388 Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Parts 9, 141, and 142 

[EPA–HQ–OW–2002–0043; FRL–8012–1] 

RIN 2040–AD38 

National Primary Drinking Water 

Regulations: Stage 2 Disinfectants and 

Disinfection Byproducts Rule 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is promulgating today’s 

final rule, the Stage 2 Disinfectants and 

Disinfection Byproducts Rule (DBPR), to 

provide for increased protection against 

the potential risks for cancer and 

reproductive and developmental health 

effects associated with disinfection 

byproducts (DBPs). The final Stage 2 

DBPR contains maximum contaminant 

level goals for chloroform, 

monochloroacetic acid and 

trichloroacetic acid; National Primary 

Drinking Water Regulations, which 

consist of maximum contaminant levels 

(MCLs) and monitoring, reporting, and 

public notification requirements for 

total trihalomethanes (TTHM) and 

haloacetic acids (HAA5); and revisions 

to the reduced monitoring requirements 

for bromate. This document also 

specifies the best available technologies 

for the final MCLs. EPA is also 

approving additional analytical methods 

for the determination of disinfectants 

and DBPs in drinking water. EPA 

believes the Stage 2 DBPR will reduce 

the potential risks of cancer and 

reproductive and developmental health 

effects associated with DBPs by 

reducing peak and average levels of 

DBPs in drinking water supplies. 

The Stage 2 DBPR applies to public 

water systems (PWSs) that are 

community water systems (CWSs) or 

nontransient noncommunity water 

systems (NTNCWs) that add a primary 

or residual disinfectant other than 

ultraviolet light or deliver water that has 

been treated with a primary or residual 

disinfectant other than ultraviolet light. 

This rule also makes minor 

corrections to drinking water 

regulations, specifically the Public 

Notification tables. New endnotes were 

added to these tables in recent 

rulemakings; however, the 

corresponding footnote numbering in 

the tables was not changed. In addition, 

this rule makes a minor correction to the 

Stage 1 Disinfectants and Disinfection 

Byproducts Rule by replacing a sentence 

that was inadvertently removed. 

DATES: This final rule is effective on 

March 6, 2006. For judicial review 

purposes, this final rule is promulgated 

as January 4, 2006. The incorporation by 

reference of certain publications listed 

in the rule is approved by the Director 

of the Federal Register as of March 6, 

2006. 

ADDRESSES: EPA has established a 

docket for this action under Docket ID 

No. EPA–HQ–OW–2002–0043. All 

documents in the docket are listed on 

the http://www.regulations.gov Web 

site. 

Although listed in the index, some 

information is not publicly available, 

e.g., CBI or other information whose 

disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, is not placed on 

the Internet and will be publicly 

available only in hard copy form. 

Publicly available docket materials 

are available either electronically 

through http://www.regulations.gov or 

in hard copy at the Water Docket, EPA/ 

DC, EPA West, Room B102, 1301 

Constitution Ave., NW., Washington, 

DC. The Public Reading Room is open 

from 10 a.m. to 4 p.m., Monday through 

Friday, excluding legal holidays. The 

telephone number for the Public 

Reading Room is (202) 566–1744, and 

the telephone number for the Water 

Docket is (202) 566–2426. 

FOR FURTHER INFORMATION CONTACT: For 

technical inquiries, contact Tom 

Grubbs, Standards and Risk 

Management Division, Office of Ground 

Water and Drinking Water (MC 4607M), 

Environmental Protection Agency, 1200 

Pennsylvania Ave., NW., Washington, 

DC 20460; telephone number: (202) 

564–5262; fax number: (202) 564–3767; 

e-mail address: grubbs.thomas@epa.gov. 

For general information, contact the 

Safe Drinking Water Hotline, Telephone 

(800) 426–4791. The Safe Drinking 

Water Hotline is open Monday through 

Friday, excluding legal holidays, from 

10 a.m. to 4 p.m. Eastern Time. 

SUPPLEMENTARY INFORMATION: 

I. General Information 

A. Does This Action Apply to Me? 

Entities potentially regulated by the 

Stage 2 DBPR are community and 

nontransient noncommunity water 

systems that add a primary or residual 

disinfectant other than ultraviolet light 

or deliver water that has been treated 

with a primary or residual disinfectant 

other than ultraviolet light. Regulated 

categories and entities are identified in 

the following chart. 

Category Examples of regulated entities 

Industry ............................................................... Community and nontransient noncommunity water systems that use a primary or residual disinfectant other than ultraviolet light or deliver water that has been treated with a primary or 

residual disinfectant other than ultraviolet light. 

State, Local, Tribal, or Federal Governments .... Community and nontransient noncommunity water systems that use a primary or residual disinfectant other than ultraviolet light or deliver water that has been treated with a primary or 

residual disinfectant other than ultraviolet light. 

This table is not intended to be 

exhaustive, but rather provides a guide 

for readers regarding entities likely to be 

regulated by this action. This table lists 

the types of entities that EPA is now 

aware could potentially be regulated by 

this action. Other types of entities not 

listed in the table could also be 

regulated. To determine whether your 

facility is regulated by this action, you 

should carefully examine the definition 

of ‘‘public water system’’ in § 141.2 and 

the section entitled ‘‘coverage’’ (§ 141.3) 

in Title 40 of the Code of Federal 

Regulations and applicability criteria in 

§ 141.600 and 141.620 of today’s 

proposal. If you have questions 

regarding the applicability of this action 

to a particular entity, contact the person 

listed in the preceding FOR FURTHER

INFORMATION CONTACT section. 

B. How Can I Get Copies of This 

Document and Other Related 

Information? 

See the ADDRESSES section for 

information on how to receive a copy of 

this document and related information. 

Regional contacts: 

I. Kevin Reilly, Water Supply Section, 

JFK Federal Bldg., Room 203, 

Boston, MA 02203, (617) 565–3616. 

II. Michael Lowy, Water Supply Section, 

290 Broadway, 24th Floor, New 


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York, NY 10007–1866, (212) 637–

3830. 

III. Jason Gambatese, Drinking Water 

Section (3WM41), 1650 Arch Street, 

Philadelphia, PA 19103–2029, (215) 

814–5759. 

IV. Robert Burns, Drinking Water 

Section, 61 Forsyth Street SW., 

Atlanta, GA 30303, (404) 562–9456. 

V. Miguel Del Toral, Water Supply 

Section, 77 W. Jackson Blvd., 

Chicago, IL 60604, (312) 886–5253. 

VI. Blake L. Atkins, Drinking Water 

Section, 1445 Ross Avenue, Dallas, 

TX 75202, (214) 665–2297. 

VII. Douglas J. Brune, Drinking Water 

Management Branch, 901 North 5th 

Street, Kansas City, KS 66101, (800) 

233–0425. 

VIII. Bob Clement, Public Water Supply 

Section (8P2-W-MS), 999 18th 

Street, Suite 500, Denver, CO 

80202–2466, (303) 312–6653. 

IX. Bruce Macler, Water Supply Section, 

75 Hawthorne Street, San 

Francisco, CA 94105, (415) 972–

3569. 

X. Wendy Marshall, Drinking Water 

Unit, 1200 Sixth Avenue (OW–136), 

Seattle, WA 98101, (206) 553–1890. 

Abbreviations Used in This Document 

ASDWA Association of State Drinking 

Water Administrators 

ASTM American Society for Testing 

and Materials 

AWWA American Water Works 

Association 

AwwaRF American Water Works 

Association Research Foundation 

BAT Best available technology 

BCAA Bromochloroacetic acid 

BDCM Bromodichloromethane 

CDBG Community Development Block 

Grant 

CWS Community water system 

DBAA Dibromoacetic acid 

DBCM Dibromochloromethane 

DBP Disinfection byproduct 

DBPR Disinfectants and Disinfection 

Byproducts Rule 

DCAA Dichloroacetic acid 

EA Economic analysis 

EC Enhanced coagulation 

EDA Ethylenediamine 

EPA United States Environmental 

Protection Agency 

ESWTR Enhanced Surface Water 

Treatment Rule 

FACA Federal Advisory Committee 

Act 

GAC Granular activated carbon 

GC/ECD Gas chromatography using 

electron capture detection 

GWR Ground Water Rule 

GWUDI Ground water under the direct 

influence of surface water 

HAA5 Haloacetic acids (five) (sum of 

monochloroacetic acid, dichloroacetic 

acid, trichloroacetic acid, 

monobromoacetic acid, and 

dibromoacetic acid) 

HAN Haloacetonitriles 

(trichloroacetonitrile, 

dichloroacetonitrile, 

bromochloroacetonitrile, and 

dibromoacetonitrile) 

IC Ion chromatograph 

IC/ICP–MS Ion chromatograph 

coupled to an inductively coupled 

plasma mass spectrometer 

IDSE Initial distribution system 

evaluation 

ILSI International Life Sciences 

Institute 

IESWTR Interim Enhanced Surface 

Water Treatment Rule 

IPCS International Programme on 

Chemical Safety 

IRIS Integrated Risk Information 

System (EPA) 

LOAEL Lowest observed adverse effect 

level 

LRAA Locational running annual 

average 

LT1ESTWR Long Term 1 Enhanced 

Surface Water Treatment Rule 

LT2ESTWR Long Term 2 Enhanced 

Surface Water Treatment Rule 

MBAA Monobromoacetic acid 

MCAA Monochloroacetic acid 

MCL Maximum contaminant level 

MCLG Maximum contaminant level 

goal 

M–DBP Microbial and disinfection 

byproducts mg/L Milligram per liter 

MRL Minimum reporting level 

MRDL Maximum residual disinfectant 

level 

MRDLG Maximum residual 

disinfectant level goal 

NDMA N-nitrosodimethylamine 

NDWAC National Drinking Water 

Advisory Council 

NF Nanofiltration 

NOAEL No Observed Adverse Effect 

Level 

NODA Notice of data availability 

NPDWR National primary drinking 

water regulation 

NRWA National Rural Water 

Association 

NTNCWS Nontransient 

noncommunity water system 

NTP National Toxicology Program 

NTTAA National Technology Transfer 

and Advancement Act 

OMB Office of Management and 

Budget 

PAR Population attributable risk 

PE Performance evaluation 

PWS Public water system 

RAA Running annual average 

RFA Regulatory Flexibility Act 

RfD Reference dose 

RSC Relative source contribution 

RUS Rural Utility Service 

SAB Science Advisory Board 

SBAR Small Business Advisory 

Review 

SBREFA Small Business Regulatory 

Enforcement Fairness Act 

SDWA Safe Drinking Water Act, or the 

‘‘Act,’’ as amended in 1996 

SER Small Entity Representative 

SGA Small for gestational age 

SUVA Specific ultraviolet absorbance 

SWAT Surface Water Analytical Tool 

SWTR Surface Water Treatment Rule 

TC Total coliforms 

TCAA Trichloroacetic acid 

TCR Total Coliform Rule 

THM Trihalomethane 

TOC Total organic carbon 

TTHM Total trihalomethanes (sum of 

four THMs: chloroform, 

bromodichloromethane, 

dibromochloromethane, and 

bromoform) 

TWG Technical work group 

UMRA Unfunded Mandates Reform 

Act 

UV 254 Ultraviolet absorption at 254 

nm 

VSL Value of Statistical Life 

WTP Willingness To Pay 

Table of Contents 

I. General Information 

A. Does This Action Apply to Me? 

B. How Can I Get Copies of This Document 

and Other Related Information? 

II. Summary of the Final Rule 

A. Why is EPA Promulgating the Stage 2 

DBPR? 

B. What Does the Stage 2 DBPR Require? 

1. Initial Distribution System Evaluation 

2. Compliance and monitoring 

requirements 

3. Operational Evaluation Levels 

4. Consecutive systems 

C. Correction of § 141.132 

III. Background 

A. Statutory Requirements and Legal 

Authority 

B. What is the Regulatory History of the 

Stage 2 DBPR and How Were 

Stakeholders Involved? 

1. Total Trihalomethanes Rule 

2. Stage 1 Disinfectants and Disinfection 

Byproducts Rule 

3. Stakeholder involvement 

a. Federal Advisory Committee process 

b. Other outreach processes 

C. Public Health Concerns to be Addressed 

1. What are DBPs? 

2. DBP Health Effects 

a. Cancer health effects 

i. Epidemiology 

ii. Toxicology 

b. Reproductive and developmental health 

effects 

i. Epidemiology 

ii. Toxicology 

c. Conclusions 

D. DBP Occurrence and DBP Control 

1. Occurrence 

2. Treatment 

E. Conclusions for Regulatory Action 

IV. Explanation of Today’s Action 

A. MCLGs 


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390 Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 

1. Chloroform MCLG 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

2. HAA MCLGs: TCAA and MCAA 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

B. Consecutive Systems 

1. Today’s Rule 

2. Background and analysis 

3. Summary of major comments 

C. LRAA MCLs for TTHM and HAA5 

1. Today’s rule 

2. Background and analysis 

3. Summary of major comments 

D. BAT for TTHM and HAA5 

1. Today’s rule 

2. Background and analysis 

3. Summary of major comments 

E. Compliance Schedules 

1. Today’s rule 

2. Background and analysis 

3. Summary of major comments 

F. Initial Distribution System Evaluation 

(IDSE) 

1. Today’s rule 

a. Applicability 

b. Data collection 

i. Standard monitoring 

ii. System specific study 

iii. 40/30 certification 

c. Implementation 

2. Background and analysis 

a. Standard monitoring 

b. Very small system waivers 

c. 40/30 certifications 

d. System specific studies 

e. Distribution System Schematics 

3. Summary of major comments 

G. Monitoring Requirements and 

Compliance Determination for TTHM 

and HAA5 MCLs 

1. Today’s Rule 

a. IDSE Monitoring 

b. Routine Stage 2 Compliance Monitoring 

i. Reduced monitoring 

ii. Compliance determination 

2. Background and Analysis 

3. Summary of Major Comments 

H. Operational Evaluation Requirements 

initiated by TTHM and HAA5 Levels 

1. Today’s rule 

2. Background and analysis 

3. Summary of major comments 

I. MCL, BAT, and Monitoring for Bromate 

1. Today’s rule 

2. Background and analysis 

a. Bromate MCL 

b. Criterion for reduced bromate 

monitoring 

3. Summary of major comments 

J. Public Notice Requirements 

1. Today’s rule 

2. Background and analysis 

3. Summary of major comments 

K. Variances and Exemptions 

1. Today’s Rule 

2. Background and Analysis 

a. Variances 

b. Affordable Treatment Technologies for 

Small Systems 

c. Exemptions 

3. Summary of major comments 

L. Requirements for Systems to Use 

Qualified Operators 

M. System Reporting and Recordkeeping 

Requirements 

1. Today’s rule 

2. Summary of major comments 

N. Approval of Additional Analytical 

Methods 

1. Today’s Rule 

2. Background and Analysis 

O. Laboratory Certification and Approval 

1. PE acceptance criteria 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

2. Minimum reporting limits 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

P. Other regulatory changes 

V. State Implementation 

A. Today’s rule 

1. State Primacy Requirements for 

Implementation Flexibility 

2. State recordkeeping requirements 

3. State reporting requirements 

4. Interim primacy 

5. IDSE implementation 

B. Background and Analysis 

C. Summary of Major Comments 

VI. Economic Analysis 

A. Regulatory Alternatives Considered 

B. Analyses that Support Today’s Final 

Rule 

1. Predicting water quality and treatment 

changes 

2. Estimating benefits 

3. Estimating costs 

4. Comparing regulatory alternatives 

C. Benefits of the Stage 2 DBPR 

1. Nonquantified benefits 

2. Quantified benefits 

3. Timing of benefits accrual 

D. Costs of the Stage 2 DBPR 

1. Total annualized present value costs 

2. PWS costs 

a. IDSE costs 

b. PWS treatment costs 

c. Monitoring costs 

3. State/Primacy agency costs 

4. Non-quantified costs 

E. Household Costs of the Stage 2 DBPR 

F. Incremental Costs and Benefits of the 

Stage 2 DBPR 

G. Benefits From the Reduction of Cooccurring Contaminants 

H. Potential Risks From Other 

Contaminants 

1. Emerging DBPs 

2. N-nitrosamines 

3. Other DBPs 

I. Effects of the Contaminant on the 

General Population and Groups within 

the General Population that are 

Identified as Likely To Be at Greater Risk 

of Adverse Health Effects 

J. Uncertainties in the Risk, Benefit, and 

Cost Estimates for the Stage 2 DBPR 

K. Benefit/Cost Determination for the Stage 

2 DBPR 

L. Summary of Major Comments 

1. Interpretation of health effects studies 

2. Derivation of benefits 

3. Use of SWAT 

5. Unanticipated risk issues 

6. Valuation of cancer cases avoided 

VII. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review 

B. Paperwork Reduction Act 

C. Regulatory Flexibility Act 

D. Unfunded Mandates Reform Act 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

G. Executive Order 13045: Protection of 

Children from Environmental Health 

Risks and Safety Risks 

H. Executive Order 13211: Actions 

Concerning Regulations That 

Significantly Affect Energy Supply, 

Distribution, or Use 

I. National Technology Transfer and 

Advancement Act 

J. Executive Order 12898: Federal Actions 

to Address Environmental Justice in 

Minority Populations or Low-Income 

Populations 

K. Consultations with the Science 

Advisory Board, National Drinking 

Water Advisory Council, and the 

Secretary of Health and Human Services 

L. Plain Language 

M. Analysis of the Likely Effect of 

Compliance With the Stage 2 DBPR on 

the Technical, Managerial, and Financial 

Capacity of Public Water Systems 

N. Congressional Review Act 

VIII. References 

II. Summary of the Final Rule 

A. Why is EPA Promulgating the Stage 

2 DBPR? 

The Environmental Protection Agency 

is finalizing the Stage 2 Disinfectants 

and Disinfection Byproduct Rule 

(DBPR) to reduce potential cancer risks 

and address concerns with potential 

reproductive and developmental risks 

from DBPs. The Agency is committed to 

ensuring that all public water systems 

provide clean and safe drinking water. 

Disinfectants are an essential element of 

drinking water treatment because of the 

barrier they provide against harmful 

waterborne microbial pathogens. 

However, disinfectants react with 

naturally occurring organic and 

inorganic matter in source water and 

distribution systems to form 

disinfection byproducts (DBPs) that may 

pose health risks. The Stage 2 DBPR is 

designed to reduce the level of exposure 

from DBPs without undermining the 

control of microbial pathogens. The 

Long Term 2 Enhanced Surface Water 

Treatment Rule (LT2ESWTR) is being 

finalized and implemented 

simultaneously with the Stage 2 DBPR 

to ensure that drinking water is 

microbiologically safe at the limits set 

for DBPs. 

Congress required EPA to promulgate 

the Stage 2 DBPR as part of the 1996 

Safe Drinking Water Act (SDWA) 

Amendments (section 1412(b)(2)(C)). 

The Stage 2 DBPR augments the Stage 

1 DBPR that was finalized in 1998 (63 

FR 69390, December 16, 1998) (USEPA 


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1998a). The goal of the Stage 2 DBPR is 

to target the highest risk systems for 

changes beyond those required for Stage 

1 DBPR. Today’s rule reflects consensus 

recommendations from the Stage 2 

Microbial/Disinfection Byproducts (M–

DBP) Federal Advisory Committee (the 

Advisory Committee) as well as public 

comments. 

New information on health effects, 

occurrence, and treatment has become 

available since the Stage 1 DBPR that 

supports the need for the Stage 2 DBPR. 

EPA has completed a more extensive 

analysis of health effects, particularly 

reproductive and developmental 

endpoints, associated with DBPs since 

the Stage 1 DBPR. Some recent studies 

on both human epidemiology and 

animal toxicology have shown possible 

associations between chlorinated 

drinking water and reproductive and 

developmental endpoints such as 

spontaneous abortion, stillbirth, neural 

tube and other birth defects, intrauterine 

growth retardation, and low birth 

weight. While results of these studies 

have been mixed, EPA believes they 

support a potential hazard concern. 

New epidemiology and toxicology 

studies evaluating bladder, colon, and 

rectal cancers have increased the weight 

of evidence linking these health effects 

to DBP exposure. The large number of 

people (more than 260 million 

Americans) exposed to DBPs and the 

potential cancer, reproductive, and 

developmental risks have played a 

significant role in EPA’s decision to 

move forward with regulatory changes 

that target lowering DBP exposures 

beyond the requirements of the Stage 1 

DBPR. 

While the Stage 1 DBPR is predicted 

to provide a major reduction in DBP 

exposure, national survey data suggest 

that some customers may receive 

drinking water with elevated, or peak, 

DBP concentrations even when their 

distribution system is in compliance 

with the Stage 1 DBPR. Some of these 

peak concentrations are substantially 

greater than the Stage 1 DBPR maximum 

contaminant levels (MCLs) and some 

customers receive these elevated levels 

of DBPs on a consistent basis. The new 

survey results also show that Stage 1 

DBPR monitoring sites may not be 

representative of higher DBP 

concentrations that occur in distribution 

systems. In addition, new studies 

indicate that cost-effective technologies 

including ultraviolet light (UV) and 

granular activated carbon (GAC) may be 

very effective at lowering DBP levels. 

EPA’s analysis of this new occurrence 

and treatment information indicates that 

significant public health benefits may be 

achieved through further, cost-effective 

reductions of DBPs in distribution 

systems. 

The Stage 2 DBPR presents a risktargeting approach to reduce risks from 

DBPs. The new requirements provide 

for more consistent, equitable protection 

from DBPs across the entire distribution 

system and the reduction of DBP peaks. 

New risk-targeting provisions require 

systems to first identify their risk level; 

then, only those systems with the 

greatest risk will need to make 

operational or treatment changes. The 

Stage 2 DBPR, in conjunction with the 

LT2ESWTR, will help public water 

systems deliver safer water to 

Americans with the benefits of 

disinfection to control pathogens and 

with fewer risks from DBPs. 

B. What Does the Stage 2 DBPR Require? 

The risk-targeting components of the 

Stage 2 DBPR focus the greatest amount 

of change where the greatest amount of 

risk may exist. Therefore, the provisions 

of the Stage 2 DBPR focus first on 

identifying the higher risks through the 

Initial Distribution System Evaluation 

(IDSE). The rule then addresses 

reducing exposure and lowering DBP 

peaks in distribution systems by using 

a new method to determine MCL 

compliance (locational running annual 

average (LRAA)), defining operational 

evaluation levels, and regulating 

consecutive systems. This section 

briefly describes the requirements of 

this final rule. More detailed 

information on the regulatory 

requirements for this rule can be found 

in Section IV. 

1. Initial Distribution System Evaluation 

The first provision, designed to 

identify higher risk systems, is the 

Initial Distribution System Evaluation 

(IDSE). The purpose of the IDSE is to 

identify Stage 2 DBPR compliance 

monitoring sites that represent each 

system’s highest levels of DBPs. Because 

Stage 2 DBPR compliance will be 

determined at these new monitoring 

sites, only those systems that identify 

elevated concentrations of TTHM and 

HAA5 will need to make treatment or 

process changes to bring the system into 

compliance with the Stage 2 DBPR. By 

identifying compliance monitoring sites 

with the highest concentrations of 

TTHM and HAA5 in each system’s 

distribution system, the IDSE will offer 

increased assurance that MCLs are being 

met across the distribution system and 

that customers are receiving more 

equitable public health protection. Both 

treatment changes and awareness of 

TTHM and HAA5 levels resulting from 

the IDSE will allow systems to better 

control for distribution system peaks. 

The IDSE is designed to offer 

flexibility to public water systems. The 

IDSE requires TTHM and HAA5 

monitoring for one year on a regular 

schedule that is determined by source 

water type and system size. 

Alternatively, systems have the option 

of performing a site-specific study based 

on historical data, water distribution 

system models, or other data; and 

waivers are available under certain 

circumstances. The IDSE requirements 

are discussed in Sections IV.E, IV.F., 

and IV.G of this preamble and in 

subpart U of the rule language. 

2. Compliance and Monitoring 

Requirements 

As in Stage 1, the Stage 2 DBPR 

focuses on monitoring for and reducing 

concentrations of two classes of DBPs: 

total trihalomethanes (TTHM) and 

haloacetic acids (HAA5). These two 

groups of DBPs act as indicators for the 

various byproducts that are present in 

water disinfected with chlorine or 

chloramine. This means that 

concentrations of TTHM and HAA5 are 

monitored for compliance, but their 

presence in drinking water is 

representative of many other 

chlorination DBPs that may also occur 

in the water; thus, a reduction in TTHM 

and HAA5 generally indicates an overall 

reduction of DBPs. 

The second provision of the Stage 2 

DBPR is designed to address spatial 

variations in DBP exposure through a 

new compliance calculation (referred to 

as locational running annual average) 

for TTHM and HAA5 MCLs. The MCL 

values remain the same as in the Stage 

1. The Stage 1 DBPR running annual 

average (RAA) calculation allowed some 

locations within a distribution system to 

have higher DBP annual averages than 

others as long as the system-wide 

average was below the MCL. The Stage 

2 DBPR bases compliance on a 

locational running annual average 

(LRAA) calculation, where the annual 

average at each sampling location in the 

distribution system will be used to 

determine compliance with the MCLs of 

0.080 mg/L and 0.060 mg/L for TTHM 

and HAA5, respectively. The LRAA will 

reduce exposures to high DBP 

concentrations by ensuring that each 

monitoring site is in compliance with 

the MCLs as an annual average, while 

providing all customers drinking water 

that more consistently meets the MCLs. 

A more detailed discussion of Stage 2 

DBPR MCL requirements can be found 

in Sections IV.C, IV.E, and IV.G of this 

preamble and in § 141.64(b)(2) and (3) 

and subpart V of the rule language. 

The number of compliance 

monitoring sites is based on the 


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392 Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 

population served and the source water 

type. EPA believes that populationbased monitoring provides better risktargeting and is easier to implement. 

Section IV.G describes population-based 

monitoring and how it affects systems 

complying with this rule. 

The Stage 2 DBPR includes new 

MCLGs for chloroform, 

monochloroacetic acid, and 

trichloroacetic acid, but these new 

MCLGs do not affect the MCLs for 

TTHM or HAA5. 

3. Operational Evaluation Levels 

The IDSE and LRAA calculation will 

lead to lower DBP concentrations 

overall and reduce short term exposures 

to high DBP concentrations in certain 

areas, but this strengthened approach to 

regulating DBPs will still allow 

individual DBP samples above the MCL 

even when systems are in compliance 

with the Stage 2 DBPR. Today’s rule 

requires systems that exceed operational 

evaluation levels (referred to as 

significant excursions in the proposed 

rule) to evaluate system operational 

practices and identify opportunities to 

reduce DBP concentrations in the 

distribution system. This provision will 

curtail peaks by providing systems with 

a proactive approach to remain in 

compliance. Operational evaluation 

requirements are discussed in greater 

detail in Section IV.H. 

4. Consecutive Systems 

The Stage 2 DBPR also contains 

provisions for regulating consecutive 

systems, defined in the Stage 2 DBPR as 

public water systems that buy or 

otherwise receive some or all of their 

finished water from another public 

water system. Uniform regulation of 

consecutive systems provided by the 

Stage 2 DBPR will ensure that 

consecutive systems deliver drinking 

water that meets applicable DBP 

standards, thereby providing better, 

more equitable public health protection. 

More information on regulation of 

consecutive systems can be found in 

Sections IV.B, IV.E, and IV.G. 

C. Correction of § 141.132 

Section 553 of the Administrative 

Procedure Act, 5 U.S.C. 553(b)(B), 

provides that, when an agency for good 

cause finds that notice and public 

procedure are impracticable, 

unnecessary, or contrary to the public 

interest, the agency may issue a rule 

without providing prior notice and an 

opportunity for public comment. In 

addition to promulgating the Stage 2 

regulations, this rule also makes a minor 

correction to the National Primary 

Drinking Water Regulations, specifically 

the Stage 1 Disinfection Byproducts 

Rule. This rule corrects a technical error 

made in the January 16, 2001, Federal 

Register Notice (66 FR 3769) (see page 

3770). This rule restores the following 

sentence that was inadvertently 

removed from § 141.132 (b)(1)(iii), 

‘‘Systems on a reduced monitoring 

schedule may remain on that reduced 

schedule as long as the average of all 

samples taken in the year (for systems 

which must monitor quarterly) or the 

result of the sample (for systems which 

must monitor no more frequently than 

annually) is no more than 0.060 mg/L 

and 0.045 mg/L for TTHMs and HAA5, 

respectively.’’ This text had been part of 

the original regulation when it was 

codified in the CFR on December 16, 

1998. However, as a result of a 

subsequent amendment to that 

regulatory text, the text discussed today 

was removed. EPA recognized the error 

only after publication of the new 

amendment, and is now correcting the 

error. EPA is merely restoring to the 

CFR language that EPA had 

promulgated on December 16, 1998. 

EPA is not creating any new rights or 

obligations by this technical correction. 

Thus, additional notice and public 

comment is not necessary. EPA finds 

that this constitutes ‘‘good cause’’ under 

5 U.S.C. 553(b)(B). 

III. Background 

A combination of factors influenced 

the development of the Stage 2 DBPR. 

These include the initial 1992–1994 

Microbial and Disinfection Byproduct 

(M–DBP) stakeholder deliberations and 

EPA’s Stage 1 DBPR proposal (USEPA 

1994); the 1996 Safe Drinking Water Act 

(SDWA) Amendments; the 1996 

Information Collection Rule; the 1998 

Stage 1 DBPR; new data, research, and 

analysis on disinfection byproduct 

(DBP) occurrence, treatment, and health 

effects since the Stage 1 DBPR; and the 

Stage 2 DBPR Microbial and 

Disinfection Byproducts Federal 

Advisory Committee. The following 

sections provide summary background 

information on these subjects. For 

additional information, see the 

proposed Stage 2 DBPR and supporting 

technical material where cited (68 FR 

49548, August 18, 2003) (USEPA 

2003a). 

A. Statutory Requirements and Legal 

Authority 

The SDWA, as amended in 1996, 

authorizes EPA to promulgate a national 

primary drinking water regulation 

(NPDWR) and publish a maximum 

contaminant level goal (MCLG) for any 

contaminant the Administrator 

determines ‘‘may have an adverse effect 

on the health of persons,’’ is ‘‘known to 

occur or there is a substantial likelihood 

that the contaminant will occur in 

public water systems with a frequency 

and at levels of public health concern,’’

and for which ‘‘in the sole judgement of 

the Administrator, regulation of such 

contaminant presents a meaningful 

opportunity for health risk reduction for 

persons served by public water 

systems’’ (SDWA section 1412(b)(1)(A)). 

MCLGs are non-enforceable health goals 

set at a level at which ‘‘no known or 

anticipated adverse effects on the health 

of persons occur and which allows an 

adequate margin of safety.’’ These 

health goals are published at the same 

time as the NPDWR (SDWA sections 

1412(b)(4) and 1412(a)(3)). 

SDWA also requires each NPDWR for 

which an MCLG is established to 

specify an MCL that is as close to the 

MCLG as is feasible (sections 1412(b)(4) 

and 1401(1)(C)). The Agency may also 

consider additional health risks from 

other contaminants and establish an 

MCL ‘‘at a level other than the feasible 

level, if the technology, treatment 

techniques, and other means used to 

determine the feasible level would 

result in an increase in the health risk 

from drinking water by—(i) increasing 

the concentration of other contaminants 

in drinking water; or (ii) interfering with 

the efficacy of drinking water treatment 

techniques or processes that are used to 

comply with other national primary 

drinking water regulations’’ (section 

1412(b)(5)(A)). When establishing an 

MCL or treatment technique under this 

authority, ‘‘the level or levels or 

treatment techniques shall minimize the 

overall risk of adverse health effects by 

balancing the risk from the contaminant 

and the risk from other contaminants 

the concentrations of which may be 

affected by the use of a treatment 

technique or process that would be 

employed to attain the maximum 

contaminant level or levels’’ (section 

1412(b)(5)(B)). In today’s rule, the 

Agency is establishing MCLGs and 

MCLs for certain DBPs, as described in 

Section IV. 

Finally, section 1412(b)(2)(C) of the 

Act requires EPA to promulgate a Stage 

2 DBPR. Consistent with statutory 

provisions for risk balancing (section 

1412(b)(5)(B)), EPA is finalizing the 

LT2ESWTR concurrently with the Stage 

2 DBPR to ensure simultaneous 

protection from microbial and DBP 

risks. 

B. What is the Regulatory History of the 

Stage 2 DBPR and How Were 

Stakeholders Involved? 

This section first summarizes the 

existing regulations aimed at controlling 


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levels of DBPs in drinking water. The 

Stage 2 DBPR establishes regulatory 

requirements beyond these rules that 

target high risk systems and provide for 

more equitable protection from DBPs 

across the entire distribution system. 

Next, this section summarizes the 

extensive stakeholder involvement in 

the development of the Stage 2 DBPR. 

1. Total Trihalomethanes Rule 

The first rule to regulate DBPs was 

promulgated on November 29, 1979. 

The Total Trihalomethanes Rule (44 FR 

68624, November 29, 1979) (USEPA 

1979) set an MCL of 0.10 mg/L for total 

trihalomethanes (TTHM). Compliance 

was based on the running annual 

average (RAA) of quarterly averages of 

all samples collected throughout the 

distribution system. This TTHM 

standard applied only to community 

water systems using surface water and/ 

or ground water that served at least 

10,000 people and added a disinfectant 

to the drinking water during any part of 

the treatment process. 

2. Stage 1 Disinfectants and Disinfection 

Byproducts Rule 

The Stage 1 DBPR, finalized in 1998 

(USEPA 1998a), applies to all 

community and nontransient 

noncommunity water systems that add 

a chemical disinfectant to water. The 

rule established maximum residual 

disinfectant level goals (MRDLGs) and 

enforceable maximum residual 

disinfectant level (MRDL) standards for 

three chemical disinfectants—chlorine, 

chloramine, and chlorine dioxide; 

maximum contaminant level goals 

(MCLGs) for three trihalomethanes 

(THMs), two haloacetic acids (HAAs), 

bromate, and chlorite; and enforceable 

maximum contaminant level (MCL) 

standards for TTHM, five haloacetic 

acids (HAA5), bromate (calculated as 

running annual averages (RAAs)), and 

chlorite (based on daily and monthly 

sampling). The Stage 1 DBPR uses 

TTHM and HAA5 as indicators of the 

various DBPs that are present in 

disinfected water. Under the Stage 1 

DBPR, water systems that use surface 

water or ground water under the direct 

influence of surface water and use 

conventional filtration treatment are 

required to remove specified 

percentages of organic materials, 

measured as total organic carbon (TOC), 

that may react with disinfectants to form 

DBPs. Removal is achieved through 

enhanced coagulation or enhanced 

softening, unless a system meets one or 

more alternative compliance criteria. 

The Stage 1 DBPR was one of the first 

rules to be promulgated under the 1996 

SDWA Amendments (USEPA 1998a). 

EPA finalized the Interim Enhanced 

Surface Water Treatment Rule (63 FR 

69477, December 16, 1998) (USEPA 

1998b) at the same time as the Stage 1 

DBPR to ensure simultaneous 

compliance and address risk tradeoff 

issues. Both rules were products of 

extensive Federal Advisory Committee 

deliberations and final consensus 

recommendations in 1997. 

3. Stakeholder Involvement 

a. Federal Advisory Committee 

process. EPA reconvened the M-DBP 

Advisory Committee in March 1999 to 

develop recommendations on issues 

pertaining to the Stage 2 DBPR and 

LT2ESWTR. The Stage 2 M-DBP 

Advisory Committee consisted of 21 

organizational members representing 

EPA, State and local public health and 

regulatory agencies, local elected 

officials, Native American Tribes, large 

and small drinking water suppliers, 

chemical and equipment manufacturers, 

environmental groups, and other 

stakeholders. Technical support for the 

Advisory Committee’s discussions was 

provided by a technical working group 

established by the Advisory Committee. 

The Advisory Committee held ten 

meetings from September 1999 to July 

2000, which were open to the public, 

with an opportunity for public comment 

at each meeting. 

The Advisory Committee carefully 

considered extensive new data on the 

occurrence and health effects of DBPs, 

as well as costs and potential impacts 

on public water systems. In addition, 

they considered risk tradeoffs associated 

with treatment changes. Based upon this 

detailed technical evaluation, the 

committee concluded that a targeted 

protective public health approach 

should be taken to address exposure to 

DBPs beyond the requirements of the 

Stage 1 DBPR. While there had been 

substantial research to date, the 

Advisory Committee also concluded 

that significant uncertainty remained 

regarding the risk associated with DBPs 

in drinking water. After reaching these 

conclusions, the Advisory Committee 

developed an Agreement in Principle 

(65 FR 83015, December 29, 2000) 

(USEPA 2000a) that laid out their 

consensus recommendations on how to 

further control DBPs in public water 

systems, which are reflected in today’s 

final rule. 

In the Agreement in Principle, the 

Advisory Committee recommended 

maintaining the MCLs for TTHM and 

HAA5 at 0.080 mg/L and 0.060 mg/L, 

respectively, but changing the 

compliance calculation in two phases to 

facilitate systems moving from the 

running annual average (RAA) 

calculation to a locational running 

annual average (LRAA) calculation. In 

the first phase, systems would continue 

to comply with the Stage 1 DBPR MCLs 

as RAAs and, at the same time, comply 

with MCLs of 0.120 mg/L for TTHM and 

0.100 mg/L for HAA5 calculated as 

LRAAs. RAA calculations average all 

samples collected within a distribution 

system over a one-year period, but 

LRAA calculations average all samples 

taken at each individual sampling 

location in a distribution system during 

a one-year period. Systems would also 

carry out an Initial Distribution System 

Evaluation (IDSE) to select compliance 

monitoring sites that reflect higher 

TTHM and HAA5 levels occurring in 

the distribution system. The second 

phase of compliance would require 

MCLs of 0.080 mg/L for TTHM and 

0.060 mg/L for HAA5, calculated as 

LRAAs at individual monitoring sites 

identified through the IDSE. The first 

phase has been dropped in the final 

rule, as discussed in section IV.C. 

The Agreement in Principle also 

provided recommendations for 

simultaneous compliance with the 

LT2ESWTR so that the reduction of 

DBPs does not compromise microbial 

protection. The complete text of the 

Agreement in Principle (USEPA 2000a) 

can be found online at 

www.regulations.gov. 

b. Other outreach processes. EPA 

worked with stakeholders to develop 

the Stage 2 DBPR through various 

outreach activities other than the MDBP Federal Advisory Committee 

process. The Agency consulted with 

State, local, and Tribal governments; the 

National Drinking Water Advisory 

Committee (NDWAC); the Science 

Advisory Board (SAB); and Small Entity 

Representatives (SERs) and small 

system operators (as part of an Agency 

outreach initiative under the Regulatory 

Flexibility Act). Section VII includes a 

complete description of the many 

stakeholder activities which contributed 

to the development of the Stage 2 DBPR. 

Additionally, EPA posted a preproposal draft of the Stage 2 DBPR 

preamble and regulatory language on an 

EPA Internet site on October 17, 2001. 

This public review period allowed 

readers to comment on the Stage 2 

DBPR’s consistency with the Agreement 

in Principle of the Stage 2 M-DBP 

Advisory Committee. EPA received 

important suggestions on this preproposal draft from 14 commenters, 

which included public water systems, 

State governments, laboratories, and 

other stakeholders. 


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C. Public Health Concerns to be 

Addressed 

EPA is promulgating the Stage 2 rule 

to reduce the potential risks of cancer 

and reproductive and developmental 

health effects from DBPs. In addition, 

the provisions of the Stage 2 DBPR 

provide for more equitable public health 

protection. Sections C and D describe 

the general basis for this public health 

concern through reviewing information 

in the following areas: the health effects 

associated with DBPs, DBP occurrence, 

and the control of DBPs. 

1. What Are DBPs? 

Chlorine has been widely used to kill 

disease-causing microbes in drinking 

water. The addition of chlorine in PWSs 

across the U.S. to kill microbial 

pathogens in the water supply has been 

cited as one of the greatest public health 

advances of the twentieth century 

(Okun 2003). For example, during the 

decade 1880–1890, American cities 

experienced an average mortality rate of 

58 per 100,000 from typhoid, which was 

commonly transmitted through 

contaminated water. By 1938, this rate 

had fallen to 0.67 deaths per 100,000, 

largely due to improved treatment of 

drinking water (Blake 1956). 

During the disinfection process, 

organic and inorganic material in source 

waters can combine with chlorine and 

certain other chemical disinfectants to 

form DBPs. More than 260 million 

people in the U.S. are exposed to 

disinfected water and DBPs (USEPA 

2005a). Although chlorine is the most 

commonly applied disinfectant, other 

disinfectants, including ozone, chlorine 

dioxide, chloramine, and ultraviolet 

radiation, are in use. In combination 

with these, all surface water systems 

must also use either chlorine or 

chloramine to maintain a disinfectant 

residual in their distribution system. 

The kind of disinfectant used can 

produce different types and levels of 

disinfectant byproducts in the drinking 

water. 

Many factors affect the amount and 

kinds of DBPs in drinking water. Areas 

in the distribution system that have had 

longer contact time with chemical 

disinfectants tend to have higher levels 

of DBPs, such as sites farther from the 

treatment plant, dead ends in the 

system, and small diameter pipes. The 

makeup and source of the water also 

affect DBP formation. Different types of 

organic and inorganic material will form 

different types and levels of DBPs. Other 

factors, such as water temperature, 

season, pH, and location within the 

water purification process where 

disinfectants are added, can affect DBP 

formation within and between water 

systems. 

THMs and HAAs are widely occurring 

classes of DBPs formed during 

disinfection with chlorine and 

chloramine. The four THMs (TTHM) 

and five HAAs (HAA5) measured and 

regulated in the Stage 2 DBPR act as 

indicators for DBP occurrence. There are 

other known DBPs in addition to a 

variety of unidentified DBPs present in 

disinfected water. THMs and HAAs 

typically occur at higher levels than 

other known and unidentified DBPs 

(McGuire et al. 2002; Weinberg et al. 

2002). The presence of TTHM and 

HAA5 is representative of the 

occurrence of many other chlorination 

DBPs; thus, a reduction in the TTHM 

and HAA5 generally indicates an overall 

reduction of DBPs. 

2. DBP Health Effects 

Since the mid 1980’s, epidemiological 

studies have supported a potential 

association between bladder cancer and 

chlorinated water and possibly also 

with colon and rectal cancers. In 

addition, more recent health studies 

have reported potential associations 

between chlorinated drinking water and 

reproductive and developmental health 

effects. 

Based on a collective evaluation of 

both the human epidemiology and 

animal toxicology data on cancer and 

reproductive and developmental health 

effects discussed below and in 

consideration of the large number of 

people exposed to chlorinated 

byproducts in drinking water (more 

than 260 million), EPA concludes that 

(1) new cancer data since Stage 1 

strengthen the evidence of a potential 

association of chlorinated water with 

bladder cancer and suggests an 

association for colon and rectal cancers, 

(2) current reproductive and 

developmental health effects data do not 

support a conclusion at this time as to 

whether exposure to chlorinated 

drinking water or disinfection 

byproducts causes adverse 

developmental or reproductive health 

effects, but do support a potential health 

concern, and (3) the combined health 

data indicate a need for public health 

protection beyond that provided by the 

Stage 1 DBPR. 

This section summarizes the key 

information in the areas of cancer, 

reproductive, and developmental health 

studies that EPA used to arrive at these 

conclusions. Throughout this writeup, 

EPA uses ‘weight of evidence,’

‘causality,’ and ‘hazard’ as follows: 

• A ‘weight of evidence’ evaluation is 

a collective evaluation of all pertinent 

information. Judgement about the 

weight of evidence involves 

considerations of the quality and 

adequacy of data and consistency of 

responses. These factors are not scored 

mechanically by adding pluses and 

minuses; they are judged in 

combination. 

• Criteria for determining ‘causality’

include consistency, strength, and 

specificity of association, a temporal 

relationship, a biological gradient (doseresponse relationship), biological 

plausibility, coherence with multiple 

lines of evidence, evidence from human 

populations, and information on agent’s 

structural analogues (USEPA 2005i). 

Additional considerations for individual 

study findings include reliable exposure 

data, statistical power and significance, 

and freedom from bias and 

confounding. 

• The term ‘hazard’ describes not a 

definitive conclusion, but the possibility 

that a health effect may be attributed to 

a certain exposure, in this case 

chlorinated water. Analyses done for the 

Stage 2 DBPR follow the 1999 EPA 

Proposed Guidelines for Carcinogenic 

Risk Assessment (USEPA 1999a). In 

March 2005, EPA updated and finalized 

the Cancer Guidelines and a 

Supplementary Children’s Guidance, 

which include new considerations on 

mode of action for cancer risk 

determination and additional potential 

risks due to early childhood exposure 

(USEPA 2005i; USEPA 2005j). 

Conducting the cancer evaluation using 

the 2005 Cancer Guidelines would not 

result in any change from the existing 

analysis. With the exception of 

chloroform, no mode of action has been 

established for other specific regulated 

DBPs. Although some of the DBPs have 

given mixed mutagenicity and 

genotoxicity results, having a positive 

mutagenicity study does not necessarily 

mean that a chemical has a mutagenic 

mode of action. The extra factor of 

safety for children’s health protection 

does not apply because the new 

Supplementary Children’s Guidance 

requires application of the children’s 

factor only when a mutagenic mode of 

action has been identified. 

a. Cancer health effects. The following 

section briefly discusses cancer 

epidemiology and toxicology 

information EPA analyzed and some 

conclusions of these studies and reports. 

Further discussion of these studies and 

EPA’s conclusions can be found in the 

proposed Stage 2 DBPR (USEPA 2003a) 

and the Economic Analysis for the Final 

Stage 2 Disinfectants and Disinfection 

Byproducts Rule (Economic Analysis 

(EA)) (USEPA 2005a). 

Human epidemiology studies and 

animal toxicology studies have 


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examined associations between 

chlorinated drinking water or DBPs and 

cancer. While EPA cannot conclude 

there is a causal link between exposure 

to chlorinated surface water and cancer, 

EPA believes that the available research 

indicates a potential association 

between bladder cancer and exposure to 

chlorinated drinking water or DBPs. 

EPA also believes the available research 

suggests a possible association between 

rectal and colon cancers and exposure 

to chlorinated drinking water or DBPs. 

This is based on EPA’s evaluation of all 

available cancer studies. The next two 

sections focus on studies published 

since the Stage 1 DBPR. Conclusions are 

based on the research as a whole. 

i. Epidemiology. A number of 

epidemiological studies have been 

conducted to investigate the 

relationship between exposure to 

chlorinated drinking water and various 

cancers. These studies contribute to the 

overall evidence on potential human 

health hazards from exposure to 

chlorinated drinking water. 

Epidemiology studies provide useful 

health effects information because they 

reflect human exposure to a drinking 

water DBP mixture through multiple 

routes of intake such as ingestion, 

inhalation and dermal absorption. The 

greatest difficulty with conducting 

cancer epidemiology studies is the 

length of time between exposure and 

effect. Higher quality studies have 

adequately controlled for confounding 

and have limited the potential for 

exposure misclassification, for example, 

using DBP levels in drinking water as 

the exposure metric as opposed to type 

of source water. Study design 

considerations for interpreting cancer 

epidemiology data include sufficient 

follow-up time to detect disease 

occurrence, adequate sample size, valid 

ascertainment of cause of the cancer, 

and reduction of potential selection bias 

in case-control and cohort studies (by 

having comparable cases and controls 

and by limiting loss to follow-up). 

Epidemiology studies provide extremely 

useful information on human exposure 

to chlorinated water, which 

complement single chemical, high dose 

animal data. 

In the Stage 1 DBPR, EPA concluded 

that the epidemiological evidence 

suggested a potential increased risk for 

bladder cancer. Some key studies EPA 

considered for Stage 1 include Cantor et 

al. (1998), Doyle et al. (1997), Freedman 

et al. (1997), King and Marrett (1996), 

McGeehin et al. (1993), Cantor et al. 

(1987), and Cantor et al. (1985). Several 

studies published since the Stage 1 

DBPR continue to support an 

association between increased risk of 

bladder cancer and exposure to 

chlorinated surface water (Chevrier et 

al. 2004; Koivusalo et al. 1998; Yang et 

al. 1998). One study found no effects on 

a biomarker of genotoxicity in urinary 

bladder cells from TTHM exposure 

(Ranmuthugala et al. 2003). 

Epidemiological reviews and metaanalyses generally support the 

possibility of an association between 

chlorinated water or THMs and bladder 

cancer (Villanueva et al. 2004; 

Villanueva et al. 2003; Villanueva et al. 

2001; Mills et al. 1998). The World 

Health Organization (WHO 2000) found 

data inconclusive or insufficient to 

determine causality between 

chlorinated water and any health 

endpoint, although they concluded that 

the evidence is better for bladder cancer 

than for other cancers. 

In the Stage 1 DBPR, EPA concluded 

that early studies suggested a small 

possible increase in rectal and colon 

cancers from exposure to chlorinated 

surface waters. The database of studies 

on colon and rectal cancers continues to 

support a possible association, but 

evidence remains mixed. For colon 

cancer, one newer study supports the 

evidence of an association (King et al. 

2000a) while others showed 

inconsistent findings (Hildesheim et al. 

1998; Yang et al. 1998). Rectal cancer 

studies are also mixed. Hildesheim et al. 

(1998) and Yang et al. (1998) support an 

association with rectal cancer while 

King et al. (2000a) did not. A review of 

colon and rectal cancer concluded 

evidence was inconclusive but that 

there was a stronger association for 

rectal cancer and chlorination DBPs 

than for colon cancer (Mills et al. 1998). 

The WHO (2000) review reported that 

studies showed weak to moderate 

associations with colon and rectal 

cancers and chlorinated surface water or 

THMs but that evidence is inadequate to 

evaluate these associations. 

Recent studies on kidney, brain, and 

lung cancers and DBP exposure support 

a possible association (kidney: Yang et 

al. 1998, Koivusalo et al. 1998; brain: 

Cantor et al. 1999; lung: Yang et al. 

1998). However, so few studies have 

examined these endpoints that 

definitive conclusions cannot be made. 

Studies on leukemia found little or no 

association with DBPs (Infante-Rivard et 

al. 2002; Infante-Rivard et al. 2001). A 

recent study did not find an association 

between pancreatic cancer and DBPs 

(Do et al. 2005). A study researching 

multiple cancer endpoints found an 

association between THM exposure and 

all cancers when grouped together 

(Vinceti et al. 2004). More details on the 

cancer epidemiology studies since the 

Stage 1 DBPR are outlined in Table II.D–

1. 

TABLE II.D–1.—SUMMARY OF CANCER EPIDEMIOLOGY STUDIES REVIEWED FOR STAGE 2 DBPR 

Study type Exposure(s) studied Outcome(s) 

measured Findings 

Author(s) 

Do et al. 2005 Case-control 

study in 

Canada, 

1994–1997.

Estimated chlorinated DBPs, 

chloroform, BDCM concentrations.

Pancreatic cancer.No association was found between pancreatic cancer and 

exposure to chlorinated DBPs, chloroform, or BDCM. 

Chevrier et al. 

2004..

Case-control 

study in 

France, 

1985–1987.

Compared THM levels, duration of exposure, and 3 

types of water treatment 

(ozonation, chlorination, 

ozonation/chlorination).

Bladder cancer. A statistically significant decreased risk of bladder cancer 

was found as duration of exposure to ozonated water increased. This was evident with and without adjustment 

for other exposure measures. A small association was 

detected for increased bladder cancer risk and duration 

of exposure to chlorinated surface water and with the estimated THM content of the water, achieving statistical 

significance only when adjusted for duration of ozonated 

water exposures. Effect modification by gender was 

noted in the adjusted analyses. 


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TABLE II.D–1.—SUMMARY OF CANCER EPIDEMIOLOGY STUDIES REVIEWED FOR STAGE 2 DBPR—Continued 

Study type Exposure(s) studied Outcome(s) 

measured Findings 

Vinceti et al. 

2004.

Retrospective 

cohort study 

in Italy, 

1987–1999.

Standardized mortality ratios 

from all causes vs. cancer 

for consumers drinking 

water with high THMs.

15 cancers including colon, 

rectum, and 

bladder.

Mortality ratio from all cancers showed a statistically significant small increase for males consuming drinking water 

with high THMs. For females, an increased mortality ratio 

for all cancers was seen but was not statistically significant. Stomach cancer in men was the only individual 

cancer in which a statistically significant excess in mortality was detected for consumption of drinking water with 

high THMs. 

Ranmuthugala 

et al. 2003.

Cohort study 

in 3 Australian communities, 

1997.

Estimated dose of TTHM, 

chloroform, and bromoform 

from routinely-collected 

THM measurements and 

fluid intake diary.

Frequency of 

micronuclei in 

urinary bladder epithelial 

cells.

Relative risk estimates for DNA damage to bladder cells for 

THM dose metrics were near 1.0. The study provides no 

evidence that THMs are associated with DNA damage to 

bladder epithelial cells, and dose-response patterns were 

not detected. 

Infante-Rivard 

et al. 2002.

Populationbased casecontrol study 

in Quebec, 

1980–1993.

Estimated prenatal and postnatal exposure to THMs 

and polymorphisms in two 

genes.

Acute 

lymphoblastic 

leukemia.

Data are suggestive, but imprecise, linking DNA variants 

with risk of acute lymphoblastic leukemia associated with 

drinking water DBPs. The number of genotyped subjects 

for GSTT1 and CYP2E1 genes was too small to be conclusive. 

Infante-Rivard 

et al. 2001.

Populationbased casecontrol study 

in Quebec, 

1980–1993.

Compared water chlorination 

(never, sometimes, always) 

and exposure to TTHMs, 

metals, and nitrates.

Acute 

lymphoblastic 

leukemia.

No increased risk for lymphoblastic leukemia was observed 

for prenatal exposure at average levels of TTHMs, metals or nitrates. However, a non-statistically significant, 

small increased risk was seen for postnatal cumulative 

exposure to TTHMs and chloroform (both at above the 

95th exposure percentile of the distribution for cases and 

controls), for zinc, cadmium, and arsenic, but not other 

metals or nitrates. 

King et al. 

2000a.

Populationbased casecontrol study 

in southern 

Ontario, 

1992–1994.

Compared source of drinking 

water and chlorination status. Estimated TTHM levels, duration of exposure, 

and tap water consumption.

Colon and rectal cancer.Colon cancer risk was statistically associated with cumulative long term exposure to THMs, chlorinated surface 

water, and tap water consumption metrics among males 

only. Exposure-response relationships were evident for 

exposure measures combining duration and THM levels. 

Associations between the exposure measures and rectal 

cancer were not observed for either gender. 

Cantor et al. 

1999.

Populationbased casecontrol study 

in Iowa, 

1984–1987.

Compared level and duration 

of THM exposure (cumulative and average), source 

of water, chlorination, and 

water consumption.

Brain cancer .... Among males, a statistically significant increased risk of 

brain cancer was detected for duration of chlorinated 

versus non-chlorinated source water, especially among 

high-level consumers of tap water. An increased risk of 

brain cancer for high water intake level was found in 

men. No associations were found for women for any of 

the exposure metrics examined. 

Cantor et al. 

1998.

Populationbased casecontrol study 

in Iowa, 

1986–1989.

Compared level and duration 

of THM exposure (cumulative and average), source 

of water, chlorination, and 

water consumption.

Bladder cancer A statistically significant positive association between risk 

of bladder cancer and exposure to chlorinated groundwater or surface water reported for men and for smokers, 

but no association found for male/female non-smokers, 

or for women overall. Limited evidence was found for an 

association between tapwater consumption and bladder 

cancer risk. Suggestive evidence existed for exposure-response effects of chlorinated water and lifetime THM 

measures on bladder cancer risk. 

Hildesheim et 

al. 1998.

Populationbased casecontrol study 

in Iowa, 

1986–1989.

Compared level and duration 

of THM exposure (cumulative and average), source 

of water, chlorination, and 

water consumption.

Colon and rectal cancer.Increased risks of rectal cancer was associated with duration of exposure to chlorinated surface water and any 

chlorinated water, with evidence of an exposure-response relationship. Risk of rectal cancer is statistically 

significant increased with >60 years lifetime exposure to 

THMs in drinking water, and risk increased for individuals 

with low dietary fiber intake. Risks were similar for men 

and women and no effects were observed for tapwater 

measures. No associations were detected for water exposure measures and risk of colon cancer. 

Koivusalo et 

al. 1998.

Populationbased casecontrol study 

in Finland, 

1991–1992.

Estimated residential duration 

of exposure and level of 

drinking water mutagenicity.

Bladder and 

kidney cancer.

Drinking water mutagenicity was associated with a small, 

statistically significant, exposure-related excess risk for 

kidney and bladder cancers among men; weaker associations were detected for mutagenic water and bladder 

or kidney cancer among women. The effect of mutagenicity on bladder cancer was modified by smoking status, 

with an increased risk among non-smokers. 


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TABLE II.D–1.—SUMMARY OF CANCER EPIDEMIOLOGY STUDIES REVIEWED FOR STAGE 2 DBPR—Continued 

Study type Exposure(s) studied Outcome(s) 

measured Findings 

Yang et al. 

1998.

Cross-sectional study 

in Taiwan, 

1982–1991.

Examined residence in 

chlorinated (mainly surface 

water sources) relative to 

non-chlorinated (mainly private well) water.

Cancer of rectum, lung, 

bladder, kidney, colon, 

and 11 others.

Residence in chlorinating municipalities (vs. nonchlorinating) was statistically significantly associated with 

the following types of cancer in both males and females: 

rectal, lung, bladder, and kidney cancer. Liver cancer 

and all cancers were also statistically significantly elevated in chlorinated towns for males only. Mortality rates 

for cancers of the esophagus, stomach, colon, pancreas, 

prostate, brain, breast, cervix uteri and uterus, and ovary 

were comparable for chlorinated and non-chlorinated residence. 

Doyle et al. 

1997.

Prospective 

cohort study 

in Iowa, 

1987–1993.

Examined chloroform levels 

and source of drinking 

water.

Colon, rectum, 

bladder, and 

8 other cancers in 

women.

Statistically significant increased risk of colon cancer, 

breast cancer and all cancers combined was observed 

for women exposed to chloroform in drinking water, with 

evidence of exposure-response effects. No associations 

were detected between chloroform and bladder, rectum, 

kidney, upper digestive organs, lung, ovary, endometrium, or breast cancers, or for melanomas or nonHodgkin’s lymphoma. Surface water exposure (compared 

to ground water users) was also a significant predictor of 

colon and breast cancer risk. 

Freedman et 

al. 1997.

Populationbased casecontrol study 

in Maryland, 

1975–1992.

Estimated duration of exposure to chlorinated water. 

Compared exposure to 

chlorinated municipal water 

(yes/no).

Bladder cancer There was a weak association between bladder cancer risk 

and duration of exposure to municipal water for male cigarette smokers, as well as an exposure-response relationship. No association was seen for those with no history of smoking, suggesting that smoking may modify a 

possible effect of chlorinated surface water on the risk of 

bladder cancer. 

King and 

Marrett 1996.

Case-control 

study in Ontario, Canada, 1992–

1994.

Compared source of drinking 

water and chlorination status. Estimated TTHM levels, duration of exposure, 

and tap water consumption.

Bladder cancer Statistically significant associations were detected for bladder cancer and chlorinated surface water, duration or 

concentration of THM levels and tap water consumption 

metrics. Population attributable risks were estimated at 

14 to 16 percent. An exposure-response relationship was 

observed for estimated duration of high THM exposures 

and risk of bladder cancer. 

McGeehin et 

al. 1993.

Populationbased casecontrol study 

in Colorado, 

1990–1991.

Compared source of drinking 

water, water treatment, and 

tap water versus bottled 

water. Estimated duration 

of exposure to TTHMs and 

levels of TTHMs, nitrates, 

and residual chlorine.

Bladder cancer Statistically significant associations were detected for bladder cancer and duration of exposure to chlorinated surface water. The risk was similar for males and females 

and among nonsmokers and smokers. The attributable 

risk was estimated at 14.9 percent. High tap water intake 

was associated with risk of bladder cancer in a exposure-response fashion. No associations were detected 

between bladder cancer and levels of TTHMs, nitrates, 

and residual chlorine. 

Cantor et al. 

1987 (and 

Cantor et al. 

1985).

Populationbased casecontrol study 

in 10 areas 

of the U.S., 

1977–1978.

Compared source of drinking 

water. Estimated total beverage and tap water consumption and duration of 

exposure.

Bladder cancer Bladder cancer was statistically associated with duration of 

exposure to chlorinated surface water for women and 

nonsmokers of both sexes. The largest risks were seen 

when both exposure duration and level of tap water ingestion were combined. No association was seen for 

total beverage consumption. 

Reviews/Metaanalyses 

Villanueva et 

al. 2004.

Review and 

meta-analysis of 6 

case-control 

studies.

Individual-based exposure 

estimates to THMs and 

water consumption over a 

40-year period.

Bladder cancer The meta-analysis suggests that risk of bladder cancer in 

men increases with long-term exposure to TTHMs. An 

exposure-response pattern was observed among men 

exposed to TTHMs, with statistically significant risk seen 

at exposures higher than 50 ug/L. No association between TTHMs and bladder cancer was seen for women. 

Villanueva et 

al. 2003 

(and Goebell 

et al. 2004).

Review and 

meta-analysis of 6 

case-control 

studies and 

2 cohort 

studies.

Compared source of water 

and estimated duration of 

exposure to chlorinated 

drinking water.

Bladder cancer The meta-analysis findings showed a moderate excess risk 

of bladder cancer attributable to long-term consumption 

of chlorinated drinking water for both genders, particularly in men. Statistically significance seen with men and 

combined both sexes. The risk was higher when exposure exceeded 40 years. 


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TABLE II.D–1.—SUMMARY OF CANCER EPIDEMIOLOGY STUDIES REVIEWED FOR STAGE 2 DBPR—Continued 

Study type Exposure(s) studied Outcome(s) 

measured Findings 

Villanueva et 

al. 2001.

Qualitative review of 31 

cancer studies.

Compared exposure to TTHM 

levels, mutagenic drinking 

water, water consumption, 

source water, types of disinfection (chlorination and 

chloramination), and residence times.

Cancer of bladder, colon, 

rectum, and 5 

other cancers..

Review found that although results for cancer studies varied and were not always statistically significant, evidence 

for bladder cancer is strongest, and all 10 of the bladder 

cancer studies showed increased cancer risks with ingestion of chlorinated water. The authors felt associations with chlorinated water and cancer of the colon, rectum, pancreas, esophagus, brain, and other cancers 

were inconsistent. 

