oEPA
United States
Environmental Protection
Agency
Consideration of Other Regulatory
Revisions in Support of the Third Six-Year
Review of the National Primary Drinking
Water Regulations

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Office of Water (4607M)
EPA 810-R-16-003
December 2016

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Table of Contents
1	Introduction and Background	1-1
1.1 Purpose ofthe Review of "Other Regulatory Revisions"	1-1
2	Implementation Issues for Consideration	2-1
2.1	Nitrogen Monitoring in Consecutive Systems and the Distribution System	2-1
2.1.1	Issue Description	2-1
2.1.2	Potential Resolution(s)	2-2
2.2	Alternative Nitrate-Nitrogen MCL of 20 mg/L for Non-Community Water
Systems	2-2
2.2.1	Issue Description	2-2
2.2.2	Potential Resolution(s)	2-3
2.3	Synthetic Organic Chemical (SOC) Method Detection Limits	2-3
2.3.1	Issue Description	2-3
2.3.2	Potential Resolution(s)	2-4
2.4	Fluoride Public Notification Requirements	2-4
2.4.1	Issue Description	2-4
2.4.2	Potential Resolution(s)	2-5
3	References	3-1
Appendix A	A-l
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Acronyms
ASDWA
Association of State Drinking Water Administrators
CFR
Code of Federal Regulations
CWS
Community Water System
EPA
United States Environmental Protection Agency
FR
Federal Register
GWUDI
Ground Water under the Direct Influence of Surface Water
IRIS
Integrated Risk Information System
MCL
Maximum Contaminant Level
MCLG
Maximum Contaminant Level Goal
mg/L
Milligrams per Liter
MRL
Minimum Reporting Level
NCWS
Non-community Water System
NPDWR
National Primary Drinking Water Regulation
NTNCWS
Non-transient, Non-community Water System
OGWDW
Office of Ground Water and Drinking Water
PN
Public Notification
PWS
Public Water System
SDWA
Safe Drinking Water Act
SMCL
Secondary Maximum Contaminant
SOC
Synthetic Organic Chemical
TNCWS
Transient Non-Community Water System
VOC
Volatile Organic Compound
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1 Introduction and Background
Under the Safe Drinking Water Act (SDWA), as amended in 1996, the U.S. Environmental
Protection Agency (EPA) must periodically review existing National Primary Drinking Water
Regulations (NPDWRs) and, if appropriate, revise them. Section 1412(b)(9) of SDWA states:
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.
EPA completed and published the results of its first Six-Year Review (Six-Year Review 1) on July
18, 2003 (68 FR 42908, USEPA, 2003) after developing a systematic approach, or protocol, for the
review of NPDWRs. EPA has applied the same protocol with some refinements to the second Six-
Year Review (Six-Year Review 2) (USEPA, 2009) and third Six-Year Review (Six-Year Review 3)
(USEPA, 2016a) of NPDWRs.
To facilitate the regulatory review of a large number of NPDWRs, EPA performs a series of
analyses at the beginning of each review cycle, intended to target those NPDWRs that are the most
appropriate candidates for revision. During each review cycle, EPA reviews the following key
information and/or factors to determine whether regulatory revisions are possible and appropriate:
health risk assessments; analytical methods and treatment technology assessments; occurrence and
exposure analyses; and other regulatory revisions (such as implementation-related issues).
This document focuses on implementation issues related to Chemical Phase Rules and
Radionuclide Rules reviewed as part of the Six-Year Review 3. The considerations of
implementation issues associated with the Disinfection Byproducts Rules are documented in the
Six-Year Review 3 Technical Support Document for Disinfectants/Disinfection Byproducts
Regulations (USEPA, 2016b).
1.1 Purpose of the Review of "Other Regulatory Revisions"
In addition to the review of the maximum contaminant level goals (MCLGs), maximum
contaminant levels (MCLs), and treatment techniques components of the NPDWRs, EPA considers
whether other regulatory revisions might be needed, such as system monitoring and reporting
requirements, as part of Six-Year Review process. For the Six-Year Review 3, EPA utilized the
Six-Year Review 3 Protocol (USEPA, 2016a) for evaluating which implementation issues to
consider. EPA's protocol first focused on identifying items that were not already being addressed,
or had not been addressed, through alternative mechanisms (e.g., as a part of a recent or ongoing
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rulemaking). In addition to this limitation, EPA also considered potential implementation-related
revisions if they:
1.	Represented a potential change to an NPDWR, as defined under section 1401 of SDWA1;
2.	Were "ready" for rulemaking - that is, the problem to be resolved had been clearly defined
and specific option(s) had been formulated to address the problem under the current
regulatory framework; and
3.	Would clearly improve the level of public health protection; and/or provide a meaningful
opportunity for cost savings (either monetary or burden reduction) while not lessening
public health protection.
