654 Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules and Regulations 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Parts 9, 141, and 142 

[EPA–HQ–OW–2002–0039; FRL–8013–1] 

RIN 2040—AD37 

National Primary Drinking Water 

Regulations: Long Term 2 Enhanced 

Surface Water Treatment Rule 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule. 

SUMMARY: EPA is promulgating National 

Primary Drinking Water Regulations 

that require the use of treatment 

techniques, along with monitoring, 

reporting, and public notification 

requirements, for all public water 

systems that use surface water sources. 

The purposes of the Long Term 2 

Enhanced Surface Water Treatment Rule 

(LT2ESWTR) are to protect public 

health from illness due to 

Cryptosporidium and other microbial 

pathogens in drinking water and to 

address risk-risk trade-offs with the 

control of disinfection byproducts. 

Key provisions in the LT2ESWTR 

include the following: source water 

monitoring for Cryptosporidium, with a 

screening procedure to reduce 

monitoring costs for small systems; risktargeted Cryptosporidium treatment by 

filtered systems with the highest source 

water Cryptosporidium levels; 

inactivation of Cryptosporidium by all 

unfiltered systems; criteria for the use of 

Cryptosporidium treatment and control 

processes; and covering or treating 

uncovered finished water storage 

facilities. 

EPA believes that implementation of 

the LT2ESWTR will significantly reduce 

levels of infectious Cryptosporidium in 

finished drinking water. This will 

substantially lower rates of endemic 

cryptosporidiosis, the illness caused by 

Cryptosporidium, which can be severe 

and sometimes fatal in sensitive 

subpopulations (e.g., infants, people 

with weakened immune systems). In 

addition, the treatment technique 

requirements of this regulation will 

increase protection against other 

microbial pathogens like Giardia 

lamblia. 

DATES: This final rule is effective on 

March 6, 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. For judicial review purposes, this 

final rule is promulgated as of January 

5, 2006. 

ADDRESSES: EPA has established a 

docket for this action under Docket ID 

No. EPA-HQ-OW–2002–0039. All 

documents in the docket are listed on 

the www.regulations.gov Web site. 

Although listed in the index, some 

information is not publicly available, 

i.e., 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 

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 8:30 a.m. to 

4:30 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: 

Daniel C. Schmelling, 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) 564–5281; fax number: 

(202) 564–3767; e-mail address: 

schmelling.dan@epa.gov. For general 

information, contact the Safe Drinking 

Water Hotline, telephone number: (800) 

426–4791. The Safe Drinking Water 

Hotline is open Monday through Friday, 

excluding legal holidays, from 9 a.m. to 

5 p.m., Eastern time. 

SUPPLEMENTARY INFORMATION: 

I. General Information 

A. Who Is Regulated by This Action? 

Entities potentially regulated by the 

LT2ESWTR are public water systems 

(PWSs) that use surface water or ground 

water under the direct influence of 

surface water (GWUDI). Regulated 

categories and entities are identified in 

the following chart. 

Category Examples of regulated entities 

Industry ..................................................................................................... Public Water Systems that use surface water or ground water under 

the direct influence of surface water. 

State, Local, Tribal or Federal Governments ........................................... Public Water Systems that use surface water or ground water under 

the direct influence of surface water. 

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 this 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 § 141.3 of 

Title 40 of the Code of Federal 

Regulations and applicability criteria in 

§ 141.700(b) of today’s rule. If you have 

questions regarding the applicability of 

the LT2ESWTR to a particular entity, 

consult one of the persons listed in the 

preceding section entitled FOR FURTHER

INFORMATION CONTACT. 

Abbreviations Used in This Document 

ASTM American Society for Testing 

and Materials 

AWWA American Water Works 

Association 

°C Degrees Centigrade 

CDC Centers for Disease Control and 

Prevention 

CFE Combined Filter Effluent 

CFR Code of Federal Regulations 

COI Cost-of-Illness 

CT The Residual Concentration of 

Disinfectant (mg/L) Multiplied by the 

Contact Time (in minutes) 

CWS Community Water Systems 

DAPI 4′,6-Diamindino-2-phenylindole 

DBPs Disinfection Byproducts 

DBPR Disinfectants/Disinfection 

Byproducts Rule 

DE Diatomaceous Earth 

DIC Differential Interference Contrast 

(microscopy) 

EA Economic Analysis 

EPA United States Environmental 

Protection Agency 

GAC Granular Activated Carbon 

GWUDI Ground Water Under the 

Direct Influence of Surface Water 

HAA5 Five Haloacetic Acids 

(Monochloroacetic, Dichloroacetic, 

Trichloroacetic, Monobromoacetic 

and Dibromoacetic Acids) 

ICR Information Collection Rule (also 

Information Collection Request) 

ICRSS Information Collection Rule 

Supplemental Surveys 


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ICRSSM Information Collection Rule 

Supplemental Survey of Medium 

Systems 

ICRSSL Information Collection Rule 

Supplemental Survey of Large 

Systems 

IESWTR Interim Enhanced Surface 

Water Treatment Rule 

Log Logarithm (common, base 10) 

LRAA Locational Running Annual 

Average 

LRV Log Removal Value 

LT1ESWTR Long Term 1 Enhanced 

Surface Water Treatment Rule 

LT2ESWTR Long Term 2 Enhanced 

Surface Water Treatment Rule 

MCL Maximum Contaminant Level 

MCLG Maximum Contaminant Level 

Goal 

MG Million Gallons 

M–DBP Microbial and Disinfectants/ 

Disinfection Byproducts 

MF Microfiltration 

NPDWR National Primary Drinking 

Water Regulation 

NTTAA National Technology Transfer 

and Advancement Act 

NTU Nephelometric Turbidity Unit 

OMB Office of Management and 

Budget 

PE Performance Evaluation 

PWS Public Water System 

QC Quality Control 

QCRV Quality Control Release Value 

RAA Running Annual Average 

RFA Regulatory Flexibility Act 

RO Reverse Osmosis 

SAB Science Advisory Board 

SBAR Small Business Advocacy 

Review 

SDWA Safe Drinking Water Act 

SWAP Source Water Assessment 

Program 

SWTR Surface Water Treatment Rule 

TCR Total Coliform Rule 

TTHM Total Trihalomethanes 

UF Ultrafiltration 

UMRA Unfunded Mandates Reform 

Act 

Table of Contents 

I. General Information 

A. Who Is Regulated by This Action? 

II. Summary of the Final Rule 

A. Why Is EPA Promulgating the 

LT2ESWTR? 

B. What Does the LT2ESWTR Require? 

1. Source water monitoring 

2. Additional treatment for 

Cryptosporidium 

3. Uncovered finished water storage 

facilities 

C. Will This Regulation Apply to My Water 

System? 

III. Background Information 

A. Statutory Requirements and Legal 

Authority 

B. Existing Regulations for Microbial 

Pathogens in Drinking Water 

1. Surface Water Treatment Rule 

2. Total Coliform Rule 

3. Interim Enhanced Surface Water 

Treatment Rule 

4. Long Term 1 Enhanced Surface Water 

Treatment Rule 

5. Filter Backwash Recycle Rule 

C. Concern with Cryptosporidium in 

Drinking Water 

1. Introduction 

2. What is Cryptosporidium? 

3. Cryptosporidium health effects 

4. Efficacy of water treatment processes on 

Cryptosporidium 

5. Epidemic and endemic disease from 

Cryptosporidium 

D. Specific Concerns Following the 

IESWTR and LT1ESWTR 

E. New Information on Cryptosporidium 

Risk Management 

1. Infectivity 

2. Occurrence 

3. Analytical methods 

4. Treatment 

F. Federal Advisory Committee 

Recommendations 

IV. Explanation of Today’s Action 

A. Source Water Monitoring Requirements 

1. Today’s rule 

a. Sampling parameters and frequency 

b. Sampling location 

c. Sampling schedule 

d. Plants operating only part of the year 

e. Failing to monitor 

f. Providing treatment instead of 

monitoring 

g. Grandfathering previously collected data 

h. Ongoing watershed assessment 

i. Second round of monitoring 

j. New source monitoring 

2. Background and analysis 

a. Sampling parameters and frequency 

b. Sampling location 

c. Sampling schedule 

d. Plants operating only part of the year 

e. Failing to monitor 

f. Grandfathering previously collected data 

g. Ongoing watershed assessment 

h. Second round of monitoring 

3. Summary of major comments 

a. Sampling parameters and frequency 

b. Sampling location 

c. Sampling schedule 

d. Plants operating only part of the year 

e. Failing to monitor 

f. Providing treatment instead of 

monitoring 

g. Grandfathering previously collected data 

h. Ongoing watershed assessment 

i. Second round of monitoring 

j. New source monitoring 

B. Filtered System Cryptosporidium 

Treatment Requirements 

1. Today’s rule 

a. Bin classification 

b. Bin treatment requirements 

2. Background and analysis 

a. Basis for targeted treatment requirements 

b. Basis for bin concentration ranges and 

treatment requirements 

3. Summary of major comments 

C. Unfiltered System Cryptosporidium 

Treatment Requirements 

1. Today’s rule 

a. Determination of mean Cryptosporidium 

level 

b. Cryptosporidium treatment requirements 

c. Use of two disinfectants 

2. Background and analysis 

a. Basis for Cryptosporidium treatment 

requirements 

b. Basis for requiring the use of two 

disinfectants 

c. Filtration avoidance 

3. Summary of major comments 

D. Options for Systems to Meet 

Cryptosporidium Treatment 

Requirements 

1. Microbial toolbox overview 

2. Watershed control program 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

3. Alternative source 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

4. Pre-sedimentation with coagulant 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

5. Two-stage lime softening 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

6. Bank filtration 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

7. Combined filter performance 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

8. Individual filter performance 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

9. Demonstration of performance 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

10. Bag and cartridge filtration 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

11. Membrane filtration 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

12. Second stage filtration 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

13. Slow sand filtration 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

14. Ozone and chlorine dioxide 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

15. Ultraviolet light 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

E. Disinfection Benchmarking for Giardia 

lamblia and Viruses 

1. Today’s rule 

2. Background and analysis 

3. Summary of major comments 

F. Requirements for Systems with 

Uncovered Finished Water Storage 

Facilities 

1. Today’s rule 


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2. Background and analysis 

a. Types and sources of contaminants in 

open reservoirs 

b. Regulatory approaches to reduce risk 

from contamination in open reservoirs 

c. Definition of uncovered finished water 

storage facility 

3. Summary of major comments 

G. Compliance Schedules 

1. Today’s rule 

2. Background and analysis 

3. Summary of major comments 

H. Public Notice Requirements 

1. Today’s rule 

2. Background and analysis 

3. Summary of major comments 

I. Reporting Source Water Monitoring 

Results 

1. Today’s rule 

2. Background and analysis 

3. Summary of major comments 

J. Analytical Methods 

1. Analytical methods overview 

2. Cryptosporidium methods 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

3. E. coli methods 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

4. Turbidity methods 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

K. Laboratory Approval 

1. Cryptosporidium laboratory approval 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

2. E. coli laboratory approval 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

3. Turbidity analyst approval 

a. Today’s rule 

b. Background and analysis 

c. Summary of major comments 

L. Requirements for Sanitary Surveys 

Conducted by EPA 

1. Today’s rule 

2. Background and analysis 

3. Summary of major comments 

M. Variances and Exemptions 

1. Variances 

2. Exemptions 

V. State Implementation 

A. Today’s Rule 

1. Special State primacy requirements 

2. State recordkeeping requirements 

3. State reporting requirements 

4. Interim primacy 

B. Background and Analysis 

C. Summary of Major Comments 

VI. Economic Analysis 

A. What Regulatory Alternatives Did the 

Agency Consider? 

B. What Analyses Support Today’s Final 

Rule? 

C. What Are the Benefits of the 

LT2ESWTR? 

1. Nonquantified benefits 

2. Quantified benefits 

a. Filtered PWSs 

b. Unfiltered PWSs 

3. Timing of benefits accrual (latency) 

D. What Are the Costs of the LT2ESWTR? 

1. Total annualized present value costs 

2. PWS costs 

a. Source water monitoring costs 

b. Filtered PWSs treatment costs 

c. Unfiltered PWSs treatment costs 

d. Uncovered finished water storage 

facilities 

e. Future monitoring costs 

f. Sensitivity analysis—influent bromide 

levels on technology selection for filtered 

plants 

3. State/Primacy agency costs 

4. Non-quantified costs 

E. What Are the Household Costs of the 

LT2ESWTR? 

F. What Are the Incremental Costs and 

Benefits of the LT2ESWTR? 

H. Are there Increased Risks From Other 

Contaminants? 

I. What Are the Effects of the Contaminant 

on the General Population and Groups 

within the General Populations that Are 

Identified as Likely to be at Greater Risk 

of Adverse Health Effects? 

J. What Are the Uncertainties in the Risk, 

Benefit, and Cost Estimates for the 

LT2ESWTR? 

K. What Is the Benefit/Cost Determination 

for the LT2ESWTR? 

L. Summary of Major Comments 

1. Cryptosporidium occurrence 

a. Quality of the ICR and ICRSS data sets 

b. Treatment of observed zeros 

2. Drinking water consumption 

3. Cryptosporidium infectivity 

4. Valuation of benefits 

a. Valuation of morbidity 

b. Valuation of lost time under the 

enhanced cost of illness (COI) approach 

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 and 

Safety Risks 

H. Executive Order 13211: Actions 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 LT2ESWTR on the 

Technical, Financial, and Managerial 

Capacity of Public Water Systems 

N. Congressional Review Act 

VIII. References 

II. Summary of the Final Rule 

A. Why Is EPA Promulgating the 

LT2ESWTR? 

EPA is promulgating the Long Term 2 

Enhanced Surface Water Treatment Rule 

(LT2ESWTR) to further protect public 

health against Cryptosporidium and 

other microbial pathogens in drinking 

water. Cryptosporidium is a protozoan 

parasite that is common in surface water 

used as drinking water sources by 

public water systems (PWSs). In 

drinking water, Cryptosporidium is a 

particular concern because it is highly 

resistant to chemical disinfectants like 

chlorine. When ingested, 

Cryptosporidium can cause acute 

gastrointestinal illness, which may be 

severe and sometimes fatal for people 

with weakened immune systems. 

Cryptosporidium has been identified as 

the cause of a number of waterborne 

disease outbreaks in the United States 

(details in section III.C). 

The LT2ESWTR supplements existing 

microbial treatment regulations and 

targets PWSs with higher potential risk 

from Cryptosporidium. Existing 

regulations require most PWSs using 

surface water sources to filter the water, 

and those PWSs that are required to 

filter must remove at least 99 percent (2- 

log) of the Cryptosporidium (details in 

section III.B). As explained in the 

proposal for today’s rule (68 FR 47640, 

August 11, 2003) (USEPA 2003a), new 

data on the occurrence, infectivity, and 

treatment of Cryptosporidium in 

drinking water indicate that existing 

regulations are sufficient for most PWSs. 

A subset of PWSs with greater 

vulnerability to Cryptosporidium, 

however, requires additional treatment. 

In particular, recent national survey 

data show that the level of 

Cryptosporidium in the sources of most 

filtered PWSs is lower than previously 

estimated, but also that 

Cryptosporidium levels vary widely 

from source to source. Accordingly, a 

subset of filtered PWSs has relatively 

high levels of source water 

Cryptosporidium contamination. In 

addition, data from human health 

studies indicate that the potential for 

Cryptosporidium to cause infection is 

likely greater than previously 

recognized (details in section III.E). 

These findings have led EPA to 

conclude that existing requirements do 

not provide adequate public health 

protection in filtered PWSs with the 

highest source water Cryptosporidium 

levels. Consequently, EPA is 

establishing risk-targeted additional 

treatment requirements for such filtered 

PWSs under the LT2ESWTR. 


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For PWSs that use surface water 

sources and are not required to filter 

(i.e., unfiltered PWSs), existing 

regulations do not require any treatment 

for Cryptosporidium. New survey data 

suggest that typical Cryptosporidium 

levels in the treated water of unfiltered 

PWSs are higher than in the treated 

water of filtered PWSs (USEPA 2003a). 

Thus, Cryptosporidium treatment by 

unfiltered PWSs is needed to achieve 

comparable public health protection 

(details in section III.E). Further, results 

from recent treatment studies have 

allowed EPA to develop standards for 

the inactivation of Cryptosporidium by 

ozone, ultraviolet (UV) light, and 

chlorine dioxide (details in section 

IV.D). Based on these developments, 

EPA is establishing requirements under 

the LT2ESWTR for all unfiltered PWSs 

to treat for Cryptosporidium, with the 

required degree of treatment depending 

on the source water contamination 

level. 

Additionally, the LT2ESWTR 

addresses risks in uncovered finished 

water storage facilities, in which treated 

water can be subject to significant 

contamination as a result of runoff, bird 

and animal wastes, human activity, 

algal growth, insects, fish, and airborne 

deposition (details in section IV.F). 

Existing regulations prohibit the 

building of new uncovered finished 

water storage facilities but do not deal 

with existing ones. Under the 

LT2ESWTR, PWSs must limit potential 

risks by covering or treating the 

discharge of such storage facilities. 

Most of the requirements in today’s 

final LT2ESWTR reflect consensus 

recommendations from the Stage 2 

Microbial and Disinfection Byproducts 

(M–DBP) Federal Advisory Committee. 

These recommendations are set forth in 

the Stage 2 M–DBP Agreement in 

Principle (65 FR 83015, December 29, 

2000) (USEPA 2000a). 

B. What Does the LT2ESWTR Require? 

1. Source Water Monitoring 

The LT2ESWTR requires PWSs using 

surface water or ground water under the 

direct influence (GWUDI) of surface 

water to monitor their source water (i.e., 

the influent water entering the treatment 

plant) to determine an average 

Cryptosporidium level. As described in 

the next section, monitoring results 

determine the extent of 

Cryptosporidium treatment 

requirements under the LT2ESWTR. 

Large PWSs (serving at least 10,000 

people) must monitor for 

Cryptosporidium (plus E. coli and 

turbidity in filtered PWSs) for a period 

of two years. To reduce monitoring 

costs, small filtered PWSs (serving fewer 

than 10,000 people) initially monitor 

just for E. coli for one year as a 

screening analysis and are required to 

monitor for Cryptosporidium only if 

their E. coli levels exceed specified 

‘‘trigger’’ values. Small filtered PWSs 

that exceed the E. coli trigger, as well as 

all small unfiltered PWSs, must monitor 

for Cryptosporidium for one or two 

years, depending on the sampling 

frequency (details sections IV.A). 

Under the LT2ESWTR, specific 

criteria are set for sampling frequency 

and schedule, sampling location, using 

previously collected data (i.e., 

grandfathering), providing treatment 

instead of monitoring, sampling by 

PWSs that use surface water for only 

part of the year, and monitoring of new 

plants and sources (details in section 

IV.A). The LT2ESWTR also establishes 

requirements for reporting of monitoring 

results (details in section IV.I), using 

analytical methods (details in section 

IV.J), and using approved laboratories 

(details in section IV.K). 

The date for PWSs to begin 

monitoring is staggered by PWS size, 

with smaller PWSs starting at a later 

time than larger ones (details in section 

IV.G). Today’s rule also requires a 

second round of monitoring to begin 

approximately 6.5 years after the first 

round concludes in order to determine 

if source water quality has changed to 

a degree that should affect treatment 

requirements (details in section IV.A). 

2. Additional Treatment for 

Cryptosporidium 

The LT2ESWTR establishes risktargeted treatment technique 

requirements to control 

Cryptosporidium in PWSs using surface 

water or GWUDI. These treatment 

requirements supplement those 

established by existing regulations, all 

of which remain in effect under the 

LT2ESWTR. 

Filtered PWSs will be classified in 

one of four treatment categories (or 

‘‘bins’’) based on the results of the 

source water Cryptosporidium 

monitoring described in the previous 

section. This bin classification 

determines the degree of additional 

Cryptosporidium treatment, if any, the 

filtered PWS must provide. Occurrence 

data indicate that the majority of filtered 

PWSs will be classified in Bin 1, which 

carries no additional treatment 

requirements. PWSs classified in Bins 2, 

3, or 4 must achieve 1.0- to 2.5-log of 

treatment (i.e., 90 to 99.7 percent 

reduction) for Cryptosporidium over 

and above that provided with 

conventional treatment. Different 

additional treatment requirements may 

apply to PWSs using other than 

conventional treatment, such as direct 

filtration, membranes, or cartridge filters 

(details in section. IV.B). Filtered PWSs 

must meet the additional 

Cryptosporidium treatment required in 

Bins 2, 3, or 4 by using one or more 

treatment or control processes from a 

‘‘microbial toolbox’’ of options (details 

in section. IV.D). 

