Arizona · drinking water · SDWIS through latest publish

Epcor - San Tan Water Quality — San Tan Valley, Arizona

PWSID AZ0411128 · GroundwaterPrivate

87,435 people served. No health-based SDWIS violations recorded in the past 5 years. 2 remain unresolved. Last cited 2 years ago.

ALL SDWIS VIOLATIONS · 20202026 (annual count)
Bar chart of annual values from 2020 to 2026, in violations. Most recent year (2026): 0 violations.56 violations'20'21'22'23'24'25'260 violations
Anomaly engine

Active signals

UNRESOLVED VIOLATION · SDWIS VIOLATION

Chlorine

Unresolved Disinfectants and Disinfection Byproducts (Stage 2) violation cited in 2024 (chlorine).

EPA SDWIS record

UNRESOLVED VIOLATION · SDWIS VIOLATION

Chlorine

Unresolved Disinfectants and Disinfection Byproducts (Stage 2) violation cited in 2024 (chlorine).

EPA SDWIS record

Most-cited contaminants

What This Utility Gets Cited For

  • Beryllium14 citations
  • Chlorine11 citations
  • Xylenes (total)2 citations
  • Benzene2 citations
  • Contaminant 29552 citations
  • Contaminant 29642 citations
Violation history

What's On The SDWIS Record

Health-based violations exceed an MCL or treatment-technique standard. Monitoring violations are reporting failures with no measured exceedance — they tell you the system isn't fully transparent, not that the water is unsafe today.

MONITORING · CHLORINE

2024 · Chlorine · Disinfectants and Disinfection Byproducts (Stage 2)

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 0999

MONITORING · CHLORINEUNRESOLVED

2024 · Chlorine · Disinfectants and Disinfection Byproducts (Stage 2)

Failure to monitor as scheduled

CONTAMINANT CODE 0999

MONITORING · CHLORINE

2024 · Chlorine · Disinfectants and Disinfection Byproducts (Stage 2)

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 0999

MONITORING · CHLORINE

2024 · Chlorine · Disinfectants and Disinfection Byproducts (Stage 2)

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 0999

MONITORING · CHLORINEUNRESOLVED

2024 · Chlorine · Disinfectants and Disinfection Byproducts (Stage 2)

Failure to monitor as scheduled

CONTAMINANT CODE 0999

MONITORING · CHLORINE

2024 · Chlorine · Disinfectants and Disinfection Byproducts (Stage 2)

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 0999

MONITORING · CHLORINE

2024 · Chlorine · Disinfectants and Disinfection Byproducts (Stage 2)

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 0999

MONITORING · CHLORINE

2024 · Chlorine · Disinfectants and Disinfection Byproducts (Stage 2)

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 0999

MONITORING · BERYLLIUM

2024 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · BERYLLIUM

2024 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · BERYLLIUM

2024 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · BERYLLIUM

2024 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · XYLENES (TOTAL)

2024 · Xylenes (total) · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2378

MONITORING · XYLENES (TOTAL)

2024 · Xylenes (total) · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2378

MONITORING · BENZENE

2024 · Benzene · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2380

MONITORING · BENZENE

2024 · Benzene · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2380

MONITORING · CONTAMINANT 2955

2024 · Contaminant 2955 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2955

MONITORING · CONTAMINANT 2955

2024 · Contaminant 2955 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2955

MONITORING · CONTAMINANT 2964

2024 · Contaminant 2964 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2964

MONITORING · CONTAMINANT 2964

2024 · Contaminant 2964 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2964

MONITORING · CONTAMINANT 2968

2024 · Contaminant 2968 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2968

MONITORING · CONTAMINANT 2968

2024 · Contaminant 2968 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2968

MONITORING · CONTAMINANT 2969

2024 · Contaminant 2969 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2969

MONITORING · CONTAMINANT 2969

2024 · Contaminant 2969 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2969

MONITORING · CONTAMINANT 2977

2024 · Contaminant 2977 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2977

MONITORING · CONTAMINANT 2977

2024 · Contaminant 2977 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2977