1 The subject of the Six-Year-Review, as specified in section 1412(b)(9) of the SDWA, is "each national primary
drinking water regulation," as defined under section 1401 of SDWA.
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2 Implementation Issues for Consideration
As part of Six-Year Review 3, EPA requested its regional offices and headquarters staff involved in
assisting states with implementing NPDWRs to gather input regarding concerns that are within the
scope of the Six-Year Review. Two additional issues were also reconsidered that had been
originally identified during Six-Year Review 2. The potential implementation issues were shared
with the Association of State Drinking Water Administrators (ASDWA) to obtain feedback from
state drinking water agencies concerning the significance of the issues. ASDWA's input is provided
in the document entitled "Six-Year Review 3 Implementation & Other Regulatory Issues for
Potential Consideration - ASDWA Regulatory Committee feedback," available on the Federal
Rulemaking Portal: http://www.regulations.gov. under Docket ID No. EPA-HQ-OW-2016-0627.
The following sections of this document provide background and summary information regarding
four issues that are within the scope of an NPDWR review and appear to be the most important.
Other issues that were shared with ASDWA and considered are listed and briefly described in
Appendix A. Issues that fall within the scope of an NPDWR revision for the current review effort
include:
	Section 2.1- Nitrogen monitoring in the distribution system.
	Section 2.2 - Consider Removal or Further Restricting the Alternative Nitrate-Nitrogen MCL
of 20 mg/L for Non-Community Water Systems (NCWS).
	Section 2.3 - Synthetic Organic Chemical (SOC) Detection Limits.
	Section 2.4 - Fluoride
2.1 Nitrogen Monitoring in Consecutive Systems and the Distribution System
2.1.1 Issue Description
The EPA Six-Year Review 3 workgroup identified the potential increase in nitrite and/or nitrate
levels at the tap as compared to levels at the point of entry to the distribution system as a potential
health concern. Currently, nitrite and nitrate standards are measured at the point of entry to the
distribution system. This issue was also identified as a concern by the States/EPA workgroup
during Six-Year Review 2. Ammonia may be present in drinking water systems as a result of either
naturally-occurring processes or ammonia addition during secondary disinfection to form
chloramines. Nitrite and nitrate are produced during nitrification through ammonia utilization by
nitrifying bacteria.2 This process could result in increased total nitrite/nitrate concentrations at the
point of use above the MCLs for those contaminants. To protect public health, any system with
source water that exceeds the MCLs for nitrate and nitrite must treat the water to a level below the
MCL(s). However, if a water system reduces nitrate and nitrite levels to just meet the MCLs, and
the water system uses chloramine for disinfection, there is a potential for nitrate and nitrite
2 Nitrification is a microbial process by which reduced nitrogen compounds (primarily ammonia) are sequentially
oxidized to nitrite and nitrate. See http://www.epa.gov/sites/production/files/2015-09/documents/nitrification l.pdf for
additional information on nitrification.
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concentrations to exceed the numeric values of their respective MCLs at the point of use if a
nitrification event occurs.
2.1.2 Potential Resolution(s)
To address this concern, certain water systems could develop and implement a nitrification
monitoring program, which would include adding monitoring locations. Additional monitoring
locations to consider could include the point of maximum residence time where disinfection
byproducts samples are already collected, or end use collection points.
A nitrification monitoring program would be most effective for water systems: (1) where nitrite
and/or nitrate levels at the point of entry to the distribution system are approaching the MCLs, and
(2) when trigger levels of ammonia in source water and/or from chloramination are exceeded.
Monitoring of ammonia in source water or through treatment additions may also be necessary for
those systems with nitrite and/or nitrate levels near the MCL.