The LT2ESWTR requires all 

unfiltered PWSs to provide at least 2-log 

(i.e., 99 percent) inactivation of 

Cryptosporidium. If the average source 

water Cryptosporidium level exceeds 

0.01 oocysts/L based on the monitoring 

described in the previous section, the 

unfiltered PWS must provide at least 3- 

log (i.e., 99.9 percent) inactivation of 

Cryptosporidium. Further, under the 

LT2ESWTR, unfiltered PWSs must 

achieve their overall inactivation 

requirements (including Giardia lamblia 

and virus inactivation as established by 

earlier regulations) using a minimum of 

two disinfectants (details in section 

IV.C). 

3. Uncovered Finished Water Storage 

Facilities 

Under the LT2ESWTR, PWSs with 

uncovered finished water storage 

facilities must take steps to address 

contamination risks. Existing 

regulations require PWSs to cover all 

new storage facilities for finished water 

but do not address existing uncovered 

finished water storage facilities. Under 

the LT2ESWTR, PWSs using uncovered 

finished water storage facilities must 

either cover the storage facility or treat 

the storage facility discharge to achieve 

inactivation and/or removal of 4-log 

virus, 3-log Giardia lamblia, and 2-log 

Cryptosporidium on a State-approved 

schedule (details in section. IV.F). 

C. Will This Regulation Apply to My 

Water System? 

The LT2ESWTR applies to all PWSs 

using surface water or GWUDI, 

including both large and small PWSs, 

community and non-community PWSs, 

and non-transient and transient PWSs. 

Wholesale PWSs must comply with the 

requirements of today’s rule based on 

the population of the largest PWS in the 

combined distribution system. 

Consecutive PWSs that purchase treated 

water from wholesale PWSs that fully 

comply with the monitoring and 

treatment requirements of the 

LT2ESWTR are not required to take 

additional steps for that water under 

today’s rule. 

III. Background Information 

The sections in this part provide 

summary background information for 


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today’s final LT2ESWTR. Individual 

sections address the following topics: 

(A) Statutory requirements and legal 

authority for the LT2ESWTR; (B) 

existing regulations for microbial 

pathogens in drinking water; (C) the 

problem with Cryptosporidium in 

drinking water; (D) specific public 

health concerns addressed by the 

LT2ESWTR; (E) new information for 

Cryptosporidium risk management in 

PWSs; and (F) recommendations from 

the Stage 2 M-DBP Advisory Committee 

for the LT2ESWTR. For additional 

information on these topics, see the 

proposed LT2ESWTR (USEPA 2003a) 

and supporting technical material where 

cited. 

A. Statutory Requirements and Legal 

Authority 

The Safe Drinking Water Act (SDWA 

or the Act), as amended in 1996, 

requires EPA to publish a maximum 

contaminant level goal (MCLG) and 

promulgate a national primary drinking 

water regulation (NPDWR) with 

enforceable requirements for any 

contaminant that the Administrator 

determines may have an adverse effect 

on the health of persons, is known to 

occur or has a substantial likelihood of 

occurring in public water systems 

(PWSs) 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 PWSs (section 1412 

(b)(1)(A)). 

MCLGs are non-enforceable health 

goals and are to be 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 (sections 1412(b)(4) and 

1412(a)(3)). EPA established an MCLG 

of zero for Cryptosporidium under the 

Interim Enhanced Surface Water 

Treatment Rule (IESWTR) (63 FR 69478, 

December 16, 1998) (USEPA 1998a). In 

today’s rule, the Agency is not making 

any changes to the current MCLG for 

Cryptosporidium. 

The Act also requires each NPDWR 

for which an MCLG is established to 

specify a maximum contaminant level 

(MCL) that is as close to the MCLG as 

is feasible (sections 1412(b)(4) and 

1401(1)(C)). The Agency is authorized to 

promulgate an NPDWR that requires the 

use of a treatment technique in lieu of 

establishing an MCL if the Agency finds 

that it is not economically or 

technologically feasible to ascertain the 

level of the contaminant (sections 

1412(b)(7)(A) and 1401(1)(C)). The Act 

specifies that in such cases, the Agency 

shall identify those treatment 

techniques that would prevent known 

or anticipated adverse effects on the 

health of persons to the extent feasible 

(section 1412(b)(7)(A)). 

The Agency has concluded that it is 

not currently economically or 

technologically feasible for PWSs to 

determine the level of Cryptosporidium 

in finished drinking water for the 

purpose of compliance with a finished 

water standard. As described in section 

IV.C, the LT2ESWTR is designed to 

protect public health by lowering the 

level of infectious Cryptosporidium in 

finished drinking water to less than 1 

oocyst/10,000 L. Approved 

Cryptosporidium analytical methods, 

which are described in section IV.K, are 

not sufficient to routinely determine the 

level of Cryptosporidium at this 

concentration. Consequently, the 

LT2ESWTR relies on treatment 

technique requirements to reduce health 

risks from Cryptosporidium in PWSs. 

When proposing an NPDWR that 

includes an MCL or treatment 

technique, the Act requires EPA to 

publish and seek public comment on an 

analysis of health risk reduction and 

costs. This includes an analysis of 

quantifiable and nonquantifiable costs 

and health risk reduction benefits, 

incremental costs and benefits of each 

alternative considered, the effects of the 

contaminant upon sensitive 

subpopulations (e.g., infants, children, 

pregnant women, the elderly, and 

individuals with a history of serious 

illness), any increased risk that may 

occur as the result of compliance, and 

other relevant factors (section 

1412(b)(3)(C)). EPA’s analysis of health 

benefits and costs associated with the 

LT2ESWTR is presented in the 

Economic Analysis of the LT2ESWTR 

(USEPA 2005a) and is summarized in 

section VI of this preamble. The Act 

does not, however, authorize the 

Administrator to use a determination of 

whether benefits justify costs to 

establish an MCL or treatment technique 

requirement for the control of 

Cryptosporidium (section 1412(b)(6)(C)). 

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

Act requires EPA to promulgate a Stage 

2 Disinfectants and Disinfection 

Byproducts Rule within 18 months after 

promulgation of the LT1ESWTR, which 

occurred on January 14, 2002. 

Consistent with statutory requirements 

for risk balancing (section 

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

LT2ESWTR in conjunction with the 

Stage 2 DBPR to ensure parallel 

protection from microbial and DBP 

risks. 

B. Existing Regulations for Microbial 

Pathogens in Drinking Water 

This section summarizes existing 

rules that regulate treatment for 

pathogenic microorganisms by PWSs 

using surface water sources. The 

LT2ESWTR supplements these rules 

with additional risk-targeted 

requirements, but does not withdraw 

any existing requirements. 

1. Surface Water Treatment Rule 

The Surface Water Treatment Rule 

(SWTR) (54 FR 27486, June 29, 1989) 

(USEPA 1989a) applies to all PWSs 

using surface water or ground water 

under the direct influence (GWUDI) of 

surface water as sources (i.e., Subpart H 

PWSs). It established MCLGs of zero for 

Giardia lamblia, viruses, and Legionella, 

and includes the following treatment 

technique requirements to reduce 

exposure to pathogenic microorganisms: 

(1) Filtration, unless specific avoidance 

criteria are met; (2) maintenance of a 

disinfectant residual in the distribution 

system; (3) removal and/or inactivation 

of 3-log (99.9%) of Giardia lamblia and 

4-log (99.99%) of viruses; (4) maximum 

allowable turbidity in the combined 

filter effluent (CFE) of 5 nephelometric 

turbidity units (NTU) and 95th 

percentile CFE turbidity of 0.5 NTU or 

less for plants using conventional 

treatment or direct filtration (with 

different standards for other filtration 

technologies); and (5) watershed 

protection and source water quality 

requirements for unfiltered PWSs. 

2. Total Coliform Rule 

The Total Coliform Rule (TCR) (54 FR 

27544, June 29, 1989) (USEPA 1989b) 

applies to all PWSs. It established an 

MCLG of zero for total and fecal 

coliform bacteria and an MCL based on 

the percentage of positive samples 

collected during a compliance period. 

Coliforms are used as an indicator of 

fecal contamination and to determine 

the integrity of the water treatment 

process and distribution system. Under 

the TCR, no more than 5 percent of 

distribution system samples collected in 

any month may contain coliform 

bacteria (no more than 1 sample per 

month may be coliform positive in those 

PWSs that collect fewer than 40 samples 

per month). The number of samples to 

be collected in a month is based on the 

number of people served by the PWS. 

3. Interim Enhanced Surface Water 

Treatment Rule 

The Interim Enhanced Surface Water 

Treatment Rule (IESWTR) (63 FR 69478, 

December 16, 1998) (USEPA 1998a) 

applies to PWSs serving at least 10,000 

people and using surface water or 


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GWUDI sources. Key provisions 

established by the IESWTR include the 

following: (1) An MCLG of zero for 

Cryptosporidium; (2) Cryptosporidium 

removal requirements of 2-log (99 

percent) for PWSs that filter; (3) more 

stringent CFE turbidity performance 

standards of 1.0 NTU as a maximum 

and 0.3 NTU or less at the 95th 

percentile monthly for treatment plants 

using conventional treatment or direct 

filtration; (4) requirements for 

individual filter turbidity monitoring; 

(5) disinfection benchmark provisions to 

assess the level of microbial protection 

that PWSs provide as they take steps to 

comply with new DBP standards; (6) 

inclusion of Cryptosporidium in the 

definition of GWUDI and in the 

watershed control requirements for 

unfiltered PWSs; (7) requirements for 

covers on new finished water storage 

facilities; and (8) sanitary surveys for all 

surface water systems regardless of size. 

The IESWTR was developed in 

conjunction with the Stage 1 

Disinfectants and Disinfection 

Byproducts Rule (Stage 1 DBPR) (63 FR 

69389, December 16, 1998) (USEPA 

1998b), which reduced allowable levels 

of certain DBPs, including 

trihalomethanes, haloacetic acids, 

chlorite, and bromate. 

4. Long Term 1 Enhanced Surface Water 

Treatment Rule 

The Long Term 1 Enhanced Surface 

Water Treatment Rule ( LT1ESWTR) (67 

FR 1812, January 14, 2002) (USEPA 

2002a) builds upon the microbial 

control provisions established by the 

IESWTR for large PWSs through 

extending similar requirements to small 

PWSs. The LT1ESWTR applies to PWSs 

that use surface water or GWUDI as 

sources and that serve fewer than 10,000 

people. Like the IESWTR, the 

LT1ESWTR established the following: 2- 

log (99 percent) Cryptosporidium 

removal requirements by PWSs that 

filter; individual filter turbidity 

monitoring and more stringent 

combined filter effluent turbidity 

standards for conventional and direct 

filtration plants; disinfection profiling 

and benchmarking; inclusion of 

Cryptosporidium in the definition of 

GWUDI and in the watershed control 

requirements for unfiltered PWSs; and 

the requirement that new finished water 

storage facilities be covered. 

5. Filter Backwash Recycle Rule 

The Filter Backwash Recycling Rule 

(FBRR) (66 FR 31085, June 8, 2001) 

(USEPA 2001a) requires PWSs to 

consider the potential risks associated 

with recycling contaminants removed 

during the filtration process. The 

provisions of the FBRR apply to all 

PWSs that recycle, regardless of 

population served. In general, the 

provisions include the following: (1) 

PWSs must return certain recycle 

streams to a point in the treatment 

process that is prior to primary 

coagulant addition unless the State 

specifies an alternative location; (2) 

direct filtration PWSs recycling to the 

treatment process must provide detailed 

recycle treatment information to the 

State; and (3) certain conventional 

PWSs that practice direct recycling must 

perform a one-month, one-time 

recycling self assessment. 

C. Concern With Cryptosporidium in 

Drinking Water 

1. Introduction 

EPA is promulgating the LT2ESWTR 

to reduce the public health risk 

associated with Cryptosporidium in 

drinking water. This section describes 

the general basis for this public health 

concern through reviewing information 

in several areas: the nature of 

Cryptosporidium, health effects, efficacy 

of water treatment processes, and the 

incidence of epidemic and endemic 

disease. Further information about 

Cryptosporidium is available in the 

following documents: Cryptosporidium: 

Human Health Criteria Document 

(USEPA 2001b), Cryptosporidium: 

Drinking Water Advisory (USEPA 

2001c), and Cryptosporidium: Risks for 

Infants and Children (USEPA 2001d). 

2. What Is Cryptosporidium? 

Cryptosporidium is a protozoan 

parasite that lives and reproduces 

entirely in one host. Ingestion of 

Cryptosporidium can cause 

cryptosporidiosis, a gastrointestinal (GI) 

illness. Cryptosporidium is excreted in 

feces. Transmission of cryptosporidiosis 

occurs through consumption of water or 

food contaminated with feces or by 

direct or indirect contact with infected 

persons or animals (Casemore 1990). 

In the environment, Cryptosporidium 

is present as a thick-walled oocyst 

containing four organisms (sporozoites); 

the oocyst wall insulates the sporozoites 

from harsh environmental conditions. 

Oocysts are 4–5 microns in length and 

width. Upon a host’s ingestion of 

oocysts, enzymes and chemicals 

produced by the host’s digestive system 

cause the oocyst to excyst, or break 

open. The excysted sporozoites embed 

themselves in the surfaces of the 

epithelial cells of the lower small 

intestine. The organisms then begin 

absorbing nutrients from their host cells. 

When these organisms sexually 

reproduce, they produce thick- and 

thin-walled oocysts. The host excretes 

the thick-walled oocysts in its feces; 

thin-walled oocysts excyst within the 

host and contribute to further host 

infection. 

The exact mechanism by which 

Cryptosporidium causes GI illness is not 

known. Factors may include damage to 

intestinal structure and cells, changes in 

the absorption/secretion processes of 

the intestine, toxins produced by 

Cryptosporidium or the host, and 

proteins that allow Cryptosporidium to 

adhere to host cell surfaces (Carey et al. 

2004). 

Upon excretion, Cryptosporidium 

oocysts may survive for months in 

various environmental media, including 

soil, river water, seawater, and human 

and cattle feces at ambient temperatures 

(Kato et al. 2001, Pokorny et al. 2002, 

Fayer et al. 1998a and 1998b, and 

Robertson et al. 1992). Cryptosporidium 

can also withstand temperatures as low 

as ¥20 °C for periods of a few hours 

(Fayer and Nerad 1996) but are 

susceptible to desiccation (Robertson et 

al. 1992). 

Cryptosporidium is a widespread 

contaminant in surface water used as 

drinking water supplies. For example, 

among 67 drinking water sources 

surveyed by LeChevallier and Norton 

(1995), 87 percent had positive samples 

for Cryptosporidium. A more recent 

survey of 80 medium and large PWSs 

conducted by EPA detected 

Cryptosporidium in 85 percent of water 

sources (USEPA 2003a). 

Cryptosporidium contamination can 

come from animal agriculture, 

wastewater treatment plant discharges, 

slaughterhouses, birds, wild animals, 

and other sources of fecal matter. 

Because different species of 

Cryptosporidium are very similar in 

morphology, researchers have focused 

on genetic differences in trying to 

classify them. However, discussion on 

Cryptosporidium taxonomy is 

complicated by the fact that even within 

species or strains, there may be 

differences in infectivity and virulence. 

Cryptosporidium parvum (C. parvum) 

has been the primary species of concern 

to humans. Until recently, some 

researchers divided C. parvum into two 

primary strains, genotype 1, which 

infects humans, and genotype 2, which 

infects both humans and cattle (Carey et 

al. 2004). In 2002, Morgan-Ryan et al. 

proposed that genotype 1 be designated 

a separate species, C. hominis. 

Additional Cryptosporidium species 

infecting other mammals, birds, and 

reptiles have been documented. In some 

cases, these species can infect both 

immunocompromised (having 

weakened immune systems) and 


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otherwise healthy humans (Carey et al. 

2004). 

3. Cryptosporidium Health Effects 

Cryptosporidium infection is 

characterized by mild to severe 

diarrhea, dehydration, stomach cramps, 

and/or a slight fever. Incubation is 

thought to range from 2 to 10 days 

(Arrowood 1997). Symptoms typically 

last from several days to 2 weeks, 

though in a small percentage of cases, 

the symptoms may persist for months or 

longer in otherwise healthy individuals. 

Symptoms may be more severe in 

immunocompromised persons (Frisby et 

al. 1997, Carey et al. 2004). Such 

persons include those with AIDS, 

cancer patients undergoing 

chemotherapy, organ transplant 

recipients treated with drugs that 

suppress the immune system, and 

patients with autoimmune disorders 

(e.g., Lupus). In AIDS patients, 

Cryptosporidium has been found in the 

lungs, ear, stomach, bile duct, and 

pancreas in addition to the small 

intestine (Farthing 2000). 

Immunocompromised patients with 

severe persistent cryptosporidiosis may 

die (Carey et al. 2004). Besides the 

immunocompromised, children and the 

elderly may be at higher risk from 

Cryptosporidium than the general 

population (discussed in section VII.G). 

Studies with human volunteers have 

demonstrated that a low dose of C. 

parvum (e.g., 10 oocysts) is sufficient to 

cause infection in healthy adults, 

although some strains are more 

infectious than others (DuPont et al. 

1995, Chappell et al. 1999, Okhuysen et 

al. 2002). Studies of immunosuppressed 

adult mice have demonstrated that a 

single viable oocyst can induce C. 

parvum infections (Yang et al. 2000, 

Okhuysen et al. 2002). The lowest dose 

tested in any of the human challenge 

studies was 10 oocysts. Because 

drinking water exposures are generally 

projected to be at lower levels (e.g., 1 

oocyst), statistical modeling is necessary 

to project the effects of such exposure. 

Following the advice of its Science 

Advisory Board (SAB), EPA has 

developed a range of models to predict 

effects of exposure to low doses of 

Cryptosporidium. These models are 

discussed in section VI and in the 

LT2ESWTR Economic Analysis (USEPA 

2005a). 

The degree and duration of the 

immune response to Cryptosporidium is 

not well characterized. In a study by 

Chappell et al. (1999), volunteers with 

IgG Cryptosporidium antibodies in their 

blood were immune to low doses of 

oocysts. The ID50 (the dose that infects 

50 percent of the challenged population) 

was 1,880 oocysts for those individuals 

compared to 132 oocysts for individuals 

that tested negative for those antibodies. 

However, earlier studies did not observe 

a correlation between the development 

of antibodies after Cryptosporidium 

infection and subsequent protection 

from illness (Okhuysen et al. 1998). 

No cure for cryptosporidiosis is 

known. Medical care usually involves 

treatment for dehydration and nutrient 

loss. Certain antimicrobial drugs like 

Azithromycin, Paromomycin, and 

nitazoxanide, the only drug approved 

for cryptosporidiosis in children, have 

been partially effective in treating 

immunocompromised patients 

(Rossignol et al. 1998). Therapies used 

to treat retroviruses can be helpful in 

fighting cryptosporidiosis in people 

with AIDS and are more effective when 

used in conjunction with antimicrobial 

therapy. The effectiveness of 

antiretroviral therapy is thought to be 

related to the associated increase in 

white blood cells rather than the 

decrease in the amount of virus present. 

4. Efficacy of Water Treatment Processes 

on Cryptosporidium 

EPA is particularly concerned about 

Cryptosporidium because, unlike 

pathogens such as bacteria and most 

viruses, Cryptosporidium oocysts are 

highly resistant to standard 

disinfectants like chlorine and 

chloramines (Korich et al. 1990, 

Ransome et al. 1993, Finch et al. 1997). 

Consequently, control of 

Cryptosporidium in most treatment 

plants is dependent on physical removal 

processes. However, due to their size 

(4–5 microns), oocysts can sometimes 

pass through filters. 

Monitoring data on finished water 

show that Cryptosporidium is 

sometimes present in filtered, treated 

drinking water (LeChevallier et al. 1991, 

Aboytes et al. 2004). For example, 

Aboytes et al. (2004) analyzed 1,690 

finished water samples from 82 plants. 

Of these, 22 plants had at least one 

positive sample for infectious 

Cryptosporidium (1.4 percent of all 

samples were positive). All positive 

samples occurred at plants that met 

existing regulatory standards and many 

had very low turbidity. 

Waterborne outbreaks of 

cryptosporidiosis have occurred even in 

areas served by filtered surface water 

supplies (Solo-Gabriele and Neumeister, 

1996). In some cases, outbreaks were 

attributed to treatment deficiencies, but 

in others, the treatment provided by the 

water system met the regulatory 

requirements in place at that time. 