WHO 2000 ..... Qualitative reviews of various studies 

in Finland, 

U.S., and 

Canada.

Various exposures to THMs. Various cancers Studies reviewed reported weak to moderate increased relative risks of bladder, colon, rectal, pancreatic, breast, 

brain or lung cancer associated with long-term exposure 

to chlorinated drinking water. The authors felt evidence is 

inconclusive for an association between colon cancer 

and long-term exposure to THMs; that evidence is insufficient to evaluate a causal relationship between THMs 

and rectal, bladder, and other cancers. They found no 

association between THMs and increased risk of cardiovascular disease. 

Mills et al. 

1998.

Qualitative review of 22 

studies.

Examined TTHM levels and 

water consumption. Compared source of water and 

2 types of water treatment 

(chlorination and 

chloramination).

Cancer of 

colon, rectum, and 

bladder.

Review suggests possible increases in risks of bladder 

cancer with exposure to chlorinated drinking water. The 

authors felt evidence for increased risk of colon and rectal cancers is inconclusive, though evidence is stronger 

for rectal cancer. 

Overall, bladder cancer data provide 

the strongest basis for quantifying 

cancer risks from DBPs. EPA has chosen 

this endpoint to estimate the primary 

benefits of the Stage 2 DBPR (see 

Section VI). 

ii. Toxicology. Cancer toxicology 

studies provide additional support that 

chlorinated water is associated with 

cancer. In general, EPA uses long term 

toxicology studies that show a dose 

response to derive MCLGs and cancer 

potency factors. Short term studies are 

used for hazard identification and to 

design long term studies. Much of the 

available cancer toxicology information 

was available for the Stage 1 DBPR, but 

there have also been a number of new 

cancer toxicology and mode of action 

studies completed since the Stage 1 

DBPR was finalized in December 1998. 

In support of this rule, EPA has 

developed health criteria documents 

which summarize the available 

toxicology data for brominated THMs 

(USEPA 2005b), brominated HAAs 

(USEPA 2005c), MX (USEPA 2000b), 

MCAA (USEPA 2005d), and TCAA 

(USEPA 2005e). The 2003 IRIS 

assessment of DCAA (USEPA 2003b) 

and an addendum (USEPA 2005k) also 

provides analysis released after Stage 1. 

It summarizes information on exposure 

from drinking water and develops a 

slope factor for DCAA. IRIS also has 

toxicological reviews for chloroform 

(USEPA 2001a), chlorine dioxide and 

chlorite (USEPA 2000c), and bromate 

(USEPA 2001b), and is currently 

reassessing TCAA. 

Slope factors and risk concentrations 

for BDCM, bromoform, DBCM and 

DCAA have been developed and are 

listed in Table II.D–2. For BDCM, 

bromoform, and DBCM, table values are 

derived from the brominated THM 

criteria document (USEPA 2005b), 

which uses IRIS numbers that have been 

updated using the 1999 EPA Proposed 

Guidelines for Carcinogenic Risk 

Assessment (USEPA 1999a). For DCAA, 

the values are derived directly from 

IRIS. 

TABLE II.D–2.—QUANTIFICATION OF CANCER RISK

Disinfection byproduct 

LED 10a ED 10a

Slope 

factor 

(mg/kg/day)¥1

10 ¥6 Risk 

concentration 

(mg/L) 

Slope 

factor 

(mg/kg/day) ¥1

10 ¥6 Risk 

concentration 

(mg/L) 

Bromodichloromethane .................................................................... 0.034 0.001 0.022 0.002 

Bromoform ....................................................................................... 0.0045 0.008 0.0034 0.01 

Dibromochloromethane .................................................................... 0.04 0.0009 0.017 0.002 

Dichloroacetic Acid .......................................................................... 0.048 0.0007 0.015 b 0.0023 b

a LED10 is the lower 95% confidence bound on the (effective dose) ED10 value. ED10 is the estimated dose producing effects in 10% of animals. bThe ED10 risk factors for DCAA have been changed from those given in the comparable table in the proposed Stage 2 DBPR to correct for 

transcriptional errors. 

More research on DBPs is underway 

at EPA and other research institutions. 

Summaries of on-going studies may be 

found on EPA’s DRINK Web site (http:// 

www.epa.gov/safewater/drink/ 

intro.html). Two-year bioassays by the 

National Toxicology Program (NTP) 

released in abstract form have recently 

been completed on BDCM and chlorate. 

The draft abstract on BDCM reported no 

evidence of carcinogenicity when 

BDCM was administered via drinking 


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water (NTP 2005a). Another recent 

study, a modified two-year bioassay on 

BDCM in the drinking water, reported 

little evidence of carcinogenicity 

(George et al. 2002). In a previous NTP 

study, tumors were observed, including 

an increased incidence of kidney, liver, 

and colon tumors, when BDCM was 

administered at higher doses by gavage 

in corn oil (NTP 1987). EPA will 

examine new information on BDCM as 

it becomes available. In the chlorate 

draft abstract, NTP found some evidence 

that it may be a carcinogen (NTP 2004). 

Chlorate is a byproduct of hypochlorite 

and chlorine dioxide systems. A longterm, two-year bioassay NTP study on 

DBA is also complete but has not yet 

undergone peer review (NTP 2005b). 

b. Reproductive and developmental 

health effects. Both human 

epidemiology studies and animal 

toxicology studies have examined 

associations between chlorinated 

drinking water or DBPs and 

reproductive and developmental health 

effects. Based on an evaluation of the 

available science, EPA believes the data 

suggest that exposure to DBPs is a 

potential reproductive and 

developmental health hazard. 

The following section briefly 

discusses the reproductive and 

developmental epidemiology and 

toxicology information available to EPA. 

Further discussion of these studies and 

EPA’s conclusions can be found in the 

proposed Stage 2 DBPR (USEPA 2003a) 

and the Economic Analysis (USEPA 

2005a). 

i. Epidemiology. As discussed 

previously, epidemiology studies have 

the strength of relating human exposure 

to DBP mixtures through multiple 

intake routes. Although the critical 

exposure window for reproductive and 

developmental effects is much smaller 

than that for cancer (generally weeks 

versus years), exposure assessment is 

also a main limitation of reproductive 

and developmental epidemiology 

studies. Exposure assessment 

uncertainties arise from limited data on 

DBP concentrations and maternal water 

usage and source over the course of the 

pregnancy. However, classification 

errors typically push the true risk 

estimate towards the null value (Vineis 

2004). According to Bove et al. (2002), 

‘‘Difficulties in assessing exposure may 

result in exposure misclassification 

biases that would most likely produce 

substantial underestimates of risk as 

well as distorted or attenuated 

exposure-response trends.’’ Studies of 

rare outcomes (e.g., individual birth 

defects) often have limited statistical 

power because of the small number of 

cases being examined. This limits the 

ability to detect statistically significant 

associations for small to moderate 

relative risk estimates. Small sample 

sizes also result in imprecision around 

risk estimates reflected by wide 

confidence intervals. In addition to the 

limitations of individual studies, 

evaluating reproductive and 

developmental epidemiology studies 

collectively is difficult because of the 

methodological differences between 

studies and the wide variety of 

endpoints examined. These factors may 

contribute to inconsistencies in the 

scientific body of literature as noted 

below. 

More recent studies tend to be of 

higher quality because of improved 

exposure assessments and other 

methodological advancements. For 

example, studies that use THM levels to 

estimate exposure tend to be higher 

quality than studies that define 

exposure by source or treatment. These 

factors were taken into account by EPA 

when comparing and making 

conclusions on the reproductive and 

developmental epidemiology literature. 

What follows is a summary of available 

epidemiology literature on reproductive 

and developmental endpoints such as 

spontaneous abortion, stillbirth, neural 

tube and other birth defects, low birth 

weight, and intrauterine growth 

retardation. Information is grouped, 

where appropriate, into three categories 

on fetal growth, viability, and 

malformations, and reviews are 

described separately afterward. Table 

II.D–3 provides a more detailed 

description of each study or review. 

Fetal growth. Many studies looked for 

an association between fetal growth 

(mainly small for gestational age, low 

birth weight, and pre-term delivery) and 

chlorinated water or DBPs. The results 

from the collection of studies as a whole 

are inconsistent. A number of studies 

support the possibility that exposure to 

chlorinated water or DBPs are 

associated with adverse fetal growth 

effects (Infante-Rivard 2004; Wright et 

al. 2004; Wright et al. 2003; Ka ̈lle ́n and 

Robert 2000; Gallagher et al. 1998; 

Kanitz et al. 1996; Bove et al. 1995; 

Kramer et al. 1992). Other studies 

showed mixed results (Porter et al. 

2005; Savitz et al. 2005; Yang 2004) or 

did not provide evidence of an 

association (Toledano et al. 2005; 

Jaakkola et al. 2001; Dodds et al. 1999; 

Savitz et al. 1995) between DBP 

exposure and fetal growth. EPA notes 

that recent, higher quality studies 

provide some evidence of an increased 

risk of small for gestational age and low 

birth weight. 

Fetal viability. While the database of 

epidemiology studies for fetal loss 

endpoints (spontaneous abortion or 

stillbirth) remains inconsistent as a 

whole, there is suggestive evidence of 

an association between fetal loss and 

chlorinated water or DBP exposure. 

Various studies support the possibility 

that exposure to chlorinated water or 

DBPs is associated with decreased fetal 

viability (Toledano et al. 2005; Dodds et 

al. 2004; King et al. 2000b; Dodds et al. 

1999; Waller et al. 1998; Aschengrau et 

al. 1993; Aschengrau et al. 1989). Other 

studies did not support an association 

(Bove et al. 1995) or reported 

inconclusive results (Savitz et al. 2005; 

Swan et al. 1998; Savitz et al. 1995) 

between fetal viability and exposure to 

THMs or tapwater. A recent study by 

King et al. (2005) found little evidence 

of an association between stillbirths and 

haloacetic acids after controlling for 

trihalomethane exposures, though nonstatistically significant increases in 

stillbirths were seen across various 

exposure levels. 

Fetal malformations. A number of 

epidemiology studies have examined 

the relationship between fetal 

malformations (such as neural tube, oral 

cleft, cardiac, or urinary defects, and 

chromosomal abnormalities) and 

chlorinated water or DBPs. It is difficult 

to assess fetal malformations in 

aggregate due to inconsistent findings 

and disparate endpoints being examined 

in the available studies. Some studies 

support the possibility that exposure to 

chlorinated water or DBPs is associated 

with various fetal malformations 

(Cedergren et al. 2002; Hwang et al. 

2002; Dodds and King 2001; Klotz and 

Pyrch 1999; Bove et al. 1995; 

Aschengrau et al. 1993). Other studies 

found little evidence (Shaw et al. 2003; 

Ka ̈lle ́n and Robert 2000; Dodds et al. 

1999; Shaw et al. 1991) or inconclusive 

results (Magnus et al. 1999) between 

chlorinated water or DBP exposure and 

fetal malformations. Birth defects most 

consistently identified as being 

associated with DBPs include neural 

tube defects and urinary tract 

malformations. 

Other endpoints have also been 

examined in recent epidemiology 

studies. One study suggests an 

association between DBPs and 

decreased menstrual cycle length 

(Windham et al. 2003), which, if 

corroborated, could be linked to the 

biological basis of other reproductive 

endpoints observed. No association 

between THM exposure and semen 

quality was found (Fenster et al. 2003). 

More work is needed in both areas to 

support these results. 

Reviews. An early review supported 

an association between measures of fetal 

viability and tap water (Swan et al. 


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1992). Three other reviews found data 

inadequate to support an association 

between reproductive and 

developmental health effects and THM 

exposure (Reif et al. 1996; Craun 1998; 

WHO 2000). Mills et al. (1998) 

examined data on and found support for 

an association between fetal viability 

and malformations and THMs. Another 

review presented to the Stage 2 MDBP 

FACA found some evidence for an 

association with fetal viability and some 

fetal malformations and exposure to 

DBPs but reported that the evidence was 

inconsistent for these endpoints as well 

as for fetal growth (Reif et al. 2000). Reif 

et al. (2000) concluded that the weight 

of evidence from epidemiology studies 

suggests that ‘‘DBPs are likely to be 

reproductive toxicants in humans under 

appropriate exposure conditions,’’ but 

from a risk assessment perspective, data 

are primarily at the hazard 

identification stage. Nieuwenhuijsen et 

al. (2000) found some evidence for an 

association between fetal growth and 

THM exposure and concluded evidence 

for associations with other fetal 

endpoints is weak but gaining weight. A 

qualitative review by Villanueva et al. 

(2001) found evidence generally 

supports a possible association between 

reproductive effects and drinking 

chlorinated water. Graves et al. (2001) 

supports a possible association for fetal 

growth but not fetal viability or 

malformations. More recently, Bove et 

al. (2002) examined and supported an 

association between small for 

gestational age, neural tube defects and 

spontaneous abortion endpoints and 

DBPs. Following a meta-analysis on five 

malformation studies, Hwang and 

Jaakkola (2003) concluded that there 

was evidence which supported 

associations between DBPs and risk of 

birth defects, especially neural tube 

defects and urinary tract defects. 

TABLE II.D–3.—SUMMARY OF REPRODUCTIVE/DEVELOPMENTAL EPIDEMIOLOGY STUDIES

Author(s) Study type Exposure(s) studied Outcome(s) measured Findings 

Porter et al. 

2005.

Cross-sectional study in 

Maryland, 1998–2002.

Estimated THM and 

HAA exposure during 

pregnancy.

Intrauterine growth retardation.No consistent association or dose-response relationship was found between exposure to either 

TTHM or HAA5 and intrauterine growth retardation. Results suggest an increased risk of 

intrauterine growth retardation associated with 

TTHM and HAA5 exposure in the third trimester, although only HAA5 results were statistically significant. 

Savitz et al. 

2005.

Population-based prospective cohort study 

in three communities 

around the U.S., 

2000–2004.

Estimated TTHM, HAA9, 

and TOC exposures 

during pregnancy. Indices examined included concentration, 

ingested amount, exposure from showering and bathing, 

and an integration of 

all exposures combined.

Early and late pregnancy loss, preterm 

birth, small for gestational age, and term 

birth weight.

No association with pregnancy loss was seen 

when looking at high exposure of TTHM compared to low exposure of TTHM. When examining individual THMs, a statistically significant 

association was found between 

bromodichloromethane (BDCM) and pregnancy loss. A similar, non-statistically significant association was seen between 

dibromochloromethane (DBCM) and pregnancy loss. Some increased risk was seen for 

losses at greater than 12 weeks’ gestation for 

TTHM, BDCM, and TOX (total organic halide), 

but most results generally did not provide support for an association. Preterm birth showed 

a small inverse relationship with DBP exposure (i.e. higher exposures showed less 

preterm births), but this association was weak. 

TTHM exposure of 80 ug/L was associated 

with twice the risk for small for gestational age 

during the third trimester and was statistically 

significant. 

Toledano et 

al. 2005.

Large cross-sectional 

study in England, 

1992–1998.

Linked mother’s residence at time of delivery to modeled estimates of TTHM levels 

in water zones.

Stillbirth, low birth 

weight.

A significant association between TTHM and risk 

of stillbirth, low birth weight, and very low birth 

weight was observed in one of the three regions. When all three regions were combined, 

small, but non-significant, excess risks were 

found between all three outcomes and TTHM 

and chloroform. No associations were observed between reproductive risks and BDCM 

or total brominated THMs. 

Dodds et al. 

2004 (and 

King et al. 

2005).

Population-based casecontrol study in Nova 

Scotia and Eastern 

Ontario, 1999–2001.

Estimated THM and 

HAA exposure at residence during pregnancy. Linked water 

consumption and 

showering/bathing to 

THM exposure.

Stillbirth ......................... A statistically significant association was observed between stillbirths and exposure to 

total THM, BDCM, and chloroform. Associations were also detected for metrics, which incorporated water consumption, showering and 

bathing habits. Elevated relative risks were observed for intermediate exposures for total 

HAA and DCAA measures; TCAA and 

brominated HAA exposures showed no association. No statistically significant associations 

or dose-response relationships between any 

HAAs and stillbirth were detected after controlling for THM exposure. 


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TABLE II.D–3.—SUMMARY OF REPRODUCTIVE/DEVELOPMENTAL EPIDEMIOLOGY STUDIES—Continued 

Author(s) Study type Exposure(s) studied Outcome(s) measured Findings 

InfanteRivard 

2004.

Case-control study of 

newborns in Montreal, 

1998–2000.

Estimated THM levels 

and water consumption during pregnancy. 

Exposure from showering and presence of 

two genetic 

polymorphisms.

Intrauterine growth retardation.No associations were found between exposure 

to THMs and intrauterine growth retardation. 

However, a significant effect was observed between THM exposure and intrauterine growth 

retardation for newborns with the CYP2E1 

gene variant. Findings suggest that exposure 

to THMs at the highest levels can affect fetal 

growth but only in genetically susceptible 

newborns. 

Wright et al. 

2004.

Large cross-sectional 

study: Massachusetts, 

1995–1998.

Estimated maternal 

third-trimester exposures to TTHMs, chloroform, BDCM, total 

HAAs, DCA, TCA, MX 

and mutagenicity in 

drinking water.

Birth weight, small for 

gestational age, 

preterm delivery, gestational age.

Statistically significant reductions in mean birth 

weight were observed for BDCM, chloroform, 

and mutagenic activity. An exposure-response 

relationship was found between THM exposure and reductions in mean birth weight and 

risk of small for gestational age. There was no 

association between preterm delivery and elevated levels of HAAs, MX, or mutagenicity. A 

reduced risk of preterm delivery was observed 

with high THM exposures. Gestational age 

was associated with exposure to THMs and 

mutagenicity. 

Yang et al. 

2004 (and 

Yang et 

al. 2000).

Large cross-sectional 

studies in Taiwan, 

1994–1996.

Compared maternal 

consumption of 

chlorinated drinking 

water (yes/no).

Low birth weight, 

preterm delivery.

Residence in area supplied with chlorinated 

drinking water showed a statistically significant 

association with preterm delivery. No association was seen between chlorinated drinking 

water and low birth weight. 

Fenster et 

al. 2003.

Small prospective study 

in California, 1990–

1991.

Examined TTHM levels 

within the 90 days 

preceding semen collection.

Sperm motility, sperm 

morphology.

No association between TTHM level and sperm 

mobility or morphology. BDCM was inversely 

associated with linearity of sperm motion. 

There was some suggestion that water consumption and other ingestion metrics may be 

associated with different indicators of semen 

quality. 

Shaw et al. 

2003.

2 case-control maternal 

interview studies: CA, 

1987–1991.

Estimated THM levels 

for mothers’ residences from before 

conception through 

early pregnancy.

Neural tube defects, oral 

clefts, selected heart 

defects.

No associations or exposure-response relation 

were observed between malformations and 

TTHMs in either study. 

Windham et 

al. 2003.

Prospective study: CA, 

1990–1991.

Estimated exposure to 

THMs through showering and ingestion 

over average of 5.6 

menstrual cycles per 

woman.

Menstrual cycle, follicular phase length 

(in days).

Findings suggest that THM exposure may affect 

ovarian function. All brominated THM compounds were associated with significantly 

shorter menstrual cycles with the strongest 

finding for chlorodibromomethane. There was 

little association between TTHM exposure and 

luteal phase length, menses length, or cycle 

variability. 

Wright et al. 

2003.

Cross-sectional study: 

Massachusetts, 1990.

Estimated TTHM exposure in women during 

pregnancy (average 

for pregnancy and 

during each trimester).

Birth weight, small for 

gestational age, 

preterm delivery, gestational age.

Statistically significant associations between 2nd 

trimester and pregnancy average TTHM exposure and small for gestational age and fetal 

birth weight were detected. Small, statistically 

significant increases in gestational duration/ 

age were observed at increased TTHM levels, 

but there was little evidence of an association 

between TTHM and preterm delivery or low 

birth weight. 

Cedergren 

et al. 2002.

Retrospective case-control study: Sweden, 

1982–1997.

Examined maternal 

periconceptional DBP 

levels and used GIS 

to assign water supplies.

Cardiac defects ............. Exposure to chlorine dioxide in drinking water 

showed statistical significance for cardiac defects. THM concentrations of 10 ug/L and 

higher were significantly associated with cardiac defects. No excess risk for cardiac defect 

and nitrate were seen. 

Hwang et al. 

2002.

Large cross-sectional 

study in Norway, 

1993–1998.

Compared exposure to 

chlorination (yes/no) 

and water color levels 

for mother’s residence 

during pregnancy.

Birth defects (neural 

tube defects, cardiac, 

respiratory system, 

oral cleft, urinary 

tract).

Risk of any birth defect, cardiac, respiratory system, and urinary tract defects were significantly associated with water chlorination. Exposure to chlorinated drinking water was statistically significantly associated with risk of 

ventricular septal defects, and an exposure-response pattern was seen. No other specific 

defects were associated with the exposures 

that were examined. 


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TABLE II.D–3.—SUMMARY OF REPRODUCTIVE/DEVELOPMENTAL EPIDEMIOLOGY STUDIES—Continued 

Author(s) Study type Exposure(s) studied Outcome(s) measured Findings 

Dodds and 

King 2001.

Population-based retrospective cohort in 

Nova Scotia, 1988–

1995.

Estimated THM, chloroform, and 

bromodichloromethane (BDCM) exposure.

Neural tube defects, 

cardiovascular defects, cleft defects, 

chromosomal abnormalities.

Exposure to BDCM was associated with increased risk of neural tube defects, cardiovascular anomalies. Chloroform was not associated with neural tube defects, but was associated with chromosomal abnormalities. No association between THM and cleft defects were 

detected. 

Jaakkola et 

al. 2001.

Large cross-sectional 

study in Norway, 

1993–1995.

Compared chlorination 

(yes/no) and water 

color (high/low) for 

mother during pregnancy.

Low birth weight, small 

for gestational age, 

preterm delivery.

No evidence found for association between prenatal exposure to chlorinated drinking water 

and low birth weight or small for gestational 

age. A reduced risk of preterm delivery was 

noted for exposure to chlorinated water with 

high color content. 

Ka ̈lle ́n and 

Robert 

2000.

Large cross-sectional 

cohort study in Sweden, 1985–1994.

Linked prenatal exposure to drinking water 

disinfected with various methods (no 

chlorine, chlorine dioxide only, sodium 

hypochlorite only).

Gestational duration, 

birth weight, intrauterine growth, mortality, congenital malformations, and other 

birth outcomes.

A statistically significant difference was found for 

short gestational duration and low birth weight 

among infants whose mother resided in areas 

using sodium hypochlorite, but not for chlorine 

dioxide. Sodium hypochlorite was also associated with other indices of fetal development 

but not with congenital defects. No other effects were observed for intrauterine growth, 

childhood cancer, infant mortality, low Apgar 

score, neonatal jaundice, or neonatal 

hypothyroidism in relation to either disinfection 

method. 

Dodds et al. 

1999 (and 

King et al. 

2000b).

Population-based retrospective cohort study 

in Nova Scotia, 1988–

1995.

Estimated TTHM level 

for women during 

pregnancy.

Low birth weight, 

preterm birth, small 

for gestational age, 

stillbirth, chromosomal 

abnormalities, neural 

tube defects, cleft defects, major cardiac 

defects.

A statistically significant increased risk for stillbirths and high total THMs and specific THMs 

during pregnancy was detected, with higher 

risks observed among asphyxia-related stillbirths. Bromodichloromethane had the strongest association and exhibited an exposure-response pattern. There was limited evidence of 

an association between THM level and other 

reproductive outcomes. No congenital anomalies were associated with THM exposure, except for a non-statistically significant association with chromosomal abnormalities. 

Klotz and 

Pyrch 

1999 (and 

Klotz and 

Pyrch 

1998).

Population-based casecontrol study in New 

Jersey, 1993–1994.

Estimated exposure of 

pregnant mothers to 

TTHMs and HAAs, 

and compared source 

of water.

Neural tube defects ...... A significant association was seen between exposure to THMs and neural tube defects. No 

associations were observed for neural tube 

defects and haloacetic acids or 

haloacetonitriles. 

Magnus et 

al. 1999.

Large cross-sectional 

study in Norway, 

1993–1995.

Compared chlorination 

(yes/no) and water 

color (high/low) at 

mothers’ residences 

at time of birth.

Birth defects (neural 

tube defects, major 

cardiac, respiratory, 

urinary, oral cleft).

Statistically significant associations were seen 

between urinary tract defects and chlorination 

and high water color (high content of organic 

compounds). No associations were detected 

for other outcomes or all birth defects combined. A non-statistically significant, overall excess risk of birth defects was seen within municipalities with chlorination and high water 

color compared to municipalities with no 

chlorination and low color. 

Gallagher et 

al. 1998.

Retrospective cohort 

study of newborns in 

Colorado, 1990–1993.

Estimated THM levels in 

drinking water during 

third trimester of pregnancy.

Low birth weight, term 

low birthweight, and 

preterm delivery.

Weak, non-statistically significant association 

with low birth weight and TTHM exposure during the third trimester. Large statistically significant increase for term low birthweight at 

highest THM exposure levels. No association 

between preterm delivery and THM exposure. 

Swan et al. 

1998.

Prospective study in 

California, 1990–1991.

Compared consumption 

of cold tap water to 

bottled water during 

early pregnancy.

Spontaneous abortion ... Pregnant women who drank cold tap water compared to those who consumed no cold tap 

water showed a significant finding for spontaneous abortion at one of three sites. 


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TABLE II.D–3.—SUMMARY OF REPRODUCTIVE/DEVELOPMENTAL EPIDEMIOLOGY STUDIES—Continued 

Author(s) Study type Exposure(s) studied Outcome(s) measured Findings 

Waller et al. 

1998 (and 

Waller et 

al. 2001).

Prospective cohort in 

California, 1989–1991.

Estimated TTHM levels 

during first trimester 

of pregnancy via ingestion and showering.

Spontaneous abortion ... Statistically significant increased risk between 

high intake of TTHMs and spontaneous abortion compared to low intake. BDCM statistically associated with increased spontaneous 

abortion; other THMs not. Reanalysis of exposure yielded less exposure misclassification 

and relative risks similar in magnitude to earlier study. An exposure-response relationship 

was seen between spontaneous abortion and 

ingestion exposure to TTHMs. 

Kanitz et al. 

1996.

Cross-sectional study in 

Italy, 1988–1989.

Compared 3 types of 

water treatment (chlorine dioxide, sodium 

hypochlorite, and 

chlorine dioxide/sodium hypochlorite).

Low birth weight, body 

length, cranial circumference, preterm delivery, and other effects.

Smaller body length and small cranial circumference showed statistical significant association with maternal exposure to chlorinated 

drinking water. Neonatal jaundice linked statistically to prenatal exposure to drinking water 

treated with chlorine dioxide. Length of pregnancy, type of delivery, and birthweight 

showed no association. 

Bove et al. 

1995 (and 

Bove et 

al. 1992a 

& 1992b).

Large cohort cross-sectional study in New 

Jersey, 1985–1988.

Examined maternal exposure to TTHM and 

various other contaminants.

Low birth weight, fetal 

deaths, small for gestational age, birth defects (neural tube defects, oral cleft, central nervous system, 

major cardiac).

Weak, statistically significant increased risk 

found for higher TTHM levels with small for 

gestational age, neural tube defects, central 

nervous system defects, oral cleft defects, and 

major cardiac defects. Some association with 

higher TTHM exposure and low birth weight. 

No effect seen for preterm birth, very low birth 

weight, or fetal deaths. 

Savitz et al. 

1995.

Population-based casecontrol study: North 

Carolina, 1988–1991.

Examined TTHM concentration at residences and water 

consumption (during 

first and third trimesters).

Spontaneous abortion, 

preterm delivery, low 

birth weight.

There was a statistically significant increased 

miscarriage risk with high THM concentration, 

but THM intake (based on concentration times 

consumption level) was not related to pregnancy outcome. No associations were seen for 

preterm delivery or low birth weight. Water 

source was not related to pregnancy outcome 

either, with the exception of a non-significant, 

increased risk of spontaneous abortion for bottled water users. There was a non-statistically 

significant pattern of reduced risk with increased consumption of water for all three outcomes. 

Aschengrau 

et al. 1993.

Case-control study in 

Massachusetts, 1977–

1980.

Source of water and 2 

types of water treatment (chlorination, 

chloramination).

Neonatal death, stillbirth, congenital 

anomalies.

There was a non-significant, increased association between frequency of stillbirths and maternal exposure to chlorinated versus 

chloraminated surface water. An increased risk 

of urinary track and respiratory track defects 

and chlorinated water was detected. Neonatal 

death and other major malformations showed 

no association. No increased risk seen for any 

adverse pregnancy outcomes for surface 

water versus ground and mixed water use. 

Kramer et 

al. 1992.

Population-based casecontrol study in Iowa, 

1989–1990.

Examined chloroform, 

DCBM, DBCM, and 

bromoform levels and 

compared type of 

water source (surface, 

shallow well, deep 

well).

Low birth weight, prematurity, intrauterine 

growth retardation.

Statistically significant increased risk for intrauterine growth retardation effects from chloroform exposure were observed. Non-significant 

increased risks were observed for low birth 

weight and chloroform and for intrauterine 

growth retardation and DCBM. No intrauterine 

growth retardation or low birth weight effects 

were seen for the other THMs, and no effects 

on prematurity were observed for any of the 

THMs. 

Shaw et al. 

1991 (and 

Shaw et 

al. 1990).

Small case-control 

study: Santa Clara 

County, CA, 1981–

1983.

Estimated chlorinated 

tap water consumption, mean maternal 

TTHM level, showering/bathing exposure at residence during first trimester.

Congenital cardiac 

anomalies.

Following reanalysis, no association between 

cardiac anomalies and TTHM level were observed. 

Aschengrau 

et al. 1989.

Case-control study in 

Massachusetts, 1976–

1978.

Source of water and exposure to metals and 

other contaminants.

Spontaneous abortion ... A statistically significantly association was detected between surface water source and frequency of spontaneous abortion. 


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TABLE II.D–3.—SUMMARY OF REPRODUCTIVE/DEVELOPMENTAL EPIDEMIOLOGY STUDIES—Continued 

Author(s) Study type Exposure(s) studied Outcome(s) measured Findings 

Reviews/ 

Metaanalyses 

Hwang and 

Jakkola 

2003.

Review and meta-analysis of 5 studies.Compared DBP levels, 

source of water, chlorine residual, color 

(high/low), and 2 

types of disinfection: 

chlorination and 

chloramination.

Birth defects (respiratory 

system, urinary system, neural tube defects, cardiac, oral 

cleft).

The meta-analysis supports an association between exposure to chlorination by-products 

and the risk of any birth defect, particularly the 

risk of neural tube defects and urinary system 

defects. 

Bove et al. 

2002.

Qualitative review of 14 

studies.

Examined THM levels. 

Compared drinking 

water source and type 

of water treatment.

Birth defects, small for 

gestational age, low 

birth weight, preterm 

delivery, spontaneous 

abortion, fetal death.

Review found the studies of THMs and adverse 

birth outcomes provide moderate evidence for 

associations with small for gestational age, 

neural tube defects, and spontaneous abortions. Authors felt risks may have been underestimated and exposure-response relationships distorted due to exposure 

misclassification. 

Graves et al. 

2001.

Review of toxicological 

and epidemiological 

studies using a weight 

of evidence approach.

Examined water consumption, duration of 

exposure, THM levels, 

HAA levels, and other 

contaminants. Compared source of 

water, water treatment, water color 

(high/low), etc.

Low birth weight, 

preterm delivery, 

small for gestational 

age, intrauterine 

growth retardation, 

specific birth defects, 

neonatal death, decreased fertility, fetal 

resorption, and other 

effects.

Weight of evidence suggested positive association with DBP exposure for growth retardation 

such as small for gestational age or intrauterine growth retardation and urinary tract defects. Review found no support for DBP exposure and low birth weight, preterm delivery, 

some specific birth defects, and neonatal 

death, and inconsistent findings for all birth defects, all central nervous system defects, neural tube defects, spontaneous abortion, and 

stillbirth. 

Villanueva et 

al. 2001.

Qualitative review of 14 

reproductive and developmental health effect studies.

Compared exposure to 

TTHM levels, mutagenic drinking water, 

water consumption, 

source water, types of 

disinfection 

(chlorination and 

chloramination), and 

residence times.

Spontaneous abortion, 

low birth weight, small 

for gestational age, 

neural tube defects, 

other reproductive 

and developmental 

outcomes.

Review found positive associations between increased spontaneous abortion, low birth 

weight, small for gestational age, and neural 

tube defects and drinking chlorinated water in 

most studies, although not always with statistical significance. 

Nieuwenhuijsen et al. 

2000.

Qualitative review of numerous toxicological 

and epidemiological 

studies.

Examined levels of various DBPs, water consumption, and duration of exposure. 

Compared water 

color, water treatment, 

source of water, etc.

Low birth weight, 

preterm delivery, 

spontaneous abortions, stillbirth, birth 

defects, etc.

The review supports some evidence of association between THMs and low birth weight, but 

inconclusive. Review found no evidence of association between THMs and preterm delivery, 

and that associations for other outcomes 

(spontaneous abortions, stillbirth, and birth defects) were weak but gaining weight. 

Reif et al. 

2000.

Qualitative reviews of 

numerous epidemiological studies.

Compared source of 

water supply and 

methods of disinfection. Estimated TTHM 

levels.

Birth weight, low birth 

weight, intrauterine 

growth retardation, 

small for gestational 

age, preterm deliver, 

somatic parameters, 

neonatal jaundice, 

spontaneous abortion, 

stillbirth, developmental anomalies.

Weight of evidence suggested DBPs are reproductive toxicants in humans under appropriate 

exposure conditions. The review reports findings between TTHMs and effects on fetal 

growth, fetal viability, and congenital anomalies as inconsistent. Reviewers felt data are at 

the stage of hazard identification and did not 

suggest a dose-response pattern of increasing 

risk with increasing TTHM concentration. 

WHO 2000 Qualitative reviews of 

various studies in Finland, U.S., and Canada.

Various exposures to 

THMs.

Various reproductive 

and developmental effects.

Review found some support for an association 

between increased risks of neural tube defects 

and miscarriage and THM exposure. Other associations have been observed, but the authors believed insufficient data exist to assess 

any of these associations. 

Craun, ed. 

1998.

Qualitative review of 10 

studies, focus on California cohort study.

Examined THM levels 

and water consumption, and compared 

source of water and 

water treatment (chlorine, chloramines, 

chlorine dioxide).

Stillbirth, neonatal 

death, spontaneous 

abortion, low birth 

weight, preterm delivery, intrauterine 

growth retardation, 

neonatal jaundice, 

birth defects.

Associations between DBPs and various reproductive effects were seen in some epidemiological studies, but the authors felt these results do not provide convincing evidence for a 

causal relationship between DBPs and reproductive effects. 


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TABLE II.D–3.—SUMMARY OF REPRODUCTIVE/DEVELOPMENTAL EPIDEMIOLOGY STUDIES—Continued 

Author(s) Study type Exposure(s) studied Outcome(s) measured Findings 

Mills et al. 

1998.

Qualitative review of 22 

studies.

Examined TTHM levels 

and water consumption. Compared 

source of water and 2 

types of water treatment (chlorination and 

chloramination).

Various reproductive 

and developmental effects.

Review found studies suggest possible increases 

in adverse reproductive and developmental effects, such as increased spontaneous abortion 

rates, small for gestational age, and fetal 

anomalies, but that insufficient evidence exists 

to establish a causal relationship. 

Reif et al. 

1996.

Review of 3 case-control studies and 1 

cross-sectional study.

Examined THM levels at 

residences, dose consumption, chloroform. 

Compared source of 

waters and 2 types of 

water treatment 

(chlorination and 

chloramination).

Birth defects (central 

nervous system, neural tube defects, cardiac, oral cleft, respiratory, urinary tract), 

spontaneous abortion, 

low birth weight, 

growth retardation, 

preterm delivery, 

intrauterine growth retardation, stillbirth, 

neonatal death.

Studies reviewed suggest that exposure to DBPs 

may increase intrauterine growth retardation, 

neural tube defects, major heart defects, and 

oral cleft defects. Review found epidemiologic 

evidence supporting associations between exposure to DBPs and adverse pregnancy outcomes to be sparse and to provide an inadequate basis to identify DBPs as a reproductive or developmental hazard. 

Swan et al. 

1992.

Qualitative review of 5 

studies in Santa Clara 

County, CA (Deane et 

al. 1992, Wrensch et 

al. 1992, HertzPicciotto et al. 1992, 

Windham et al. 1992, 

Fenster et al. 1992).

Compared maternal 

consumption of residence tap water to 

bottled water.

Spontaneous abortion ... Four of the studies reviewed suggest that 

women drinking bottled water during the first 

trimester of pregnancy may have reduced risk 

of spontaneous abortion relative to drinking 

tap water. No association seen in the fifth 

study. Review concluded that if findings are 

causal and not due to chance or bias, data 

suggest a 10–50% increase in spontaneous 

abortion risk for pregnant women drinking tap 

water over bottled water. 

ii. Toxicology. To date, the majority of 

reproductive and developmental 

toxicology studies have been short term 

and higher dose. Many of these studies 

are summarized in a review by Tyl 

(2000). A summary of this review and of 

additional studies is provided in the 

proposed Stage 2 DBPR (USEPA 2003a). 

Individual DBP supporting documents 

evaluate and assess additional studies as 

well (USEPA 2000b; USEPA 2000c; 

USEPA 2001a; USEPA 2001b; USEPA 

2003b; USEPA 2005b; USEPA 2005c; 

USEPA 2005d; USEPA 2005e; USEPA 

2005k). A number of recent studies have 

been published that include in vivo and 

in vitro assays to address mechanism of 

action. Overall, reproductive and 

developmental toxicology studies 

indicate a possible reproductive/ 

developmental health hazard although 

they are preliminary in nature for the 

majority of DBPs, and the dose-response 

characteristics of most DBPs have not 

been quantified. Some of the 

reproductive effects of DCAA were 

quantified as part of the RfD 

development process, and impacts of 

DCAA on testicular structure are one of 

the critical effects in the study that is 

the basis of the RfD (USEPA 2003b). 

A few long term, lower dose studies 

have been completed. Christian et al. 

(2002a and 2002b) looked for an 

association between BDCM and DBAA 

and reproductive and developmental 

endpoints. The authors identified a 

NOAEL and LOAEL of 50 ppm and 150 

ppm, respectively, based on delayed 

sexual maturation for BDCM and a 

NOAEL and LOAEL of 50 ppm and 250 

ppm based on abnormal 

spermatogenesis for DBAA. The authors 

concluded that similar effects in 

humans would only be seen at levels 

many orders of magnitude higher than 

that of current drinking water levels. As 

discussed in more detail in the 

proposal, EPA believes that because of 

key methodological differences 

indicated as being important in other 

studies (Bielmeier et al. 2001; Bielmeier 

et al. 2004; Kaydos et al. 2004; 

Klinefelter et al. 2001; Klinefelter et al. 

2004), definitive conclusions regarding 

BDCM and DBAA cannot be drawn. 

Other multi-generation research 

underway includes a study on BCAA, 

but this research is not yet published. 

Biological plausibility for the effects 

observed in reproductive and 

developmental epidemiological studies 

has been demonstrated through various 

toxicological studies on some individual 

DBPs (e.g., Bielmeier et al. 2001; 

Bielmeier et al. 2004; Narotsky et al. 

1992; Chen et al. 2003; Chen et al. 

2004). Some of these studies were 

conducted at high doses, but similarity 

of effects observed between toxicology 

studies and epidemiology studies 

strengthens the weight of evidence for a 

possible association between adverse 

reproductive and developmental health 

effects and exposure to chlorinated 

surface water. 

c. Conclusions. EPA’s weight of 

evidence evaluation of the best available 

science on carcinogenicity and 

reproductive and developmental effects, 

in conjunction with the widespread 

exposure to DBPs, supports the 

incremental regulatory changes in 

today’s rule that target lowering DBPs 

and providing equitable public health 

protection. 

EPA believes that the cancer 

epidemiology and toxicology literature 

provide important information that 

contributes to the weight of evidence for 

potential health risks from exposure to 

chlorinated drinking water. At this time, 

the cancer epidemiology studies support 

a potential association between 

exposure to chlorinated drinking water 

and cancer, but evidence is insufficient 

to establish a causal relationship. The 

epidemiological evidence for an 

association between DBP exposure and 

colon and rectal cancers is not as 

consistent as it is for bladder cancer, 

although similarity of effects reported in 

animal toxicity and human 

epidemiology studies strengthens the 

evidence for an association with colon 

and rectal cancers. EPA believes that the 

overall cancer epidemiology and 

toxicology data support the decision to 


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pursue additional DBP control measures 

as reflected in the Stage 2 DBPR. 

Based on the weight of evidence 

evaluation of the reproductive and 

developmental epidemiology data, EPA 

concludes that a causal link between 

adverse reproductive or developmental 

health effects and exposure to 

chlorinated drinking water or DBPs has 

not been established, but that there is a 

potential association. Despite 

inconsistent findings across studies, 

some recent studies continue to suggest 

associations between DBP exposure and 

various adverse reproductive and 

developmental effects. In addition, data 

from a number of toxicology studies, 

although the majority of them were 

conducted using high doses, 

demonstrate biological plausibility for 

some of the effects observed in 

epidemiology studies. EPA concludes 

that no dose-response relationship or 

causal link has been established 

between exposure to chlorinated 

drinking water or disinfection 

byproducts and adverse developmental 

or reproductive health effects. EPA’s 

evaluation of the best available studies, 

particularly epidemiology studies is that 

they do not support a conclusion at this 

time as to whether exposure to 

chlorinated drinking water or 

disinfection byproducts causes adverse 

developmental and reproductive health 

effects, but do provide an indication of 

a potential health concern that warrants 

incremental regulatory action beyond 

the Stage 1 DBPR. 

D. DBP Occurrence and DBP Control 

New information on the occurrence of 

DBPs in distribution systems raises 

issues about the protection provided by 

the Stage 1 DBPR. This section presents 

new occurrence and treatment 

information used to identify key issues 

and to support the development of the 

Stage 2 DBPR. For a more detailed 

discussion see the proposed Stage 2 

DBPR (USEPA 2003a). For additional 

information on occurrence of regulated 

and nonregulated DBPs, see the 

Occurrence Assessment for the Final 

Stage 2 Disinfectants and Disinfection 

Byproducts Rule (USEPA 2005f). 

1. Occurrence 

EPA, along with the M-DBP Advisory 

Committee, collected, developed, and 

evaluated new information that became 

available after the Stage 1 DBPR was 

published. The Information Collection 

Rule (ICR) (USEPA 1996) provided new 

field data on DBP exposure for large 

water systems and new study data on 

the effectiveness of several DBP control 

technologies. The unprecedented 

amount of information collected under 

the ICR was supplemented by a survey 

conducted by the National Rural Water 

Association, data provided by various 

States, the Water Utility Database 

(which contains data collected by the 

American Water Works Association), 

and ICR Supplemental Surveys for small 

and medium water systems. 

After analyzing the DBP occurrence 

data, EPA and the Advisory Committee 

reached three significant conclusions 

that in part led the Advisory Committee 

to recommend further control of DBPs 

in public water systems. First, the data 

from the Information Collection Rule 

showed that the RAA compliance 

calculation under the Stage 1 DBPR 

allows elevated TTHM or HAA5 levels 

to regularly occur at some locations in 

the distribution system while the overall 

average of TTHM or HAA5 levels at all 

DBP monitoring locations is below the 

MCLs of the Stage 1 DBPR. Customers 

served at those sampling locations with 

DBP levels that are regularly above 

0.080 mg/L TTHM and 0.060 mg/L 

HAA5 experience higher exposure 

compared to customers served at 

locations where these levels are 

consistently met. 

Second, the new data demonstrated 

that DBP levels in single samples can be 

substantially above 0.080 mg/L TTHM 

and 0.060 mg/L HAA5. Some customers 

receive drinking water with 

concentrations of TTHM and HAA5 up 

to 75% above 0.080 mg/L and 0.060 mg/ 

L, respectively, even when their water 

system is in compliance with the Stage 

1 DBPR. Some studies support an 

association between acute exposure to 

DBPs and potential adverse 

reproductive and developmental health 

effects (see Section III.C for more detail). 

Third, the data from the Information 

Collection Rule revealed that the highest 

TTHM and HAA5 levels can occur at 

any monitoring site in the distribution 

system. In fact, the highest 

concentrations did not occur at the 

maximum residence time locations in 

more than 50% of all ICR samples. The 

fact that the locations with the highest 

DBP levels vary in different public 

water systems indicates that the Stage 1 

DBPR monitoring may not accurately 

represent the high DBP concentrations 

that actually exist in distribution 

systems, and that additional monitoring 

is needed to identify distribution system 

locations with elevated DBP levels. 

These data showed that efforts beyond 

the Stage 1 DBPR are needed to provide 

more equitable protection from DBP 

exposure across the entire distribution 

system. The incremental regulatory 

changes made under the Stage 2 DBPR 

meet this need by reevaluating the 

locations of DBP monitoring sites and 

addressing high DBP concentrations that 

occur at particular locations or in single 

samples within systems in compliance. 

2. Treatment 

The analysis of the new treatment 

study data confirmed that certain 

technologies are effective at reducing 

DBP concentrations. Bench- and pilotscale studies for granular activated 

carbon (GAC) and membrane 

technologies required by the 

Information Collection Rule provided 

information on the effectiveness of the 

two technologies. Other studies found 

UV light to be highly effective for 

inactivating Cryptosporidium and 

Giardia at low doses without promoting 

the formation of DBPs (Malley et al. 

1996; Zheng et al. 1999). This new 

treatment information adds to the 

treatment options available to utilities 

for controlling DBPs beyond the 

requirements of the Stage 1 DBPR. 

E. Conclusions for Regulatory Action 

After extensive analysis of available 

data and rule options considered by the 

Advisory Committee and review of 

public comments on the proposed Stage 

2 DBPR (USEPA, 2003a), EPA is 

finalizing a Stage 2 DBPR control 

strategy consistent with the key 

elements of the Agreement in Principle 

signed in September 2000 by the 

participants in the Stage 2 M–DBP 

Advisory Committee. EPA believes that 

exposure to chlorinated drinking water 

may be associated with cancer, 

reproductive, and developmental health 

risks. EPA determined that the risktargeting measures recommended in the 

Agreement in Principle will require 

only those systems with the greatest risk 

to make treatment and operational 

changes and will maintain simultaneous 

protection from potential health 

concerns from DBPs and microbial 

contaminants. EPA has carefully 

evaluated and expanded upon the 

recommendations of the Advisory 

Committee and public comments to 

develop today’s rule. EPA also made 

simplifications where possible to 

minimize complications for public 

water systems as they transition to 

compliance with the Stage 2 DBPR 

while expanding public health 

protection. The requirements of the 

Stage 2 DBPR are described in detail in 

Section IV of this preamble. 

IV. Explanation of Today’s Action 

A. MCLGs 

MCLGs are set at concentration levels 

at which no known or anticipated 

adverse health effects occur, allowing 

for an adequate margin of safety. 


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Establishment of an MCLG for each 

specific contaminant is based on the 

available evidence of carcinogenicity or 

noncancer adverse health effects from 

drinking water exposure using EPA’s 

guidelines for risk assessment. MCLGs 

are developed to ensure they are 

protective of the entire population. 

Today’s rule provides MCLGs for 

chloroform and two haloacetic acids, 

monochloroacetic acid (MCAA) and 

trichloroacetic acid (TCAA). 

1. Chloroform MCLG 

a. Today’s rule. The final MCLG for 

chloroform is 0.07 mg/L. The MCLG was 

calculated using toxicological evidence 

that the carcinogenic effects of 

chloroform are due to sustained tissue 

toxicity. EPA is not changing the other 

THM MCLGs finalized in the Stage 1 

DBPR. 

b. Background and analysis. The 

MCLG for chloroform is unchanged 

from the proposal. The MCLG is 

calculated using a reference dose (RfD) 

of 0.01 mg/kg/day and an adult tap 

water consumption of 2 L per day for a 

70 kg adult. A relative source 

contribution (RSC) of 20% was used in 

accordance with Office of Water’s 

current approach for deriving RSC 

through consideration of data that 

indicate that other routes and sources of 

exposure may potentially contribute 

substantially to the overall exposure to 

chloroform. See the proposed Stage 2 

DBPR (USEPA 2003a) for a detailed 

discussion of the chloroform MCLG. 

MCLG for Chloroform (0.01 mg/kg /day)(70 kg)(0.2)

2 L/day = = 0.07 mg/L (rounded)

Based on an analysis of the available 

scientific data on chloroform, EPA 

believes that the chloroform doseresponse is nonlinear and that 

chloroform is likely to be carcinogenic 

only under high exposure conditions 

(USEPA 2001a). This assessment is 

supported by the principles of the 1999 

EPA Proposed Guidelines for 

Carcinogen Risk Assessment (USEPA 

1999a) and reconfirmed by the 2005 

final Cancer Guidelines (USEPA 2005i). 

The science in support of a nonlinear 

approach for estimating the 

carcinogenicity of chloroform was 

affirmed by the Chloroform Risk 

Assessment Review Subcommittee of 

the EPA SAB Executive Committee 

(USEPA 2000d). Since the nonzero 

MCLG is based on a mode of action 

consideration specific to chloroform, it 

does not affect the MCLGs of other 

trihalomethanes. 

c. Summary of major comments. EPA 

received many comments in support of 

the proposed MCLG calculation for 

chloroform, although some commenters 

disagreed with a non-zero MCLG. 

At this time, based on an analysis of 

all the available scientific data on 

chloroform, EPA concludes that 

chloroform is likely to be carcinogenic 

to humans only under high exposure 

conditions that lead to cytotoxicity and 

regenerative hyperplasia and that 

chloroform is not likely to be 

carcinogenic to humans under 

conditions that do not cause 

cytotoxicity and cell regeneration 

(USEPA 2001a). Therefore, the doseresponse is nonlinear, and the MCLG is 

set at 0.07 mg/L. This conclusion has 

been reviewed by the SAB (USEPA 

2000d), who agree that nonlinear 

approach is most appropriate for the 

risk assessment of chloroform; it also 

remains consistent with the principles 

of the 1999 EPA Proposed Guidelines 

for Carcinogenic Risk Assessment 

(USEPA 1999a) and the final Cancer 

Guidelines ( USEPA 2005i), which 

allow for nonlinear extrapolation. 

EPA also received some comments 

requesting a combined MCLG for THMs 

or HAAs. This is not appropriate 

because these different chemicals have 

different health effects. 

2. HAA MCLGs: TCAA and MCAA 

a. Today’s rule. Today’s rule finalizes 

the proposed Stage 2 MCLG for TCAA 

of 0.02 mg/L (USEPA 2003a) and sets an 

MCLG for MCAA of 0.07 mg/L. EPA is 

not changing the other HAA MCLGs 

finalized in the Stage 1 DBPR (USEPA 

1998a). 

b. Background and analysis. The Stage 

1 DBPR included an MCLG for TCAA of 

0.03 mg/L and did not include an MCLG 

for MCAA (USEPA 1998a). Based on 

toxicological data published after the 

Stage 1 DBPR, EPA proposed new 

MCLGs for TCAA and MCAA of 0.02 

mg/L and 0.03 mg/L, respectively, in the 

Stage 2 proposal (USEPA 2003a). The 

proposed TCAA MCLG and its 

supporting analysis is being finalized 

unchanged in today’s final rule. The 

MCLG calculation for MCAA is revised 

in this final rule, based on a new 

reference dose, as discussed later. See 

the proposed Stage 2 DBPR (USEPA 

2003a) for a detailed discussion of the 

calculation of the MCLGs. 

TCAA. The MCLG for TCAA was 

calculated based on the RfD of 0.03 mg/ 

kg/day using a 70 kg adult body weight, 

a 2 L/day drinking water intake, and a 

relative source contribution of 20%. An 

additional tenfold risk management 

factor has been applied to account for 

the possible carcinogenicity of TCAA. 

This approach is consistent with EPA 

policy. TCAA induces liver tumors in 

mice (Ferreira-Gonzalez et al. 1995; 

Pereira 1996; Pereira and Phelps 1996; 

Tao et al. 1996; Latendresse and Pereira 

1997; Pereira et al. 1997) but not in rats 

(DeAngelo et al. 1997). Much of the 

recent data on the carcinogenicity of 

TCAA have focused on examining the 

carcinogenic mode(s) of action. 

However, at this time, neither the 

bioassay nor the mechanistic data are 

sufficient to support the development of 

a slope factor from which to quantify 

the cancer risk. 

MCLG for TCAA (0.03 mg/kg/day)(70 kg)(0.2)

(2 L/day)(10) = = 0.02 mg/L (rounded)

The chronic bioassay for TCAA by 

DeAngelo et al. (1997) was selected as 

the critical study for the development of 

the RfD. In this chronic drinking water 

study, a dose-response was noted for 

several endpoints and both a LOAEL 

and NOAEL were determined. The data 

are consistent with the findings in both 

the Pereira (1996) chronic drinking 

water study and the Mather et al. (1990) 

subchronic drinking water study. The 

RfD of 0.03 mg/kg/day is based on the 

NOAEL of 32.5 mg/kg/day for liver 

histopathological changes in rats 

(DeAngelo et al. 1997). A composite 

uncertainty factor of 1000 was applied 

in the RfD determination. A default 

uncertainty factor of 10 was applied to 


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the RfD to account for extrapolation 

from an animal study because data to 

quantify rat-to-human differences in 

toxicokinetics or toxicodynamics are not 

available. The default uncertainty factor 

of 10 was used to account for human 

variability in the absence of data on 

differences in human susceptibility. 

Although subchronic and chronic 

studies of TCAA have been reported for 

multiple species, many studies have 

focused on liver lesions and a full 

evaluation of a wide range of potential 

target organs has not been conducted in 

two different species. In addition, there 

has been no multi-generation study of 

reproductive toxicity and the data from 

teratology studies in rats provide 

LOAEL values but no NOAEL for 

developmental toxicity. Thus, an 

additional uncertainty factor of 10 was 

used to account for database 

insufficiencies. 

The MCLG calculation also includes a 

relative source contribution (RSC) of 

20%. The RSC was derived consistent 

with Office of Water’s current approach 

for deriving RSC. In addition to 

disinfected water, foods are expected to 

contribute to daily exposure to TCAA 

(Raymer et al. 2001, 2004; Reimann et 

al. 1996). Some of the TCAA in foods 

comes from cleaning and cooking foods 

in chlorinated water. Additional TCAA 

is found in some foods because of the 

widespread use of chlorine as a 

sanitizing agent in the food industry 

(USFDA 1994). EPA was not able to 

identify any dietary surveys or duplicate 

diet studies of TCAA in the diet. TCAA 

also has been identified in rain water, 

suggesting some presence in the 

atmosphere (Reimann et al. 1996); 

however, due to the low volatility (0.5—

0.7 mm Hg at 25 °C) of TCAA, exposure 

from ambient air is expected to be 

minimal. Dermal exposure to 

disinfected water is also unlikely to be 

significant. A study by Xu et al. (2002) 

reports that dermal exposure from 

bathing and showering is only 0.01% of 

that from oral exposure. In addition, the 

solvents trichloroethylene, 

tetrachlorethylene, 1,1,1-trichloroethane 

(often found in ambient air and drinking 

water), and the disinfection byproduct 

chloral hydrate all contribute to the 

body’s TCAA load since each of these 

compounds is metabolized to TCAA 

(ATSDR 2004; ATSDR 1997a; ATSDR 

1997b; USEPA 2000e). Due to the 

limitations primarily in the dietary data 

and a clear indication of exposure from 

other sources, EPA applied a relative 

source contribution of 20%. 

MCAA. The MCLG for MCAA uses 

the following calculations: An RfD of 

0.01 mg/kg/day, a 70 kg adult 

consuming 2 L/day of tap water, and a 

relative source contribution of 20%. 

The RfD included in the proposal was 

based on a chronic drinking water study 

in rats conducted by DeAngelo et al. 

(1997). In the assessment presented for 

the proposed rule, the LOAEL from this 

study was identified as 3.5 mg/kg/day 

based on increased absolute and relative 

spleen weight in the absence of 

histopathologic changes. After 

reviewing comments and further 

analysis of the data, EPA concludes that 

it is more appropriate to identify this 

change as a NOAEL. Increased spleen 

weights in the absence of 

histopathological effects are not 

necessarily adverse. In addition, spleen 

weights were decreased, rather than 

increased in the mid- and high-dose 

groups in the DeAngelo et al. (1997) 

study and were accompanied by a 

significant decrease in body weight, 

decreased relative and absolute liver 

weights, decreased absolute kidney 

weight, and an increase in relative testes 

weight. Accordingly, the mid-dose in 

this same study (26.1 mg/kg/day) has 

been categorized as the LOAEL with the 

lower 3.5 mg/kg/day dose as a NOAEL. 

Based on a NOAEL of 3.5 mg/kg/day 

(DeAngelo et al. 1997), the revised RfD 

was calculated as shown below, with a 

composite uncertainty factor of 300. 

EPA used a default uncertainty factor of 

10 to account for extrapolation from an 

animal study, since no data on rat-tohuman differences in toxicokinetics or 

toxicodynamics were identified. A 

default uncertainty factor of 10 was 

used to account for human variability in 

the absence of data on the variability in 

the toxicokinetics of MCAA in humans 

or in human susceptibility to MCAA. 

An additional uncertainty factor of three 

was used to account for database 

insufficiencies. Although there is no 

multi-generation reproduction study, 

the available studies of reproductive 

and developmental processes suggest 

that developmental toxicity is unlikely 

to be the most sensitive endpoint. This 

led to the following calculation of the 

Reference Dose (RfD) and MCLG for 

MCAA: 

RfD (3.5 mg /kg/day)

(300) = = 0.012 mg /kg/day rounded to 0.01 mg /kg/day

Where: 

3.5 mg/kg/day = NOAEL for decreased 

body weight plus decreased liver, 

kidney and spleen weights in rats 

exposed to MCA for 104 weeks in 

drinking water (DeAngelo et al. 

1997). 

300 = composite uncertainty factor 

chosen to account for inter species 

extrapolation, inter-individual 

variability in humans, and 

deficiencies in the database. 

MCLG for MCAA (0.01 mg/kg/day)(70 kg)(0.2)

2 L/day = = 0.07 mg/L

The RSC for MCAA was selected 

using comparable data to that discussed 

for TCAA. MCAA, like TCAA, has been 

found in foods and is taken up by foods 

during cooking (15% in chicken to 62% 

in pinto beans) and cleaning (2.5% for 

lettuce) with water containing 500 ppb 

MCAA (Reimann et al.1996; Raymer et 

al. 2001, 2004). Rinsing of cooked foods 

did not increase the MCAA content of 

foods to the same extent as was 

observed for TCAA (Raymer et al. 2004). 

MCAA was found to be completely 

stable in water boiled for 60 minutes 

and is likely to be found in the diet due 

to the use of chlorinated water in food 

preparation and the use of chlorine as 

a sanitizing agent by the food industry 

(USFDA 1994). As with TCAA, 

inhalation and dermal exposures are 

unlikely to be significant. Dermal 

exposure from bathing and showering 

was estimated to contribute only 0.03% 

of that from oral exposure (Xu et al. 

2002). As with TCAA, due to the 

limitations in dietary data and a clear 

indication of exposure from other 


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sources, EPA applied a relative source 

contribution of 20%. 

c. Summary of major comments. EPA 

received few comments on MCAA and 

TCAA. The majority of comments about 

the MCLGs for TCAA and MCAA were 

general MCLG questions, including RSC 

derivation. Some commenters 

questioned why MCAA, TCAA, and 

chloroform were calculated using an 

RSC of 20%. In particular, some 

commenters compared these 

calculations to that for DBCM in the 

Stage 1 DBPR, which uses 80%. Each of 

the MCLGs set for chloroform, TCAA, 

and MCAA under this rule is calculated 

using the best available science and EPA 

Office of Water’s current approach for 

deriving the RSC. EPA chose an RSC of 

20%, not 80%, because of clear 

indications of exposure from other 

sources; data limitations preclude the 

derivation of a specific RSC. 

The RSC for DBCM was 80% in the 

Stage 1 DBPR. The DBCM MCLG is not 

part of today’s rulemaking. Any possible 

future revision to the DBCM MCLG as 

a result of an RSC change would not 

affect the MCL for TTHM finalized in 

today’s rule. 

In response to comments received on 

the RfD for MCAA, EPA has reviewed 

the critical study regarding the 

appropriateness of an increase in spleen 

weight in the absence of histopathology 

as a LOAEL. EPA has determined that 

the dose associated with this endpoint 

is more appropriately categorized as a 

NOAEL rather than a LOAEL and has 

revised the RfD and MCLG for MCAA. 

B. Consecutive Systems 

Today’s rule includes provisions for 

consecutive systems, which are public 

water systems that receive some or all 

of their finished water from another 

water system (a wholesale system). 

Consecutive systems face particular 

challenges in providing water that meets 

regulatory standards for DBPs and other 

contaminants whose concentration can 

increase in the distribution system. 

Moreover, previous regulation of DBP 

levels in consecutive systems varies 

widely among States. In consideration 

of these factors, EPA is finalizing 

monitoring, compliance schedule, and 

other requirements specifically for 

consecutive systems. These 

requirements are intended to facilitate 

compliance by consecutive systems 

with MCLs for TTHM and HAA5 under 

the Stage 2 DBPR and help to ensure 

that consumers in consecutive systems 

receive equivalent public health 

protection. 

1. Today’s Rule 

As public water systems, consecutive 

systems must provide water that meets 

the MCLs for TTHM and HAA5 under 

the Stage 2 DBPR, use specified 

analytical methods, and carry out 

associated monitoring, reporting, 

recordkeeping, public notification, and 

other requirements. The following 

discusses a series of definitions needed 

for addressing consecutive system 

requirements in today’s rule. Later 

sections of this preamble provide 

further details on how rule requirements 

(e.g., schedule and monitoring) apply to 

consecutive systems. 

A consecutive system is a public 

water system that receives some or all 

of its finished water from one or more 

wholesale systems. 

Finished water is water that has been 

introduced into the distribution system 

of a public water system and is intended 

for distribution and consumption 

without further treatment, except as 

necessary to maintain water quality in 

the distribution system (e.g., booster 

disinfection, addition of corrosion 

control chemicals). 