EPA does not believe revising the monitoring requirements is appropriate at this time because
additional information is needed. For example, research is needed to develop criteria that could be
used to identify the specific systems where distribution system monitoring should be targeted to
prevent nitrate/nitrate MCL exceedances. This would help avoid additional burden on systems
where a potential health concern from nitrite/nitrate would not be likely. After research information
is gathered, EPA can reevaluate the possibility of revising the NPDWRs for nitrate/nitrite to
address nitrification as part of the next Six-Year Review cycle; or if appropriate, EPA can consider
accelerating the review.
2.2 Alternative Nitrate-Nitrogen MCL of 20 mg/L for Non-Community Water Systems
2.2.1 Issue Description
The EPA Six-Year Review 3 workgroup discussed concerns about the appropriate use of an
alternative nitrate-nitrogen MCL allowing up to 20 mg/L for Non-Community Water Systems
(NCWS) under specific conditions. If certain conditions are met, 40 CFR 141.11 provides states
with the discretion to allow NCWSs to use an alternative nitrate-nitrogen MCL above the NPDWR
of 10 mg/L but not exceeding 20 mg/L. The four conditions that must be met are as follows:
1.	Such water will not be available to children under six months of age;
2.	The NCWS is meeting the public notification requirements under 141.209, including
continuous posting of the fact that nitrate levels exceed 10 mg/L and the potential health
effects of exposure;
3.	Local and state public health authorities will be notified annually of nitrate levels that
exceed 10 mg/L; and
4.	No adverse health effects shall result.
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Other provisions related to this issue are included in 40 CFR 141.23 which states:
"Community water systems shall conduct monitoring to determine
compliance with the maximum contaminant levels specified in 
141.62 in accordance with this section. Non-transient, non-
community water systems shall conduct monitoring to determine
compliance with the maximum contaminant levels specified in 
141.62 in accordance with this section. Transient, non-community
water systems shall conduct monitoring to determine compliance
with the nitrate and nitrite maximum contaminant levels in 
141.11 and 141.62 (as appropriate) in accordance with this
section." [emphasis added]
Two concerns were identified with the current rule provisions:
	First, there may be potential health concerns other than methemoglobinemia associated with
the ingestion of nitrate-nitrogen, such as possible effects on fetal development.
	Second, the monitoring provisions in 40 CFR 141.23 imply that Transient Non-Community
Water Systems (TNCWS), a subcategory of NCWSs, are eligible for use of the alternative
MCL, but Non-Transient Non-Community Water Systems (NTNCWS) are not. However,
consistent with 40 CFR 141.11(d) the alternative MCL does apply to entities such as
industrial plants, generally considered to be a NTNCWS, that do not deliver water to
children under six months of age (44 FR 42254, USEPA, 1979).
2.2.2 Potential Resolution(s)
EPA acknowledges that both, nitrate and nitrite, are included in the Integrated Risk Information
System (IRIS) Multi-Year Agenda (USEPA, 2015) and believes that nitrates and nitrites should
remain a priority for reassessment per the outcome results of the Six-Year Review Protocol. It is
important that a reassessment focuses not only on infant methemoglobinemia, but also on other
potential health effects in populations such as the possible effects on fetal development.
Additionally, any effects of nitrate-nitrogen levels, specifically between 10 and 20 mg/L, should be
requested to be evaluated in the IRIS assessment. EPA will reevaluate the possibility of revising the
nitrate NPDWR to clarify the appropriate use of the alternative MCL as part of the next Six-Year
Review cycle; or at any time, if appropriate, EPA can consider accelerating the review.
2.3 Synthetic Organic Chemical (SOC) Method Detection Limits
2.3.1 Issue Description
EPA and states indicated that some laboratories have reported difficulty in consistently achieving
the detection limits for a number of s synthetic organic chemicals (SOCs). Section 40 CFR
141.24(h)18 of the NPDWRs lists detection limits for the SOCs, including certain pesticides. These
detection limits serve as triggers for determining whether the compliance monitoring frequency for
SOCs may be reduced. Public water systems that do not detect a SOC contaminant above the
detection limit may qualify for reduced monitoring frequency of that contaminant. It was reported
that detection limits of several SOCs may be lower than what can economically and efficiently be
achieved by laboratories using approved methods. As a result, water systems may not be able to
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qualify for reduced monitoring if the laboratories cannot achieve the listed detection limits. This
issue was also identified as a concern by the states during Six-Year Review 2.
