Title 42, The Public Health and WelfareRelease 119-110

§300g–7 Monitoring of Contaminants

Title 42 › CHAPTER 6A — PUBLIC HEALTH SERVICE › SUBCHAPTER XII — SAFETY OF PUBLIC WATER SYSTEMS › Part B — Public Water Systems › § 300g–7

Last updated Sep 22, 2026|Official source

Summary

States that enforce federal drinking water rules may let small public water systems (serving 10,000 people or fewer) skip extra quarterly testing for certain chemical contaminants for a short time, but not for microbes, disinfectants and disinfection byproducts, or corrosion byproducts. To get this short-term relief, the system must do and certify an initial test that finds no contaminant in the ground or surface water, and the State must write that, based on local geology and other facts, the contaminant is unlikely to show up during the interim period. The first test must be done when the system is most likely to be exposed (for pesticides, this means when they are applied and how long they take to reach the water; for other chemicals, the State must consider seasons and travel time). This interim relief ends when permanent relief is approved or at the end of 36 months after August 6, 1996, whichever comes first. For long-term relief, a State with enforcement authority and an approved source water assessment program can put in place alternative, tailored monitoring rules if they follow EPA guidance and can show public health will be protected. Each contaminant is judged separately, and a system must prove the contaminant is not present or is “reliably and consistently below” the maximum contaminant level (meaning the State knows the source and extent well enough to predict the level will not be exceeded; wide swings or results near the limit do not count). If later the contaminant is found at or above the limit, or is no longer reliably low, the system must remove the source or start testing under the national rules. States that did not have enforcement responsibility on August 6, 1996 can ask the EPA Administrator to change monitoring for their systems; any such approval is for 3 years and can be extended in 5-year periods. Any monitoring relief a State gives is treated as part of the national drinking water rules, and States may still use other waiver authorities while EPA reviews and updates those authorities.

Full Legal Text

Title 42, §300g–7

The Public Health and Welfare, Source: USLM XML via OLRC

(a)Interim monitoring relief authority

(1)In general

A State exercising primary enforcement responsibility for public water systems may modify the monitoring requirements for any regulated or unregulated contaminants for which monitoring is required other than microbial contaminants (or indicators thereof), disinfectants and disinfection byproducts or corrosion byproducts for an interim period to provide that any public water system serving 10,000 persons or fewer shall not be required to conduct additional quarterly monitoring during an interim relief period for such contaminants if—

(A)monitoring, conducted at the beginning of the period for the contaminant concerned and certified to the State by the public water system, fails to detect the presence of the contaminant in the ground or surface water supplying the public water system; and

(B)the State, considering the hydrogeology of the area and other relevant factors, determines in writing that the contaminant is unlikely to be detected by further monitoring during such period.

(2)Termination; timing of monitoring

The interim relief period referred to in paragraph (1) shall terminate when permanent monitoring relief is adopted and approved for such State, or at the end of 36 months after August 6, 1996, whichever comes first. In order to serve as a basis for interim relief, the monitoring conducted at the beginning of the period must occur at the time determined by the State to be the time of the public water system’s greatest vulnerability to the contaminant concerned in the relevant ground or surface water, taking into account in the case of pesticides the time of application of the pesticide for the source water area and the travel time for the pesticide to reach such waters and taking into account, in the case of other contaminants, seasonality of precipitation and contaminant travel time.

(b)Permanent monitoring relief authority

(1)In general

Each State exercising primary enforcement responsibility for public water systems under this subchapter and having an approved source water assessment program may adopt, in accordance with guidance published by the Administrator, tailored alternative monitoring requirements for public water systems in such State (as an alternative to the monitoring requirements for chemical contaminants set forth in the applicable national primary drinking water regulations) where the State concludes that (based on data available at the time of adoption concerning susceptibility, use, occurrence, or wellhead protection, or from the State’s drinking water source water assessment program) such alternative monitoring would provide assurance that it complies with the Administrator’s guidelines. The State program must be adequate to assure compliance with, and enforcement of, applicable national primary drinking water regulations. Alternative monitoring shall not apply to regulated microbiological contaminants (or indicators thereof), disinfectants and disinfection byproducts, or corrosion byproducts. The preceding sentence is not intended to limit other authority of the Administrator under other provisions of this subchapter to grant monitoring flexibility.

(2)Guidelines

(A)In general

The Administrator shall issue, after notice and comment and at the same time as guidelines are issued for source water assessment under section 300j–13 of this title, guidelines for States to follow in proposing alternative monitoring requirements under paragraph (1) for chemical contaminants. The Administrator shall publish such guidelines in the Federal Register. The guidelines shall assure that the public health will be protected from drinking water contamination. The guidelines shall require that a State alternative monitoring program apply on a contaminant-by-contaminant basis and that, to be eligible for such alternative monitoring program, a public water system must show the State that the contaminant is not present in the drinking water supply or, if present, it is reliably and consistently below the maximum contaminant level.

(B)Definition

For purposes of subparagraph (A), the phrase “reliably and consistently below the maximum contaminant level” means that, although contaminants have been detected in a water supply, the State has sufficient knowledge of the contamination source and extent of contamination to predict that the maximum contaminant level will not be exceeded. In determining that a contaminant is reliably and consistently below the maximum contaminant level, States shall consider the quality and completeness of data, the length of time covered and the volatility or stability of monitoring results during that time, and the proximity of such results to the maximum contaminant level. Wide variations in the analytical results, or analytical results close to the maximum contaminant level, shall not be considered to be reliably and consistently below the maximum contaminant level.

(3)Effect of detection of contaminants

The guidelines issued by the Administrator under paragraph (2) shall require that if, after the monitoring program is in effect and operating, a contaminant covered by the alternative monitoring program is detected at levels at or above the maximum contaminant level or is no longer reliably or consistently below the maximum contaminant level, the public water system must either—

(A)demonstrate that the contamination source has been removed or that other action has been taken to eliminate the contamination problem; or

(B)test for the detected contaminant pursuant to the applicable national primary drinking water regulation.

(4)States not exercising primary enforcement responsibility

The Governor of any State not exercising primary enforcement responsibility under section 300g–2 of this title on August 6, 1996, may submit to the Administrator a request that the Administrator modify the monitoring requirements established by the Administrator and applicable to public water systems in that State. After consultation with the Governor, the Administrator shall modify the requirements for public water systems in that State if the request of the Governor is in accordance with each of the requirements of this subsection that apply to alternative monitoring requirements established by States that have primary enforcement responsibility. A decision by the Administrator to approve a request under this clause shall be for a period of 3 years and may subsequently be extended for periods of 5 years.

(c)Treatment as NPDWR

All monitoring relief granted by a State to a public water system for a regulated contaminant under subsection (a) or (b) shall be treated as part of the national primary drinking water regulation for that contaminant.

(d)Other monitoring relief

Nothing in this section shall be construed to affect the authority of the States under applicable national primary drinking water regulations to alter monitoring requirements through waivers or other existing authorities. The Administrator shall periodically review and, as appropriate, revise such authorities.

Reference

Citations & Metadata

Citation

42 U.S.C. § 300g–7

Title 42, The Public Health and Welfare

Last Updated

Sep 22, 2026

Release point: 119-110