A wholesale system is a public water 

system that treats source water as 

necessary to produce finished water and 

then delivers finished water to another 

public water system. Delivery may be 

through a direct connection or through 

the distribution system of one or more 

consecutive systems. 

The combined distribution system is 

defined as the interconnected 

distribution system consisting of the 

distribution systems of wholesale 

systems and of the consecutive systems 

that receive finished water from those 

wholesale system(s). 

EPA is allowing States some 

flexibility in defining what systems are 

a part of a combined distribution 

system. This provision determines 

effective dates for requirements in 

today’s rule; see Section IV.E 

(Compliance Schedules) for further 

discussion. EPA has consulted with 

States and deferred to their expertise 

regarding the nature of the connection 

in making combined distribution system 

determinations. In the absence of input 

from the State, EPA will determine that 

combined distribution systems include 

all interconnected systems for the 

purpose of determining compliance 

schedules for implementation of this 

rule. 

2. Background and Analysis 

The practice of public water systems 

buying and selling water to each other 

has been commonplace for many years. 

Reasons include saving money on 

pumping, treatment, equipment, and 

personnel; assuring an adequate supply 

during peak demand periods; acquiring 

emergency supplies; selling surplus 

supplies; and delivering a better product 

to consumers. EPA estimates that there 

are more than 10,000 consecutive 

systems nationally. 

Consecutive systems face particular 

challenges in providing water that meets 

regulatory standards for contaminants 

that can increase in the distribution 

system. Examples of such contaminants 

include coliforms, which can grow if 

favorable conditions exist, and some 

DBPs, including THMs and HAAs, 

which can increase when a disinfectant 

and DBP precursors continue to react in 

the distribution system. 

EPA included requirements 

specifically for consecutive systems 

because States have taken widely 

varying approaches to regulating DBPs 

in consecutive systems in previous 

rules. For example, some States have 

not regulated DBP levels in consecutive 

systems that deliver disinfected water 

but do not add a disinfectant. Other 

States have determined compliance 

with DBP standards based on the 

combined distribution system that 

includes both the wholesaler and 

consecutive systems. In this case, sites 

in consecutive systems are treated as 

monitoring sites within the combined 

distribution system. Neither of these 

approaches provide the same level of 

public health protection as nonconsecutive systems receive under the 

Stage 1 DBPR. Once fully implemented, 

today’s rule will ensure similar 

protection for consumers in consecutive 

systems. 

In developing its recommendations, 

the Stage 2 M-DBP Advisory Committee 

recognized two principles related to 

consecutive systems: (1) consumers in 

consecutive systems should be just as 

well protected as customers of all 

systems, and (2) monitoring provisions 

should be tailored to meet the first 

principle. Accordingly, the Advisory 

Committee recommended that all 

wholesale and consecutive systems 

comply with provisions of the Stage 2 

DBPR on the same schedule required of 

the wholesale or consecutive system 

serving the largest population in the 

combined distribution system. In 

addition, the Advisory Committee 

recommended that EPA solicit 

comments on issues related to 

consecutive systems that the Advisory 

Committee had not fully explored 

(USEPA 2000a). EPA agreed with these 

recommendations and they are reflected 

in today’s rule. 


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3. Summary of Major Comments 

Commenters generally supported the 

proposed definitions. However, 

commenters did express some concerns, 

especially with including a time period 

of water delivery that defined whether 

a system was a consecutive system 

(proposed to trigger plant-based 

monitoring requirements) or wholesale 

system (proposed to allow 

determination that a combined 

distribution system existed). EPA has 

dropped this requirement from the final 

rule; population-based monitoring 

requirements in the final rule do not 

need to define how long a plant must 

operate in order to be considered a 

plant, and EPA has provided some 

flexibility for States to determine which 

systems comprise a combined 

distribution system (without presenting 

a time criterion). 

Other commenters expressed concern 

that the proposed definition of 

consecutive system was inconsistent 

with use of the term prior to the 

rulemaking. EPA acknowledges that the 

Agency has not previously formally 

defined the term, but believes that the 

definition in today’s rule best considers 

all commenters’ concerns, while also 

providing for accountability and public 

health protection in as simple a manner 

as is possible given the many 

consecutive system scenarios that 

currently exist. 

Several States requested flexibility to 

determine which systems comprised a 

combined distribution system under 

this rule; EPA has included that 

flexibility for situations in which 

systems have only a marginal 

association (such as an infrequently 

used emergency connection) with other 

systems in the combined distribution 

system. To prepare for the IDSE and 

subsequent Stage 2 implementation, 

EPA has worked with States in 

identifying all systems that are part of 

each combined distribution system. 

Finally, several commenters requested 

that the wholesale system definition 

replace ‘‘public water system’’ with 

‘‘water system’’ so that wholesale 

systems serving fewer than 25 people 

would not be considered public water 

systems. EPA did not change the 

definition in today’s rule; EPA considers 

any water system to be a public water 

system (PWS) if it serves 25 or more 

people either directly (retail) or 

indirectly (by providing finished water 

to a consecutive system) or through a 

combination of retail and consecutive 

system customers. If a PWS receives 

water from an unregulated entity, that 

PWS must meet all compliance 

requirements (including monitoring and 

treatment techniques) that any other 

public water system that uses source 

water of unknown quality must meet. 

C. LRAA MCLs for TTHM and HAA5 

1. Today’s Rule 

This rule requires the use of 

locational running annual averages 

(LRAAs) to determine compliance with 

the Stage 2 MCLs of 0.080 mg/L TTHM 

and 0.060 mg/L HAA5. All systems, 

including consecutive systems, must 

comply with the MCLs for TTHM and 

HAA5 using sampling sites identified 

under the Initial Distribution System 

Evaluation (IDSE) or using existing 

Stage 1 DBPR compliance monitoring 

locations (as discussed in Section IV.F). 

EPA has dropped the proposed phased 

approach for LRAA implementation 

(Stage 2A and Stage 2B) by removing 

Stage 2A and redesignating Stage 2B as 

Stage 2. 

Details of monitoring requirements 

and compliance schedules are discussed 

in preamble Sections IV.G and IV.E, 

respectively, and may be found in 

subpart V of today’s rule. 

2. Background and Analysis 

The MCLs for TTHM and HAA5 are 

the same as those proposed, 0.080 mg/ 

L TTHM and 0.060 mg/L HAA5 as an 

LRAA. See the proposed rule (68 FR 

49584, August 18, 2003) (USEPA 2003a) 

for a more detailed discussion of the 

analysis supporting the MCLs. The 

primary objective of the LRAA is to 

reduce exposure to high DBP levels. For 

an LRAA, an annual average must be 

computed at each monitoring location. 

The RAA compliance basis of the 1979 

TTHM rule and the Stage 1 DBPR allows 

a system-wide annual average under 

which high DBP concentrations in one 

or more locations are averaged with, and 

dampened by, lower concentrations 

elsewhere in the distribution system. 

Figure IV.C–1 illustrates the difference 

in calculating compliance with the 

MCLs for TTHM between a Stage 1 

DBPR RAA, and the Stage 2 DBPR 

LRAA. 

BILLING CODE 6560–50–P 


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BILLING CODE 6560–50–C 

EPA and the Stage 2 M–DBP Advisory 

Committee considered an array of 

alternative MCL strategies. The 

Advisory Committee discussions 

primarily focused on the relative 

magnitude of exposure reduction versus 

the expected impact on the water 

industry and its customers. Strategies 

considered included across the board 

requirements, such as significantly 

decreasing the MCLs (e.g., 40/30) or 

single hit MCLs (e.g., all samples must 

be below 80/60); and risk targeting 

requirements. In the process of 

evaluating alternatives, EPA and the 

Advisory Committee reviewed vast 

quantities of data and many analyses 

that addressed health effects, DBP 

occurrence, predicted reductions in DBP 

levels, predicted technology changes, 


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and capital, annual, and household 

costs. The Advisory Committee 

recommended and EPA proposed the 

risk targeting approach of 80/60 as an 

LRAA preceded by an IDSE. Today’s 

rule finalizes these requirements. 

EPA has chosen compliance based on 

an LRAA due to concerns about levels 

of DBPs above the MCL in some 

portions of the distribution system. The 

LRAA standard will eliminate systemwide averaging of monitoring results 

from different monitoring locations. The 

individuals served in areas of the 

distribution system with above average 

DBP occurrence levels masked by 

averaging under an RAA are not 

receiving the same level of health 

protection. Although an LRAA standard 

still allows averaging at a single location 

over an annual period, EPA concluded 

that changing the basis of compliance 

from an RAA to an LRAA will result in 

decreased exposure to higher DBP levels 

(see Section VI for predictions of DBP 

reductions under the LRAA MCLs). This 

conclusion is based on three 

considerations: 

(1) There is considerable evidence 

that under the current RAA MCL 

compliance monitoring requirements, a 

small but significant proportion of 

monitoring locations experience high 

DBP levels at least some of the time. Of 

systems that collected data under the 

Information Collection Rule that met the 

Stage 1 DBPR RAA MCLs, 14 percent 

had TTHM single sample concentrations 

greater than the Stage 1 MCL, and 21 

percent had HAA5 single sample 

concentrations above the MCL. 

Although most TTHM and HAA5 

samples were below 100 μg/L, some 

ranged up to 140 μg/L and 130 μg/L, 

respectively. 

(2) In some situations, the populations 

served by certain portions of the 

distribution system consistently receive 

water that exceeds 0.080 mg/L for 

TTHM or 0.060 mg/L for HAA5 (both as 

LRAAs) even though the system is in 

compliance with Stage 1 MCLs). Of 

Information Collection Rule systems 

meeting the Stage 1 DBPR MCLs as 

RAAs, five percent had monitoring 

locations that exceeded 0.080 mg/L 

TTHM and three percent exceeded 

0.060 mg/L HAA5 as an annual average 

(i.e., as LRAAs) by up to 25% 

(calculated as indicated in Figure IV.C–

1). Customers served at these locations 

consistently received water with TTHM 

and/or HAA5 concentrations higher 

than the system-wide average and 

higher than the MCL. 

(3) Compliance based on an LRAA 

will remove the opportunity for systems 

to average out samples from high and 

low quality water sources. Some 

systems are able to comply with an RAA 

MCL even if they have a plant with a 

poor quality water source (that thus 

produces high concentrations of DBPs) 

because they have another plant that has 

a better quality water source (and thus 

lower concentrations of DBPs). 

Individuals served by the plant with the 

poor quality source will usually have 

higher DBP exposure than individuals 

served by the other plant. 

In part, both the TTHM and HAA5 

classes are regulated because they occur 

at high levels and represent chlorination 

byproducts that are produced from 

source waters with a wide range of 

water quality. The combination of 

TTHM and HAA5 represent a wide 

variety of compounds resulting from 

bromine substitution and chlorine 

substitution reactions (e.g., bromoform 

has three bromines, TCAA has three 

chlorines, BDCM has one bromine and 

two chlorines). EPA believes that the 

TTHM and HAA5 classes serve as an 

indicator for unidentified and 

unregulated DBPs. EPA believes that 

controlling the occurrence levels of 

TTHM and HAA5 will help control the 

overall levels of chlorination DBPs. 

3. Summary of Major Comments 

Commenters supported the proposed, 

risk-targeted MCL strategy over the 

alternative MCL strategies that were 

considered by the Advisory Committee 

as the preferred regulatory strategy. 

Commenters concurred with EPA’s 

analysis that such an approach will 

reduce peak and average DBP levels. 

Commenters supported the Stage 2 longterm MCLs of 0.080 mg/L TTHM and 

0.060 mg/L HAA5 as LRAAs. 

EPA received many comments on 

today’s MCLs specific to consecutive 

systems. While commenters supported 

consecutive system compliance with the 

Stage 2 DBPR in order to provide 

comparable levels of public health 

protection, they noted that it would be 

difficult for many consecutive systems 

to meet Stage 2 requirements because 

they have not had to meet the full scope 

of DBP requirements under previous 

rules. EPA has developed a training and 

outreach program to assist these systems 

and encourages States, wholesale 

systems, and professional associations 

to also provide assistance. 

Some commenters expressed concern 

about holding consecutive systems 

responsible for water quality over which 

they have no control. Several 

commenters were concerned about the 

establishment of contracts between 

wholesale and consecutive systems, 

including concern about a strain on 

their relationship, wholesale system 

reluctance to commit to keep DBPs at a 

level suggested by the consecutive 

systems, and the time and money it 

could take to work out differences. 

Although setting up a contract is a 

prudent business action, commenters 

noted that small consecutive water 

systems have few resources to sue for 

damages should the wholesaler provide 

water exceeding the MCL. 

The purpose of DBPRs is to protect 

public health from exposure to high 

DBP levels. Not requiring violations 

when distributed water exceeds MCLs 

undermines the intent of the rule. While 

EPA recognizes consecutive systems do 

not have full control over the water they 

receive, agreements between wholesale 

and consecutive systems may specify 

water quality and actions required of the 

wholesaler if those water quality 

standards are not met. 

Finally, commenters recommended 

that the Stage 2A provisions in the 

proposed rule be removed. These 

provisions (compliance with locational 

running annual average MCLs of 0.120 

mg/L for TTHM and 0.100 mg/L for 

HAA5) required systems to comply with 

the Stage 1 MCLs (as running annual 

averages) and the Stage 2A MCLs (as 

LRAAs) concurrently until systems were 

required to comply with Stage 2B MCLs. 

Commenters noted that having two 

separate MCLs for an individual system 

to comply with at the same time was 

confusing to the system and its 

customers. In addition, State resources 

needed for compliance determinations 

and data management for this short-term 

requirement would be resourceintensive. Finally, resources spent to 

comply with Stage 2A would be better 

spent in complying with Stage 2B, 

especially given that some of the 

changes for Stage 2A compliance might 

not provide any benefit for Stage 2B. 

Since EPA agrees with commenters’

concerns, the Stage 2A requirements 

have been removed from the final rule. 

D. BAT for TTHM and HAA5 

1. Today’s Rule 

Today, EPA is identifying the best 

available technology (BAT) for the 

TTHM and HAA5 LRAA MCLs (0.080 

mg/L and 0.060 mg/L respectively) for 

systems that treat their own source 

water as one of the three following 

technologies: 

(1) GAC10 (granular activated carbon 

filter beds with an empty-bed contact 

time of 10 minutes based on average 

daily flow and a carbon reactivation 

frequency of every 120 days) 

(2) GAC20 (granular activated carbon 

filter beds with an empty-bed contact 

time of 20 minutes based on average 


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Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 413 

daily flow and a carbon reactivation 

frequency of every 240 days) 

(3) Nanofiltration (NF) using a 

membrane with a molecular weight 

cutoff of 1000 Daltons or less. 

EPA is specifying a different BAT for 

consecutive systems than for systems 

that treat their own source water to meet 

the TTHM and HAA5 LRAA MCLs. The 

consecutive system BAT is 

chloramination with management of 

hydraulic flow and storage to minimize 

residence time in the distribution 

system for systems that serve at least 

10,000 people and management of 

hydraulic flow and storage to minimize 

residence time in the distribution 

system for systems that serve fewer than 

10,000 people. 

2. Background and Analysis 

The BATs are the same as was 

proposed, except that consecutive 

systems serving fewer than 10,000 

people do not have chloramination as 

part of the consecutive system BAT. See 

the proposal (68 FR 49588, August 18, 

2003) (USEPA 2003a) for more detail on 

the analysis supporting these 

requirements. The Safe Drinking Water 

Act directs EPA to specify BAT for use 

in achieving compliance with the MCL. 

Systems unable to meet the MCL after 

application of BAT can get a variance 

(see Section IV.K for a discussion of 

variances). Systems are not required to 

use BAT in order to comply with the 

MCL. PWSs may use any State-approved 

technologies as long as they meet all 

drinking water standards. 

EPA examined BAT options first by 

analyzing data from the Information 

Collection Rule treatment studies 

designed to evaluate the ability of GAC 

and NF to remove DBP precursors. 

Based on the treatment study results, 

GAC is effective for controlling DBP 

formation for waters with influent TOC 

concentrations below approximately 6 

mg/L (based on the Information 

Collection Rule and NRWA data, over 

90 percent of plants have average 

influent TOC levels below 6 mg/L 

(USEPA 2003c)). Of the plants that 

conducted an Information Collection 

Rule GAC treatment study, 

approximately 70 percent of the surface 

water plants studied could meet the 

0.080 mg/L TTHM and 0.060 mg/L 

HAA5 MCLs, with a 20 percent safety 

factor (i.e., 0.064 mg/L and 0.048 mg/L, 

respectively) using GAC with 10 

minutes of empty bed contact time and 

a 120 day reactivation frequency, and 78 

percent of the plants could meet the 

MCLs with a 20 percent safety factor 

using GAC with 20 minutes of empty 

bed contact time and a 240 day 

reactivation frequency. Because the 

treatment studies were conducted at 

plants with much poorer water quality 

than the national average, EPA believes 

that much higher percentages of plants 

nationwide could meet the MCLs with 

the proposed GAC BATs. 

Among plants using GAC, larger 

systems would likely realize an 

economic benefit from on-site 

reactivation, which could allow them to 

use smaller, 10-minute empty bed 

contact time contactors with more 

frequent reactivation (i.e., 120 days or 

less). Most small systems would not 

find it economically advantageous to 

install on-site carbon reactivation 

facilities, and thus would opt for larger, 

20-minute empty bed contact time 

contactors, with less frequent carbon 

replacement (i.e., 240 days or less). 

The Information Collection Rule 

treatment study results also 

demonstrated that nanofiltration was 

the better DBP control technology for 

ground water sources with high TOC 

concentrations (i.e., above 

approximately 6 mg/L). The results of 

the membrane treatment studies showed 

that all ground water plants could meet 

the 0.080 mg/L TTHM and 0.060 mg/L 

HAA5 MCLs, with a 20% safety factor 

(i.e., 0.064 mg/L and 0.048 mg/L, 

respectively) at the system average 

distribution system residence time using 

nanofiltration. Nanofiltration would be 

less expensive than GAC for high TOC 

ground waters, which generally require 

minimal pretreatment prior to the 

membrane process. Also, nanofiltration 

is an accepted technology for treatment 

of high TOC ground waters in Florida 

and parts of the Southwest, areas of the 

country with elevated TOC levels in 

ground waters. 

The second method that EPA used to 

examine alternatives for BAT was the 

Surface Water Analytical Tool model 

that was developed to compare 

alternative regulatory strategies as part 

of the Stage 1 and Stage 2 M–DBP 

Advisory Committee deliberations. EPA 

modeled a number of BAT options. In 

the model, GAC10 was defined as 

granular activated carbon with an empty 

bed contact time of 10 minutes and a 

reactivation or replacement interval of 

90 days or longer. GAC20 was defined 

as granular activated carbon with an 

empty bed contact time of 20 minutes 

and a reactivation or replacement 

interval of 90 days or longer. 

The compliance percentages 

forecasted by the SWAT model are 

indicated in Table IV.D–1. EPA 

estimates that more than 97 percent of 

large systems will be able to achieve the 

Stage 2 MCLs with the GAC BAT, 

regardless of post-disinfection choice 

(Seidel Memo, 2001). Because the 

source water quality (e.g., DBP 

precursor levels) in medium and small 

systems is expected to be comparable to 

or better than that for the large system 

(USEPA 2005f), EPA believes it is 

conservative to assume that at least 90 

percent of medium and small systems 

will be able to achieve the Stage 2 MCLs 

if they were to apply one of the 

proposed GAC BATs. EPA assumes that 

small systems may adopt GAC20 in a 

replacement mode (with replacement 

every 240 days) over GAC10 because it 

may not be economically feasible for 

some small systems to install and 

operate an on-site GAC reactivation 

facility. Moreover, some small systems 

may find nanofiltration cheaper than the 

GAC20 in a replacement mode if their 

specific geographic locations cause a 

relatively high cost for routine GAC 

shipment. 

TABLE IV.D–1.—SWAT MODEL PREDICTIONS OF PERCENT OF LARGE PLANTS IN COMPLIANCE WITH TTHM AND HAA5 

STAGE 2 MCLS AFTER APPLICATION OF SPECIFIED TREATMENT TECHNOLOGIES

Technology 

Compliance with 0.080 mg/L TTHM and 0.060 

mg/L HAA5 LRAAs 

Compliance with 0.064 mg/L TTHM and 0.048 

mg/L HAA5 LRAAs (MCLs with 20% Safety factor) 

Residual disinfectant 

All systems 

(percent) 

Residual 

disinfectant All systems 

(percent) Chlorine (percent) 

Chloramine 

(percent) Chlorine (percent) Chloramine 

(percent) 

Enhanced Coagulation (EC) .................... 73.5 76.9 74.8 57.2 65.4 60.4 

EC (no pre-disinfection) ........................... 73.4 88.0 78.4 44.1 62.7 50.5 

EC & GAC10 ............................................ 100 97.1 99.1 100 95.7 98.6 


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TABLE IV.D–1.—SWAT MODEL PREDICTIONS OF PERCENT OF LARGE PLANTS IN COMPLIANCE WITH TTHM AND HAA5 

STAGE 2 MCLS AFTER APPLICATION OF SPECIFIED TREATMENT TECHNOLOGIES—Continued 

Technology 

Compliance with 0.080 mg/L TTHM and 0.060 

mg/L HAA5 LRAAs 

Compliance with 0.064 mg/L TTHM and 0.048 

mg/L HAA5 LRAAs (MCLs with 20% Safety factor) 

Residual disinfectant 

All systems 

(percent) 

Residual 

disinfectant All systems 

(percent) Chlorine (percent) 

Chloramine 

(percent) Chlorine (percent) Chloramine 

(percent) 

EC & GAC20 ............................................ 100 100 100 100 100 100 

EC & All Chloramines .............................. NA 83.9 NA NA 73.6 NA 

Note: Enhanced coagulation/softening is required under the Stage 1 DBPR for conventional plants. 

Source: Seidel (2001). 

The BAT requirements for large 

consecutive systems are the same as 

proposed, but the requirements have 

changed for small consecutive systems. 

EPA believes that the best compliance 

strategy for consecutive systems is to 

collaborate with wholesalers on the 

water quality they need. For consecutive 

systems that are having difficulty 

meeting the MCLs, EPA is specifying a 

BAT of chloramination with 

management of hydraulic flow and 

storage to minimize residence time in 

the distribution system for systems 

serving at least 10,000 and management 

of hydraulic flow and storage to 

minimize residence time in the 

distribution system for systems serving 

fewer than 10,000. EPA believes that 

small consecutive systems can use this 

BAT to comply with the Stage 2 DBPR, 

but if they cannot, then they can apply 

to the State for a variance. 

Chloramination has been used for 

residual disinfection for many years to 

minimize the formation of chlorination 

DBPs, including TTHM and HAA5 

(USEPA 2003d). EPA estimates that over 

50 percent of large subpart H systems 

serving at least 10,000 use 

chloramination for Stage 1. The BAT 

provision to manage hydraulic flow and 

minimize residence time in the 

distribution system is to facilitate the 

maintenance of the chloramine residual 

and minimize the likelihood for 

nitrification. EPA has not included 

chloramination for consecutive systems 

as part of the BAT for systems serving 

fewer than 10,000 due to concerns about 

their ability to properly control the 

process, given that many have no 

treatment capability or expertise and the 

Agency’s concern about such systems 

having operational difficulties such as 

distribution system nitrification. 

EPA believes that the BATs for 

nonconsecutive systems are not 

appropriate for consecutive systems 

because their efficacy in controlling 

DBPs is based on precursor removal. 

Consecutive systems face the unique 

challenge of receiving waters in which 

DBPs are already present if the 

wholesale system has used a residual 

disinfectant, which the BATs for nonconsecutive systems do not effectively 

remove. GAC is not cost-effective for 

removing DBPs. Nanofiltration is only 

moderately effective at removing THMs 

or HAAs if membranes with a very low 

molecular weight cutoff (and very high 

cost of operation are employed). 

Therefore, GAC and nanofiltration are 

not appropriate BATs for consecutive 

systems. 

3. Summary of Major Comments 

Commenters concurred with EPA’s 

identification of BATs for nonconsecutive systems but expressed 

concern about the BAT for consecutive 

systems. Many commenters agreed that 

Stage 2 compliance for consecutive 

systems would usually best be achieved 

by improved treatment by the wholesale 

system. However, they noted that the 

proposed BAT may not be practical for 

compliance if water delivered to the 

consecutive system is at or near DBP 

MCLs. In addition, chloramination 

requires operator supervision and 

adjustment and many consecutive 

systems that buy water may be reluctant 

to operate chemical feed systems. 

Therefore, EPA included chloramines as 

part of the BAT in today’s rule only for 

systems serving at least 10,000 because 

of the operator attention it requires and 

concerns with safety and nitrification. 

While some commenters believed that 

having a BAT for consecutive systems 

contradicts the premise of the Stage 1 

DBPR that DBPs are best controlled 

through TOC removal and optimizing 

disinfection processes, the SDWA 

requires EPA to identify a BAT for all 

systems required to meet an MCL. No 

commenter recommended an alternative 

BAT. EPA still believes that precursor 

removal remains a highly effective 

strategy to reduce DBPs. Thus, EPA 

encourages States to work with 

wholesale systems and consecutive 

systems to identify strategies to ensure 

compliance, especially those systems 

with DBP levels close to the MCL. 

E. Compliance Schedules 

1. Today’s Rule 

This section specifies compliance 

dates for the IDSE and MCL compliance 

requirements in today’s rule. As 

described elsewhere in Section IV of 

this preamble, today’s rule requires 

PWSs to carry out the following 

activities: 

• Conduct initial distribution system 

evaluations (IDSEs) on a required 

schedule. Systems may comply by using 

any of four approaches for which they 

qualify (standard monitoring, system 

specific study, 40/30 certification, or 

very small system waiver). 

• Determine Stage 2 monitoring 

locations based on the IDSE. 

• Comply with Stage 2 MCLs on a 

required schedule. 

Compliance dates for these activities 

vary by PWS size. Table IV.E–1 and 

Figure IV.E–1 specify IDSE and Stage 2 

compliance dates. Consecutive systems 

of any size must comply with the 

requirements of the Stage 2 DBPR on the 

same schedule as required for the largest 

system in the combined distribution 

system. 


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TABLE IV.E–1.—IDSE AND STAGE 2 COMPLIANCE DATES

Requirement 

Compliance dates by PWS size (retail population served) 1

CWSs and 

NTNCWSs serving 

at least 100,000 

CWSs and 

NTNCWSs serving 

50,000–99,999 

CWSs and 

NTNCWSs serving 

10,000–49,999 

CWSs serving 

<10,000 

NTNCWSs serving 

<10,000 

Submit IDSE monitoring plan OR 

Submit IDSE system specific 

study plan OR.

Submit 40/30 certification OR .....

Receive very small system waiver from State.

October 1, 2006 ..... April 1, 2007 ........... October 1, 2007 ..... April 1, 2008 ....... Not applicable. 

Complete standard monitoring or 

system specific study.

September 30, 2008 March 31, 2009 ...... September 30, 2009 March 31, 2010 .. Not applicable. 

Submit IDSE Report ................... January 1, 2009 ..... July 1, 2009 ............ January 1, 2010 ..... July 1, 2010 ....... Not applicable. 

Begin subpart V (Stage 2) compliance monitoring 2.April 1, 2012 ........... October 1, 2012 ..... October 1, 2013 ..... October 1, 2013 

(October 1, 

2014 if Cryptosporidium monitoring is required under 

Subpart W)..

1Wholesale and consecutive systems that are part of a combined distribution system must comply based on the schedule required of the largest system in the combined distribution system. 2States may grant up to an additional 2 years for systems making capital improvements. 

BILLING CODE 6560–50–P 


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BILLING CODE 6560–50–C 


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2. Background and Analysis 

The compliance schedule in today’s 

final rule stems from the risk-targeted 

approach of the rule, wherein PWSs 

conduct initial monitoring to determine 

locations and concentrations of high 

DBPs. A primary objective of this 

schedule is to ensure that PWSs identify 

locations with high DBP concentrations 

and provide appropriate additional 

treatment in a timely manner for high 

risk areas, while not requiring low risk 

systems to add additional treatment. 

The compliance schedule balances the 

objective of early risk-targeted 

monitoring with adequate time for 

PWSs and the State or primacy agency 

to assure full implementation and 

compliance. EPA is establishing 

concurrent compliance schedules under 

the Stage 2 DBPR for all systems (both 

wholesale systems and consecutive 

systems) in a particular combined 

distribution system because this will 

assure comparable risk-based targeting 

information being available at the same 

time for all PWSs that are part of a 

combined distribution system and 

thereby allow for more cost-effective 

compliance with TTHM and HAA5 

MCLs. 

SDWA section 1412(b)(10) states that 

a drinking water regulation shall take 

effect 3 years from the promulgation 

date unless the Administrator 

determines that an earlier date is 

practicable. Today’s rule requires PWSs 

to begin monitoring prior to 3 years 

from the promulgation date. Based on 

EPA’s assessment and recommendations 

of the Advisory Committee, as described 

in this section, EPA has determined that 

these monitoring start dates are 

practicable and appropriate. 

Systems must submit their IDSE plans 

(monitoring plans for standard 

monitoring, study plans for system 

specific studies) to the primacy agency 

for review and approval. The State or 

primacy agency will then have 12 

months to review, and, as necessary, 

consult with the system. A number of 

PWSs will then conduct one year of 

distribution system monitoring for 

TTHM and HAA5 at locations other 

than those currently used for Stage 1 

DBPR compliance monitoring. At the 

conclusion of this monitoring, these 

PWSs have three months to evaluate 

analysis and monitoring results and 

submit Stage 2 compliance monitoring 

locations and schedules to the State or 

primacy agency. Where required, PWSs 

must provide the necessary level of 

treatment to comply with the Stage 2 

MCLs within three years of the 

completion of State or primacy agency 

review of the IDSE report, though States 

may allow an additional two years for 

PWSs making capital improvements. 

EPA has modified the proposed 

compliance schedule to stagger 

monitoring start dates for PWSs serving 

10,000 to 99,999 people and to allow 

more time for development and review 

of IDSE monitoring plans prior to the 

start of monitoring. The following 

discussion addresses these changes from 

the proposal. 

The proposed rule required all PWSs 

serving at least 10,000 people (plus 

smaller systems that are part of a 

combined distribution system with a 

PWS that serves at least 10,000 people) 

to complete IDSE monitoring and 

submit IDSE reports (including 

recommended Stage 2 compliance 

monitoring locations) two years after 

rule promulgation, followed by one year 

for review of IDSE reports, after which 

systems had three years to come into 

compliance with Stage 2B MCLs. 

Under today’s final rule, PWSs 

serving at least 100,000 people (plus 

smaller systems that are part of the 

combined distribution system) will meet 

the same Stage 2 compliance deadlines 

as proposed. However, the timing of the 

IDSE has been changed to allow for a 

more even workload and a greater 

opportunity for primacy agency 

involvement (e.g., through monitoring 

plan review and approval). The IDSE 

plan submission dates for PWSs serving 

50,000 to 99,999 people (plus smaller 

systems that are part of the combined 

distribution system) will be 12 months 

after the effective date; for PWSs serving 

10,000 to 49,999 (plus smaller systems 

that are part of the combined 

distribution system), the IDSE plan 

submission dates will be 18 months 

after the effective date. The Stage 2 

compliance schedule for systems 

serving fewer than 10,000 people 

remains the same as proposed. Stage 2 

MCL compliance dates are modified 

accordingly. 

This staggering of IDSE start dates for 

PWSs serving 10,000 to 99,999 people is 

advantageous in several respects: 

• Provides PWSs greater assurance 

that IDSEs are properly conducted by 

requiring IDSE plan review prior to 

conducting the IDSE. 

• Provides additional time to develop 

budgets and establish contracts with 

laboratories. 

• Spreads out the workload for 

technical assistance and guidance. The 

staggered schedule will allow States and 

EPA to provide more support to 

individual PWSs as needed. 

• Provides time for DBP analytical 

laboratories to build capacity as needed 

to accommodate the sample analysis 

needs of PWSs and extends and 

smooths the demand for laboratory 

services. 

• Maintains simultaneous rule 

compliance with the LT2ESWTR as 

recommended by the Stage 2 M-DBP 

Advisory Committee and as mandated 

by the 1996 SDWA Amendments, which 

require that EPA ‘‘minimize the overall 

risk of adverse health effects by 

balancing the risk from the contaminant 

and the risk from other contaminants 

the concentrations of which may be 

affected by the use of a treatment 

technique or process that would be 

employed to attain the maximum 

contaminant level’’ (Sec. 

1412(b)(5)(B)(i)). 

The Advisory Committee 

recommended the Initial Distribution 

System Evaluation, as discussed in 

Section IV.F, and EPA is finalizing an 

IDSE schedule generally consistent with 

the Advisory Committee timeframe 

recommendation, but modified to 

stagger the schedule for systems serving 

more than 10,000 but less than 100,000, 

and to address public comments on the 

IDSE requirements. 

For all systems, the IDSE schedule has 

been revised to allow systems to submit 

and States or primacy agencies to 

review (and revise, if necessary) 

systems’ recommendations for IDSE and 

Stage 2 monitoring locations, while still 

allowing systems three years after 

completion of the State or primacy 

agency review of Stage 2 compliance 

monitoring locations to make necessary 

treatment and operational changes to 

comply with Stage 2 MCLs. 

Figure IV.E–2 illustrates compliance 

schedules for examples of three 

combined distribution systems, with the 

schedule dictated by the retail 

population served by the largest system. 

FIGURE IV.E–2.—SCHEDULE EXAMPLES. 

—Wholesale system (pop. 64,000) with three consecutive systems (pops. 21,000; 15,000; 5,000): 

—IDSE monitoring plan due for all systems April 1, 2007 since wholesale system serves 50,000–99,999 

—Stage 2 compliance beginning October 1, 2012 for all systems 

—Wholesale system (pop. 4,000) with three consecutive systems (pops. 21,000; 5,000; 5,000): 


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FIGURE IV.E–2.—SCHEDULE EXAMPLES.—Continued 

—IDSE monitoring plan due for all systems October 1, 2007 since the largest system in combined distribution system serves 10,000–

49,999 

—Stage 2 compliance beginning October 1, 2013 for all systems 

—Wholesale system (pop. 4,000) with three consecutive systems (pops. 8,000; 5,000; 5,000): 

—IDSE monitoring plan due for all systems April 1, 2008 since no individual system in combined distribution system exceeds 10,000 (even 

though total population exceeds 10,000) 

—Stage 2 compliance beginning October 1, 2013 if no Cryptosporidium monitoring under the LT2ESWTR is required or beginning October 

1, 2014 if Cryptosporidium monitoring under the LT2ESWTR is required 

This schedule requires wholesale 

systems and consecutive systems that 

are part of a combined distribution 

system with at least one system with an 

earlier compliance deadline to conduct 

their IDSE simultaneously so that the 

wholesale system will be aware of 

compliance challenges facing the 

consecutive systems and will be able to 

implement treatment plant, capital, and 

operational improvements as necessary 

to ensure compliance of both the 

wholesale and consecutive systems. The 

Advisory Committee and EPA both 

recognized that DBPs, once formed, are 

difficult to remove and are generally 

best addressed by treatment plant 

improvements, typically through 

precursor removal or use of alternative 

disinfectants. For a wholesale system to 

make the best decisions concerning the 

treatment steps necessary to meet 

TTHM and HAA5 LRAAs under the 

Stage 2 DBPR, both in its own 

distribution system and in the 

distribution systems of consecutive 

systems it serves, the wholesale system 

must know the DBP levels throughout 

the combined distribution system. 

Without this information, the wholesale 

system may design treatment changes 

that allow the wholesale system to 

achieve compliance, but leave the 

consecutive system out of compliance. 

In summary, the compliance schedule 

for today’s rule maintains the earliest 

compliance dates recommended by the 

Advisory Committee for PWSs serving 

at least 100,000 people (plus smaller 

systems that are part of the combined 

distribution system). These PWSs serve 

the majority of people. The schedule 

also maintains the latest compliance 

dates the Advisory Committee 

recommended, which apply to PWSs 

serving fewer than 10,000 people. EPA 

has staggered compliance schedules for 

PWSs between these two size categories 

in order to facilitate implementation of 

the rule. This staggered schedule is 

consistent with the schedule required 

under the LT2ESWTR promulgated 

elsewhere in today’s Federal Register. 

3. Summary of Major Comments 

EPA received significant public 

comment on the compliance schedule in 

the August 18, 2003 proposal. Major 

issues raised by commenters include 

providing more time for PWSs to 

prepare for monitoring, giving States or 

primacy agencies more time to oversee 

monitoring, and establishing consistent 

schedules for consecutive PWSs. A 

summary of these comments and EPA’s 

responses follows. 

Standard monitoring plan and system 

specific study plan preparation. Many 

commenters were concerned about the 

proposed requirement to develop and 

execute an IDSE monitoring plan 

without any primacy agency review. 

PWSs specifically expressed concern 

about the financial commitment without 

prior State approval and noted that 

some PWSs would need more than the 

time allowed under the proposed rule to 

develop and implement an IDSE 

monitoring plan, especially without an 

opportunity for State or primacy agency 

review and approval. Smaller PWSs 

may require substantial time and 

planning to budget for IDSE expenses, 

especially for systems that have not 

previously complied with DBP MCLs. 

EPA recognizes these concerns and 

today’s final rule provides time for 

PWSs to submit IDSE plans (monitoring 

plans, study plans, or 40/30 

certifications) for State or primacy 

agency review and more time before 

having to begin monitoring. 

Specifically, PWSs serving 50,000 to 

99,999 people and those serving 10,000 

to 49,999 people must submit IDSE 

plans about 12 months and 18 months 

after the effective date, respectively, and 

complete standard monitoring or a 

system specific study within two years 

after submitting their IDSE plan. This is 

significantly more time than was 

specified under the proposal, where 

these systems would have had to 

conduct their IDSE and submit their 

IDSE report 24 months after the effective 

date. PWSs serving at least 100,000 

people must submit IDSE plans about 

six months after the effective date and 

complete standard monitoring or a 

system specific study about 30 months 

after the effective date, which also 

provides more time than was specified 

under the proposal. PWSs serving fewer 

than 10,000 people, not associated with 

a larger system in their combined 

distribution system, do not begin 

monitoring until more than 36 months 

after the effective date. 

EPA believes that the final 

compliance schedule allows PWSs 

sufficient time to develop IDSE plans 

with these compliance dates. The 

schedule also allows 12 months for 

State or primacy agency review of IDSE 

plans, which allows additional time for 

review and for coordination with 

systems and provides more time to 

address deficiencies in IDSE plans. This 

is especially important for smaller 

PWSs, which are likely to need the most 

assistance from States. By staggering 

monitoring start dates, today’s rule also 

eases implementation by reducing the 

number of PWSs that will submit plans 

at any one time, when the most 

assistance from regulatory agencies will 

be required. 

In summary, today’s schedule has 

been modified so that systems are 

required to submit IDSE plans for 

primacy agency review and approval 

prior to conducting their IDSE. Systems 

can consider that their plan has been 

approved if they have not heard back 

from the State by the end of the State 

review period. Systems are also required 

to conduct the approved monitoring and 

submit their IDSE report (including the 

system’s recommended Stage 2 

compliance monitoring) for State or 

primacy agency review on a schedule 

that allows for systems to still have a 

minimum of full three years to comply 

with Stage 2 following State or primacy 

agency review of the system’s Stage 2 

recommended monitoring. As with the 

review of plans, systems can consider 

that their IDSE report has been 

approved if they have not heard back 

from the State by the end of the State 

review period. 

State/primacy agency oversight. EPA 

is preparing to support implementation 

of IDSE requirements that must be 

completed prior to States achieving 

primacy. Several States have expressed 

concern about EPA providing guidance 

and reviewing reports from systems that 

the State has permitted, inspected, and 

worked with for a long time. These 

States believe that their familiarity with 


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the systems enables them to make the 

best decisions to implement the rule 

and protect public health and that the 

rule requirement should be delayed 

until States receive primacy. 

Commenters were concerned that some 

States will not participate in early 

implementation activities and indicated 

that States would prefer monitoring to 

begin 24 months after rule 

promulgation. Commenters also noted 

that States need sufficient time to 

become familiar with the rule, train 

their staff, prepare primacy packages, 

and train PWSs. 

EPA agrees that State familiarity is an 

important component of the review and 

approval process, looks forward to 

working closely with the State drinking 

water program representatives during 

IDSE implementation, and welcomes 

proactive State involvement. However, 

the Agency believes that delaying 

implementation of risk-based IDSE 

targeting activities until States receive 

primacy is an unacceptable delay in 

public health protection and also 

inconsistent with the Advisory 

Committee’s recommendations. EPA 

remains committed to working with 

States to the greatest extent feasible to 

implement today’s rule, consistent with 

the schedule promulgated today. For 

States unable to actively participate in 

IDSE implementation, however, EPA 

believes it has an obligation to provide 

support and guidance to PWSs who are 

covered and independently responsible 

for complying with the IDSE 

requirements of today’s rule and is 

prepared to oversee implementation. 

Moreover, EPA believes that the 

staggered compliance schedule in 

today’s final rule will enhance States’

ability to help implement the rule. 

Consecutive systems. Most 

commenters supported consecutive 

systems being on the same IDSE 

schedule as wholesale systems, 

recognizing the benefits of treatment 

plant capital and operational 

improvements by the wholesale system 

as the preferred method of DBP 

compliance, with the timely collection 

of DBP data throughout the combined 

distribution system a key component. 

Several commenters preferred that 

consecutive systems have a later Stage 

2 compliance date to allow for 

evaluation of whether wholesale system 

treatment changes are adequate to 

ensure compliance and to consider 

changes to water delivery specifications. 

EPA disagrees with those commenters 

recommending a different Stage 2 

compliance date and thus has 

maintained the approach in the 

proposal, which keeps all systems that 

are part of a combined distribution 

system (the interconnected distribution 

system consisting of the distribution 

systems of wholesale systems and of the 

consecutive systems that receive 

finished water) on the same Stage 2 

compliance schedule. Extending the 

Stage 2 compliance dates would 

unnecessarily delay the public health 

protection afforded by this rule. 

Consecutive systems must be able to 

evaluate whether wholesale system 

changes are sufficient to ensure 

compliance and, if they are not, to make 

cost-effective changes to ensure 

compliance where wholesale system 

efforts address some, but not all, of the 

concerns with compliance. Public 

health protection through compliance 

with Stage 2 MCLs will occur on the 

schedule of the largest system for all 

systems in the combined distribution 

system (regardless of size). If a 

consecutive system must make capital 

improvements to comply with this rule, 

the State may use its existing authority 

to grant up to an additional 24 months 

to that system. In addition, 

implementation and data tracking will 

be simplified because all systems in a 

combined distribution system will be on 

the same IDSE and Stage 2 compliance 

schedule. EPA believes that this is a 

better approach from both a public 

health standpoint and an 

implementation standpoint. 

EPA agrees with many commenters 

that a high level of coordination among 

wholesaler, consecutive system, and 

States will be necessary to ensure 

compliance. The schedule in today’s 

rule provides more time for planning, 

reviewing, and conducting the IDSE 

than the schedule in the proposed rule, 

which will allow more time for 

necessary coordination, including small 

consecutive systems that need help in 

negotiations with their wholesale 

system. EPA will work with ASDWA 

and States to develop guidance to 

facilitate wholesale/consecutive system 

cooperation. This additional time and 

the staggered schedule discussed in this 

section also lessens the laboratory 

burden associated with IDSE 

monitoring. 

The staggered schedule also helps 

address commenter concerns about 

evaluating combined distribution 

systems. Other commenters’ concerns 

about time needed for developing 

contracts between systems and for 

planning, funding, and implementing 

treatment changes are addressed by not 

requiring Stage 2 compliance until at 

least six years following rule 

promulgation. 

F. Initial Distribution System Evaluation 

(IDSE) 

1. Today’s Rule 

Today’s rule establishes requirements 

for systems to perform an Initial 

Distribution System Evaluation (IDSE). 

The IDSE is intended to identify sample 

locations for Stage 2 compliance 

monitoring that represent distribution 

system sites with high DBP 

concentrations. Systems will develop an 

IDSE plan, collect data on DBP levels 

throughout their distribution system, 

evaluate these data to determine which 

sampling locations are most 

representative of high DBP levels, and 

compile this information into a report 

for submission to the State or primacy 

agency. Systems must complete one 

IDSE to meet the requirements of 

today’s rule. 

a. Applicability. This requirement 

applies to all community water systems, 

and to large nontransient 

noncommunity water systems (those 

serving at least 10,000 people) that use 

a primary or residual disinfectant other 

than ultraviolet light, or that deliver 

water that has been treated with a 

primary or residual disinfectant other 

than ultraviolet light. Systems serving 

fewer than 500 people are covered by 

the very small system waiver provisions 

of today’s rule and are not required to 

complete an IDSE if they have TTHM 

and HAA5 data collected under Subpart 

L. Consecutive systems are subject to 

the IDSE requirements of today’s rule. 

Consecutive systems must comply with 

IDSE requirements on the same 

schedule as the system serving the 

largest population in the combined 

distribution system, as described in 

section IV.E. 

b. Data collection. For those systems 

not receiving a very small system 

waiver, there are three possible 

approaches by which a system can meet 

the IDSE requirement. 

i. Standard monitoring. Standard 

monitoring requires one year of DBP 

monitoring throughout the distribution 

system on a specified schedule. Prior to 

commencing standard monitoring, 

systems must prepare a monitoring plan 

and submit it to the primacy agency for 

review. The frequency and number of 

samples required under standard 

monitoring is determined by source 

water type and system size. The number 

of samples does not depend on the 

number of plants per system. Section 

IV.G provides a detailed discussion of 

the specific population-based 

monitoring requirements for IDSE 

standard monitoring. Although standard 

monitoring results are not to be used for 

determining compliance with MCLs, 


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systems are required to include 

individual sample results for the IDSE 

results when determining the range of 

TTHM and HAA5 levels to be reported 

in their Consumer Confidence Report 

(see section IV.J). 

ii. System specific study. Under this 

approach, systems may choose to 

perform a system specific study based 

on earlier monitoring studies or 

distribution system hydraulic models in 

lieu of standard monitoring. Prior to 

commencing a system specific study, 

systems must prepare a study plan and 

submit it to the primacy agency for 

approval. The two options for system 

specific studies are: (1) TTHM and 

HAA5 monitoring data that encompass 

a wide range of sample sites 

representative of the entire distribution 

system, including those judged to 

represent high TTHM and HAA5 

concentrations, and (2) extended period 

simulation hydraulic models that 

simulate water age in the distribution 

system, in conjunction with one round 

of TTHM and HAA5 sampling. 

iii. 40/30 certification. Under this 

approach, systems must certify to their 

State or primacy agency that every 

individual compliance sample taken 

under subpart L during the period 

specified in Table IV.F–2 were less than 

or equal to 0.040 mg/L for TTHM and 

less than or equal to 0.030 mg/L for 

HAA5, and that there were no TTHM or 

HAA5 monitoring violations during the 

same period. The State or primacy 

agency may require systems to submit 

compliance monitoring results, 

distribution system schematics, or 

recommend subpart V compliance 

monitoring locations as part of the 

certification. This certification must be 

kept on file and submitted to the State 

or primacy agency for review. Systems 

that qualify for reduced monitoring for 

the Stage 1 DBPR during the two years 

prior to the start of the IDSE may use 

results of reduced Stage 1 DBPR 

monitoring to prepare the 40/30 

certification. The requirements for the 

40/30 certification are listed in Table 

IV.F–1. 

TABLE IV.F–1.—40/30 CERTIFICATION REQUIREMENTS

40/30 Certification Requirements ... • A certification that every individual compliance sample taken under subpart L during the period specified 

in Table IV.F–2 were less than or equal to 0.040 mg/L for TTHM and less than or equal to 0.030 mg/L 

for HAA5, and that there were no TTHM or HAA5 monitoring violations during the same period. 

• Compliance monitoring results, distribution system schematics, and/or recommended subpart V compliance monitoring locations as required by the State or primacy agency. 

TABLE IV.F–2.—40/30 ELIGIBILITY DATES

If your 40/30 Certification Is Due 

Then your eligibility for 40/30 certification is based on eight consecutive 

calendar quarters of subpart L compliance monitoring results beginning 

no earlier than1

(1) October 1, 2006 .................................................................................. January 2004. 

(2) April 1, 2007 ........................................................................................ January 2004. 

(3) October 1, 2007 .................................................................................. January 2005. 

(4) April 1, 2008 ........................................................................................ January 2005. 

1 Unless you are on reduced monitoring under subpart L and were not required to monitor during the specified period. If you did not monitor 

during the specified period, you must base your eligibility on compliance samples taken during the 12 months preceding the specified period. 

c. Implementation. All systems 

subject to the IDSE requirement under 

this final rule (except those covered by 

the very small system waiver) must 

prepare and submit an IDSE plan 

(monitoring plan for standard 

monitoring, study plan for system 

specific study) or 40/30 certification to 

the State or primacy agency. IDSE plans 

and 40/30 certifications must be 

submitted according to the schedule 

described in section IV.E and IV.M. The 

requirements for the IDSE plan depend 

on the IDSE approach that the system 

selects and are listed in Tables IV.F–1 

and IV.F–3. 

TABLE IV.F–3.—IDSE MONITORING PLAN REQUIREMENTS

IDSE data collection alternative IDSE plan requirements 

Standard Monitoring ........................ • Schematic of the distribution system (including distribution system entry points and their sources, and 

storage facilities), with notes indicating locations and dates of all projected standard monitoring, and all 

projected subpart L compliance monitoring. 

• Justification for all standard monitoring locations selected and a summary of data relied on to select 

those locations. 

• Population served and system type (subpart H or ground water). 

System Specific Study: 

Hydraulic Model .............................. Hydraulic models must meet the following criteria: 

• Extended period simulation hydraulic model. 

• Simulate 24 hour variation in demand and show a consistently repeating 24 hour pattern of residence 

time. 

• Represent 75% of pipe volume; 50% of pipe length; all pressure zones; all 12-inch diameter and larger 

pipes; all 8-inch and larger pipes that connect pressure zones, influence zones from different sources, 

storage facilities, major demand areas, pumps, and control valves, or are known or expected to be significant conveyors of water; all pipes 6 inches and larger that connect remote areas of a distribution system to the main portion of the system; all storage facilities with standard operations represented in the 

model; all active pump stations with controls represented in the model; and all active control valves. 


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TABLE IV.F–3.—IDSE MONITORING PLAN REQUIREMENTS—Continued 

IDSE data collection alternative IDSE plan requirements 

• The model must be calibrated, or have calibration plans, for the current configuration of the distribution 

system during the period of high TTHM formation potential. All storage facilities must be evaluated as 

part of the calibration process. 

• All required calibration must be completed no later than 12 months after plan submission. 

Submission must include: 

• Tabular or spreadsheet data demonstrating percent of total pipe volume and pipe length represented in 

the model, broken out by pipe diameter, and all required model elements. 

• A description of all calibration activities undertaken, and if calibration is complete, a graph of predicted 

tank levels versus measured tank levels for the storage facility with the highest residence time in each 

pressure zone, and a time series graph of the residence time at the longest residence time storage facility in the distribution system showing the predictions for the entire simulation period (i.e., from time zero 

until the time it takes for the model to reach a consistently repeating pattern of residence time). 

• Model output showing preliminary 24 hour average residence time predictions throughout the distribution 

system. 

• Timing and number of samples planned for at least one round of TTHM and HAA5 monitoring at a number of locations no less than would be required for the system under standard monitoring in § 141.601 

during the historical month of high TTHM. These samples must be taken at locations other than existing 

subpart L compliance monitoring locations. 

• Description of how all requirements will be completed no later than 12 months after submission of the 

system specific study plan. 

• Schematic of the distribution system (including distribution system entry points and their sources, and 

storage facilities), with notes indicating the locations and dates of all completed system specific study 

monitoring (if calibration is complete) and all subpart L compliance monitoring. 

• Population served and system type (subpart H or ground water). 

• If the model submitted does not fully meet the requirements, the system must correct the deficiencies 

and respond to State inquiries on a schedule the State approves, or conduct standard monitoring. 

System Specific Study: 

Existing Monitoring Results ............ Existing monitoring results must meet the following criteria: 

• TTHM and HAA5 results must be based on samples collected and analyzed in accordance with 

§ 141.131. Samples must be collected within five years of the study plan submission date. 

• The sampling locations and frequency must meet the requirements identified in Table IV.F–4. Each location must be sampled once during the peak historical month for TTHM levels or HAA5 levels or the 

month of warmest water temperature for every 12 months of data submitted for that location. Monitoring 

results must include all subpart L compliance monitoring results plus additional monitoring results as 

necessary to meet minimum sample requirements. 

Submission must include: 

• Previously collected monitoring results 

• Certification that the reported monitoring results include all compliance and non-compliance results generated during the time period beginning with the first reported result and ending with the most recent 

subpart L results. 

• Certification that the samples were representative of the entire distribution system and that treatment 

and distribution system have not changed significantly since the samples were collected. 

• Schematic of the distribution system (including distribution system entry points and their sources, and 

storage facilities), with notes indicating the locations and dates of all completed or planned system specific study monitoring. 

• Population served and system type (subpart H or ground water). 

• If a system submits previously collected data that fully meet the number of samples required for IDSE 

monitoring in Table IV.F–4 and some of the data are rejected due to not meeting the additional requirements, the system must either conduct additional monitoring to replace rejected data on a schedule the 

State approves, or conduct standard monitoring. 

TABLE IV.F–4.—SSS EXISTING MONITORING DATA SAMPLE REQUIREMENTS. 

System type Population size category 

Number of 

monitoring locations 

Number of samples 

TTHM HAA5 

Subpart H: 

<500 3 3 3 

500–3,300 3 9 9 

3,301–9,999 6 36 36 

10,000–49,999 12 72 72 

50,000–249,999 24 144 144 

250,000–999,999 36 216 216 


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TABLE IV.F–4.—SSS EXISTING MONITORING DATA SAMPLE REQUIREMENTS.—Continued 

System type Population size category 

Number of 

monitoring locations 

Number of samples 

TTHM HAA5 

1,000,000–4,999,999 48 288 288 

≥ 5,000,000 60 360 360 

Ground Water: <500 3 3 3 

500–9,999 3 9 9 

10,000–99,999 12 48 48 

100,000–499,999 18 72 72 

≥ 500,000 24 96 96 

The State or primacy agency will 

approve the IDSE plan or 40/30 

certification, or request modifications. If 

the State or primacy agency has not 

taken action by the date specified in 

section IV.E or has not notified the 

system that review is not yet complete, 

systems may consider their submissions 

to be approved. Systems must 

implement the IDSE option described in 

the IDSE plan approved by the State or 

primacy agency according to the 

schedule described in section IV.E. 

All systems completing standard 

monitoring or a system specific study 

must submit a report to the State or 

primacy agency according to the 

schedule described in section IV.E. 

Systems that have completed their 

system specific study at the time of 

monitoring plan submission may submit 

a combined monitoring plan and report 

on the required schedule for IDSE plan 

submissions. The requirements for the 

IDSE report are listed in Table IV.F–5. 

Some of these reporting requirements 

have changed from the proposal to 

reduce reporting and paperwork burden 

on systems. 

TABLE IV.F–5.—IDSE REPORT REQUIREMENTS

IDSE data collection alternative IDSE report requirements 

Standard Monitoring ........................ • All subpart L compliance monitoring and standard monitoring TTHM and HAA5 analytical results in a 

tabular format acceptable to the State. 

• If changed from the monitoring plan, a schematic of the distribution system, population served, and system type. 

• An explanation of any deviations from the approved monitoring plan. 

• Recommendations and justifications for subpart V compliance monitoring locations and timing. 

System Specific Study .................... • All subpart L compliance monitoring and all system specific study monitoring TTHM and HAA5 analytical 

results conducted during the period of the system specific study in a tabular or spreadsheet form acceptable to the State. 

• If changed from the study plan, a schematic of the distribution system, population served, and system 

type. 

• If using the modeling provision, include final information for required plan submissions and a 24-hour 

time series graph of residence time for each subpart V compliance monitoring location selected. 

• An explanation of any deviations from the original study plan. 

• All analytical and modeling results used to select subpart V compliance monitoring locations that show 

that the system specific study characterized TTHM and HAA5 levels throughout the entire distribution 

system. 

• Recommendations and justifications for subpart V compliance monitoring locations and timing. 

All systems must prepare Stage 2 

compliance monitoring 

recommendations. All IDSE reports 

must include recommendations for 

Stage 2 compliance monitoring 

locations and sampling schedule. 

Systems submitting a 40/30 certification 

must include their Stage 2 compliance 

monitoring recommendations in their 

Stage 2 (Subpart V) monitoring plan 

unless the State requests Subpart V site 

recommendations as part of the 40/30 

certification. The number of sampling 

locations and the criteria for their 

selection are described in § 141.605 of 

today’s final rule, and in section IV.G. 

Generally, a system must recommend 

locations with the highest LRAAs unless 

it provides a rationale (such as ensuring 

geographical coverage of the 

distribution system instead of clustering 

all sites in a particular section of the 

distribution system) for selecting other 

locations. In evaluating possible Stage 2 

compliance monitoring locations, 

systems must consider both Stage 1 

DBPR compliance data and IDSE data. 

The State or primacy agency will 

approve the IDSE report or request 

modifications. If the State or primacy 

agency has not taken action by the date 

specified in section IV.E or has not 

notified the system that review is not 

yet complete, systems may consider 

their submission to be approved and 

prepare to begin Stage 2 compliance 

monitoring. 

EPA has developed the Initial 

Distribution System Evaluation 

Guidance Manual for the Final Stage 2 

Disinfectants and Disinfection 

Byproducts Rule (USEPA 2006) to assist 

systems with implementing each of 

these requirements. This guidance may 

be requested from EPA’s Safe Drinking 


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Water Hotline, which may be contacted 

as described under FOR FURTHER

INFORMATION CONTACT in the beginning 

of this notice. This guidance manual is 

also available on the EPA Web site at 

http://www.epa.gov/safewater/stage2/ 

index.html. 

2. Background and Analysis 

In the Stage 2 DBPR proposal 

(USEPA, 2003a), EPA proposed 

requirements for systems to complete an 

IDSE. The Agency based its proposal 

upon the Stage 2 M–DBP Advisory 

Committee recommendations in the 

Agreement in Principle. The Advisory 

Committee believed and EPA concurs 

that maintaining Stage 1 DBPR 

monitoring sites for the Stage 2 DBPR 

would not accomplish the risk-targeting 

objective of minimizing high DBP levels 

and providing consistent and equitable 

protection across the distribution 

system. Most of these requirements have 

not changed from the proposed rule. 

The data collection requirements of 

the IDSE are designed to find both high 

TTHM and high HAA5 sites (see section 

IV.G for IDSE monitoring requirements). 

High TTHM and HAA5 concentrations 

often occur at different locations in the 

distribution system. The Stage 1 DBPR 

monitoring sites identified as the 

maximum location are selected 

according to residence time. HAAs can 

degrade in the distribution system in the 

absence of sufficient disinfectant 

residual (Baribeau et al. 2000). 

Consequently, residence time is not an 

ideal criterion for identifying high 

HAA5 sites. In addition, maximum 

residence time locations that are 

associated with high TTHM levels may 

not be constant due to daily or seasonal 

changes in demand. The analysis of 

maximum residence time completed for 

the selection of Stage 1 monitoring sites 

may not have been capable of detecting 

these variations. The Information 

Collection Rule data show that over 60 

percent of the highest HAA5 LRAAs and 

50 percent of the highest TTHM LRAAs 

were found at sampling locations in the 

distribution system other than the 

maximum residence time compliance 

monitoring location (USEPA 2003a). 

Therefore, the method and assumptions 

used to select the Information Collection 

Rule monitoring sites and the Stage 1 

DBPR compliance monitoring sites may 

not reliably capture high DBP levels for 

Stage 2 DBPR compliance monitoring 

sites. 

a. Standard monitoring. The Advisory 

Committee recommended that systems 

sample throughout the distribution 

system at twice the number of locations 

as required under Stage 1 and, using 

these results in addition to Stage 1 

compliance data, identify high DBP 

locations. Monitoring at additional sites 

increases the chance of finding sites 

with high DBP levels and targets both 

DBPs that degrade and DBPs that form 

as residence time increases in the 

distribution system. EPA believes that 

the required number of standard 

monitoring locations plus Stage 1 

monitoring results will provide an 

adequate characterization of DBP levels 

throughout the distribution system at a 

reasonable cost. By revising Stage 2 

compliance monitoring plans to target 

locations with high DBPs, systems will 

be required to take steps to address high 

DBP levels at locations that might 

otherwise have gone undetected. 

The Advisory Committee 

recommended that an IDSE be 

performed by all community water 

systems, unless the system had 

sufficiently low DBP levels or is a very 

small system with a simple distribution 

system. EPA believes that large 

nontransient noncommunity water 

systems (NTNCWS) (those serving at 

least 10,000 people) also have 

distribution systems that require further 

evaluation to determine the locations 

most representative of high DBP levels 

and proposed that they be required to 

conduct an IDSE. Therefore, large 

NTNCWS and all community water 

systems are required to comply with 

IDSE requirements under today’s final 

rule, unless they submit a 40/30 

certification or they are covered by the 

very small system waiver provisions. 

b. Very small system waivers. Systems 

serving fewer than 500 people that have 

taken samples under the Stage 1 DBPR 

will receive a very small system waiver. 

EPA proposed and the Advisory 

Committee recommended a very small 

system waiver following a State 

determination that the existing Stage 1 

compliance monitoring location 

adequately characterizes both high 

TTHM and high HAA5 for the 

distribution system because many very 

small systems have small or simple 

distribution systems. The final rule 

grants the very small system waiver to 

all systems serving fewer than 500 that 

have Stage 1 DBPR data. This provision 

was changed from the proposal to reflect 

that most very small systems that 

sample under the Stage 1 DBPR have 

sampling locations that are 

representative of both high TTHM and 

high HAA5 because most very small 

systems have small and simple 

distribution systems. In addition, many 

very small systems are ground water 

systems that typically have stable DBP 

levels that tend to be lower than surface 

water DBP levels. NRWA survey data 

show that free chlorine residual in very 

small systems (serving <500) at both 

average residence time and maximum 

residence time locations are lower than 

levels at both of those locations in larger 

systems, and the change in residual 

concentration between those two 

locations is smaller in very small 

systems compared to larger sized 

systems. The magnitude of the 

reduction in residual concentration 

gives an indication of how much 

disinfectant has reacted to form DBPs, 

including TTHM and HAA5. The 

smaller reduction in disinfectant 

concentration between average 

residence time and maximum residence 

time in very small systems compared to 

larger systems indicates that DBP 

formation potential is probably lower in 

very small systems compared to larger 

systems, and the likelihood for 

significant DBP variation within the 

distribution system of very small 

systems is low if the distribution system 

is small and not complex. However, 

there may be some small systems with 

extended or complex distribution 

systems that should be studied further 

to determine new sampling locations. 