2.3.2 Potential Resolution(s)
To address the concern about the SOC method detection limits, EPA investigated the minimum
reporting level (MRL) values for SOCs from the Six-Year Review 3 Information Collection
Request (ICR). Using the MRL values, EPA evaluated the percentage of records in the ICR
database that were at or below the detection limit. This percentage gave EPA an indication of
whether and to what extent laboratories are able to detect contaminant concentrations at or below
detection limits. EPA found that for most of the SOCs, nearly half of the concentrations reported
for each of the contaminants were at or below the appropriate detection level stated in the
regulation. Four SOCs (dalapon, dinoseb, picloram and endrin) had more modest results, but each
showed a sufficient number of records below the detection limit, demonstrating that there are
approved analytical methods that can be used to measure below the detection limits. Through this
investigation EPA found there was an existing approved analytical method for each SOC that
laboratories could use to achieve the appropriate detection limits in order to qualify for reduced
monitoring requirements and thus, EPA determined it is not warranted at this time to revise the
regulation to address this issue.
2.4 Fluoride Public Notification Requirements
2.4.1 Issue Description
Currently, community water systems are required to notify their customers within 12 months if a
single sample fluoride concentration exceeds the fluoride Secondary MCL (SMCL) of 2.0 mg/L
(Tier 3 Notice) or within 30 days if their yearly average fluoride concentration exceeds the MCL of
4 mg/L (Tier 2 Notice). The SMCL, although not an NPDWR, is tied to enforceable action (i.e.,
public notification) and could be considered for revision if the MCLG is revised. EPA identified the
following potential concerns with the current public notifications for fluoride.
	Some systems found it confusing to have two different public notification requirements for the
MCL and the SMCL exceedances. (See 40 CFR Subpart Q, 141.208).
	Both of the public notices could be revised to provide consumers with more timely and
practical advice on how to manage fluoride exposure, particularly in teething infants and
children who are vulnerable to severe dental fluorosis during the critical stage of tooth enamel
development for the primary teeth. According to public notice requirements, PWSs could have
up to one year to notify customers of an exceedance of the MCL and SMCL.
	The updated health assessments (NRC, 2006a; USEPA, 2010a) indicate that severe dental
fluorosis is an adverse health effect, not simply a cosmetic effect. According to health
assessments, the adverse health effect can occur at drinking water concentrations >2 mg/L. The
standard public notification language on adverse health effects of fluoride does not reflect the
information in the health assessments (USEPA, 2010a; 2010b). For example, the public
notification for an MCL exceedance identifies severe skeletal fluorosis as the adverse health
effect of concern for concentrations exceeding 4.0 mg/L. The SMCL notification identifies
moderate and severe dental fluorosis as the health effect of concern for concentrations
exceeding 2.0 mg/L.
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EPA will continue to monitor the evolving science, and, when appropriate, will reconsider the
fluoride NPDWR's relative priority for revision and take any other available and appropriate action
to address fluoride risks under the SDWA.
2.4.2 Potential Resolution(s)
EPA will continue to monitor the evolving science and take any other available and appropriate
action to address fluoride risks under SDWA.
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3 References
ASDWA. 2016. Six-Year Review 3 Implementation & Other Regulatory Issues for Potential
Consideration - ASDWA Regulatory Committee feedback. Available on the Federal Rulemaking
Portal: http://www.regulations.gov under Docket ID No. EPA-HQ-OW-2016-0627.
National Research Council. 2006. Fluoride in drinking-water: A Scientific Review of EPA's
Standards. The National Academies Press, Washington D.C.
USEPA. 1979. Interim Primary Drinking Water Regulations; Amendments. Federal Register. Vol.
44, No. 140, p. 42254. July 19, 1979.
USEPA. 2003. National Primary Drinking Water Regulations; Announcement of Completion of
EPA's Review of Existing Drinking Water Standards. Federal Register. Vol. 68, No. 138, p. 42908.
July 18, 2003.
USEPA. 2009. EPA Protocol for the Second Review of Existing National Primary Drinking Water
Regulations (Updated). EPA Report 815-B-09-002. October 2009.
USEPA. 2010a. Fluoride: Dose Response Analysis for Non-Cancer Effects. EPA 820-R-10-019.
December 2010.