These data indicate that even surface 

water systems that filter and disinfect 

can still be vulnerable to 

Cryptosporidium, depending on the 

source water quality and treatment 

effectiveness. 

Certain alternative disinfectants can 

be more effective in treating for 

Cryptosporidium. Both ozone and 

chlorine dioxide have been shown to 

inactivate Cryptosporidium, albeit at 

doses much higher than those required 

to inactivate Giardia, which has 

typically been used to set disinfectant 

doses (summarized in USEPA 2003a). 

Studies have also demonstrated a 

synergistic effect of treatment using 

ozone followed by chlorine or 

monochloramine (Rennecker et al. 2000, 

Driedger et al. 2001). Significantly, UV 

light has recently been shown to achieve 

high levels of Cryptosporidium 

inactivation at feasible doses 

(summarized in USEPA 2003a). 

Other processes that can help reduce 

Cryptosporidium levels in finished 

water include watershed management 

programs, pretreatment processes like 

bank filtration, and additional 

clarification and filtration processes 

during water treatment. Further, 

optimizing treatment performance and 

achieving very low levels of turbidity in 

the finished water has been shown to 

improve Cryptosporidium removal in 

treatment plants (summarized in USEPA 

2003a). 

5. Epidemic and Endemic Disease From 

Cryptosporidium 

Cryptosporidium has caused a 

number of waterborne disease outbreaks 

since 1984 when the first was reported 

in the United States. Data from the 

Centers for Disease Control and 

Prevention (CDC) include ten outbreaks 

caused by Cryptosporidium in drinking 

water between 1984 and 2000, with 

approximately 421,000 cases of illness 

(CDC 1993, 1996, 1998, 2000, and 2002). 

The most serious outbreak occurred in 

1993 in Milwaukee; an estimated 

403,000 people became sick (MacKenzie 

et al. 1994), and at least 50 

Cryptosporidium-associated deaths 

occurred among the severely 

immunocompromised (Hoxie et al. 

1997). Further, a study by McDonald et 

al. (2001) using blood samples from 

Milwaukee children suggests that 

Cryptosporidium infection was more 

widespread than might be inferred from 

the illness estimates by MacKenzie et al. 

(1994). 

The number of identified and 

reported outbreaks in the CDC database 

is believed to substantially understate 

the actual incidence of waterborne 

disease outbreaks and cases (Craun and 

Calderon 1996, National Research 

Council 1997). This under reporting is 


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due to a number of factors. Many people 

experiencing gastrointestinal illness do 

not seek medical attention. Where 

medical attention is provided, the 

pathogenic agent may not be identified 

through routine testing. Physicians and 

patients often lack sufficient 

information to attribute gastrointestinal 

illness to any specific origin, such as 

drinking water, and few States have an 

active outbreak surveillance program. In 

addition, if drinking water is 

investigated as the source of an 

outbreak, oocysts may not be detected in 

water samples even if they are present, 

due to limitations in analytical methods. 

Consequently, outbreaks may not be 

recognized in a community or, if 

recognized, may not be traced to a 

drinking water source. 

In addition, an unknown but probably 

significant portion of waterborne 

disease is endemic (i.e., isolated cases 

not associated with an outbreak) and, 

thus, is even more difficult to recognize. 

In an outbreak, if the pathogen has been 

identified, medical providers and public 

health investigators know what to look 

for. In endemic disease, there is no 

investigation, so the illness may never 

be identified, or if it is, it may not be 

linked to a source (e.g., drinking water, 

person-to-person transmission). In 

addition, where a pathogen is identified, 

lab results may not be reported to public 

health agencies. 

Because of this under reporting, the 

actual incidence of cryptosporidiosis 

associated with drinking water is 

unknown. However, indications of this 

incidence rate can be roughly 

extrapolated from different sources. 

Mead et al. (1999) estimated 

approximately 300,000 total cases of 

cryptosporidiosis annually that result in 

a physician visit, with 90 percent of 

these attributed to waterborne (drinking 

water and recreational water) and 

secondary transmission. This estimate is 

based on the percentage of stools that 

test positive for Cryptosporidium and 

applying this percentage to the 

approximately 15 million physician 

visits for diarrhea each year. While the 

fraction of cryptosporidiosis cases that 

result in a physician visit is unknown, 

Corso et al. (2003) reported that during 

the 1993 outbreak in Milwaukee, 

medical care was sought in 

approximately 12 percent of all 

cryptosporidiosis cases. 

Surveillance data from the CDC for 

2001 show an overall incidence of 1.5 

laboratory diagnosed cases of 

cryptosporidiosis per 100,000 

population (CDC, 2002). Although the 

fraction of all cryptosporidiosis cases 

that are laboratory confirmed is 

unknown, during the 1993 Milwaukee 

outbreak, 739 cases from an estimated 

403,000 cases total were confirmed by a 

laboratory (MacKenzie et al., 1994). 

These data indicate a ratio of 1 

laboratory confirmed case per 545 

people estimated to be ill with 

cryptosporidiosis. 

A few studies have attempted to 

determine exposure in certain areas by 

measuring seroprevalence of 

Cryptosporidium antibodies (the 

frequency at which antibodies are found 

in the blood). Detection of such 

antibodies (seropositivity), however, 

does not mean that the person actually 

experienced symptoms of 

cryptosporidiosis. An individual can be 

asymptomatically infected and still 

excrete oocysts. Seroprevalence, though, 

is still a method for estimating the 

exposure to Cryptosporidium that has 

occurred within a limited time period 

(the antibodies may last only a few 

months). 

Frost et al. (2001) conducted a paired 

city study, in which the serological 

response of blood donors in a city using 

ground water as its water source was 

compared to that of donors in a city 

using surface water as its source. Rates 

of seropositivity were higher (49 vs. 36 

percent) in the city with the surface 

water source. A similar study in two 

other cities (Frost et al. 2002) showed a 

seropositivity rate of 54 percent in the 

city served by surface water compared 

to 38 percent in the city served by 

ground water. These studies suggest that 

drinking water from surface sources 

may be a factor in the higher rates of 

seropositivity. 

D. Specific Concerns Following the 

IESWTR and LT1ESWTR 

In the LT2ESWTR, EPA is addressing 

a number of public health concerns that 

remain following implementation of the 

IESWTR and LT1ESWTR. These are as 

follows: 

• The need for filtered PWSs with 

higher levels of source water 

Cryptosporidium contamination to 

provide additional risk-based treatment 

for Cryptosporidium beyond IESWTR or 

LT1ESWTR requirements; 

• The need for unfiltered PWSs to 

provide risk-based treatment for 

Cryptosporidium to achieve equivalent 

public health protection with filtered 

PWSs; and 

• The need for PWSs with uncovered 

finished water storage facilities to take 

steps to reduce the risk of 

contamination of treated water prior to 

distribution to consumers. 

EPA and stakeholders identified each 

of these issues as public health concerns 

during development of the IESWTR 

(USEPA 1994, 1997). However, the 

Agency was unable to address these 

concerns in those regulations due to 

data gaps in the areas of health effects, 

occurrence, analytical methods, and 

treatment. Consequently, EPA followed 

a two-stage strategy for microbial and 

disinfection byproducts rules. Under 

this strategy, the IESWTR and 

LT1ESWTR were promulgated to 

provide an initial improvement in 

public health protection in large and 

small PWSs, respectively, while 

additional data to support a more 

comprehensive regulatory approach 

were collected. 

Since promulgating the IESWTR and 

LT1ESWTR, EPA has worked with 

stakeholders to collect and analyze 

significant new information to fill data 

gaps related to Cryptosporidium risk 

management in PWSs. The next section 

presents EPA’s evaluation of these data 

and their implications for both the risk 

of Cryptosporidium in filtered and 

unfiltered PWSs and the feasibility of 

steps to limit this risk. In addition, the 

Agency has evaluated additional data 

related to mitigating risks with 

uncovered finished water storage 

facilities, which are presented in section 

IV.F. 

E. New Information on Cryptosporidium 

Risk Management 

EPA and stakeholders determined 

during development of the IESWTR that 

in order to establish risk-based 

treatment requirements for 

Cryptosporidium, additional 

information was needed in the 

following areas: (1) The risk associated 

with a given level of Cryptosporidium 

(i.e., infectivity); (2) the occurrence of 

Cryptosporidium in PWS sources; (3) 

analytical methods that would suffice 

for making site-specific source water 

Cryptosporidium density estimates; and 

(4) the use of treatment technologies to 

achieve specific levels of 

Cryptosporidium disinfection (USEPA 

1997). 

In today’s final LT2ESWTR, EPA is 

promulgating risk-based 

Cryptosporidium treatment 

requirements for filtered and unfiltered 

PWSs. The Agency believes that the 

critical data gaps in the areas of 

infectivity, occurrence, analytical 

methods, and treatment that prevented 

the adoption of such an approach under 

earlier regulations have been addressed. 

The new information that the Agency 

and stakeholders evaluated in each of 

these areas and its significance for 

today’s LT2ESWTR are summarized as 

follows. See section VI.L for a summary 

of public comments on EPA’s use of 

Cryptosporidium infectivity and 


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occurrence data in assessing benefits of 

the LT2ESWTR. 

1. Infectivity 

Infectivity relates the probability of 

infection to the number of 

Cryptosporidium oocysts that a person 

ingests. It is used to predict the disease 

burden associated with a particular 

Cryptosporidium level in drinking 

water. Information on Cryptosporidium 

infectivity comes from dose-response 

studies where healthy human 

volunteers ingest different numbers of 

oocysts (i.e., the ‘‘dose’’) and are 

subsequently evaluated for signs of 

infection and illness (i.e., the 

‘‘response’’). 

Prior to the IESWTR, data from a 

human dose-response study of one 

Cryptosporidium isolate (IOWA) had 

been published (DuPont et al. 1995). 

Following IESWTR promulgation, a 

study of two additional isolates (TAMU 

and UCP) was completed and published 

(Okhuysen et al. 1999). This 1999 study 

also reanalyzed the IOWA study results. 

The measured infectivity of 

Cryptosporidium oocysts varied over a 

wide range in the Okhuysen et al. (1999) 

study. The UCP oocysts were much less 

infective than the IOWA oocysts, and 

the TAMU oocysts were much more 

infective. 

EPA analyzed these new data for the 

proposed LT2ESWTR using two 

different dose-response models. This 

analysis suggested that the overall 

infectivity of Cryptosporidium is greater 

than was estimated for the IESWTR 

(USEPA 2003a). Specifically, EPA 

estimated the mean probability of 

infection from ingesting a single 

infectious oocyst ranges from 7 to 10 

percent. This infection rate is 

approximately 20 times higher than the 

estimate of 0.4 percent used in the 

IESWTR. 

Since the publication of the proposed 

LT2ESWTR, EPA has evaluated three 

additional studies of Cryptosporidium 

infectivity. EPA also received a 

recommendation from the SAB that it 

analyze Cryptosporidium infectivity 

data using a wider range of models. 

Accordingly, EPA re-estimated 

Cryptosporidium infectivity using the 

new data and six different doseresponse models, including the two 

models used at proposal. Estimates from 

the new data and models for the 

probability of infection from ingesting a 

single infectious oocyst range from 4 to 

16 percent. A detailed discussion of the 

models and their varying assumptions is 

provided in the LT2ESWTR Economic 

Analysis (USEPA 2005a). 

As is apparent from these results, 

substantial uncertainty about the 

infectivity of Cryptosporidium remains 

in several areas. These include the 

variability in host susceptibility, 

response at very low oocyst doses 

typical of drinking water ingestion, and 

the relative infectivity and occurrence of 

different Cryptosporidium isolates in 

the environment. To address this 

uncertainty, EPA conducted its health 

risk reduction and benefits analyses 

using a representative range of model 

results. In the summary tables for these 

analyses, three sets of estimates are 

presented: A ‘‘high’’ estimate based on 

the model that showed the highest mean 

baseline risk; a ‘‘medium’’ estimate, 

based on the models and data used at 

proposal, which also happens to be in 

the middle of the range of estimates 

produced by the six models using the 

newly available data; and a ‘‘low’’

estimate, based on the model that 

showed the lowest mean baseline risk. 

These estimates should not be 

construed as upper and lower bounds 

on illnesses avoided and benefits. For 

each model, a distribution of effects is 

estimated, and the ‘‘high’’ and ‘‘low’’

estimates show only the means of these 

distributions for two different model 

choices. The detailed distribution of 

effects is presented for the proposal 

model in the Economic Analysis 

(USEPA 2005a). Further, the six doseresponse models used in this analysis 

do not cover all possible variations of 

models that might have been used with 

the data, and it is possible that estimates 

with other models would fall outside 

the range presented. However, as 

discussed in the Economic Analysis, 

EPA believes that the models used in 

the analyses reflect a reasonable range of 

results based on important dimensions 

of model choice. 

Regardless of which model is chosen, 

the available infectivity data suggest 

that the risk associated with a given 

concentration of Cryptosporidium is 

most likely higher than EPA had 

estimated for the IESWTR. This finding 

supports the need for increased 

treatment for Cryptosporidium as 

required under the LT2ESWTR. 

2. Occurrence 

Information on the occurrence of 

Cryptosporidium oocysts in drinking 

water sources is a critical parameter for 

assessing risk and the need for 

additional treatment for this pathogen. 

For the IESWTR, EPA had no national 

survey data on Cryptosporidium 

occurrence and relied instead on several 

studies that were local or regional. After 

promulgating the IESWTR, EPA 

obtained data from two national 

surveys, the Information Collection Rule 

(ICR) and the ICR Supplemental Surveys 

(ICRSS), which were designed to 

provide improved estimates of 

occurrence on a national basis. 

The ICR included monthly sampling 

for Cryptosporidium and other water 

quality parameters from the sources of 

approximately 350 large PWSs over 18 

months. The ICRSS involved twice-permonth Cryptosporidium sampling from 

the sources of a statistically random 

sample of 40 large and 40 medium 

PWSs over 12 months. In addition, the 

ICRSS required the use of an improved 

analytical method for Cryptosporidium 

analysis that had a higher method 

recovery (the likelihood that an oocyst 

present in the sample will be counted) 

and enhanced sample preparation 

procedures. 

EPA analyzed ICR and ICRSS data 

using a statistical model to account for 

factors like method recovery and sample 

volume analyzed. As described in more 

detail in EPA’s Occurrence and 

Exposure Assessment for the 

LT2ESWTR (USEPA 2005b), the ICR 

and ICRSS results demonstrate two 

main differences for filtered PWSs in 

comparison to Cryptosporidium 

occurrence data used for the IESWTR: 

(1) The occurrence of Cryptosporidium in 

many drinking water sources is lower than 

was indicated by the data used in IESWTR. 

For example, median Cryptosporidium levels 

for the ICR and ICRSS data are approximately 

0.05/L, which is nearly 50 times lower than 

the median IESWTR estimates of 2.3 oocysts/ 

L (USEPA 1998a). 

(2) Cryptosporidium occurrence is more 

variable from location to location than was 

shown by the data considered for the 

IESWTR. This finding demonstrates that, 

although median occurrence levels are below 

those estimated for the IESWTR, a subset of 

PWSs contains Cryptosporidium levels that 

are considerably greater than the median. 

These results, therefore, indicate that 

Cryptosporidium levels are relatively 

low in most water sources, but a subset 

of sources with relatively higher 

concentrations may require additional 

treatment. These findings support a risktargeted approach for the LT2ESWTR 

wherein additional Cryptosporidium 

treatment is required only for filtered 

PWSs with the highest source water 

pathogen levels. 

Only the ICR provided data to 

evaluate Cryptosporidium occurrence in 

unfiltered PWS sources. The median 

Cryptosporidium level among unfiltered 

PWS sources was 0.0079 oocysts/L. This 

level is approximately 10 times lower 

than the median level for filtered PWS 

sources. 

When the Cryptosporidium removal 

that filtered PWSs achieve is taken into 

account, these occurrence data suggest 

that unfiltered PWSs typically have 


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higher concentrations of 

Cryptosporidium in their treated water 

than filtered PWSs. EPA has estimated 

that on average, conventional filtration 

plants remove around 99.9 percent (3- 

log) of the Cryptosporidium present in 

the source water. Most unfiltered PWSs, 

however, provide no treatment for 

Cryptosporidium. If an unfiltered PWS 

had a source water Cryptosporidium 

level 10 times lower than a filtered PWS 

and the filtered PWS achieved 3-log 

Cryptosporidium removal, then the 

Cryptosporidium level in the treated 

water of the unfiltered PWS would be 

100 times higher than in the filtered 

PWS. 

These results suggest that to achieve 

public health protection equivalent to 

that provided by filtered PWSs, 

unfiltered PWSs must take additional 

steps. Thus, this finding supports the 

need for Cryptosporidium treatment 

requirements for unfiltered PWSs under 

the LT2ESWTR. 

3. Analytical Methods 

To establish risk-targeted treatment 

requirements, analytical methods must 

be available to estimate the contaminant 

densities in PWS sources. These density 

estimates are used to determine the 

level of treatment that is needed at a 

particular site. 

When EPA developed the IESWTR, 

the best available method for measuring 

Cryptosporidium was the Information 

Collection Rule Protozoan Method (ICR 

Method). The ICR Method provided a 

quantitative measurement of 

Cryptosporidium oocysts, but typically 

undercounted the actual occurrence due 

to low method recovery. For example, in 

a spiking study (studies in which 

known quantities of oocysts are added 

to water samples) conducted during the 

ICR survey, the mean recovery of spiked 

Cryptosporidium oocysts was only 12 

percent (Scheller et al. 2002). EPA 

concluded that the ICR Method was 

adequate for making national 

occurrence estimates in the ICR survey 

but would not suffice for making 

estimates of Cryptosporidium levels at 

specific sites. 

Subsequent to promulgating the 

IESWTR, EPA developed an improved 

Cryptosporidium method, EPA Method 

1622 (and later, 1623), to achieve higher 

recovery rates and lower inter- and 

intra-laboratory variability than 

previous methods. Methods 1622 and 

1623 incorporate improvements in the 

concentration, separation, staining, and 

microscope examination procedures. 

During the ICRSS, which required the 

use of Method 1622 or 1623, a spiking 

study demonstrated a mean 

Cryptosporidium recovery of 43 percent 

(Connell et al. 2000). Thus, mean 

Cryptosporidium recovery with 

Methods 1622 and 1623 was more than 

3.5 times higher compared to the ICR 

Method performance in the earlier 

spiking study. In addition, the relative 

variation in recovery from sample to 

sample was lower with Methods 1622 

and 1623. 

As described in section IV of this 

preamble, EPA has concluded that a 

monitoring program using Methods 

1622 or 1623 can be effective in 

characterizing PWSs source water 

Cryptosporidium levels for purposes of 

determining the need for additional 

treatment requirements. This finding 

supports the feasibility of risk-targeted 

treatment requirements under the 

LT2ESWTR. 

4. Treatment 

To establish risk-targeted 

Cryptosporidium treatment 

requirements, feasible treatment 

processes must be available that allow 

PWSs to inactivate or remove 

Cryptosporidium. PWSs may then 

implement these treatment processes to 

comply with additional treatment 

requirements. 

During development of the IESWTR, 

EPA recognized that chlorine, the most 

commonly used disinfectant, is 

ineffective for inactivating 

Cryptosporidium. Studies suggested that 

other disinfectants like ozone and 

chlorine dioxide could be effective 

against Cryptosporidium. However, EPA 

concluded that data available at that 

time were not sufficient to define how 

any disinfectant could be applied to 

achieve a specific level of 

Cryptosporidium inactivation (USEPA 

1997). This conclusion was due in part 

to methodological inconsistencies and 

shortcomings in the available studies. 

With the completion of major studies 

since promulgation of the IESWTR, EPA 

has acquired the data necessary to 

establish standards for Cryptosporidium 

inactivation by several disinfectants. For 

ozone and chlorine dioxide, EPA 

reviewed new studies by Rennecker et 

al. (1999), Owens et al. (1999, 2000), 

Oppenheimer et al. (2000), Ruffell et al. 

(2000), and Li et al. (2001). Collectively, 

these studies cover a wide range of both 

natural and laboratory water conditions. 

Based on these studies, EPA has 

developed tables that specify the 

product of ozone or chlorine dioxide 

concentration and time of exposure (i.e., 

CT tables) needed to achieve up to 3-log 

Cryptosporidium inactivation. Section 

IV.D of this preamble shows these 

tables. 

Most significantly, many recent 

studies have demonstrated that UV light 

is efficient for inactivating high levels of 

Cryptosporidium. These studies include 

Clancy et al. (1998, 2000, 2002), Bukhari 

et al. (1999), Craik et al. (2000, 2001), 

Landis et al. 2000), Sommer et al. 