For this reason, States or primacy 

agencies can require any particular very 

small system to conduct an IDSE. Very 

small systems subject to the Stage 2 

DBPR that do not have a Stage 1 

compliance monitoring location may 

monitor in accordance with the Stage 1 

DBPR provisions to be eligible for this 

waiver. 

c. 40/30 certifications. Systems that 

certify to their State or primacy agency 

that all compliance samples taken 

during eight consecutive calendar 

quarters prior to the start of the IDSE 

were ≤0.040 mg/L TTHM and ≤0.030 

mg/L HAA5 are not required to collect 

additional DBP monitoring data under 

the IDSE requirements as long as the 

system has no TTHM or HAA5 

monitoring violations. These criteria 

were developed because both EPA and 

the AdvisoryCommittee determined that 

these systems most likely would not 

have DBP levels that exceed the MCLs. 

Systems must have qualifying TTHM 

and HAA5 data for eight consecutive 

calendar quarters according to the 

schedule in Table IV.F–2 to be eligible 

for this option. Systems on reduced 

monitoring that did not monitor during 

the specified time period may use data 

from the prior year to meet the 40/30 

certification criteria. Systems that have 

not previously conducted Stage 1 DBPR 

compliance monitoring may begin such 

monitoring to collect the data necessary 

to qualify for 40/30 certification. The 

certification and data supporting it must 

be available to the public upon request. 


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The qualifying time period for the 40/ 

30 certification has changed from the 

proposed rule. 

Under the proposed rule, the rule 

language identified a specific two year 

window with start and end dates. In 

today’s final rule, the qualifying time 

period has been changed to ‘‘eight 

consecutive calendar quarters of subpart 

L compliance monitoring results 

beginning no earlier than * * *’’ (see 

Table IV.F–2). This change was made so 

that systems that have made a treatment 

change within the two years prior to 

rule promulgation and have collected 

initial data that meet the 40/30 criteria 

might have the opportunity to collect 

eight consecutive quarters of qualifying 

data and apply for a 40/30 certification. 

This schedule change also allows 

systems that have not previously 

monitored under Stage 1 an opportunity 

to qualify for a 40/30 certification. 

Under the proposed Stage 2 DBPR, 

systems that missed the deadline for 

submitting a 40/30 certification would 

be required to conduct either standard 

monitoring or a system specific study 

even if the system otherwise qualified 

for the 40/30 certification. Under 

today’s final rule, systems that do not 

make any submission by the IDSE plan 

submission deadline will still receive a 

violation, but may submit a late 40/30 

certification if their data meet the 

requirements. This change was made so 

that systems and primacy agencies do 

not spend time preparing and reviewing 

standard monitoring plans and IDSE 

reports for systems with a low 

likelihood of finding high TTHM and 

HAA5 levels. 

The reporting requirements for this 

provision have been reduced from the 

requirements in the proposed 

rulemaking. In the proposal, systems 

qualifying for the 40/30 certification 

were required to submit all qualifying 

data and provide recommendations for 

Stage 2 compliance monitoring 

locations. The final rule requires 

systems to submit a certification that 

their data meet all the requirements of 

the 40/30 certification and to include 

their Stage 2 compliance monitoring 

recommendations in their Stage 2 

monitoring plan. These changes were 

made to reduce the reporting burden on 

systems that qualify for the 40/30 

certification and to maintain 

consistency with monitoring plan 

requirements under the Stage 1 DBPR. 

This approach also gives systems more 

time to select appropriate monitoring 

sites for Stage 2 compliance monitoring. 

The State or primacy agency may 

request systems to submit the data, a 

distribution system schematic, and/or 

recommendations for Stage 2 

compliance monitoring as part of the 

40/30 certification. This provision was 

included to facilitate primacy agency 

review of 40/30 certifications; the 

additional information is only required 

if requested by the primacy agency. 

d. System specific studies. Advisory 

Committee members recognized that 

some systems have detailed knowledge 

of their distribution systems by way of 

ongoing hydraulic modeling and/or 

existing widespread monitoring plans 

(beyond that required for compliance 

monitoring) that would provide 

equivalent or superior monitoring site 

selection information compared to 

standard monitoring. Therefore, the 

Advisory Committee recommended that 

such systems be allowed to determine 

new monitoring sites using systemspecific data such as hydraulic model 

results or existing monitoring data; this 

provision remains in the final rule. In 

the proposed rule, the only specification 

for SSSs was to identify monitoring sites 

that would be equivalent or superior to 

those identified under Standard 

Monitoring. The final rule includes 

more specific requirements on how 

these studies should be completed. The 

requirements in the final rule were 

developed to be consistent with the 

proposal, yet more specific to help 

systems better understand expectations 

under this provision and lessen the 

chances of a study plan not being 

approved. 

The new modeling requirements were 

developed to reflect that hydraulic 

models can identify representative high 

TTHM monitoring locations by 

predicting hydraulic residence time in 

the distribution system. Water age has 

been found to correlate with TTHM 

formation in the distribution system. 

Consequently, for this system specific 

study approach, hydraulic residence 

time predicted by the model is used as 

a surrogate for TTHM formation to 

locate appropriate Stage 2 compliance 

monitoring locations. To predict 

hydraulic residence time in the 

distribution system, the model must 

represent most of the distribution 

system and must have been calibrated 

recently and appropriately to reflect 

water age in the distribution system. 

Requirements to reflect this are in 

today’s rule. All storage facilities must 

be evaluated for the calibration, and 

systems using this option must submit 

a graph of predicted tank levels versus 

measured tank levels for the storage 

facility with the highest residence time 

in each pressure zone. These calibration 

requirements are focused on storage 

facilities because they are the largest 

controlling factor for water age in the 

distribution system. The calibration 

requirements reflect the fact that the 

purpose of the model is to predict water 

age. ICR data show that HAA5 data do 

not necessarily correlate well with water 

age (USEPA 2003a). Because the 

purpose of the IDSE is to locate 

representative high locations for both 

TTHM and HAA5, one round of 

monitoring must be completed at 

potential Stage 2 compliance monitoring 

locations to determine appropriate 

HAA5 monitoring locations during the 

historical high month of TTHM 

concentrations. The number of locations 

must be no less than would be required 

under standard monitoring. 

Preliminary average residence time 

data are required as a part of the study 

plan for systems to demonstrate that 

their distribution system hydraulic 

model is able to produce results for 

water age throughout the distribution 

system, even though calibration may not 

be complete. Systems also need to 

describe their plans to complete the 

modeling requirements within 12 

months of submitting the study plan. 

These last two requirements were 

developed so that States can be assured 

that systems have the technical capacity 

to complete their modeling 

requirements by the IDSE report 

deadline. If systems cannot demonstrate 

that they are in a position to complete 

the modeling requirements according to 

the required schedule, they will be 

required to complete standard 

monitoring. 

All new modeling requirements were 

added to help systems demonstrate how 

their model will fulfill the purpose and 

requirements of the IDSE and to assist 

primacy agencies with approval 

determinations. The associated 

reporting requirements were developed 

to balance the needs of systems to 

demonstrate that they have fulfilled the 

requirements and the needs of primacy 

agency reviewers to be able to 

understand the work completed by the 

system. 

EPA has specified new requirements 

for systems complete an SSS using 

existing monitoring data to help systems 

understand the extent of historical data 

that would meet the requirements of the 

IDSE. The number of required sample 

locations and samples are consistent 

with sampling requirements under 

standard monitoring and the 

recommendations made by the Advisory 

Committee. The Advisory Committee 

recommended that systems complete an 

IDSE sample at twice the number of 

sites required by the Stage 1 DBPR in 

addition to Stage 1 DBPR sampling. 

Because the number of required Stage 1 

DBPR monitoring locations varies 

within each population category under 


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the Stage 1 plant-based monitoring 

approach (since systems have different 

numbers of plants), EPA used the 

number of required Standard 

Monitoring locations plus the number of 

Stage 2 compliance monitoring 

locations to develop minimum 

requirements for the use of existing 

monitoring data for the SSS. The 

number of required locations and 

samples are shown in Table IV.F–4. 

Systems will use their Stage 1 

monitoring results plus additional noncompliance or operational samples to 

fulfill these requirements. Small 

systems with many plants may have 

been collecting a disproportionate 

number of samples under the Stage 1 

DBPR compared to the population based 

monitoring requirements presented in 

today’s rule and may have sufficient 

historical data to characterize the entire 

distribution system. These requirements 

allow those systems to submit an SSS 

based on existing Stage 1 monitoring 

results, and they also accommodate 

systems that have been completing 

additional monitoring throughout the 

distribution system. 

The requirement to sample during the 

historical month of high TTHM, high 

HAA5, or warmest water temperature 

during each year for which data were 

collected was added to maintain 

consistency with the standard 

monitoring requirements where each 

location must be sampled one time 

during the peak historical month. 

Samples that qualify for this SSS must 

have been collected within five years of 

the study plan submission date and 

must reflect the current configuration of 

treatment and the distribution system. 

Five years was selected as a cut off for 

eligible data so that all data submitted 

would be reasonably representative of 

current source water conditions and 

DBP formation within the distribution 

system. Data that are older may not 

reflect current DBP formation potential 

in the distribution system. Five years 

prior to the submission of the study 

plan also correlates with the signing of 

the Agreement in Principle where the 

Advisory Committee made the 

recommendation for this provision. 

Systems interested in using this 

provision would have started eligible 

monitoring after the agreement was 

signed. 

Systems that submit existing 

monitoring data must submit all Stage 1 

sample results from the beginning of the 

SSS to the time when the SSS plan is 

submitted. The purpose of this 

requirement is to demonstrate that there 

have been no significant changes in 

source water quality since the first 

samples were collected, especially if all 

existing monitoring results were taken 

during the earliest eligible dates. Again, 

these clarifications were made so that 

systems could better understand the 

extent of data necessary for a monitoring 

plan to be deemed acceptable and be 

confident that efforts to complete an 

SSS would be found acceptable to the 

State or primacy agency. 

e. Distribution System Schematics. 

EPA has considered security concerns 

that may result from the requirement for 

systems to submit a distribution system 

schematic as part of their IDSE plan. 

EPA believes that the final rule strikes 

an appropriate balance between security 

concerns and the need for States and 

primacy agencies to be able to review 

IDSE plans. EPA has developed 

guidance for systems on how to submit 

a distribution system schematic that 

does not include sensitive information. 

3. Summary of Major Comments 

The Agency received significant 

comments on the following issues 

related to the proposed IDSE 

requirements: Waiver limitations, and 

State or primacy agency review of IDSE 

plans. 

In the proposed rule, EPA requested 

comment on what the appropriate 

criteria should be for States or primacy 

agencies to grant very small system 

waivers. Commenters responded with a 

wide range of suggestions including 

support for the proposal as written, 

different population cut-offs, State or 

primacy agency discretion on what 

system size should qualify for the 

waiver, and alternative waiver criteria 

such as pipe length or number of 

booster stations. There was no 

consensus among the commenters on 

what changes should be made to the 

proposal for the very small system 

waiver requirements. EPA did not 

change the population cutoff for the 

very small system waiver because 

analysis of NRWA survey data also 

showed that systems serving fewer than 

500 had different residence times and 

lower free chlorine residual 

concentrations compared to other 

population categories, indicating that 

larger systems have different DBP 

formation characteristics compared to 

very small systems. Some of the 

suggested changes for very small system 

waiver criteria may require data that are 

not readily available to systems (such as 

pipe length in service) and for which 

there were no specific criteria proposed 

or recommended by the commenters. 

Implementation of subjective very small 

system waiver criteria would result in 

reduced public health protection from 

the rule by allowing higher DBP levels 

to go undetected. 

In addition to addressing the very 

small system waivers, commenters 

suggested that different criteria should 

be used for the 40/30 certification, such 

as higher minimum DBP levels, cut-offs 

of 40/30 as LRAAs or RAAs rather than 

single sample maximums, or State or 

primacy agency discretion on which 

systems should qualify for 40/30 

certification. There was no consensus 

among the commenters on what changes 

should be made to the proposal for the 

40/30 certification requirements. EPA 

did not change the requirements for the 

40/30 certification eligibility because 

the recommended alternatives were not 

technically superior to the requirements 

of the proposed rule. Implementation of 

40/30 criteria using an LRAA or RAA 

would result in reduced public health 

protection from the rule by allowing 

higher DBP levels to go undetected. EPA 

did change the eligibility dates and 

reporting requirements for the 40/30 

certification to reduce the burden on the 

system. Under today’s final rule, States 

or primacy agencies can request TTHM 

and HAA5 data as desired for a more indepth review of a system’s 

qualifications. 

Many commenters expressed concern 

over the implementation schedule for 

the IDSE. Commenters were especially 

concerned that IDSE plans would be 

developed and implemented prior to 

State primacy, and once States receive 

primacy, they might not support the 

IDSE plan and would reject the results 

of the completed IDSE. To address this 

issue, commenters requested the 

opportunity for States to review the 

IDSE plans prior to systems completing 

their IDSEs. In today’s rule EPA has 

modified the compliance schedule for 

the Stage 2 DBPR so that systems have 

the opportunity to complete their IDSE 

plan and have it reviewed by the 

primacy agency prior to completing the 

IDSE to address the concern that States 

or primacy agencies may reject the 

results of the completed IDSE. The 

changes to the compliance schedule are 

discussed further in section IV.E. 

G. Monitoring Requirements and 

Compliance Determination for TTHM 

and HAA5 MCLs 

EPA is finalizing monitoring 

requirements under a population-based 

approach described in this section. EPA 

believes the population-based approach 

will provide more representative high 

DBP concentrations throughout 

distribution systems than would plantbased monitoring, is equitable, and will 

simplify implementation for both States 

and systems. For these reasons, EPA 

believes this approach is more 

appropriate than the proposed plantVerDate Aug<31>2005 20:53 Jan 03, 2006 Jkt 208001 PO 00000 Frm 00039 Fmt 4701 Sfmt 4700 E:\FR\FM\04JAR2.SGM 04JAR2

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based monitoring. Detailed discussion 

of the two approaches is presented in 

the preamble of the proposed rule 

(USEPA 2003a) and EA for today’s rule 

(USEPA 2005a). 

1. Today’s Rule 

Today’s rule establishes TTHM and 

HAA5 monitoring requirements for all 

systems based on a population-based 

monitoring approach instead of a plantbased approach. Under the populationbased approach, monitoring 

requirements are based solely on the 

retail population served and the type of 

source water used and not influenced by 

the number of treatment plants or entry 

points in the distribution system as in 

previous rules (i.e., TTHM Rule (USEPA 

1979) and Stage 1 DBPR (USEPA 

1998a)). 

a. IDSE Monitoring. All systems 

conducting IDSE standard monitoring 

must collect samples during the peak 

historical month for DBP levels or water 

temperature; this will determine their 

monitoring schedule. Table IV.G–1 

contains the IDSE monitoring 

frequencies and locations for all source 

water and size category systems. Section 

IV.F identifies other approaches by 

which systems can meet IDSE 

requirements. 

TABLE IV.G–1.—IDSE MONITORING FREQUENCIES AND LOCATIONS

Source water 

type Population size category Monitoring periods and frequency of sampling 

Distribution system monitoring locations 1

Total per 

monitoring 

period 

Near entry 

points 

Average 

residence 

time 

High TTHM 

locations 

High HAA5 

locations 

Subpart H 

<500 consecutive systems.one (during peak historical month) 2.2 1 .................... 1 

<500 non-consecutive 

systems.

.......................................... 2 .................... .................... 1 1 

500–3,300 non-consecutive systems.four (every 90 days) ........ 2 1 .................... 1 ....................

500–3,300 consecutive 

systems.

.......................................... 2 .................... .................... 1 1 

3,301–9,999 ..................... .......................................... 4 .................... 1 2 1 

10,000–49,999 ................. six (every 60 days) .......... 8 1 2 3 2 

50,000–249,999 ............... .......................................... 16 3 4 5 4 

250,000–999,999 ............. .......................................... 24 4 6 8 6 

1,000,000–4,999,999 ....... .......................................... 32 6 8 10 8 

≥5,000,000 ....................... .......................................... 40 8 10 12 10 

Ground 

Water 

<500 consecutive systems.one (during peak historical month) 2.2 1 .................... 1 ....................

<500 non-consecutive 

systems.

.......................................... 2 .................... .................... 1 1 

500–9,999 ........................ four (every 90 days) ........ 2 .................... .................... 1 1 

10,000–99,999 ................. .......................................... 6 1 1 2 2 

100,000–499,999 ............. .......................................... 8 1 1 3 3 

≥500,000 .......................... .......................................... 12 2 2 4 4 

1A dual sample set (i.e., a TTHM and an HAA5 sample) must be taken at each monitoring location during each monitoring period. 

2The peak historical month is the month with the highest TTHM or HAA5 levels or the warmest water temperature. 

b. Routine Stage 2 Compliance 

Monitoring. For all systems conducting 

either standard monitoring or a system 

specific study, initial Stage 2 

compliance monitoring locations are 

based on the system’s IDSE results, 

together with an analysis of a system’s 

Stage 1 DBPR compliance monitoring 

results. Systems receiving 40/30 

certification or a very small system 

waiver, and nontransient 

noncommunity water systems serving 

<10,000 not required to conduct an 

IDSE, base Stage 2 initial compliance 

monitoring locations on the system’s 

Stage 1 DBPR compliance monitoring 

results. Some of these systems may also 

need an evaluation of distribution 

system characteristics to identify 

additional monitoring locations, if 

required by the transition from plantbased monitoring to population-based 

monitoring. 

Systems recommend Stage 2 

monitoring locations generally by 

arraying results of IDSE standard 

monitoring (or system specific study 

results) and Stage 1 compliance 

monitoring by monitoring location (from 

highest to lowest LRAA for both TTHM 

and HAA5). Using the protocol in 

§ 141.605(c) of today’s rule, systems 

then select the required number of 

locations. Larger systems include 

existing Stage 1 monitoring locations in 

order to be able to have historical 

continuity for evaluating how changes 

in operations or treatment affect DBP 

levels. Systems may also recommend 

locations with lower levels of DBPs that 

would not be picked up by the protocol 

if they provide a rationale for the 

recommendation. Examples of 

rationales include ensuring better 

distribution system or population 

coverage (not having all locations in the 

same area) or maintaining existing 

locations with DBP levels that are nearly 

as high as those that would otherwise be 

selected. The State or primacy agency 

will review these recommendations as 

part of the review of the IDSE report 

submitted by systems that conducted 

standard monitoring or a system specific 

study. 

Table IV.G–2 contains the routine 

Stage 2 TTHM and HAA5 compliance 


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monitoring requirements for all systems 

(both non-consecutive and consecutive 

systems), as well as the protocol for 

Stage 2 compliance monitoring location 

selection in the IDSE report. Systems 

that do not have to submit an IDSE 

report (those receiving a 40/30 

certification or very small system waiver 

and nontransient noncommunity water 

systems serving <10,000) must conduct 

Stage 2 compliance monitoring as 

indicated in the ‘‘Total per monitoring 

period’’ column at current Stage 1 

compliance monitoring locations, unless 

the State or primacy agency specifically 

directs otherwise. All systems are then 

required to maintain and follow a Stage 

2 compliance monitoring plan. 

TABLE IV.G–2. ROUTINE COMPLIANCE MONITORING FREQUENCIES AND LOCATIONS

Source water type Population size category Monitoring frequency1

Distribution system monitoring location 

Total per 

monitoring 

period2

Highest 

TTHM locations 

Highest 

HAA5 locations 

Existing 

Subpart L 

compliance 

locations 

Subpart H: 

<500 .................................. per year ............................. 2 1 1 ....................

500–3,300 ......................... per quarter ........................ 2 1 1 ....................

3,301–9,999 ...................... per quarter ........................ 2 1 1 ....................

10,000–49,999 .................. per quarter ........................ 4 2 1 1 

50,000–249,999 ................ per quarter ........................ 8 3 3 2 

250,000–999,999 .............. per quarter ........................ 12 5 4 3 

1,000,000–4,999,999 ........ per quarter ........................ 16 6 6 4 

≥ 5,000,000 ....................... per quarter ........................ 20 8 7 5 

Ground water: 

<500 .................................. per year ............................. 2 1 1 ....................

500–9,999 ......................... per year ............................. 2 1 1 ....................

10,000–99,999 .................. per quarter ........................ 4 2 1 1 

100,000–499,999 .............. per quarter ........................ 6 3 2 1 

≥ 500,000 .......................... per quarter ........................ 8 3 3 2 

1All systems must monitor during month of highest DBP concentrations. 

2Systems on quarterly monitoring must take dual sample sets every 90 days at each monitoring location, except for subpart H systems serving 

500–3,300. Systems on annual monitoring and subpart H systems serving 500–3,300 are required to take individual TTHM and HAA5 samples 

(instead of a dual sample set) at the locations with the highest TTHM and HAA5 concentrations, respectively. Only one location with a dual sample set per monitoring period is needed if highest TTHM and HAA5 concentrations occur at the same location, and month, if monitored annually). 

Today’s rule provides States the 

flexibility to specify alternative Stage 2 

compliance monitoring requirements 

(but not alternative IDSE monitoring 

requirements) for multiple consecutive 

systems in a combined distribution 

system. As a minimum under such an 

approach, each consecutive system must 

collect at least one sample among the 

total number of samples required for the 

combined distribution system and will 

base compliance on samples collected 

within its distribution system. The 

consecutive system is responsible for 

ensuring that required monitoring is 

completed and the system is in 

compliance. It also must document its 

monitoring strategy as part of its subpart 

V monitoring plan. 

Consecutive systems not already 

conducting disinfectant residual 

monitoring under the Stage 1 DBPR 

must comply with the monitoring 

requirements and MRDLs for chlorine 

and chloramines. States may use the 

provisions of § 141.134(c) to modify 

reporting requirements. For example, 

the State may require that only the 

consecutive system distribution system 

point-of-entry disinfectant 

concentration be reported to 

demonstrate MRDL compliance, 

although monitoring requirements may 

not be reduced. 

i. Reduced monitoring. Systems can 

qualify for reduced monitoring, as 

specified in Table IV.G–3, if the LRAA 

at each location is ≤0.040 mg/L for 

TTHM and ≤0.030 mg/L for HAA5 based 

on at least one year of monitoring at 

routine compliance monitoring 

locations. Systems may remain on 

reduced monitoring as long as the 

TTHM LRAA is ≤0.040 mg/L and the 

HAA5 LRAA is ≤0.030 mg/L at each 

monitoring location for systems with 

quarterly reduced monitoring. If the 

LRAA at any location exceeds either 

0.040 mg/L for TTHM or 0.030 mg/L for 

HAA5 or if the source water annual 

average TOC level, before any treatment, 

exceeds 4.0 mg/L at any of the system’s 

treatment plants treating surface water 

or ground water under the direct 

influence of surface water, the system 

must resume routine monitoring. For 

systems with annual or less frequent 

reduced monitoring, systems may 

remain on reduced monitoring as long 

as each TTHM sample is ≤0.060 mg/L 

and each HAA5 sample is ≤0.045 mg/L. 

If the annual (or less frequent) sample 

at any location exceeds either 0.060 mg/ 

L for TTHM or 0.045 mg/L for HAA5, 

or if the source water annual average 

TOC level, before any treatment, 

exceeds 4.0 mg/L at any treatment plant 

treating surface water or ground water 

under the direct influence of surface 

water, the system must resume routine 

monitoring. 

TABLE IV.G–3.—REDUCED MONITORING FREQUENCY

Source water type Population size category 

Monitoring frequency 1 Distribution system monitoring location per monitoring period 

Subpart H: 

<500 ...................... ........................... Monitoring may not be reduced. 


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TABLE IV.G–3.—REDUCED MONITORING FREQUENCY—Continued 

Source water type Population size category 

Monitoring frequency 1 Distribution system monitoring location per monitoring period 

500–3,300 ............. per year ................. 1 TTHM and 1 HAA5 sample: one at the location and during the quarter with 

the highest TTHM single measurement, one at the location and during the 

quarter with the highest HAA5 single measurement; 1 dual sample set per 

year if the highest TTHM and HAA5 measurements occurred at the same 

location and quarter. 

3,301–9,999 .......... per year ................. 2 dual sample sets: one at the location and during the quarter with the highest 

TTHM single measurement, one at the location and during the quarter with 

the highest HAA5 single measurement. 

10,000–49,999 ...... per quarter ............ 2 dual sample sets at the locations with the highest TTHM and highest HAA5 

LRAAs. 

50,000–249,999 .... per quarter ............ 4 dual sample sets—at the locations with the two highest TTHM and two highest HAA5 LRAAs. 

250,000–999,999 .. per quarter ............ 6 dual sample sets—at the locations with the three highest TTHM and three 

highest HAA5 LRAAs 

1,000,000–

4,999,999.

per quarter ............ 8 dual sample sets—at the locations with the four highest TTHM and four 

highest HAA5 LRAAs. 

≥5,000,000 ............ per quarter ............ 10 dual sample sets—at the locations with the five highest TTHM and five 

highest HAA5 LRAAs. 

Ground Water: 

<500 ...................... every third year ..... 1 TTHM and 1 HAA5 sample: one at the location and during the quarter with 

the highest TTHM single measurement, one at the location and during the 

quarter with the highest HAA5 single measurement; 1 dual sample set per 

year if the highest TTHM and HAA5 measurements occurred at the same 

location and quarter. 

500–9,999 ............. per year ................. 1 TTHM and 1 HAA5 sample: one at the location and during the quarter with 

the highest TTHM single measurement, one at the location and during the 

quarter with the highest HAA5 single measurement; 1 dual sample set per 

year if the highest TTHM and HAA5 measurements occurred at the same 

location and quarter. 

10,000–99,999 ...... per year ................. 2 dual sample sets: one at the location and during the quarter with the highest 

TTHM single measurement, one at the location and during the quarter with 

the highest HAA5 single measurement. 

100,000–499,999 .. per quarter ............ 2 dual sample sets; at the locations with the highest TTHM and highest HAA5 

LRAAs. 

≥500,000 ............... per quarter ............ 4 dual sample sets at the locations with the two highest TTHM and two highest HAA5 LRAAs. 

1Systems on quarterly monitoring must take dual sample sets every 90 days. 

ii. Compliance determination. A PWS 

is in compliance when the annual 

sample or LRAA of quarterly samples is 

less than or equal to the MCLs. If an 

annual sample exceeds the MCL, the 

system must conduct increased 

(quarterly) monitoring but is not 

immediately in violation of the MCL. 

The system is out of compliance if the 

LRAA of the quarterly samples for the 

past four quarters exceeds the MCL. 

Monitoring and MCL violations are 

assigned to the PWS where the violation 

occurred. Several examples are as 

follows: 

• If monitoring results in a 

consecutive system indicate an MCL 

violation, the consecutive system is in 

violation because it has the legal 

responsibility for complying with the 

MCL under State/EPA regulations. The 

consecutive system may set up a 

contract with its wholesale system that 

details water quality delivery 

specifications. 

• If a consecutive system has hired its 

wholesale system under contract to 

monitor in the consecutive system and 

the wholesale system fails to monitor, 

the consecutive system is in violation 

because it has the legal responsibility 

for monitoring under State/EPA 

regulations. 

• If a wholesale system has a 

violation and provides that water to a 

consecutive system, the wholesale 

system is in violation. Whether the 

consecutive system is in violation will 

depend on the situation. The 

consecutive system will also be in 

violation unless it conducted 

monitoring that showed that the 

violation was not present in the 

consecutive system. 

2. Background and Analysis 

EPA proposed the plant-based 

approach for all systems that produce 

some or all of their finished water and 

the population-based monitoring 

approach for systems purchasing all of 

their finished water year-round. As part 

of the proposal, EPA presented a 

monitoring cost analysis for applying 

this approach to all systems in the 

Economic Analysis to better understand 

the impacts of using the populationbased approach. 

The plant-based approach was 

adopted from the 1979 TTHM rule and 

the Stage 1 DBPR and was derived from 

the generally valid assumption that, as 

systems increase in size, they tend to 

have more plants and increased 

complexity. During the development of 

the Stage 2 proposal, EPA identified a 

number of issues associated with the 

use of the plant-based monitoring 

approach. These included: (1) Plantbased monitoring is not as effective as 

population-based monitoring in 

targeting locations with the highest risk; 

(2) a plant-based approach can result in 

disproportionate monitoring 

requirements for systems serving the 

same number of people (due to widely 

varying numbers of plants per system); 

(3) it cannot be adequately applied to 

plants or consecutive system entry 

points that are operated seasonally or 

intermittently if an LRAA is used for 

compliance due to complex 

implementation and a need for repeated 

transactions between the State and 


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system to determine whether and how 

compliance monitoring requirements 

may need to be changed; (4) State 

determinations of monitoring 

requirements for consecutive systems 

would be complicated, especially in 

large combined distribution systems 

with many connections between 

systems; and (5) systems with multiple 

disinfecting wells would have to 

conduct evaluation of common aquifers 

in order to avoid taking unnecessary 

samples for compliance (if they did not 

conduct such evaluations under Stage 

1). EPA requested comment on two 

approaches to address these issues: (1) 

keep the plant-based monitoring 

approach and add new provisions to 

address specific concerns; and (2) base 

monitoring requirements on source 

water type and population served, in 

lieu of plant-based monitoring. 

The final rule’s requirements of 

population-based monitoring for all 

systems are based on improved public 

health protection, flexibility, and 

simplified implementation. For 

determining monitoring requirements, 

EPA’s objective was to maintain 

monitoring loads consistent with Stage 

1 and similar to monitoring loads 

proposed for Stage 2 under a plantbased approach, using a populationbased approach to facilitate 

implementation, better target high DBP 

levels, and protect human health. This 

leads to a more cost-effective 

characterization of where high levels 

occur. For the proposed rule, EPA used 

1995 CWSS data to derive the number 

of plants per system for calculating the 

number of proposed monitoring sites 

per system. During the comment period, 

2000 CWSS data became available. 

Compared to the 1995 CWSS, the 2000 

CWSS contained questions more 

relevant for determining the number of 

plants in each system. Based on 2000 

CWSS data, EPA has modified the 

number of monitoring sites per system 

for several categories (particularly for 

the larger subpart H systems) to align 

the median population-based 

monitoring requirements with the 

median monitoring requirements under 

plant-based monitoring, as was 

proposed. 

EPA also believes that more samples 

are necessary to characterize larger 

systems (as defined by population) than 

for smaller systems. This progressive 

approach is included in Table IV.G–4. 

As system size increases, the number of 

samples increases to better reflect the 

hydraulic complexity of these systems. 

While the national monitoring burden 

under the population-based approach is 

slightly less than under a plant-based 

approach, some larger systems with few 

plants relative to system population will 

take more samples per system than they 

had under plant-based monitoring. 

However, EPA believes that many of 

these large systems with few plants have 

traditionally been undermonitored (as 

noted in the proposal). Systems with 

more plants will see a reduction in 

monitoring (e.g., small ground water 

systems with multiple wells). 

While population-based monitoring 

requirements for ground water systems 

in today’s rule remain the same as those 

in the proposed rule, the final rule 

consolidates ten population categories 

for subpart H systems into eight 

categories for ease of implementation. 

As indicated in Table IV.G–4, EPA has 

gone from four to three population size 

categories for smaller subpart H systems 

(serving fewer than 10,000 people) and 

the ranges have been modified to be 

consistent with those for other existing 

rules (such as the Lead and Copper 

Rule). This change will reduce 

implementation transactional costs. For 

medium and large subpart H systems 

(serving at least 10,000 people), EPA has 

gone from seven categories in the 

proposal to five categories in final rule. 

The population groups are sized so that 

the ratio of maximum population to 

minimum population for each of the 

categories is consistent. EPA believes 

that this will allow most systems to 

remain in one population size category 

and maintain the same monitoring 

requirements within a reasonable range 

of population variation over time. In 

addition, it assures that systems within 

a size category will not have disparate 

monitoring burdens as could occur if 

there were too few categories. Overall, 

EPA believes that the population-based 

monitoring approach allows systems to 

have more flexibility to designate their 

monitoring sites within the distribution 

system to better target high DBP levels 

and is more equitable. 

To derive the number of monitoring 

sites for IDSE standard monitoring, EPA 

doubled the number of routine 

compliance monitoring sites per system 

for each size category. This is consistent 

with the advice and recommendations 

of the M-DBP Advisory Committee for 

the IDSE. EPA has developed the Initial 

Distribution System Evaluation 

Guidance Manual for the Final Stage 2 

Disinfectants and Disinfection 

Byproducts Rule (USEPA 2006) to assist 

systems in choosing IDSE monitoring 

locations, including criteria for selecting 

monitoring. 

TABLE IV.G–4.—COMPARISON OF MONITORING LOCATIONS PER SYSTEM FOR STAGE 2 ROUTINE COMPLIANCE

MONITORING WITH PLANT-BASED AND POPULATION-BASED APPROACHES

Population category 

Ratio of 

maximum 

population 

to minimum 

population 

Number of 

sampling 

periods per 

year 

Plant-based 

approach* 

Number of plants per system (Based on 2000 

CWSS data) 

Calculated number of sites 

per system for plant-based 

approach 

Number of 

monitoring 

sites per 

system for 

pop-based 

approach 

# Sites per 

plant Median Mean 

Based on 

median # 

plants per 

system 

Based on 

mean # 

plants per 

system 

A B C D E=B*C F=B*D G 

<500 .................................................................. .................... 1 **1 1 1.21 1 1.2 **1 

500–3,300 ......................................................... 6.6 4 **1 1 1.22 1 1.2 **1 

3,301–9,999 ...................................................... 3 4 2 1 1.56 2 3.1 2 

10,000–49,999 .................................................. 5 4 4 1 1.37 4 5.5 4 

50,000–249,999 ................................................ 5 4 4 1 1.83 4 7.3 8 

250,000–<1 million ............................................ 4 4 4 2 2.53 8 10.1 12 

1 million–<5 million ........................................... 5 4 4 4 3.62 16 14.5 16 

≥5 million ........................................................... .................... 4 4 4 4.33 16 17.3 20 

* As in the proposal. 

** System is required to take individual TTHM and HAA5 samples at the locations with the highest TTHM and HAA5 concentrations, respectively, if highest TTHM 

and HAA5 concentrations do not occur at the same location. 


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Note: To determine the number of routine compliance monitoring sites per population category, EPA took these steps: (1) Maintaining about the same sampling 

loads in the nation as required under the plant-based approach, but basing on population rather than number of plants to better target high DBP levels in distribution 

systems and facilitate implementation; (2) The number of monitoring sites per plant under the plant-based approach (Column B) were multiplied by the number of 

plants per system (Columns C and D) to calculate the number of monitoring sites per system under the plant-based approach (Columns E and F in terms of median 

and mean, respectively); and (3) The number of monitoring sites per system under the population-based approach were derived with adjustments to keep categories 

consistent and to maintain an even incremental trend as the population size category increases (Column G). 

3. Summary of Major Comments 

EPA received significant support for 

applying the population-based approach 

to all systems. EPA also received 

comments concerning the specific 

requirements in a population-based 

approach. 

Excessive Sampling Requirements. 

Several commenters believed that the 

proposed sampling requirements were 

excessive (especially in the larger 

population categories for subpart H 

systems) and that some individual 

systems would be required to sample 

more under the population-based 

approach than the plant-based 

approach. EPA recognizes that a small 

fraction of systems in some categories 

will have to take more samples under 

the population-based approach than the 

plant-based approach because their 

number of plants is substantially less 

than the national median or mean. 

However, the number of samples 

required under the Stage 1 DBPR for 

these systems may not have been 

sufficient to determine the 

concentrations of DBPs throughout the 

distribution system of these systems. On 

the other hand, systems with many 

plants may have taken excessive 

samples under the Stage 1 DBPR that 

were not necessary to appropriately 

determine DBP levels throughout the 

distribution system. Consequently, the 

total number of samples taken 

nationally will be comparable to the 

Stage 1 DBPR, but will better target DBP 

risks in individual distribution systems. 

Consecutive systems. Some 

commenters noted that a consecutive 

system may need to take more samples 

than its associated wholesale system. 

Under today’s rule, all systems, 

including consecutive systems, must 

monitor based on retail population 

served. Thus, large consecutive systems 

will take more samples than a smaller 

wholesale system. The population-based 

monitoring approach will allow the 

samples to better represent the DBP 

concentrations consumed by the 

population associated with the sampling 

locations and to understand the DBP 

concentrations reaching consumers. 

There is also a provision that allows 

States to specify alternative monitoring 

requirements for a consecutive system 

in a combined distribution system (40 

CFR 142.16(m)(3)). This special primacy 

condition allows the State to establish 

monitoring requirements that account 

for complicated distribution system 

relationships, such as where 

neighboring systems buy from and sell 

to each other regularly throughout the 

year. In this case, water may pass 

through multiple consecutive systems 

before it reaches a user. Another 

example would be a large group of 

interconnected systems that have a 

complicated combined distribution 

system. This approach also allows the 

combined distribution system to 

concentrate IDSE and Stage 2 

monitoring sites in the system with the 

highest known DBP concentrations, 

while assigning fewer sample sites to 

systems with low DBP concentrations. 

Population Size Categories. Some 

commenters recommended fewer 

population categories for subpart H 

systems (those using surface water or 

ground water under the direct influence 

of surface water as a source) than 

proposed while others recommended 

more. Today’s rule has fewer categories 

than proposed. However, EPA believes 

that further reduction of the number of 

population size categories will not 

reflect the fact that the number of plants 

and complexity of distribution systems 

(and DBP exposure) tend to increase as 

the population served increases. As a 

result, the population served by a large 

system in one particular category would 

receive much less protection from the 

DBP risks than a smaller system in the 

same size category. On the other hand, 

too many categories with smaller 

population ranges would result in 

frequent category and requirement shifts 

as population fluctuates. Much greater 

implementation effort would be needed 

for those systems without much benefit 

in DBP exposure knowledge. 

Population Definition. Some 

commenters supported use of the 

population of a combined distribution 

system (i.e., the wholesale and 

consecutive systems should be 

considered a single system for 

monitoring purposes) while others 

preferred use of the retail population for 

each individual system (i.e., wholesale 

systems and consecutive systems are 

considered separately). Today’s final 

rule uses the retail population for each 

individual system. EPA chose this 

approach for today’s rule because of the 

complexity involved in making 

implementation decisions for 

consecutive systems. Using the retail 

population to determine requirements 

eases the complexity by specifying 

minimum system-level requirements; 

simplicity is essential for meeting the 

implementation schedule in today’s 

rule. If monitoring requirements were 

determined by the combined 

distribution system population, many 

implementation problems would occur. 

Some of these problems would have the 

potential to impact public health 

protection. For example, States or 

primacy agencies would have to decide 

how to allocate IDSE distribution 

system samples (where and how much 

to monitor in individual PWSs) in a 

complicated combined distribution 

system with many systems, multiple 

sources, multiple treatment plants, and 

varying water demand and with limited 

understanding of DBP levels throughout 

the combined distribution system. This 

would have to happen shortly after rule 

promulgation in order to meet the 

schedule. For example, some 

consecutive systems buy water 

seasonally (in times of high water 

demand) or buy from more than one 

wholesale system (with the volume 

purchased based on many factors). The 

State or primacy agency would find it 

difficult to properly assign a limited 

number of IDSE monitoring locations 

(especially since there are States where 

many consecutive systems have no DBP 

data) to adequately reflect DBP levels in 

such a system, as well as throughout the 

combined distribution system. 

EPA believes that assigning 

compliance monitoring requirements 

appropriately throughout the combined 

distribution system requires a case-bycase determination based on factors 

such as amount and percentage of 

finished water provided; whether 

finished water is provided seasonally, 

intermittently, or full-time; and 

improved DBP occurrence information. 

Since the IDSE will provide improved 

DBP occurrence information throughout 

the combined distribution system, 

States may consider modifications to 

Stage 2 compliance monitoring 

requirements for consecutive systems on 

a case-by-case basis as allowed by 

§ 141.29 or under the special primacy 

condition at § 142.16(m)(3) by taking all 

these factors into consideration. In 

making these case-by-case 

determinations, the State will be able to 

use its system-specific knowledge, along 

with the IDSE results, to develop an 

appropriate monitoring plan for each 


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system within the combined 

distribution system. 

Changes to monitoring plans. 

Commenters requested more specific 

language regarding how IDSE and Stage 

2 monitoring plans should be updated 

as a result of treatment or population 

changes in the distribution system. 

Changes to IDSE plans should not be 

necessary since the State or primacy 

agency will have reviewed those plans 

shortly before the system must conduct 

the IDSE and the reviewed plan should 

identify such issues. EPA provided a 

process in the Stage 2 DBPR proposal 

for updating monitoring plans for 

systems that have significant changes to 

treatment or in the distribution system 

after they complete their IDSE. This 

process remains in today’s rule, with an 

added requirement that systems must 

consult with the State or primacy 

agency to determine whether the 

changes are necessary and appropriate 

prior to implementing changes to their 

Stage 2 monitoring plan. 

In addition, the State or primacy 

agency may require a system to revise 

its IDSE plan, IDSE report, or Stage 2 

monitoring plan at any time. This 

change was made so that systems could 

receive system-specific guidance from 

the State or primacy agency on the 

appropriate revisions to the Stage 2 

monitoring plan. Regulatory language 

regarding changes that might occur is 

not appropriate because any 

modifications would be system-specific 

and a national requirement is not 

capable of addressing these systemspecific issues. 

H. Operational Evaluation 

Requirements Initiated by TTHM and 

HAA5 Levels 

A system that is in full compliance 

with the Stage 2 DBPR LRAA MCL may 

still have individual DBP measurements 

that exceed the Stage 2 DBPR MCLs, 

since compliance is based on individual 

DBP measurements at a location 

averaged over a four-quarter period. 

EPA and the Advisory Committee were 

concerned about these higher levels of 

DBPs. This concern was clearly 

reflected in the Agreement in Principle, 

which states, ‘‘. . . significant 

excursions of DBP levels will sometimes 

occur, even when systems are in full 

compliance with the enforceable 

MCL. . .’’. 

Today’s final rule addresses this 

concern by requiring systems to conduct 

operational evaluations that are initiated 

by operational evaluation levels 

identified in Stage 2 DBPR compliance 

monitoring and to submit an operational 

evaluation report to the State. 

1. Today’s Rule 

Today’s rule defines the Stage 2 DBP 

operational evaluation levels that 

require systems to conduct operational 

evaluations. The Stage 2 DBP 

operational evaluation levels are 

identified using the system’s Stage 2 

DBPR compliance monitoring results. 

The operational evaluation levels for 

each monitoring location are 

determined by the sum of the two 

previous quarters’ TTHM results plus 

twice the current quarter’s TTHM result, 

at that location, divided by 4 to 

determine an average and the sum of the 

two previous quarters’ HAA5 results 

plus twice the current quarter’s HAA5 

result, at that location, divided by 4 to 

determine an average. If the average 

TTHM exceeds 0.080 mg/L at any 

monitoring location or the average 

HAA5 exceeds 0.060 mg/L at any 

monitoring location, the system must 

conduct an operational evaluation and 

submit a written report of the 

operational evaluation to the State. 

Operational evaluation levels 

(calculated at each monitoring location) 

IF (Q1 + Q2 + 2Q3)/4> MCL, then the 

system must conduct an operational 

evaluation 

where: 

Q3 = current quarter measurement 

Q2 = previoius quarter measurement 

Q1 = quarter before previous quarter 

measurement 

MCL = Stage 2 MCL for TTHM (0.080 

mg/l) or Stage 2 MCL for HAA5 (0.060 

mg/L) 

The operational evaluation includes 

an examination of system treatment and 

distribution operational practices, 

including changes in sources or source 

water quality, storage tank operations, 

and excess storage capacity, that may 

contribute to high TTHM and HAA5 

formation. Systems must also identify 

what steps could be considered to 

minimize future operational evaluation 

level exceedences. In cases where the 

system can identify the cause of DBP 

levels that resulted in the operational 

evaluation, based on factors such as 

water quality data, plant performance 

data, and distribution system 

configuration the system may request 

and the State may allow limiting the 

evaluation to the identified cause. The 

State must issue a written determination 

approving limiting the scope of the 

operational evaluation. The system must 

submit their operational evaluation 

report to the State for review within 90 

days after being notified of the 

analytical result that initiates the 

operational evaluation. Requesting 

approval to limit the scope of the 

operational evaluation does not extend 

the schedule (90 days after notification 

of the analytical result) for submitting 

the operational evaluation report. 

2. Background and Analysis 

The Stage 2 DBPR proposal outlined 

three components of the requirements 

for significant excursions (definition, 

system evaluation and excursion 

report). In response to public comments, 

the term ‘‘significant excursion’’ has 

been replaced by the term ‘‘operational 

evaluation level’’ in today’s rule. The 

evaluation and report components 

remain the same as those outlined in the 

proposed rule for significant excursions. 

However, the scope of the evaluation 

and report components of the 

operational evaluation has also been 

modified from the proposed significant 

excursion evaluation components based 

on public comments. 

In the Stage 2 DBPR proposal, States 

were to define criteria to identify 

significant excursions rather than using 

criteria defined by EPA. Concurrent 

with the Stage 2 DBPR proposal, EPA 

issued draft guidance (USEPA 2003e) 

for systems and States that described 

how to determine whether a significant 

excursion has occurred, using several 

different options. The rule proposal 

specifically requested public comment 

on the definition of a significant 

excursion, whether it should be defined 

by the State or nationally, and the scope 

of the evaluation. 

After reviewing comments on the 

Stage 2 DBPR proposal, EPA determined 

that DBP levels initiating an operational 

evaluation should be defined in the 

regulation to ensure national 

consistency. Systems were concerned 

with the evaluation requirements being 

initiated based on criteria that might not 

be consistent nationally. Also, many 

States believed the requirement for 

States to define criteria to initiate an 

evaluation would be difficult for States 

to implement. 

Under today’s rule, EPA is defining 

operational evaluation levels with an 

algorithm based on Stage 2 DBPR 

compliance monitoring results. These 

operational evaluation levels will act as 

an early warning for a possible MCL 

violation in the following quarter. This 

early warning is accomplished because 

the operational evaluation requirement 

is initiated when the system assumes 

that the current quarter’s result is 

repeated and this will result in an MCL 

violation. This early identification 

allows the system to act to prevent the 

violation. 

Today’s rule also modifies the scope 

of an operational evaluation. EPA has 

concluded that the source of DBP levels 


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that would initiate an operational 

evaluation can potentially be linked to 

a number of factors that extend beyond 

distribution system operations. 

Therefore, EPA believes that evaluations 

must include a consideration of 

treatment plant and other system 

operations rather than limiting the 

operational evaluation to only the 

distribution system, as proposed. 

Because the source of the problem could 

be associated with operations in any of 

these system components (or more than 

one), an evaluation that provides 

systems with valuable information to 

evaluate possible modifications to 

current operational practices (e.g. water 

age management, source blending) or in 

planning system modifications or 

improvements (e.g. disinfection 

practices, tank modifications, 

distribution looping) will reduce DBP 

levels initiating an operational 

evaluation. EPA also believes that State 

review of operational evaluation reports 

is valuable for both States and systems 

in their interactions, particularly when 

systems may be in discussions with or 

requesting approvals from the State for 

system improvements. Timely reviews 

of operational evaluation reports will be 

valuable for States in reviewing other 

compliance submittals and will be 

particularly valuable in reviewing and 

approving any proposed source, 

treatment or distribution system 

modifications for a water system. Under 

today’s rule, systems must submit a 

written report of the operational 

evaluation to the State no later than 90 

days after being notified of the DBP 

analytical result initiating an 

operational evaluation. The written 

operational evaluation report must also 

be made available to the public upon 

request. 

3. Summary of Major Comments 

EPA received comments both in favor 

of and opposed to the proposed 

evaluation requirements. While some 

commenters felt that the evaluation 

requirements should not be a part of the 

Stage 2 DBPR until there was more 

information regarding potential health 

effects correlated to specific DBP levels, 

other commenters felt that the existing 

health effects data were sufficient to 

warrant strengthening the proposed 

requirements for an evaluation. Today’s 

final rule requirements are consistent 

with the Agreement in Principle 

recommendations. 

Some commenters noted that health 

effects research on DBPs is insufficient 

to identify a level at which health 

effects occur and were concerned that 

the proposed significant excursion 

requirements placed an emphasis on 

DBP levels that might not be warranted 

rather than on system operational issues 

and compliance with Stage 2 DBPR 

MCLs. 

Basis. The proposed requirements for 

significant excursion evaluations were 

not based upon health effects, but rather 

were intended to be an indicator of 

operational performance. To address 

commenter’s concerns and to emphasize 

what EPA believes should initiate a 

comprehensive evaluation of system 

operations that may result in elevated 

DBP levels and provide a proactive 

procedure to address compliance with 

Stage 2 DBP LRAA MCLs , EPA has 

replaced the term ‘‘significant 

excursion’’ used in the Stage 2 DBPR 

proposal with the term ‘‘operational 

evaluation level’’ in today’s rule. 

Definition of the operational 

evaluation levels. The majority of 

commenters stated that EPA should 

define the DBP levels initiating an 

operational evaluation (‘‘significant 

excursion’’ in the proposal) in the 

regulation to ensure national 

consistency rather than requiring States 

to develop their own criteria (as was 

proposed). Commenters suggested 

several definitions, including a single 

numerical limit and calculations 

comparing previous quarterly DBP 

results to the current quarter’s result. 

Commenters that recommended a single 

numerical limit felt that such an 

approach was justified by the available 

health effects information, while other 

commenters felt available heath effects 

information did not support a single 

numerical limit. Commenters 

recommended that any definition be 

easy to understand and implement. 

EPA agrees with commenter 

preference for national criteria to 

initiate an operational evaluation. The 

DBP levels initiating an operational 

evaluation in today’s rule consider 

routine operational variations in 

distribution systems, are simple for 

water systems to calculate, and 

minimize the implementation burden 

on States. They also provide an early 

warning to help identify possible future 

MCL violations and allow the system to 

take proactive steps to remain in 

compliance. EPA emphasizes, as it did 

in the proposal and elsewhere in this 

notice, that health effects research is 

insufficient to identify a level at which 

health effects occur, and thus today’s 

methodology for initiating operational 

evaluation is not based upon health 

effects, but rather is intended as an 

indicator of operational performance. 

Scope of an evaluation. Some 

commenters felt that the scope of an 

evaluation initiated by locational DBP 

levels should be limited to the 

distribution systems, as in the proposal. 

Others felt that the treatment processes 

should be included in the evaluation, 

noting that these can be significant in 

the formation of DBPs. 

The Agency agrees with commenters 

that treatment processes can be a 

significant factor in DBP levels initiating 

an operational evaluation and that a 

comprehensive operational evaluation 

should address treatment processes. In 

cases where the system can clearly 

identify the cause of the DBP levels 

initiating an operational evaluation 

(based on factors such as water quality 

data, plant performance data, 

distribution system configuration, and 

previous evaluations) the State may 

allow the system to limit the scope of 

the evaluation to the identified cause. In 

other cases, it is appropriate to evaluate 

the entire system, from source through 

treatment to distribution system 

configuration and operational practices. 

Timing for completion and review of 

the evaluation report. While some 

commenters agreed that the evaluation 

report should be reviewed as part of the 

sanitary survey process (as proposed), 

many commenters felt that the time 

between sanitary surveys (up to five 

years) minimized the value of the 

evaluation report in identifying both the 

causes of DBP levels initiating an 

operational evaluation and in possible 

changes to prevent recurrence. 

Moreover, a number of commenters felt 

that the evaluation report was important 

enough to warrant a separate submittal 

and State review rather than have the 

evaluation report compete with other 

priorities during a sanitary survey. 

The Agency agrees that completion 

and State review of evaluation reports 

on a three or five year sanitary survey 

cycle, when the focus of the evaluation 

is on what may happen in the next 

quarter, would allow for an 

unreasonable period of time to pass 

between the event initiating the 

operational evaluation and completion 

and State review of the report. This 

would diminish the value of the 

evaluation report for both systems and 

States, particularly when systems may 

be in discussions with or requesting 

approval for treatment changes from 

States, and as noted above, the focus of 

the report is on what may occur in the 

next quarter. EPA believes that timely 

reviews of evaluation reports by States 

is important, would be essential for 

States in understanding system 

operations and reviewing other 

compliance submittals, and would be 

extremely valuable in reviewing and 

approving any proposed source, 

treatment or distribution system 

modifications for a water system. 


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Having the evaluation information on an 

ongoing basis rather than a delayed 

basis would also allow States to 

prioritize their resources in scheduling 

and reviewing particular water system 

operations and conditions as part of any 

on-site system review or oversight. 

Therefore, today’s rule requires that 

systems complete the operational 

evaluation and submit the evaluation 

report to the State within 90 days of the 

occurrence. 

I. MCL, BAT, and Monitoring for 

Bromate 

1. Today’s Rule 

Today EPA is confirming that the 

MCL for bromate for systems using 

ozone remains at 0.010 mg/L as an RAA 

for samples taken at the entrance to the 

distribution system as established by the 

Stage 1 DBPR. Because the MCL remains 

the same, EPA is not modifying the 

existing bromate BAT. EPA is changing 

the criterion for a system using ozone to 

qualify for reduced bromate monitoring 

from demonstrating low levels of 

bromide to demonstrating low levels of 

bromate. 

2. Background and Analysis 

a. Bromate MCL. Bromate is a 

principal byproduct from ozonation of 

bromide-containing source waters. As 

described in more detail in the Stage 2 

DBPR proposal (USEPA 2003a), more 

stringent bromate MCL has the potential 

to decrease current levels of microbial 

protection, impair the ability of systems 

to control resistant pathogens like 

Cryptosporidium, and increase levels of 

DBPs from other disinfectants that may 

be used instead of ozone. EPA 

considered reducing the bromate MCL 

from 0.010 mg/L to 0.005 mg/L as an 

annual average but concluded that many 

systems using ozone to inactivate 

microbial pathogens would have 

significant difficulty maintaining 

bromate levels at or below 0.005 mg/L. 

In addition, because of the high doses 

required, the ability of systems to use 

ozone to meet Cryptosporidium 

treatment requirements under the 

LT2ESWTR would be diminished if the 

bromate MCL was decreased from 0.010 

to 0.005 mg/L; higher doses will 

generally lead to greater bromate 

formation. After evaluation under the 

risk-balancing provisions of section 

1412(b)(5) of the SDWA, EPA concluded 

that the existing MCL was justified. EPA 

will review the bromate MCL as part of 

the six-year review process and 

determine whether the MCL should 

remain at 0.010 mg/L or be reduced to 

a lower level. As a part of that review, 

EPA will consider the increased 

utilization of alternative technologies, 

such as UV, and whether the risk/risk 

concerns reflected in today’s rule, as 

well as in the LT2ESWTR, remain valid. 

b. Criterion for reduced bromate 

monitoring. Because more sensitive 

bromate methods are now available, 

EPA is requiring a new criterion for 

reduced bromate monitoring. In the 

Stage 1 DBPR, EPA required ozone 

systems to demonstrate that source 

water bromide levels, as a running 

annual average, did not exceed 0.05 mg/ 

L. EPA elected to use bromide as a 

surrogate for bromate in determining 

eligibility for reduced monitoring 

because the available analytical method 

for bromate was not sensitive enough to 

quantify levels well below the bromate 

MCL of 0.010 mg/L. 

EPA approved several new analytical 

methods for bromate that are far more 

sensitive than the existing method as 

part of today’s rule. Since these methods 

can measure bromate to levels of 0.001 

mg/L or lower, EPA is replacing the 

criterion for reduced bromate 

monitoring (source water bromide 

running annual average not to exceed 

0.05 mg/L) with a bromate running 

annual average not to exceed 0.0025 mg/ 

L. 

In the past, EPA has often set the 

criterion for reduced monitoring 

eligibility at 50% of the MCL, which 

would be 0.005 mg/L. However, the 

MCL for bromate will remain at 0.010 

mg/L, representing a risk level of 2×10/ 

b 2×10¥4, 10¥4 and 10¥6 (higher than 

EPA’s usual excess cancer risk range of 

10¥4 to 10¥6) because of risk tradeoff 

considerations) (USEPA 2003a). 

EPA believes that the decision for 

reduced monitoring is separate from 

these risk tradeoff considerations. Risk 

tradeoff considerations influence the 

selection of the MCL, while reduced 

monitoring requirements are designed to 

ensure that the MCL, once established, 

is reliably and consistently achieved. 

Requiring a running annual average of 

0.0025 mg/L for the reduced monitoring 

criterion allows greater confidence that 

the system is achieving the MCL and 

thus ensuring public health protection. 

3. Summary of Major Comments 

Commenters supported both the 

retention of the existing bromate MCL 

and the modified reduced monitoring 

criterion. 

J. Public Notice Requirements 

1. Today’s Rule 

Today’s rule does not alter existing 

public notification language for TTHM, 

HAA5 or TOC, which are listed under 

40 CFR 141.201–141.210 (Subpart Q). 

2. Background and Analysis 

EPA requested comment on including 

language in the proposed rule 

concerning potential reproductive and 

developmental health effects. EPA 

believes this is an important issue 

because of the large population exposed 

(58 million women of child-bearing age; 

USEPA 2005a) and the number of 

studies that, while not conclusive, point 

towards a potential risk concern. While 

EPA is not including information about 

reproductive and developmental health 

effects in public notices at this time, the 

Agency plans to reconsider whether to 

include this information in the future. 

As part of this effort, EPA intends to 

support research to assess 

communication strategies on how to 

best provide this information. 

The responsibilities for public 

notification and consumer confidence 

reports rest with the individual system. 

Under the Public Notice Rule (Part 141 

subpart Q) and Consumer Confidence 

Report Rule (Part 141 subpart O), the 

wholesale system is responsible for 

notifying the consecutive system of 

analytical results and violations related 

to monitoring conducted by the 

wholesale system. Consecutive systems 

are required to conduct appropriate 

public notification after a violation 

(whether in the wholesale system or the 

consecutive system). In their consumer 

confidence report, consecutive systems 

must include results of the testing 

conducted by the wholesale system 

unless the consecutive system 

conducted equivalent testing (as 

required in today’s rule) that indicated 

the consecutive system was in 

compliance, in which case the 

consecutive system reports its own 

compliance monitoring results. 

3. Summary of Major Comments 

EPA requested and received many 

comments on the topic of including 

public notification language regarding 

potential reproductive and 

developmental effects. A number of 

comments called for including 

reproductive and developmental health 

effects language to address the potential 

health concerns that research has 

shown. Numerous comments also 

opposed such language due to 

uncertainties in the underlying science 

and the implications such language 

could have on public trust of utilities. 

EPA agrees on the importance of 

addressing possible reproductive and 

developmental health risks. However, 

given the uncertainties in the science 

and our lack of knowledge of how to 

best communicate undefined risks, a 

general statement about reproductive 


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and developmental health effects is 

premature at this time. The Agency 

needs to understand how best to 

characterize and communicate these 

risks and what to do to follow up any 

such communication. The public 

deserves accurate, timely, relevant, and 

understandable communication. The 

Agency will continue to follow up on 

this issue with additional research, 

possibly including a project to work 

with stakeholders to assess risk 

communication strategies. 

Some comments also suggested 

leaving the choice of language up to the 

water server. EPA believes that this 

strategy would cause undue confusion 

to both the PWS and the public. 

Commenters generally agreed that 

both wholesale and consecutive systems 

that conduct monitoring be required to 

report their own analytical results as 

part of their CCRs. One commenter 

requested clarification of consecutive 

system public notification requirements 

when there is a violation in the 

wholesale system but the consecutive 

system data indicate that it meets DBP 

MCLs. 

Although EPA requires consecutive 

systems to conduct appropriate public 

notification of violations (whether in the 

wholesale or consecutive system), there 

may be cases where the violation may 

only affect an isolated portion of the 

distribution system. Under the public 

notification rule, the State may allow 

systems to limit distribution of the 

notice to the area that is out of 

compliance if the system can 

demonstrate that the violation occurred 

in a part of the distribution system that 

is ‘‘physically or hydraulically isolated 

from other parts of the distribution 

system.’’ This provision remains in 

place. As for a consecutive system 

whose wholesale system is in violation, 

the consecutive system is not required 

to conduct public notification if DBP 

levels in the consecutive system are in 

compliance. 

K. Variances and Exemptions 

1. Today’s Rule 

States may grant variances in 

accordance with sections 1415(a) and 

1415(e) of the SDWA and EPA’s 

regulations. States may grant 

exemptions in accordance with section 

1416(a) of the SDWA and EPA’s 

regulations. 

2. Background and Analysis 

a. Variances. The SDWA provides for 

two types of variances—general 

variances and small system variances. 

Under section 1415(a)(1)(A) of the 

SDWA, a State that has primary 

enforcement responsibility (primacy), or 

EPA as the primacy agency, may grant 

general variances from MCLs to those 

public water systems of any size that 

cannot comply with the MCLs because 

of characteristics of the raw water 

sources. The primacy agency may grant 

general variances to a system on 

condition that the system install the best 

technology, treatment techniques, or 

other means that EPA finds available 

and based upon an evaluation 

satisfactory to the State that indicates 

that alternative sources of water are not 

reasonably available to the system. At 

the time this type of variance is granted, 

the State must prescribe a compliance 

schedule and may require the system to 

implement additional control measures. 

Furthermore, before EPA or the State 

may grant a general variance, it must 

find that the variance will not result in 

an unreasonable risk to health (URTH) 

to the public served by the public water 

system. In today’s final rule, EPA is 

specifying BATs for general variances 

under section 1415(a) (see section IV.D). 

