ROBSTOWN, Tx — Nueces County Water Control and Improvement District 3 received its third arsenic violation on April 22, even though the most recent water sample came in below the federal limit. The violation stems from how the EPA calculates compliance — using a running annual average rather than a single sample.
The most recent arsenic sample, collected April 7, measured 0.0076 milligrams per liter. The federal maximum contaminant level, or MCL, is 0.010 mg/L, meaning that the individual sample is within the legal limit.
However, compliance is determined by a running annual average, or RAA — the average of the last four quarterly samples. That four-quarter average currently sits at 0.011 mg/L, which is above the federal limit.
Here is what the quarterly timeline looks like:
- Q3 2025 — Aug. 8 sample: 0.0108 mg/L — No violation
- Q4 2025 — Dec. 11 sample: 0.0131 mg/L — First violation issued Jan. 23
- Q1 2026 — Jan. 29 sample: 0.0115 mg/L — Second violation issued Feb. 19
- Q2 2026 — April 7 sample: 0.0076 mg/L — Level dropped, but four-quarter average remains 0.011 mg/L — Third violation issued April 22
The RAA system exists to protect people from long-term arsenic exposure, not just one elevated reading. These rules were established by the EPA to protect consumers against the effects of long-term, chronic exposure.
On March 13, TCEQ issued a notice of violation to NCWCID 3 for exceeding the MCL for total trihalomethanes, or THM.
TCEQ also initiated enforcement action against the district. On March 27, the agency sent a Notice of Enforcement to NCWCID 3 covering the fourth quarter 2025 and first quarter 2026 arsenic MCL violations, as well as the first quarter total trihalomethane MCL violation.
TCEQ said the following to KRIS 6 News:
"If serious or continuing violations are identified at any public water system, TCEQ initiates enforcement, and the entity receives a Notice of Enforcement (NOE). When violations are serious enough to warrant an enforcement action, TCEQ is authorized to enforce correction of the violations and to seek penalties to deter future noncompliance. On March 27, 2026, Nueces County WCID 3 was sent a NOE for the fourth quarter 2025 and first quarter 2026 arsenic MCL violations, and the first quarter TTHM MCL, LRAA violation."
Neighborhood News Reporter Stephanie Molina attempted to reach the district by phone but was unsuccessful.
The district has previously said it is working on solutions, including an interconnect with the City of Corpus Christi. In a recent water briefing, Nick Winklemann of CCW said operations on that interconnect are nearly complete.
TCEQ said this is not an emergency. However, drinking water with arsenic above the limit over many years can cause health problems.
Residents with complaints about regulated activities in their area can contact the TCEQ Corpus Christi office at 361-881-6900 or submit a complaint using the online form here.
Residents can check their own water system using the Texas Drinking Water Viewer on the TCEQ website.
