An open MCL violation is not a paperwork note — it is a finding that a contaminant in your drinking water has crossed a maximum contaminant level, and it starts two clocks the day it posts to your EPA SDWIS record: a public-notification clock and a correction deadline. If your system has an open MCL violation, the single highest-value thing you can do is work this 30-day checklist in order, because every missed deadline adds a separate, citable failure on top of the original exceedance. Check your water system's compliance status — free at orevant.com before you read another word, then come back for the step-by-step.

What an 'open MCL violation' actually means

An MCL — maximum contaminant level — is the enforceable limit the EPA sets for a contaminant under the National Primary Drinking Water Regulations (40 CFR Part 141). When a sampling result exceeds the MCL, your system has an MCL violation. 'Open' means it has not yet been resolved and closed on the state's and EPA's books. MCL violations come in two flavors that demand very different responses:

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  • Health-based (acute or chronic) violations — an exceedance of the contaminant itself, like nitrate above 10 mg/L, total coliform/E. coli, arsenic, or a disinfection byproduct above the TTHM/HAA5 limit. See what a nitrate MCL exceedance obligates you to do.
  • Monitoring and reporting violations — a missed sample, a late report, or a failure to follow the required monitoring schedule. These are 'MCL-related' because the state cannot confirm compliance without the data.

The distinction matters because the public-notification requirement and the correction path are different for each.

The clock that starts the day it posts

Under the federal public-notification rule (40 CFR 141.201–141.211), the notice you owe depends on the severity tier:

  • Tier 1 (acute — 24 hours). An E. coli-positive sample, a nitrate exceedance, or another acute risk requires notice within 24 hours of learning of the violation, by the fastest practical means to every customer, plus notice to the state.
  • Tier 2 (30 days). Other MCL and treatment-technique violations carry a 30-day public-notice window, delivered by mail or direct delivery.
  • Tier 3 (12 months or next CCR). Monitoring and reporting violations are typically reported via the annual Consumer Confidence Report or a standalone notice within 12 months.

The 30-day window in Tier 2 is where most small systems lose control — they read the notice, set it aside, and miss the correction deadline. That is what this checklist is for.

The 30-day operator checklist

Days 1–3: confirm and scope the violation. Verify the exceedance against your lab report and the correct MCL, identify which contaminant and which sample location, and confirm the tier so you know your notice clock. Log the date the result posted to SDWIS — that date is what the state enforces against.

Days 1–3: issue the required public notice. If Tier 1, do it now — door hangers, direct mail, broadcast, or posted notice to every person served, plus your state primacy agency. Every day of delay is a separate citable failure. See what a boil-water advisory leaves on your record for the acute case.

Days 3–7: determine the correction. For a treatment or source-water problem, identify the fix and its cost — a new treatment unit, a source change, or a process adjustment. For a monitoring violation, restore the sampling schedule and file the missing results. Your state sets the correction deadline (commonly 30, 60, or 90 days); you need the fix scoped before it lapses.

Days 7–14: run confirmation sampling. The violation does not close until a compliant result is on record. Schedule and complete the follow-up sample that will clear the exceedance, and file it with the state.

Days 14–30: document, close, and calendar. Submit the correction and confirmation results, confirm the state closes the violation, and put the next monitoring date on a calendar you actually own. An MCL violation that recurs after a 'fix' is worse than the first one — it reads as a systemic issue, which under the EPA's new guidance triggers faster enforcement. See EPA's systemic-issues checklist.

What happens if it stays open

An open MCL violation does not age out. It stays on your public SDWIS and ECHO record, follows you into every future sanitary survey, and escalates from a notice to a compliance order to formal enforcement. It is visible to your board, your customers, and any third party who looks — including a free lookup at orevant.com. The cheapest fix is the one that happens in the first 30 days, before the state converts the finding into a binding timeline.

How to see your full record before the inspector does

Orevant reads your EPA SDWIS record and maps your open violations, the patterns inside them, and your next deadlines onto one screen, sourced to the actual regulation. The free lookup shows what is on the public record today; the $199 compliance scan turns that record into a prioritized, regulation-linked action plan; and the $87/month monitoring plan keeps a running calendar so a violation never sneaks up on you again. See how to prepare for a state drinking water inspection.

Check your water system's compliance status — free at orevant.com, and close the gap before the state closes it for you.

FAQ

How long do I have to correct an open MCL violation?

Your state primacy agency sets the correction deadline, commonly 30, 60, or 90 days depending on severity. The public-notification clock is separate: Tier 1 acute violations require notice within 24 hours, and Tier 2 MCL violations within 30 days.

Does a monitoring violation count the same as an exceedance?

Both are violations on your record, but they are corrected differently. A monitoring violation is cleared by restoring the sampling schedule and filing results; an exceedance requires a treatment or source fix plus confirmation sampling.

Will the violation stay on my record after I fix it?

Resolved violations remain visible in historical SDWIS/ECHO records, which is why closing them quickly — before they compound — matters for how your system reads to a reviewer.

Sources: National Primary Drinking Water Regulations (40 CFR Part 141); Public Notification Rule (40 CFR 141.201–141.211); EPA SDWIS/ECHO federal compliance data.