11.1 The Revised Total Coliform Rule & Assessments
Key Takeaways
- The Total Coliform Rule is a named sub-topic in both the treatment and the distribution Expected Range of Knowledge documents.
- The RTCR replaced the old monthly total coliform MCL with a treatment technique built on Level 1 and Level 2 assessments; only E. coli now carries an MCL.
- A Level 1 trigger is more than 5.0 percent coliform-positive samples for systems taking 40 or more samples per month, or two or more positives for systems taking fewer than 40, or failure to take every required repeat sample.
- A Level 2 trigger is an E. coli MCL violation, a second Level 1 trigger within a rolling 12 months, or for annual-monitoring systems a Level 1 trigger in two consecutive years.
- Every routine total coliform-positive sample requires a set of repeat samples, and every total coliform-positive sample must be analyzed for E. coli.
From an MCL to a Find-and-Fix Rule
The original Total Coliform Rule set a monthly MCL for total coliform. The Revised Total Coliform Rule (RTCR), effective for all systems from April 1, 2016, changed the philosophy. Total coliform is now treated as an indicator that something may be wrong, not as a health violation in itself. The rule works as a treatment technique: a coliform result above a trigger requires the system to find and fix the sanitary defect.
| Old TCR | RTCR | |
|---|---|---|
| Total coliform | MCL violation | Trigger for an assessment - no MCL |
| E. coli | Acute MCL via a fecal coliform pathway | MCL, with a specific definition |
| Response to positives | Public notification | Level 1 or Level 2 assessment plus corrective action |
| Focus | Reporting an exceedance | Identifying and correcting sanitary defects |
California implements the RTCR through the Division of Drinking Water; the federal rule is at 40 CFR Part 141, Subpart Y.
Routine and Repeat Monitoring
Routine samples are collected on a schedule set by system size and population, at sites listed in the system's sample siting plan. The plan must identify routine sites representative of water throughout the distribution system, plus the repeat sites associated with each routine site.
Repeat monitoring is triggered by any total coliform-positive routine sample. The standard set is:
- One repeat at the same tap as the original positive
- One repeat within five service connections upstream
- One repeat within five service connections downstream
Repeat samples are collected within 24 hours of being notified of the positive result, and every total coliform-positive sample - routine or repeat - must be analyzed for E. coli.
[!TIP] Getting the repeat set wrong is itself a violation. "Failure to take every required repeat sample after any single total coliform-positive sample" is an explicit Level 1 trigger, independent of what the results show. Missing the paperwork is treated as seriously as missing the bacteria.
The Triggers
Level 1 Assessment Triggers
- Systems collecting 40 or more samples per month: the system exceeds 5.0 percent total coliform-positive samples for the month.
- Systems collecting fewer than 40 samples per month: the system has two or more total coliform-positive samples in the same month.
- The system fails to take every required repeat sample after any single total coliform-positive sample.
Level 2 Assessment Triggers
- An E. coli MCL violation.
- A second Level 1 trigger within a rolling 12-month period - unless the State determined a likely reason for the first Level 1 trigger and the system corrected the problem.
- For systems on State-approved annual monitoring, a Level 1 trigger in two consecutive years.
What Level 1 and Level 2 Actually Require
Both assessments exist to identify the possible presence of sanitary defects and defects in distribution system coliform monitoring practices.
| Level 1 | Level 2 | |
|---|---|---|
| Who conducts it | The system itself (a trained operator) | A State-approved party - often the State, a third-party expert, or a specifically approved system staff member |
| Depth | Review of treatment, source, protocols, monitoring practices, and recent operations | More comprehensive, including a detailed review of history, treatment, source, distribution, hydraulics, and operational practices |
| Timing | Submitted to the State within 30 days of learning the trigger was met | Same 30-day submission clock |
| Output | Identified sanitary defects, corrective actions taken, and a schedule for those not yet completed | Same, at greater depth |
A sanitary defect is a defect that could provide a pathway for contamination, that is indicative of a failure or imminent failure in a barrier already in place, or that fails to prevent contamination. Classic examples: an unscreened storage vent, a submerged overflow, a failed well seal, a cross-connection, an unprotected sample tap, or a system operated below 20 psi.
The E. coli MCL
An E. coli MCL violation occurs when any of the following happens:
- The system has an E. coli-positive repeat sample following a total coliform-positive routine sample.
- The system has a total coliform-positive repeat sample following an E. coli-positive routine sample.
- The system fails to take all required repeat samples following an E. coli-positive routine sample.
- The system fails to test for E. coli when any repeat sample tests positive for total coliform.
[!IMPORTANT] Note that two of the four pathways are procedural failures, not laboratory results. A system that gets an E. coli-positive routine sample and then does not collect the full repeat set has committed an E. coli MCL violation regardless of what the water actually contained. An E. coli MCL violation is an acute violation requiring Tier 1 public notification within 24 hours and triggers a Level 2 assessment.
Other RTCR Requirements Operators Own
- Sample siting plan. Must be developed, kept current, and available for State review. Sites must be representative; a plan that samples only the two most convenient taps near the office is a documented defect.
- Seasonal systems - those that are not operated year-round, such as campgrounds and seasonal restaurants - must complete a State-approved start-up procedure before serving water to the public, and must certify its completion. Failure to complete the approved start-up procedure is a treatment technique violation.
- Groundwater Rule interaction. A total coliform-positive routine sample at a groundwater system without 4-log virus treatment triggers source water (triggered) monitoring under the Ground Water Rule.
- Corrective action. Sanitary defects identified in an assessment must be corrected, and the system must consult with the State if it cannot correct a defect before submitting the assessment form.
- Reduced monitoring is available to small systems with a clean record, a completed sanitary survey with no significant deficiencies, and an approved sample siting plan.
A Worked Compliance Scenario
A system serving 6,800 people collects 8 routine samples per month. In March, two samples come back total coliform-positive. The system collects the full repeat set for each; all repeats are negative and no E. coli is detected.
- Because the system takes fewer than 40 samples per month and had two positives in the same month, a Level 1 trigger has been met.
- The system conducts a Level 1 assessment itself and submits it to the State within 30 days.
- There is no MCL violation and no acute public notification, because no E. coli was found and no repeat requirement was missed.
- If a second Level 1 trigger occurs before the following March, and the State has not determined and the system has not corrected a cause for the first one, that becomes a Level 2 trigger.
A public water system collects 10 routine samples per month. In June, three samples are total coliform-positive, all repeats are negative, and no E. coli is detected anywhere. What is the compliance consequence?
Which of the following constitutes an E. coli MCL violation under the RTCR?
A seasonal campground water system reopens in May without completing its State-approved start-up procedure. What has occurred?