Section 1415(e) authorizes the 

primacy agency to issue variances to 

small public water systems (those 

serving fewer than 10,000 people) where 

the primacy agent determines (1) that 

the system cannot afford to comply with 

an MCL or treatment technique and (2) 

that the terms of the variances will 

ensure adequate protection of human 

health (63 FR 43833, August 14, 1998) 

(USEPA 1998c). These variances may 

only be granted where EPA has 

determined that there is no affordable 

compliance technology and has 

identified a small system variance 

technology under section 1412(b)(15) for 

the contaminant, system size and source 

water quality in question. As discussed 

below, small system variances under 

section 1415(e) are not available because 

EPA has determined that affordable 

compliance technologies are available. 

The 1996 Amendments to the SDWA 

identify three categories of small public 

water systems that need to be addressed: 

(1) Those serving a population of 3301–

10,000; (2) those serving a population of 

500–3300; and (3) those serving a 

population of 25–499. The SDWA 

requires EPA to make determinations of 

available compliance technologies for 

each size category. A compliance 

technology is a technology that is 

affordable and that achieves compliance 

with the MCL and/or treatment 

technique. Compliance technologies can 

include point-of-entry or point-of-use 

treatment units. Variance technologies 

are only specified for those system size/ 

source water quality combinations for 

which there are no listed affordable 

compliance technologies. 

Using its current National 

Affordability Criteria, EPA has 

determined that multiple affordable 

compliance technologies are available 

for each of the three system sizes 

(USEPA 2005a), and therefore did not 

identify any variance treatment 

technologies. The analysis was 

consistent with the current methodology 

used in the document ‘‘National-Level 

Affordability Criteria Under the 1996 

Amendments to the Safe Drinking Water 

Act’’ (USEPA 1998d) and the ‘‘Variance 

Technology Findings for Contaminants 

Regulated Before 1996’’ (USEPA 1998e). 

However, EPA is currently reevaluating 

its national-level affordability criteria 

and has solicited recommendations 

from both the NDWAC and the SAB as 

part of this review. EPA intends to 

apply the revised criteria to the Stage 2 

DBPR once they have been finalized for 

the purpose of determining whether to 

enable States to give variances. Thus, 

while the analysis of Stage 2 household 

costs will not change, EPA’s 

determination regarding the availability 

of affordable compliance technologies 

for the different categories of small 

systems may. 

b. Affordable Treatment Technologies 

for Small Systems. The treatment trains 

considered and predicted to be used in 

EPA’s compliance forecast for systems 

serving under 10,000 people, are listed 

in Table IV.K–1. 

TABLE IV.K–1.—TECHNOLOGIES CONSIDERED AND PREDICTED TO BE USED IN COMPLIANCE FORECAST FOR SMALL

SYSTEMS

SW Water Plants GW Water Plants 

• Switching to chloramines as a residual disinfectant ............................. • Switching to chloramines as a residual disinfectant 

• Chlorine dioxide (not for systems serving fewer than 100 people) ...... • UV 

• UV ......................................................................................................... • Ozone (not for systems serving fewer than 100 people) 

• Ozone (not for systems serving fewer than 100 people) ..................... • GAC20 

• Micro-filtration/Ultra-filtration ................................................................. • Nanofiltration 


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TABLE IV.K–1.—TECHNOLOGIES CONSIDERED AND PREDICTED TO BE USED IN COMPLIANCE FORECAST FOR SMALL

SYSTEMS—Continued 

SW Water Plants GW Water Plants 

• GAC20.

• GAC20 + Advanced disinfectants.

• Integrated Membranes.

Note: Italicized technologies are those predicted to be used in the compliance forecast. 

Source: Exhibits 5.11b and 5.14b, USEPA 2005a. 

The household costs for these 

technologies were compared against the 

EPA’s current national-level 

affordability criteria to determine the 

affordable treatment technologies. The 

Agency’s national level affordability 

criteria were published in the August 6, 

1998 Federal Register (USEPA 1998d). 

A complete description of how this 

analysis was applied to Stage 2 DBPR is 

given in Section 8.3 of the Economic 

Analysis (USEPA 2005a). Of the technologies listed in Table 

IV.K–1, integrated membranes with 

chloramines, GAC20 with advanced 

oxidants, and ozone are above the 

affordability threshold in the 0 to 500 

category. No treatment technologies are 

above the affordability threshold in the 

500 to 3,300 category or the 3,300 to 

10,000 category. As shown in the 

Economic Analysis for systems serving 

fewer than 500 people, 14 systems are 

predicted to use GAC20 with advanced 

disinfectants, one system is predicted to 

use integrated membranes, and no 

systems are predicted to use ozone to 

comply with the Stage 2 DBPR (USEPA 

2005a). However, several alternate 

technologies are affordable and likely 

available to these systems. In some 

cases, the compliance data for these 

systems under the Stage 2 DBPR will be 

the same as under the Stage 1 DBPR 

(because many systems serving fewer 

than 500 people will have the same 

single sampling site under both rules); 

these systems will have already 

installed the necessary compliance 

technology to comply with the Stage 1 

DBPR. It is also possible that less costly 

technologies such as those for which 

percentage use caps were set in the 

decision tree may actually be used to 

achieve compliance (e.g., chloramines, 

UV). Thus, EPA believes that 

compliance by these systems will be 

affordable. 

As shown in Table IV.K–2, the cost 

model predicts that some households 

served by very small systems will 

experience household cost increases 

greater than the available expenditure 

margins as a result of adding advanced 

technology for the Stage 2 DBPR 

(USEPA 2005a). This prediction may be 

overestimated because small systems 

may have other compliance alternatives 

available to them besides adding 

treatment, which were not considered in 

the model. For example, some of these 

systems currently may be operated on a 

part-time basis; therefore, they may be 

able to modify the current operational 

schedule or use excessive capacity to 

avoid installing a costly technology to 

comply with the Stage 2 DBPR. The 

system also may identify another water 

source that has lower TTHM and HAA5 

precursor levels. Systems that can 

identify such an alternate water source 

may not have to treat that new source 

water as intensely as their current 

source, resulting in lower treatment 

costs. Systems may elect to connect to 

a neighboring water system. While 

connecting to another system may not 

be feasible for some remote systems, 

EPA estimates that more than 22 percent 

of all small water systems are located 

within metropolitan regions (USEPA 

2000f) where distances between 

neighboring systems will not present a 

prohibitive barrier. Low-cost 

alternatives to reduce total 

trihalomethanes (TTHM) and haloacetic 

acid (HAA5) levels also include 

distribution system modifications such 

as flushing distribution mains more 

frequently, looping to prevent dead 

ends, and optimizing storage to 

minimize retention time. More 

discussion of household cost increases 

is presented in Section VI.E and the 

Economic Analysis (USEPA 2005a). 

TABLE IV.K–2.—DISTRIBUTION OF HOUSEHOLD UNIT TREATMENT COSTS FOR PLANTS ADDING TREATMENT

Systems size 

(population 

seved) 

Number of 

households 

served by 

plants adding treatment (Percent of all 

households 

subject to 

the Stage 2 

DBPR) 

Mean annual household cost increase Median annual household cost increase 

90th Percentile annual household cost increase 95th Percentile annual household cost increase 

Available 

expenditure 

margin ($/ 

hh/yr) 

Number of 

households 

with annual 

cost increases 

greater than 

the available expenditure 

margin 

Number of 

surface 

water plants 

with annual 

cost increases 

greater than 

the available expenditure 

margin 

Number of 

groundwater 

plants with 

annual cost 

increases 

greater than 

the available expenditure 

margin 

Total number of plants 

with annual 

cost increases 

greater than 

the available expenditure 

margin 

A B C D E F G H I J = H + I 

0–500 ................ 43045(3) $201.55 $299.01 $299.01 $414.74 $733 964 15 0 15 

501–3,300 ......... 205842 (4) $58.41 $29.96 $75.09 $366.53 $724 0 9 0 0 

3,301–10,000 .... 342525 (5) $37.05 $14.59 $55.25 $200.05 $750 0 0 0 0 

Notes: Household unit costs represent treatment costs only. All values in year 2003 dollars. 

Source: Exhibit 8.4c, USEPA 2005a. 

c. Exemptions. Under section 1416(a), 

EPA or a State that has primary 

enforcement responsibility (primacy) 

may exempt a public water system from 

any requirements related to an MCL or 

treatment technique of an NPDWR, if it 

finds that (1) due to compelling factors 

(which may include economic factors 

such as qualification of the PWS as 

serving a disadvantaged community), 

the PWS is unable to comply with the 

requirement or implement measures to 

develop an alternative source of water 

supply; (2) the exemption will not result 

in an unreasonable risk to health; and; 

(3) the PWS was in operation on the 

effective date of the NPDWR, or for a 

system that was not in operation by that 

date, only if no reasonable alternative 

source of drinking water is available to 

the new system; and (4) management or 

restructuring changes (or both) cannot 

reasonably result in compliance with 

the Act or improve the quality of 


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drinking water. If EPA or the State 

grants an exemption to a public water 

system, it must at the same time 

prescribe a schedule for compliance 

(including increments of progress or 

measures to develop an alternative 

source of water supply) and 

implementation of appropriate control 

measures that the State requires the 

system to meet while the exemption is 

in effect. Under section 1416(b)(2)(A), 

the schedule prescribed shall require 

compliance as expeditiously as 

practicable (to be determined by the 

State), but no later than 3 years after the 

effective date for the regulations 

established pursuant to section 

1412(b)(10). For public water systems 

which do not serve more than a 

population of 3,300 and which need 

financial assistance for the necessary 

improvements, EPA or the State may 

renew an exemption for one or more 

additional two-year periods, but not to 

exceed a total of 6 years, if the system 

establishes that it is taking all 

practicable steps to meet the 

requirements above. A public water 

system shall not be granted an 

exemption unless it can establish that 

either: (1) the system cannot meet the 

standard without capital improvements 

that cannot be completed prior to the 

date established pursuant to section 

1412(b)(10); (2) in the case of a system 

that needs financial assistance for the 

necessary implementation, the system 

has entered into an agreement to obtain 

financial assistance pursuant to section 

1452 or any other Federal or state 

program; or (3) the system has entered 

into an enforceable agreement to 

become part of a regional public water 

system. 

3. Summary of Major Comments 

Several commenters agreed with the 

proposal not to list variances 

technologies for the Stage 2 DBPR. One 

commenter requested that EPA modify 

the methodology used to assess 

affordability. As mentioned earlier, EPA 

is currently reevaluating its nationallevel affordability criteria and has 

solicited recommendations from both 

the NDWAC and the SAB as part of this 

review. EPA intends to apply the 

revised criteria to the Stage 2 DBPR for 

the purpose of determining whether to 

enable States to give variances. 

L. Requirements for Systems to Use 

Qualified Operators 

EPA believes that systems that must 

make treatment changes to comply with 

requirements to reduce microbiological 

risks and risks from disinfectants and 

disinfection byproducts should be 

operated by personnel who are qualified 

to recognize and respond to problems. 

Subpart H systems were required to be 

operated by qualified operators under 

the SWTR (§ 141.70). The Stage 1 DBPR 

added requirements for all disinfected 

systems to be operated by qualified 

personnel who meet the requirements 

specified by the State, which may differ 

based on system size and type. The rule 

also requires that States maintain a 

register of qualified operators (40 CFR 

141.130(c)). While the Stage 2 DBPR 

requirements do not supercede or 

modify the requirement that disinfected 

systems be operated by qualified 

operators, such personnel play an 

important role in delivering drinking 

water that meets Stage 2 MCLs to the 

public. States should also review and 

modify, as required, their qualification 

standards to take into account new 

technologies (e.g., ultraviolet (UV) 

disinfection) and new compliance 

requirements (including simultaneous 

compliance and consecutive system 

requirements). EPA received only one 

comment on this topic; the commenter 

supported the need for a qualified 

operator. 

M. System Reporting and Recordkeeping 

Requirements 

1. Today’s Rule 

Today’s Stage 2 DBPR, consistent 

with the existing system reporting and 

recordkeeping regulations under 40 CFR 

141.134 (Stage 1 DBPR), requires public 

water systems (including consecutive 

systems) to report monitoring data to 

States within ten days after the end of 

the compliance period. In addition, 

systems are required to submit the data 

required in § 141.134. These data are 

required to be submitted quarterly for 

any monitoring conducted quarterly or 

more frequently, and within ten days of 

the end of the monitoring period for less 

frequent monitoring. As with other 

chemical analysis data, the system must 

keep the results for 10 years. 

In addition to the existing Stage 1 

reporting requirements, today’s rule 

requires systems to perform specific 

IDSE-related reporting to the primacy 

agency, except for systems serving fewer 

than 500 for which the State or primacy 

agency has waived this requirement. 

Required reporting includes submission 

of IDSE monitoring plans, 40/30 

certification, and IDSE reports. This 

reporting must be accomplished on the 

schedule specified in the rule (see 

§ 141.600(c)) and discussed in section 

IV.E of today’s preamble. System 

submissions must include the elements 

identified in subpart U and discussed 

further in section IV.F of today’s 

preamble. These elements include 

recommended Stage 2 compliance 

monitoring sites as part of the IDSE 

report. 

Systems must report compliance with 

Stage 2 TTHM and HAA5 MCLs (0.080 

mg/LTTHM and 0.060 mg/L HAA5, as 

LRAAs) according to the schedules 

specified in §§ 141.620 and 141.629 and 

discussed in section IV.E of today’s 

preamble. Reporting for DBP 

monitoring, as described previously, 

will remain generally consistent with 

current public water system reporting 

requirements (§ 141.31 and § 141.134); 

systems will be required to calculate 

and report each LRAA (instead of the 

system’s RAA) and each individual 

monitoring result (as required under the 

Stage 1 DBPR). Systems will also be 

required to provide a report to the State 

about each operational evaluation 

within 90 days, as discussed in section 

IV.H. Reports and evaluations must be 

kept for 10 years and may prove 

valuable in identifying trends and 

recurring issues. 

2. Summary of Major Comments 

EPA requested comment on all system 

reporting and recordkeeping 

requirements. Commenters generally 

supported EPA’s proposed 

requirements, but expressed concern 

about two specific issues. The first issue 

was the data management and tracking 

difficulties that States would face if EPA 

finalized a monitoring approach which 

had both plant-based and populationbased requirements, as was proposed. 

Since today’s rule contains only 

population-based monitoring 

requirements, this concern is no longer 

an issue. See section IV.G in today’s 

preamble for further discussion. 

The second concern related to 

reporting associated with the IDSE. 

Commenters who supported an 

approach other than the IDSE for 

determining Stage 2 compliance 

monitoring locations did not support 

IDSE-related reporting. The IDSE 

remains a key component of the final 

rule; thus, EPA has retained IDSErelated reporting. However, the Agency 

has modified both the content and the 

timing of the reporting to reduce the 

burden. See sections IV.F and IV.E, 

respectively, of today’s preamble for 

further discussion. 

N. Approval of Additional Analytical 

Methods 

1. Today’s Rule 

EPA is taking final action to: 

(1) allow the use of 13 methods 

published by the Standard Methods 

Committee in Standard Methods for the 

Examination of Water and Wastewater, 


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20th edition, 1998 (APHA 1998) and 12 

methods in Standard Methods Online. 

(2) approve three methods published 

by American Society for Testing and 

Materials International. 

(3) approve EPA Method 327.0 

Revision 1.1 (USEPA 2005h) for daily 

monitoring of chlorine dioxide and 

chlorite, EPA Method 552.3 (USEPA 

2003f) for haloacetic acids (five) 

(HAA5), EPA Methods 317.0 Revision 2 

(USEPA 2001c) and 326.0 (USEPA 2002) 

for bromate, chlorite, and bromide, EPA 

Method 321.8 (USEPA 2000g) for 

bromate only, and EPA Method 415.3 

Revision 1.1 (USEPA 2005l) for total 

organic carbon (TOC) and specific 

ultraviolet absorbance (SUVA). 

(4) update the citation for EPA 

Method 300.1 (USEPA 2000h) for 

bromate, chlorite, and bromide. 

(5) standardize the HAA5 sample 

holding times and the bromate sample 

preservation procedure and holding 

time. 

(6) add the requirement to remove 

inorganic carbon prior to determining 

TOC or DOC, remove the specification 

of type of acid used for TOC/DOC 

sample preservation; and require that 

TOC samples be preserved at the time 

of collection. 

(7) clarify which methods are 

approved for magnesium hardness 

determinations (40 CFR 141.131 and 

141.135). 

2. Background and Analysis 

The Stage 1 Disinfectants and 

Disinfection Byproducts Rule (Stage 1 

DBPR) was promulgated on December 

16, 1998 (USEPA 1998a) and it included 

approved analytical methods for DBPs, 

disinfectants, and DBP precursors. 

Additional analytical methods became 

available subsequent to the rule and 

were proposed in the Stage 2 

Disinfectants and Disinfection 

Byproducts Rule (Stage 2 DBPR) 

(USEPA 2003a). These methods are 

applicable to monitoring that is required 

under the Stage 1 DBPR. After the Stage 

2 DBPR proposal, analytical methods for 

additional drinking water contaminants 

were proposed for approval in a 

Methods Update Rule proposal (USEPA 

2004). The Stage 2 DBPR and Methods 

Update Rule proposals both included 

changes in the same sections of the CFR. 

EPA decided to make all the changes to 

§ 141.131 as part of the Stage 2 DBPR 

and the remainder of the methods that 

were proposed with the Stage 2 DBPR 

will be considered as part of the 

Methods Update Rule, which will be 

finalized at a later date. Two ASTM 

methods, D 1253–86(96) and D 1253–03, 

that were proposed in the Methods 

Update Rule, are being approved for 

measuring chlorine residual as part of 

today’s action. 

Minor corrections have been made in 

two of the methods that were proposed 

in the Stage 2 DBPR. In today’s rule, the 

Agency is approving EPA Method 327.0 

(Revision 1.1, 2005) which corrects 

three typographical errors in the 

proposed method. 

EPA is also approving EPA Method 

415.3 (Revision 1.1, 2005), which does 

not contain the requirement that 

samples for the analysis of TOC must be 

received within 48 hours of sample 

collection. 

A summary of the methods that are 

included in today’s rule is presented in 

Table IV.N–1. 

TABLE IV.N–1. ANALYTICAL METHODS APPROVED IN TODAY’S RULE

Analyte EPA method Standard methods 20th 

edition Standard methods online Other 

§ 141.131—Disinfection Byproducts 

HAA5 .................................. 552.3 ................................. 6251 B .............................. 6251 B–94 ........................

Bromate ............................. 317.0, Revision 2.0 ...........

321.8 .................................

326.0 .................................

........................................... ........................................... ASTM D 6581–00 

Chlorite (monthly or daily) 317.0, Revision 2.0 ...........

326.0 .................................

........................................... ........................................... ASTM D 6581–00 

Chlorite (daily) .................... 327.0, Revision 1.1 ........... 4500–ClO2 E ..................... 4500–ClO2 E–00 ...............

§ 141.131—Disinfectants 

Chlorine (free, combined, 

total).

........................................... 4500–Cl D .........................

4500–Cl F .........................

4500–Cl G .........................

4500–Cl D–00 ...................

4500–Cl F–00 ...................

4500–Cl G–00 ...................

ASTM D 1253–86(96) 

ASTM D 1253–03 

Chlorine (total) ................... ........................................... 4500–Cl E .........................

4500–Cl I ..........................

4500–Cl E–00 ...................

4500–Cl I–00 ....................

Chlorine (free) .................... ........................................... 4500–Cl H ......................... 4500–Cl H–00 ...................

Chlorine Dioxide ................ 327.0, Revision 1.1 ........... 4500–ClO2 D .....................

4500–ClO2 E .....................

4500–ClO2 E–00 ...............

§ 141.131—Other parameters 

Bromide .............................. 317.0, Revision 2.0 ...........

326.0 .................................

........................................... ........................................... ASTM D 6581–00 

TOC/DOC .......................... 415.3, Revision 1.1 ........... 5310 B ..............................

5310 C ..............................

5310 D ..............................

5310 B–00 ........................

5310 C–00 ........................

5310 D–00 ........................

UV254 .................................. 415.3, Revision 1.1 ........... 5910 B .............................. 5910 B–00 ........................

SUVA ................................. 415.3, Revision 1.1 ........... ........................................... ...........................................


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O. Laboratory Certification and 

Approval 

1. PE Acceptance Criteria 

a. Today’s rule. Today’s rule 

maintains the requirements of 

laboratory certification for laboratories 

performing analyses to demonstrate 

compliance with MCLs and all other 

analyses to be conducted by approved 

parties. It revises the acceptance criteria 

for performance evaluation (PE) studies 

which laboratories must pass as part of 

the certification program. The new 

acceptance limits are effective 60 days 

after promulgation. Laboratories that 

were certified under the Stage 1 DBPR 

PE acceptance criteria will be subject to 

the new criteria when it is time for them 

to analyze their annual DBP PE 

sample(s). Today’s rule also requires 

that TTHM and HAA5 analyses that are 

performed for the IDSE or systemspecific study be conducted by 

laboratories certified for those analyses. 

TABLE IV.O–1.—PERFORMANCE EVALUATION (PE) ACCEPTANCE CRITERIA

DBP 

Acceptance 

limits (percent of true 

value) 

Comments 

TTHM 

Chloroform ............................................................................. ±20 Laboratory must meet all 4 individual THM acceptance limits in 

order to successfully pass a PE sample for TTHM 

Bromodichloromethane ......................................................... ±20 

Dibromochloromethane ......................................................... ±20 

Bromoform ............................................................................. ±20 

HAA5 

Monochloroacetic Acid .......................................................... ±40 Laboratory must meet the acceptance limits for 4 out of 5 of the 

HAA5 compounds in order to successfully pass a PE sample 

for HAA5 

Dichloroacetic Acid ................................................................ ±40 

Trichloroacetic Acid ............................................................... ±40 

Monobromoacetic Acid .......................................................... ±40 

Dibromoacetic Acid ............................................................... ±40 

Chlorite ......................................................................................... ±30 

Bromate ........................................................................................ ±30 

b. Background and analysis. The Stage 

1 DBPR (USEPA 1998a) specified that in 

order to be certified the laboratory must 

pass an annual performance evaluation 

(PE) sample approved by EPA or the 

State using each method for which the 

laboratory wishes to maintain 

certification. The acceptance criteria for 

the DBP PE samples were set as 

statistical limits based on the 

performance of the laboratories in each 

study. This was done because EPA did 

not have enough data to specify fixed 

acceptance limits. 

Subsequent to promulgation of the 

Stage 1 DBPR, EPA was able to evaluate 

data from PE studies conducted during 

the Information Collection Rule (USEPA 

1996) and during the last five general 

Water Supply PE studies. Based on the 

evaluation process as described in the 

proposed Stage 2 DBPR (USEPA 2003a), 

EPA determined that fixed acceptance 

limits could be established for the DBPs. 

Today’s action replaces the statistical PE 

acceptance limits with fixed limits 

effective one year after promulgation. 

c. Summary of major comments. Four 

commenters supported the fixed 

acceptance criteria as presented in the 

proposed rule. One requested that a 

minimum concentration be set for each 

DBP in the PE studies, so that 

laboratories would not be required to 

meet tighter criteria in the PE study than 

they are required to meet with the 

minimum reporting level (MRL) check 

standard. EPA has addressed this 

concern by directing the PE sample 

suppliers to use concentrations no less 

than 10 μg/L for the individual THM 

and HAAs, 100 μg/L for chlorite, and 7 

μg/L for bromate in PE studies used for 

certifying drinking water laboratories. 

Two commenters requested that the 

effective date for the new PE acceptance 

criteria be extended from 60 days to 180 

days, because they felt that 60 days was 

not enough time for laboratories to meet 

the new criteria. EPA realized from 

those comments that the original intent 

of the proposal was not clearly 

explained; the 60 days was to be the 

deadline for when the PE providers 

must change the acceptance criteria that 

are used when the studies are 

conducted. Laboratories would have to 

meet the criteria when it is time for 

them to analyze their annual PE samples 

in order to maintain certification. 

Depending upon when the last PE 

sample was analyzed, laboratories could 

have up to one year to meet the new 

criteria. In order to eliminate this 

confusion, EPA has modified the rule 

language to allow laboratories one year 

from today’s date to meet the new PE 

criteria. 

2. Minimum Reporting Limits 

a. Today’s rule. EPA is establishing 

regulatory minimum reporting limits 

(MRLs) for compliance reporting of 

DBPs by Public Water Systems. These 

regulatory MRLs (Table IV.O–2) also 

define the minimum concentrations that 

must be reported as part of the 

Consumer Confidence Reports (40 CFR 

§ 141.151(d)). EPA is incorporating 

MRLs into the laboratory certification 

program for DBPs by requiring 

laboratories to include a standard near 

the MRL concentration as part of the 

calibration curve for each DBP and to 

verify the accuracy of the calibration 

curve at the MRL concentration by 

analyzing an MRL check standard with 

a concentration less than or equal to 

110% of the MRL with each batch of 

samples. The measured DBP 

concentration for the MRL check 

standard must be ±50% of the expected 

value, if any field sample in the batch 

has a concentration less than 5 times the 

regulatory MRL. 


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TABLE IV.O–2.—REGULATORY MINIMUM REPORTING LEVELS

DBP Minimum reporting level 

(mg/L) 1 Comments 

TTHM 2

Chloroform ...................................................... 0.0010 

Bromodichloromethane .................................. 0.0010 

Dibromochloromethane .................................. 0.0010 

Bromoform ...................................................... 0.0010 

HAA5 2

Monochloroacetic Acid ................................... 0.0020 

Dichloroacetic Acid ......................................... 0.0010 

Trichloroacetic Acid ........................................ 0.0010 

Monobromoacetic Acid ................................... 0.0010 

Dibromoacetic Acid ........................................ 0.0010 

Chlorite .................................................................. 0.020 Applicable to monitoring as prescribed in § 141.132(b)(2)(i)(B) 

and (b)(2)(ii). 

Bromate ................................................................. 0.0050 or 0.0010 Laboratories that use EPA Methods 317.0 Revision 2.0, 326.0 or 

321.8 must meet a 0.0010 mg/L MRL for bromate. 

1The calibration curve must encompass the regulatory minimum reporting level (MRL) concentration. Data may be reported for concentrations 

lower than the regulatory MRL as long as the precision and accuracy criteria are met by analyzing an MRL check standard at the lowest reporting limit chosen by the laboratory. The laboratory must verify the accuracy of the calibration curve at the MRL concentration by analyzing an 

MRL check standard with a concentration less than or equal to 110% of the MRL with each batch of samples. The measured concentration for 

the MRL check standard must be ±50% of the expected value, if any field sample in the batch has a concentration less than 5 times the regulatory MRL. Method requirements to analyze higher concentration check standards and meet tighter acceptance criteria for them must be met in 

addition to the MRL check standard requirement. 2When adding the individual trihalomethane or haloacetic acid concentrations to calculate the TTHM or HAA5 concentrations, respectively, a 

zero is used for any analytical result that is less than the MRL concentration for that DBP, unless otherwise specified by the State. 

b. Background and analysis. EPA 

proposed to establish regulatory MRLs 

for DBPs in order to define expectations 

for reporting compliance monitoring 

data to the Primacy Agencies and in the 

Consumer Confidence Reports. The 

proposed MRLs were generally based on 

those used during the Information 

Collection Rule (USEPA 1996), because 

an analysis of the quality control data 

set from the Information Collection Rule 

(Fair et al. 2002) indicated that 

laboratories are able to provide 

quantitative data down to those 

concentrations. 

EPA also proposed that laboratories 

be required to demonstrate ability to 

quantitate at the MRL concentrations by 

analyzing an MRL check standard and 

meeting accuracy criteria on each day 

that compliance samples are analyzed. 

Three public commenters noted that 

meeting the accuracy requirement for 

the MRL check standard did not 

contribute to the quality of the data in 

cases in which the concentration of a 

DBP in the samples was much higher 

than the MRL. For example, if 

chloroform concentrations are always 

greater than 0.040 mg/L in a water 

system’s samples, then verifying 

accurate quantitation at 0.0010 mg/L is 

unnecessary and may require the 

laboratory to dilute samples or maintain 

two calibration curves in order to 

comply with the requirement. EPA has 

taken this into consideration in today’s 

rule and has adjusted the requirement 

accordingly. EPA is maintaining the 

requirement for all laboratories to 

analyze the MRL check standard, but 

the laboratory is only required to meet 

the accuracy criteria (±50%) if a field 

sample has a concentration less than 

five times the regulatory MRL 

concentration. 

EPA proposed a regulatory MRL of 

0.200 mg/L for chlorite, because data 

from the Information Collection Rule 

indicated that most samples would 

contain concentrations greater than 

0.200 mg/L (USEPA 2003c). EPA also 

took comment on a lower MRL of 0.020 

mg/L. Commenters were evenly divided 

concerning which regulatory MRL 

concentration should be adopted in the 

final rule. EPA has decided to set the 

chlorite regulatory MRL at 0.020 mg/L 

in today’s rule. This decision was based 

on two factors. First, the approved 

analytical methods for determining 

compliance with the chlorite MCL can 

easily support an MRL of 0.020 mg/L. 

More importantly, since the proposal, 

EPA has learned that water systems that 

have low chlorite concentrations in 

their water have been obtaining data on 

these low concentrations from their 

laboratories and have been using these 

data in their Consumer Confidence 

Reports. Setting the MRL at 0.020 mg/ 

L is reflective of current practices in 

laboratories and current data 

expectations by water systems. 

c. Summary of major comments. 

There were no major comments. 

P. Other Regulatory Changes 

As part of today’s action, EPA has 

included several ‘‘housekeeping’’

actions to remove sections of Part 141 

that are no longer effective. These 

sections have been superceded by new 

requirements elsewhere in Part 141. 

Sections 141.12 (Maximum 

contaminant levels for total 

trihalomethanes) and 141.30 (Total 

trihalomethanes sampling, analytical 

and other requirements) were 

promulgated as part of the 1979 TTHM 

Rule. These sections have been 

superceded in their entirety by § 141.64 

(Maximum contaminant levels for 

disinfection byproducts) and subpart L 

(Disinfectant Residuals, Disinfection 

Byproducts, and Disinfection Byproduct 

Precursors), respectively, as of 

December 31, 2003. Also, § 141.32 

(Public notification) has been 

superceded by subpart Q (Public 

Notification of Drinking Water 

Violations), which is now fully in effect. 

Section 553 of the Administrative 

Procedure Act, 5 U.S.C. 553(b)(B), 

provides that, when an agency for good 

cause finds that notice and public 

procedure are impracticable, 

unnecessary, or contrary to the public 

interest, the agency may issue a rule 

without providing prior notice and an 

opportunity for public comment. In 

addition to updating methods, this rule 

also makes minor corrections to the 

National Primary Drinking Water 

Regulations, specifically the Public 

Notification tables (Subpart Q, 

Appendices A and B). Two final 

drinking water rules (66 FR 6976 and 65 

FR 76708) inadvertently added new 

endnotes to two existing tables using the 

same endnote numbers. This rule 

corrects this technical drafting error by 


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renumbering the endnote citations in 

these two tables. Thus, additional notice 

and public comment is not necessary. 

EPA finds that this constitutes ‘‘good 

cause’’ under 5 U.S.C. 553(b)(B). For the 

same reasons, EPA is making this rule 

change effective upon publication. 5 

U.S.C. 553(d)(3). 

V. State Implementation 

A. Today’s Rule 

This section describes the regulations 

and other procedures and policies States 

must adopt to implement today’s rule. 

States must continue to meet all other 

conditions of primacy in 40 CFR Part 

142. To implement the Stage 2 DBPR, 

States must adopt revisions to the 

following: 

—§ 141.2—Definitions 

—§ 141.33—Record maintenance; 

—§ 141.64—Maximum contaminant 

levels for disinfection byproducts; 

—subpart L—Disinfectant Residuals, 

Disinfection Byproducts, and 

Disinfection Byproduct Precursors; 

—subpart O, Consumer Confidence 

Reports; 

—subpart Q, Public Notification of 

Drinking Water Violations; 

—new subpart U, Initial Distribution 

System Evaluation; and 

—new subpart V, Stage 2 Disinfection 

Byproducts Requirements. 

1. State Primacy Requirements for 

Implementation Flexibility 

In addition to adopting basic primacy 

requirements specified in 40 CFR part 

142, States are required to address 

applicable special primacy conditions. 

Special primacy conditions pertain to 

specific regulations where 

implementation of the rule involves 

activities beyond general primacy 

provisions. The purpose of these special 

primacy requirements in today’s rule is 

to ensure State flexibility in 

implementing a regulation that (1) 

applies to specific system configurations 

within the particular State and (2) can 

be integrated with a State’s existing 

Public Water Supply Supervision 

Program. States must include these ruledistinct provisions in an application for 

approval or revision of their program. 

These primacy requirements for 

implementation flexibility are discussed 

in this section. 

To ensure that a State program 

includes all the elements necessary for 

an effective and enforceable program 

under today’s rule, a State primacy 

application must include a description 

of how the State will implement a 

procedure for modifying consecutive 

system and wholesale system 

monitoring requirements on a case-bycase basis, if a State will use the 

authority to modify monitoring 

requirements under this special primacy 

condition. 

2. State Recordkeeping Requirements 

Today’s rule requires States to keep 

additional records of the following, 

including all supporting information 

and an explanation of the technical 

basis for each decision: 

—very small system waivers. 

—IDSE monitoring plans. 

—IDSE reports and 40/30 

certifications, plus any 

modifications required by the State. 

—operational evaluations conducted 

by the system. 

3. State Reporting Requirements 

Today’s rule has no new State 

reporting requirements. 

4. Interim Primacy 

States that have primacy for every 

existing NPDWR already in effect may 

obtain interim primacy for this rule, 

beginning on the date that the State 

submits the application for this rule to 

USEPA, or the effective date of its 

revised regulations, whichever is later. 

A State that wishes to obtain interim 

primacy for future NPDWRs must obtain 

primacy for today’s rule. As described 

in Section IV.F, EPA expects to work 

with States to oversee the individual 

distribution system evaluation process 

that begins shortly after rule 

promulgation. 

5. IDSE Implementation 

As discussed in section IV.E, many 

systems will be performing certain IDSE 

activities prior to their State receiving 

primacy. During that period, EPA will 

act as the primacy agency, but will 

consult and coordinate with individual 

States to the extent practicable and to 

the extent that States are willing and 

able to do so. In addition, prior to 

primacy, States may be asked to assist 

EPA in identifying and confirming 

systems that are required to comply 

with certain IDSE activities. Once the 

State has received primacy, it will 

become responsible for IDSE 

implementation activities. 

B. Background and Analysis 

SDWA establishes requirements that a 

State or eligible Indian Tribe must meet 

to assume and maintain primary 

enforcement responsibility (primacy) for 

its PWSs. These requirements include 

the following activities: (1) Adopting 

drinking water regulations that are no 

less stringent than Federal drinking 

water regulations; (2) adopting and 

implementing adequate procedures for 

enforcement; (3) keeping records and 

making reports available on activities 

that EPA requires by regulation; (4) 

issuing variances and exemptions (if 

allowed by the State), under conditions 

no less stringent than allowed under 

SDWA; and (5) adopting and being 

capable of implementing an adequate 

plan for the provisions of safe drinking 

water under emergency situations. 

40 CFR part 142 sets out the specific 

program implementation requirements 

for States to obtain primacy for the 

public water supply supervision 

program as authorized under SDWA 

section 1413. In addition to adopting 

basic primacy requirements specified in 

40 CFR Part 142, States may be required 

to adopt special primacy provisions 

pertaining to specific regulations where 

implementation of the rule involves 

activities beyond general primacy 

provisions. States must include these 

regulation specific provisions in an 

application for approval of their 

program revision. 

The current regulations in 40 CFR 

142.14 require States with primacy to 

keep various records, including the 

following: analytical results to 

determine compliance with MCLs, 

MRDLs, and treatment technique 

requirements; PWS inventories; State 

approvals; enforcement actions; and the 

issuance of variances and exemptions. 

Today’s final rule requires States to 

keep additional records, including all 

supporting information and an 

explanation of the technical basis for 

decisions made by the State regarding 

today’s rule requirements. The State 

may use these records to identify trends 

and determine whether to limit the 

scope of operational evaluations. EPA 

currently requires in 40 CFR 142.15 that 

States report to EPA information such as 

violations, variance and exemption 

status, and enforcement actions; today’s 

rule does not add additional reporting 

requirements or modify existing 

requirements. 

On April 28, 1998, EPA amended its 

State primacy regulations at 40 CFR 

142.12 to incorporate the new process 

identified in the 1996 SDWA 

Amendments for granting primary 

enforcement authority to States while 

their applications to modify their 

primacy programs are under review (63 

FR 23362, April 28, 1998) (USEPA 

1998f). The new process grants interim 

primary enforcement authority for a 

new or revised regulation during the 

period in which EPA is making a 

determination with regard to primacy 

for that new or revised regulation. This 

interim enforcement authority begins on 

the date of the primacy application 

submission or the effective date of the 


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new or revised State regulation, 

whichever is later, and ends when EPA 

makes a final determination. However, 

this interim primacy authority is only 

available to a State that has primacy 

(including interim primacy) for every 

existing NPDWR in effect when the new 

regulation is promulgated. States that 

have primacy for every existing NPDWR 

already in effect may obtain interim 

primacy for this rule and a State that 

wishes to obtain interim primacy for 

future NPDWRs must obtain primacy for 

this rule. 

EPA is aware that due to the 

complicated wholesale systemconsecutive system relationships that 

exist nationally, there will be cases 

where the standard monitoring 

framework will be difficult to 

implement. Therefore, States may 

develop, as a special primacy condition, 

a program under which the State can 

modify monitoring requirements for 

consecutive systems. These 

modifications must not undermine 

public health protection and all 

systems, including consecutive systems, 

must comply with the TTHM and HAA5 

MCLs based on the LRAA at each 

compliance monitoring location. Each 

consecutive system must have at least 

one compliance monitoring location. 

However, such a program allows the 

State to establish monitoring 

requirements that account for 

complicated distribution system 

relationships, such as where 

neighboring systems buy from and sell 

to each other regularly throughout the 

year, water passes through multiple 

consecutive systems before it reaches a 

user, or a large group of interconnected 

systems have a complicated combined 

distribution system. EPA has developed 

a guidance manual to address these and 

other consecutive system issues. 

C. Summary of Major Comments 

Public comment generally supported 

the special primacy requirements in the 

August 11, 2003 proposal, and many 

commenters expressed appreciation for 

the flexibility the special primacy 

requirements provided to States. 

Many commenters expressed concern 

about EPA as the implementer instead 

of the State, given the existing 

relationship between the State and 

system. EPA agrees that States perform 

an essential role in rule implementation 

and intends to work with States to the 

greatest extent possible, consistent with 

the rule schedule promulgated today. 

EPA believes that pre-promulgation 

coordination with States, changes in the 

final rule strongly supported by States 

(e.g., population-based monitoring 

instead of plant-based monitoring), and 

the staggered rule schedule will 

facilitate State involvement in preprimacy implementation. 

Many commenters also requested that 

the State have more flexibility to grant 

sampling waivers and exemptions. EPA 

believes that it has struck a reasonable 

balance among competing objectives in 

granting State flexibility. State 

flexibility comes at a resource cost and 

excessive system-by-system flexibility 

could overwhelm State resources. Also, 

EPA believes that much of the 

monitoring and water quality 

information a State would need to 

properly consider whether a waiver is 

appropriate is generally not available 

and, if available, difficult to evaluate. 

VI. Economic Analysis 

This section summarizes the 

Economic Analysis for the Final Stage 2 

Disinfectants and Disinfection 

Byproducts Rule (Economic Analysis 

(EA)) (USEPA 2005a). The EA is an 

evaluation of the benefits and costs of 

today’s final rule and other regulatory 

alternatives the Agency considered. 

Specifically, this evaluation addresses 

both quantified and non-quantified 

benefits to PWS consumers, including 

the general population and sensitive 

subpopulations. Costs are presented for 

PWSs, States, and consumer 

households. Also included is a 

discussion of potential risks from other 

contaminants, uncertainties in benefit 

and cost estimates, and a summary of 

major comments on the EA for the 

proposed Stage 2 DBPR. 

EPA relied on data from several 

epidemiologic and toxicologic studies, 

the Information Collection Rule (ICR), 

and other sources, along with analytical 

models and input from technical 

experts, to understand DBP risk, 

occurrence, and PWS treatment changes 

that will result from today’s rule. 

Benefits and costs are presented as 

annualized values using social discount 

rates of three and seven percent. The 

time frame used for benefit and cost 

comparisons is 25 years—approximately 

five years account for rule 

implementation and 20 years for the 

average useful life of treatment 

technologies. 

EPA has prepared this EA to comply 

with the requirements of SDWA, 

including the Health Risk Reduction 

and Cost Analysis required by SDWA 

section 1412(b)(3)(C), and Executive 

Order 12866, Regulatory Planning and 

Review. The full EA is available in the 

docket for today’s rule, which is 

available online as described in the 

ADDRESSES section. The full document 

provides detailed explanations of the 

analyses summarized in this section and 

additional analytical results. 

A. Regulatory Alternatives Considered 

The Stage 2 DBPR is the second in a 

set of rules that address public health 

risks from DBPs. EPA promulgated the 

Stage 1 DBPR to decrease average 

exposure to DBPs and mitigate 

associated health risks—compliance 

with TTHM and HAA5 MCLs is based 

on averaging concentrations across the 

distribution system. In developing the 

Stage 2 DBPR, EPA sought to identify 

and further reduce remaining risks from 

exposure to chlorinated DBPs. 

The regulatory options EPA 

considered for the Stage 2 DBPR are the 

direct result of a consensus rulemaking 

process (Federal Advisory Committee 

Act (FACA) process) that involved 

various drinking water stakeholders (see 

Section III for a description of the FACA 

process). The Advisory Committee 

considered the following key questions 

during the negotiation process for the 

Stage 2 DBPR: 

• What are the remaining health risks 

after implementation of the Stage 1 

DBPR? 

• What are approaches to addressing 

these risks? 

• What are the risk tradeoffs that need 

to be considered in evaluating these 

approaches? 

• How do the estimated costs of an 

approach compare to reductions in peak 

DBP occurrences and overall DBP 

exposure for that approach? 

The Advisory Committee considered 

DBP occurrence estimates to be 

important in understanding the nature 

of public health risks. Although the ICR 

data were collected prior to 

promulgation of the Stage 1 DBPR, they 

were collected under a similar sampling 

strategy. The data support the concept 

that a system could be in compliance 

with the RAA Stage 1 DBPR MCLs of 

0.080 mg/L and 0.060 mg/L for TTHM 

and HAA5, respectively, and yet have 

points in the distribution system with 

either periodically or consistently 

higher DBP levels. 

Based on these findings, the Advisory 

Committee discussed an array of 

alternatives to address disproportionate 

risk within distribution systems. 

Alternative options included lowering 

DBP MCLs, revising the method for 

MCL compliance determination e.g., 

requiring individual sampling locations 

to meet the MCL as an LRAA or 

requiring that no samples exceed the 

MCL), and combinations of both. The 

Advisory Committee also considered the 

associated technology changes and costs 

for these alternatives. After narrowing 

down options, the Advisory Committee 


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primarily focused on four types of 

alternative MCL scenarios. These are the 

alternatives EPA evaluated in the EA, as 

follows: 

Preferred Alternative 

—MCLs of 0.080 mg/L for TTHM and 

0.060 mg/L for HAA5 as LRAAs 

—Bromate MCL remaining at 0.010 

mg/L 

Alternative 1 

—MCLs of 0.080 mg/L for TTHM and 

0.060 mg/L for HAA5 as LRAAs 

—Bromate MCL of 0.005 mg/L 

Alternative 2 

—MCLs of 0.080 mg/L for TTHM and 

0.060 mg/L for HAA5 as absolute 

maximums for individual 

measurements 

—Bromate MCL remaining at 0.010 

mg/L 

Alternative 3 

—MCLs of 0.040 mg/L for TTHM and 

0.030 mg/L for HAA5 as RAAs 

—Bromate MCL remaining at 0.010 

mg/L. 

Figure VI.A–1 shows how compliance 

would be determined under each of the 

TTHM/HAA5 alternatives described and 

the Stage 1 DBPR for a hypothetical 

large surface water system. This 

hypothetical system has one treatment 

plant and measures TTHM in the 

distribution system in four locations per 

quarter (the calculation methodology 

shown would be the same for HAA5). 

Ultimately, the Advisory Committee 

recommended the Preferred Alternative 

in combination with an IDSE 

requirement (discussed in Section IV.F). 


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B. Analyses That Support Today’s Final 

Rule 

EPA’s goals in designing the Stage 2 

DBPR were to protect public health by 

reducing peak DBP levels in the 

distribution system while maintaining 

microbial protection. As described 

earlier, the Stage 1 DBPR reduces 

overall average DBP levels, but specific 

locations within distribution systems 

can still experience relatively high DBP 

concentrations. EPA believes that high 

DBP concentrations should be reduced 

due to the potential association of DBPs 

with cancer, as well as reproductive and 

developmental health effects. 

EPA analyzed the benefits and costs 

of the four regulatory alternatives 

presented in the previous section. 

Consistent with the recommendations of 

the Advisory Committee, EPA is 

establishing the preferred alternative to 

achieve the Agency’s goals for the Stage 

2 DBPR. The following discussion 

summarizes EPA’s analyses that support 

today’s final rule. This discussion 

explains how EPA predicted water 

quality and treatment changes, 

estimated benefits and costs, and 

assessed the regulatory alternatives. 

1. Predicting Water Quality and 

Treatment Changes 

Water quality and treatment data from 

the ICR were used in predicting 

treatment plant technology changes (i.e. 

compliance forecasts) and reductions in 

DBP exposure resulting from the Stage 

2 DBPR. Because ICR data were gathered 

prior to Stage 1 DBPR compliance 

deadlines, EPA first accounted for 

treatment changes resulting from the 

Stage 1 DBPR. Benefit and cost 

estimates for the Stage 2 DBPR reflect 

changes following compliance with the 

Stage 1 DBPR. 

The primary model used to predict 

changes in treatment and reductions in 

DBP levels was the Surface Water 

Analytical Tool (SWAT), which EPA 

developed using results from the ICR. 

SWAT results were applied directly for 

large and medium surface water systems 

and were adjusted for small surface 

water systems to account for differences 

in source water DBP precursor levels 

and operational constraints in small 

systems. EPA used ICR data and a 

Delphi poll process (a group of drinking 

water experts who provided best 

professional judgment in a structured 

format) to project technologies selected 

by ground water systems. 

To address uncertainty in SWAT 

predictions, EPA also predicted 

treatment changes using a second 

methodology, called the ‘‘ICR Matrix 

Method.’’ Rather than a SWATpredicted pre-Stage 1 baseline, the ICR 

Matrix Method uses unadjusted ICR 

TTHM and HAA5 pre-Stage 1 data to 

estimate the percent of plants changing 

technology to comply with the Stage 2 

DBPR. EPA gives equal weight to SWAT 

and ICR Matrix Method predictions in 

estimating Stage 2 compliance forecasts 

and resultant reductions in DBP 

exposure. The ICR Matrix Method is 

also used to estimate reductions in the 

occurrence of peak TTHM and HAA5 

concentrations because SWATpredicted TTHM and HAA5 

concentrations are valid only when 

considering national averages, not at the 

plant level. 

When evaluating compliance with a 

DBP MCL, EPA assumed that systems 

would maintain DBP levels at least 20 

percent below the MCL. This safety 

margin represents the level at which 

systems typically take action to ensure 

they meet a drinking water standard and 

reflects industry practice. In addition, 

the safety margin accounts for year-toyear fluctuations in DBP levels. To 

address the impact of the IDSE, EPA 

also analyzed compliance using a safety 

margin of 25 percent based on an 

analysis of spatial variability in TTHM 

and HAA5 occurrence. EPA assigned 

equal probability to the 20 and 25 

percent safety margin for large and 

medium surface water systems for the 

final analysis because both alternatives 

are considered equally plausible. EPA 

assumes the 20 percent operational 

safety margin accounts for variability in 

small surface water systems and all 

groundwater systems. 

2. Estimating Benefits 

Quantified benefits estimates for the 

Stage 2 DBPR are based on potential 

reductions in fatal and non-fatal bladder 

cancer cases. In the EA, EPA included 

a sensitivity analysis for benefits from 

avoiding colon and rectal cancers. EPA 

believes additional benefits from this 

rule could come from reducing potential 

reproductive and developmental risks. 

EPA has not included these potential 

risks in the primary benefit analysis 

because of the associated uncertainty. 

The major steps in deriving and 

characterizing potential cancer cases 

avoided include the following: (1) 

estimate the current and future annual 

cases of illness from all causes; (2) 

estimate how many cases can be 

attributed to DBP occurrence and 

exposure; and (3) estimate the reduction 

in future cases corresponding to 

anticipated reductions in DBP 

occurrence and exposure due to the 

Stage 2 DBPR. 

EPA used results from the National 

Cancer Institute’s Surveillance, 

Epidemiology, and End Results program 

in conjunction with data from the 2000 

U.S. Census to estimate the number of 

new bladder cancer cases per year 

(USEPA 2005a). Three approaches were 

then used to gauge the percentage of 

cases attributable to DBP exposure (i.e., 

population attributable risk (PAR)). 

Taken together, the three approaches 

provide a reasonable estimate of the 

range of potential risks. EPA notes that 

the existing epidemiological evidence 

has not conclusively established 

causality between DBP exposure and 

any health risk endpoints, so the lower 

bound of potential risks may be as low 

as zero. 

The first approach used the range of 

PAR values derived from consideration 

of five individual epidemiology studies. 

This range was used at the basis for the 

Stage 1 and the proposed Stage 2 

economic analyses (i.e., 2 percent to 17 

percent) (USEPA 2003a). 

The second approach used results 

from the Villanueva et al. (2003) metaanalysis. This study develops a 

combined Odds Ratio (OR) of 1.2 that 

reflects the ever-exposed category for 

both sexes from all studies considered 

in the meta-analysis and yields a PAR 

value of approximately 16 percent. 

The third approach used the 

Villanueva et al. (2004) pooled data 

analysis to develop a dose-response 

relationship for OR as a function of 

average TTHM exposure. Using the 

results from this approach, EPA 

estimates a PAR value of approximately 

17 percent. 

EPA used the PAR values from all 

three approaches to estimate the number 

of bladder cancer cases ultimately 

avoided annually as a result of the Stage 

2 DBPR. To quantify the reduction in 

cases, EPA assumed a linear 

relationship between average DBP 

concentration and relative risk of 

bladder cancer. Because of this, EPA 

considers these estimates to be an upper 

bound on the annual reduction in 

bladder cancer cases due to the rule. 

A lag period (i.e., cessation lag) exists 

between when reduction in exposure to 

a carcinogen occurs and when the full 

risk reduction benefit of that exposure 

reduction is realized by exposed 

individuals. No data are available that 

address the rate of achieving bladder 

cancer benefits resulting from DBP 

reductions. Consequently, EPA used 

data from epidemiological studies that 

address exposure reduction to cigarette 

smoke and arsenic to generate three 

possible cessation lag functions for 

bladder cancer and DBPs. The cessation 

lag functions are used in conjunction 


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with the rule implementation schedule 

to project the number of bladder cancer 

cases avoided each year as a result of 

the Stage 2 DBPR. 

Although EPA used three approaches 

for estimating PAR, for simplicity’s 

sake, EPA used the Villanueva et al. 

(2003) study to calculate the annual 

benefits of the Stage 2 DBPR. The 

benefits estimates derived from 

Villanueva et al. (2003) capture a 

substantial portion of the overall range 

of results, reflecting the uncertainty in 

both the underlying OR and PAR values, 

as well as the uncertainty in DBP 

reductions for Stage 2. 

To assign a monetary value to avoided 

bladder cancer cases, EPA used the 

value of a statistical life (VSL) for fatal 

cases and used two alternate estimates 

of willingness-to-pay to avoid non-fatal 

cases (one based on curable lymphoma 

and the other based on chronic 

bronchitis). EPA believes additional 

benefits from this rule could come from 

a reduction in potential reproductive 

and developmental risks. See Chapter 6 

of the EA for more information on 

estimating benefits (USEPA 2005a). 

3. Estimating Costs 

Analyzing costs for systems to comply 

with the Stage 2 DBPR included 

identifying and costing treatment 

process improvements that systems will 

make, as well as estimating the costs to 

implement the rule, conduct IDSEs, 

prepare monitoring plans, perform 

additional routine monitoring, and 

evaluate significant DBP excursion 

events. The cost analysis for States/ 

Primacy Agencies included estimates of 

the labor burdens for training employees 

on the requirements of the Stage 2 

DBPR, responding to PWS reports, and 

record keeping. 

All treatment costs are based on mean 

unit cost estimates for advanced 

technologies and chloramines. 

Derivation of unit costs are described in 

detail in Technologies and Costs for the 

Final Long Term 2 Enhanced Surface 

Water Treatment Rule and Final Stage 2 

Disinfectants and Disinfection 

Byproducts Rule (USEPA 2005g). Unit 

costs (capital and O&M) for each of nine 

system size categories are calculated 

using mean design and average daily 

flows values. The unit costs are then 

combined with the predicted number of 

plants selecting each technology to 

produce national treatment cost 

estimates. 

Non-treatment costs for 

implementation, the IDSE, monitoring 

plans, additional routine monitoring, 

and operational evaluations are based 

on estimates of labor hours for 

performing these activities and on 

laboratory costs. 

While systems vary with respect to 

many of the input parameters to the 

Stage 2 DBPR cost analysis (e.g., plants 

per system, population served, flow per 

population, labor rates), EPA believes 

that mean values for the various input 

parameters are appropriate to generate 

the best estimate of national costs for 

the rule. Uncertainty in the national 

average unit capital and O&M costs for 

the various technologies has been 

incorporated into the cost analysis 

(using Monte Carlo simulation 

procedures). Costs of the Stage 2 DBPR 

are estimated at both mean and 90 

percent confidence bound values. 

EPA assumes that systems will, to the 

extent possible, pass cost increases on to 

their customers through increases in 

water rates. Consequently, EPA has also 

estimated annual household cost 

increases for the Stage 2 DBPR. This 

analysis includes costs for all 

households served by systems subject to 

the rule, costs just for those households 

served by systems actually changing 

treatment technologies to comply with 

the rule, costs for households served by 

small systems, and costs for systems 

served by surface water and ground 

water sources. 

4. Comparing Regulatory Alternatives 

Through the analyses summarized in 

this section, EPA assessed the benefits 

and costs of the four regulatory 

alternatives described previously. 

Succeeding sections of this preamble 

present the results of these analyses. As 

recommended by the Advisory 

Committee, EPA is establishing the 

preferred regulatory alternative for 

today’s Stage 2 DBPR. This regulation 

will reduce peak DBP concentrations in 

distribution systems through requiring 

compliance determinations with 

existing TTHM and HAA5 MCLs using 

the LRAA. Further, the IDSE will ensure 

that systems identify compliance 

monitoring sites that reflect high DBP 

levels. EPA believes that these provision 

are appropriate given the association of 

DBPs with cancer, as well as potential 

reproductive and developmental health 

effects. 

Alternative 1 would have established 

the same DBP regulations as the 

preferred alternative, and would have 

lowered the bromate MCL from 0.010 to 

0.005 mg/L. The Advisory Committee 

did not recommend and EPA did not 

establish this alternative because it 

could have an adverse effect on 

microbial protection. The lower bromate 

MCL could cause many systems to 

reduce or eliminate the use of ozone, 

which is an effective disinfectant for a 

broad spectrum of microbial pathogens, 

including microorganisms like 

Cryptosporidium that are resistant to 

chlorine. 

Alternative 2 would have prohibited 

any single sample from exceeding the 

TTHM or HAA5 MCL. This is 

significantly more stringent than the 

preferred alternative and would likely 

require a large fraction of surface water 

systems to switch from their current 

treatment practices to more expensive 

advanced technologies. Consistent with 

the Advisory Committee, EPA does not 

believe such a drastic shift is warranted 

at this time. 

Similarly, Alternative 3, which would 

decrease TTHM and HAA5 MCLs to 

0.040 mg/L and 0.030 mg/L, 

respectively, and would require a 

significant portion of surface water 

systems to implement expensive 

advanced technologies in place of their 

existing treatment. Further, compliance 

with TTHM and HAA5 MCLs under this 

alternative would be based on the RAA, 

which does not specifically address DBP 

peaks in the distribution system as the 

LRAA, in conjunction with the IDSE, 

are designed to do. Based on these 

considerations, EPA and the Advisory 

Committee did not favor this alternative. 

C. Benefits of the Stage 2 DBPR 

The benefits analysis for the Stage 2 

DBPR includes a description of nonquantified benefits, calculations of 

quantified benefits, and a discussion of 

when benefits will occur after today’s 

final rule is implemented. An overview 

of the methods used to determine 

benefits is provided in Section VI.B. 

More detail can be found in the final 

EA. A summary of benefits for the Stage 

2 DBPR is given in this section. 

1. Nonquantified Benefits 

Non-quantified benefits of the Stage 2 

DBPR include potential benefits from 

reduced reproductive and 

developmental risks, reduced risks of 

cancers other than bladder cancer, and 

improved water quality. EPA believes 

that additional benefits from this rule 

could come from a reduction in 

potential reproductive and 

developmental risks. However, EPA 

does not believe the available evidence 

provides an adequate basis for 

quantifying these potential risks in the 

primary analysis. 

Both toxicology and epidemiology 

studies indicate that other cancers may 

be associated with DBP exposure but 

currently there is not enough data to 

include them in the primary analysis. 

However, EPA believes that the 

association between exposure to DBPs 

and colon and rectal cancer is possibly 


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significant, so an analysis of benefits is 

presented as a sensitivity analysis. 

To the extent that the Stage 2 DBPR 

changes perceptions of the health risks 

associated with drinking water and 

improves taste and odor, it may reduce 

actions such as buying bottled water or 

installing filtration devices. Any 

resulting cost savings would be a 

regulatory benefit. Also, as PWSs move 

away from conventional treatment to 

more advanced technologies, other nonhealth benefits are anticipated besides 

better tasting and smelling water. For 

example, GAC lowers nutrient 

availability for bacterial growth, 

produces a biologically more stable 

finished water, and facilitates 

management of water quality in the 

distribution system. Since GAC also 

removes synthetic organic chemicals 

(SOCs), it provides additional protection 

from exposure to chemicals associated 

with accidental spills or environmental 

runoff. 

2. Quantified Benefits 

EPA has quantified the benefits 

associated with the expected reductions 

in the incidence of bladder cancer. As 

discussed in Section VI.B, EPA used the 

PAR values from all three approaches to 

estimate the number of bladder cancer 

cases ultimately avoided annually as a 

result of the Stage 2 DBPR, shown in 

Figure VI.C–1. 

Table VI.C–1 summarizes the 

estimated number of bladder cancer 

cases avoided as a result of the Stage 2 

DBPR, accounting for cessation lag and 

the rule implementation schedule, and 

the monetized value of those cases. The 

benefits in Table VI.C–1 were developed 

using the PAR value from Villanueva et 

al. (2003), as described in Section VI.B. 

Table VI.C–1 summarizes the benefits 

for the Preferred Regulatory Alternative 

for the Stage 2 DBPR. Benefits estimates 

for the other regulatory alternatives 

were derived using the same methods as 

for the Preferred Regulatory Alternative 

and are presented in the EA. 

The confidence bounds of the results 

in Table VI.C–1 reflect uncertainty in 

PAR, uncertainty in the compliance 

forecast and resulting reduction in DBP 

concentrations, and cessation lag. 

Confidence bounds of the monetized 

benefits also reflect uncertainty in 

valuation parameters. An estimated 26 

percent of bladder cancer cases avoided 

are fatal, and 74 percent are non-fatal 

(USEPA 1999b). The monetized benefits 

therefore reflect the estimate of avoiding 

both fatal and non-fatal cancers in those 

proportions. 


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TABLE VI.C–1.—SUMMARY OF QUANTIFIED BENEFITS FOR THE STAGE 2 DBPR (MILLIONS OF $2003) 

Annual average cases avoided Discount rate, WTP for nonfatal cases Annualized benefits of cases avoided 

Cessation lag model 

Mean 5th 95th Mean 5th 95th 

279 103 541 3%, Lymphoma ...................

7% Lymphoma ....................

3% Bronchitis ......................

7% Bronchitis ......................

$1,531 

1,246 

763 

621 

$233 

190 

165 

135 

$3,536 

2,878 

1,692 

1,376 

Smoking/Lung Cancer 

188 61 399 3%, Lymphoma ...................

7% Lymphoma ....................

3% Bronchitis ......................

7% Bronchitis ......................

1,032 

845 

514 

420 

157 

129 

111 

91 

2,384 

1,950 

1,141 

932 

Smoking/Bladder Cancer 

333 138 610 3%, Lymphoma ...................

7% Lymphoma ....................

3% Bronchitis ......................

7% Bronchitis ......................

1,852 

1,545 

922 

769 

282 

235 

200 

167 

4,276 

3,566 

2,045 

1,704 

Arsenic/Bladder Cancer 

Notes: Values are discounted and annualized in 2003$. The 90 percent confidence interval for cases incorporates uncertainty in PAR, reduction in average TTHM and HAA5 concentrations, and cessation lag. The 90 percent confidence bounds for monetized benefits reflect uncertainty 

in monetization inputs relative to mean cases. Based on TTHM as an indicator, benefits were calculated using the Villanueva et al. (2003) PAR. 

EPA recognizes that benefits may be as low as zero since causality has not yet been established between exposure to chlorinated water and 

bladder cancer. Assumes 26 percent of cases are fatal, 74 percent are non-fatal (USEPA 1999b). 

Source: Exhibit 6.1, USEPA 2005a. 

3. Timing of Benefits Accrual 

EPA recognizes that it is unlikely that 

all cancer reduction benefits would be 

realized immediately upon exposure 

reduction. Rather, it is expected that 

there will likely be some transition 

period as individual risks reflective of 

higher past exposures at the time of rule 

implementation become, over time, 

more reflective of the new lower 

exposures. EPA developed cessation lag 

models for DBPs from literature to 

describe the delayed benefits, in 

keeping with the recommendations of 

the SAB (USEPA 2001d). Figure VI.C–2 

illustrates the effects of the cessation lag 

models. The results from the cessation 

lag models show that the majority of the 

potential cases avoided occur within the 

first fifteen years after initial reduced 

exposure to DBPs. For example, fifteen 

years after the exposure reduction has 

occurred, the annual cases avoided will 

be 489 for the smoking/lung cancer 

cessation lag model, 329 for the 

smoking/bladder cancer cessation lag 

model, and 534 cases for the arsenic/ 

bladder cancer cessation lag model. 