(2001), Shin et al. (2001), and 

Oppenheimer et al. (2002). Using results 

from these studies, EPA has defined the 

UV light intensity and exposure time 

required for up to 4-log 

Cryptosporidium inactivation. Section 

IV.D presents these values. EPA has 

determined that UV light is a feasible 

technology for PWSs of all sizes to 

inactivate Cryptosporidium. 

EPA has also developed standards for 

processes that physically remove 

Cryptosporidium contamination. These 

processes include river bank filtration, 

sedimentation basins, bag filters, 

cartridge filters, and membranes. 

Section IV.D presents design and 

operational standards for these 

processes, along with a summary of 

supporting studies. 

The development of these standards 

for Cryptosporidium inactivation and 

removal processes overcomes a 

significant limitation that existed when 

EPA developed the IESWTR. These 

standards will allow PWSs to 

implement cost-effective strategies to 

comply with additional 

Cryptosporidium treatment 

requirements under the LT2ESWTR. 

F. Federal Advisory Committee 

Recommendations 

EPA convened the Stage 2 M–DBP 

Federal Advisory Committee in March 

1999 to evaluate new information and 

develop recommendations for the 

LT2ESWTR and Stage 2 DBPR. The 

Committee was comprised of 

representatives from EPA, State and 

local public health and regulatory 

agencies, local elected officials, Indian 

Tribes, drinking water suppliers, 

chemical and equipment manufacturers, 

and public interest groups. A technical 

workgroup provided analytical support 

for the Committee’s discussions. 

Committee members signed an 

Agreement in Principle in September 

2000 stating consensus 

recommendations of the group. The 

Agreement was published in a 

December 29, 2000 Federal Register 

notice (USEPA 2000a). For the 

LT2ESWTR, the consensus 

recommendations of the Committee are 

summarized as follows: 

(1) Supplemental risk-targeted 

Cryptosporidium treatment by filtered 

PWSs with higher source water 

contaminant levels as shown by 

monitoring results; 

(2) Cryptosporidium inactivation by 

all unfiltered PWSs, which must meet 


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overall treatment requirements using a 

minimum of 2 disinfectants; 

(3) A ‘‘toolbox’’ of treatment and 

control processes for PWSs to comply 

with Cryptosporidium treatment 

requirements; 

(4) Reduced monitoring burden for 

small filtered PWSs; 

(5) Future monitoring to confirm or 

revise source water quality assessments; 

(6) Development of guidance for UV 

disinfection and other toolbox 

components; and 

(7) Cover or treat existing uncovered 

finished water reservoirs (i.e., storage 

facilities) or implement risk mitigation 

plans. 

These recommendations reflect a 

Committee judgement that, based on 

available information, additional riskbased Cryptosporidium treatment 

requirements for filtered and unfiltered 

PWSs are appropriate and feasible 

under the LT2ESWTR. Much of today’s 

final LT2ESWTR reflects the 

Committee’s recommendations. The 

next part of this preamble describes 

specific requirements of the rule. 

IV. Explanation of Today’s Action 

A. Source Water Monitoring 

Requirements 

Today’s rule requires PWSs using 

surface water or GWUDI sources to 

monitor their source water to assess the 

level of Cryptosporidium. Monitoring 

results assign a PWS to a 

Cryptosporidium treatment bin, which 

determines the extent of additional 

Cryptosporidium treatment 

requirements (sections IV.B and IV.C 

described treatment requirements for 

filtered and unfiltered PWSs, 

respectively). 

Source water monitoring under the 

LT2ESWTR is designed to ascertain the 

mean level of Cryptosporidium in the 

influent to a surface water treatment 

plant. Requirements differ by PWS size 

(above or below 10,000 people served) 

and treatment plant type (filtered or 

unfiltered PWS). This section describes 

monitoring requirements for sampling 

parameters and frequency, sampling 

location, sampling schedule, monitoring 

plants that operate only part of the year, 

failing to monitor, providing treatment 

instead of monitoring, grandfathering 

previously collected data, ongoing 

watershed assessment, second round of 

monitoring, and new source monitoring. 

Other sections of this preamble 

describe additional requirements related 

to monitoring, including compliance 

schedules (section IV.G), reporting of 

monitoring results (section IV.I), use of 

approved analytical methods, including 

minimum sample volume (section IV.J), 

and use of approved laboratories 

(section IV.K). As described in section 

IV.G, monitoring compliance dates 

under the LT2ESWTR are staggered: 

smaller PWSs begin monitoring after 

larger PWSs. 

For additional information, see 

Source Water Monitoring Guidance 

Manual for Public Water Systems under 

the Long Term 2 Enhanced Surface 

Water Treatment Rule. This document 

provides guidance on sampling location, 

procedures for collecting and shipping 

samples, contracting with laboratories, 

and related topics to assist PWSs in 

complying with LT2ESWTR monitoring 

requirements. It may be acquired from 

EPA’s Safe Drinking Water Hotline, 

which can be contacted as described 

under FOR FURTHER INFORMATION

CONTACT at the beginning of this 

document. 

1. Today’s Rule 

a. Sampling parameters and 

frequency. Requirements for the source 

water parameters that PWSs must 

measure under the LT2ESWTR, as well 

as the sampling frequency and duration, 

are stated as follows for large and small 

PWSs, including both filtered and 

unfiltered plants: 

Large Filtered PWSs 

Filtered PWSs serving at least 10,000 

people must sample at least monthly for 

Cryptosporidium, E. coli, and turbidity 

for a period of two years. Sampling may 

be conducted at a higher frequency (e.g., 

twice-per-month, once-per-week) but 

the sampling must be evenly spaced 

throughout the monitoring period. As 

described in section IV.B, filtered PWSs 

that sample at least twice-per-month 

over two years use a different 

calculation, which is less conservative, 

to determine their treatment bin 

classification under the LT2ESWTR. 

Large Unfiltered PWSs 

Unfiltered PWSs serving at least 

10,000 people must also sample for 

Cryptosporidium at least monthly for a 

period of 2 years. No E. coli or turbidity 

monitoring is required for unfiltered 

PWSs. Unfiltered PWSs may choose to 

sample more frequently; however, as 

described in section IV.C, a higher 

sampling frequency does not change the 

calculation used to determine unfiltered 

PWS Cryptosporidium treatment 

requirements. 

Small Filtered PWSs 

Filtered PWSs serving fewer than 

10,000 people (i.e., small PWSs) 

monitor under the LT2ESWTR using a 

two-phase strategy that begins with an 

indicator screening analysis. Small 

filtered PWSs must initially sample for 

E. coli at least once every two weeks for 

a period of one year. Cryptosporidium 

monitoring is required of these PWSs 

only if the indicator monitoring results 

meet one of the following conditions: 

(1) For PWSs using lake/reservoir 

sources, the annual mean E. coli 

concentration is greater than 10 E. coli/ 

100 mL. 

(2) For PWSs using flowing stream 

sources, the annual mean E. coli 

concentration is greater than 50 E. coli/ 

100 mL. 

PWSs using ground water under the 

direct influence of surface water must 

comply with the requirement to monitor 

for Cryptosporidium based on the E. coli 

level that applies to the nearest surface 

water body. If no surface water body is 

nearby, the PWS must comply based on 

the requirements that apply to PWSs 

using lake/reservoir sources. 

The State may approve small filtered 

PWSs to monitor for an indicator other 

than E. coli. The State also may approve 

an alternative E. coli concentration to 

trigger Cryptosporidium monitoring. 

This approval must be in writing and 

must be based on a State determination 

that the alternative indicator and/or 

trigger level will more accurately 

identify whether a PWS will exceed the 

Bin 1 Cryptosporidium level of 0.075 

oocysts/L, as stated in section IV.B.1 of 

this preamble. EPA will issue guidance 

to States on alternative indicators and 

trigger levels, if warranted, based on 

large PWS monitoring results. 

Small filtered PWSs may elect to skip 

E. coli monitoring if they notify the 

State that they will monitor for 

Cryptosporidium. PWSs must notify the 

State no later than three months prior to 

the date the PWS is required to begin 

monitoring (see section IV.G for specific 

dates). 

Small filtered PWSs that are required 

to monitor for Cryptosporidium must 

conduct this monitoring using either of 

two frequencies: (1) Sample at least 

twice-per-month for a period of one year 

or (2) sample at least once-per-month for 

a period of two years. Note that the 

same treatment compliance dates apply 

to the PWS regardless of which 

Cryptosporidium sampling frequency is 

used (i.e., selecting the two-year 

Cryptosporidium sampling frequency 

does not extend Cryptosporidium 

treatment compliance deadlines). 

Small Unfiltered PWSs 

All unfiltered PWSs serving fewer 

than 10,000 people must monitor for 

Cryptosporidium. The E. coli screening 

analysis used by small filtered PWSs is 

not applicable to small unfiltered PWSs. 

Small unfiltered PWSs must use either 


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of the same two Cryptosporidium 

sampling frequencies available to small 

filtered PWSs: (1) Sample twice-permonth for one year or (2) sample onceper-month for two years. As with small 

filtered PWSs, the same treatment 

compliance dates apply to the PWS 

regardless of which Cryptosporidium 

sampling frequency is used. 

b. Sampling location. PWSs must 

collect source water samples for each 

plant that treats a surface water or 

GWUDI source. However, where 

multiple plants receive all of their water 

from the same influent, such as plants 

that draw water from the same intake or 

pipe, the State may approve one set of 

monitoring results to be applied to all 

plants. 

PWSs must collect source water 

samples prior to chemical treatment, 

such as coagulants, oxidants, and 

disinfectants, unless the following 

condition is met: The State may approve 

a system to collect a sample after 

chemical treatment if the State 

determines that collecting a sample 

prior to chemical treatment is not 

feasible and that the chemical treatment 

is unlikely to have a significant adverse 

effect on the analysis of the sample. 

PWSs that recycle filter backwash must 

collect samples prior to the point of 

filter backwash addition due to the 

likely presence of coagulant and other 

treatment chemicals in the backwash. 

See section IV.D.6 for directions on 

sampling location for PWSs using bank 

filtration. 

For plants that use multiple water 

sources at the same time, PWSs must 

collect samples from a tap where the 

sources are combined prior to treatment, 

if available. If a blended source tap is 

not available, PWSs must collect 

samples from each source and either 

analyze a weighted composite (blended) 

sample or analyze samples from each 

source separately and determine a 

weighted average of the results. The 

weighting of sources must reflect the 

relative usage of the different sources by 

the treatment plant at the time the 

sample is collected. 

PWSs must submit a description of 

their proposed sampling location(s) to 

the State no later than three months 

prior to the date the PWS must begin 

monitoring (see section IV.G for specific 

dates). This description must address 

the position of the sampling location in 

relation to the PWS’s water source(s) 

and treatment processes, including 

points of chemical addition and filter 

backwash recycle. If the State does not 

respond to a PWS regarding sampling 

location(s), the PWS must begin 

sampling at the reported location. See 

Source Water Monitoring Guidance 

Manual for Public Water Systems under 

the Long Term 2 Enhanced Surface 

Water Treatment Rule, which can be 

acquired as stated previously, for 

guidance on sampling location 

descriptions. 

c. Sampling schedule. PWSs must 

collect samples in accordance with a 

schedule that the PWS develops and 

reports prior to initiating monitoring. 

The sampling schedule must specify the 

calendar dates when the PWS will 

collect each required sample in a 

particular round of monitoring. 

Scheduled sampling dates must be 

evenly distributed throughout the 

monitoring period, but may be arranged 

to accommodate holidays, weekends, 

and other events when collecting or 

analyzing a sample would be 

problematic (e.g., a PWS is not required 

to schedule samples on the same 

calendar date each month). 

PWSs must submit sampling 

schedules no later than three months 

prior to the date the PWS must begin a 

round of monitoring (see section IV.G 

for specific dates). Unless the State 

approves an alternative procedure, large 

PWSs (serving at least 10,000 people) 

must report their sampling schedule for 

initial source water monitoring to EPA 

using the LT2ESWTR electronic data 

reporting and review system described 

in section IV.I. Schedules for initial 

monitoring by small PWSs and for the 

second round of monitoring by all PWSs 

must be reported to the State. PWSs 

should verify that their laboratory can 

accommodate the scheduled sampling 

dates before submitting the schedule. 

EPA will not formally approve 

sampling schedules but will notify a 

PWS if its sampling schedules does not 

meet the requirements of today’s rule 

(e.g., does not include the required 

number of samples). If a PWS does not 

receive notification from the State or 

EPA regarding the sampling schedule, 

the PWS must begin monitoring 

according to the reported sampling 

schedule. 

PWSs must collect samples within 

two days before or two days after the 

dates indicated in their sampling 

schedules (i.e., within a 5-day period 

around the schedule date) unless one of 

the following two conditions applies: 

(1) If an extreme condition or 

situation exists that may pose danger to 

the sample collector, or that cannot be 

avoided and causes the PWS to be 

unable to sample in the scheduled 5-day 

period, the PWS must sample as close 

to the scheduled date as is feasible 

unless the State approves an alternative 

sampling date. The PWS must submit an 

explanation for the delayed sampling 

date to the State concurrent with the 

shipment of the samples to the 

laboratory. 

(2) If a PWS is unable to report a valid 

analytical result for a scheduled 

sampling date due to equipment failure, 

loss of or damage to the sample, failure 

to comply with the analytical method 

requirements, or the failure of an 

approved laboratory to analyze the 

sample, then the PWS must collect a 

replacement sample. Collection of the 

replacement sample must occur within 

21 days of the PWS receiving 

information that an analytical result 

cannot be reported for the scheduled 

date unless the PWS demonstrates that 

collecting a replacement sample within 

this time frame is not feasible or the 

State approves an alternative resampling 

date. The PWS must submit an 

explanation for the resampling date to 

the State concurrent with the shipment 

of the sample to the laboratory. 

Failure to collect a required sample 

within the 5-day period around a 

scheduled date that does not meet one 

of these two conditions is a monitoring 

violation. PWSs must revise their 

sampling schedules to add dates for 

collecting all missed samples and must 

submit the revised schedule to the State 

for approval prior to when the PWS 

begins collecting the missed samples. 

d. Plants operating only part of the 

year. Some PWSs operate surface water 

treatment plants for only part of the 

year. This includes PWSs that provide 

water for only a fraction of the year (e.g., 

resorts open only in the summer) and 

PWSs that use a surface water plant to 

supplement another source only during 

periods of high demand. 

Most LT2ESWTR monitoring, 

treatment, and implementation schedule 

requirements apply to such plants. 

Monitoring requirements, however, 

differ in two respects: 

(1) PWSs must conduct sampling only 

during months of the 2 year monitoring 

period when the plant operates unless 

the State specifies another monitoring 

period based on plant operating 

practices; and 

(2) For plants that operate less than 

six months per year and where 

Cryptosporidium monitoring is 

required, PWSs must collect at least six 

Cryptosporidium samples per year 

during each of two years of monitoring. 

e. Failing to monitor. Today’s rule 

requires PWSs to provide a Tier 3 public 

notice for violation of monitoring and 

testing procedure requirements, 

including the failure to collect one or 

two source water Cryptosporidium 

samples. If a PWS fails to collect three 

or more Cryptosporidium samples, other 

than in specifically exempted situations 

(see section IV.A.1.c), the PWS must 


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provide a Tier 2 special public notice. 

Violations for failing to monitor persist 

until the State determines that the PWS 

has begun sampling on a revised 

schedule that includes dates for the 

collection of missed samples. Section 

IV.H provides further details on public 

notice requirements of the LT2ESWTR. 

PWSs must report their bin 

classification (or mean Cryptosporidium 

level for unfiltered PWSs) no later than 

six months after the end of the 

scheduled monitoring period (specific 

dates in section IV.G). Failure by a PWS 

to collect the required number of 

Cryptosporidium samples to report its 

bin classification or mean 

Cryptosporidium level by the 

compliance date is a treatment 

technique violation and the PWS must 

provide a Tier 2 special public notice 

(unless the PWS has already provided a 

Tier 2 public notice for missing three 

sampling dates and is successfully 

meeting a State-approved schedule for 

sampling). The treatment technique 

violation and public notice 

requirements persist until the State 

determines that the PWS is 

implementing a State-approved 

monitoring plan to allow bin 

classification or will install the highest 

level of treatment required under the 

rule, as described next. 

f. Providing treatment instead of 

monitoring. PWSs are not required to 

conduct source water monitoring under 

the LT2ESWTR for plants that will 

provide the highest level of treatment 

required under the rule. This applies 

both to plants that provide this level of 

treatment at the time the plant would 

otherwise begin source water 

monitoring and to plants that commit to 

install technology to achieve this level 

of treatment by the applicable 

compliance date for meeting 

Cryptosporidium treatment 

requirements under the LT2ESWTR. 

Filtered PWSs are not required to 

monitor at plants that will provide a 

total of at least 5.5-log of treatment for 

Cryptosporidium, equivalent to meeting 

the treatment requirements of Bin 4 as 

discussed in section IV.B. Unfiltered 

PWSs are not required to monitor for 

plants that will provide a total of at least 

3-log of Cryptosporidium inactivation, 

equivalent to meeting the treatment 

requirements for unfiltered PWSs with 

source water Cryptosporidium levels 

above 0.01 oocysts/L as discussed in 

section IV.C. 

PWSs that intend to provide this level 

of treatment rather than initiate 

monitoring must notify the State no 

later than three months prior to the 

month the PWS must otherwise begin 

monitoring. PWSs submit this 

notification in lieu of submitting a 

sampling schedule. In addition, a PWS 

may choose to stop sampling at any 

point after it has initiated monitoring if 

it notifies the State that it will provide 

the highest level of treatment. In both 

cases, the PWSs must install and 

operate technologies to achieve this 

level of treatment no later than the 

applicable Cryptosporidium treatment 

compliance date for the PWS as 

specified in section IV.G. Failure to 

provide this treatment by the 

compliance date is a treatment 

technique violation. 

g. Grandfathering previously collected 

data. If the State approves, PWSs may 

comply with the initial source water 

monitoring requirements of today’s rule 

by using (i.e., grandfathering) sample 

results collected before the PWS is 

required to begin monitoring. PWSs may 

grandfather monitoring results either in 

lieu of or in addition to conducting new 

monitoring under the rule. To be 

eligible for grandfathering, monitoring 

results must be equivalent in data 

quality to monitoring PWSs conduct 

under today’s rule and the PWS must 

comply with reporting requirements. 

Details of these requirements follow. 

Grandfathered Data Quality 

Requirements 

• Analysis of E. coli samples must 

meet the analytical method and 

approved laboratory requirements for 

source water monitoring under today’s 

rule. PWSs are not required to report E. 

coli and turbidity data in order to 

grandfather Cryptosporidium 

monitoring results, although EPA 

requests that PWSs report these data if 

they are available. PWSs that 

grandfather Cryptosporidium data 

without associated E. coli and turbidity 

data are not required to conduct 

separate monitoring for these 

parameters when they have satisfied 

Cryptosporidium monitoring 

requirements. 

• Analysis of Cryptosporidium 

samples must meet the criteria of a 

validated version of EPA Method 1622 

or 1623, which are described in USEPA 

1999a, USEPA 1999b, USEPA 2001e, 

USEPA 2001f, USEPA 2005c, and 

USEPA 2005d. The volume analyzed for 

each sample must meet the criteria 

described in section IV.J, which are at 

least 10 L of sample or at least 2 mL of 

packet pellet volume or as much volume 

as two approved filters can 

accommodate before clogging. 

• The sampling location must meet 

the criteria for LT2ESWTR monitoring, 

as described previously. 

• For Cryptosporidium samples, the 

sampling frequency must be at least 

monthly and on a regular schedule. The 

collection of individual samples may 

deviate from a regular schedule under 

the same criteria that apply to deviation 

from LT2ESWTR sampling schedules, as 

described previously. Additionally, 

deviations in the sampling frequency of 

previously collected data are allowed 

under the following conditions: (1) 

PWSs may grandfather data where there 

are gaps in the sampling frequency if the 

State approves and if the PWS conducts 

additional monitoring when specified 

by the State to ensure the data used for 

bin classification are seasonally 

representative and unbiased; and (2) 

PWSs may grandfather data where the 

sampling frequency varies (e.g., one year 

of sampling monthly and one year of 

sampling twice-per-month); monthly 

average sample concentrations must be 

used to calculate the bin classification, 

as described in section IV.B. 

