water Information System (SDWIS) tracks these classifications, with Tier 1 (immediate notice required), Tier 2 (notice within thirty days), and Tier 3 (annual report) public notification requirements scaled to acute health risk. Researchers including Maura Allaire at UC Irvine have shown that small water systems serving fewer than three thousand three hundred residents account for a disproportionate share of recurring violations, primarily because of constrained operator capacity and aging infrastructure.

The arsenic standard reduction from fifty to ten parts per billion in 2006 illustrates the tension between health-based standards and economic feasibility, implementation costs disproportionately fell on small Western and Northeastern systems serving low-income communities. Lead and Copper Rule revisions finalized in 2021 introduced lead service line inventory requirements and revised trigger levels, but full lead service line replacement timelines extend through 2037 under current regulations. The PFAS regulatory landscape evolved dramatically in 2024 when EPA finalized National Primary Drinking Water Regulations for six PFAS compounds, marking the first new federal MCLs since the 1996 SDWA amendments.

Related data on PlainEnviro

Sources