Revised Total Coliform Rule & Ground Water Rule Fundamentals

Learn the operator fundamentals of the Revised Total Coliform Rule and Ground Water Rule, including coliform monitoring, E. coli, repeat sampling, assessments, sanitary surveys, source monitoring, and corrective action.

Microbiological contamination is one of the most immediate public-health concerns in drinking-water operation. Two important federal regulations address microbial risk from different directions: the Revised Total Coliform Rule, or RTCR, and the Ground Water Rule, or GWR.

The RTCR focuses on monitoring the distribution system for total coliform bacteria and E. coli and on identifying and correcting sanitary defects when monitoring results indicate potential contamination pathways.

The Ground Water Rule focuses specifically on public water systems using groundwater sources and reduces microbial risk through sanitary surveys, source-water monitoring, corrective action, and treatment compliance monitoring.

Why Coliform Bacteria Are Used as Indicators

Testing every drinking-water sample for every possible pathogen is not practical.

Instead, drinking-water programs use indicator organisms to identify conditions that can suggest contamination or loss of sanitary integrity.

Total coliform bacteria are used primarily as indicators of:

sanitary integrity;
distribution-system condition;
sampling problems;
potential contamination pathways.

Total coliform bacteria are not all necessarily harmful themselves. Their presence can indicate conditions that require further investigation.

Total Coliform Versus E. coli

Operators must distinguish total coliform from E. coli.

Total coliform is a broad indicator group.

E. coli is more specifically associated with fecal contamination and therefore represents a more serious public-health concern.

Under the RTCR, routine and repeat samples that are total-coliform positive must also be analyzed for E. coli.

E. coli Maximum Contaminant Level Goal

The federal Maximum Contaminant Level Goal for E. coli is:

zero.

The RTCR E. coli MCL is not simply a numerical concentration such as milligrams per liter. Instead, an E. coli MCL violation is based on specified combinations of routine and repeat sample results.

The Revised Total Coliform Rule

The RTCR replaced the previous Total Coliform Rule approach with greater emphasis on finding and correcting sanitary defects.

The current framework emphasizes:

routine monitoring;
repeat monitoring;
E. coli analysis;
sample siting plans;
Level 1 assessments;
Level 2 assessments;
correction of sanitary defects;
reporting and recordkeeping.

Routine Monitoring

Public water systems subject to the RTCR collect routine distribution-system samples according to their required monitoring frequency.

Depending on system characteristics and applicable state requirements, routine monitoring can occur:

monthly;
quarterly;
annually;
at another frequency established under the applicable rule.

Operators must follow the system's approved sampling requirements rather than assume all systems use the same frequency.

Sample Siting Plan

A public water system must develop and follow a sample siting plan that identifies representative routine and repeat sample locations.

A good sampling plan helps ensure that results represent actual distribution-system conditions.

Operators should know:

routine sample locations;
repeat sample locations;
sample collection schedule;
how to respond to a positive result.

Sampling Technique Matters

An improperly collected microbiological sample can produce misleading results.

Sampling errors can include:

touching the inside of the sample bottle or cap;
sampling from an inappropriate faucet;
failing to remove attachments when required;
inadequate flushing;
improper dechlorination;
improper sample storage or transport.

A positive microbiological result must be treated seriously, but operators should also understand that sanitary sampling technique is part of reliable compliance monitoring.

Total-Coliform Positive Routine Sample

If a routine sample is total-coliform positive, or TC+, the RTCR requires follow-up actions.

Important operator responsibilities include:

ensuring the sample is analyzed for E. coli;
collecting required repeat samples;
following the approved sample siting plan;
notifying appropriate system personnel;
meeting state reporting requirements.

Repeat Samples

The RTCR generally requires at least three repeat samples for each total-coliform-positive routine sample.

The purpose of repeat sampling is to help determine whether the positive result reflects:

a localized condition;
a broader distribution-system problem;
a persistent contamination pathway.

Repeat samples must be collected according to the applicable regulatory timing and siting requirements.

Do Not Wait for the Next Routine Sampling Period

A TC-positive routine sample requires timely follow-up.

An operator should not simply wait until the next normal monthly or quarterly sampling event.

E. coli Analysis

Every routine or repeat sample that tests positive for total coliform must be analyzed for E. coli.

This distinction is critical because E. coli findings can trigger more serious regulatory responses than total coliform alone.

Total Coliform Alone Does Not Automatically Mean an E. coli MCL Violation

One common exam mistake is assuming every total-coliform-positive result is automatically an acute E. coli violation.

That is incorrect.

Total coliform indicates a potential sanitary problem and can trigger repeat sampling or assessments.

E. coli MCL violations depend on the specific combination of routine and repeat results defined by the rule.

Level 1 Assessment

A Level 1 assessment is a basic examination of the water system intended to identify possible sanitary defects.

The assessment can examine:

source water;
treatment;
distribution system;
storage;
sampling practices;
operational practices.

Level 1 assessments are commonly conducted by an appropriate responsible party for the water system, subject to primacy-agency requirements.

Common Level 1 Assessment Triggers

Under the federal RTCR framework, Level 1 assessment triggers include specified frequencies of total-coliform-positive results.