USEPA. 2010b. Fluoride: Exposure and Relative Source Contribution Analysis. EPA 820-R-10-
015. December 2010.
USEPA. 2015. IRIS Agenda, https://www.epa.gov/iris/iris-agenda
USEPA. 2016a. EPA Protocol for the Third Review of Existing National Primary Drinking Water
Regulations. EPA Report 810-R-16-007.
USEPA. 2016b. Six-Year Review 3 Technical Support Document for Disinfectants/Disinfection
Byproducts Regulations. EPA Report 810-R-16-012
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Appendix A: Third Six-Year Review of National Primary Drinking Water Regulations: Chemical Phase
Rule and Radionuclides Rule - Summary of Issues Identified for Phase Rules
Table A-1: Third Six-Year Review of National Primary Drinking Water Regulations: Chemical Phase Rule and
Radionuclides Rule - Summary of List of Issues Identified by Work Group to Consider for Possible Revision1
Issue2
Description of Issue and Potential Rule
Modification
Additional Information
Finding
Nitrogen Monitoring in
Consecutive Systems and
in the Distribution System
The nitrate and nitrite compliance monitoring location
should be moved to within the distribution system to
more accurately reflect nitrification considerations in
public water systems that use chloramines.
Nitrification may also occur due to certain source
water characteristics including elevated levels of
ammonia nitrogen.
The issue would likely be of concern primarily in
systems where nitrite or nitrate levels are relatively
close to the MCLs for those contaminants. To address
this concern, the location of the nitrate/nitrite sampling
point could be changed. This change could be
targeted to only affect water systems having source
water characteristics and disinfection management
practices that may result in nitrate/nitrite levels that
could exceed their respective MCLs.
This issue is within the scope of Six-
Year Review. However, research is
needed, as identified in Section 2.1 of
this document, to determine whether a
revision to the rule would be justified,
and if so, ways to target rulemaking to
systems where nitrification may be a
significant issue.
1 This chart provides a summary of issues identified during EPA's review. For those issues where immediate revision has been determined not to be appropriate
at this time, that determination is based on an evaluation of other, higher priority actions as well as potentially limited benefits of the revision.
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Issue2
Description of Issue and Potential Rule
Modification
Additional Information
Finding
Alternative Nitrate MCL of
20 mg/L for Non-
Community Water
Systems (NCWS)
Consider removal or further restricting the alternative
nitrate MCL of 20 mg/L for NCWS. The regulation in
40 CFR 141.11 provides that States have the
discretion to allow NCWSs to use an alternative
nitrate (as nitrogen) MCL of up to 20 mg/L if certain
conditions are met. A 10 mg/L MCL for nitrate exists
for other public water systems. There is concern that
these contaminants may also cause adverse health
effects to populations other than infants under six
months of age. There is a separate concern that the
preamble to the rule appears to indicate the intent
may have been to allow the alternative MCL of 20
mg/L for non-transient NCWSs but not for transient
NCWSs. However, 40 CFR 141.11(d) of the rule
clearly applies to all NCWSs, including non-transient
ones, and 141.23, which addresses monitoring,
should not be interpreted as inconsistent with that
provision, which was intended to allow the alternative
MCL at locations such as industrial plants (which are
non-transient NCWSs) that do not serve water to
infants.
ASDWA is collecting data from all states on how often
the alternative MCL is used and under what
circumstances (ASDWA, 2016).
This issue is within the scope of Six-
Year Review. EPA believes the
appropriate action is to pursue an
updated IRIS health risk assessment
as identified in Section 2.2 of this
document to determine appropriate
actions, if any, concerning the
potential revision of the rule.
SOC Method Detection
Limits
Revise SOC method detection limits based on newer
methodologies (i.e., establish minimum reporting
levels (MRLs)). Some compounds have detection
limits that may be lower than levels that can be
economically and efficiently achieved by laboratories
using approved methods. Therefore, monitoring is
continued quarterly to make sure the concentration
does not exceed the MCL since the lab is not
reporting at a concentration low enough to qualify for
reduced monitoring.
The concept of incorporating newer methodologies
such as MRLs would provide valuable insight into
actual analytical capabilities across laboratories and
States. With respect to achieving the SOC method
detection limits, EPA investigated the MRL values for
SOCs from the Six Year Review 3 Information
Collection Request (ICR) and found that there was an
approved analytical method that laboratories can use
to achieve the appropriate detection limits in order to
reduce monitoring requirements.