MONITORING · CONTAMINANT 2979

2024 · Contaminant 2979 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2979

MONITORING · CONTAMINANT 2979

2024 · Contaminant 2979 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2979

MONITORING · METHYL TERT-BUTYL ETHER (MTBE)

2024 · Methyl tert-butyl ether (MTBE) · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2980

MONITORING · METHYL TERT-BUTYL ETHER (MTBE)

2024 · Methyl tert-butyl ether (MTBE) · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2980

MONITORING · CONTAMINANT 2981

2024 · Contaminant 2981 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2981

MONITORING · CONTAMINANT 2981

2024 · Contaminant 2981 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2981

MONITORING · CONTAMINANT 2982

2024 · Contaminant 2982 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2982

MONITORING · CONTAMINANT 2982

2024 · Contaminant 2982 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2982

MONITORING · CONTAMINANT 2983

2024 · Contaminant 2983 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2983

MONITORING · CONTAMINANT 2983

2024 · Contaminant 2983 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2983

MONITORING · CONTAMINANT 2984

2024 · Contaminant 2984 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2984

MONITORING · CONTAMINANT 2984

2024 · Contaminant 2984 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2984

MONITORING · CONTAMINANT 2985

2024 · Contaminant 2985 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2985

MONITORING · CONTAMINANT 2985

2024 · Contaminant 2985 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2985

MONITORING · CONTAMINANT 2987

2024 · Contaminant 2987 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2987

MONITORING · CONTAMINANT 2987

2024 · Contaminant 2987 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2987

MONITORING · CONTAMINANT 2989

2024 · Contaminant 2989 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2989

MONITORING · CONTAMINANT 2989

2024 · Contaminant 2989 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2989

MONITORING · CONTAMINANT 2990

2024 · Contaminant 2990 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2990

MONITORING · CONTAMINANT 2990

2024 · Contaminant 2990 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2990

MONITORING · CONTAMINANT 2991

2024 · Contaminant 2991 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2991

MONITORING · CONTAMINANT 2991

2024 · Contaminant 2991 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2991

MONITORING · CONTAMINANT 2992

2024 · Contaminant 2992 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2992

MONITORING · CONTAMINANT 2992

2024 · Contaminant 2992 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2992

MONITORING · CONTAMINANT 2996

2024 · Contaminant 2996 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2996

MONITORING · CONTAMINANT 2996

2024 · Contaminant 2996 · Arsenic Rule

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 2996

MONITORING · BERYLLIUM

2024 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · BERYLLIUM

2024 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · BERYLLIUM

2024 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · BERYLLIUM

2024 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · CHLORINE

2022 · Chlorine · Disinfectants and Disinfection Byproducts (Stage 2)

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 0999

MONITORING · CHLORINE

2022 · Chlorine · Disinfectants and Disinfection Byproducts (Stage 2)

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 0999

MONITORING · CHLORINE

2022 · Chlorine · Disinfectants and Disinfection Byproducts (Stage 2)

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 0999

MONITORING · BERYLLIUM

2022 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · BERYLLIUM

2022 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · BERYLLIUM

2022 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · BERYLLIUM

2022 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · BERYLLIUM

2022 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · BERYLLIUM

2022 · Beryllium · Phase I/II/V Inorganic Chemical Rules

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 1040

MONITORING · E. COLI

2020 · E. coli · Drinking water rule (140)

Failure to monitor as scheduled; returned to compliance

CONTAMINANT CODE 3014

Equity context · ACS 2018-2022 · USEPA-clone EJ disparity

Who Drinks This Water

San Tan Valley, Arizona (Census place; block-group disparity scores aggregated by centroid containment): a service population of 101,207. Local disparity score for pm2.5 (fine particulate) sits well below the reference (32). Why we surface this →

POPULATION SHARE
7.7%

Low-income

POPULATION SHARE
38.4%

People of color

POPULATION SHARE
8.4%

Under age 5

POPULATION SHARE
11.7%

Over age 64

NATIONAL PERCENTILE · vs all US block groups (population-weighted; ranked against the national EJScreen indicator distribution)