For systems collecting 40 or more samples per month, a Level 1 assessment is triggered when more than 5 percent of the routine and repeat samples are total-coliform positive during the month.

For systems collecting fewer than 40 samples per month, two or more total-coliform-positive routine or repeat samples during the month can trigger a Level 1 assessment.

Failure to collect every required repeat sample after a TC-positive routine sample can also trigger a Level 1 assessment.

Level 2 Assessment

A Level 2 assessment is a more detailed examination of the system.

It is required when monitoring results or repeated problems indicate a greater potential sanitary risk.

Important Level 2 triggers include:

an E. coli MCL violation;
a second Level 1 assessment trigger within a rolling 12-month period;
specified repeated assessment conditions for systems on annual monitoring.

The primacy agency determines who is qualified to conduct a Level 2 assessment.

Sanitary Defects

The purpose of an assessment is not merely to complete paperwork.

The system must identify conditions that can allow contamination to enter or persist in the water system.

Possible sanitary defects include:

damaged storage tank openings;
improperly screened vents;
cross-connections;
low-pressure events;
leaking or damaged piping;
poor sampling practices;
inadequate disinfection;
defective well components;
poor maintenance practices.

Correcting Sanitary Defects

Sanitary defects identified through an RTCR assessment must be corrected within the applicable regulatory timeframe.

The regulatory objective is to remove the contamination pathway or condition rather than simply continue collecting samples indefinitely.

Seasonal Systems

Seasonal public water systems can have special RTCR requirements.

These systems can be required to:

complete state-approved startup procedures;
certify completion of those procedures;
follow the monitoring schedule established for seasonal operation.

The Ground Water Rule

The Ground Water Rule protects public health from microbial pathogens associated with groundwater sources.

The rule applies to public water systems using groundwater.

It also applies when groundwater and surface water are both supplied and the groundwater enters the distribution system without treatment equivalent to the treatment required for surface water.

Why Groundwater Can Be Vulnerable

Groundwater often receives natural protection from soil and geologic formations, but contamination can still occur.

Potential pathways include:

poorly constructed wells;
damaged well seals;
flooding;
surface runoff;
septic-system contamination;
sewer leaks;
improper drainage;
contaminated aquifers.

Four Major Components of the Ground Water Rule

EPA describes four major components of the GWR:

sanitary surveys;
triggered source-water monitoring;
corrective action;
compliance monitoring for systems providing required treatment.

Sanitary Surveys

A sanitary survey is a comprehensive evaluation of the water system intended to identify sanitary risks and significant deficiencies.

Groundwater sanitary surveys evaluate eight major system elements:

source;
treatment;
distribution system;
finished-water storage;
pumps, pump facilities, and controls;
monitoring, reporting, and data verification;
system management and operation;
operator compliance with state requirements.

Significant Deficiency

A significant deficiency is a defect or condition that can create or contribute to microbial contamination or other sanitary risk.

Examples can include:

damaged well construction;
unprotected well openings;
improper drainage around the well;
cross-connections;
inadequate disinfection equipment where treatment is required;
serious storage or distribution defects.

Triggered Source-Water Monitoring

One of the most important Ground Water Rule concepts is triggered source-water monitoring.

For a groundwater system that does not provide qualifying 4-log virus treatment, certain positive distribution-system microbiological results can trigger source-water monitoring.

The purpose is to determine whether the groundwater source itself may be fecally contaminated.

Distribution Positive Versus Source Positive

Operators should distinguish between:

a positive distribution-system coliform sample; and
a fecal-indicator-positive groundwater source sample.

A distribution-system result can trigger source monitoring.

The source-water result helps determine whether the groundwater source itself is contaminated.

Representative Source Monitoring

Systems with multiple groundwater sources can sometimes use representative monitoring when allowed by the state.

The state determines whether representative monitoring is appropriate based on system configuration and source use.

Operators should follow the approved monitoring arrangement rather than assume that one source sample automatically represents every well.

Corrective Action Under the Ground Water Rule

Corrective action is required when specified groundwater-system problems are identified.

Important triggers include:

a significant deficiency identified by the state;
confirmed source-water fecal contamination;
other conditions for which the state requires corrective action under the rule.

Corrective Action Options

EPA identifies several corrective-action approaches.

Depending on the condition and state direction, corrective action can include:

correcting the significant deficiency;
eliminating the source of contamination;
providing an alternate source of water;
providing treatment that reliably achieves at least 4-log treatment of viruses.

What Does 4-Log Mean?

A 4-log reduction corresponds to:

99.99 percent reduction.

This means the treatment process reduces the number of target organisms by a factor of 10,000.

Example of 4-Log Reduction

Suppose untreated water contains 100,000 target organisms in a hypothetical test volume.

A 4-log reduction gives:

100,000 ÷ 10,000 = 10

The remaining concentration is 0.01 percent of the original amount, representing 99.99 percent reduction.

Corrective-Action Timeline

When the state notifies a groundwater system of a significant deficiency and does not itself specify the corrective action, the federal GWR framework generally requires consultation with the state within 30 days.