These represent approximately 84%, 

57%, and 92%, respectively, of the 

estimated 581 annual cases ultimately 

avoidable by the Stage 2 DBPR. 

In addition to the delay in reaching a 

steady-state level of risk reduction as a 

result of cessation lag, there is a delay 

in attaining maximum exposure 

reduction across the entire affected 

population that results from the Stage 2 

DBPR implementation schedule. For 

example, large surface water PWSs have 

six years from rule promulgation to 

meet the new Stage 2 MCLs, with up to 

a two-year extension possible for capital 

improvements. In general, EPA assumes 

that a fairly constant increment of 

systems will complete installation of 

new treatment technologies each year, 

with the last systems installing 

treatment by 2016. The delay in 

exposure reduction resulting from the 

rule implementation schedule is 

incorporated into the benefits model by 

adjusting the cases avoided for the given 

year and is illustrated in Table VI.C–2. 


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TABLE VI.C–2.—BLADDER CANCER CASES AVOIDED (TTHM AS INDICATOR) EACH YEAR USING THREE CESSATION LAG

MODELS

Year 

Smoking/lung cancer 

cessation lag model 

Smoking/bladder cancer cessation lag 

model 

Arsenic/bladder cancer cessation lag 

model 

Total Percent Total Percent Total Percent 

1 ............................................................................................................... 0 0 0 0 0 0 

2 ............................................................................................................... 0 0 0 0 0 0 

3 ............................................................................................................... 0 0 0 0 0 0 

4 ............................................................................................................... 0 0 0 0 0 0 

5 ............................................................................................................... 0 0 0 0 0 0 

6 ............................................................................................................... 24 4 23 4 45 8 

7 ............................................................................................................... 62 11 54 9 110 19 

8 ............................................................................................................... 111 19 90 16 187 32 

9 ............................................................................................................... 170 29 132 23 275 48 

10 ............................................................................................................. 220 38 161 28 334 58 

11 ............................................................................................................. 265 46 184 32 379 65 

12 ............................................................................................................. 305 53 204 35 412 71 

13 ............................................................................................................. 341 59 221 38 438 76 

14 ............................................................................................................. 371 64 237 41 458 79 

15 ............................................................................................................. 396 68 251 43 475 82 

16 ............................................................................................................. 416 72 265 46 488 84 

17 ............................................................................................................. 433 75 278 48 499 86 

18 ............................................................................................................. 448 77 289 50 509 88 

19 ............................................................................................................. 460 79 301 52 516 89 

20 ............................................................................................................. 471 81 311 54 523 90 

21 ............................................................................................................. 481 83 321 55 528 91 

22 ............................................................................................................. 489 84 330 57 533 92 

23 ............................................................................................................. 496 86 339 59 537 93 

24 ............................................................................................................. 503 87 347 60 541 93 

25 ............................................................................................................. 509 88 355 61 544 94 

Notes: Percent of annual cases ultimately avoidable achieved during each of the first 25 years. The benefits model estimates 581 (90% CB = 

229–1,079) annual cases ultimately avoidable using the Villanueva et al. (2003) PAR inputs and including uncertainty in these and DBP reductions. EPA recognizes that benefits may be as low as zero since causality has not yet been established between exposure to chlorinated water 

and bladder cancer. 

Source: Summarized from detailed results presented in Exhibits E.38a, E.38e and E.38i, USEPA 2005a. 

D. Costs of the Stage 2 DBPR 

National costs include those of 

treatment changes to comply with the 

rule as well as non-treatment costs such 

as for Initial Distribution System 

Evaluations (IDSEs), additional routine 

monitoring, and operational 

evaluations. The methodology used to 

estimate costs is described in Section 

VI.B. More detail is provided in the EA 

(USEPA 2005a). The remainder of this 

section presents summarized results of 

EPA’s cost analysis for total annualized 

present value costs, PWS costs, State/ 

Primacy agency costs, and nonquantified costs. 

1. Total Annualized Present Value Costs 

Tables VI.D–1 and VI.D–2 summarize 

the average annualized costs for the 

Stage 2 DBPR Preferred Regulatory 

Alternative at 3 and 7 percent discount 

rates, respectively. System costs range 

from approximately $55 to $101 million 

annually at a 3 percent discount rate, 

with a mean estimate of approximately 

$77 million per year. The mean and 

range of annualized costs are similar at 

a 7 percent discount rate. State costs are 

estimated to be between $1.70 and $1.71 

million per year depending on the 

discount rate. These estimates are 

annualized starting with the year of 

promulgation. Actual dollar costs 

during years when most treatment 

changes are expected to occur would be 

somewhat higher (the same is true for 

benefits that occur in the future). 

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2. PWS costs 

PWS costs for the Stage 2 DBPR 

include non-treatment costs of rule 

implementation, Initial Distribution 

System Evaluations (IDSEs), Stage 2 

DBPR monitoring plans, additional 

routine monitoring, and operational 

evaluations. Systems required to install 

treatment to comply with the MCLs will 

accrue the additional costs of treatment 

installation as well as operation and 

maintenance. Significant PWS costs for 

IDSEs, treatment, and monitoring are 

described in this section, along with a 

sensitivity analysis. 

a. IDSE costs. Costs and burden 

associated with IDSE activities differ 

depending on whether or not the system 

performs the IDSE and, if so, which 

option a system chooses. All systems 

performing the IDSE are expected to 

incur some costs. EPA’s analysis 

allocated systems into five categories to 

determine the costs of the IDSE—those 

conducting standard monitoring, SSS, 

VSS, 40/30, and NTNCWS not required 

to do an IDSE. EPA then developed cost 

estimates for each option. Tables VI.D–

3, VI.D–4, and VI.D–5 illustrate PWS 

costs for IDSE for systems conducting an 

SMP, SSS, and 40/30, respectively. 


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b. PWS treatment costs. The number 

of plants changing treatment as a result 

of the Stage 2 DBPR and which 

technology various systems will install 

are determined from the compliance 

forecast. The percent of systems 

predicted to make treatment technology 

changes and the technologies predicted 

to be in place after implementation of 

the Stage 2 DBPR are shown in Table 

VI.D–6. The cost model includes 

estimates for the cost of each 

technology; the results of the cost model 

for PWS treatment costs are summarized 

in Table VI.D–7. 


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c. Monitoring costs. Because systems 

already sample for the Stage 1 DBPR, 

costs for additional routine monitoring 

are determined by the change in the 

number of samples to be collected from 

the Stage 1 to the Stage 2 DBPR. The 


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Stage 2 DBPR monitoring requirements 

for systems are based only on 

population served and source water 

type, while the Stage 1 DBPR 

requirements are also based on the 

number of treatment plants. With this 

modification in monitoring scheme, the 

average system will have no change in 

monitoring costs. The number of 

samples required is estimated to 

increase for some systems but actually 

decrease from the Stage 1 to the Stage 

2 DBPR for many systems. Table VI.D–

8 summarizes the estimated additional 

routine monitoring costs for systems. 

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3. State/Primacy Agency Costs 

To estimate State/Primacy Agency 

costs, the estimated number of full-time 

equivalents (FTEs) required per activity 

is multiplied by the number of labor 

hours per FTE, the State/Primacy 

Agency hourly wage, and the number of 

States/Primacy Agencies. EPA estimated 

the number of FTEs required per 

activity based on experience 

implementing previous rules, such as 

the Stage 1 DBPR. State/Primacy Agency 

costs are summarized in Table VI.D–9. 

4. Non-quantified Costs 

All significant costs that EPA has 

identified have been quantified. In some 

instances, EPA did not include a 

potential cost element because its effects 

are relatively minor and difficult to 

estimate. For example, it may be less 

costly for a small system to merge with 

neighboring systems than to add 

advanced treatment. Such changes have 

both costs (legal fees and connecting 

infrastructure) and benefits (economies 

of scale). Likewise, procuring a new 

source of water would have costs for 

new infrastructure, but could result in 

lower treatment costs. Operational costs 

such as changing storage tank operation 

were also not considered as alternatives 

to treatment. These might be options for 

systems with a single problem area with 

a long residence time. In the absence of 

detailed information needed to evaluate 

situations such as these, EPA has 

included a discussion of possible effects 

where appropriate. In general, however, 

the expected net effect of such 

situations is lower costs to PWSs. Thus, 

the EA tends to present conservatively 

high estimates of costs in relation to 

non-quantified costs. 

E. Household Costs of the Stage 2 DBPR 

EPA estimates that, as a whole, 

households subject to the Stage 2 DBPR 

face minimal increases in their annual 

costs. Approximately 86 percent of the 

households potentially subject to the 

rule are served by systems serving at 

least 10,000 people; these systems 

experience the lowest increases in costs 

due to significant economies of scale. 

Households served by small systems 

that add treatment will face the greatest 

increases in annual costs. Table VI.E–1 

summarizes annual household cost 

increases for all system sizes. 


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TABLE VI.E–1.—ANNUAL HOUSEHOLD COST INCREASES. 

Total number 

of households 

served 

Mean annual household cost increase Median annual household cost increase 

90th percentile annual household cost increase 95th percentile annual household cost increase 

Percentage 

of annual 

household 

cost increase < 

$12 (percent) 

Percentage 

of annual 

household 

cost increase < 

$120 (percent) 

Households Served by All Plants 

All Systems .......................................... 101,553,868 $0.62 $0.03 $0.36 $0.98 99 100 

All Small Systems ................................ 14,261,241 2.20 0.10 0.79 2.57 97 100 

SW < 10,000 ........................................ 3,251,893 4.58 0.79 2.69 7.24 95 99 

SW ≥ 10,000 ........................................ 62,137,350 0.46 0.02 0.35 1.81 99 100 

GW < 10,000 ....................................... 11,009,348 1.49 0.02 0.39 0.99 98 100 

GW ≥ 10,000 ........................................ 25,155,277 0.13 0.00 0.03 0.08 100 100 

Households Served by Plants Adding Treatment 

All Systems .......................................... 10,161,304 $5.53 $0.80 $10.04 $22.40 92 99 

All Small Systems ................................ 591,623 46.48 18.47 168.85 197.62 38 89 

SW < 10,000 ........................................ 285,911 43.05 13.79 173.53 177.93 47 85 

SW ≥ 10,000 ........................................ 9,060,119 2.83 0.80 6.98 11.31 96 100 

GW < 10,000 ....................................... 305,712 49.69 16.65 109.86 197.62 31 92 

GW ≥ 10,000 ........................................ 509,562 5.97 1.37 26.82 33.84 79 100 

Notes: Detail may not add to total due to independent rounding. Number of households served by systems adding treatment will be higher 

than households served by plants adding treatment because an entire system will incur costs even if only some of the plants for that system add 

treatment (this would result in lower household costs, however). 

Source: Exhibit 7.15, USEPA 2005a. 

F. Incremental Costs and Benefits of the 

Stage 2 DBPR 

Incremental costs and benefits are 

those that are incurred or realized in 

reducing DBP exposures from one 

alternative to the next more stringent 

alternative. Estimates of incremental 

costs and benefits are useful in 

considering the economic efficiency of 

different regulatory options considered 

by the Agency. Generally, the goal of an 

incremental analysis is to identify the 

regulatory option where net social 

benefits are maximized. However, the 

usefulness of this analysis is 

constrained when major benefits and/or 

costs are not quantified or not 

monetized. Also, as pointed out by the 

Environmental Economics Advisory 

Committee of the Science Advisory 

Board, efficiency is not the only 

appropriate criterion for social decision 

making (USEPA 2000i). 

For the proposed Stage 2 DBPR, 

presentation of incremental quantitative 

benefit and cost comparisons may be 

unrepresentative of the true net benefits 

of the rule because a significant portion 

of the rule’s potential benefits are not 

quantified, particularly potential 

reproductive and developmental health 

effects (see Section VI.C). Table VI.F–1 

shows the incremental monetized costs 

and benefits for each regulatory 

alternative. Evaluation of this table 

shows that incremental costs generally 

fall within the range of incremental 

benefits for each more stringent 

alternative. Equally important, the 

addition of any benefits attributable to 

the non-quantified categories would add 

to the benefits without any increase in 

costs. 

Table VI.F–1 shows that the Preferred 

Alternative is the least-cost alternative. 

A comparison of Alternative 1 with the 

Preferred Alternative shows that 

Alternative 1 would have approximately 

the same benefits as the Preferred 

Alternative. The costs of Alternative 1 

are greater due to the additional control 

of bromate. However, the benefits of 

Alternative 1 are less than the Preferred 

Alternative because the Agency is not 

able to estimate the additional benefits 

of reducing the bromate MCL. 

Alternative 1 was determined to be 

unacceptable due to the potential for 

increased risk of microbial exposure. 

Both benefits and costs are greater for 

Alternative 2 and Alternative 3 as 

compared to the Preferred Alternative. 

However, these regulatory alternatives 

do not have the risk-targeted design of 

the Preferred Alternative. Rather, 

implementation of these stringent 

standards would require a large number 

of systems to change treatment 

technology. The high costs of these 

regulatory alternatives and the drastic 

shift in the nation’s drinking water 

practices were considered unwarranted 

at this time. (See Section VI.A of this 

preamble for a description of regulatory 

alternatives.) 

TABLE VI.F–1.—INCREMENTAL COSTS AND BENEFITS OF THE STAGE 2 DBPR 

WTP for non-fatal 

bladder cancer cases Rule alternative 

Annual 

costs 

Annual benefits Incremental costs Incremental benefits Incremental net benefits 

A B C D E=D¥C 

3 Percent Discount Rate 

Lymphoma ............... Preferred ................. $79 $1,531 $79 .......................... $1,531 ..................... $1,452 

Alternative 1 1 .......... 254 1,377 (1) ............................ (1) ............................ (1) 

Alternative 2 ............ 422 5,167 343 .......................... 3,637 ....................... 3,294 

Alternative 3 ............ 634 7,130 212 .......................... 1,962 ....................... 1,750 

Bronchitis ................. Preferred ................. 79 763 79 ............................ 763 .......................... 684 


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TABLE VI.F–1.—INCREMENTAL COSTS AND BENEFITS OF THE STAGE 2 DBPR—Continued 

WTP for non-fatal 

bladder cancer cases Rule alternative 

Annual 

costs 

Annual benefits Incremental costs Incremental benefits Incremental net benefits 

A B C D E=D¥C 

Alternative 1 1 .......... 254 686 (1) ............................ (1) ............................ (1) 

Alternative 2 ............ 422 2,575 343 .......................... 1,812 ....................... 1,469 

Alternative 3 ............ 634 3,552 212 .......................... 978 .......................... 765 

7 Percent Discount Rate 

Lymphoma ............... Preferred ................. $77 $1,246 $77 .......................... $1,246 ..................... $1,170 

Alternative 1 1 .......... 242 1,126 (1) ............................ (1) ............................ (1) 

Alternative 2 ............ 406 4,227 330 .......................... 2,981 ....................... 2,651 

Alternative 3 ............ 613 5,832 207 .......................... 1,605 ....................... 1,399 

Bronchitis ................. Preferred ................. 77 621 77 ............................ 621 .......................... 544 

Alternative 1 1 .......... 242 561 (1) ............................ (1) ............................ (1) 

Alternative 2 ............ 406 2,105 330 .......................... 1,484 ....................... 1,154 

Alternative 3 ............ 613 2,904 207 .......................... 799 .......................... 593 

Notes: Estimates are discounted to 2003 and given in 2003 dollars. Based on TTHM as an indicator, Villanueva et al. (2003) for baseline risk, 

and smoking/lung cancer cessation lag model. Assumes 26 percent of cases are fatal, 74 percent are non-fatal (USEPA 1999b). EPA recognizes 

that benefits may be as low as zero since causality has not yet been established between exposure to chlorinated water and bladder cancer. 1Alternative 1 appears to have fewer benefits than the Preferred Alternative because it does not incorporate the IDSE, as explained in Chapter 

4. Furthermore, this EA does not quantify the benefits of reducing the MCL for bromate (and potentially associated cancer cases), a requirement 

that is included only in Alternative 1. This means that Alternative 1 is dominated by the Preferred Alternative in this analysis (having higher costs 

than the Preferred Alternative but lower benefits), and so it is not included in the incremental comparison of alternatives (Columns C–E). OMB 

states this in terms of comparing cost effectiveness ratios, but the same rule applies to an incremental cost, benefits, or net benefits comparison: 

‘‘When constructing and comparing incremental cost-effectiveness ratios, [analysts] * * * should make sure that inferior alternatives identified by 

the principles of strong and weak dominance are eliminated from consideration.’’ (OMB Circular A–4, p. 10) 

Source: Exhibit 9.13, USEPA 2005a. 

G. Benefits From the Reduction of Cooccurring Contaminants 

Installing certain advanced 

technologies to control DBPs has the 

added benefit of controlling other 

drinking water contaminants in addition 

to those specifically targeted by the 

Stage 2 DBPR. For example, membrane 

technology installed to reduce DBP 

precursors can also reduce or eliminate 

many other drinking water 

contaminants (depending on pore size), 

including those that EPA may regulate 

in the future. Removal of any 

contaminants that may face regulation 

could result in future cost savings to a 

water system. Because of the difficulties 

in establishing which systems would be 

affected by other current or future rules, 

no estimate was made of the potential 

cost savings from addressing more than 

one contaminant simultaneously. 

H. Potential Risks From Other 

Contaminants 

Along with the reduction in DBPs 

from chlorination such as TTHM and 

HAA5 as a resultof the Stage 2 DBPR, 

there may be increases in other DBPs as 

systems switch from chlorine to 

alternative disinfectants. For all 

disinfectants, many DBPs are not 

regulated and many others have not yet 

been identified. EPA will continue to 

review new studies on DBPs and their 

occurrence levels to determine if they 

pose possible health risks. EPA 

continues to support regulation of 

TTHM and HAA5 as indicators for 

chlorination DBP occurrence and 

believes that operational and treatment 

changes made because of the Stage 2 

DBPR will result in an overall decrease 

in risk. 

1. Emerging DBPs 

Iodo-DBPs and nitrogenous DBPs 

including halonitromethanes are DBPs 

that have recently been reported 

(Richardson et al. 2002, Richardson 

2003). One recent occurrence study 

sampled quarterly at twelve surface 

water plants using different 

disinfectants across the U.S. for several 

iodo-THMs and halonitromethane 

species (Weinberg et al. 2002). The 

concentrations of iodo-THMs and 

halonitromethane in the majority of 

samples in this study were less than the 

analytical minimum reporting levels; 

plant-average concentrations of iodoTHM and halonitromethane species 

were typically less than 0.002 mg/L, 

which is an order of magnitude lower 

than the corresponding average 

concentrations of TTHM and HAA5 at 

those same plants. Chloropicrin, a 

halonitromethane species, was also 

measured in the ICR with a median 

concentration of 0.00019 mg/L across all 

surface water samples. No occurrence 

data exist for the iodoacids due to the 

lack of a quantitative method and 

standards. Further work on chemical 

formation of iodo-DBPs and 

halonitromethanes is needed. 

Iodoacetic acid was found to be 

cytotoxic and genotoxic in Salmonella 

and mammalian cells (Plewa et al. 

2004a) as were some of the 

halonitromethanes (Kundu et al. 2004; 

Plewa et al. 2004b). Although potent in 

these in vitro screening studies, further 

research is needed to determine if these 

DBPs are active in living systems. No 

conclusions on human health risk can 

be drawn from such preliminary 

studies. 

2. N-Nitrosamines 

Another group of nitrogenous DBPs 

are the N-nitrosamines. A number of Nnitrosamines exist, and Nnitrosodimethylamine (NDMA), a 

probable human carcinogen (USEPA 

1993), has been identified as a potential 

health risk in drinking water. NDMA is 

a contaminant from industrial sources 

and a potential disinfection byproduct 

from reactions of chlorine or chloramine 

with nitrogen containing organic matter 

and from some polymers used as 

coagulant aids. Studies have produced 

new information on the mechanism of 

formation of NDMA, but there is not 

enough information at this time to draw 

conclusions regarding a potential 

increase in NDMA occurrence as 

systems change treatment. Although 

there are studies that examined the 

occurrence of NDMA in some water 

systems, there are no systematic 

evaluations of the occurrence of NDMA 

and other nitrosamines in U.S. waters. 


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Recent studies have provided new 

occurrence information that shows 

NDMA forms in both chlorinated and 

chloraminated systems. Barrett et al. 

(2003) reported median concentrations 

of less than 2ng/L for the seven chlorine 

systems studied and less than 3 ng/L for 

13 chloramine systems. Another study 

demonstrated that factors other than 

disinfectant type may play an important 

role in the formation of NDMA 

(Schreiber and Mitch 2005). More 

research is underway to determine the 

extent of NDMA occurrence in drinking 

water systems. EPA has proposed 

monitoring for NDMA under 

Unregulated Contaminant Monitoring 

Rule 2 (70 FR 49094, at 49103, August 

22, 2005) (USEPA 2005m). 

Risk assessments have estimated that 

the 10¥6 lifetime cancer risk level is 7 

ng/L based on induction of tumors at 

multiple sites. NDMA is also present in 

food, tobacco smoke, and industrial 

emissions, and additional research is 

underway to determine the relative 

exposure of NDMA in drinking water to 

these other sources. 

3. Other DBPs 

Some systems, depending on bromide 

and organic precursor levels in the 

source water and technology selection, 

may experience a shift to higher ratios, 

or concentrations, of brominated DBPs 

while the overall TTHM or HAA5 

concentration may decrease. In some 

instances where alternative 

disinfectants are used, levels of chlorite 

and bromate may increase as a result of 

systems switching to chlorine dioxide or 

ozone, respectively. However, EPA 

anticipates that changes in chlorite and 

bromate concentration as a result of the 

Stage 2 DBPR will be minimal (USEPA 

2005a). For most systems, overall levels 

of DBPs, as well as brominated DBP 

species, should decrease as a result of 

this rule. EPA continues to believe that 

precursor removal is a highly effective 

strategy to reduce levels of DBPs. 

EPA also considered the impact this 

rule may have on microbial 

contamination that may result from 

altering disinfection practices. To 

address this concern, the Agency 

developed this rule jointly with the 

Long Term 2 Enhanced Surface Water 

Treatment Rule (LT2ESWTR). EPA 

expects that the LT2ESWTR provisions 

will prevent increases in microbial risk 

resulting from the Stage 2 DBPR. 

I. Effects of the Contaminant on the 

General Population and Groups Within 

the General Population That Are 

Identified As Likely To Be at Greater 

Risk of Adverse Health Effects 

EPA’s Office of Water has historically 

considered risks to sensitive 

subpopulations (including fetuses, 

infants, and children) when establishing 

drinking water assessments, advisories 

and other guidance, and standards 

(USEPA 1989) (56 FR 3526, January 30, 

1991) (USEPA 1991). In the case of 

Stage 2 DBPR, maximizing health 

protection for sensitive subpopulations 

requires balancing risks to achieve the 

recognized benefits of controlling 

waterborne pathogens while minimizing 

risk of potential DBP toxicity. 

Experience shows that waterborne 

disease from pathogens in drinking 

water is a major concern for children 

and other subgroups (e.g., the elderly, 

immunocompromised, and pregnant 

women) because of their greater 

vulnerabilities (Gerba et al. 1996). EPA 

believes DBPs may also potentially pose 

risks to fetuses and pregnant women 

(USEPA 1998a). In addition, because the 

elderly population (age 65 and above) is 

naturally at a higher risk of developing 

bladder cancer, their health risks may 

further increase as a result of long-term 

DBP exposure (National Cancer Institute 

2002). 

In developing this rule, risks to 

sensitive subpopulations, including 

children, were taken into account in the 

assessments of disinfectants and DBPs. 

More details on sensitive 

subpopulations can be found in the 

Economic Analysis (USEPA 2005a). For 

each of the DBPs included in the Stage 

2 DBPR, the maximum contaminant 

level goals (MCLG) are derived using the 

most sensitive endpoint among all 

available data and an intraspecies 

uncertainty factor of 10 which accounts 

for human variability including 

sensitive subpopulations, like children. 

The Agency has evaluated several 

alternative regulatory options and 

selected the one that balances cost with 

significant benefits, including those for 

sensitive subpopulations. The Stage 2 

DBPR will result in a potential 

reduction in cancer risk and a potential 

reduction in reproductive and 

developmental risk to fetuses and 

pregnant women. It should be noted that 

the LT2ESWTR, which accompanies 

this rule, reduces pathogens in drinking 

water and further protects sensitive 

subpopulations. See Section VII.G for a 

discussion of EPA’s requirements under 

Executive Order 13045. 

J. Uncertainties in the Risk, Benefit, and 

Cost Estimates for the Stage 2 DBPR 

For today’s final rule, EPA has 

estimated the current baseline risk from 

exposure to DBPs in drinking water and 

projected the risk reduction and cost for 

various rule alternatives. There is 

uncertainty in the risk calculation, the 

benefit estimates, the cost estimates, and 

the interaction with other regulations. 

The EA has an extensive discussion of 

relevant uncertainties (USEPA 2005a). 

This section briefly summarizes the 

major uncertainties. Table VI.J–1 

presents a summary of uncertainty in 

the cost and benefit estimates, refers to 

the section or appendix of the EA where 

the information is introduced, and 

estimates the potential effects that each 

may have on national cost and benefit 

estimates. 

EPA believes that uncertainty in the 

compliance forecast has a potentially 

large influence on cost and benefit 

estimates for today’s rule. Thus, the 

Agency has attempted to quantify the 

uncertainty by giving equal weight to 

two different compliance forecast 

approaches. One compliance forecast 

approach is based on the SWAT 

predictions, and the other is based on 

the ‘‘ICR Matrix Method.’’ The ICR 

Matrix Method uses the same basic 

approach as SWAT, but uses TTHM and 

HAA5 data from the ICR directly to 

estimate the percent of plants changing 

technology to comply with the Stage 2 

DBPR and the resulting DBP reduction. 

To characterize the uncertainty of the 

compliance forecast results, EPA 

assumes a uniform distribution between 

SWAT and ICR Matrix Method results 

(USEPA 2005a). That is, the cost and 

benefit estimates presented in the 

preamble represent the midpoint 

between costs and benefits estimated 

using the SWAT model, and those 

estimated using the ICR Matrix Method. 

Cost estimates using the SWAT model 

are about 25% lower than the midpoint 

estimates, while those using the ICR 

Matrix Method are about 25% higher. 

Benefits estimated using the SWAT 

model are about 30% lower than the 

midpoint estimates, while those using 

the ICR Matrix Method are about 30% 

higher. 

EPA believes the compliance forecast 

may be overstated because the 

technology decision tree does not 

consider low-cost, non-treatment system 

improvements that could be used to 

comply with the Stage 2 DBPR. These 

improvements, including things like 

flushing more frequently and managing 

storage facilities to reduce water age, 

could be used by systems to reduce 

TTHM and HAA5 levels for specific 


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locations in their distribution system to 

meet Stage 2 DBPR MCLs. Thus, the 

standard compliance forecast method as 

developed during the M/DBP FACA 

(with a 20 percent safety margin) is a 

reasonable estimation. However, SWAT 

does not explicitly consider the IDSE. 

To address uncertainty in the impact of 

the IDSE on the compliance forecast, 

EPA revised the compliance forecast 

methodology, assigning equal 

probability to 20 and 25 percent 

operational safety margins. EPA believes 

the 25 percent safety margin is a 

reasonable high-end estimate of system 

response to account for the influences of 

the IDSE. EPA used a spatial variability 

analysis to determine the appropriate 

safety margin to use to estimate the 

impact of the IDSE on the compliance 

forecast. 

These alternative approaches for the 

compliance forecast estimate are used to 

represent a range of possible results and 

are incorporated into the cost and 

benefit models using Monte Carlo 

probability functions. EPA believes this 

approach helps inform the reader of the 

likely magnitude of the impact of the 

uncertainties. 

In addition to quantifying some 

uncertainties in the compliance 

forecasts, EPA has explicitly accounted 

for uncertainty in estimated treatment 

technology costs. Treatment costs are 

modeled using a triangular distribution 

of ± 30 percent for Capital, and ± 15 

percent for O&M costs to recognize that 

the assumptions for cost analysis to 

produce the national average are 

uncertain. 

For the cost estimates, uncertainty 

also exists in baseline data inputs, such 

as the total number of disinfecting 

plants and their typical average and 

design flow rates. Other cost model 

inputs such as labor rates and laboratory 

fees also contain uncertainties. In these 

cases, EPA has evaluated available data 

and estimated a cost input value to 

represent the average of all water 

systems nationally. EPA recognizes that 

there is uncertainty in this average and 

variability in the characteristics of 

individual systems. The influence of 

these uncertainties on national cost 

estimates is expected to be fairly minor. 

For the benefits estimates, uncertainty 

exists in model inputs such as the 

estimated PAR values and the cessation 

lag models. EPA considered three 

approaches to estimate attributable risk: 

(1) a range of risk derived from 

individual studies, (2) a risk estimate 

from a meta-analysis, and (3) a risk 

estimate from a pooled analysis. To 

quantify uncertainty in cessation lag, 

three independent cessation lag models 

derived from three different 

epidemiological studies are used. Also, 

two functional forms are used for each 

of these data sets and uncertainty in the 

parameters of those functions is 

included in the analysis. As noted 

previously, causality has not been 

established between DBP levels and 

cancer endpoints, so the lower bound of 

potential risk reductions may be as low 

as zero. 

In a number of different contexts over 

the past few years, the Agency has 

considered the relative merits and 

assumptions encountered when 

employing meta-analyses. Cessation lag 

modeling is a relatively recent analysis 

that the Agency has incorporated into 

its risk analyses to more appropriately 

model the timing of health benefits. The 

specific papers upon which the Stage 2 

analysis is based have been peer 

reviewed. However, the Agency believes 

that it is time to consider these Agencywide science issues in a broader sense 

with outside experts to better inform the 

Agency’s future analyses. 

For monetization of benefits, EPA 

uses two alternatives for valuing nonfatal bladder cancer. Other 

uncertainties, such as the linear 

relationship between DBP reductions 

and reductions in bladder cancer cases 

avoided, are discussed qualitatively. 

In addition to the uncertainties 

quantified as part of the benefits 

evaluation, other uncertainties that have 

not been quantified could result in 

either an over-or under-estimation of the 

benefits. Two of the greatest 

uncertainties affecting the benefits of 

the Stage 2 DBPR, benefits from 

potential reductions of cancers other 

than bladder and benefits from possible 

reductions in potential reproductive and 

developmental health effects, are 

unquantified. Both of these factors 

could result in an underestimation of 

quantified Stage 2 DBPR benefits. 

TABLE VI.J–1.—EFFECTS OF UNCERTAINTIES ON NATIONAL ESTIMATES

Assumptions for which there 

is uncertainty 

Section with 

full discussion 

of uncertainty 

Potential effect on benefit estimate Potential effect on cost estimates 

Under-estimate Over-estimate Unknown impact Under-estimate Over-estimate Unknown impact 

Uncertainty in the industry 

baseline (SDWIS and 

1995 CWSS data).

3.4 ................ .................. .................. X ................... .................. .................. X 

Uncertainty in observed data 

and predictive tools used 

to characterize DBP occurrence for the pre-Stage 

1 baseline.

3.7 ................ .................. .................. X ................... .................. .................. X 

Uncertainty in predictive 

tools used to develop the 

compliance forecast for 

surface water systems 

(SWAT and ICR Matrix 

Method).

Chapter 5, 

Appendix A.

Quantified in primary analysis (addresses potential underestimate or overestimate) Quantified in primary analysis (addresses potential underestimate or overestimate) 

Uncertainty in ground water 

compliance forecast methodologies.

Chapter 5, A 

and B.

.................. .................. X ................... .................. .................. X 

Operational safety margin of 

20%.

5.2 ................ .................. .................. X ................... .................. .................. X 

Impacts of the IDSE on the 

compliance forecast for 

the Preferred Regulatory 

Alternative.

5.3 ................ Quantified in the primary analysis (addresses 

potential underestimate) 

Quantified in the primary analysis (addresses 

potential underestimate) 


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TABLE VI.J–1.—EFFECTS OF UNCERTAINTIES ON NATIONAL ESTIMATES—Continued 

Assumptions for which there 

is uncertainty 

Section with 

full discussion 

of uncertainty 

Potential effect on benefit estimate Potential effect on cost estimates 

Under-estimate Over-estimate Unknown impact Under-estimate Over-estimate Unknown impact 

Uncertainty in the PAR 

value.

6.1.1 Appendix E.Quantified in the primary analysis (addresses 

range of potential effects, but true values 

could lie outside range) 

Reduction in TTHM and 

HAA5 used as proxies for 

all chlorination DBPs.

6.3.3 ............. .................. .................. X.

DBPs have a linear nothreshold dose-response 

relationship for bladder 

cancer effects.

6.2.1 ............. .................. X.

Uncertainty in benefits valuation inputs.6.5.2 ............. Quantified in the primary analysis (addresses 

potential underestimate or overestimate) 

Benefits of reduced cancers 

other than bladder cancer 

are not included in the 

quantitative analysis.

6.7 ................ Quantified in a sensitivity analysis (addresses 

potential underestimate) 

Value of potential reproductive and developmental 

health effects avoided is 

not quantified in the primary analysis.

6.8 ................ X.

Treatment costs do not include costs for minor 

operational changes predicted by SWAT.

7.4.1 ............. .................. .................. .................. X.

Median operational and 

water quality parameters 

considered for technology 

unit costs.

7.4.1 ............. .................. .................. .................. .................. .................. X 

Economies of scale for combination treatment technologies not considered.7.4.1 ............. .................. .................. .................. .................. X.

Possible UV-chloramine 

synergy not taken into account.

7.4.1 ............. .................. .................. .................. .................. X.

Potential low-cost alternatives to treatment not 

considered.

7.4.2 ............. .................. .................. .................. .................. X.

Uncertainties in unit costs ... 7.4.3 ............. .................. .................. .................. Quantified in primary analysis (addresses potential overestimate or underestimate) 

K. Benefit/Cost Determination for the 

Stage 2 DBPR 

The Agency has determined that the 

benefits of the Stage 2 DBPR justify the 

costs. As discussed previously, the main 

concern for the Agency and the 

Advisory Committee involved in the 

Stage 2 rulemaking process was to 

provide more equitable protection from 

DBPs across the entire distribution 

system and reduce high DBP levels. The 

final rule achieves this objective using 

the least cost alternative by targeting 

sampling locations with high DBP levels 

and modifying how the annual average 

DBP level is calculated. This will reduce 

both average DBP levels associated with 

bladder cancer (and possibly other 

cancers) and peak DBP levels which are 

potentially associated with reproductive 

and developmental effects. In addition, 

this rule may reduce uncertainty about 

drinking water quality and may allow 

some systems to avoid installing 

additional technology to meet future 

drinking water regulations. 

Table VI.K–1 presents net benefits for 

the four regulatory alternatives 

evaluated by EPA. This table shows that 

net benefits are positive for all four 

regulatory alternatives. Generally, 

analysis of net benefits is used to 

identify alternatives where benefits 

exceed costs, as well as the alternative 

that maximizes net benefits. However, 

analyses of net benefits should consider 

both quantified and non-quantified 

(where possible) benefits and costs. As 

discussed previously with incremental 

net benefits, the usefulness of this 

analysis in evaluating regulatory 

alternatives for the Stage 2 DBPR is 

somewhat limited because many 

benefits from this rule are nonquantified and non-monetized. 

Table VI.K–1 shows that the Preferred 

Alternative is the least cost alternative. 

The Preferred Alternative has higher 

mean net benefits than Alternative 1. 

Alternatives 2 and 3 have higher 

benefits than the Preferred Alternative 

but also much greater costs. These 

regulatory alternatives do not have the 

risk-targeted design of the Preferred 

Alternative. Rather, a large number of 

systems would be required to make 

treatment technology changes to meet 

the stringent standards under these 

regulatory alternatives. Also, because 

causality has not been established 

between DBP exposure and bladder 

cancer, actual benefits may be as low as 

zero. EPA is promulgating the preferred 

regulatory alternative because the 

Agency believes that such a drastic shift 

in the nation’s drinking water practices 

is not warranted at this time. 


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TABLE VI.K–1.—MEAN NET BENEFITS BY REGULATORY ALTERNATIVE ($MILLION) 

Rule alternative WTP for non-fatal bladder cancer cases Mean annual 

costs 

Mean annual 

benefits 

Mean net 

benefits 

3 Percent Discount Rate, 25 Years 

Preferred ......................................................... Lymphoma ...................................................... $78.8 $1,530.8 $1,452 

A1 .................................................................... .................................................................... 254.1 1,376.6 1,122 

A2 .................................................................... .................................................................... 421.7 5,167.4 4,746 

A3 .................................................................... .................................................................... 634.2 7,129.6 6,495 

Preferred ......................................................... Bronchitis ........................................................ 78.8 762.8 684 

A1 .................................................................... .................................................................... 254.1 685.9 432 

A2 .................................................................... .................................................................... 421.7 2,574.6 2,153 

A3 .................................................................... .................................................................... 634.2 3,552.2 2,918 

7 Percent Discount Rate, 25 Years 

Preferred ......................................................... Lymphoma ...................................................... $76.8 $1,246.5 $1,170 

A1 .................................................................... .................................................................... 241.8 1,126.4 885 

A2 .................................................................... .................................................................... 406.4 4,227.2 3,821 

A3 .................................................................... .................................................................... 613.1 5,832.4 5,219 

Preferred ......................................................... Bronchitis ........................................................ 76.8 620.7 544 

A1 .................................................................... .................................................................... 241.8 560.8 319 

A2 .................................................................... .................................................................... 406.4 2,104.6 1,698 

A3 .................................................................... .................................................................... 613.1 2,903.8 2,291 

Notes: Estimates are discounted to 2003 and given in 2003 dollars. Based on TTHM as an indicator, Villanueva et al. (2003) for baseline risk, 

and smoking/lung cancer cessation lag model. Assumes 26 percent of cases are fatal, 74 percent are non-fatal (USEPA 1999b). EPA recognizes 

that benefits may be as low as zero since causality has not yet been established exposure to chlorinated water and bladder cancer. 

Source: Exhibits 9.10 and 9.11, USEPA 2005a. 

The Agency also compared the costs 

and benefits for each regulatory 

alternative by calculating which option 

is the most cost-effective. The costeffectiveness analysis compares the cost 

of the rule per bladder cancer case 

avoided. This cost-effectiveness 

measure is another way of examining 

the benefits and costs of the rule, but 

should not be used to compare 

alternatives because an alternative with 

the lowest cost per illness/death 

avoided may not result in the highest 

net benefits. Table VI.K–2 shows the 

cost of the rule per case avoided. This 

table shows that cost per case avoided 

for the preferred alternative seems 

favorable when compared to the 

willingness to pay estimates. Additional 

information about this analysis and 

other methods of comparing benefits 

and costs can be found in the EA 

(USEPA 2005a). 

TABLE VI.K–2.—ESTIMATED COST PER DISCOUNTED CASED AVOIDED 1 FOR THE REGULATORY ALTERNATIVES, USING

TTHM AS DBP INDICATOR AND SMOKING/LUNG CANCER CESSATION LAG MODEL ($MILLIONS, 2003) 

Rule alternative 

Cost per case avoided 

3% 7% 

Preferred .................................................................................................................................................................. $ .033 $ .041 

Alternative 1 ............................................................................................................................................................. 1 .18 1 .42 

Alternative 2 ............................................................................................................................................................. 0 .52 0 .63 

Alternative 3 ............................................................................................................................................................. 0 .57 0 .69 

1The cost effectiveness ratios are a potentially a high estimate because regulatory costs in the numerator are not adjusted by subtracting the 

avoided medical costs associated with cases avoided to produce a net cost numerator. Subtraction of theses costs would not be expected to 

alter the ranking of alternatives. In the case where thresholds of maximum public expenditure per case avoided are prescribed, defining the numerator more precisely by making such adjustments would be appropriate. 

Notes: In reference to conducting incremental CEA, OMB states that analyst should make sure that ‘‘When constructing and comparing incremental cost-effectiveness ratios, [analysts] should make sure that inferior alternatives identified by the principles of strong and weak dominance 

are eliminated from consideration’’ (OMB Circular A–4, p. 10). Alternative 1 is dominated by the Preferred Alternative and is therefore not included in the incremental analysis. The reason for this domination is mainly that the Preferred Alternative includes IDSE and Alternative 1 does 

not; and to a lesser degree because the bromate control included in Alternative 1 increases the costs but the benefits of this control are not 

quantified at this time. Alternative 2 is compared directly to the Preferred Alternative (skipping Alternative 1) in this analysis. Cost per case avoided is in year 2003 dollars ($Millions), discounted for the 25 year analysis period to year 2005. 

Source: Exhibit 9.14, USEPA, 2005a. 

L. Summary of Major Comments 

EPA received significant public 

comment on the analysis of benefits and 

costs of the proposed Stage 2 DBPR in 

the following areas: interpretation of 

health effects studies, derivation of 

benefits, use of SWAT, illustrative 

example, unanticipated risk issues, and 

valuation of cancer cases avoided. The 

following discussion summarizes public 

comment in these areas and EPA’s 

responses. 

1. Interpretation of Health Effects 

Studies 

EPA requested comment on the 

conclusions of the cancer health effects 

section and the epidemiology and 

toxicology studies discussed. A number 

of comments questioned the overall 


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Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 465 

interpretation of the studies presented 

by EPA. A few comments pointed out 

missed studies. Commenters also asked 

about concordance between cancer 

epidemiology and toxicology. Some 

commenters also felt EPA did not 

discuss the broad range of risks from 

DBPs other than the ones regulated. 

The Agency continues to believe that, 

although there is not a causal link, the 

cancer literature points to an association 

between bladder cancer and potentially 

rectal and colon cancer and exposure to 

chlorinated surface water. EPA has 

included in today’s preamble the 

literature that commenters pointed out 

as missing and expands on its 

discussion of non-regulated DBPs. 

EPA believes that a lack of bladder 

cancer effect in toxicological studies 

does not negate the findings in 

epidemiological studies at this time. 

Tumor site concordance between 

human and test animal is not necessary 

to determine carcinogenic potential. 

While there is evidence from human 

cancer epidemiology studies that 

lifetime consumption of the DBP 

mixture within chlorinated surface 

water poses a bladder cancer risk, the 

specific causative constituents have not 

been identified. EPA will continue to 

evaluate new mode-of-action data as it 

becomes available. 

Several comments were received on 

EPA’s characterization of the literature 

on reproductive and developmental 

health risk. Some commenters wanted 

EPA to characterize reproductive and 

developmental health effects more 

strongly, stating that current research 

shows more evidence for these effects 

than described in the proposed 

preamble. Others thought that EPA’s 

characterization in the proposal was too 

strong, and that EPA had 

overemphasized these health concerns. 

Some commenters noted that certain 

published studies were missing from 

EPA’s risk discussion. 

EPA believes that the characterization 

of reproductive and developmental risks 

in the final Stage 2 DBPR preamble is 

appropriate based on the weight of 

evidence evaluation of the reproductive 

and developmental epidemiology 

database described in Section III.C. EPA 

considered comments and incorporated 

additional and recent studies into its 

characterization of health risks in 

today’s final preamble. While no causal 

link has been established, EPA’s 

evaluation of the available studies 

continues to indicate a potential health 

hazard that warrants additional 

regulatory action beyond the Stage 1 

DBPR. The inconsistencies and 

uncertainties remaining in the available 

science support the incremental nature 

of change in today’s rule. 

EPA did not include all findings from 

every study in the proposed DBPR 

preamble because the intent was to 

provide a summary overview and more 

importantly, the Agency’s conclusions 

regarding the weight of evidence. The 

epidemiology literature has 

inconsistencies in its findings on the 

relationship between various 

reproductive and developmental health 

effects and DBPs. In this final preamble, 

EPA describes how recent studies since 

the proposal further inform the 

perspective of overall risk from 

exposure to DBPs. EPA continues to 

believe that studies indicate a potential 

hazard. 

2. Derivation of Benefits 

EPA received numerous comments on 

the derivation of benefits from 

occurrence estimates for the Stage 2 

DBPR. The majority of the comments 

provided addressed EPA’s use of a 

cessation lag model to estimate the 

timing of benefits and a PAR analysis to 

estimate reduced risks. Several 

commenters opposed the cessation lag 

model proposed by EPA, suggesting that 

EPA use a longer cessation lag period or 

conduct a sensitivity analysis on the 

cessation lag exponent. 

In the effort to develop a cessation lag 

model specific to DBPs, EPA reviewed 

the available epidemiological literature 

for information relating to the timing of 

exposure and response, but could not 

identify any studies that could, alone or 

in combination, support a specific 

cessation lag model for DBPs in 

drinking water. Thus, in keeping with 

the SAB recommendation to consider 

other models in the absence of specific 

cessation lag information (USEPA 

2001d), EPA explored the use of 

information on other carcinogens that 

could be used to characterize the 

influence of cessation lag in calculating 

benefits. The benefit analysis for today’s 

rule uses three cessation lag models, 

which allows for a better 

characterization of uncertainty than did 

the approach used in the proposal. More 

details on this analysis are in the EA 

(USEPA 2005a). 

Additional comments were received 

on the use of PAR values derived from 

epidemiology studies to determine the 

number of bladder cancer cases 

attributable to DBP exposure. Some 

commenters remarked that there was 

not sufficient evidence in the 

epidemiology studies used to develop a 

reliable PAR estimate. A key issue 

expressed in the comments was that 

studies that developed the PAR 

estimates did not adequately control for 

confounders. One commenter supported 

EPA review of the Villanueva (2003) 

meta-analysis, stating that this was the 

best available data on the issue. 

EPA revised the methodology for 

calculating PAR values for bladder 

cancer associated with exposure to 

chlorinated drinking water by 

considering three different analytical 

approaches as described in Section 

V.B.2. EPA used the PAR values from all 

three approaches to estimate the number 

of bladder cancer cases ultimately 

avoided annually as a result of the Stage 

2 DBPR. Taken together, the three 

approaches provide a reasonable 

estimate of the range of potential risk. 

For simplicity, EPA used the Villanueva 

et al. (2003) study to calculate the 

annual benefits of the rule. The benefit 

estimates derived from Villanueva et al. 

(2003) capture a substantial portion of 

the overall range of results, reflecting 

the uncertainty in both the underlying 

OR and PAR values, as well as the 

uncertainty in DBP reductions for Stage 

2. More details on the PAR analysis can 

be found in the EA (USEPA 2005a). 

3. Use of SWAT 

Comments received on the use of 

SWAT for the compliance forecast 

claimed that the model probably 

underestimates DBP occurrence levels 

and hence underestimates compliance 

costs. Other commenters supported 

EPA’s occurrence estimation methods 

and results. Some commenters added 

that monitoring under the IDSE will 

produce different results than 

monitoring for the ICR and that SWAT 

did not capture these changes. 

EPA describes in detail the limitations 

of SWAT as well as all assumptions and 

uncertainties associated with the model 

in the EA published with today’s rule. 

EPA believes that, for the reasons stated 

below, the standard compliance forecast 

method using SWAT, as developed 

during the M-DBP FACA, provides a 

reasonable prediction of national 

treatment changes and resulting DBP 

levels anticipated for the Stage 2 DBPR: 

1. SWAT predictive equations for 

TTHM and HAA5 were calibrated to 

ICR-observed TTHM and HAA5 data. 

2. SWAT estimates are based on 12 

months of influent water quality data, 

treatment train information, and related 

characteristics for the 273 ICR surface 

water plants. EPA believes the ICR data 

provide a robust basis for the 

compliance forecast as it represents 

significant variability with respect to 

factors influencing DBP formation, 

including temperature, residence time, 

and geographical region. 

3. EPA uses a ‘‘delta’’ approach to 

reduce the impact of uncertainty in 


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466 Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 

SWAT’s predictive equations for TTHM 

and HAA5. Under this approach, EPA 1) 

estimates the difference in technology 

and TTHM and HAA5 concentration 

predictions between pre-Stage 1 and 

post-Stage 1; 2) estimates the difference 

in technology and TTHM and HAA5 

concentration predictions between preStage 1 and post-Stage 2; and 3) 

subtracts the result of the first estimate 

from the second estimate to predict the 

impacts between Stage 1 and Stage 2. 

Since each predictive estimate has bias 

in the same direction, EPA believes that 

this methodology minimized overall 

predictive error. 

In response to commenters concerns 

about potential uncertainties in the 

SWAT predictions, EPA also developed 

the ‘‘ICR Matrix Method.’’ The ICR 

Matrix Method uses TTHM and HAA5 

data from the ICR to estimate the 

percent of plants changing technology to 

comply with the Stage 2 DBPR and the 

resulting DBP reduction. The EA 

includes a detailed description of the 

ICR Matrix Method (USEPA 2005a). In 

the analysis for today’s rule, EPA gives 

equal weight to SWAT and ICR Matrix 

Method predictions in estimating Stage 

2 compliance forecasts and resultant 

reductions in DBP exposure. The ICR 

Matrix Method is also used to estimate 

reductions in the occurrence of peak 

TTHM and HAA5 concentrations 

because SWAT-predicted TTHM and 

HAA5 concentrations are valid only 

when considering national averages, not 

at the plant level. 

EPA revised the Stage 2 DBPR 

compliance forecast methodology to 

quantify the potential impacts of the 

IDSE for large and medium surface 

water systems. For these systems, EPA 

predicted compliance implications 

using a safety margin of both 20 and 25 

percent based on an analysis of spatial 

variability in TTHM and HAA5 

occurrence. EPA assigned equal 

probability to the 20 and 25 percent 

safety margins because both alternatives 

are considered equally plausible. These 

changes result in a wider uncertainty 

range for the compliance cost estimates 

than under the EA of the proposed rule. 

EPA assumes the 20 percent operational 

safety margin accounts for variability in 

small surface water systems and all 

ground water systems. Small systems 

are not expected to find significantly 

higher levels that affect their 

compliance as a result of the IDSE 

because their distribution systems are 

not as complex as large systems. 

Additionally, the IDSE is not expected 

to significantly impact the compliance 

forecast for ground water systems 

because they have more consistent 

source water quality and do not 

experience significant year-to-year 

variability in TTHM and HAA5 

occurrence. 

As some commenters noted, any 

underestimation in costs as a result of 

the compliance forecast is associated 

with an underestimation in the benefits. 

Accordingly, EPA adjusted both cost 

and benefits estimates based on the ICR 

Matrix Method and the impact of the 

IDSE for the upper end of the 

compliance forecast range. 

4. Illustrative Example 

Many comments were received on the 

illustrative calculation of fetal loss 

benefits included in the proposed EA. 

Many commenters recommended that 

EPA remove this calculation because of 

uncertainties in the underlying data. 

Other commenters, however, expressed 

support for this calculation because of 

the magnitude of potential benefits, and 

suggested that EPA include these 

benefits in its primary analysis. 

EPA believes that the reproductive 

and developmental epidemiologic data, 

although not conclusive, are suggestive 

of potential health effects in humans 

exposed to DBPs. EPA does not believe 

the available evidence provides an 

adequate basis for quantifying potential 

reproductive and developmental risks. 

Nevertheless, given the widespread 

nature of exposure to DBPs, the 

importance our society places on 

reproductive and developmental health, 

and the large number of fetal losses 

experienced each year in the U.S. 

(nearly 1 million), the Agency believes 

that it is appropriate to provide some 

quantitative indication of the potential 

risk suggested by some of the published 

results on reproductive and 

developmental endpoints, despite the 

absence of certainty regarding a causal 

link between disinfection byproducts 

and these risks and the inconsistencies 

between studies. However, the Agency 

is unable at this time to either develop 

a specific estimate of the value of 

avoiding fetal loss or to use a benefit 

transfer methodology to estimate the 

value from studies that address other 

endpoints. 

5. Unanticipated Risk Issues 

Comments were received that 

expressed concern about unanticipated 

risks that could result from the 

proposed Stage 2 DBPR. Several 

commenters remarked that regulation of 

TTHM and HAA5 would not control 

levels of other DBPs that may be more 

toxic than these indicator compounds, 

such as NDMA. Some commenters 

supported future research on the 

potential health effects of other DBPs. 

Other comments suggested that EPA 

further consider these risks when 

developing the final Stage 2 DBPR. 

EPA has addressed the occurrence of 

other DBPs in Section VI.H of this 

document and in the EA (USEPA 

2005a). Levels of some DBPs may 

increase because of treatment changes 

anticipated as a result of today’s rule. 

However, these DBPs generally occur at 

much lower levels than TTHM and 

HAA5, often more than an order of 

magnitude less (USEPA 2005f, Weinberg 

et al. 2002). For NDMA, studies have 

shown formation in both chlorinated 

and chloraminated systems (Barrett et 

al. 2003). The uncertainties surrounding 

NDMA formation make determinations 

regarding the impact of the Stage 2 

DBPR difficult. In addition, other routes 

of exposure appear to be more 

significant than drinking water. Dietary 

sources of NDMA include preserved 

meat and fish products, beer and 

tobacco. EPA is looking at calculating 

the relative source contribution of these 

routes of exposure compared to drinking 

water. 

EPA continues to support the use of 

TTHM and HAA5 as indicators for DBP 

regulation. The presence of TTHM and 

HAA5 is representative of the 

occurrence of many other chlorination 

DBPs; thus, a reduction in the TTHM 

and HAA5 generally indicates an overall 

reduction of DBPs. EPA also supports 

additional research on unregulated and 

unknown DBPs to ensure continual 

public health protection. 

6. Valuation of Cancer Cases Avoided 

A number of commenters remarked 

on the valuation of cancer cases 

avoided. Some commenters supported 

the use of value of statistical life (VSL) 

analysis in monetizing the benefits of 

fatal bladder cancer cases avoided. 

Comments were also received in 

support of the addition of expected 

medical costs for treating fatal bladder 

cancer cases to the VSL estimates. Other 

commenters recommended that EPA 

further review the use of willingness-topay estimates used to value the nonfatal cancer cases avoided. These 

comments stated concern over the 

similarity of bronchitis and lymphoma 

to bladder cancer and the resulting 

limitation of benefits transfer. 

EPA thanks commenters for 

expressing support of the use of VSL 

and valuation of fatal bladder cancer 

cases. EPA acknowledges that the 

willingness to pay (WTP) to avoid 

curable lymphoma or chronic bronchitis 

is not a perfect substitute for the WTP 

to avoid a case of non-fatal bladder 

cancer. However, non-fatal internal 

cancers, regardless of type, generally 

present patients with very similar 


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treatment, health, and long-term quality 

of life implications, including surgery, 

radiation or chemotherapy treatments 

(with attendant side effects), and 

generally diminished vitality over the 

duration of the illness. In the absence of 

more specific WTP studies, EPA 

believes the WTP values for avoiding a 

case of curable lymphoma or a case of 

chronic bronchitis provides a 

reasonable, though not definitive, 

substitute for the value of avoiding nonfatal bladder cancer. 

VII. Statutory and Executive Order 

Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review 

Under Executive Order 12866, [58 FR 

51735, (October 4, 1993)] the Agency 

must determine whether the regulatory 

action is ‘‘significant’’ and therefore 

subject to OMB review and the 

requirements of the Executive Order. 

The Order defines ‘‘significant 

regulatory action’’ as one that is likely 

to result in a rule that may: 

(1) Have an annual effect on the 

economy of $100 million or more or 

adversely affect in a material way the 

economy, a sector of the economy, 

productivity, competition, jobs, the 

environment, public health or safety, or 

State, local, or Tribal governments or 

communities; 

(2) Create a serious inconsistency or 

otherwise interfere with an action taken 

or planned by another agency; 

(3) Materially alter the budgetary 

impact of entitlements, grants, user fees, 

or loan programs or the rights and 

obligations of recipients thereof; or 

(4) Raise novel legal or policy issues 

arising out of legal mandates, the 

President’s priorities, or the principles 

set forth in the Executive Order. 

Pursuant to the terms of Executive 

Order 12866, it has been determined 

that this rule is a ‘‘significant regulatory 

action.’’ As such, this action was 

submitted to OMB for review. Changes 

made in response to OMB suggestions or 

recommendations will be documented 

in the public record. 

B. Paperwork Reduction Act 

The Office of Management and Budget 

(OMB) has approved the information 

collection requirements contained in 

this rule under the provisions of the 

Paperwork Reduction Act, 44 U.S.C. 

3501 et seq. and has assigned OMB 

control number 2040–0265 (USEPA 

2005n). 

The information collected as a result 

of this rule will allow the States and 

EPA to determine appropriate 

requirements for specific systems, and 

to evaluate compliance with the rule. 

For the first three years after Stage 2 

DBPR promulgation, the major 

information requirements involve 

monitoring activities, which include 

conducting the IDSE and submission of 

the IDSE report, and tracking 

compliance. The information collection 

requirements are mandatory (Part 141), 

and the information collected is not 

confidential. 

The estimate of annual average 

burden hours for the Stage 2 DBPR for 

systems and States is 228,529 hours. 

This estimate covers the first three years 

of the Stage 2 DBPR and most of the 

IDSE (small system reports are not due 

until the fourth year). The annual 

average aggregate cost estimate is $9.8 

million for operation and maintenance 

as a purchase of service for lab work and 

$6.6 million is associated with labor. 

The annual burden hour per response is 

4.18 hours. The frequency of response 

(average responses per respondent) is 

7.59 annually. The estimated number of 

likely respondents is 7,202 per year (the 

product of burden hours per response, 

frequency, and respondents does not 

total the annual average burden hours 

due to rounding). Because disinfecting 

systems have already purchased basic 

monitoring equipment to comply with 

the Stage 1 DBPR, EPA assumes no 

capital start-up costs are associated with 

the Stage 2 DBPR ICR. 

Burden means the total time, effort, or 

financial resources expended by persons 

to generate, maintain, retain, or disclose 

or provide information to or for a 

Federal agency. This includes the time 

needed to review instructions; develop, 

acquire, install, and utilize technology 

and systems for the purposes of 

collecting, validating, and verifying 

information, processing and 

maintaining information, and disclosing 

and providing information; adjust the 

existing ways to comply with any 

previously applicable instructions and 

requirements; train personnel to be able 

to respond to a collection of 

information; search data sources; 

complete and review the collection of 

information; and transmit or otherwise 

disclose the information. 

An agency may not conduct or 

sponsor, and a person is not required to 

respond to a collection of information 

unless it displays a currently valid OMB 

control number. The OMB control 

numbers for EPA’s regulations in 40 

CFR are listed in 40 CFR part 9. In 

addition, EPA is amending the table in 

40 CFR part 9 of currently approved 

OMB control numbers for various 

regulations to list the regulatory 

citations for the information 

requirements contained in this final 

rule. 

C. Regulatory Flexibility Act 

The Regulatory Flexibility Act (RFA) 

generally requires an agency to prepare 

a regulatory flexibility analysis for any 

rule subject to notice and comment 

rulemaking requirements under the 

Administrative Procedure Act or other 

statute unless the agency certifies that 

the rule will not have a significant 

economic impact on a substantial 

number of small entities. Small entities 

include small businesses, small 

organizations, and small governmental 

jurisdictions. 

The RFA provides default definitions 

for each type of small entity. Small 

entities are defined as: (1) A small 

business as defined by the Small 

Business Administrations’s (SBA) 

regulations at 13 CFR 121.201; (2) a 

small governmental jurisdiction that is a 

government of a city, county, town, 

school district or special district with a 

population of less than 50,000; and (3) 

a small organization that is any ‘‘not-forprofit enterprise which is independently 

owned and operated and is not 

dominant in its field.’’ However, the 

RFA also authorizes an agency to use 

alternative definitions for each category 

of small entity, ‘‘which are appropriate 

to the activities of the agency’’ after 

proposing the alternative definition(s) in 

the Federal Register and taking 

comment. 5 U.S.C. 601(3)–(5). In 

addition, to establish an alternative 

small business definition, agencies must 

consult with SBA’s Chief Council for 

Advocacy. 

For purposes of assessing the impacts 

of today’s rule on small entities, EPA 

considered small entities to be public 

water systems serving 10,000 or fewer 

persons. As required by the RFA, EPA 

proposed using this alternative 

definition in the Federal Register (63 FR 

7620, February 13, 1998), requested 

public comment, consulted with the 

Small Business Administration (SBA), 

and finalized the alternative definition 

in the Consumer Confidence Reports 

regulation (63 FR 44511, August 19, 

1998). As stated in that Final Rule, the 

alternative definition is applied to this 

regulation as well. 

After considering the economic 

impacts of today’s final rule on small 

entities, I certify that this action will not 

have a significant economic impact on 

a substantial number of small entities. 

The small entities regulated by this final 

rule are PWSs serving fewer than 10,000 

people. We have determined that 92 

small surface water and ground water 

under the direct influence of surface 

water (GWUDI) systems (or 2.16% of all 


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small surface water and GWUDI systems 

affected by the Stage 2 DBPR) will 

experience an impact of 1% or greater 

of average annual revenues. Of the 92, 

40 small surface water and GWUDI 

systems (or 0.94% of all small surface 

water and GWUDI systems affected by 

the Stage 2 DBPR) will experience an 

impact of 3% or greater of average 

annual revenues. Further, 354 small 

ground water systems (or 1.02% of all 

small ground water systems affected by 

the Stage 2 DBPR) will experience an 

impact of 1% or greater of average 

annual revenues. Of the 354, 45 small 

ground water systems (or 0.13% of all 

small ground water systems affected by 

the Stage 2 DBPR) will experience an 

impact of 3% or greater of average 

annual revenues. 

Although this final rule will not have 

a significant economic impact on a 

substantial number of small entities, 

EPA nonetheless has tried to reduce the 

impact of this rule on small entities. The 

Stage 2 DBPR contains a number of 

provisions to minimize the impact of 

the rule on systems generally, and on 

small systems in particular. For 

example, small systems have a longer 

time frame to comply with requirements 

than large systems (see § 141.600(c) and 

§ 141.620(c)). The final rule determines 

monitoring frequency based on 

population rather than plant-based 

monitoring requirements (see § 141.605 

and § 141.621(a)) as proposed. Small 

systems will also have to take fewer 

samples than large systems due to the 

40/30 waiver (see § 141.603(a)), for 

which small, ground water systems are 

expected to be able to qualify, and the 

very small system waiver (see 

§ 141.604). 

Funding may be available from 

programs administered by EPA and 

other Federal agencies to assist small 

PWSs in complying with the Stage 2 

DBPR. The Drinking Water State 

Revolving Fund (DWSRF) assists PWSs 

with financing the costs of 

infrastructure needed to achieve or 

maintain compliance with SDWA 

requirements. Through the DWSRF, 

EPA awards capitalization grants to 

States, which in turn can provide lowcost loans and other types of assistance 

to eligible PWSs. Loans made under the 

program can have interest rates between 

0 percent and market rate and 

repayment terms of up to 20 years. 