  • PM2.5 (fine particulate)Health riskFine inhalable particles 2.5 micrometers or smaller. They travel deep into the lungs and into the bloodstream — linked to asthma, heart disease, stroke, and premature death.26below the national median
  • OzoneHealth riskGround-level ozone (smog) inflames the airways. Even short exposures trigger asthma attacks and worsen chronic lung and heart disease.90in the highest 10% nationally
  • Nitrogen dioxide (NO₂)Health riskA tailpipe and combustion gas. Concentrates near busy roads and industrial sites; raises risk of airway inflammation, asthma, and lower respiratory infections in children.51near the national median
  • Diesel particulateHealth riskSoot from diesel engines (trucks, trains, ports, construction). EPA classifies it as a likely human carcinogen and a major driver of childhood asthma near freight corridors.42near the national median
  • Toxic releases (RSEI)Health riskEPA's Risk-Screening Environmental Indicators score — weights TRI chemical releases by toxicity, where they go, and how many people are nearby. Higher means greater modeled cancer and chronic-health risk.27below the national median
  • Traffic proximityHealth riskPopulation-weighted distance to high-volume roads. Living close to heavy traffic raises exposure to PM2.5, NO₂, and diesel exhaust — and the cardiovascular and asthma risks that follow.25below the national median
  • Lead-paint risk (pre-1960 housing)Health riskShare of housing built before 1960, when lead-based paint was common. Dust from deteriorating paint is the leading cause of childhood lead poisoning, which permanently impairs cognitive development.17below the national median
  • Superfund site proximityHealth riskPopulation-weighted distance to NPL Superfund sites — the most contaminated waste sites in the country. Nearby groundwater, soil, and air can carry industrial solvents, metals, and other long-lived contaminants.56near the national median
  • RMP-facility proximityHealth riskDistance to facilities holding chemicals at quantities large enough to require an EPA Risk Management Plan (refineries, fertilizer plants, etc.). These pose acute exposure risk during accidental releases.28below the national median
  • Hazardous-waste site proximityHealth riskDistance to RCRA hazardous-waste handlers (treatment, storage, disposal facilities). Indicates potential exposure to industrial chemicals in air, soil, and groundwater.23below the national median
  • Underground storage tanksHealth riskDensity of underground tanks (gasoline, heating oil, industrial fluids). Leaking tanks are a leading source of benzene and other volatile organic compounds in groundwater drinking-water supplies.40near the national median
  • NPDES wastewater proximityHealth riskDistance to permitted industrial wastewater dischargers. Closer proximity raises exposure to pollutants released into surface waters used for fishing, recreation, and downstream drinking-water intakes.70above the national median
  • Drinking-water non-complianceHealth riskEPA score for public water systems with health-based Safe Drinking Water Act violations. Higher means more residents on systems that recently exceeded safe limits for contaminants like lead, arsenic, or nitrate.76above the national median
EJ disparity scores · service-area block groups (100 = national reference; higher = greater disparate burden)
IndicatorDisparity scoreReading
PM2.5 (fine particulate)32well below the reference
Ozone109near the reference
Nitrogen dioxide (NO₂)57below the reference
Diesel particulate51below the reference
Toxic releases (RSEI)30well below the reference
Traffic proximity31well below the reference
Lead-paint risk (pre-1960 housing)2well below the reference
Superfund site proximity27well below the reference
RMP-facility proximity16well below the reference
Hazardous-waste site proximity20well below the reference
Underground storage tanks20well below the reference
NPDES wastewater proximity71below the reference
Drinking-water non-compliance1well below the reference

Source: Census ACS 2018-2022 (5-year) + USEPA-clone EJ blockgroup stats (raw indicators + EJ disparity mirror).

Source. EPA Safe Drinking Water Information System · retrieved 2026-05-07. Reporting period 2020-01-012026-05-07.

What this is not. SDWIS records compliance against federal MCLs — not a direct readout of tap-water concentrations. Active health-based violations are not the same as a current crisis; we link to the EPA record so you can verify return-to-compliance status before forming a conclusion.