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Six-Year Review 3 Frequent Questions and Answers

Why did EPA conduct a review of the National Primary Drinking Water Regulations (NPDWRs)?

The 1996 Safe Drinking Water Act (SDWA) Amendments require EPA to conduct a review every six years of existing national primary drinking water regulations and determine which, if any, need to be revised.  This requirement is contained in Section 1412(b)(9) of SDWA, which reads:

The Administrator shall, not less often than every 6 years, review and revise, as appropriate, each national primary drinking water regulation promulgated under this title. Any revision of a national primary drinking water regulation shall be promulgated in accordance with this section, except that each revision shall maintain, or provide for greater, protection of the health of persons.

What NPDWRs are covered by this action?

The Six-Year Review process only applies to existing national primary drinking water regulations (NPDWRs) (i.e., currently regulated contaminants/parameters).  Unregulated contaminants, such as those listed on the Contaminant Candidate List (CCL), are not covered by the Six-Year Review.  The current review specifically focused on a detailed review of 76 regulations promulgated prior to August 2008. The Agency included 12 other NPDWRs (e.g., lead, copper, trichloroethylene (TCE) and tetrachloroethylene (PCE)) in the review. However, these regulations did not need a detailed assessment because they are the subject of recent, ongoing, or pending rulemaking activity.

Why were the Aircraft Drinking Water Rule (ADWR) and Revised Total Coliform Rule (RTCR) excluded from the detailed review? When will the ADWR and RTCR be reviewed as part of the Six-Year Review (SYR) process?

Under the Six-Year Review protocol, EPA identifies NPDWRs with recent or ongoing actions and excludes them from the review process to prevent duplicative Agency efforts. The cutoff date for the NPDWRs reviewed under the SYR3 was August 2008. Based on its review, EPA excluded the ADWR, which was promulgated in 2009, and the RTCR (the revision of the 1989 TCR), which was promulgated in 2013.

EPA intends to include the ADWR and RTCR as part of the fourth cycle of the SYR (i.e., SYR4).

Why was the Public Notification Rule not addressed under Six-Year Review 3?

While the Public Notification (PN) Rule was not explicitly discussed in the Six-Year Review 3 Federal Register Notice, it was considered during the review of the specific NPDWRs reviewed as part of SYR3. In reviewing each NPDWR, the Agency considered public notification aspects of the NPDWRs reviewed as part of SYR3.

How did EPA review the NPDWRs under Six-Year Review 3?

A detailed description of the process the Agency used to review the NPDWRs is documented in the “EPA Protocol for the Third Review of Existing National Primary Drinking Water Regulations.” The foundation of this protocol was developed for the Six-Year Review 1 based on the recommendations of the National Drinking Water Advisory Council. The Six-Year Review 3 process is very similar to the process implemented during the Six-Year Review 1 and the Six-Year Review 2, with some clarifications to the elements related to the review of NPDWRs included in the Microbial and Disinfection Byproducts Rules.

The protocol for the Six-Year Review 3 is broken down into a series of questions that can inform a decision about the appropriateness of revising an NPDWR. These questions are structured into a decision tree related to the following review elements considered for each NPDWR during the Six-Year Review 3: initial review, health effects, analytical feasibility, occurrence and exposure, treatment feasibility, risk balancing and other regulatory revisions.

What are the impacts of the review results from Six-Year Review 3?

This action does not change or add to existing regulatory requirements, and no new requirements will be imposed by this action. Instead, it notifies interested parties of EPA’s review of existing NPDWRs and the Agency’s conclusions about which of these rules warrant new regulatory action at this time.

How were stakeholders involved with Six-Year Review 3?

The Agency has involved interested stakeholders in the Six-Year Review process. Examples of such involvement include the following:

  • In January 2015, states provided input (through the Association of State Drinking Water Administrators) on rule implementation issues related to the NPDWRs being reviewed as part of the third Six-Year Review;
  • In November 2014, the Agency briefed the National Drinking Water Advisory Council (NDWAC) on the Six-Year Review protocol and the key elements of that protocol as they relate to the Microbial and Disinfection Byproducts (MDBP) rules. The briefing included information on how the Agency is implementing the NDWAC’s previous recommendations on the Six-Year Review process to incorporate the review of the MDBP rules;
  • The Agency initiated a series of public stakeholder meetings for the Long Term 2 Enhanced Surface Water Treatment Rule (LT2). These meetings were held in accordance with the recommendation of the Federal Advisory Committee to have public meetings following the first round of monitoring under LT2, and as a result of Executive Order 13563. The Agency hosted three public meetings in Washington, D.C., on December 7, 2011, April 24, 2012, and November 15, 2012. The Agency presented information about LT2 requirements, monitoring data collected under LT2, analytical methods, and forecasts about the second round of monitoring and the treatment technique requirements. In addition to presentations to educate the public, the meetings included public statements, panel discussions, question and answer sessions, and requests by the Agency to provide data and information on the implementation of LT2 for the regulatory review.

Will EPA consider reviewing any NPDWRs before the next review cycle?

If the result of an ongoing health risk assessment or the resolution of data gaps/research needs indicate that significant or compelling new information becomes available that will change the basis for an NPDWR, the Agency may decide to accelerate the review schedule for a particular NPDWR.

What are the next steps?

The Agency requests public comment on the eight NPDWRs identified as candidates for revision, as well as other relevant comments. EPA will consider comments received as the Agency moves forward with determining whether regulatory actions are necessary for the eight NPDWRs. 

Where can I find more information about this notice and the Six-Year Review?

For information on the Six-Year Review, please visit the EPA internet website,

For general information on drinking water, please visit the EPA Office of Ground Water and Drinking Water website at or contact the Safe Drinking Water Hotline at 1-800-426-4791. Local or international calls can reach the Hotline at 703-412-3330. The Safe Drinking Water Hotline is open Monday through Friday, excluding legal holidays, from 10:00 a.m. to 5:30 p.m. Eastern Time.