Grandfathered Data Reporting 

Requirements 

PWSs that request to grandfather 

previously collected monitoring results 

must report the following information 

by the applicable dates listed in this 

section. PWSs serving at least 10,000 

people must report this information to 

EPA unless the State approves an 

alternate procedure for reporting. PWSs 

serving fewer than 10,000 people must 

report this information to the State. 

PWSs must report that they intend to 

submit previously collected monitoring 

results for grandfathering. This report 

must specify the number of previously 

collected results the PWS will submit, 

the dates of the first and last sample, 

and whether a PWS will conduct 

additional source water monitoring for 

initial bin classification. PWSs must 

report this information no later than 

three months prior to the date the PWSs 

is required to start monitoring, as shown 

in section IV.G. 

PWSs must report previously 

collected monitoring results for 

grandfathering, along with the required 

documentation listed in this section, no 

later than two months after the month 

the PWS is required to start monitoring, 

as shown in section IV.G. 

• For each sample Cryptosporidium 

or E. coli result, PWSs must report the 

applicable data elements in section 

IV.I.1. 

• PWSs must certify to EPA or the 

State that the reported monitoring 

results include all results the PWS 

generated during the time period 

beginning with the first reported result 

and ending with the final reported 

result. This applies to samples that were 

collected from the sampling location 

specified for source water monitoring 


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under this subpart, not spiked, and 

analyzed using the laboratory’s routine 

process for the analytical methods listed 

in this section. 

• PWSs must certify to EPA or the 

State that the samples were 

representative of a plant’s source 

water(s) and the source water(s) have 

not changed. PWSs must submit to EPA 

a description of the sampling location(s) 

for each water treatment plant, which 

must address the position of the 

sampling location in relation to the 

PWS’s water source(s) and treatment 

processes, including points of chemical 

addition and filter backwash recycle. 

• For Cryptosporidium samples, the 

laboratory or laboratories that analyzed 

the samples must provide a letter 

certifying that the quality control 

criteria specified in the methods listed 

in this section were met for each sample 

batch associated with the reported 

results. Alternatively, the laboratory 

may provide bench sheets and sample 

examination report forms for each field, 

matrix spike, initial precision and 

recovery (IPR), ongoing precision and 

recovery (OPR), and method blank 

sample associated with the reported 

results. 

• If the State determines that a 

previously collected data set submitted 

for grandfathering was generated during 

source water conditions that were not 

normal for the PWS, such as a drought, 

the State may disapprove the data. 

Alternatively, the State may approve the 

previously collected data if the PWS 

reports additional source water 

monitoring data, as determined by the 

State, to ensure that the overall data set 

used for bin classification represents 

average source water conditions for the 

PWS. 

If a PWS submits previously collected 

data that fully meet the number of 

samples required for initial source water 

monitoring and some of the data are 

rejected due to not meeting the 

requirements of this section, PWSs must 

conduct additional monitoring to 

replace rejected data on a schedule the 

State approves. PWSs are not required 

to begin this additional monitoring until 

at least two months after notification 

that data have been rejected and 

additional monitoring is necessary. 

h. Ongoing watershed assessment. 

Today’s rule includes provisions to 

assess changes in a PWS’s source water 

quality following initial bin 

classification. As required by 40 CFR 

142.16(b)(3)(i), source water is one of 

the components that States must 

address during the sanitary surveys that 

are required for surface water PWSs. 

These sanitary surveys must be 

conducted every 3 years for community 

PWSs and every 5 years for noncommunity PWSs. Under today’s rule, if 

the State determines during the sanitary 

survey or an equivalent source water 

assessment that significant changes have 

occurred in the watershed that could 

lead to increased contamination of the 

source water by Cryptosporidium, the 

PWS must take actions specified by the 

State to address the contamination. 

These actions may include additional 

source water monitoring and/or 

implementing options from the 

microbial toolbox discussed in section 

IV.D. 

i. Second round of monitoring. PWSs 

must begin a second round of source 

water monitoring beginning six years 

after initial bin classification (see 

compliance dates in section IV.G). If 

EPA does not modify LT2ESWTR 

requirements by issuing a new 

regulation prior to the second round of 

monitoring, PWSs must carry out this 

monitoring according to the 

requirements that apply to the initial 

round of source water monitoring. PWSs 

will then be reclassified in LT2ESWTR 

treatment bins based on the secondround monitoring result. However, if 

EPA changes the LT2ESWTR treatment 

bin structure to reflect a new analytical 

method or new risk information, PWSs 

will undergo a risk characterization in 

accordance with the revised rule. 

j. New source monitoring. A PWS that 

begins using a new surface water source 

after the date the PWS is required to 

conduct source water monitoring under 

the LT2ESWTR must monitor the new 

source on a schedule approved by the 

State. This applies to both new plants 

that begin operation and previously 

operating plants that bring a new source 

on-line after the required monitoring 

date for the PWS. The State may 

determine that monitoring should be 

conducted before a new plant or source 

is brought on-line or initiated within 

some time period afterward. The new 

source monitoring must meet all 

LT2ESWTR requirements as specified 

previously in this section. The PWS 

must also determine its treatment bin 

classification and comply with any 

additional Cryptosporidium treatment 

requirements based on the monitoring 

results on a schedule approved by the 

State. 

2. Background and Analysis 

Monitoring requirements in today’s 

rule are designed to ascertain 

Cryptosporidium levels with suitable 

accuracy for making treatment bin 

classifications and in a time frame that 

does not delay the installation of 

Cryptosporidium treatment where 

needed. The following discussion 

summarizes the basis for monitoring 

requirements with respect to sampling 

parameters and frequency, sampling 

location, sampling schedule, monitoring 

plants that operate for only part of the 

year, failing to monitor, grandfathering 

previously collected data, ongoing 

watershed assessment, and the second 

round of monitoring. Most of these 

requirements were part of the August 

11, 2003, proposal for today’s final rule, 

and supporting analyses are presented 

in greater detail in the proposal (USEPA 

2003a). Differences from proposed 

requirements are noted in the following 

discussion where applicable. 

a. Sampling parameters and 

frequency. The requirements in today’s 

final rule for the parameters and 

frequency of source water monitoring 

are unchanged from those in the 

proposed rule (USEPA 2003a), with the 

exception of an additional option for 

lower frequency Cryptosporidium 

sampling by small PWSs. These 

requirements reflect recommendations 

by the Stage 2 M-DBP Advisory 

Committee. They are designed to ensure 

a low potential for misclassification in 

assigning PWSs to Cryptosporidium 

treatment bins. The supporting analyses 

are summarized as follows for 

Cryptosporidium and indicator (E. coli) 

monitoring: 

Cryptosporidium Monitoring 

EPA analyzed bin misclassification 

rates for different Cryptosporidium 

monitoring programs by evaluating the 

likelihood of two types of errors: 

(1) A PWS with a true mean 

Cryptosporidium concentration of 0.5- 

log (i.e., factor of 3.2) above a bin 

boundary is incorrectly assigned to a 

lower bin (false negative) and 

(2) A PWS with a true mean 

concentration of 0.5-log below a bin 

boundary is incorrectly assigned to a 

higher bin (false positive). 

The first type of error, a false negative, 

could lead to PWSs not providing an 

adequate level of treatment while the 

second type of error, a false positive, 

could lead to PWSs incurring additional 

costs for unnecessary treatment. 

EPA evaluated false positive and false 

negative rates for monitoring programs 

that differed based on the number of 

samples collected and the calculation 

used to determine the bin classification. 

The analysis accounted for the sample 

volume assayed, variation in source 

water Cryptosporidium occurrence, 

variation in analytical method recovery, 

and other factors. 

Results of this analysis indicate that 

PWSs must collect at least 24 samples 

in order to keep the likelihood of both 

false positives and false negatives at five 


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percent or less. Under a monitoring 

program involving fewer samples, such 

as eight or twelve, a very conservative 

calculation for bin classification would 

be required to achieve a low false 

negative rate (e.g., bin classification 

based on the maximum or second 

highest sample concentration). 

However, such an approach would 

result in false positive rates in the range 

of 50 to 70 percent. Conversely, 

collecting more than 24 samples can 

further reduce false positive and false 

negative rates, albeit to a small degree. 

See the proposed LT2ESWTR for 

additional details on this analysis 

(USEPA 2003a). 

Based on the results of this analysis, 

EPA concluded that PWSs operating 

year-round should collect at least 24 

samples when they monitor for 

Cryptosporidium. This number of 

samples ensures a high likelihood of 

appropriate bin classification. Today’s 

rule does not allow bin classification 

based on fewer samples (except in the 

case of PWSs operating only part of the 

year) as this would involve 

unacceptably high false positive or false 

negative rates and would, therefore, be 

an inappropriate basis to determine 

Cryptosporidium treatment 

requirements. EPA believes, though, 

that PWSs should have the choice to 

collect more than 24 samples to further 

improve the accuracy of bin 

classification, and today’s rule allows 

this. 

In regard to the time frame for 

LT2ESWTR monitoring, the Agency 

considered the trade-off between 

monitoring over a long period to better 

capture temporal fluctuations and the 

desire to prescribe additional treatment 

quickly to PWSs with higher 

Cryptosporidium levels. Today’s rule 

requires large PWSs to evaluate their 

source water Cryptosporidium levels 

using two years of monitoring. This will 

account for some degree of yearly 

variability, without significantly 

delaying additional public health 

protection where needed. 

Because many small PWSs will 

monitor for E. coli for one year before 

monitoring for Cryptosporidium, today’s 

rule allows two options. Small PWSs 

can collect 24 Cryptosporidium samples 

over just one year (resulting in a total of 

two years of source water monitoring 

when E. coli monitoring is considered) 

or they can spread their 24 

Cryptosporidium samples over two 

years. Spreading the Cryptosporidium 

monitoring over two years will reduce 

the monitoring costs a PWS incurs in a 

single year but will not push back the 

treatment compliance deadline. This 

allowance for small PWSs to monitor for 

Cryptosporidium over two years is a 

change from the proposal (USEPA 

2003a). It stems from recognition of the 

benefit this approach will provide to 

some small PWSs in budgeting for 

monitoring. 

Indicator Monitoring 

Due to the relatively high cost of 

analyzing samples for Cryptosporidium, 

the Advisory Committee and EPA 

investigated indicators that are less 

costly to analyze to determine if any 

could be used in place of 

Cryptosporidium monitoring. No 

indicators were identified that 

correlated strongly with 

Cryptosporidium and could fully 

substitute for Cryptosporidium 

monitoring for determining treatment 

bin classifications. However, this 

investigation did identify an indicator, 

E. coli, that can be used to identify some 

of the water sources that are unlikely to 

exceed a Cryptosporidium level of 0.075 

oocysts/L—the level at which filtered 

PWSs must provide additional 

treatment under the LT2ESWTR. 

Data from the ICR and ICRSS were 

used in the investigation of indicators. 

With these data, E. coli performed the 

best in identifying sources with low 

Cryptosporidium levels. In addition, 

analyzing plants separately based on 

source water type was necessary due to 

a different relationship between E. coli 

and Cryptosporidium in reservoir/lake 

sources compared to flowing stream 

sources. 

The analysis of E. coli concentrations 

that could trigger Cryptosporidium 

monitoring was based on false negative 

and false positive rates. For this 

indicator, false negatives occur when 

sources do not exceed the E. coli trigger 

value but exceed a Cryptosporidium 

level of 0.075 oocysts/L. False positives 

occur when sources exceed the E. coli 

trigger value but do not exceed a 

Cryptosporidium level of 0.075 oocysts/ 

L. The false negative rate is critical 

because it characterizes the ability of the 

indicator to identify those plants with 

higher Cryptosporidium levels that 

should conduct Cryptosporidium 

monitoring to determine if additional 

treatment is needed. 

For plants with flowing stream 

sources, a mean E. coli trigger 

concentration of 50/100 mL produced 

zero false negatives for both ICR and 

ICRSS data sets. This means that in 

these data sets, all plants that exceeded 

mean Cryptosporidium concentrations 

of 0.075 oocysts/L also exceeded the E. 

coli trigger concentration. The false 

positive rate for this trigger 

concentration was near 50 percent, 

meaning it was not highly specific in 

targeting only those plants with high 

Cryptosporidium levels. However, at a 

higher E. coli trigger concentration, such 

as 100/100 mL, the false negative rate 

increased without a significant 

reduction in the false positive rate. 

For plants with lake or reservoir 

sources, a mean E. coli trigger of 10/100 

mL resulted in a false negative rate of 20 

percent with ICR data and 67 percent 

with ICRSS data. While this false 

negative rate in the ICRSS data set 

appears high, it is based on just three 

plants in this survey that used a 

reservoir/lake source and had a mean 

Cryptosporidium level above 0.075 

oocysts/L. With a lower E. coli trigger 

concentration, such as 5/100 mL, the 

number of false negatives in both data 

sets decreased by one plant, but the 

false positive rate increased from 20 to 

40 percent. 

After evaluating these results, the 

Advisory Committee recommended that 

all large PWSs monitor for 

Cryptosporidium, rather than using E. 

coli in a screening analysis. EPA 

concurred with this recommendation 

because it achieves the highest certainty 

that these PWSs will be classified in the 

correct Cryptosporidium treatment bin 

and provide the appropriate level of 

public health protection. In addition, 

the Advisory Committee recommended 

and today’s rule requires that large 

filtered PWSs collect E. coli and 

turbidity samples along with 

Cryptosporidium. EPA will use these 

data to confirm or, if necessary, further 

refine the use of E. coli and possibly 

turbidity as indicators for monitoring by 

small filtered PWSs. 

Cryptosporidium monitoring places a 

relatively greater economic burden on 

small PWSs, and EPA will have 

additional E. coli and Cryptosporidium 

data from large PWS monitoring prior to 

the initiation of small PWS monitoring. 

Based on these considerations and the 

available data on E. coli as an indicator 

of sources with lower Cryptosporidium 

levels, the Advisory Committee 

recommended that small filtered PWSs 

initially monitor for E. coli for one year 

as a screening analysis. Biweekly 

sampling (i.e., 1 sample every two 

weeks) for E. coli is required to achieve 

high confidence in the results, since no 

additional monitoring is required if the 

E. coli level is less than the trigger 

value. Mean E. coli concentrations 

above 10 and 50/100 mL trigger 

Cryptosporidium monitoring in PWSs 

using reservoir/lake and flowing stream 

sources, respectively. 

EPA concurred with these 

recommendations by the Advisory 

Committee and believes they achieve an 

appropriate balance between enhancing 


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public health protection and reducing 

the economic impact of today’s rule on 

small PWSs. Survey data indicate that 

approximately 75 to 80 percent of small 

PWSs will not exceed the E. coli trigger 

values and, consequently, will not be 

required to monitor for 

Cryptosporidium. Because E. coli is far 

less costly to analyze than 

Cryptosporidium (costs listed in USEPA 

2005a), this approach will significantly 

reduce the burden of today’s rule for 

these PWSs. Further, EPA will review 

indicator data from large PWS 

monitoring and, if appropriate, issue 

guidance to States on alternative 

indicator triggers prior to when small 

PWSs begin monitoring. Today’s rule 

allows States to approve alternative 

approaches to indicator monitoring for 

small PWSs. 

EPA could not identify an indicator 

screening analysis for unfiltered PWSs. 

As described in section IV.C, a mean 

Cryptosporidium concentration of 0.01 

oocysts/L determines whether unfiltered 

PWSs are required to provide 2- or 3-log 

Cryptosporidium inactivation. No E. 

coli concentration was effective in 

determining whether PWSs were likely 

to fall above or below this level. 

Consequently, today’s rule requires all 

unfiltered PWSs to monitor for 

Cryptosporidium, unless they choose to 

provide 3-log Cryptosporidium 

inactivation. 

b. Sampling location. The 

requirements in today’s final rule for the 

source water sample collection location 

are similar to those in the proposed rule 

(USEPA 2003a). They are designed to 

achieve two objectives: (1) Characterize 

the influent water to the treatment plant 

at the time each sample is collected and 

(2) ensure that samples are not affected 

by treatment chemicals that could 

interfere with Cryptosporidium 

analysis. 

The first objective is the basis for 

requiring PWSs that use multiple 

sources to either analyze a blended 

source sample or calculate a weighted 

average of sources that reflects the 

influent at the time of sample collection. 

It is also the reason that PWSs are 

required to sample after certain 

pretreatment processes like bank 

filtration (described in section IV.D) that 

do not involve chemical addition. 

The second objective is why PWSs are 

generally required to sample upstream 

of chemical addition and prior to 

backwash addition (for PWSs that 

recycle filter backwash). However, EPA 

recognizes that in some situations, 

sampling prior to chemical addition will 

not be feasible and discontinuing 

chemical addition for a period of time 

prior to sampling will not be advisable. 

This situation could occur when a 

treatment chemical is added at an intake 

that is difficult to access. Further, some 

treatment chemicals may not interfere 

with Cryptosporidium analyses when 

present at very low levels. 

Consequently, today’s rule allows States 

to approve PWSs sampling after 

chemical addition when the State 

determines that collection prior to 

chemical treatment is not feasible and 

the treatment chemical is not expected 

to interfere with the analysis of the 

sample. 

EPA believes that States should 

review source water monitoring 

locations for their PWSs. State review of 

monitoring locations will ensure that 

PWSs collect source water samples at 

the correct location to determine the 

appropriate level of public health 

protection. Consequently, today’s rule 

requires PWSs to report a description of 

their monitoring location to the State. 

This requirement is a change from the 

proposed rule, which did not require 

PWSs to report a description of their 

sampling location (USEPA 2003a). This 

change reflects public comment on the 

proposal, as described later, which 

strongly supported State review of 

monitoring locations. If a PWS does not 

hear back from the State by the time it 

is scheduled to begin sampling, it may 

assume that its monitoring location is 

acceptable. 

c. Sampling schedule. The 

requirement in today’s final rule that 

PWSs must develop a schedule for 

sample collection before the start of 

monitoring was part of the proposal 

(USEPA 2003a). This requirement will 

help to ensure that monitoring 

determines the mean concentration of 

Cryptosporidium in the treatment plant 

influent. To achieve this objective, the 

timing of sample collection must not be 

adjusted in response to fluctuations in 

water quality—for example, the 

avoidance of sampling when the 

influent water is expected to be of poor 

quality. 

EPA believes that the 5-day window 

for sample collection and associated 

allowances for sampling outside this 

window provide sufficient flexibility. If 

circumstances arise that prevent the 

PWS from sampling within the 

scheduled 5-day window, such as a 

weather event or plant emergency, the 

PWS must collect a sample as soon as 

feasible. In this case, feasibility includes 

both the ability of the PWS to safely 

collect a sample and the availability of 

an approved laboratory to conduct the 

analysis within method specifications. 

In addition, today’s rule allows States to 

authorize a different date for collecting 

the delayed sample. Such an 

authorization may be appropriate in 

cases where sampling is significantly 

delayed and collecting the delayed 

sample during the same time period in 

the following year of monitoring is 

preferable. 

PWSs that collect a sample as 

scheduled but are unable to have the 

sample analyzed as required due to 

problems like shipping or laboratory 

analysis must collect a replacement 

sample within 21 days of receiving 

information that one is needed, unless 

the PWS demonstrates that collecting a 

replacement sample within this time 

frame is not feasible. This time frame is 

a minor change from the proposal, 

which allowed only 14 days for 

resampling (USEPA 2003a), and it 

provides greater flexibility for 

scheduling replacement samples. 

Information that resampling is needed 

includes information the PWS acquires 

directly, as well as notice from the 

shipping company, laboratory, State, or 

EPA. Today’s rule allows States to 

authorize an alternative date for 

collection of the replacement sample. 

This may be needed for resampling to 

occur during the same conditions as the 

originally scheduled sample. 

If collecting a sample was feasible but 

the PWS failed to do so, EPA believes 

that the PWSs must develop a revised 

sampling schedule and submit it to the 

State. This will allow for State 

consultation regarding the reason for the 

missed sample(s) and strategies for the 

PWS to complete the required 

monitoring. 

d. Plants operating only part of the 

year. The proposed LT2ESWTR did not 

include distinct monitoring 

requirements for plants that operate 

only part-year. However, EPA requested 

comment in the proposal on an 

approach to plants that operate only 

part-year that is similar to the 

requirements in today’s final rule 

(USEPA 2003a). 

Monitoring requirements for plants 

that operate only part-year derive from 

three considerations: (1) A PWS should 

sample only during the months when a 

treatment plant operates; (2) the mean 

Cryptosporidium level used for bin 

classification can be determined with 

fewer samples in plants that operate 

only part-year because source water 

quality typically varies less during the 

shorter operating period; and (3) a 

minimum number of samples is 

necessary to classify any plant in an 

LT2ESWTR bin with high confidence. 