This issue is within the scope of Six-
Year Review. Since analytical
methods to achieve the detection limits
listed in the regulation exist, no
change to the rule is appropriate at
this time.
Cyanide Total Screen for
Free Cyanide
Amend the Phase V Rule in CFR Part 141, Subpart
C to allow the use of total cyanide monitoring as a
screen for free cyanide, with follow-up monitoring for
free cyanide only required if the total cyanide
exceeds the MCL for free cyanide.
The concept of using total cyanide as a screening for
free cyanide is discussed in the preamble to the
Phase V Rule, but there is no enabling language in
the body of the rule. There is a footnote in the
detection limit table that identifies one method as a
"screening method for total cyanides," but the
description of the intent is not clear.
This issue is within the scope of Six-
Year Review. It does not merit an
immediate rule change, but may be
addressed when the Phase V Rule or
CFR Part 141, Subpart C is revised for
other more substantive reasons.
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Issue2
Description of Issue and Potential Rule
Modification
Additional Information
Finding
Monitoring for Ground
Water Systems with Low
Nitrate-Nitrite
Reduce the frequency of monitoring for public water
systems with historically low levels of nitrate/nitrite
and the trigger level for increased/decreased
monitoring. Frequencies may be changed to be
consistent with the Standardized Monitoring
Framework or the Alternative Monitoring Guidelines
or through waivers.
This issue was considered in Six-Year Review 2.
ASDWA suggested that there may be less support for
this potential change now than in the past since
nitrate levels in water have been increasing nationally
(ASDWA, 2016).
This issue is within the scope of Six-
Year Review. However, EPA concurs
with ASDWA that this may not be a
substantive issue at this time due to
increasing trends of nitrate levels in
ground water (ASDWA, 2016).
Nitrite (N02) Monitoring
Frequency
Establish a regulatory compliance monitoring repeat
frequency for nitrite monitoring. Consider specifying
that nitrite must be monitored at least once every
compliance cycle (i.e., nine years) when the initial
sample was less than 50 percent of the MCL, or
require future nitrite monitoring when a total nitrate
and nitrate analysis exceeds a certain trigger level.
After an initial nitrite sample is analyzed and found to
be less than 50 percent of the MCL, the current rule
specifies that future monitoring is at a frequency
specified by the state. Some states do not specify a
frequency to address these situations, so there are
many instances where only one initial nitrite sample
has been required. The Agency investigated the
possibility of using total nitrate + nitrite nitrogen
monitoring as a screening tool to predict elevated
nitrite levels, but was unable to derive a valid
statistical correlation using currently available finished
water datasets.
This issue is within the scope of Six-
Year Review. Nitrite (as nitrogen)
levels above the MCL of 1 mg/L are
extremely rare in source waters.
Therefore, any occurrence in finished
waters above the MCL would
essentially be limited to cases where
significant nitrification would occur
after source water entered the water
system. Further evaluation of this
issue can be considered in conjunction
with research needs identified in
Section 2.1 of this document.
Frequency of Nitrate (N03)
Monitoring in transient
non-community water
systems
Establish a regulatory quarterly nitrate compliance
monitoring frequency for transient non-community
water systems (TNCWSs) when the sample result is
less than or equal to 50 percent of the MCL.
Currently, if a TNCWS has a sample result greater
than or equal to 50 percent of the MCL for nitrate,
monitoring is only required annually, even if the
TNCWS has an MCL violation. Requiring TNCWSs to
increase nitrate monitoring to quarterly if the sample
result was greater than or equal to 50 percent of the
MCL would be consistent with other types of public
water systems. Seasonal TNCWSs, such as
campgrounds, require monitoring only at times of year
the system is operational. ASDWA reports that most
states already require increased nitrate monitoring for
TNCWSs when a sample is at or greater than 50% of
the MCL (ASDWA, 2016).
This issue is within the scope of Six-
Year Review. Since most states
already require increased monitoring,
this change does not merit a rule
change unless the Phase II Rule or
CFR Part 141, Subpart C is amended
for other reasons.
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Issue2
Description of Issue and Potential Rule
Modification
Additional Information
Finding
Total Nitrate and Nitrite
Monitoring
Clarify monitoring requirements for total nitrate and
nitrite nitrogen. This would include specifying
monitoring frequency, identification of laboratory
methods, need for confirmation samples, procedures
to make a compliance determination and need for
increased monitoring frequency if detected at or
above 50 percent of the MCL.