States prioritize funding based on 

projects that address the most serious 

risks to human health and assist PWSs 

most in need. Congress provided the 

DWSRF program $8 billion for fiscal 

years 1997 through 2004. 

The DWSRF places an emphasis on 

small and disadvantaged communities. 

States must provide a minimum of 15% 

of the available funds for loans to small 

communities. A State has the option of 

providing up to 30% of the grant 

awarded to the State to furnish 

additional assistance to State-defined 

disadvantaged communities. This 

assistance can take the form of lower 

interest rates, principal forgiveness, or 

negative interest rate loans. The State 

may also extend repayment terms of 

loans for disadvantaged communities to 

up to 30 years. A State can set aside up 

to 2% of the grant to provide technical 

assistance to PWSs serving communities 

with populations fewer than 10,000. 

In addition to the DWSRF, money is 

available from the Department of 

Agriculture’s Rural Utility Service 

(RUS) and Housing and Urban 

Development’s Community 

Development Block Grant (CDBG) 

program. RUS provides loans, 

guaranteed loans, and grants to improve, 

repair, or construct water supply and 

distribution systems in rural areas and 

towns of up to 10,000 people. In fiscal 

year 2003, RUS had over $1.5 billion of 

available funds for water and 

environmental programs. The CDBG 

program includes direct grants to States, 

which in turn are awarded to smaller 

communities, rural areas, and colon ̃ as in 

Arizona, California, New Mexico, and 

Texas and direct grants to U.S. 

territories and trusts. The CDBG budget 

for fiscal year 2003 totaled over $4.4 

billion. 

Although not required by the RFA to 

convene a Small Business Advocacy 

Review (SBAR) Panel because EPA 

determined that the proposed rule 

would not have a significant economic 

impact on a substantial number of small 

entities, EPA did convene a panel to 

obtain advice and recommendations 

from representatives of the small 

entities potentially subject to this rule’s 

requirements. For a description of the 

SBAR Panel and stakeholder 

recommendations, please see the 

proposed rule (USEPA 2003a). 

D. Unfunded Mandates Reform Act 

Title II of the Unfunded Mandates 

Reform Act of 1995 (UMRA), Public 

Law 104–4, establishes requirements for 

Federal agencies to assess the effects of 

their regulatory actions on State, local, 

and Tribal governments and the private 

sector. Under section 202 of the UMRA, 

EPA generally must prepare a written 

statement, including a cost-benefit 

analysis, for proposed and final rules 

with ‘‘Federal mandates’’ that may 

result in expenditures to State, local and 

Tribal governments, in the aggregate, or 

to the private sector, of $100 million or 

more in any one year. Before 

promulgating an EPA rule for which a 

written statement is needed, section 205 

of the UMRA generally requires EPA to 

identify and consider a reasonable 

number of regulatory alternatives and 

adopt the least costly, most costeffective or least burdensome alternative 

that achieves the objectives of the rule. 

The provisions of section 205 do not 

apply when they are inconsistent with 

applicable law. Moreover, section 205 

allows EPA to adopt an alternative other 

than the least costly, most cost-effective 

or least burdensome alternative if the 

Administrator publishes with the final 

rule an explanation why that alternative 

was not adopted. Before EPA establishes 

any regulatory requirements that may 

significantly or uniquely affect small 

governments, including Tribal 

governments, it must have developed 

under section 203 of the UMRA a small 

government agency plan. The plan must 

provide for notifying potentially 

affected small governments, enabling 

officials of affected small governments 

to have meaningful and timely input in 

the development of EPA regulatory 

proposals with significant Federal 

intergovernmental mandates, and 

informing, educating, and advising 

small governments on compliance with 

the regulatory requirements. 

EPA has determined that this rule 

may contain a Federal mandate that 

results in expenditures of $100 million 

or more for the State, Local, and Tribal 

governments, in the aggregate in the 

private sector in any one year. While the 

annualized costs fall below the $100 

million threshold, the costs in some 

future years may be above the $100 

million mark as public drinking water 

systems make capital investments and 

finance these through bonds, loans, and 

other means. EPA’s year by year cost 

tables do not reflect that investments 

through bonds, loans, and other means 

spread out these costs over many years. 

The cost analysis in general does not 

consider that some systems may be 

eligible for financial assistance such as 

low-interest loans and grants through 

such programs as the Drinking Water 

State Revolving Fund. 

As noted earlier, today’s final rule is 

promulgated pursuant to section 1412 

(b)(1)(A) of the Safe Drinking Water Act 

(SDWA), as amended in 1996, which 

directs EPA to promulgate a national 

primary drinking water regulation for a 

contaminant if EPA determines that the 

contaminant may have an adverse effect 

on the health of persons, occurs in 

PWSs with a frequency and at levels of 

public health concern, and regulation 

presents a meaningful opportunity for 

health risk reduction. 


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Section VI of this preamble discusses 

the cost and benefits associated with the 

Stage 2 DBPR. Details are presented in 

the Economic Analysis (USEPA 2005a). 

TABLE VII.D–1—PUBLIC AND PRIVATE COSTS FOR THE STAGE 2 DBPR (ANNUALIZED AT 3 AND 7 PERCENT, $MILLIONS) 

3% discount rate 7% discount rate 

Percent of 3% 

grand total costs 

(percent) 

Percent of 7% 

grand total costs 

(percent) 

Surface Water Systems Costs ................................................ $41.4 $41.2 53 54 

Ground Water Systems Costs ................................................. 20.3 19.2 26 25 

State Costs .............................................................................. 1.7 1.7 2 2 

Tribal Costs .............................................................................. 0.4 0.4 1 0 

Total Public ....................................................................... 63.8 62.5 81 81 

Surface Water Systems Costs ................................................ 6.4 6.3 8 8 

Ground Water Systems Costs ................................................. 8.5 8.0 11 10 

Total Private ..................................................................... 15.0 14.3 19 19 

Grand total ................................................................. 78.8 76.8 100 100 

Note: Detail may not add due to independent rounding. Estimates are discounted to 2003 and given in 2003 dollars. 

Source: Exhibits 3.2 and 7.5, USEPA 2005a. 

To meet the UMRA requirement in 

section 202, EPA analyzed future 

compliance costs and possible 

disproportionate budgetary effects. The 

Agency believes that the cost estimates 

and regulatory alternatives indicated 

earlier and discussed in more detail in 

section VI of this preamble, accurately 

characterize future compliance costs of 

today’s rule. 

In analyzing disproportionate 

impacts, EPA considered the impact on 

(1) different regions of the United States, 

(2) State, local, and Tribal governments, 

(3) urban, rural and other types of 

communities, and (4) any segment of the 

private sector. This analysis is presented 

in Chapter 7of the Economic Analysis 

(USEPA 2005a). EPA analyzed four 

regulatory alternatives and selected the 

least costly of these in accordance with 

UMRA Section 205. 

EPA has determined that the Stage 2 

DBPR contains no regulatory 

requirements that might significantly or 

uniquely affect small governments. The 

Stage 2 DBPR affects all size systems. As 

described in section VII.C, EPA has 

certified that today’s rule will not have 

a significant economic impact on a 

substantial number of small entities. 

Average annual expenditures for small 

CWSs to comply with the Stage 2 DBPR 

range from $27.7 to $26.1 million at a 

3 and 7 percent discount rate, 

respectively. 

Consistent with the intergovernmental 

consultation provisions of section 204 of 

the UMRA and Executive Order 12875, 

‘‘Enhancing the Intergovernmental 

Partnership,’’ EPA has already initiated 

consultations with the governmental 

entities affected by this rule. The 

consultations are described in the 

proposed rule (68 FR 49654, August 18, 

2003). 

E. Executive Order 13132: Federalism 

Executive Order 13132, entitled 

‘‘Federalism’’ (64 FR 43255, August 10, 

1999), requires EPA to develop an 

accountable process to ensure 

‘‘meaningful and timely input by State 

and local officials in the development of 

regulatory policies that have federalism 

implications.’’ ‘‘Policies that have 

federalism implications’’ is defined in 

the Executive Order to include 

regulations that have ‘‘substantial direct 

effects on the States, on the relationship 

between the national government and 

the States, or on the distribution of 

power and responsibilities among the 

various levels of government.’’

This final rule does not have 

federalism implications. It will not have 

substantial direct effects on the States, 

on the relationship between national 

government and the States, or on the 

distribution of power and 

responsibilities among various levels of 

government, as specified in Executive 

Order 13132. The final rule has onetime costs for implementation of 

approximately $7.8 million. Thus, 

Executive Order 13132 does not apply 

to this rule. 

Although section 6 of Executive Order 

13132 does not apply to this rule, in the 

spirit of Executive Order 13132, and 

consistent with EPA policy to promote 

communications between EPA and State 

and local governments, EPA nonetheless 

specifically solicited comment on the 

proposed rule from State and local 

officials and did consult with State and 

local officials in developing this rule. A 

description of that consultation can be 

found in the preamble to the proposed 

rule, 68 FR 49548, (August 18, 2003). 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

Executive Order 13175, entitled 

‘‘Consultation and Coordination with 

Indian Tribal Governments’’ (65 FR 

67249, November 9, 2000), requires EPA 

to develop ‘‘an accountable process to 

ensure meaningful and timely input by 

tribal officials in the development of 

regulatory policies that have tribal 

implications.’’ Under Executive Order 

13175, EPA may not issue a regulation 

that has Tribal implications, that 

imposes substantial direct compliance 

costs, and that is not required by statute, 

unless the Federal government provides 

the funds necessary to pay the direct 

compliance costs incurred by Tribal 

governments, or EPA consults with 

Tribal officials early in the process of 

developing the proposed regulation and 

develops a Tribal summary impact 

statement. 

EPA has concluded that this final rule 

may have Tribal implications, because it 

may impose substantial direct 

compliance costs on Tribal 

governments, and the Federal 

government will not provide the funds 

necessary to pay those costs. 

Accordingly, EPA provides the 

following Tribal summary impact 

statement as required by section 5(b). 

EPA provides further detail on Tribal 

impact in the Economic Analysis 

(USEPA 2005a). Total Tribal costs are 

estimated to be approximately $391,773 

per year (at a 3 percent discount rate) 

and this cost is distributed across 755 

Tribal systems. The cost for individual 

systems depend on system size and 

source water type. Of the 755 Tribes that 

may be affected in some form by the 

Stage 2 DBPR, 654 use ground water as 

a source and 101 systems use surface 

water or GWUDI. Since the majority of 

Tribal systems are ground water systems 


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470 Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 

serving fewer than 500 people, 

approximately 15.6 percent of all Tribal 

systems will have to conduct an IDSE. 

As a result, the Stage 2 DBPR is most 

likely to have an impact on Tribes using 

surface water or GWUDI serving more 

than 500 people. 

EPA consulted with Tribal officials 

early in the process of developing this 

regulation to permit them to have 

meaningful and timely input into its 

development. Moreover, in the spirit of 

Executive Order 13175, and consistent 

with EPA policy to promote 

communications between EPA and 

Tribal governments, EPA specifically 

solicited comment on the proposed rule 

from Tribal officials. 

As required by section 7(a), EPA’s 

Tribal Consultation Official has certified 

that the requirements of the Executive 

Order has been met in a meaningful and 

timely manner. A copy of this 

certification has been included in the 

docket for this rule. 

G. Executive order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

Executive Order 13045: ‘‘Protection of 

Children from Environmental Health 

Risks and Safety Risks’’ (62 FR 19885, 

April 23, 1997) applies to any rule that: 

(1) is determined to be ‘‘economically 

significant’’ as defined under 12866, 

and; (2) concerns an environmental 

health or safety risk that EPA has reason 

to believe may have a disproportionate 

effect on children. If the regulatory 

action meets both criteria, the Agency 

must evaluate the environmental health 

or safety effects of the planned rule on 

children, and explain why the planned 

regulation is preferable to other 

potentially effective and reasonably 

feasible alternatives considered by the 

Agency. 

While this final rule is not subject to 

the Executive Order because it is not 

economically significant as defined in 

Executive Order 12866, EPA 

nonetheless has reason to believe that 

the environmental health or safety risk 

(i.e., the risk associated with DBPs) 

addressed by this action may have a 

disproportionate effect on children. EPA 

believes that the Stage 2 DBPR will 

result in greater risk reduction for 

children than for the general 

population. The results of the 

assessments are contained in Section 

VI.I of this preamble and in the 

Economic Analysis (USEPA 2005a). A 

copy of all documents has been placed 

in the public docket for this action. 

H. Executive Order 13211: Actions 

Concerning Regulations That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This rule is not a ‘‘significant energy 

action’’ as defined in Executive Order 

13211, ‘‘Actions Concerning Regulations 

That Significantly Affect Energy Supply, 

Distribution, or Use’’ (66 FR 28355, May 

22, 2001) because it is not likely to have 

a significant adverse effect on the 

supply, distribution, or use of energy. 

This determination is based on the 

following analysis. 

The first consideration is whether the 

Stage 2 DBPR would adversely affect the 

supply of energy. The Stage 2 DBPR 

does not regulate power generation, 

either directly or indirectly. The public 

and private utilities that the Stage 2 

DBPR regulates do not, as a rule, 

generate power. Further, the cost 

increases borne by customers of water 

utilities as a result of the Stage 2 DBPR 

are a low percentage of the total cost of 

water, except for a very few small 

systems that might install advanced 

technologies that must spread that cost 

over a narrow customer base. Therefore, 

the customers that are power generation 

utilities are unlikely to face any 

significant effects as a result of the Stage 

2 DBPR. In sum, the Stage 2 DBPR does 

not regulate the supply of energy, does 

not generally regulate the utilities that 

supply energy, and is unlikely 

significantly to affect the customer base 

of energy suppliers. Thus, the Stage 2 

DBPR would not translate into adverse 

effects on the supply of energy. 

The second consideration is whether 

the Stage 2 DBPR would adversely affect 

the distribution of energy. The Stage 2 

DBPR does not regulate any aspect of 

energy distribution. The utilities that are 

regulated by the Stage 2 DBPR already 

have electrical service. As derived later 

in this section, the final rule is projected 

to increase peak electricity demand at 

water utilities by only 0.009 percent. 

Therefore, EPA estimates that the 

existing connections are adequate and 

that the Stage 2 DBPR has no 

discernable adverse effect on energy 

distribution. 

The third consideration is whether 

the Stage 2 DBPR would adversely affect 

the use of energy. Because some 

drinking water utilities are expected to 

add treatment technologies that use 

electrical power, this potential impact is 

evaluated in more detail. The analyses 

that underlay the estimation of costs for 

the Stage 2 DBPR are national in scope 

and do not identify specific plants or 

utilities that may install treatment in 

response to the rule. As a result, no 

analysis of the effect on specific energy 

suppliers is possible with the available 

data. The approach used to estimate the 

impact of energy use, therefore, focuses 

on national-level impacts. The analysis 

estimates the additional energy use due 

to the Stage 2 DBPR and compares that 

analysis to the national levels of power 

generation in terms of average and peak 

loads. 

The first step in the analysis is to 

estimate the energy used by the 

technologies expected to be installed as 

a result of the Stage 2 DBPR. Energy use 

is not directly stated in Technologies 

and Costs for the Final Long Term 2 

Enhanced Surface Water Treatment Rule 

and Final Stage 2 Disinfectants and 

Disinfection Byproducts Rule (USEPA 

2005g), but the annual cost of energy for 

each technology addition or upgrade 

necessitated by the Stage 2 DBPR is 

provided. An estimate of plant-level 

energy use is derived by dividing the 

total energy cost per plant for a range of 

flows by an average national cost of 

electricity of $0.076/ kilowatt hours per 

year (kWh/yr) (USDOE 2004a). These 

calculations are shown in detail in the 

Economic Analysis (USEPA 2005a). The 

energy use per plant for each flow range 

and technology is then multiplied by 

the number of plants predicted to install 

each technology in a given flow range. 

The energy requirements for each flow 

range are then added to produce a 

national total. No electricity use is 

subtracted to account for the 

technologies that may be replaced by 

new technologies, resulting in a 

conservative estimate of the increase in 

energy use. The incremental national 

annual energy usage is 0.12 million 

megawatt-hours (MWh). 

According to the U.S. Department of 

Energy’s Information Administration, 

electricity producers generated 3,848 

million MWh of electricity in 2003 

(USDOE 2004b). Therefore, even using 

the highest assumed energy use for the 

Stage 2 DBPR, the rule when fully 

implemented would result in only a 

0.003 percent increase in annual average 

energy use. 

In addition to average energy use, the 

impact at times of peak power demand 

is important. To examine whether 

increased energy usage might 

significantly affect the capacity margins 

of energy suppliers, their peak season 

generating capacity reserve was 

compared to an estimate of peak 

incremental power demand by water 

utilities. 

Both energy use and water use peak 

in the summer months, so the most 

significant effects on supply would be 

seen then. In the summer of 2003, U.S. 

generation capacity exceeded 

consumption by 15 percent, or 


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approximately 160,000 MW (USDOE 

2004b). Assuming around-the-clock 

operation of water treatment plants, the 

total energy requirement can be divided 

by 8,760 hours per year to obtain an 

average power demand of 13.28 MW. A 

more detailed derivation of this value is 

shown in the Economic Analysis 

(USEPA 2005a). Assuming that power 

demand is proportional to water flow 

through the plant and that peak flow 

can be as high as twice the average daily 

flow during the summer months, about 

26.55 MW could be needed for 

treatment technologies installed to 

comply with the Stage 2 DBPR. This is 

only 0.017 percent of the capacity 

margin available at peak use. 

Although EPA recognizes that not all 

areas have a 15 percent capacity margin 

and that this margin varies across 

regions and through time, this analysis 

reflects the effect of the rule on national 

energy supply, distribution, and use. 

While certain areas, notably California, 

have experienced shortfalls in 

generating capacity in the recent past, a 

peak incremental power requirement of 

26.55 MW nationwide is not likely to 

significantly change the energy supply, 

distribution, or use in any given area. 

Considering this analysis, EPA has 

concluded that Stage 2 DBPR will not 

have any significant effect on the use of 

energy, based on annual average use and 

on conditions of peak power demand. 

I. National Technology Transfer and 

Advancement Act 

As noted in the proposed rule, 

Section 12(d) of the National 

Technology Transfer and Advancement 

Act of 1995 (‘‘NTTAA’’), Public Law 

104–113, section 12(d) (15 U.S.C. 272 

note) directs EPA to use voluntary 

consensus standards in its regulatory 

activities unless to do so would be 

inconsistent with applicable law or 

otherwise impractical. Voluntary 

consensus standards are technical 

standards (e.g., materials specifications, 

test methods, sampling procedures, and 

business practices) that are developed or 

adopted by voluntary consensus 

standard bodies. The NTTAA directs 

EPA to provide Congress, through OMB, 

explanations when the Agency decides 

not to use available and applicable 

voluntary consensus standards. 

This rulemaking involves technical 

standards. EPA has decided to use two 

voluntary consensus methods for HAA5 

(Standard Method 6251 B, 1998 in the 

20th Edition of Standard Methods for 

the Examination of Water and 

Wastewater and Standard Method 6251 

B–94, 1994 available at http:// 

www.standardmethods.org). In addition 

to these two consensus methods, EPA is 

also approving EPA Method 552.3 for 

HAA5, which also can be used to 

measure three unregulated HAAs that 

are not included in the consensus 

methods. The unregulated HAAs are 

included in the EPA method because 

some water systems monitor for them in 

order to better understand their 

treatment processes and provide greater 

public health protection. EPA is 

approving two voluntary consensus 

standards for daily monitoring for 

chlorite (Standard Method 4500–ClO2 E, 

1998, in the 20th Edition of Standard 

Methods for the Examination of Water 

and Wastewater and Standard Method 

4500–ClO2 E–00, 2000, available at 

http://www.standardmethods.org). EPA 

Method 327.0, Revision 1.1 is also being 

approved for daily monitoring for both 

chlorite and chlorine dioxide in order to 

provide an alternative to the titration 

procedure that is required in the 

Standard Methods. EPA is approving a 

method from American Society for 

Testing and Materials International for 

bromate, chlorite and bromide analyses 

(ASTM D 6581–00, 2000, ASTM 

International. Annual Book of ASTM 

Standards, Volume 11.01, American 

Society for Testing and Materials 

International, 2001 or any year 

containing the cited version of the 

method may be used). EPA is also 

approving three EPA methods (EPA 

Methods 317.0 Revision 2.0, 321.8, and 

326.0) that provide greater sensitivity 

and selectivity for bromate than the 

ASTM consensus standard. These EPA 

methods are required in order to 

provide better process control for water 

systems using ozone in the treatment 

process and to allow for a reduced 

monitoring option. EPA Methods 317.0 

Revision 2.0 and 326.0 can also be used 

to determine chlorite and bromide. 

Today’s action approves eight voluntary 

consensus standards for determining 

free, combined, and total chlorine (SM 

4500–Cl D, SM 4500–Cl F, and 4500–Cl 

G, 1998, in the 20th Edition of Standard 

Methods for the Examination of Water 

and Wastewater and SM 4500–Cl D–00, 

SM 4500–Cl F–00, and 4500–Cl G–00, 

2000 available at http:// 

www.standardmethods.org and ASTM D 

1253–86(96), 1996, ASTM International, 

Annual Book of ASTM Standards, 

Volume 11.01, American Society for 

Testing and Materials International, 

1996 or any year containing the cited 

version of the method may be used and 

ASTM D 1253–03, 2003, ASTM 

International, Annual Book of ASTM 

Standards, Volume 11.01, American 

Society for Testing and Materials 

International, 2004 or any year 

containing the cited version of the 

method may be used). EPA is approving 

four standards for determining total 

chlorine (SM 4500–Cl E and SM 4500–

Cl I, 1998, in the 20th Edition of 

Standard Methods for the Examination 

of Water and Wastewater and SM 4500–

Cl E–00 and SM 4500–Cl I–00, 2000 

available at http:// 

www.standardmethods.org). Two 

standards for determining free chlorine 

are approved in today’s rule (SM 4500–

Cl H, 1998, in the 20th Edition of 

Standard Methods for the Examination 

of Water and Wastewater and SM 4500–

Cl H–00, 2000 available at http:// 

www.standardmethods.org). Today’s 

action approves three voluntary 

consensus standards for measuring 

chlorine dioxide (4500–ClO2 D and 

4500–ClO2 E, 1998, in the 20th Edition 

of Standard Methods for the 

Examination of Water and Wastewater 

and 4500–ClO2 E–00, 2000 available at 

http://www.standardmethods.org). EPA 

is approving six standards for 

determining TOC and DOC (SM 5310 B, 

SM 5310 C, and SM 5310 D, 1998, in the 

20th Edition of Standard Methods for 

the Examination of Water and 

Wastewater and SM 5310 B–00, SM 

5310 C–00, and SM 5310 D–00, 2000 

available at http:// 

www.standardmethods.org). Two 

standards for determining UV254 are 

approved in today’s rule (SM 5910 B, 

1998, in the 20th Edition of Standard 

Methods for the Examination of Water 

and Wastewater and SM 5910 B–00, 

2000 available at http:// 

www.standardmethods.org). EPA is also 

approving EPA Method 415.3 Revision 

1.1 for the determination of TOC and 

SUVA (DOC and UV254). This EPA 

method contains method performance 

data that are not available in the 

consensus standards. 

Copies of the ASTM standards may be 

obtained from the American Society for 

Testing and Materials International, 100 

Barr Harbor Drive, West Conshohocken, 

PA 19428–2959. The Standard Methods 

may be obtained from the American 

Public Health Association, 1015 

Fifteenth Street, NW., Washington, DC 

20005. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations or LowIncome Populations 

Executive Order 12898 establishes a 

Federal policy for incorporating 

environmental justice into Federal 

agency missions by directing agencies to 

identify and address disproportionately 

high and adverse human health or 

environmental effects of its programs, 

policies, and activities on minority and 

low-income populations. EPA has 


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472 Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 

considered environmental justice 

related issues concerning the potential 

impacts of this action and consulted 

with minority and low-income 

stakeholders. A description of this 

consultation can be found in the 

proposed rule (USEPA 2003a). 

K. Consultations With the Science 

Advisory Board, National Drinking 

Water Advisory Council, and the 

Secretary of Health and Human Services 

In accordance with Section 1412(d) 

and (e) of the SDWA, the Agency 

consulted with the Science Advisory 

Board, the National Drinking Water 

Advisory Council (NDWAC), and the 

Secretary of Health and Human Services 

on today’s rule. 

EPA met with the SAB to discuss the 

Stage 2 DBPR on June 13, 2001 

(Washington, DC), September 25–26, 

2001 (teleconference), and December 

10–12, 2001 (Los Angeles, CA). Written 

comments from the December 2001 

meeting of the SAB addressing the 

occurrence analysis and risk assessment 

were generally supportive. SAB 

comments are discussed in greater detail 

within the proposal. 

EPA met with the NDWAC on 

November 8, 2001, in Washington, DC 

to discuss the Stage 2 DBPR proposal. 

The Advisory Committee generally 

supported the need for the Stage 2 DBPR 

based on health and occurrence data, 

but also stressed the importance of 

providing flexibility to the systems 

implementing the rule. The results of 

these discussions are included in the 

docket for the proposed rule. 

L. Plain Language 

Executive Order 12866 requires each 

agency to write its rules in plain 

language. Readable regulations help the 

public find requirements quickly and 

understand them easily. They increase 

compliance, strengthen enforcement, 

and decrease mistakes, frustration, 

phone calls, appeals, and distrust of 

government. EPA made every effort to 

write this preamble to the final rule in 

as clear, concise, and unambiguous 

manner as possible. 

M. Analysis of the Likely Effect of 

Compliance With the Stage 2 DBPR on 

the Technical, Managerial, and 

Financial Capacity of Public Water 

Systems 

Section 1420(d)(3) of SDWA, as 

amended, requires that, in promulgating 

a National Primary Drinking Water 

Regulation (NPDWR), the Administrator 

shall include an analysis of the likely 

effect of compliance with the regulation 

on the technical, managerial, and 

financial (TMF) capacity of PWSs. This 

analysis is described in more detail and 

can be found in the Economic Analysis 

(USEPA 2005a). Analyses reflect only 

the impact of new or revised 

requirements, as established by the 

LT2ESWTR; the impacts of previously 

established requirements on system 

capacity are not considered. 

EPA has defined overall water system 

capacity as the ability to plan for, 

achieve, and maintain compliance with 

applicable drinking water standards. 

Capacity encompasses three 

components: technical, managerial, and 

financial. Technical capacity is the 

physical and operational ability of a 

water system to meet SDWA 

requirements. This refers to the physical 

infrastructure of the water system, 

including the adequacy of source water 

and the adequacy of treatment, storage, 

and distribution infrastructure. It also 

refers to the ability of system personnel 

to adequately operate and maintain the 

system and to otherwise implement 

requisite technical knowledge. 

Managerial capacity is the ability of a 

water system to conduct its affairs to 

achieve and maintain compliance with 

SDWA requirements. Managerial 

capacity refers to the system’s 

institutional and administrative 

capabilities. Financial capacity is a 

water system’s ability to acquire and 

manage sufficient financial resources to 

allow the system to achieve and 

maintain compliance with SDWA 

requirements. 

EPA estimated the impact of the Stage 

2 DBPR on small and large system 

capacity as a result of the measures that 

systems are expected to adopt to meet 

the requirements of the rule (e.g., 

selecting monitoring sites for the IDSE, 

installing/upgrading treatment, operator 

training, communication with regulators 

and the service community, etc.). The 

Stage 2 DBPR may have a substantial 

impact on the capacity of the 1,743 

plants in small systems and 518 plants 

in large systems that must make changes 

to their treatment process to meet the 

Stage 2 DBPR requirements. However, 

while the impact to these systems is 

potentially significant, only 3.8 percent 

of all plants regulated under the Stage 

2 DBPR (2,261 of 60,220) will be 

affected by this requirement. Since 

individual systems may employ more 

than one plant, it is likely that fewer 

than 1,620 systems (3.4 percent of 

48,293 systems) will be affected by this 

requirement. The new IDSE and 

monitoring requirements are expected to 

have a small impact on the technical 

and managerial capacity of small 

systems, a moderate impact on the 

financial capacity of some small 

systems, and a much smaller impact on 

large systems. The capacity of systems 

that must conduct an operational 

evaluation will only be impacted in a 

minor way, while those systems that 

must only familiarize themselves with 

the rule (the large majority of systems) 

will not face any capacity impact as a 

result of the Stage 2 DBPR. 

N. Congressional Review Act 

The Congressional Review Act, 5 

U.S.C. 801 et seq., as added by the Small 

Business Regulatory Enforcement 

Fairness Act of 1996, generally provides 

that before a rule may take effect, the 

agency promulgating the rule must 

submit a rule report, which includes a 

copy of the rule, to each House of the 

Congress and to the Comptroller General 

of the United States. EPA will submit a 

report containing this rule and other 

required information to the U.S. Senate, 

the U.S. House of Representatives, and 

the Comptroller General of the United 

States prior to publication of the rule in 

the Federal Register. A Major rule 

cannot take effect until 60 days after it 

is published in the Federal Register. 

This action is a ‘‘major rule’’ as defined 

by 5 U.S.C. 804(2). This rule will be 

effective March 6, 2006. 

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Absorbance at 254 nm in Source Water 

and Drinking Water. Revision 1.1. EPA/ 

600/R–05/055. (Available at http:// 

www.epa.gov/nerlcwww/ordmeth.htm.) 

USEPA. 2005m. Unregulated Contaminant 

Monitoring Regulation (UCMR) for 

Public Water Systems Revions; Proposed 

Rule. 70 FR 49094, August 22, 2005. 

USEPA. 2005n. Information Collection 

Request for National Primary Drinking 

Water Regulations: Final Stage 2 

Disinfectants and Disinfection 

Byproducts Rule. Washington, DC. EPA 

815–Z–05–002. 

USEPA. 2006. Initial Distribution System 

Evaluation Guidance Manual for the 

Final Stage 2 Disinfectants and 

Disinfection Byproducts Rule. 

Washington, DC. EPA 815–B–06–002. 

USFDA (Food and Drug Administration). 

1994. Sanitizing Solutions. 21 Code of 

Federal Regulation, Part 

178.1010.&http://ecfr.gpoaccess.gov/cgi/ 

t/text/text-idx?c=ecfr&tpl=%2Findex.tpl 

Villanueva, C.M., M. Kogevinas and J.O. 

Grimalt. 2001. Drinking water 

chlorination and adverse health effects: a 

review of epidemiological studies. 

Medicina Clinica 117(1): 27–35. 

(Spanish). 

Villanueva, C.M., Fernandez, F., Malats, N., 

Grimalt, J.O., and Kogenvinas, M. 2003. 

Meta-analysis of Studies on Individual 

Consumption of Chlorinated Drinking 

Water and Bladder Cancer. Journal of 

Epidemiology Community Health 57: 

166–173. 

Villanueva, C.M., K.P. Cantor, S. Cordier, 

J.J.K. Jaakkola, W.D. King, C.F. Lynch, S. 

Porru and M. Kogevinas. 2004. 

Disinfection byproducts and bladder 

cancer a pooled analysis. Epidemiology. 

15(3):357–367. 

Vinceti, M., G. Fantuzzi, L. Monici, et al. 

2004. A retrospective cohort study of 

trihalomethane exposure through 

drinking water and cancer mortality in 

northern Italy. Science of the Total 

Environment. 330(1–3):47–53. 

Vineis, P. 2004. A self-fulfilling prophecy: 

are we underestimating the role of the 

environment in gene-environment 

interaction research? International 

Journal of Epidemiology. 33:945–946. 

Waller, K., S.H. Swan, G. DeLorenze, B. 

Hopkins. 1998. Trihalomethanes in 

drinking water and spontaneous 

abortion. Epidemiology. 9(2):134–140. 

Waller, K., S.H. Swan, G.C. Windham and L. 

Fenster. 2001. Influence of exposure 

assessment methods on risk estimates in 

an epidemiologic study of total 


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trihalomethane exposure and 

spontaneous abortion. Journal of 

Exposure Analysis and Environmental 

Epidemiology. 11(6): 522–531. 

Weinberg, H.S., S.W. Krasner, S.D. 

Richardson and A.D. Thruston, Jr. 2002. 

The Occurrence of Disinfection ByProducts (DBPs) of Health Concern in 

Drinking Water: Results of a Nationwide 

DBP Occurrence Study, U.S. 

Environmental Protection Agency, 

National Exposure Research Laboratory, 

Athens, GA. EPA/600/R–02/068. http:// 

www.epa.gov/athens/publications/ 

EPA600R02068.pdf. 

WHO. 2000. World Health Organization, 

International Programme on Chemical 

Safety (IPCS). Environmental Health 

Criteria 216: Disinfectants and 

Disinfectant By-products. 

Windham, GC, Swan SH, Fenster L, Neutra 

RR. 1992. Tap or bottled water 

consumption and spontaneous abortion: 

a 1986 case-control study in California. 

Epidemiology. 3:113–9. 

Windham GC, Waller K, Anderson M, 

Fenster L, Mendola P, and Swan S. 2003. 

Chlorination by-products in drinking 

water and menstrual cycle function. 

Environ Health Perspect: doi:10.1289/ 

ehp.5922. http://ehpnet1.niehs.nih.gov/ 

docs/2003/5922/abstract.html. 

Wrensch, M., S.H. Swan, J. Lipscomb, D.M. 

Epstein, R.R. Neutra, and L. Fenster. 

1992. Spontaneous abortions and birth 

defects related to tap and bottled water 

use, San Jose, California, 1980–1985. 

Epidemiology. 3(2):98–103. 

Wright, J.M., J. Schwartz and D.W. Dockery. 

2003. Effect of trihalomethane exposure 

on fetal development. Occupational and 

Environmental Medicine. 60(3):173–180. 

Wright, J.M., J. Schwartz and D.W. Dockery. 

2004. The effect of disinfection byproducts and mutagenic activity on birth 

weight and gestational duration. 

Environmental Health Perspectives. 

112(8):920–925. 

Xu, X., T.M. Marino, J.D. Laskin and C.P. 

Weisel. 2002. Pericutaneous absorption 

of trihalomethanes, haloacetic acids, and 

haloketones. Toxicology and Applied 

Pharmacology. 184(1):19–26. 

Yang, C.Y., Chiu, H.F, Cheng, M.F., and Tsai, 

S.S. 1998. Chlorination of Drinking 

Water and Cancer Mortality in Taiwan. 

Environ Res, 78:1–6. 

Yang, V., B. Cheng, S. Tsai, T. Wu, M. Lin 

M. and K. Lin. 2000. Association 

between chlorination of drinking water 

and adverse pregnancy outcome in 

Taiwan. Environ. Health. Perspect. 

108:765–68. 

Yang, C.–Y. 2004. Drinking water 

chlorination and adverse birth outcomes 

in Taiwan. Toxicology. 198(2004):249–

254. 

Zheng, M., S. Andrews, and J. Bolton. 1999. 

Impacts of medium-pressure UV on THM 

and HAA formation in pre-UV 

chlorinated drinking water. Proceedings, 

Water Quality Technology Conference of 

the American Water Works Association, 

Denver, CO. 

List of Subjects 

40 CFR Part 9 

Reporting and recordkeeping 

requirements. 

40 CFR Part 141 

Environmental protection, Chemicals, 

Indians-lands, Incorporation by 

reference, Intergovernmental relations, 

Radiation protection, Reporting and 

recordkeeping requirements, Water 

supply. 

40 CFR Part 142 

Environmental protection, 

Administrative practice and procedure, 

Chemicals, Indians-lands, Radiation 

protection, Reporting and recordkeeping 

requirements, Water supply. 

Dated: December 15, 2005. 

Stephen L. Johnson, 

Administrator. 

■ For the reasons set forth in the 

preamble, title 40 chapter I of the Code 

of Federal Regulations is amended as 

follows: 

PART 9—OMB APPROVALS UNDER 

THE PAPERWORK REDUCTION ACT 

■ 1. The authority citation for part 9 

continues to read as follows: 

Authority: 7 U.S.C. 135 et seq., 136–136y; 

15 U.S.C. 2001, 2003, 2005, 2006, 2601–2671; 

21 U.S.C. 331j, 346a, 348; 31 U.S.C. 9701; 33 

U.S.C. 1251 et seq., 1311, 1313d, 1314, 1318, 

1321, 1326, 1330, 1342, 1344, 1345 (d) and 

(e), 1361; Executive Order 11735, 38 FR 

21243, 3 CFR, 1971–1975 Comp. p. 973; 42 

U.S.C. 241, 242b, 243, 246, 300f, 300g, 300g–

1, 300g–2, 300g–3, 300g–4, 300g–5, 300g–6, 

300j–1, 300j–2, 300j–3, 300j–4, 300j–9, 1857 

et seq., 6901–6992k, 7401–7671q, 7542, 

9601–9657, 11023, 11048. 

■ 2. In § 9.1 the table is amended as 

follows: 

■ a. Under the heading ‘‘National 

Primary Drinking Water Regulations 

Implementation’’ by adding entries in 

numerical order for ‘‘§ 141.600–141.605, 

141.620–141.626, 141.629’’. 

■ b. Under the heading ‘‘National 

Primary Drinking Water Regulations 

Implementation’’ by removing entries 

‘‘§ 142.14(a),142.14(a)–(d)(3)’’ and 

adding entries in numerical order for 

‘‘142.14(a) (1)–(7), 142.14(a)(8), 

142.14(b)–(d) and 142.16(m)’’ as 

follows: 

§ 9.1 OMB approvals under the Paperwork 

Reduction Act. 

* * * * * 

40 CFR citation OMB control 

No. 

40 CFR citation OMB control 

No. 

* * * * * 

National Primary Drinking Water 

Regulations 

* * * * * 

141.600–141.605 .................. 2040–0265 

141.620–141.626 .................. 2040–0265 

141.629 ................................. 2040–0265 

National Primary Drinking Water 

Regulations Implementation 

* * * * * 

142.14(a)(1)–(7) .................... 2040–0265 

142.14(a)(8) .......................... 2040–0265 

142.14(b)–(d) ........................ 2040–0090 

* * * * * 

142.16(m) ............................. 2040–0265 

* * * * * 

PART 141—NATIONAL PRIMARY 

DRINKING WATER REGULATIONS 

■ 3. The authority citation for part 141 

continues to read as follows: 

Authority: 42 U.S.C. 300f, 300g–1, 300g–2, 

300g–3, 300g–4, 300g–5, 300g–6, 300j–4, 

300j–9, and 300j–11. 

■ 4. Section 141.2 is amended by 

adding, in alphabetical order, 

definitions for ‘‘Combined distribution 

system’’, ‘‘Consecutive system’’, ‘‘Dual 

sample sets’’, ‘‘Finished water’’, 

‘‘GAC20’’, ‘‘Locational running annual 

average’’, and ‘‘Wholesale system’’ and 

revising the definition of ‘‘GAC10’’ to 

read as follows: 

§ 141.2 Definitions. 

* * * * * 

Combined distribution system is the 

interconnected distribution system 

consisting of the distribution systems of 

wholesale systems and of the 

consecutive systems that receive 

finished water. 

* * * * * 

Consecutive system is a public water 

system that receives some or all of its 

finished water from one or more 

wholesale systems. Delivery may be 

through a direct connection or through 

the distribution system of one or more 

consecutive systems. 

* * * * * 

Dual sample set is a set of two 

samples collected at the same time and 

same location, with one sample 

analyzed for TTHM and the other 


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478 Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 

sample analyzed for HAA5. Dual sample 

sets are collected for the purposes of 

conducting an IDSE under subpart U of 

this part and determining compliance 

with the TTHM and HAA5 MCLs under 

subpart V of this part. 

* * * * * 

Finished water is water that is 

introduced into the distribution system 

of a public water system and is intended 

for distribution and consumption 

without further treatment, except as 

treatment necessary to maintain water 

quality in the distribution system (e.g., 

booster disinfection, addition of 

corrosion control chemicals). 

* * * * * 

GAC10 means granular activated 

carbon filter beds with an empty-bed 

contact time of 10 minutes based on 

average daily flow and a carbon 

reactivation frequency of every 180 

days, except that the reactivation 

frequency for GAC10 used as a best 

available technology for compliance 

with subpart V MCLs under 

§ 141.64(b)(2) shall be 120 days. 

GAC20 means granular activated 

carbon filter beds with an empty-bed 

contact time of 20 minutes based on 

average daily flow and a carbon 

reactivation frequency of every 240 

days. 

* * * * * 

Locational running annual average 

(LRAA) is the average of sample 

analytical results for samples taken at a 

particular monitoring location during 

the previous four calendar quarters. 

* * * * * 

Wholesale system is a public water 

system that treats source water as 

necessary to produce finished water and 

then delivers some or all of that finished 

water to another public water system. 

Delivery may be through a direct 

connection or through the distribution 

system of one or more consecutive 

systems. 

§ 141.12 [Removed] 

■ 5. Section 141.12 is removed and 

reserved. 

§ 141.30 [Removed] 

■ 6. Section 141.30 is removed. 

§ 141.32 [Removed] 

■ 7. Section 141.32 is removed and 

reserved. 

■ 8. Section 141.33 is amended by 

revising the first sentence of paragraph 

(a) introductory text and adding 

paragraph (f) to read as follows: 

§ 141.33 Record maintenance. 

* * * * * 

(a) Records of microbiological 

analyses and turbidity analyses made 

pursuant to this part shall be kept for 

not less than 5 years. * * * 

* * * * * 

(f) Copies of monitoring plans 

developed pursuant to this part shall be 

kept for the same period of time as the 

records of analyses taken under the plan 

are required to be kept under paragraph 

(a) of this section, except as specified 

elsewhere in this part. 

■ 9. Section 141.53 is amended by 

revising the table to read as follows: 

§ 141.53 Maximum contaminant level goals 

for disinfection byproducts. 

* * * * * 

Disinfection byproduct MCLG (mg/L) 

Bromodichloromethane ......... zero 

Bromoform ............................ zero 

Bromate ................................. zero 

Chlorite .................................. 0.8 

Chloroform ............................ 0.07 

Dibromochloromethane ......... 0.06 

Dichloroacetic acid ................ zero 

Monochloroacetic acid .......... 0.07 

Trichloroacetic acid ............... 0.02 

■ 10. Section 141.64 is revised to read 

as follows: 

§ 141.64 Maximum contaminant levels for 

disinfection byproducts. 

(a) Bromate and chlorite. The 

maximum contaminant levels (MCLs) 

for bromate and chlorite are as follows: 

Disinfection byproduct MCL (mg/L) 

Bromate .................................... 0 .010 

Chlorite ..................................... 1 .0 

(1) Compliance dates for CWSs and 

NTNCWSs. Subpart H systems serving 

10,000 or more persons must comply 

with this paragraph (a) beginning 

January 1, 2002. Subpart H systems 

serving fewer than 10,000 persons and 

systems using only ground water not 

under the direct influence of surface 

water must comply with this paragraph 

(a) beginning January 1, 2004. 

(2) The Administrator, pursuant to 

section 1412 of the Act, hereby 

identifies the following as the best 

technology, treatment techniques, or 

other means available for achieving 

compliance with the maximum 

contaminant levels for bromate and 

chlorite identified in this paragraph (a): 

Disinfection byproduct 

Best available technology 

Bromate Control of ozone treatment process to reduce production of bromate 

Disinfection byproduct 

Best available technology 

Chlorite Control of treatment processes to 

reduce disinfectant demand and 

control of disinfection treatment 

processes to reduce disinfectant 

levels 

(b) TTHM and HAA5. (1) Subpart L—

RAA compliance. (i) Compliance dates. 

Subpart H systems serving 10,000 or 

more persons must comply with this 

paragraph (b)(1) beginning January 1, 

2002. Subpart H systems serving fewer 

than 10,000 persons and systems using 

only ground water not under the direct 

influence of surface water must comply 

with this paragraph (b)(1) beginning 

January 1, 2004. All systems must 

comply with these MCLs until the date 

specified for subpart V compliance in 

§ 141.620(c). 

Disinfection byproduct MCL (mg/L) 

Total trihalomethanes (TTHM) 0.080 

Haloacetic acids (five) (HAA5) 0.060 

(ii) The Administrator, pursuant to 

section 1412 of the Act, hereby 

identifies the following as the best 

technology, treatment techniques, or 

other means available for achieving 

compliance with the maximum 

contaminant levels for TTHM and 

HAA5 identified in this paragraph 

(b)(1): 

Disinfection byproduct Best available technology 

Total trihalomethanes 

(TTHM) and 

Haloacetic acids 

(five) (HAA5).

Enhanced coagulation or enhanced 

softening or 

GAC10, with chlorine as the primary 

and residual disinfectant 

(2) Subpart V—LRAA compliance. (i) 

Compliance dates. The subpart V MCLs 

for TTHM and HAA5 must be complied 

with as a locational running annual 

average at each monitoring location 

beginning the date specified for subpart 

V compliance in § 141.620(c). 

Disinfection byproduct MCL (mg/L) 

Total trihalomethanes (TTHM) 0.080 

Haloacetic acids (five) (HAA5) 0.060 

(ii) The Administrator, pursuant to 

section 1412 of the Act, hereby 

identifies the following as the best 

technology, treatment techniques, or 

other means available for achieving 

compliance with the maximum 

contaminant levels for TTHM and 

HAA5 identified in this paragraph (b)(2) 


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Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 479 

for all systems that disinfect their source 

water: 

Disinfection byproduct Best available technology 

Total 

trihalomethanes (TTHM) 

and 

Haloacetic 

acids (five) 

(HAA5).

Enhanced coagulation or enhanced softening, plus 

GAC10; or nanofiltration 

with a molecular weight 

cutoff ≤1000 Daltons; or 

GAC20 

(iii) The Administrator, pursuant to 

section 1412 of the Act, hereby 

identifies the following as the best 

technology, treatment techniques, or 

other means available for achieving 

compliance with the maximum 

contaminant levels for TTHM and 

HAA5 identified in this paragraph (b)(2) 

for consecutive systems and applies 

only to the disinfected water that 

consecutive systems buy or otherwise 

receive: 

Disinfection byproduct Best available technology 

Total 

trihalomethanes (TTHM) 

and 

Haloacetic 

acids (five) 

(HAA5).

Systems serving ≥10,000: 

Improved distribution system and storage tank 

management to reduce 

residence time, plus the 

use of chloramines for disinfectant residual maintenance 

Systems serving <10,000: 

Improved distribution system and storage tank 

management to reduce 

residence time 

■ 11. Section 141.131 is amended as 

follows: 

■ a. By revising paragraph (a), 

■ b. By revising paragraphs (b)(1) and 

(b)(2), 

■ c. By revising the table in paragraph 

(c)(1), 

■ d. By revising paragraphs (d)(2), 

(d)(3), (d)(4)(i), and (d)(4)(ii), 

■ e. By adding paragraph (d)(6). 

§ 141.131 Analytical requirements. 

(a) General. (1) Systems must use only 

the analytical methods specified in this 

section, or their equivalent as approved 

by EPA, to demonstrate compliance 

with the requirements of this subpart 

and with the requirements of subparts U 

and V of this part. These methods are 

effective for compliance monitoring 

February 16, 1999, unless a different 

effective date is specified in this section 

or by the State. 

(2) The following documents are 

incorporated by reference. The Director 

of the Federal Register approves this 

incorporation by reference in 

accordance with 5 U.S.C. 552(a) and 1 

CFR part 51. Copies may be inspected 

at EPA’s Drinking Water Docket, 1301 

Constitution Avenue, NW., EPA West, 

Room B102, Washington, DC 20460, or 

at the National Archives and Records 

Administration (NARA). For 

information on the availability of this 

material at NARA, call 202–741–6030, 

or go to: http://www.archives.gov/ 

federal_register/ 

code_of_federal_regulations/ 

ibr_locations.html. EPA Method 552.1 is 

in Methods for the Determination of 

Organic Compounds in Drinking WaterSupplement II, USEPA, August 1992, 

EPA/600/R–92/129 (available through 

National Information Technical Service 

(NTIS), PB92–207703). EPA Methods 

502.2, 524.2, 551.1, and 552.2 are in 

Methods for the Determination of 

Organic Compounds in Drinking WaterSupplement III, USEPA, August 1995, 

EPA/600/R–95/131 (available through 

NTIS, PB95–261616). EPA Method 

300.0 is in Methods for the 

Determination of Inorganic Substances 

in Environmental Samples, USEPA, 

August 1993, EPA/600/R–93/100 

(available through NTIS, PB94–121811). 

EPA Methods 300.1 and 321.8 are in 

Methods for the Determination of 

Organic and Inorganic Compounds in 

Drinking Water, Volume 1, USEPA, 

August 2000, EPA 815–R–00–014 

(available through NTIS, PB2000–

106981). EPA Method 317.0, Revision 

2.0, ‘‘Determination of Inorganic 

Oxyhalide Disinfection By-Products in 

Drinking Water Using Ion 

Chromatography with the Addition of a 

Postcolumn Reagent for Trace Bromate 

Analysis,’’ USEPA, July 2001, EPA 815–

B–01–001, EPA Method 326.0, Revision 

1.0, ‘‘Determination of Inorganic 

Oxyhalide Disinfection By-Products in 

Drinking Water Using Ion 

Chromatography Incorporating the 

Addition of a Suppressor Acidified 

Postcolumn Reagent for Trace Bromate 

Analysis,’’ USEPA, June 2002, EPA 815–

R–03–007, EPA Method 327.0, Revision 

1.1, ‘‘Determination of Chlorine Dioxide 

and Chlorite Ion in Drinking Water 

Using Lissamine Green B and 

Horseradish Peroxidase with Detection 

by Visible Spectrophotometry,’’ USEPA, 

May 2005, EPA 815–R–05–008 and EPA 

Method 552.3, Revision 1.0, 

‘‘Determination of Haloacetic Acids and 

Dalapon in Drinking Water by Liquidliquid Microextraction, Derivatization, 

and Gas Chromatography with Electron 

Capture Detection,’’ USEPA, July 2003, 

EPA–815–B–03–002 can be accessed 

and downloaded directly on-line at 

http://www.epa.gov/safewater/methods/ 

sourcalt.html. EPA Method 415.3, 

Revision 1.1, ‘‘Determination of Total 

Organic Carbon and Specific UV 

Absorbance at 254 nm in Source Water 

and Drinking Water,’’ USEPA, February 

2005, EPA/600/R–05/055 can be 

accessed and downloaded directly online at www.epa.gov/nerlcwww/ 

ordmeth.htm. Standard Methods 4500–

Cl D, 4500–Cl E, 4500–Cl F, 4500–Cl G, 

4500–Cl H, 4500–Cl I, 4500–ClO2 D, 

4500–ClO2 E, 6251 B, and 5910 B shall 

be followed in accordance with 

Standard Methods for the Examination 

of Water and Wastewater, 19th or 20th 

Editions, American Public Health 

Association, 1995 and 1998, 

respectively. The cited methods 

published in either edition may be used. 

Standard Methods 5310 B, 5310 C, and 

5310 D shall be followed in accordance 

with the Supplement to the 19th Edition 

of Standard Methods for the 

Examination of Water and Wastewater, 

or the Standard Methods for the 

Examination of Water and Wastewater, 

20th Edition, American Public Health 

Association, 1996 and 1998, 

respectively. The cited methods 

published in either edition may be used. 

Copies may be obtained from the 

American Public Health Association, 

1015 Fifteenth Street, NW., Washington, 

DC 20005. Standard Methods 4500–Cl 

D–00, 4500–Cl E–00, 4500–Cl F–00, 

4500–Cl G–00, 4500–Cl H–00, 4500–Cl 

I–00, 4500–ClO2 E–00, 6251 B–94, 5310 

B–00, 5310 C–00, 5310 D–00 and 5910 

B–00 are available at http:// 

www.standardmethods.org or at EPA’s 

Water Docket. The year in which each 

method was approved by the Standard 

Methods Committee is designated by the 

last two digits in the method number. 

The methods listed are the only Online 

versions that are IBR-approved. ASTM 

Methods D 1253–86 and D 1253–86 

(Reapproved 1996) shall be followed in 

accordance with the Annual Book of 

ASTM Standards, Volume 11.01, 

American Society for Testing and 

Materials International, 1996 or any 

ASTM edition containing the IBRapproved version of the method may be 

used. ASTM Method D1253–03 shall be 

followed in accordance with the Annual 

Book of ASTM Standards, Volume 

11.01, American Society for Testing and 

Materials International, 2004 or any 

ASTM edition containing the IBRapproved version of the method may be 

used. ASTM Method D 6581–00 shall be 

followed in accordance with the Annual 

Book of ASTM Standards, Volume 

11.01, American Society for Testing and 

Materials International, 2001 or any 

ASTM edition containing the IBRapproved version of the method may be 

used; copies may be obtained from the 

American Society for Testing and 


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480 Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 

Materials International, 100 Barr Harbor 

Drive, West Conshohocken, PA 19428–

2959. 

(b) Disinfection byproducts. (1) 

Systems must measure disinfection 

byproducts by the methods (as modified 

by the footnotes) listed in the following 

table: 

APPROVED METHODS FOR DISINFECTION BYPRODUCT COMPLIANCE MONITORING

Contaminant and methodology 1 EPA method Standard method 2 SM online 9 ASTM method 3

TTHM 

P&T/GC/ElCD & PID ................................... 502.2 4 .......................... ...................................... ......................................

P&T/GC/MS ................................................ 524.2 ............................ ...................................... ......................................

LLE/GC/ECD ............................................... 551.1 ............................ ...................................... ......................................

HAA5 

LLE (diazomethane)/GC/ECD ..................... ...................................... 6251 B5 ....................... 6251 B–94 ...................

SPE (acidic methanol)/GC/ECD ................. 552.1 5 .......................... ...................................... ......................................

LLE (acidic methanol)/GC/ECD .................. 552.2, 552.3 ................. ...................................... ......................................

Bromate 

Ion chromatography .................................... 300.1 ............................ ...................................... ...................................... D 6581–00 

Ion chromatography & post column reaction.317.0 Rev 2.0 6, 326.0 6 ...................................... ......................................

IC/ICP–MS .................................................. 321.86 7 ........................ ...................................... ......................................

Chlorite 

Amperometric titration ................................. ...................................... 4500–ClO2 E8 ............. 4500–ClO2 E–00 8 .......

Spectrophotometry ...................................... 327.0 Rev 1.1 8 ............ ...................................... ......................................

Ion chromatography .................................... 300.0, 300.1, 317.0 

Rev 2.0, 326.0.

...................................... ...................................... D 6581–00 

1P&T = purge and trap; GC = gas chromatography; ElCD = electrolytic conductivity detector; PID = photoionization detector; MS = mass spectrometer; LLE = liquid/liquid extraction; ECD = electron capture detector; SPE = solid phase extraction; IC = ion chromatography; ICP–MS = inductively coupled plasma/mass spectrometer. 2 19th and 20th editions of Standard Methods for the Examination of Water and Wastewater, 1995 and 1998, respectively, American Public 

Health Association; either of these editions may be used. 3Annual Book of ASTM Standards, 2001 or any year containing the cited version of the method, Vol 11.01. 

4 If TTHMs are the only analytes being measured in the sample, then a PID is not required. 

5The samples must be extracted within 14 days of sample collection. 

6 Ion chromatography & post column reaction or IC/ICP-MS must be used for monitoring of bromate for purposes of demonstrating eligibility of 

reduced monitoring, as prescribed in § 141.132(b)(3)(ii). 7Samples must be preserved at the time of sampling with 50 mg ethylenediamine (EDA)/L of sample and must be analyzed within 28 days. 8Amperometric titration or spectrophotometry may be used for routine daily monitoring of chlorite at the entrance to the distribution system, as 

prescribed in § 141.132(b)(2)(i)(A). Ion chromatography must be used for routine monthly monitoring of chlorite and additional monitoring of chlorite in the distribution system, as prescribed in § 141.132(b)(2)(i)(B) and (b)(2)(ii). 9The Standard Methods Online version that is approved is indicated by the last two digits in the method number which is the year of approval 

by the Standard Method Committee. Standard Methods Online are available at http://www.standardmethods.org. 

(2) Analyses under this section for 

disinfection byproducts must be 

conducted by laboratories that have 

received certification by EPA or the 

State, except as specified under 

paragraph (b)(3) of this section. To 

receive certification to conduct analyses 

for the DBP contaminants in §§ 141.64, 

141.135, and subparts U and V of this 

part, the laboratory must: 

(i) Analyze Performance Evaluation 

(PE) samples that are acceptable to EPA 

or the State at least once during each 

consecutive 12 month period by each 

method for which the laboratory desires 

certification. 

(ii) Until March 31, 2007, in these 

analyses of PE samples, the laboratory 

must achieve quantitative results within 

the acceptance limit on a minimum of 

80% of the analytes included in each PE 

sample. The acceptance limit is defined 

as the 95% confidence interval 

calculated around the mean of the PE 

study between a maximum and 

minimum acceptance limit of +/¥50% 

and +/¥15% of the study mean. 

(iii) Beginning April 1, 2007, the 

laboratory must achieve quantitative 

results on the PE sample analyses that 

are within the following acceptance 

limits: 

DBP 

Acceptance 

limits (percent 

of true value) 

Comments 

TTHM 

Chloroform ........................................................................... ±20 Laboratory must meet all 4 individual THM acceptance limits 

in order to successfully pass a PE sample for TTHM 

Bromodichloromethane ....................................................... ±20 

Dibromochloromethane ....................................................... ±20 

Bromoform ........................................................................... ±20 

HAA5 

Monochloroacetic Acid ........................................................ ±40 Laboratory must meet the acceptance limits for 4 out of 5 of 

the HAA5 compounds in order to successfully pass a PE 

sample for HAA5 

Dichloroacetic Acid .............................................................. ±40 

Trichloroacetic Acid ............................................................. ±40 

Monobromoacetic Acid ........................................................ ±40 

Dibromoacetic Acid ............................................................. ±40 

Chlorite ....................................................................................... ±30 


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DBP 

Acceptance 

limits (percent 

of true value) 

Comments 

Bromate ...................................................................................... ±30 

(iv) Beginning April 1, 2007, report 

quantitative data for concentrations at 

least as low as the ones listed in the 

following table for all DBP samples 

analyzed for compliance with §§ 141.64, 

141.135, and subparts U and V of this 

part: 

DBP 

Minimum reporting level 

(mg/L) 1

Comments 

TTHM 2

Chloroform ............................................................................. 0.0010 

Bromodichloromethane .......................................................... 0.0010 

Dibromochloromethane ......................................................... 0.0010 

Bromoform ............................................................................. 0.0010 

HAA5 2

Monochloroacetic Acid .......................................................... 0.0020 

Dichloroacetic Acid ................................................................ 0.0010 

Trichloroacetic Acid ............................................................... 0.0010 

Monobromoacetic Acid .......................................................... 0.0010 

Dibromoacetic Acid ................................................................ 0.0010 

Chlorite .......................................................................................... 0.020 Applicable to monitoring as prescribed in § 141.132(b)(2)(1)(B) 

and (b)(2)(ii). 

Bromate ........................................................................................ 0.0050 or 

0.0010 

Laboratories that use EPA Methods 317.0 Revision 2.0, 326.0 

or 321.8 must meet a 0.0010 mg/L MRL for bromate. 

1The calibration curve must encompass the regulatory minimum reporting level (MRL) concentration. Data may be reported for concentrations 

lower than the regulatory MRL as long as the precision and accuracy criteria are met by analyzing an MRL check standard at the lowest reporting limit chosen by the laboratory. The laboratory must verify the accuracy of the calibration curve at the MRL concentration by analyzing an 

MRL check standard with a concentration less than or equal to 110% of the MRL with each batch of samples. The measured concentration for 

the MRL check standard must be ±50% of the expected value, if any field sample in the batch has a concentration less than 5 times the regulatory MRL. Method requirements to analyze higher concentration check standards and meet tighter acceptance criteria for them must be met in 

addition to the MRL check standard requirement. 2When adding the individual trihalomethane or haloacetic acid concentrations to calculate the TTHM or HAA5 concentrations, respectively, a 

zero is used for any analytical result that is less than the MRL concentration for that DBP, unless otherwise specified by the State. 

* * * * * 

(c) * * * 

(1) * * * 

Methodology SM (19th or 

20th ed) 

SM 

Online 2

ASTM 

method 

EPA 

method 

Residual measured 1

Free 

Cl2

Combined 

Cl2

Total 

Cl2 ClO2

Amperometric Titration 4500–C D 4500–C D–

00 

D 1253–86 (96), 

03 

X X X 

Low Level Amperometric Titration.4500–C E 4500–C E–

00 

X 

DPD Ferrous Titrimetric 4500–C F 4500–C F–

00 

X X X 

DPD Colorimetric .......... 4500–C G 4500–C G–

00 

X X X 

Syringaldazine (FACTS) 4500–C H 4500–C H–

00 

X 

Iodometric Electrode .... 4500–C I 4500–C I–00 X 

DPD .............................. 4500–C O2 D X 

Amperometric Method II 4500–C O2 E 4500–C O2

E–00 

X 

Lissamine Green 

Spectrophotometric.

327.0 Rev 

1.1 

X 

1X indicates method is approved for measuring specified disinfectant residual. Free chlorine or total chlorine may be measured for demonstrating compliance with the chlorine MRDL and combined chlorine, or total chlorine may be measured for demonstrating compliance with the 

chloramine MRDL. 2The Standard Methods Online version that is approved is indicated by the last two digits in the method number which is the year of approval 

by the Standard Method Committee. Standard Methods Online are available at http://www.standardmethods.org. 

* * * * * 

(d) * * * 

(2) Bromide. EPA Methods 300.0, 

300.1, 317.0 Revision 2.0, 326.0, or 

ASTM D 6581–00. 

(3) Total Organic Carbon (TOC). 

Standard Method 5310 B or 5310 B–00 

(High-Temperature Combustion 


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Method) or Standard Method 5310 C or 

5310 C–00 (Persulfate-Ultraviolet or 

Heated-Persulfate Oxidation Method) or 

Standard Method 5310 D or 5310 D–00 

(Wet-Oxidation Method) or EPA Method 

415.3 Revision 1.1. Inorganic carbon 

must be removed from the samples prior 

to analysis. TOC samples may not be 

filtered prior to analysis. TOC samples 

must be acidified at the time of sample 

collection to achieve pH less than or 

equal to 2 with minimal addition of the 

acid specified in the method or by the 

instrument manufacturer. Acidified 

TOC samples must be analyzed within 

28 days. 