The basis for the first consideration is 

straightforward. Source water 

monitoring under the LT2ESWTR is 

used to establish treatment 

requirements, and these should be based 


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on the water quality when a plant is in 

operation. The rationale for the second 

and third considerations stems from 

analyses, similar to those described 

previously, of potential 

misclassification rates in assigning 

plants to LT2ESWTR treatment bins. 

Source water variability is one factor 

that influences the number of samples 

needed to accurately classify plants in 

LT2ESWTR treatment bins. As 

variability increases, more samples are 

needed to determine the mean 

Cryptosporidium level with high 

confidence. EPA does not have data on 

source water variability specifically in 

plants that operate only part-year. 

However, survey data show that 

pathogen levels vary seasonally, and 

plants operating part-year will generally 

experience less variability during a 

given year than plants operating yearround. Consequently, fewer samples are 

typically needed to determine the mean 

Cryptosporidium level during the 

period of operation for a part-year plant. 

Nevertheless, even when a plant 

operates for only a few months per year 

and source water exhibits little 

variability, a minimum number of 

samples is necessary for bin 

classification. This is due to the 

relatively low sample volume, variable 

method recovery, nonhomogeneous 

distribution of Cryptosporidium in 

water, and other factors that limit the 

accuracy of any individual sample for 

characterizing the source water. Data 

suggest that for plants operating for six 

months per year or less, collecting a 

minimum of six samples per year over 

two years may allow bin classification 

with comparable accuracy to that 

achieved by year-round plants sampling 

monthly (USEPA 2005a). 

Based on these considerations, today’s 

rule requires similar source water 

monitoring for plants that operate only 

part-year during their months of 

operation as is required for year-round 

plants. However, if the plant is required 

to monitor for Cryptosporidium and 

operates for six months or less, the PWS 

must collect at least six 

Cryptosporidium samples per year over 

two years. 

e. Failing to monitor. Requirements 

for PWSs that fail to conduct source 

water monitoring are based on the need 

for PWSs to determine a 

Cryptosporidium bin classification and 

provide the appropriate level of public 

health protection within the compliance 

time frame. The LT2ESWTR proposal 

required PWSs that did not complete all 

source water monitoring requirements 

to meet the requirements of the highest 

treatment bin (USEPA 2003a). In today’s 

final rule, EPA has significantly 

changed requirements from those in the 

proposal for PWSs that fail to monitor. 

These changes are intended to give 

States more flexibility in working with 

PWSs to fulfill monitoring requirements 

and ensure they achieve the appropriate 

Cryptosporidium treatment level. 

For most monitoring and testing 

procedure violations under the 

LT2ESWTR, PWSs must provide a Tier 

3 public notification, which is standard 

for this type of violation under an 

NPDWR. However, if a PWS fails to 

collect three or more Cryptosporidium 

samples, the violation is elevated to a 

Tier 2 special public notice. The reason 

for elevating the public notice at this 

point is the persistence of the violation 

and the difficulty the PWS will have in 

collecting the required number of 

samples for bin classification by the 

compliance date. Section IV.H provides 

further details on public notice 

requirements of the LT2ESWTR. 

As described in section IV.G, today’s 

rule requires bin classification within 

six months following the end of the 

monitoring period specified for the 

PWS. This six-month period provides 

some opportunity for collecting and 

analyzing missed samples. The number 

of samples that can be made up in this 

period is limited, though, due to the 

need for samples to be evenly 

distributed throughout the year, as well 

as for PWSs and States to spend time 

during this period evaluating 

monitoring results to determine bin 

classification. In consideration of these 

factors, EPA believes that elevating the 

public notice when a PWS has missed 

three or more Cryptosporidium samples 

is appropriate. This violation will end 

when the State determines that the PWS 

has begun sampling on a schedule to 

collect the required number of samples. 

Failure by a PWS to collect the 

required number of Cryptosporidium 

samples for bin classification by the 

compliance date is a treatment 

technique violation with a required Tier 

2 public notice. This violation reflects 

the inability of the PWS to determine 

and comply with its Cryptosporidium 

treatment requirements under the 

LT2ESWTR and provide the appropriate 

level of public health protection. The 

violation ends when the State 

determines that the PWS is carrying out 

a monitoring plan that will lead to bin 

classification. A PWS that has already 

provided a Tier 2 public notice for 

missing three sampling dates and is 

successfully meeting a State-approved 

sampling schedule is not required to 

issue another public notice for missing 

the bin classification date. Alternatively, 

the PWS can choose to provide the 

highest level of Cryptosporidium 

treatment required under the rule, 

which is 5.5-log for filtered PWSs and 

3-log for unfiltered PWSs. 

f. Grandfathering previously collected 

data. Requirements for grandfathering 

previously collected monitoring data in 

today’s final rule are similar to those in 

the proposal (USEPA 2003a). These 

requirements are based on the principle 

that to be eligible for grandfathering, 

previously collected data must be 

equivalent in quality to data that will be 

collected under the rule. 

The Stage 2 M–DBP Advisory 

Committee recommended that EPA 

accept previously collected 

Cryptosporidium data that are 

‘‘equivalent in sample number, 

frequency, and data quality (e.g. volume 

analyzed, percent recovery) to data that 

would be collected under the 

LT2ESWTR * * * to determine bin 

classification in lieu of further 

monitoring’’ (USEPA 2000a). The 

Advisory Committee recognized that 

accepting previously collected data 

could have a number of benefits, 

including early determination of 

LT2ESWTR compliance needs, 

increasing laboratory capacity, and 

allowing PWSs to determine their bin 

classification using a larger, and 

potentially more representative, data 

set. 

To ensure equivalent data quality, 

today’s rule requires that grandfathered 

data meet the same requirements for 

analytical methods, sampling location, 

and sample volume as data collected 

under the rule. PWSs must not 

selectively report monitoring results for 

grandfathering. Further, grandfathered 

Cryptosporidium data must generally be 

collected at least monthly and on a 

regular schedule, with the same 

provisions for delayed or replacement 

samples as allowed for regular 

monitoring. Today’s final rule differs 

from the proposal, however, in making 

allowances for use of previously 

collected data where irregularities or 

gaps in the sampling frequency occur. 

EPA recognizes that when PWSs 

collected Cryptosporidium data prior to 

the proposed or final LT2ESWTR, there 

may have been months when a PWS 

either failed to collect or lost a sample 

due to problems with equipment, 

transportation, laboratory analysis, or 

other reasons. If the PWS did not collect 

a replacement sample, gaps in the 

previously collected data set occurred. 

EPA believes that grandfathering of such 

a data set may be appropriate despite 

these gaps if the PWS conducts 

additional monitoring, as necessary, to 

‘‘fill-in’’ gaps and ensure that the data 

set is unbiased. Consequently, today’s 

rule allows grandfathering of data with 


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gaps in the sampling frequency if 

approved by the State. 

In addition, if the frequency of 

sampling in a previously collected data 

set varies, EPA believes the data could 

still be appropriate for use in bin 

classification. For example, a PWS 

might have sampled for 

Cryptosporidium once per month for a 

number of months and then increased 

the sampling frequency to twice per 

month. Today’s rule allows the use of 

such a data set. However, to avoid bias, 

the PWS must calculate a monthly 

average for each month of sampling and 

then determine the bin classification 

using these monthly averages, rather 

than the individual sample 

concentrations. 

Today’s rule requires PWSs that plan 

to grandfather monitoring data to notify 

EPA or the State regarding the number 

and time span of sample results no later 

than three months prior to when the 

PWS must begin monitoring. The timing 

for submission of this notice is 

concurrent with the submission of a 

sampling schedule. This notification is 

necessary for the State to determine that 

a PWS is not required to submit a 

sampling schedule (when a PWS will 

fully comply with initial monitoring 

through grandfathering) or that a 

sampling schedule may include less 

than the full number of required 

samples (when a PWS will conduct new 

monitoring in conjunction with 

grandfathering to complete a data set). 

Further, this notice will assist EPA and 

States in determining the resources 

necessary to ensure timely review of 

grandfathered data. 

PWSs must submit all monitoring 

results for grandfathering to EPA or the 

State, along with required supporting 

documentation, no later than two 

months after the PWS is required to 

begin monitoring. This timing will 

allow a PWS to continue collecting data 

for grandfathering until the month the 

PWS is required to begin monitoring 

under today’s rule, plus an additional 

two months for sample analysis and 

compilation of the data for submission. 

This reporting deadline for 

grandfathering monitoring results is a 

change from the proposed rule. In the 

proposal, a PWS that intended to 

grandfather data in lieu of conducting 

new monitoring under the rule had to 

submit its grandfathered results no later 

than four months prior to when the 

PWS was otherwise required to begin 

monitoring under the rule. This 

proposed approach had the shortcoming 

that a PWS could not complete its 

monitoring for grandfathering within 

this four month period. In today’s final 

rule, a PWS may continue monitoring 

for grandfathering all the way until the 

date when the PWS must begin 

monitoring under the rule, if necessary. 

PWSs that conclude their monitoring for 

grandfathering earlier may submit the 

data at an earlier date. 

g. Ongoing watershed assessment. 

Treatment requirements under the 

LT2ESWTR are based on source water 

quality. Consequently, today’s rule 

requires watershed assessment and, as 

described in the next section, a second 

round of monitoring following initial 

bin classification to determine if source 

water quality has changed to the degree 

that the treatment level should be 

modified. These requirements are 

unchanged from those in the proposed 

LT2ESWTR (USEPA 2003a), with the 

exception of an allowance for States to 

use programs other than the sanitary 

survey to assess changes in the 

watershed. 

Today’s rule leverages the existing 

requirement for States to perform 

sanitary surveys on surface water PWSs. 

During the source water review in the 

sanitary survey, today’s rule requires 

States to determine if significant 

changes have occurred in the watershed 

that could lead to increased 

contamination by Cryptosporidium. The 

State can also choose to make this 

determination through an equivalent 

review of the source water under a 

program other than the sanitary survey, 

such as a Source Water Protection 

Assessment. If the State determines that 

significant changes have occurred, the 

State may specify that the PWS conduct 

additional source water monitoring or 

treat the potential contamination. This 

approach allows the PWS and State to 

respond to a significant change in 

source water quality prior to initiating a 

second round of monitoring or any time 

thereafter. 

h. Second round of monitoring. A 

more rigorous reassessment of the 

source water occurs through a second 

round of monitoring that begins six 

years after initial bin classification. If 

EPA does not develop and finalize 

modifications to the LT2ESWTR prior to 

the date when PWSs must begin the 

second round of monitoring, then this 

second round must conform to the same 

requirements that applied to the initial 

round of monitoring. PWSs may be 

classified in a different treatment bin, 

depending on the results of the second 

round of monitoring. 

The Stage 2 M–DBP Advisory 

Committee recommended that EPA 

initiate a stakeholder process several 

years prior to the second round of 

monitoring to review new information 

and determine if today’s rule should be 

modified. If the Agency modifies the 

LT2ESWTR, the second round of 

monitoring would potentially involve a 

new analytical method and a different 

treatment bin structure. 

3. Summary of Major Comments 

Public comment on the August 11, 

2003, LT2ESWTR proposal generally 

supported the use of source water 

monitoring to determine additional 

treatment requirements. The following 

discussion summarizes major comments 

and EPA’s responses in regard to 

sampling parameters and frequency, 

sampling location, sampling schedule, 

monitoring plants that operate only 

part-year, failing to monitor, providing 

treatment instead of monitoring, 

grandfathering previously collected 

data, ongoing source water assessment, 

second round of monitoring, and new 

source monitoring. 

a. Sampling parameters and 

frequency. Most commenters supported 

the proposed requirements for large 

PWSs to sample monthly for 

Cryptosporidium, as well as for E. coli 

and turbidity in filtered PWSs, for 24 

months. Alternatives recommended by 

some commenters included ending 

monitoring after one year if no oocysts 

are detected, allowing large PWSs to use 

an E. coli screening analysis to 

determine if Cryptosporidium 

monitoring is necessary, and using 

watershed data to determine treatment 

needs instead of source water 

monitoring. 

In response, EPA continues to believe 

that large PWSs should complete 24 

months of Cryptosporidium monitoring, 

regardless of the first-year results, in 

order to capture a degree of annual 

variability in Cryptosporidium 

occurrence. Moreover, for the reasons 

discussed previously in this preamble, 

EPA continues to support the Advisory 

Committee recommendation that all 

large PWSs should monitor for 

Cryptosporidium, rather than use the E. 

coli screening analysis. EPA is not 

aware of studies that support the use of 

other watershed data in place of 

Cryptosporidium monitoring to 

determine treatment needs. 

Regarding requirements for small 

PWSs, most commenters supported the 

E. coli screening analysis for small 

filtered PWSs. Several commenters 

recommended more options for 

Cryptosporidium monitoring by small 

PWSs, such as allowing monitoring to 

be spread over two years, instead of the 

one year required in the proposal, or 

allowing fewer samples. EPA agrees that 

budgeting for Cryptosporidium 

monitoring by some small PWSs will be 

easier if it is spread over two years, and 

today’s rule allows this as an option. 


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However, based on the analysis of false 

negative and false positive rates 

described previously, EPA continues to 

believe that at least 24 Cryptosporidium 

samples are necessary to determine the 

appropriate bin classification for yearround plants. 

b. Sampling location. With respect to 

sampling location requirements, several 

commenters recommended that PWSs 

be allowed to collect samples either 

before or after pretreatment processes. 

These commenters stated that the 

chemicals used in pretreatment 

processes are unlikely to affect the 

analysis of Cryptosporidium oocysts at 

typical concentrations. Further, where 

sampling is conducted prior to a 

pretreatment process like 

presedimentation, commenters 

supported allowing PWSs to receive 

additional treatment credit for the 

process. 

In response, EPA continues to believe 

that common pretreatment chemicals 

like oxidants and coagulants have the 

potential to adversely affect the 

performance of Cryptosporidium 

analytical methods. Consequently, 

today’s rule requires that in most cases, 

PWSs must sample upstream of 

chemical addition. Where PWSs sample 

prior to pretreatment processes like 

presedimentation with coagulation, they 

are eligible to receive additional 

treatment credit for the process. 

However, if sampling prior to chemical 

addition is not feasible for a particular 

plant and the treatment chemical is 

present at a very low level that is 

unlikely to interfere with sample 

analysis, the State may approve 

sampling after chemical addition. 

Many commenters recommended that 

States approve sampling locations for 

their PWSs. Commenters indicated that 

State review and approval of monitoring 

plans will help to prevent confusion 

and PWSs potentially sampling at an 

incorrect location. EPA agrees with 

these commenters and has established a 

requirement in today’s rule for PWSs to 

report a description of the sampling 

location to the State. If a PWS does not 

hear back from the State by the time it 

is scheduled to begin sampling, it may 

assume that its monitoring location is 

acceptable. 

c. Sampling schedule. In regard to 

sampling schedule requirements, 

several commenters requested that 

PWSs be given a time window larger 

than 5 days around scheduled sampling 

dates to collect samples. Recommended 

alternatives included a 7 or 9-day 

window, or only requiring that PWSs 

collect a sample within a specified 

month. In addition, commenters 

identified situations that interfere with 

sample collection, such as plant 

interruptions and laboratory or 

transportation problems, and noted that 

some of these are outside the conditions 

under which the proposal allowed a 

PWS to collect a delayed or replacement 

sample without penalty. 

In response, EPA continues to believe 

that for routine sample collection, a 5- 

day window provides sufficient 

flexibility, given that PWSs will pick the 

sampling days and can schedule around 

holidays, weekends, and other times 

when sampling would be problematic. 

However, today’s rule allows PWSs to 

sample outside of this window without 

penalty if necessary due to unforeseen 

conditions. Further, if a PWS collects a 

sample but is unable to have it analyzed 

due to problems with equipment, 

transportation or the laboratory, today’s 

rule allows the PWS to collect a 

replacement sample without penalty. 

In regard to the time frame for 

collecting missed or replacement 

samples, commenters recommended a 

number of approaches. These include 

adding extra sampling days to the 

original sampling schedule, which a 

PWS could then use in the event of 

missed sampling dates, and allowing 

PWSs to collect make-up samples either 

immediately after the scheduled 

sampling date or at the end of the 

monitoring period. 

In general, EPA considers it preferable 

for PWSs to collect missed or 

replacement samples as close as is 

feasible to scheduled sampling dates. 

However, if there is a significant delay 

with respect to the original sampling 

date, collecting make-up samples at an 

alternate time may be appropriate to 

ensure that sampling results are 

seasonally representative. Therefore, 

today’s rule requires PWSs to collect a 

missed sample as close as is feasible to 

the scheduled sampling date, and to 

collect replacement samples within 21 

days of receiving information that one is 

needed, unless doing so within this time 

frame is not feasible. However, the State 

can authorize alternative sampling dates 

so that monitoring is not seasonally 

biased. This could include sampling 

during the same time in the following 

year, if the missed sample occurred 

during the first year of monitoring, or 

sampling after the end of the scheduled 

monitoring period. 

d. Plants operating only part of the 

year. Commenters on monitoring 

requirements for surface water plants 

that operate for only part of the year 

generally recommended that sampling 

occur only during the period of 

operation. However, several different 

options were put forward for how the 

sampling be conducted. Some 

commenters recommended a minimum 

of 12 samples per year for two years 

distributed evenly over the period that 

the plant operates. Others suggested 

allowing the PWS to collect the required 

number of samples over a longer time 

period in order to limit the frequency of 

required samples when the plant is 

operating. Several commenters said that 

State input is critical to determining the 

appropriate monitoring period since 

States may have historical knowledge of 

plant operating practices. 

In response, EPA agrees that 

monitoring of plants that operate only 

part-year under today’s rule should be 

conducted only during months when 

the plant is operating, unless the State 

determines that a longer monitoring 

period is appropriate due to historical 

operating practices. Further, plants that 

operate only part-year should maintain 

the same sampling frequency as plants 

operating year-round, with the 

exception that plants monitoring for 

Cryptosporidium must collect at least 

six samples per year to allow for 

appropriate bin classification. EPA does 

not believe extending monitoring over 

more years in plants that operate only 

part-year is appropriate, as this would 

delay the installation of additional 

treatment where needed. 

e. Failing to monitor. Most 

commenters opposed automatically 

classifying PWSs in the highest 

treatment bin (Bin 4) if they fail to 

complete required monitoring, as the 

proposed rule stipulated. Commenters 

suggested alternative approaches, such 

as giving States the flexibility to address 

missed samples using current 

enforcement mechanisms, classifying a 

PWS only one level higher than the bin 

determined by the collected data, 

allowing an additional year of sampling, 

and allowing States to use other 

information (e.g., sanitary surveys, other 

monitoring data) to aid in the 

classification. A few commenters, 

however, supported Bin 4 classification 

for PWSs that fail to monitor, on the 

basis that any other approach would 

create an incentive for PWSs to stop 

testing if poor water quality is 

suspected. 

EPA agrees that States should have 

flexibility in dealing with PWSs that fail 

to monitor. Further, providing the 

highest level of treatment may not be in 

the best interests of consumers where a 

PWS has minor problems in carrying 

out source water monitoring. However, 

EPA also believes that violations for 

monitoring failures must reasonably 

ensure that PWSs complete monitoring 

as required to determine a bin 

classification within the compliance 


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date. Failure to do so would potentially 

compromise public health protection. 

Based on these considerations, EPA 

has not established an automatic Bin 4 

classification for monitoring failures 

under today’s rule. Rather, if a PWS 

misses three or more Cryptosporidium 

samples, this persistent violation 

requires a Tier 2 public notice (other 

violations require a Tier 3 notice). 

Further, if a PWS is unable to determine 

a bin classification by the compliance 

date due to failure to collect the 

required number of Cryptosporidium 

samples, this is a treatment technique 

violation with a required Tier 2 public 

notice (unless the PWS has already 

issued a Tier 2 notice for missing 3 

Cryptosporidium samples and is 

monitoring on a State-approved 

schedule). These violations last until the 

State determines that a PWS has begun 

monitoring on a schedule that will lead 

to bin classification or the PWS agrees 

to install treatment instead of 

monitoring. 

f. Providing treatment instead of 

monitoring. Commenters supported the 

option for a PWS to provide the highest 

level of Cryptosporidium treatment 

required under today’s rule rather than 

conducting source water monitoring. 

Several commenters recommended that 

a PWS should be allowed to take this 

option after having initiated monitoring. 