Currently, there are separate MCLs for: (1) nitrate (as
nitrogen (N)), (2) nitrite (as N) and (3) total nitrate and
nitrite (as N) that public water system (PWS) must
comply with. Rule language does not specify
monitoring requirements for total nitrate and nitrite.
Even if PWSs are monitoring total nitrate and nitrite
they are not required to include the results or the
health effects language in the consumer confidence
report.
This issue is within the scope of Six-
Year Review. It does not merit an
immediate rule change but should be
considered when the Phase II Rule is
revised for other more substantive
reasons.
IOC Compliance
Determination
Establish compliance determination criteria for
inorganic contaminants (lOCs) using a running
annual average of quarterly samples, consistent with
the process used for volatile organic compounds
(VOCs), and synthetic organic chemicals (SOCs)
and the Arsenic Guidance. 40 CFR 141.23(i)(2)
states that if a sampling point is monitored annually
or less frequently and the result is greater than the
MCL, the site is out of compliance.
When the Arsenic Rule was finalized in 2001, the
preamble described the procedure for determining
compliance as the same for lOCs, VOCs and SOCs,
but the corresponding regulatory section was not
revised to apply to all lOCs.
This issue is within the scope of Six-
Year Review. However, although it
does not merit an immediate rule
change, it should be addressed when
Chemical Phase Rules are revised for
other more substantive reasons.
Significant Figures
Revise MCLs to establish consistent significant
digits. Contaminant MCLs in some rules are not
expressed to the number of significant figures that
are technically feasible.
By example, the nitrite (as N) MCL is specified as 1
mg/L whereas the fluoride MCL is specified as 4.0
mg/L, implying one significant figure for nitrite and two
significant figures for fluoride. Rounding of analysis
results for MCLs with only one significant figure could
lead to an increased risk of adverse health effects for
some contaminants.
This issue is within the scope of Six-
Year Review. It does not merit an
immediate rule change, but should be
addressed when Chemical Phase
Rules are revised for other more
substantive reasons.
Ground Water Under the
Direct Influence of Surface
Water
Define ground water under the direct influence of
surface water (GWUDI) systems in the Chemical
Phase Rules. The term GWUDI was first introduced
in the Surface Water Treatment Rule published June
29, 1989.
There is no use of the term GWUDI in the Chemical
Phase Rules (only ground water or surface water
systems), so there is some confusion as to monitoring
such systems for Phase IIA/ contaminants. ASDWA
reports that states reported treating all GWUDI as
surface waters for the monitoring purposes (ASDWA,
2016).
This issue is within the Scope of Six-
Year Review. Monitoring GWUDI as
surface water would generally be more
protective of consumers due to
increased monitoring frequencies as
compared to ground water. Since
states are reportedly already
implementing the rule in this manner, it
does not merit an immediate rule
change. A clarification could be
addressed when Chemical Phase
Rules are revised for other more
substantive reasons.
Consideration of Other Regulatory Revisions in
Support of the Third Six-Year Review
December 2016

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Issue2
Description of Issue and Potential Rule
Modification
Additional Information
Finding
Monitoring Requirements
for non-community water
systems (NCWS)
Revise the monitoring requirements for non-
community water systems (NCWS) to better target
the potential health risks associated with chronic
contaminants. In light of the health threats, some
monitoring requirements for these systems may be
insufficient, and others may be excessive.
ASDWA has indicated that many states already do
discretionary monitoring of non-community water
systems if they feel there is a site specific problem,
such as petroleum related chemicals leaking at
underground storage tank locations (ASDWA, 2016).
For most contaminants, more guidance may be
valuable since it may be difficult to prescribe specific
monitoring requirements for highly variable site-
specific conditions in a rule revision. However, for
radionuclide contaminants consideration of a rule
modification to include targeted non-transient non-
community water systems, based on occurrence, the
age distribution of typical customer and other factors,
may be appropriate.
This issue is within the scope of Six-
Year Review. It does not merit an
immediate rule change, but should be
addressed when Chemical Phase
Rules are revised for other more
substantive reasons.
(2) Fluoride issue was identified as a concern by the States/EPA workgroup during Six-Year Review 2 and therefore was not shared with ASDWA during Six-Year Review 3.
Consideration of Other Regulatory Revisions in
Support of the Third Six-Year Review
AS
December 2016

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