The system generally must then:

complete the required corrective action; or
be in compliance with a state-approved corrective-action plan and schedule

within 120 days of the applicable notification.

Operators must follow state instructions because the primacy agency can specify the required corrective action and schedule.

Compliance Monitoring for 4-Log Treatment

A groundwater system that uses treatment to meet the GWR microbial-protection requirements must monitor treatment performance as required by the rule.

The purpose is to verify that treatment reliably achieves the required virus inactivation or removal.

Depending on the approved treatment process, important parameters can include:

disinfectant concentration;
flow;
contact conditions;
equipment operation;
other state-approved critical limits.

Treatment Must Be Reliable

Installing disinfection equipment is not enough.

The operator must maintain the process so the required treatment is reliably achieved.

This can require:

continuous or required-frequency monitoring;
calibration;
alarm response;
chemical supply management;
backup equipment;
recordkeeping.

RTCR and GWR Work Together

The two rules address different parts of microbial protection.

The RTCR focuses heavily on distribution-system microbiological monitoring and sanitary defects.

The GWR focuses on groundwater-source vulnerability and source-specific corrective action.

A groundwater system can therefore have responsibilities under both rules.

Example: TC-Positive Distribution Sample

A groundwater system receives a total-coliform-positive routine distribution sample.

The operator should not assume the problem is automatically located at the well.

The system must follow RTCR repeat-sampling and E. coli requirements.

Depending on the GWR treatment status and regulatory conditions, the result can also trigger groundwater source monitoring.

Example: E. coli Detected

E. coli findings require prompt attention because they can indicate fecal contamination.

The system must follow the applicable E. coli MCL, reporting, public-notification, assessment, and groundwater source-monitoring requirements.

The exact required response depends on the sample-result combination and the system's regulatory status.

Example: Defective Well Seal

A sanitary survey identifies a damaged well seal that can allow contaminated surface water to enter the well.

This can be considered a significant deficiency requiring corrective action.

Simply increasing routine distribution sampling does not correct the physical defect.

Example: 4-Log Treatment System

A groundwater system provides approved treatment designed to achieve 4-log virus inactivation.

The operator must maintain and monitor the treatment process according to applicable GWR and state requirements.

A failure to maintain the required treatment performance can become a treatment-technique compliance problem.

Common RTCR Mistakes

Assuming total coliform and E. coli mean the same thing.
Assuming any TC-positive result automatically creates an E. coli MCL violation.
Failing to collect required repeat samples.
Failing to analyze TC-positive samples for E. coli.
Ignoring the sample siting plan.
Treating a Level 1 or Level 2 assessment as paperwork instead of searching for sanitary defects.
Failing to correct an identified sanitary defect.

Common Ground Water Rule Mistakes

Assuming groundwater is automatically free of microbial risk.
Confusing distribution monitoring with source-water monitoring.
Ignoring significant deficiencies identified during sanitary surveys.
Assuming triggered source monitoring applies identically to every groundwater system.
Failing to recognize the significance of 4-log virus treatment.
Failing to monitor critical treatment parameters.
Assuming continued sampling is a substitute for correcting a contamination pathway.

A Practical Response to a Microbiological Result

Verify the sample identity and location.
Review the laboratory result.
Determine whether the result is TC-positive, E. coli-positive, or both.
Notify responsible system personnel.
Follow the RTCR repeat-sampling requirements.
Determine whether groundwater source monitoring is triggered.
Review recent operating conditions and distribution-system events.
Investigate possible sanitary defects.
Complete required assessments and corrective actions.
Complete required reporting and public notification.

What to Remember for the Exam

Total coliform is primarily an indicator of sanitary integrity and potential contamination pathways.
E. coli is more specifically associated with fecal contamination.
The E. coli MCLG is zero.
Every routine or repeat sample that is total-coliform positive must be analyzed for E. coli.
The RTCR generally requires at least three repeat samples after a TC-positive routine sample.
A sample siting plan identifies routine and repeat microbiological sampling locations.
For systems collecting 40 or more samples per month, more than 5 percent TC-positive samples can trigger a Level 1 assessment.
For systems collecting fewer than 40 samples per month, two or more TC-positive samples in a month can trigger a Level 1 assessment.
Failure to collect all required repeat samples can trigger a Level 1 assessment.
An E. coli MCL violation is an important Level 2 assessment trigger.
RTCR assessments are intended to identify and correct sanitary defects.
The Ground Water Rule applies to public water systems using groundwater sources.
The four major GWR components are sanitary surveys, triggered source monitoring, corrective action, and compliance monitoring.
Groundwater sanitary surveys evaluate eight major system elements.
A positive distribution sample and a positive groundwater source sample are not the same thing.
Significant deficiencies and confirmed source fecal contamination can require corrective action.
Corrective action can include fixing the deficiency, removing the contamination source, using an alternate source, or providing 4-log virus treatment.
4-log treatment corresponds to 99.99 percent reduction.
When applicable, federal GWR corrective-action provisions generally involve state consultation within 30 days and completion or an approved corrective-action schedule within 120 days.
Groundwater systems can have simultaneous responsibilities under both the RTCR and the Ground Water Rule.