EPA agrees, and today’s rule allows a 

PWS to stop monitoring at any time by 

notifying the State that it will provide 

5.5-log Cryptosporidium treatment for 

filtered PWSs or 3-log Cryptosporidium 

inactivation for unfiltered PWSs by the 

compliance deadline specified in 

section IV.G. 

g. Grandfathering previously collected 

data. With respect to grandfathering 

previously collected data, many 

commenters expressed concern with a 

proposed requirement that samples 

must have been collected in equal time 

intervals. Commenters stated that 

although PWSs may have sampled on a 

regular schedule, previously collected 

data sets are likely to have gaps due to 

samples rejected for method QC 

violations or periods when the PWS was 

unable to collect a sample. In addition, 

there are instances where PWSs have 

changed the frequency of sampling, 

such as from monthly to twice per 

month. 

EPA agrees that if a PWS has collected 

samples according to a regular schedule 

and met other data quality standards, 

then rejecting a large data set due to 

isolated gaps in the sampling frequency 

would be inappropriate. Consequently, 

today’s rule allows States to approve 

grandfathering of previously collected 

data with omissions in the sampling 

interval, provided the PWS conducts 

additional monitoring if required by the 

State to ensure the data set is seasonally 

representative. Further, PWSs may 

grandfather previously collected data 

sets in which the sampling frequency 

varies, as long as samples were collected 

at least monthly. In this situation, PWSs 

must use monthly average 

concentrations, rather than individual 

sample concentrations, for bin 

classification. 

With respect to data quality 

standards, such as meeting analytical 

method QC criteria, sampling at the 

correct location, and analyzing the 

minimum sample volume, several 

commenters stated that EPA should 

apply the same acceptance standards to 

previously collected data as are applied 

to data collected under today’s rule. 

Other commenters, though, suggested 

that States should have the flexibility to 

accept previously collected data that 

deviate from the data quality standards 

for monitoring under the rule. These 

commenters stated that such data sets 

might include samples collected over a 

longer period of time and may reflect 

more worst-case weather events. 

In response, EPA believes that data 

quality standards should be uniformly 

applied under today’s rule, so that 

previously collected data should not be 

held to a lower standard than new data 

or evaluated differently from State to 

State. The requirements in today’s rule 

with respect to Cryptosporidium 

analytical methods and minimum 

sample volume reflect recommendations 

of the Advisory Committee, which also 

recommended that the same data quality 

standards be applied for grandfathering. 

Further, because today’s rule allows 

PWSs to collect make-up samples to 

address gaps in previously collected 

data sets, PWSs will have the 

opportunity to collect make-up samples 

for results that are rejected due to data 

quality standards without losing an 

entire data set. 

In regard to notification of the 

acceptability of data for grandfathering, 

commenters recommended that if 

previously collected data submitted by 

a PWS are rejected, the PWS should 

have at least two months between 

notification and the date new 

monitoring must be initiated. These two 

months will give the PWS time to 

address rejection of the data and prepare 

for sampling. EPA agrees with this 

recommendation. Under today’s rule, if 

a PWS properly submits a complete data 

set for grandfathering and the PWS must 

conduct new monitoring due to 

rejection of the data, the PWS has at 

least two months following notification 

by the State to initiate sampling. 

h. Ongoing watershed assessment. 

Commenters asked for greater flexibility 

in the requirement for States to 

determine whether there have been 

significant changes in the watersheds of 

their PWSs that could lead to increased 

contamination. The proposed rule 

specified that States must make this 

determination during sanitary surveys. 

However, several commenters noted 

that some States perform source water 

protection assessments on the same 

frequency as sanitary surveys, and these 

detailed assessments might be a better 

mechanism to monitor changes in the 

watershed. EPA agrees and today’s rule 

allows States to determine whether 

significant changes have occurred in the 

watershed through either a sanitary 

survey or an equivalent review of the 

source water under another program. 

i. Second round of monitoring. Some 

commenters supported the proposed 

requirement for a second round of 

source water monitoring, but most 

opposed requiring it for all PWSs. These 

commenters recommended that States 

should be authorized to use sanitary 

surveys, source water assessments, 

ambient water quality data, treatment 

plant data, and other information to 

determine if a second round of 

monitoring is necessary for a PWS. 

Some commenters suggested that EPA 

fund research to allow the use of 

finished water monitoring as the 

determinant for treatment requirements 

in a second round of monitoring. 

In response, EPA continues to believe 

that PWSs should conduct a second 

round of monitoring to determine if the 

level of treatment required as a result of 

the first round of monitoring is still 

appropriate. Consequently, today’s rule 

requires this. However, EPA agrees that 

prior to a second round of monitoring, 

the Agency should evaluate the results 

of the first round of monitoring, along 

with whatever new information is 

available on Cryptosporidium analytical 

methods, risk, and other relevant issues. 

If EPA determines that there should be 

changes to the requirements for a 

second round of monitoring in today’s 

rule, the Agency will issue a new rule 

establishing those changes. 

j. New source monitoring. EPA 

requested comment in the proposal on 

monitoring requirements for new plants 

and sources (USEPA 2003a). Most 

commenters recommended that new 

plants and sources undergo monitoring 

equivalent to that required for existing 

plants and sources, and suggested that 

States should have discretion to 

determine when monitoring should take 

place. EPA agrees with these 

recommendations and today’s rule 

requires PWS to conduct source water 


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monitoring for new plants and sources 

on a schedule approved by the State. 

This schedule must include dates for 

the PWS to determine its treatment bin 

classification and, if necessary, comply 

with additional Cryptosporidium 

treatment requirements. 

B. Filtered System Cryptosporidium 

Treatment Requirements 

1. Today’s Rule 

Today’s rule requires filtered PWSs 

using surface water or GWUDI sources 

to provide greater levels of treatment if 

their source waters have higher 

concentrations of Cryptosporidium. 

Specifically, filtered PWSs are classified 

in one of four treatment bins based on 

results from the source water 

monitoring described in the previous 

section. PWSs classified in the lowest 

concentration bin are subject to no 

additional treatment requirements, 

while PWSs assigned to higher 

concentration bins must reduce 

Cryptosporidium levels beyond IESWTR 

and LT1ESWTR requirements. All PWSs 

must continue to comply with the 

requirements of the SWTR, IESWTR, 

and LT1ESWTR, as applicable. 

This section addresses procedures for 

classifying filtered PWSs in 

Cryptosporidium treatment bins and the 

treatment requirements associated with 

each bin. Section IV.D presents the 

treatment and control options, 

collectively termed the ‘‘microbial 

toolbox,’’ that PWSs must use to meet 

additional Cryptosporidium treatment 

requirements under today’s rule. 

a. Bin classification. After completing 

initial source water monitoring, filtered 

PWSs must calculate a Cryptosporidium 

bin concentration for each treatment 

plant where Cryptosporidium 

monitoring is required. This 

Cryptosporidium bin concentration is 

used to classify filtration plants in one 

of the four treatment bins shown in 

Table IV.B–1. 

TABLE IV.B–1.—BIN CLASSIFICATION TABLE FOR FILTERED PWSS

For PWSs that are: with a Cryptosporidium bin concentration of . . . The bin classification 

is . . . 

* * * required to monitor for Cryptosporidium ................. less than 0.075 oocysts/L ............................................... Bin 1. 

0.075 oocysts/L or higher, but less than 1.0 oocysts/L .. Bin 2. 

1.0 oocysts/L or higher, but less than 3.0 oocysts/L ...... Bin 3. 

3.0 oocysts/L or higher ................................................... Bin 4. 

* * * serving fewer than 10,000 people and NOT required to monitor for Cryptosporidium 1.NA ................................................................................... Bin 1. 

1Filtered PWSs serving fewer than 10,000 people are not required to monitor for Cryptosporidium if they monitor for E. coli and demonstrate a 

mean concentration of E. coli less than or equal to 10/100 mL for lake/reservoir sources or 50/100 mL for flowing stream sources or do not exceed an alternative State-approved indicator trigger (see section IV.A.1). 

In general, the Cryptosporidium bin 

concentration is calculated by averaging 

individual sample results from one or 

more years of monitoring. Specific 

procedures vary, however, depending 

on the frequency and duration of 

monitoring. These procedures are as 

follows: 

(1) For PWSs that collect a total of at 

least 24 but not more than 47 

Cryptosporidium samples over two or 

more years, the Cryptosporidium bin 

concentration is equal to the highest 

arithmetic mean of all sample 

concentrations in any 12 consecutive 

months of Cryptosporidium monitoring. 

(2) For PWSs that collect a total of at 

least 48 samples, the Cryptosporidium 

bin concentration is equal to the 

arithmetic mean of all sample 

concentrations. 

(3) For PWSs that serve fewer than 

10,000 people and monitor for 

Cryptosporidium for only one year (i.e., 

collect 24 samples in 12 months), the 

Cryptosporidium bin concentration is 

equal to the arithmetic mean of all 

sample concentrations. 

(4) For PWSs with plants that operate 

only part-year that monitor for less than 

12 months per year, the 

Cryptosporidium bin concentration is 

equal to the highest arithmetic mean of 

all sample concentrations during any 

year of Cryptosporidium monitoring. 

In data sets with variable sampling 

frequency, PWSs must first calculate an 

arithmetic mean for each month of 

sampling and then apply one of these 

four procedures using the monthly 

mean concentrations. As described in 

section IV.A, PWSs may grandfather 

previously collected Cryptosporidium 

data where the sampling frequency 

varies (e.g., one year of monthly 

sampling and one year of twice-permonth sampling). 

Filtered PWSs serving fewer than 

10,000 people are not required to 

monitor for Cryptosporidium if they 

demonstrate a mean E. coli 

concentration less than or equal to 10/ 

100 mL for lake/reservoir sources or 50/ 

100 mL for flowing stream sources or do 

not exceed an alternative Stateapproved indicator trigger. PWSs that 

meet this criterion are classified in Bin 

1 as shown in Table IV.B–1. 

When determining the 

Cryptosporidium bin concentration, 

PWSs must calculate individual sample 

concentrations as the total number of 

oocysts counted, divided by the volume 

assayed (see section V.K for details). In 

samples where no oocysts are detected, 

the result is assigned a value of zero for 

the purpose of calculating the bin 

concentration. Sample analysis results 

are not adjusted for analytical method 

recovery or the percent of 

Cryptosporidium oocysts that are 

infectious. 

PWSs must report their treatment bin 

classification to the State for approval 

following initial source water 

monitoring (see section IV.G for specific 

compliance dates). The report must 

include a summary of the data and 

calculation procedure used to determine 

the bin concentration. If EPA does not 

amend today’s rule before the second 

round of monitoring described in 

section IV.A, PWSs must recalculate 

their bin classification after completing 

the second round of monitoring and 

report the results to the State for 

approval. If the State does not respond 

to a PWS regarding its bin classification 

after either report, the PWS must 

comply with the Cryptosporidium 

treatment requirements of today’s rule 

based on the reported bin classification. 

b. Bin treatment requirements. Table 

IV.B–2 shows the additional 

Cryptosporidium treatment 

requirements associated with the four 

treatment bins for filtered PWSs under 

today’s rule. All filtered PWSs must 

comply with these treatment 

requirements based on their bin 

classification, which must be 

determined using the procedures just 

described. 


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TABLE IV.B–2.—TREATMENT REQUIREMENTS FOR LT2ESWTR BIN CLASSIFICATIONS

If your bin classification 

is . . . 

And you use the following filtration treatment in full compliance with the SWTR, IESWTR, and LT1ESWTR (as applicable), then your additional treatment requirements are . . . 

Conventional filtration treatment 1, diatomaceous earth filtration, or slow 

sand filtration 

Direct filtration Alternative filtration technologies 

Bin 1 ................................. No additional treatment ..................... No additional treatment ..................... No additional treatment. 

Bin 2 ................................. 1-log treatment 2 ................................ 1.5-log treatment 2 ............................. As determined by the State 2 4

Bin 3 ................................. 2-log treatment 3 ................................ 2.5-log treatment 3 ............................. As determined by the State 3 5

Bin 4 ................................. 2.5-log treatment 3 ............................. 3-log treatment 3 ................................ As determined by the State 3 6

1Applies to a treatment train using separate, sequential, unit processes for coagulation/flocculation, clarification, and granular media filtration. 

Clarification includes any solid/liquid separation process following coagulation where accumulated solids are removed during this separate component of the treatment system. 2PWSs may use any technology or combination of technologies from the microbial toolbox in section IV.D. 

3PWSs must achieve at least 1-log of the required treatment using ozone, chlorine dioxide, UV, membranes, bag filtration, cartridge filtration, 

or bank filtration. 4Total Cryptosporidium removal and inactivation must be at least 4.0 log. 

5Total Cryptosporidium removal and inactivation must be at least 5.0 log. 

6Total Cryptosporidium removal and inactivation must be at least 5.5 log. 

The total Cryptosporidium treatment 

required for plants in Bins 2, 3, and 4 

is 4.0-log, 5.0-log, and 5.5-log, 

respectively. Conventional treatment 

(including softening), slow sand, and 

diatomaceous earth filtration plants in 

compliance with the IESWTR or 

LT1ESWTR, as applicable, receive a 

prescribed 3.0-log Cryptosporidium 

treatment credit toward these total bin 

treatment requirements. Accordingly, 

these plant types must provide 1.0- to 

2.5-log of additional treatment when 

classified in Bins 2–4, respectively. 

Direct filtration plants in compliance 

with existing regulations receive a 

prescribed 2.5-log treatment credit and, 

consequently, must achieve 0.5-log 

greater treatment to comply with Bins 

2–4. Section IV.D describes how States 

may award a level of treatment credit 

that differs from the prescribed credit 

based on a demonstration of 

performance by the PWS. 

For PWSs using alternative filtration 

technologies, such as membranes, bag 

filters, or cartridge filters, no prescribed 

treatment credit is available because the 

performance of these processes is 

specific to individual products. 

Consequently, when PWSs using these 

processes are classified in Bins 2–4, the 

State must determine additional 

treatment requirements based on the 

credit the State awards to a particular 

technology. The additional treatment 

requirements must ensure that plants 

classified in Bins 2–4 achieve total 

Cryptosporidium reductions of 4.0- to 

5.5-log, respectively. Section IV.D 

describes challenge testing procedures 

to determine treatment credit for 

membranes, bag filters, and cartridge 

filters. 

PWSs can achieve additional 

Cryptosporidium treatment credit 

through implementing pretreatment 

processes like presedimentation or bank 

filtration, by developing a watershed 

control program, and by applying 

additional treatment steps like ozone, 

chlorine dioxide, UV, and membranes. 

In addition, PWSs can receive a higher 

level of credit for existing treatment 

processes through achieving very low 

filter effluent turbidity or through a 

demonstration of performance. Section 

IV.D presents criteria for awarding 

Cryptosporidium treatment credit to 

these and other treatment and control 

options, which collectively comprise 

the microbial toolbox. 

PWSs in Bin 2 can meet additional 

Cryptosporidium treatment 

requirements by using any option or 

combination of options from the 

microbial toolbox. For Bins 3 and 4, 

PWSs must achieve at least 1-log of the 

additional treatment requirement by 

using ozone, chlorine dioxide, UV, 

membranes, bag filtration, cartridge 

filtration, or bank filtration. 

2. Background and Analysis 

Today’s rule will increase protection 

against Cryptosporidium and other 

pathogens in PWSs with the highest 

source water contamination levels. This 

targeted approach builds upon existing 

regulations under which all filtered 

PWSs must provide the same level of 

treatment regardless of source water 

quality. EPA’s intent with today’s rule is 

to ensure that PWSs with higher risk 

source waters achieve public health 

protection commensurate with PWSs 

with less contaminated sources. 

The Cryptosporidium treatment 

requirements for filtered PWSs in 

today’s rule are unchanged from the 

August 11, 2003 proposal (USEPA 

2003a) and reflect consensus 

recommendations by the Stage 2 M–DBP 

Advisory Committee (USEPA 2000a). 

The following discussion summarizes 

the Agency’s basis for establishing risktargeted Cryptosporidium treatment 

requirements and for setting the specific 

bin concentration ranges and treatment 

requirements that apply to filtered 

PWSs in today’s rule. 

a. Basis for targeted treatment 

requirements. In developing today’s 

rule, EPA evaluated the degree to which 

new information on Cryptosporidium 

warranted moving beyond existing 

regulations. As discussed in section III, 

the IESWTR established a 

Cryptosporidium MCLG of zero and 

requires large filtered PWSs to achieve 

2-log Cryptosporidium removal. The 

LT1ESWTR extended this requirement 

to small PWSs. After these rules were 

promulgated, advances were made in 

analytical methods and treatment for 

Cryptosporidium, and EPA collected 

new information on Cryptosporidium 

occurrence and infectivity. 

Consequently, EPA assessed the 

implications of these developments for 

further controlling Cryptosporidium to 

approach the zero MCLG. 

The risk-targeted approach for filtered 

PWSs in today’s final rule stems from 

four general findings based on new 

information on Cryptosporidium: 

(1) New data on Cryptosporidium 

infectivity suggest that the risk 

associated with a particular level of 

Cryptosporidium is most likely higher 

than EPA estimated at the time of earlier 

rules; 

(2) New data on Cryptosporidium 

occurrence indicate that levels are 

relatively low in most water sources, but 

a subset of sources has substantially 

higher concentrations; 

(3) The finding that UV light can 

readily inactivate Cryptosporidium, as 

well as other technology developments, 

makes achieving high levels of 


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treatment for Cryptosporidium feasible 

for PWSs of all sizes; and 

(4) EPA Methods 1622 and 1623 are 

capable of assessing annual mean levels 

of Cryptosporidium in drinking water 

sources. 

These findings led EPA to conclude 

that most filtered PWSs currently 

provide sufficient treatment for 

Cryptosporidium, but additional 

treatment is needed in those PWSs with 

the highest source water 

Cryptosporidium levels to protect 

public health. Further, PWSs can 

characterize Cryptosporidium levels in 

their source waters with available 

analytical methods and can provide 

higher levels of treatment with available 

technologies. Consequently, risktargeted treatment requirements for 

Cryptosporidium based on source water 

contamination levels are appropriate 

and feasible to implement. 

b. Basis for bin concentration ranges 

and treatment requirements. To 

establish the risk-targeted treatment 

requirements in today’s rule, EPA had to 

determine the degree of treatment that 

should be required for different source 

water Cryptosporidium levels to protect 

public health. This determination 

involved addressing several questions: 

• What is the risk associated with 

Cryptosporidium in a drinking water 

source? 

• How much Cryptosporidium 

removal do filtration plants achieve? 

• What is the appropriate statistical 

measure for classifying PWSs into 

treatment bins? 

• What degree of additional treatment 

is needed for higher source water 

Cryptosporidium levels? 

• How should PWSs calculate their 

treatment bin classification? 

This section summarizes how EPA 

evaluated these questions in developing 

today’s rule. See the proposed 

LT2ESWTR for further details (USEPA 

2003a). 

What is the Risk Associated With 

Cryptosporidium in a Drinking Water 

Source? 

The risk of infection from 

Cryptosporidium in drinking water is a 

function of exposure (i.e., the dose of 

oocysts ingested) and infectivity (i.e., 

likelihood of infection as a function of 

ingested dose). Primary (i.e., direct) 

exposure to Cryptosporidium depends 

on the concentration of oocysts in the 

source water, the fraction removed by 

the treatment plant, and the volume of 

water consumed (secondary exposure 

occurs through interactions with 

infected individuals). Thus, the daily 

risk of infection (DR) is as follows: 

DR = (oocysts/L in source water) × 

(fraction remaining after treatment) × 

(liters consumed per day) × (likelihood 

of infection per oocyst dose). 

Assuming 350 days of consumption 

per year for people served by 

community water systems (CWSs), the 

annual risk (AR) of infection is as 

follows: 

AR = 1 ¥ (1 ¥ DR) 350. 

As discussed in section III.E, EPA has 

estimated the mean likelihood of 

infection from ingesting one 

Cryptosporidium oocyst to range from 4 

to 16 percent. Median individual daily 

water consumption is estimated as 1.07 

L/day. Figure IV.B–1 illustrates ranges 

for the annual risk of infection by 

Cryptosporidium in CWSs based on 

these values for different source water 

infectious oocyst concentrations and 

treatment plant removal efficiencies. 

The dashed lines represent the 

uncertainty associated with 

Cryptosporidium infectivity for each 

log-removal curve. See Chapter 5 of the 

LT2ESWTR Economic Analysis for 

details (USEPA 2005a). 