(4) * * * 

(i) Dissolved Organic Carbon (DOC). 

Standard Method 5310 B or 5310 B–00 

(High-Temperature Combustion 

Method) or Standard Method 5310 C or 

5310 C–00 (Persulfate-Ultraviolet or 

Heated-Persulfate Oxidation Method) or 

Standard Method 5310 D or 5310 D–00 

(Wet-Oxidation Method) or EPA Method 

415.3 Revision 1.1. DOC samples must 

be filtered through the 0.45 μm porediameter filter as soon as practical after 

sampling, not to exceed 48 hours. After 

filtration, DOC samples must be 

acidified to achieve pH less than or 

equal to 2 with minimal addition of the 

acid specified in the method or by the 

instrument manufacturer. Acidified 

DOC samples must be analyzed within 

28 days of sample collection. Inorganic 

carbon must be removed from the 

samples prior to analysis. Water passed 

through the filter prior to filtration of 

the sample must serve as the filtered 

blank. This filtered blank must be 

analyzed using procedures identical to 

those used for analysis of the samples 

and must meet the following criteria: 

DOC < 0.5 mg/L. 

(ii) Ultraviolet Absorption at 254 nm 

(UV254). Standard Method 5910 B or 

5910 B–00 (Ultraviolet Absorption 

Method) or EPA Method 415.3 Revision 

1.1. UV absorption must be measured at 

253.7 nm (may be rounded off to 254 

nm). Prior to analysis, UV254 samples 

must be filtered through a 0.45 μm porediameter filter. The pH of UV254 samples 

may not be adjusted. Samples must be 

analyzed as soon as practical after 

sampling, not to exceed 48 hours. 

* * * * * 

(6) Magnesium. All methods allowed 

in § 141.23(k)(1) for measuring 

magnesium. 

■ 12. Section 141.132 is amended by: 

■ a. Redesignating paragraphs (b)(1)(iii) 

through (b)(1)(v) as paragraphs (b)(1)(iv) 

through (b)(1)(vi); 

■ b. Adding a new paragraph (b)(1)(iii); 

■ c. Revising newly redesignated 

paragraph (b)(1)(iv); and 

■ d. Revising paragraph (b)(3)(ii). 

The addition and revisions read as 

follows: 

§ 141.132 Monitoring requirements. 

* * * * * 

(b) * * * 

(1) * * * 

(iii) Monitoring requirements for 

source water TOC. In order to qualify for 

reduced monitoring for TTHM and 

HAA5 under paragraph (b)(1)(ii) of this 

section, subpart H systems not 

monitoring under the provisions of 

paragraph (d) of this section must take 

monthly TOC samples every 30 days at 

a location prior to any treatment, 

beginning April 1, 2008 or earlier, if 

specified by the State. In addition to 

meeting other criteria for reduced 

monitoring in paragraph (b)(1)(ii) of this 

section, the source water TOC running 

annual average must be ≤4.0 mg/L 

(based on the most recent four quarters 

of monitoring) on a continuing basis at 

each treatment plant to reduce or 

remain on reduced monitoring for 

TTHM and HAA5. Once qualified for 

reduced monitoring for TTHM and 

HAA5 under paragraph (b)(1)(ii) of this 

section, a system may reduce source 

water TOC monitoring to quarterly TOC 

samples taken every 90 days at a 

location prior to any treatment. 

(iv) Systems on a reduced monitoring 

schedule may remain on that reduced 

schedule as long as the average of all 

samples taken in the year (for systems 

which must monitor quarterly) or the 

result of the sample (for systems which 

must monitor no more frequently than 

annually) is no more than 0.060 mg/L 

and 0.045 mg/L for TTHMs and HAA5, 

respectively. Systems that do not meet 

these levels must resume monitoring at 

the frequency identified in paragraph 

(b)(1)(i) of this section (minimum 

monitoring frequency column) in the 

quarter immediately following the 

monitoring period in which the system 

exceeds 0.060 mg/L or 0.045 mg/L for 

TTHMs and HAA5, respectively. For 

systems using only ground water not 

under the direct influence of surface 

water and serving fewer than 10,000 

persons, if either the TTHM annual 

average is >0.080 mg/L or the HAA5 

annual average is >0.060 mg/L, the 

system must go to the increased 

monitoring identified in paragraph 

(b)(1)(i) of this section (sample location 

column) in the quarter immediately 

following the monitoring period in 

which the system exceeds 0.080 mg/L or 

0.060 mg/L for TTHMs or HAA5 

respectively. 

* * * * * 

(3) *** 

(i) *** 

(ii) Reduced monitoring. 

(A) Until March 31, 2009, systems 

required to analyze for bromate may 

reduce monitoring from monthly to 

quarterly, if the system’s average source 

water bromide concentration is less than 

0.05 mg/L based on representative 

monthly bromide measurements for one 

year. The system may remain on 

reduced bromate monitoring until the 

running annual average source water 

bromide concentration, computed 

quarterly, is equal to or greater than 0.05 

mg/L based on representative monthly 

measurements. If the running annual 

average source water bromide 

concentration is ≥0.05 mg/L, the system 

must resume routine monitoring 

required by paragraph (b)(3)(i) of this 

section in the following month. 

(B) Beginning April 1, 2009, systems 

may no longer use the provisions of 

paragraph (b)(3)(ii)(A) of this section to 

qualify for reduced monitoring. A 

system required to analyze for bromate 

may reduce monitoring from monthly to 

quarterly, if the system’s running annual 

average bromate concentration is 

≤0.0025 mg/L based on monthly 

bromate measurements under paragraph 

(b)(3)(i) of this section for the most 

recent four quarters, with samples 

analyzed using Method 317.0 Revision 

2.0, 326.0 or 321.8. If a system has 

qualified for reduced bromate 

monitoring under paragraph (b)(3)(ii)(A) 

of this section, that system may remain 

on reduced monitoring as long as the 

running annual average of quarterly 

bromate samples ≤0.0025 mg/L based on 

samples analyzed using Method 317.0 

Revision 2.0, 326.0, or 321.8. If the 

running annual average bromate 

concentration is >0.0025 mg/L, the 

system must resume routine monitoring 

required by paragraph (b)(3)(i) of this 

section. 

* * * * * 

§ 141.133 [Amended] 

■ 13. Section 141.133 is amended in the 

last sentence of paragraph (d) by 

revising the reference ‘‘§ 141.32’’ to read 

‘‘subpart Q of this part’’. 

■ 14. Section 141.135 is amended by 

revising paragraph (a)(3)(ii) to read as 

follows: 

§ 141.135 Treatment technique for control 

of disinfection byproduct (DBP) precursors. 

(a) * * * 

(3) * * * 

(ii) Softening that results in removing 

at least 10 mg/L of magnesium hardness 

(as CaCO3), measured monthly 

according to § 141.131(d)(6) and 

calculated quarterly as a running annual 

average. 

* * * * * 


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■ 15. Section 141.151 is amended by 

revising paragraph (d) to read as 

follows: 

§ 141.151 Purpose and applicability of this 

subpart. 

* * * * * 

(d) For the purpose of this subpart, 

detected means: at or above the levels 

prescribed by § 141.23(a)(4) for 

inorganic contaminants, at or above the 

levels prescribed by § 141.24(f)(7) for 

the contaminants listed in § 141.61(a), at 

or above the levels prescribed by 

§ 141.24(h)(18) for the contaminants 

listed in § 141.61(c), at or above the 

levels prescribed by § 141.131(b)(2)(iv) 

for the contaminants or contaminant 

groups listed in § 141.64, and at or 

above the levels prescribed by 

§ 141.25(c) for radioactive contaminants. 

* * * * * 

■ 16. Section 141.153 is amended by 

revising paragraphs (d)(4)(iv)(B) and 

(d)(4)(iv)(C) to read as follows: 

§ 141.153 Content of the reports. 

* * * * * 

(d) * * * 

(4) * * * 

(iv) * * * 

(B) When compliance with the MCL is 

determined by calculating a running 

annual average of all samples taken at 

a monitoring location: the highest 

average of any of the monitoring 

locations and the range of all monitoring 

locations expressed in the same units as 

the MCL. For the MCLs for TTHM and 

HAA5 in § 141.64(b)(2), systems must 

include the highest locational running 

annual average for TTHM and HAA5 

and the range of individual sample 

results for all monitoring locations 

expressed in the same units as the MCL. 

If more than one location exceeds the 

TTHM or HAA5 MCL, the system must 

include the locational running annual 

averages for all locations that exceed the 

MCL. 

(C) When compliance with the MCL is 

determined on a system-wide basis by 

calculating a running annual average of 

all samples at all monitoring locations: 

the average and range of detection 

expressed in the same units as the MCL. 

The system is required to include 

individual sample results for the IDSE 

conducted under subpart U of this part 

when determining the range of TTHM 

and HAA5 results to be reported in the 

annual consumer confidence report for 

the calendar year that the IDSE samples 

were taken. 

* * * * * 

Appendix A to Subpart Q [Amended] 

■ 17. In Subpart Q, Appendix A is 

amended as follows: 

■ a. In entry I.B.2. in the fifth column, 

remove the endnote citation ‘‘9’’ and 

add in its place ‘‘11’’; 

■ b. In entry I.B.11. in the fourth 

column, remove the endnote citation 

‘‘10’’ and add in its place ‘‘12’’; 

■ c. In entry I.B.12. in the fourth 

column, remove the endnote citation 

‘‘10’’ and add in its place ‘‘12’’; 

■ d. In entry I.G. in the first column, 

remove the endnote citation ‘‘11’’ and 

add in its place ‘‘13’’; 

■ e. In entry I.G.1. in the third column, 

remove the endnote citation ‘‘12’’ and 

add in its place ‘‘14’’ and remove the 

citation in the third column ‘‘141.12, 

141.64(a)’’ and in its place add 

‘‘141.64(b)’’ (keeping the endnote 

citation to endnote 14) and in the fifth 

column remove the citation ‘‘141.30’’

and add in numerical order the citations 

‘‘141.600–141.605, 141.620–141.629’’; 

■ f. In entry I.G.2. revise the entry 

‘‘141.64(a)’’ to read ‘‘141.64(b)’’ and in 

the fifth column add in numerical order 

the citations ‘‘141.600–141.605, 

141.620–141.629’’. 

■ g. In entry I.G.7. in the fourth column, 

remove the endnote citation ‘‘13’’ and 

add in its place ‘‘15’’; 

■ h. In entry I.G.8. in the second 

column, remove the endnote citation 

‘‘14’’ and add in its place ‘‘16’’; 

■ i. In entry II. in the first column, 

remove the endnote citation ‘‘15’’ and 

add in its place ‘‘17’’; 

■ j. In entry III.A. in the third column, 

remove the endnote citation ‘‘16’’ and 

add in its place ‘‘18’’; 

■ k. In entry III.B in the third column, 

remove the endnote citation ‘‘17’’ and 

add in its place ‘‘19’’; 

■ l. In entry IV.E. in the first column, 

remove the endnote citation ‘‘18’’ and 

add in its place 20’’; and 

■ m. In entry III.F in the second column, 

remove the endnote citation ‘‘19’’ and 

add in its place ‘‘21’’. 

■ 18. In Subpart Q, Appendix A, remove 

endnote 14 and add in its place, to read 

as follows: ‘‘14.§§ 141.64(b)(1) 

141.132(a)–(b) apply until §§ 141.620–

141.630 take effect under the schedule 

in § 141.620(c). 

■ 19–20. In Subpart Q, Appendix B is 

amended as follows: 

■ a. In entry G.77. in the third column, 

remove the endnote citation ‘‘16’’ and 

add in its place ‘‘17’’; 

■ b. In entry H. (the title) in the first 

column, remove the endnote citation 

‘‘17’’ and add in its place ‘‘18’’; 

■ c. In entry H.80. in the third column, 

remove the endnote citations ‘‘17, 18’’

and add in its place ‘‘19, 20’’ and 

remove the number ‘‘0.10/’’; 

■ d. In entry H.81. in the third column, 

remove the endnote citation ‘‘20’’ and 

add in its place ‘‘21’’; and 

■ e. In entry H.84. in the second 

column, remove the endnote citation 

‘‘21’’ and add in its place ‘‘22’’ and in 

the third column remove the endnote 

citation ‘‘22’’ and add in its place ‘‘23’’. 

■ f. Revise endnotes 18 and 19. 

The revisions read as follows: 

Appendix B to Subpart Q 

* * * * * 

■ 18. Surface water systems and ground 

water systems under the direct 

influence of surface water are regulated 

under subpart H of 40 CFR 141. Subpart 

H community and non-transient noncommunity systems serving ≥10,000 

must comply with subpart L DBP MCLs 

and disinfectant maximum residual 

disinfectant levels (MRDLs) beginning 

January 1, 2002. All other community 

and non-transient non-community 

systems must comply with subpart L 

DBP MCLs and disinfectant MRDLs 

beginning January 1, 2004. Subpart H 

transient non-community systems 

serving ≥10,000 that use chlorine 

dioxide as a disinfectant or oxidant 

must comply with the chlorine dioxide 

MRDL beginning January 1, 2002. All 

other transient non-community systems 

that use chlorine dioxide as a 

disinfectant or oxidant must comply 

with the chlorine dioxide MRDL 

beginning January 1, 2004. 

■ 19. Community and non-transient 

non-community systems must comply 

with subpart V TTHM and HAA5 MCLs 

of 0.080 mg/L and 0.060 mg/L, 

respectively (with compliance 

calculated as a locational running 

annual average) on the schedule in 

§ 141.620. 

* * * * * 

■ 21. Part 141 is amended by adding 

new subpart U to read as follows: 

Subpart U—Initial Distribution System 

Evaluations 

141.600 General requirements. 

141.601 Standard monitoring. 

141.602 System specific studies. 

141.603 40/30 certification. 

141.604 Very small system waivers. 

141.605 Subpart V compliance monitoring 

location recommendations. 

Subpart U—Initial Distribution System 

Evaluations 

§ 141.600 General requirements. 

(a) The requirements of subpart U of 

this part constitute national primary 

drinking water regulations. The 

regulations in this subpart establish 

monitoring and other requirements for 

identifying subpart V compliance 

monitoring locations for determining 

compliance with maximum 

contaminant levels for total 


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trihalomethanes (TTHM) and haloacetic 

acids (five)(HAA5). You must use an 

Initial Distribution System Evaluation 

(IDSE) to determine locations with 

representative high TTHM and HAA5 

concentrations throughout your 

distribution system. IDSEs are used in 

conjunction with, but separate from, 

subpart L compliance monitoring, to 

identify and select subpart V 

compliance monitoring locations. 

(b) Applicability. You are subject to 

these requirements if your system is a 

community water system that uses a 

primary or residual disinfectant other 

than ultraviolet light or delivers water 

that has been treated with a primary or 

residual disinfectant other than 

ultraviolet light; or if your system is a 

nontransient noncommunity water 

system that serves at least 10,000 people 

and uses a primary or residual 

disinfectant other than ultraviolet light 

or delivers water that has been treated 

with a primary or residual disinfectant 

other than ultraviolet light. 

(c) Schedule. (1) You must comply 

with the requirements of this subpart on 

the schedule in the table in this 

paragraph (c)(1). 

If you serve this 

population 

You must submit your standard monitoring plan or system specific study 

plan 1 or 40/30 certification 2 to the 

State by or receive very small system 

waiver from State 

You must complete your standard 

monitoring or system specific study by 

You must submit your IDSE report to 

the State by 3

Systems that are not part of a combined distribution system and systems that serve the largest population in the combined 

distribution system 

(i) ≥100,000 ............ October 1, 2006 .................................... September 30, 2008 ............................. January 1, 2009. 

(ii) 50,000–99,999 .. April 1, 2007 ......................................... March 31, 2009 .................................... July 1, 2009. 

(iii) 10,000–49,999 October 1, 2007 .................................... September 30, 2009 ............................. January 1, 2010. 

(iv) <10,000 (CWS 

Only).

April 1, 2008 ......................................... March 31, 2010 .................................... July 1, 2010. 

Other systems that are part of a combined distribution system 

(v) Wholesale system or consecutive system.—at the same time as the system with 

the earliest compliance date in the 

combined distribution system.

—at the same time as the system with 

the earliest compliance date in the 

combined distribution system.

—at the same time as the system with 

the earliest compliance date in the 

combined distribution system. 

1 If, within 12 months after the date identified in this column, the State does not approve your plan or notify you that it has not yet completed its 

review, you may consider the plan that you submitted as approved. You must implement that plan and you must complete standard monitoring or 

a system specific study no later than the date identified in the third column. 2You must submit your 40/30 certification under § 141.603 by the date indicated. 3 If, within three months after the date identified in this column (nine months after the date identified in this column if you must comply on the 

schedule in paragraph (c)(1)(iii) of this section), the State does not approve your IDSE report or notify you that it has not yet completed its review, you may consider the report that you submitted as approved and you must implement the recommended subpart V monitoring as required. 

(2) For the purpose of the schedule in 

paragraph (c)(1) of this section, the State 

may determine that the combined 

distribution system does not include 

certain consecutive systems based on 

factors such as receiving water from a 

wholesale system only on an emergency 

basis or receiving only a small 

percentage and small volume of water 

from a wholesale system. The State may 

also determine that the combined 

distribution system does not include 

certain wholesale systems based on 

factors such as delivering water to a 

consecutive system only on an 

emergency basis or delivering only a 

small percentage and small volume of 

water to a consecutive system. 

(d) You must conduct standard 

monitoring that meets the requirements 

in § 141.601, or a system specific study 

that meets the requirements in 

§ 141.602, or certify to the State that you 

meet 40/30 certification criteria under 

§ 141.603, or qualify for a very small 

system waiver under § 141.604. 

(1) You must have taken the full 

complement of routine TTHM and 

HAA5 compliance samples required of 

a system with your population and 

source water under subpart L of this 

part (or you must have taken the full 

complement of reduced TTHM and 

HAA5 compliance samples required of 

a system with your population and 

source water under subpart L if you 

meet reduced monitoring criteria under 

subpart L of this part) during the period 

specified in § 141.603(a) to meet the 40/ 

30 certification criteria in § 141.603. 

You must have taken TTHM and HAA5 

samples under §§ 141.131 and 141.132 

to be eligible for the very small system 

waiver in § 141.604. 

(2) If you have not taken the required 

samples, you must conduct standard 

monitoring that meets the requirements 

in § 141.601, or a system specific study 

that meets the requirements in 

§ 141.602. 

(e) You must use only the analytical 

methods specified in § 141.131, or 

otherwise approved by EPA for 

monitoring under this subpart, to 

demonstrate compliance with the 

requirements of this subpart. 

(f) IDSE results will not be used for 

the purpose of determining compliance 

with MCLs in § 141.64. 

§ 141.601 Standard monitoring. 

(a) Standard monitoring plan. Your 

standard monitoring plan must comply 

with paragraphs (a)(1) through (a)(4) of 

this section. You must prepare and 

submit your standard monitoring plan 

to the State according to the schedule in 

§ 141.600(c). 

(1) Your standard monitoring plan 

must include a schematic of your 

distribution system (including 

distribution system entry points and 

their sources, and storage facilities), 

with notes indicating locations and 

dates of all projected standard 

monitoring, and all projected subpart L 

compliance monitoring. 

(2) Your standard monitoring plan 

must include justification of standard 

monitoring location selection and a 

summary of data you relied on to justify 

standard monitoring location selection. 

(3) Your standard monitoring plan 

must specify the population served and 

system type (subpart H or ground 

water). 

(4) You must retain a complete copy 

of your standard monitoring plan 

submitted under this paragraph (a), 

including any State modification of your 

standard monitoring plan, for as long as 


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Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 485 

you are required to retain your IDSE 

report under paragraph (c)(4) of this 

section. 

(b) Standard monitoring. (1) You must 

monitor as indicated in the table in this 

paragraph (b)(1). You must collect dual 

sample sets at each monitoring location. 

One sample in the dual sample set must 

be analyzed for TTHM. The other 

sample in the dual sample set must be 

analyzed for HAA5. You must conduct 

one monitoring period during the peak 

historical month for TTHM levels or 

HAA5 levels or the month of warmest 

water temperature. You must review 

available compliance, study, or 

operational data to determine the peak 

historical month for TTHM or HAA5 

levels or warmest water temperature. 

Source water 

type 

Population size 

category 

Monitoring periods and frequency of 

sampling 

Distribution system monitoring locations 1

Total per 

monitoring 

period 

Near 

entry 

points 

Average 

residence 

time 

High 

TTHM 

locations 

High 

HAA5 

locations 

Subpart H 

<500 consecutive systems ...... one (during peak historical 

month) 2.

2 1 ................ 1 

<500 non-consecutive systems .................................................. 2 ................ ................ 1 1 

500–3,300 consecutive systems.four (every 90 days) ................ 2 1 ................ 1 

500–3,300 non-consecutive 

systems.

.................................................. 2 ................ ................ 1 1 

3,301–9,999 ............................. .................................................. 4 ................ 1 2 1 

10,000–49,999 ......................... six (every 60 days) .................. 8 1 2 3 2 

50,000–249,999 ....................... .................................................. 16 3 4 5 4 

250,000–999,999 ..................... .................................................. 24 4 6 8 6 

1,000,000–4,999,999 ............... .................................................. 32 6 8 10 8 

≥5,000,000 ............................... .................................................. 40 8 10 12 10 

Ground Water 

<500 consecutive systems ...... one (during peak historical 

month) 2.

2 1 ................ 1 

<500 non-consecutive systems .................................................. 2 ................ ................ 1 1 

500–9,999 ................................ four (every 90 days) ................ 2 ................ ................ 1 1 

10,000–99,999 ......................... .................................................. 6 1 1 2 2 

100,000–499,999 ..................... .................................................. 8 1 1 3 3 

≥500,000 .................................. .................................................. 12 2 2 4 4 

1A dual sample set (i.e., a TTHM and an HAA5 sample) must be taken at each monitoring location during each monitoring period. 

2The peak historical month is the month with the highest TTHM or HAA5 levels or the warmest water temperature. 

(2) You must take samples at locations 

other than the existing subpart L 

monitoring locations. Monitoring 

locations must be distributed 

throughout the distribution system. 

(3) If the number of entry points to the 

distribution system is fewer than the 

specified number of entry point 

monitoring locations, excess entry point 

samples must be replaced equally at 

high TTHM and HAA5 locations. If 

there is an odd extra location number, 

you must take a sample at a high TTHM 

location. If the number of entry points 

to the distribution system is more than 

the specified number of entry point 

monitoring locations, you must take 

samples at entry points to the 

distribution system having the highest 

annual water flows. 

(4) Your monitoring under this 

paragraph (b) may not be reduced under 

the provisions of § 141.29 and the State 

may not reduce your monitoring using 

the provisions of § 142.16(m). 

(c) IDSE report. Your IDSE report 

must include the elements required in 

paragraphs (c)(1) through (c)(4) of this 

section. You must submit your IDSE 

report to the State according to the 

schedule in § 141.600(c). 

(1) Your IDSE report must include all 

TTHM and HAA5 analytical results 

from subpart L compliance monitoring 

and all standard monitoring conducted 

during the period of the IDSE as 

individual analytical results and LRAAs 

presented in a tabular or spreadsheet 

format acceptable to the State. If 

changed from your standard monitoring 

plan submitted under paragraph (a) of 

this section, your report must also 

include a schematic of your distribution 

system, the population served, and 

system type (subpart H or ground 

water). 

(2) Your IDSE report must include an 

explanation of any deviations from your 

approved standard monitoring plan. 

(3) You must recommend and justify 

subpart V compliance monitoring 

locations and timing based on the 

protocol in § 141.605. 

(4) You must retain a complete copy 

of your IDSE report submitted under 

this section for 10 years after the date 

that you submitted your report. If the 

State modifies the subpart V monitoring 

requirements that you recommended in 

your IDSE report or if the State approves 

alternative monitoring locations, you 

must keep a copy of the State’s 

notification on file for 10 years after the 

date of the State’s notification. You 

must make the IDSE report and any 

State notification available for review by 

the State or the public. 

§ 141.602 System specific studies. 

(a) System specific study plan. Your 

system specific study plan must be 

based on either existing monitoring 

results as required under paragraph 

(a)(1) of this section or modeling as 

required under paragraph (a)(2) of this 

section. You must prepare and submit 

your system specific study plan to the 

State according to the schedule in 

§ 141.600(c). 

(1) Existing monitoring results. You 

may comply by submitting monitoring 

results collected before you are required 

to begin monitoring under § 141.600(c). 

The monitoring results and analysis 

must meet the criteria in paragraphs 

(a)(1)(i) and (a)(1)(ii) of this section. 

(i) Minimum requirements. (A) TTHM 

and HAA5 results must be based on 

samples collected and analyzed in 

accordance with § 141.131. Samples 

must be collected no earlier than five 

years prior to the study plan submission 

date. 


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(B) The monitoring locations and 

frequency must meet the conditions 

identified in this paragraph (a)(1)(i)(B). 

Each location must be sampled once 

during the peak historical month for 

TTHM levels or HAA5 levels or the 

month of warmest water temperature for 

every 12 months of data submitted for 

that location. Monitoring results must 

include all subpart L compliance 

monitoring results plus additional 

monitoring results as necessary to meet 

minimum sample requirements. 

System Type 

Population 

size 

category 

Number of 

monitoring 

locations 

Number of samples 

TTHM HAA5 

Subpart H: 

<500 3 3 3 

500–3,300 3 9 9 

3,301–9,999 6 36 36 

10,000–49,999 12 72 72 

50,000–

249,999 

24 144 144 

250,000–

999,999 

36 216 216 

1,000,000–

4,999,999 

48 288 288 

≥ 5,000,000 60 360 360 

Ground Water: 

<500 3 3 3 

500–9,999 3 9 9 

10,000–99,999 12 48 48 

100,000–

499,999 

18 72 72 

≥ 500,000 24 96 96 

(ii) Reporting monitoring results. You 

must report the information in this 

paragraph (a)(1)(ii). 

(A) You must report previously 

collected monitoring results and certify 

that the reported monitoring results 

include all compliance and noncompliance results generated during the 

time period beginning with the first 

reported result and ending with the 

most recent subpart L results. 

(B) You must certify that the samples 

were representative of the entire 

distribution system and that treatment, 

and distribution system have not 

changed significantly since the samples 

were collected. 

(C) Your study monitoring plan must 

include a schematic of your distribution 

system (including distribution system 

entry points and their sources, and 

storage facilities), with notes indicating 

the locations and dates of all completed 

or planned system specific study 

monitoring. 

(D) Your system specific study plan 

must specify the population served and 

system type (subpart H or ground 

water). 

(E) You must retain a complete copy 

of your system specific study plan 

submitted under this paragraph (a)(1), 

including any State modification of your 

system specific study plan, for as long 

as you are required to retain your IDSE 

report under paragraph (b)(5) of this 

section. 

(F) If you submit previously collected 

data that fully meet the number of 

samples required under paragraph 

(a)(1)(i)(B) of this section and the State 

rejects some of the data, you must either 

conduct additional monitoring to 

replace rejected data on a schedule the 

State approves or conduct standard 

monitoring under § 141.601. 

(2) Modeling. You may comply 

through analysis of an extended period 

simulation hydraulic model. The 

extended period simulation hydraulic 

model and analysis must meet the 

criteria in this paragraph (a)(2). 

(i) Minimum requirements. (A) The 

model must simulate 24 hour variation 

in demand and show a consistently 

repeating 24 hour pattern of residence 

time. 

(B) The model must represent the 

criteria listed in paragraphs 

(a)(2)(i)(B)(1) through (9) of this section. 

(1) 75% of pipe volume; 

(2) 50% of pipe length; 

(3) All pressure zones; 

(4) All 12-inch diameter and larger 

pipes; 

(5) All 8-inch and larger pipes that 

connect pressure zones, influence zones 

from different sources, storage facilities, 

major demand areas, pumps, and 

control valves, or are known or expected 

to be significant conveyors of water; 

(6) All 6-inch and larger pipes that 

connect remote areas of a distribution 

system to the main portion of the 

system; 

(7) All storage facilities with standard 

operations represented in the model; 

and 

(8) All active pump stations with 

controls represented in the model; and 

(9) All active control valves. 

(C) The model must be calibrated, or 

have calibration plans, for the current 

configuration of the distribution system 

during the period of high TTHM 

formation potential. All storage facilities 

must be evaluated as part of the 

calibration process. All required 

calibration must be completed no later 

than 12 months after plan submission. 

(ii) Reporting modeling. Your system 

specific study plan must include the 

information in this paragraph (a)(2)(ii). 

(A) Tabular or spreadsheet data 

demonstrating that the model meets 

requirements in paragraph (a)(2)(i)(B) of 

this section. 

(B) A description of all calibration 

activities undertaken, and if calibration 

is complete, a graph of predicted tank 

levels versus measured tank levels for 

the storage facility with the highest 

residence time in each pressure zone, 

and a time series graph of the residence 

time at the longest residence time 

storage facility in the distribution 

system showing the predictions for the 

entire simulation period (i.e., from time 

zero until the time it takes to for the 

model to reach a consistently repeating 

pattern of residence time). 

(C) Model output showing 

preliminary 24 hour average residence 

time predictions throughout the 

distribution system. 

(D) Timing and number of samples 

representative of the distribution system 

planned for at least one monitoring 

period of TTHM and HAA5 dual sample 

monitoring at a number of locations no 


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less than would be required for the 

system under standard monitoring in 

§ 141.601 during the historical month of 

high TTHM. These samples must be 

taken at locations other than existing 

subpart L compliance monitoring 

locations. 

(E) Description of how all 

requirements will be completed no later 

than 12 months after you submit your 

system specific study plan. 

(F) Schematic of your distribution 

system (including distribution system 

entry points and their sources, and 

storage facilities), with notes indicating 

the locations and dates of all completed 

system specific study monitoring (if 

calibration is complete) and all subpart 

L compliance monitoring. 

(G) Population served and system 

type (subpart H or ground water). 

(H) You must retain a complete copy 

of your system specific study plan 

submitted under this paragraph (a)(2), 

including any State modification of your 

system specific study plan, for as long 

as you are required to retain your IDSE 

report under paragraph (b)(7) of this 

section. 

(iii) If you submit a model that does 

not fully meet the requirements under 

paragraph (a)(2) of this section, you 

must correct the deficiencies and 

respond to State inquiries concerning 

the model. If you fail to correct 

deficiencies or respond to inquiries to 

the State’s satisfaction, you must 

conduct standard monitoring under 

§ 141.601. 

(b) IDSE report. Your IDSE report 

must include the elements required in 

paragraphs (b)(1) through (b)(6) of this 

section. You must submit your IDSE 

report according to the schedule in 

§ 141.600(c). 

(1) Your IDSE report must include all 

TTHM and HAA5 analytical results 

from subpart L compliance monitoring 

and all system specific study monitoring 

conducted during the period of the 

system specific study presented in a 

tabular or spreadsheet format acceptable 

to the State. If changed from your 

system specific study plan submitted 

under paragraph (a) of this section, your 

IDSE report must also include a 

schematic of your distribution system, 

the population served, and system type 

(subpart H or ground water). 

(2) If you used the modeling provision 

under paragraph (a)(2) of this section, 

you must include final information for 

the elements described in paragraph 

(a)(2)(ii) of this section, and a 24-hour 

time series graph of residence time for 

each subpart V compliance monitoring 

location selected. 

(3) You must recommend and justify 

subpart V compliance monitoring 

locations and timing based on the 

protocol in § 141.605. 

(4) Your IDSE report must include an 

explanation of any deviations from your 

approved system specific study plan. 

(5) Your IDSE report must include the 

basis (analytical and modeling results) 

and justification you used to select the 

recommended subpart V monitoring 

locations. 

(6) You may submit your IDSE report 

in lieu of your system specific study 

plan on the schedule identified in 

§ 141.600(c) for submission of the 

system specific study plan if you believe 

that you have the necessary information 

by the time that the system specific 

study plan is due. If you elect this 

approach, your IDSE report must also 

include all information required under 

paragraph (a) of this section. 

(7) You must retain a complete copy 

of your IDSE report submitted under 

this section for 10 years after the date 

that you submitted your IDSE report. If 

the State modifies the subpart V 

monitoring requirements that you 

recommended in your IDSE report or if 

the State approves alternative 

monitoring locations, you must keep a 

copy of the State’s notification on file 

for 10 years after the date of the State’s 

notification. You must make the IDSE 

report and any State notification 

available for review by the State or the 

public. 

§ 141.603 40/30 certification. 

(a) Eligibility. You are eligible for 40/ 

30 certification if you had no TTHM or 

HAA5 monitoring violations under 

subpart L of this part and no individual 

sample exceeded 0.040 mg/L for TTHM 

or 0.030 mg/L for HAA5 during an eight 

consecutive calendar quarter period 

beginning no earlier than the date 

specified in this paragraph (a). 

If your 40/30 

certification is 

due 

Then your eligibility for 40/30 

certification is based on 

eight consecutive calendar 

quarters of subpart L compliance monitoring results beginning no earlier than 1

(1) October 1, 

2006.

January 2004. 

(2) April 1, 

2007.

January 2004. 

(3) October 1, 

2007.

January 2005. 

(4) April 1, 

2008.

January 2005. 

1 Unless you are on reduced monitoring 

under subpart L of this part and were not required to monitor during the specified period. If 

you did not monitor during the specified period, you must base your eligibility on compliance samples taken during the 12 months preceding the specified period. 

(b) 40/30 certification. (1) You must 

certify to your State that every 

individual compliance sample taken 

under subpart L of this part during the 

periods specified in paragraph (a) of this 

section were ≤0.040 mg/L for TTHM and 

≤0.030 mg/L for HAA5, and that you 

have not had any TTHM or HAA5 

monitoring violations during the period 

specified in paragraph (a) of this 

section. 

(2) The State may require you to 

submit compliance monitoring results, 

distribution system schematics, and/or 

recommended subpart V compliance 

monitoring locations in addition to your 

certification. If you fail to submit the 

requested information, the State may 

require standard monitoring under 

§ 141.601 or a system specific study 

under § 141.602. 

(3) The State may still require 

standard monitoring under § 141.601 or 

a system specific study under § 141.602 

even if you meet the criteria in 

paragraph (a) of this section. 

(4) You must retain a complete copy 

of your certification submitted under 

this section for 10 years after the date 

that you submitted your certification. 

You must make the certification, all data 

upon which the certification is based, 

and any State notification available for 

review by the State or the public. 

§ 141.604 Very small system waivers. 

(a) If you serve fewer than 500 people 

and you have taken TTHM and HAA5 

samples under subpart L of this part, 

you are not required to comply with this 

subpart unless the State notifies you 

that you must conduct standard 

monitoring under § 141.601 or a system 

specific study under § 141.602. 

(b) If you have not taken TTHM and 

HAA5 samples under subpart L of this 

part or if the State notifies you that you 

must comply with this subpart, you 

must conduct standard monitoring 

under § 141.601 or a system specific 

study under § 141.602. 

§ 141.605 Subpart V compliance 

monitoring location recommendations. 

(a) Your IDSE report must include 

your recommendations and justification 

for where and during what month(s) 

TTHM and HAA5 monitoring for 

subpart V of this part should be 

conducted. You must base your 

recommendations on the criteria in 

paragraphs (b) through (e) of this 

section. 

(b) You must select the number of 

monitoring locations specified in the 

table in this paragraph (b). You will use 

these recommended locations as subpart 

V routine compliance monitoring 

locations, unless State requires different 


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or additional locations. You should 

distribute locations throughout the 

distribution system to the extent 

possible. 

Source water type Population 

size category 

Monitoring 

frequency 1

Distribution system monitoring location 

Total per 

monitoring 

period 2

Highest 

TTHM locations 

Highest 

HAA5 locations 

Existing 

subpart L 

compliance 

locations 

Subpart H: 

<500 per year 2 1 1 ....................

500–3,300 per quarter 2 1 1 

3,301–9,999 per quarter 2 1 1 ....................

10,000–

49,999 

per quarter 4 2 1 1 

50,000–

249,999 

per quarter 8 3 3 2 

250,000–

999,999 

per quarter 12 5 4 3 

1,000,000–

4,999,999 

per quarter 16 6 6 4 

≥5,000,000 per quarter 20 8 7 5 

Ground water: 

<500 per year 2 1 1 

500–9,999 per year 2 1 1 

10,000–

99,999 

per quarter 4 2 1 1 

100,000–

499,999 

per quarter 6 3 2 1 

≥500,000 per quarter 8 3 3 2 

1All systems must monitor during month of highest DBP concentrations. 

2Systems on quarterly monitoring must take dual sample sets every 90 days at each monitoring location, except for subpart H systems serving 

500–3,300. Systems on annual monitoring and subpart H systems serving 500–3,300 are required to take individual TTHM and HAA5 samples 

(instead of a dual sample set) at the locations with the highest TTHM and HAA5 concentrations, respectively. Only one location with a dual sample set per monitoring period is needed if highest TTHM and HAA5 concentrations occur at the same location, and month, if monitored annually). 

(c) You must recommend subpart V 

compliance monitoring locations based 

on standard monitoring results, system 

specific study results, and subpart L 

compliance monitoring results. You 

must follow the protocol in paragraphs 

(c)(1) through (c)(8) of this section. If 

required to monitor at more than eight 

locations, you must repeat the protocol 

as necessary. If you do not have existing 

subpart L compliance monitoring results 

or if you do not have enough existing 

subpart L compliance monitoring 

results, you must repeat the protocol, 

skipping the provisions of paragraphs 

(c)(3) and (c)(7) of this section as 

necessary, until you have identified the 

required total number of monitoring 

locations. 

(1) Location with the highest TTHM 

LRAA not previously selected as a 

subpart V monitoring location. 

(2) Location with the highest HAA5 

LRAA not previously selected as a 

subpart V monitoring location. 

(3) Existing subpart L average 

residence time compliance monitoring 

location (maximum residence time 

compliance monitoring location for 

ground water systems) with the highest 

HAA5 LRAA not previously selected as 

a subpart V monitoring location. 

(4) Location with the highest TTHM 

LRAA not previously selected as a 

subpart V monitoring location. 

(5) Location with the highest TTHM 

LRAA not previously selected as a 

subpart V monitoring location. 

(6) Location with the highest HAA5 

LRAA not previously selected as a 

subpart V monitoring location. 

(7) Existing subpart L average 

residence time compliance monitoring 

location (maximum residence time 

compliance monitoring location for 

ground water systems) with the highest 

TTHM LRAA not previously selected as 

a subpart V monitoring location. 

(8) Location with the highest HAA5 

LRAA not previously selected as a 

subpart V monitoring location. 

(d) You may recommend locations 

other than those specified in paragraph 

(c) of this section if you include a 

rationale for selecting other locations. If 

the State approves the alternate 

locations, you must monitor at these 

locations to determine compliance 

under subpart V of this part. 

(e) Your recommended schedule must 

include subpart V monitoring during the 

peak historical month for TTHM and 

HAA5 concentration, unless the State 

approves another month. Once you have 

identified the peak historical month, 

and if you are required to conduct 

routine monitoring at least quarterly, 

you must schedule subpart V 

compliance monitoring at a regular 

frequency of every 90 days or fewer. 

■ 20. Part 141 is amended by adding 

new subpart V to read as follows: 

Subpart V—Stage 2 Disinfection 

Byproducts Requirements 

141.620 General requirements. 

141.621 Routine monitoring. 

141.622 Subpart V monitoring plan. 

141.623 Reduced monitoring. 

141.624 Additional requirements for 

consecutive systems. 

141.625 Conditions requiring increased 

monitoring. 

141.626 Operational evaluation levels. 

141.627 Requirements for remaining on 

reduced TTHM and HAA5 monitoring 

based on subpart L results. 

141.628 Requirements for remaining on 

increased TTHM and HAA5 monitoring 

based on subpart L results. 

141.629 Reporting and recordkeeping 

requirements. 

Subpart V—Stage 2 Disinfection 

Byproducts Requirements 

§ 141.620 General requirements. 

(a) General. The requirements of 

subpart V of this part constitute national 

primary drinking water regulations. The 

regulations in this subpart establish 

monitoring and other requirements for 


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achieving compliance with maximum 

contaminant levels based on locational 

running annual averages (LRAA) for 

total trihalomethanes (TTHM) and 

haloacetic acids (five)(HAA5), and for 

achieving compliance with maximum 

residual disinfectant residuals for 

chlorine and chloramine for certain 

consecutive systems. 

(b) Applicability. You are subject to 

these requirements if your system is a 

community water system or a 

nontransient noncommunity water 

system that uses a primary or residual 

disinfectant other than ultraviolet light 

or delivers water that has been treated 

with a primary or residual disinfectant 

other than ultraviolet light. 

(c) Schedule. You must comply with 

the requirements in this subpart on the 

schedule in the following table based on 

your system type. 

If you are this type of system You must comply with subpart V monitoring by: 1

Systems that are not part of a combined distribution system and systems that serve the largest population in the combined 

distribution system 

(1) System serving ≥ 100,000 ............................................ April 1, 2012. 

(2) System serving 50,000–99,999 .................................... October 1, 2012. 

(3) System serving 10,000–49,999 .................................... October 1, 2013. 

(4) System serving > 10,000 ............................................. October 1, 2013 if no Cryptosporidium monitoring is required under § 141.701(a)(4) 

or 

October 1, 2014 if Cryptosporidium monitoring is required under § 141.701(a)(4) or 

(a)(6) 

Other systems that are part of a combined distribution system 

(5) Consecutive system or wholesale system ................... —at the same time as the system with the earliest compliance date in the combined 

distribution system. 

1The State may grant up to an additional 24 months for compliance with MCLs and operational evaluaton levels if you require capital improvements to comply with an MCL. 

(6) Your monitoring frequency is 

specified in § 141.621(a)(2). 

(i) If you are required to conduct 

quarterly monitoring, you must begin 

monitoring in the first full calendar 

quarter that includes the compliance 

date in the table in this paragraph (c). 

(ii) If you are required to conduct 

monitoring at a frequency that is less 

than quarterly, you must begin 

monitoring in the calendar month 

recommended in the IDSE report 

prepared under § 141.601 or § 141.602 

or the calendar month identified in the 

subpart V monitoring plan developed 

under § 141.622 no later than 12 months 

after the compliance date in this table. 

(7) If you are required to conduct 

quarterly monitoring, you must make 

compliance calculations at the end of 

the fourth calendar quarter that follows 

the compliance date and at the end of 

each subsequent quarter (or earlier if the 

LRAA calculated based on fewer than 

four quarters of data would cause the 

MCL to be exceeded regardless of the 

monitoring results of subsequent 

quarters). If you are required to conduct 

monitoring at a frequency that is less 

than quarterly, you must make 

compliance calculations beginning with 

the first compliance sample taken after 

the compliance date. 

(8) For the purpose of the schedule in 

this paragraph (c), the State may 

determine that the combined 

distribution system does not include 

certain consecutive systems based on 

factors such as receiving water from a 

wholesale system only on an emergency 

basis or receiving only a small 

percentage and small volume of water 

from a wholesale system. The State may 

also determine that the combined 

distribution system does not include 

certain wholesale systems based on 

factors such as delivering water to a 

consecutive system only on an 

emergency basis or delivering only a 

small percentage and small volume of 

water to a consecutive system. 

(d) Monitoring and compliance. (1) 

Systems required to monitor quarterly. 

To comply with subpart V MCLs in 

§ 141.64(b)(2), you must calculate 

LRAAs for TTHM and HAA5 using 

monitoring results collected under this 

subpart and determine that each LRAA 

does not exceed the MCL. If you fail to 

complete four consecutive quarters of 

monitoring, you must calculate 

compliance with the MCL based on the 

average of the available data from the 

most recent four quarters. If you take 

more than one sample per quarter at a 

monitoring location, you must average 

all samples taken in the quarter at that 

location to determine a quarterly 

average to be used in the LRAA 

calculation. 

(2) Systems required to monitor yearly 

or less frequently. To determine 

compliance with subpart V MCLs in 

§ 141.64(b)(2), you must determine that 

each sample taken is less than the MCL. 

If any sample exceeds the MCL, you 

must comply with the requirements of 

§ 141.625. If no sample exceeds the 

MCL, the sample result for each 

monitoring location is considered the 

LRAA for that monitoring location. 

(e) Violation. You are in violation of 

the monitoring requirements for each 

quarter that a monitoring result would 

be used in calculating an LRAA if you 

fail to monitor. 

§ 141.621 Routine monitoring. 

(a) Monitoring. (1) If you submitted an 

IDSE report, you must begin monitoring 

at the locations and months you have 

recommended in your IDSE report 

submitted under § 141.605 following the 

schedule in § 141.620(c), unless the 

State requires other locations or 

additional locations after its review. If 

you submitted a 40/30 certification 

under § 141.603 or you qualified for a 

very small system waiver under 

§ 141.604 or you are a nontransient 

noncommunity water system serving 

<10,000, you must monitor at the 

location(s) and dates identified in your 

monitoring plan in § 141.132(f), updated 

as required by § 141.622. 

(2) You must monitor at no fewer than 

the number of locations identified in 

this paragraph (a)(2). 


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Source water type Population size category Monitoring Frequency 1

Distribution 

system monitoring location 

total per monitoring period 2

Subpart H: 

<500 ...................................................................... per year ......................... 2 

500–3,300 ............................................................. per quarter .................... 2 

3,301–9,999 .......................................................... per quarter .................... 2 

10,000–49,999 ...................................................... per quarter .................... 4 

50,000–249,999 .................................................... per quarter .................... 8 

250,000–999,999 .................................................. per quarter .................... 12 

1,000,000–4,999,999 ............................................ per quarter .................... 16 

≥ 5,000,000 .......................................................... per quarter .................... 20 

Ground Water: 

<500 ...................................................................... per year ......................... 2 

500–9,999 ............................................................. per year ......................... 2 

10,000–99,999 ...................................................... per quarter .................... 4 

100,000–499,999 .................................................. per quarter .................... 6 

≥ 500,000 ............................................................. per quarter .................... 8 

1All systems must monitor during month of highest DBP concentrations. 

2Systems on quarterly monitoring must take dual sample sets every 90 days at each monitoring location, except for subpart H systems serving 

500–3,300. Systems on annual monitoring and subpart H systems serving 500–3,300 are required to take individual TTHM and HAA5 samples 

(instead of a dual sample set) at the locations with the highest TTHM and HAA5 concentrations, respectively. Only one location with a dual sample set per monitoring period is needed if highest TTHM and HAA5 concentrations occur at the same location (and month, if monitored annually). 

(3) If you are an undisinfected system 

that begins using a disinfectant other 

than UV light after the dates in subpart 

U of this part for complying with the 

Initial Distribution System Evaluation 

requirements, you must consult with the 

State to identify compliance monitoring 

locations for this subpart. You must 

then develop a monitoring plan under 

§ 141.622 that includes those 

monitoring locations. 

(b) Analytical methods. You must use 

an approved method listed in § 141.131 

for TTHM and HAA5 analyses in this 

subpart. Analyses must be conducted by 

laboratories that have received 

certification by EPA or the State as 

specified in § 141.131. 

§ 141.622 Subpart V monitoring plan. 

(a)(1) You must develop and 

implement a monitoring plan to be kept 

on file for State and public review. The 

monitoring plan must contain the 

elements in paragraphs (a)(1)(i) through 

(a)(1)(iv) of this section and be complete 

no later than the date you conduct your 

initial monitoring under this subpart. 

(i) Monitoring locations; 

(ii) Monitoring dates; 

(iii) Compliance calculation 

procedures; and 

(iv) Monitoring plans for any other 

systems in the combined distribution 

system if the State has reduced 

monitoring requirements under the 

State authority in § 142.16(m). 

(2) If you were not required to submit 

an IDSE report under either § 141.601 or 

§ 141.602, and you do not have 

sufficient subpart L monitoring 

locations to identify the required 

number of subpart V compliance 

monitoring locations indicated in 

§ 141.605(b), you must identify 

additional locations by alternating 

selection of locations representing high 

TTHM levels and high HAA5 levels 

until the required number of 

compliance monitoring locations have 

been identified. You must also provide 

the rationale for identifying the 

locations as having high levels of TTHM 

or HAA5. If you have more subpart L 

monitoring locations than required for 

subpart V compliance monitoring in 

§ 141.605(b), you must identify which 

locations you will use for subpart V 

compliance monitoring by alternating 

selection of locations representing high 

TTHM levels and high HAA5 levels 

until the required number of subpart V 

compliance monitoring locations have 

been identified. 

(b) If you are a subpart H system 

serving > 3,300 people, you must submit 

a copy of your monitoring plan to the 

State prior to the date you conduct your 

initial monitoring under this subpart, 

unless your IDSE report submitted 

under subpart U of this part contains all 

the information required by this section. 

(c) You may revise your monitoring 

plan to reflect changes in treatment, 

distribution system operations and 

layout (including new service areas), or 

other factors that may affect TTHM or 

HAA5 formation, or for State-approved 

reasons, after consultation with the 

State regarding the need for changes and 

the appropriateness of changes. If you 

change monitoring locations, you must 

replace existing compliance monitoring 

locations with the lowest LRAA with 

new locations that reflect the current 

distribution system locations with 

expected high TTHM or HAA5 levels. 

The State may also require 

modifications in your monitoring plan. 

If you are a subpart H system serving > 

3,300 people, you must submit a copy 

of your modified monitoring plan to the 

State prior to the date you are required 

to comply with the revised monitoring 

plan. 

§ 141.623 Reduced monitoring. 

(a) You may reduce monitoring to the 

level specified in the table in this 

paragraph (a) any time the LRAA is 

≤0.040 mg/L for TTHM and ≤0.030 

mg/L for HAA5 at all monitoring 

locations. You may only use data 

collected under the provisions of this 

subpart or subpart L of this part to 

qualify for reduced monitoring. In 

addition, the source water annual 

average TOC level, before any treatment, 

must be ≤4.0 mg/L at each treatment 

plant treating surface water or ground 

water under the direct influence of 

surface water, based on monitoring 

conducted under either 

§ 141.132(b)(1)(iii) or § 141.132(d). 


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Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 491 

Source water type Population 

size category 

Monitoring 

frequency 1

Distribution system monitoring location per monitoring period 

Subpart H: 

<500 ........................................................ monitoring may not be reduced. 

500–3,300 per year .......................................... 1 TTHM and 1 HAA5 sample: one at the location 

and during the quarter with the highest TTHM single measurement, one at the location and during 

the quarter with the highest HAA5 single measurement; 1 dual sample set per year if the highest 

TTHM and HAA5 measurements occurred at the 

same location and quarter. 

3,301–9,999 per year .......................................... 2 dual sample sets: one at the location and during 

the quarter with the highest TTHM single measurement, one at the location and during the quarter with the highest HAA5 single measurement. 

10,000–49,999 per quarter ..................................... 2 dual sample sets at the locations with the highest 

TTHM and highest HAA5 LRAAs. 

50,000–

249,999 

per quarter ..................................... 4 dual sample sets—at the locations with the two 

highest TTHM and two highest HAA5 LRAAs. 

250,000–

999,999 

per quarter ..................................... 6 dual sample sets—at the locations with the three 

highest TTHM and three highest HAA5 LRAAs. 

1,000,000–

4,999,999 

per quarter ..................................... 8 dual sample sets—at the locations with the four 

highest TTHM and four highest HAA5 LRAAs. 

≥ 5,000,000 per quarter ..................................... 10 dual sample sets—at the locations with the five 

highest TTHM and five highest HAA5 LRAAs. 

Ground Water: 

<500 every third year .............................. 1 TTHM and 1 HAA5 sample: one at the location 

and during the quarter with the highest TTHM single measurement, one at the location and during 

the quarter with the highest HAA5 single measurement; 1 dual sample set per year if the highest 

TTHM and HAA5 measurements occurred at the 

same location and quarter. 

500–9,999 per year .......................................... 1 TTHM and 1 HAA5 sample: one at the location 

and during the quarter with the highest TTHM single measurement, one at the location and during 

the quarter with the highest HAA5 single measurement; 1 dual sample set per year if the highest 

TTHM and HAA5 measurements occurred at the 

same location and quarter. 

10,000–99,999 per year .......................................... 2 dual sample sets: one at the location and during 

the quarter with the highest TTHM single measurement, one at the location and during the quarter with the highest HAA5 single measurement. 

100,000–

499,999 

per quarter ..................................... 2 dual sample sets; at the locations with the highest 

TTHM and highest HAA5 LRAAs. 

≥ 500,000 per quarter ..................................... 4 dual sample sets at the locations with the two 

highest TTHM and two highest HAA5 LRAAs. 

1Systems on quarterly monitoring must take dual sample sets every 90 days. 

(b) You may remain on reduced 

monitoring as long as the TTHM LRAA 

≤0.040 mg/L and the HAA5 LRAA 

≤0.030 mg/L at each monitoring location 

(for systems with quarterly reduced 

monitoring) or each TTHM sample 

≤0.060 mg/L and each HAA5 sample 

≤0.045 mg/L (for systems with annual or 

less frequent monitoring). In addition, 

the source water annual average TOC 

level, before any treatment, must be ≤4.0 

mg/L at each treatment plant treating 

surface water or ground water under the 

direct influence of surface water, based 

on monitoring conducted under either 

§ 141.132(b)(1)(iii) or § 141.132(d). 

(c) If the LRAA based on quarterly 

monitoring at any monitoring location 

exceeds either 0.040 mg/L for TTHM or 

0.030 mg/L for HAA5 or if the annual 

(or less frequent) sample at any location 

exceeds either 0.060 mg/L for TTHM or 

0.045 mg/L for HAA5, or if the source 

water annual average TOC level, before 

any treatment, >4.0 mg/L at any 

treatment plant treating surface water or 

ground water under the direct influence 

of surface water, you must resume 

routine monitoring under § 141.621 or 

begin increased monitoring if § 141.625 

applies. 

(d) The State may return your system 

to routine monitoring at the State’s 

discretion. 

§ 141.624 Additional requirements for 

consecutive systems. 

If you are a consecutive system that 

does not add a disinfectant but delivers 

water that has been treated with a 

primary or residual disinfectant other 

than ultraviolet light, you must comply 

with analytical and monitoring 

requirements for chlorine and 

chloramines in § 141.131 (c) and 

§ 141.132(c)(1) and the compliance 

requirements in § 141.133(c)(1) 

beginning April 1, 2009, unless required 

earlier by the State, and report 

monitoring results under § 141.134(c). 

§ 141.625 Conditions requiring increased 

monitoring. 

(a) If you are required to monitor at 

a particular location annually or less 

frequently than annually under 

§ 141.621 or § 141.623, you must 

increase monitoring to dual sample sets 

once per quarter (taken every 90 days) 

at all locations if a TTHM sample is 

>0.080 mg/L or a HAA5 sample is 

>0.060 mg/L at any location. 


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492 Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 

(b) You are in violation of the MCL 

when the LRAA exceeds the subpart V 

MCLs in § 141.64(b)(2), calculated based 

on four consecutive quarters of 

monitoring (or the LRAA calculated 

based on fewer than four quarters of 

data if the MCL would be exceeded 

regardless of the monitoring results of 

subsequent quarters). You are in 

violation of the monitoring 

requirements for each quarter that a 

monitoring result would be used in 

calculating an LRAA if you fail to 

monitor. 

(c) You may return to routine 

monitoring once you have conducted 

increased monitoring for at least four 

consecutive quarters and the LRAA for 

every monitoring location is ≤0.060 

mg/L for TTHM and ≤0.045 mg/L for 

HAA5. 

§ 141.626 Operational evaluation levels. 

(a) You have exceeded the operational 

evaluation level at any monitoring 

location where the sum of the two 

previous quarters’ TTHM results plus 

twice the current quarter’s TTHM result, 

divided by 4 to determine an average, 

exceeds 0.080 mg/L, or where the sum 

of the two previous quarters’ HAA5 

results plus twice the current quarter’s 

HAA5 result, divided by 4 to determine 

an average, exceeds 0.060 mg/L. 

(b)(1) If you exceed the operational 

evaluation level, you must conduct an 

operational evaluation and submit a 

written report of the evaluation to the 

State no later than 90 days after being 

notified of the analytical result that 

causes you to exceed the operational 

evaluation level. The written report 

must be made available to the public 

upon request. 

(2) Your operational evaluation must 

include an examination of system 

treatment and distribution operational 

practices, including storage tank 

operations, excess storage capacity, 

distribution system flushing, changes in 

sources or source water quality, and 

treatment changes or problems that may 

contribute to TTHM and HAA5 

formation and what steps could be 

considered to minimize future 

exceedences. 

(i) You may request and the State may 

allow you to limit the scope of your 

evaluation if you are able to identify the 

cause of the operational evaluation level 

exceedance. 

(ii) Your request to limit the scope of 

the evaluation does not extend the 

schedule in paragraph (b)(1) of this 

section for submitting the written 

report. The State must approve this 

limited scope of evaluation in writing 

and you must keep that approval with 

the completed report. 

§ 141.627 Requirements for remaining on 

reduced TTHM and HAA5 monitoring based 

on subpart L results. 

You may remain on reduced 

monitoring after the dates identified in 

§ 141.620(c) for compliance with this 

subpart only if you qualify for a 40/30 

certification under § 141.603 or have 

received a very small system waiver 

under § 141.604, plus you meet the 

reduced monitoring criteria in 

§ 141.623(a), and you do not change or 

add monitoring locations from those 

used for compliance monitoring under 

subpart L of this part. If your monitoring 

locations under this subpart differ from 

your monitoring locations under subpart 

L of this part, you may not remain on 

reduced monitoring after the dates 

identified in § 141.620(c) for compliance 

with this subpart. 

§ 141.628 Requirements for remaining on 

increased TTHM and HAA5 monitoring 

based on subpart L results. 

If you were on increased monitoring 

under § 141.132(b)(1), you must remain 

on increased monitoring until you 

qualify for a return to routine 

monitoring under § 141.625(c). You 

must conduct increased monitoring 

under § 141.625 at the monitoring 

locations in the monitoring plan 

developed under § 141.622 beginning at 

the date identified in § 141.620(c) for 

compliance with this subpart and 

remain on increased monitoring until 

you qualify for a return to routine 

monitoring under § 141.625(c). 

§ 141.629 Reporting and recordkeeping 

requirements. 

(a) Reporting. (1) You must report the 

following information for each 

monitoring location to the State within 

10 days of the end of any quarter in 

which monitoring is required: 

(i) Number of samples taken during 

the last quarter. 

(ii) Date and results of each sample 

taken during the last quarter. 

(iii) Arithmetic average of quarterly 

results for the last four quarters for each 

monitoring location (LRAA), beginning 

at the end of the fourth calendar quarter 

that follows the compliance date and at 

the end of each subsequent quarter. If 

the LRAA calculated based on fewer 

than four quarters of data would cause 

the MCL to be exceeded regardless of 

the monitoring results of subsequent 

quarters, you must report this 

information to the State as part of the 

first report due following the 

compliance date or anytime thereafter 

that this determination is made. If you 

are required to conduct monitoring at a 

frequency that is less than quarterly, 

you must make compliance calculations 

beginning with the first compliance 

sample taken after the compliance date, 

unless you are required to conduct 

increased monitoring under § 141.625. 

(iv) Whether, based on § 141.64(b)(2) 

and this subpart, the MCL was violated 

at any monitoring location. 

(v) Any operational evaluation levels 

that were exceeded during the quarter 

and, if so, the location and date, and the 

calculated TTHM and HAA5 levels. 

(2) If you are a subpart H system 

seeking to qualify for or remain on 

reduced TTHM/HAA5 monitoring, you 

must report the following source water 

TOC information for each treatment 

plant that treats surface water or ground 

water under the direct influence of 

surface water to the State within 10 days 

of the end of any quarter in which 

monitoring is required: 

(i) The number of source water TOC 

samples taken each month during last 

quarter. 

(ii) The date and result of each sample 

taken during last quarter. 

(iii) The quarterly average of monthly 

samples taken during last quarter or the 

result of the quarterly sample. 

(iv) The running annual average 

(RAA) of quarterly averages from the 

past four quarters. 

(v) Whether the RAA exceeded 4.0 

mg/L. 

(3) The State may choose to perform 

calculations and determine whether the 

MCL was exceeded or the system is 

eligible for reduced monitoring in lieu 

of having the system report that 

information 

(b) Recordkeeping. You must retain 

any subpart V monitoring plans and 

your subpart V monitoring results as 

required by § 141.33. 

PART 142—NATIONAL PRIMARY 

DRINKING WATER REGULATIONS 

IMPLEMENTATION 

■ 21. The authority citation for part 142 

continues to read as follows: 

Authority: 42 U.S.C. 300f, 300g–1, 300g–2, 

300g–3, 300g–4, 300g–5, 300g–6, 300j–4, 

300j–9, and 300j–11. 

■ 22. Section 142.14 is amended by 

adding paragraph (a)(8) to read as 

follows: 

§ 142.14 Records kept by States. 

(a) * * * 

(8) Any decisions made pursuant to 

the provisions of 40 CFR part 141, 

subparts U and V of this part. 

(i) IDSE monitoring plans, plus any 

modifications required by the State, 

must be kept until replaced by approved 

IDSE reports. 

(ii) IDSE reports and 40/30 

certifications, plus any modifications 


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Federal Register / Vol. 71, No. 2 / Wednesday, January 4, 2006 / Rules and Regulations 493 

required by the State, must be kept until 

replaced or revised in their entirety. 

(iii) Operational evaluations 

submitted by a system must be kept for 

10 years following submission. 

* * * * * 

■ 23. Section 142.16 is amended by 

adding paragraph (m) to read as follows: 

§ 142.16 Special primacy requirements. 

* * * * * 

(m) Requirements for States to adopt 

40 CFR part 141, subparts U and V. In 

addition to the general primacy 

requirements elsewhere in this part, 

including the requirements that State 

regulations be at least as stringent as 

federal requirements, an application for 

approval of a State program revision 

that adopts 40 CFR part 141, subparts U 

and V, must contain a description of 

how the State will implement a 

procedure for addressing modification 

of wholesale system and consecutive 

system monitoring on a case-by-case 

basis for part 141 subpart V outside the 

provisions of § 141.29 of this chapter, if 

the State elects to use such an authority. 

The procedure must ensure that all 

systems have at least one compliance 

monitoring location. 

* * * * * 

[FR Doc. 06–3 Filed 1–3–06; 8:45 am] 

BILLING CODE 6560–50–P 


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