BILLING CODE 6560–50–P 


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BILLING CODE 6560–50–C 

The results in Figure IV.B–1 show, for 

example, that if a treatment plant had a 

concentration of infectious 

Cryptosporidium in the source water of 

0.1 oocysts/L and the plant achieved 3- 

log removal, the mean annual risk of 


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Cryptosporidium infection would range 

from 0.0017 to 0.0060 (17 to 60 

infections per 10,000 consumers). In 

comparison, if the same plant had a 

source water infectious 

Cryptosporidium level of 0.01 oocysts/ 

L, the annual infection risk would range 

from 1.7 to 6 per 10,000 consumers. 

How much Cryptosporidium removal do 

filtration plants achieve? 

The amount of Cryptosporidium 

removal that filtration plants achieve 

was a key factor in assessing the 

additional treatment that plants with 

higher source water Cryptosporidium 

levels should provide. To evaluate this 

factor, EPA reviewed studies of 

Cryptosporidium removal by common 

treatment processes. As described in the 

proposal for today’s rule, these 

processes were conventional treatment, 

direct, slow sand, and diatomaceous 

earth filtration, as well as membrane, 

bag, and cartridge filtration (USEPA 

2003a). 

The majority of plants treating surface 

water use conventional treatment, 

which is defined in 40 CFR 141.2 as 

coagulation, flocculation, 

sedimentation, and filtration. In the 

proposal, EPA reviewed studies of 

conventional treatment by Dugan et al. 

(2001), Nieminski and Bellamy (2000), 

McTigue et al. (1998), Patania et al. 

(1999), Huck et al. (2000), Emelko et al. 

(2000), and Harrington et al. (2001). 

Based on these studies, EPA estimated 

that conventional treatment plants in 

compliance with the IESWTR or 

LT1ESWTR typically achieve a 

Cryptosporidium removal efficiency of 

approximately 3-log. Consequently, 

conventional treatment plants receive 3- 

log credit toward Cryptosporidium 

treatment requirements under today’s 

rule. 

This 3-log credit for conventional 

treatment is consistent with the Stage 2 

M–DBP Agreement in Principle (USEPA 

2000a), which states as follows: 

‘‘The additional treatment requirements in 

the bin requirement table are based, in part, 

on the assumption that conventional 

treatment plants in compliance with the 

IESWTR achieve an average of 3 logs removal 

of Cryptosporidium.’’

The M–DBP Advisory Committee did 

not recommend a level of 

Cryptosporidium treatment credit for 

other types of filtration plants. 

EPA also reviewed studies of the 

performance of clarification processes 

like dissolved air flotation, which can 

be used in place of sedimentation in a 

conventional treatment train (Gregory 

and Zabel 1990, Plummer et al. 1995, 

Edzwald and Kelley 1998). These 

studies indicate that plants using 

clarification processes other than 

sedimentation that are located after 

coagulation and prior to filtration can 

achieve performance equivalent to 

conventional treatment plants. As a 

result, any treatment train that includes 

coagulation/flocculation, clarification, 

and granular media filtration is regarded 

as conventional treatment for purposes 

of awarding treatment credit under 

today’s rule. The clarification step must 

be a solid/liquid separation process 

where accumulated solids are removed 

during this separate component of the 

treatment system. 

Direct filtration plants use 

coagulation, flocculation, and filtration 

processes just as conventional treatment 

plants do, but they lack a sedimentation 

basin or equivalent clarification process. 

In the proposal, EPA reviewed studies 

of sedimentation by Dugan et al. (2001), 

States et al. (1997), Edzwald and Kelly 

(1998), Payment and Franco (1993), 

Kelly et al. (1995), and Patania et al. 

(1995). Results from these studies 

demonstrate that sedimentation basins 

can achieve 0.5-log or greater 

Cryptosporidium removal. In addition, 

some studies have observed that direct 

filtration achieves less Cryptosporidium 

removal than conventional treatment 

(Patania et al. 1995) and the incidence 

of Cryptosporidium in the treated water 

is higher (McTigue et al. 1998). Given 

these findings, EPA has awarded direct 

filtration plants a 2.5-log credit towards 

Cryptosporidium treatment 

requirements under today’s rule (i.e., 

0.5-log less credit than for conventional 

treatment). 

Slow sand filtration involves passing 

raw water through a bed of sand at low 

velocity and without prior coagulation. 

Diatomaceous earth filtration is a 

process by which a filtration medium is 

initially deposited onto a support 

membrane and medium is added 

throughout the operation to keep the 

filter from clogging. In the proposal, 

EPA reviewed slow sand filtration 

studies by Fogel et al. (1993), Hall et al. 

(1994), Schuler and Ghosh (1991), and 

Timms et al. (1995) and diatomaceous 

earth filtration studies by Schuler and 

Gosh (1990) and Ongerth and Hutton 

(1997, 2001). For both processes, these 

studies indicate that a well-designed 

and properly operated filter can achieve 

Cryptosporidium removal efficiencies 

similar to those observed for 

conventional treatment plants. Slow 

sand and diatomaceous earth filtration 

plants, therefore, receive a 3-log credit 

towards Cryptosporidium treatment 

requirements under today’s rule. 

Estimating a typical Cryptosporidium 

removal efficiency for filtration 

technologies like membranes, bag filters, 

and cartridge filters is not possible 

because the performance of such filters 

is specific to a particular product. As a 

result, credit for these devices must be 

determined by the State based on 

product-specific testing using the 

procedures described in section IV.D or 

other criteria approved by the State. 

Table IV.B–3 summarizes the credits 

various types of filtration plants receive 

toward Cryptosporidium treatment 

requirements under today’s rule. This 

credit determines the degree of 

additional treatment that plants 

classified in Bins 2–4 must apply, as 

shown in Table IV.B–2. 

TABLE IV.B–3.—CRYPTOSPORIDIUM TREATMENT CREDIT TOWARDS LT2ESWTR REQUIREMENTS 1

Plant type Conventional treatment (includes softening) Direct filtration Slow sand or diatomaceous earth filtration 

Alternative filtration technologies 

Treatment credit ................ 3.0-log ............................... 2.5-log ............................... 3.0-log ............................... Determined by State. 2

1Applies to plants in full compliance with the IESWTR or LT1ESWTR as applicable. 

2 Credit must be determined through product or site-specific assessment. 

As discussed previously, studies 

indicate that conventional treatment 

plants producing very low filtered water 

turbidity can achieve a higher level of 

Cryptosporidium removal than 3-log, 

and today’s rule allows such plants to 

receive additional treatment credit. 

Further, States can award a higher or 

lower level of credit to an individual 

plant based on a site-specific 

demonstration of performance. Section 

IV.D provides details on both of these 

topics. 

The Cryptosporidium removal credits 

for filtration plants in today’s rule differ 

from the amount of credit awarded 

under the IESWTR and LT1ESWTR. As 


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discussed in section III, those rules 

require all filtered PWSs to achieve 2- 

log removal of Cryptosporidium. PWSs 

using conventional treatment, or direct, 

slow sand, or diatomaceous earth 

filtration are in compliance with this 

requirement if they meet specified 

filtered water turbidity standards. These 

regulatory criteria were based on 

consideration of the minimum level of 

removal that all these filtration 

processes will achieve (USEPA 1998a). 

However, in the risk assessments that 

supported these regulations, EPA 

estimated that most filtration plants will 

achieve significantly more removal, 

with median Cryptosporidium 

reductions near 3-log. 

Today’s rule will supplement 

IESWTR and LT1ESWTR requirements 

by mandating additional treatment at 

certain PWSs based on source-water 

Cryptosporidium levels. When assessing 

the need for additional treatment at 

potentially higher risk PWSs, EPA 

believes that considering the full 

removal efficiency achieved by different 

types of treatment plants is appropriate. 

Because making a site-specific 

assessment of removal efficiency at all 

treatment plants individually is not 

feasible, establishing prescribed 

treatment credits based on available 

data is necessary. Accordingly, EPA has 

concluded that available data support 

the higher levels of prescribed credit 

towards Cryptosporidium treatment 

requirements for filtration plants 

established by today’s rule. 

What is the appropriate statistical 

measure for classifying PWSs into 

treatment bins? 

EPA and the Advisory Committee 

evaluated different statistical measures 

for characterizing Cryptosporidium 

monitoring results to determine if 

additional treatment should be required. 

These measures included the arithmetic 

mean, median, 90th percentile, and 

maximum. 

EPA concluded, consistent with 

Advisory Committee recommendations, 

that Cryptosporidium levels should be 

characterized by an arithmetic mean. 

This conclusion is based on two factors: 

(1) Available data suggest that the mean 

concentration directly relates to the 

average risk of the exposed population 

(i.e., drinking water consumers); and (2) 

with a limited number of samples, the 

mean can be estimated more accurately 

than other statistical measures, such as 

a 90th percentile estimate. 

What degree of additional treatment is 

needed for higher source water 

Cryptosporidium levels? 

Development of the risk-based 

treatment requirements in today’s rule 

involved first determining the threshold 

source-water Cryptosporidium level at 

which filtered PWSs should provide 

additional treatment to protect public 

health. The key factors in making this 

determination were the estimations of 

Cryptosporidium risk and treatment 

plant removal efficiency discussed 

previously, along with the performance 

of analytical methods for classifying 

PWSs in different treatment bins. 

EPA and Advisory Committee 

deliberations focused on mean sourcewater Cryptosporidium concentrations 

in the range of 0.01 to 0.1 oocysts/L as 

threshold levels for requiring additional 

treatment. Based on the type of risk 

information shown in Figure IV.B–1, 

these levels are estimated to result in an 

annual infection risk in the range of 1.7 

× 10¥4 to 6.0 × 10¥3 (or 1.7 to 60 

infections per 10,000 consumers) for a 

treatment plant achieving 3-log 

Cryptosporidium removal (the treatment 

efficiency estimated for conventional 

plants under existing regulations). 

A shortcoming with establishing the 

threshold for additional treatment at 

0.01 oocysts/L, however, is that a PWS 

would exceed this concentration with 

only a very few oocysts being detected. 

For a PWS collecting monthly 10-L 

samples and bin classification based on 

the maximum running annual average, 

as required under today’s rule, detecting 

two oocysts during one year of 

monitoring would exceed a mean of 

0.01 oocysts/L. Given the uncertainty 

associated with Cryptosporidium 

monitoring, EPA and the Advisory 

Committee did not support requiring 

additional treatment for filtered PWSs 

based on so few counts. Although this 

shortcoming could theoretically be 

addressed by a higher sampling 

frequency, the feasibility of increased 

sampling is limited by the capacity of 

laboratories and the cost of sample 

analysis. 

A related concern in establishing the 

threshold concentration for requiring 

additional treatment was bin 

misclassification. If the threshold 

concentration was set at 0.1 oocysts/L, 

for example, some PWSs with actual 

mean source-water concentrations 

greater than this level would measure a 

concentration less than this level and 

would be misclassified in the bin that 

requires no additional treatment. 

Consequently, they would not provide 

sufficient public health protection. As 

discussed previously, this type of error 

is due to the limited number and 

volume of samples that can be analyzed, 

imperfect method recovery, and 

variability in Cryptosporidium 

occurrence. 

Based on these considerations, the 

Advisory Committee recommended and 

today’s rule establishes that filtered 

PWSs must provide additional 

treatment for Cryptosporidium when 

their mean source-water concentration 

exceeds 0.075 oocysts/L. At this 

concentration, PWSs collecting monthly 

10-L samples must count at least nine 

oocysts in one year (9 oocysts per 120 

L total sample volume) before additional 

treatment is required. Further, any PWS 

with a mean source-water infectious 

Cryptosporidium level above 0.1 

oocysts/L, which corresponds to an 

estimated infection risk range of 1.7 to 

6.0 × 10¥3, is highly likely to be 

appropriately classified in a bin 

requiring additional treatment. 

After identifying this first threshold 

for requiring additional treatment, 

determining the Cryptosporidium 

concentrations that should bound 

higher treatment bins was necessary. In 

making these determinations, EPA 

concurred with Advisory Committee 

recommendations that sought to balance 

the possibility of bin misclassification 

against equitable risk reduction and 

public health protection. 

Treatment bins that span a wider 

concentration range result in lower bin 

misclassification rates. The analysis 

summarized in section IV.A shows that 

the monitoring required under today’s 

rule can accurately characterize a PWS’s 

mean Cryptosporidium level within a 

0.5-log margin, but error rates increase 

for smaller margins (USEPA 2005a). 

Conversely, treatment bins that span a 

narrower concentration range provide 

more equitable protection from risk 

among different PWSs. This is due to 

identical treatment requirements 

applying to all PWSs in the same bin. 

In consideration of these issues, today’s 

rule establishes two higher treatment 

bins at Cryptosporidium concentrations 

of 1.0 oocysts/L and 3.0 oocysts/L. 

These values result in the four bins 

shown in Table IV.B–1. Available 

occurrence data indicate that few PWSs 

will measure mean Cryptosporidium 

concentrations greater than 3.0 oocysts/ 

L, so there is no need to establish a 

treatment bin above this level. 

With respect to the degree of 

additional Cryptosporidium treatment 

that PWSs in Bins 2–4 must provide, 

EPA and the Advisory Committee 

considered values of 0.5-log and greater. 

Today’s rule establishes a 1-log 

additional treatment requirement for 

conventional plants in Bin 2. Because 


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the concentration range of Bin 2 spans 

approximately one order of magnitude, 

this degree of treatment ensures that 

plants classified in Bin 2 will achieve 

treated water Cryptosporidium levels 

comparable to plants in Bin 1. 

Conventional plants in Bins 3 and 4 

must provide 2.0- and 2.5-log of 

additional treatment, respectively. As 

recommended by the Advisory 

Committee, these higher additional 

treatment levels are required based on 

the recognition that plants in Bins 3 and 

4 have a much greater potential 

vulnerability to Cryptosporidium. 

Consequently, significantly higher 

treatment is appropriate to protect 

public health. 

These additional treatment 

requirements for conventional treatment 

plants in Bins 2–4 are based on a 

prescribed 3-log Cryptosporidium 

treatment credit for compliance with the 

IESWTR or LT1ESWTR, as discussed 

previously. They translate to total 

Cryptosporidium treatment 

requirements of 4.0-, 5.0-, and 5.5-log 

for Bins 2, 3, and 4, respectively. Plants 

receiving higher or lower levels of 

prescribed treatment credit are required 

to provide less or more additional 

treatment if classified in Bins 2–4. 

Plants using slow sand or 

diatomaceous earth filtration, which 

also receive a 3-log treatment credit, 

incur the same additional treatment 

requirements as conventional plants if 

classified in Bins 2–4. Direct filtration 

plants, however, must provide 0.5-log 

greater additional treatment if classified 

in Bins 2–4 because they receive a 2.5- 

log prescribed credit. EPA expects, 

though, that most direct filtration plants 

will be classified in Bin 1 because direct 

filtration is typically applied only to 

higher quality source waters. 

Because EPA is unable to establish a 

prescribed treatment credit for other 

types of filtration technologies like 

membranes, bag filters, and cartridge 

filters, today’s rule requires that States 

assign a treatment credit to a particular 

filtration product. This credit then 

determines the amount of additional 

treatment that a plant using this product 

must provide if classified in Bins 2–4 in 

order to achieve the required total 

treatment level. Section IV.D provides 

criteria for assigning Cryptosporidium 

treatment credit to membranes, bag 

filters, and cartridge filters. 

As described in Section IV.D, today’s 

rule establishes a wide range of 

treatment and control options through 

the microbial toolbox for PWSs to meet 

additional Cryptosporidium treatment 

requirements. PWSs may choose any 

option or combination of options from 

the microbial toolbox to meet the 

treatment requirements of plants in Bin 

2. For plants in Bins 3 or 4, though, 

PWSs must achieve at least 1-log of the 

additional treatment requirement using 

UV, ozone, chlorine dioxide, 

membranes, bag filters, cartridge filters, 

or bank filtration. EPA is establishing 

this provision in today’s rule as 

recommended by the Advisory 

Committee because these processes will 

serve as significant additional treatment 

barriers for PWSs with the highest levels 

of pathogens in their sources. 

How should PWSs calculate their 

treatment bin classification? 

The specific calculations that PWSs 

use to determine their bin classification 

are based on analyses of 

misclassification rates and bias. As 

described in section IV.A, today’s rule 

requires PWSs to collect at least 24 

samples (except for plants that operate 

only part-year) when they monitor for 

Cryptosporidium. Most PWSs will 

collect these 24 samples over two years, 

but PWSs may sample at a higher 

frequency and small PWSs may 

complete this monitoring in one year. 

These differences affect the bin 

classification calculation. 

PWSs that sample monthly over two 

years (24 samples total) must use the 

maximum running annual average 

(Max-RAA) for bin classification 

because this achieves a low false 

negative rate (the likelihood a PWS will 

be incorrectly classified in a lower bin). 

In comparison, if such PWSs used the 

mean of all samples over two years for 

bin classification, the false negative rate 

would be almost four times higher (see 

Table IV.B.4). 

PWSs that choose to sample at least 

twice per month over two years (48 

samples total) must use the mean of all 

48 samples for their bin classification. 

This approach achieves a low false 

negative rate similar to the Max-RAA for 

24 samples and, in addition, reduces the 

false positive rate (the likelihood a PWS 

will be incorrectly classified in higher 

bin—see Table IV.B.4). Due to the lower 

false positive rate associated with 48 

samples, EPA expects that some PWSs 

will choose to sample for 

Cryptosporidium twice per month. 

Small PWSs (serving fewer than 

10,000 people) that complete their 

Cryptosporidium monitoring over one 

year must use the mean of all 24 

samples for bin classification. This 

approach has a higher false negative rate 

than the approaches allowed for PWSs 

that monitor over two years. However, 

it is the only feasible option for PWSs 

that conduct just one year of 

Cryptosporidium sampling. Averaging 

sample concentrations over less than 

one year is not appropriate (except in 

the case of plants that operate only partyear that monitor for less than one year) 

as this would bias the bin classification 

due to seasonal variation in water 

quality. 

TABLE IV.B–4.—FALSE POSITIVE AND

FALSE NEGATIVE RATES FOR MONITORING AND BINNING STRATEGIES

CONSIDERED FOR THE LT2ESWTR 

Strategy False 

positive 1

False 

negative 2

48 sample arithmetic mean ... 1.7% 1.4% 

24 sample MaxRAA ............... 5.3% 1.7% 

24 sample arithmetic mean ... 2.8% 6.2% 

1False positive rates calculated for systems 

with Cryptosporidium concentrations 0.5 log 

below the Bin 1 boundary of 0.075 oocysts/L. 2False negative rates calculated for systems 

with Cryptosporidium concentrations 0.5 log 

above the Bin 1 boundary of 0.075 oocysts/L. 

Two additional considerations that 

relate to characterizing Cryptosporidium 

monitoring results to determine 

treatment requirements are (1) fewer 

than 100 percent of oocysts in a sample 

are recovered and counted by the 

analyst and (2) not all the oocysts 

measured with Methods 1622 or 1623 

are capable of causing infection. These 

two factors are offsetting, in that oocyst 

counts not adjusted for recovery tend to 

underestimate the true concentration, 

while the total oocyst count typically 

overestimates the infectious 

concentration that presents a health 

risk. 

As described in section III, matrix 

spike data indicate that average recovery 

of Cryptosporidium oocysts with 

Methods 1622 or 1623 in a national 

monitoring program will be 

approximately 40 percent. Regarding the 

fraction of oocysts that are infectious, 

LeChevallier et al. (2003) tested natural 

waters for Cryptosporidium using both 

Method 1623 and a method (cell 

culture-PCR) to test for infectivity. 

Results suggested that 37 percent of the 

Cryptosporidium oocysts detected by 

Method 1623 were infectious. This 

finding is consistent with the 

observation that 37 percent of the 

oocysts counted during the ICRSS using 

Methods 1622 or 1623 had internal 

structures, which indicate a higher 

likelihood of infectivity (among the 

remaining oocysts, 47 percent had 

amorphous structures and 16 percent 

were empty). 

While it is not possible to establish a 

precise value for method recovery or the 

fraction of oocysts that are infectious, 


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available data suggest that these 

parameters may be of similar 

magnitude. Consequently, the Advisory 

Committee recommended that 

monitoring results should not be 

adjusted to account for either recovery 

or the fraction infectious. EPA concurs 

with this recommendation and today’s 

rule requires that PWSs be classified in 

treatment bins using the total number of 

Cryptosporidium oocysts counted, 

without further adjustment. The 

LT2ESWTR treatment bins in today’s 

rule are constructed to reflect this 

approach. 

3. Summary of Major Comments 

For filtered PWS treatment 

requirements in the LT2ESWTR 

proposal, EPA received significant 

public comment on the risk-based 

approach to requiring additional 

treatment, the role of States in 

determining bin classification, and the 

treatment credit for filtration plants. The 

following discussion summarizes 

comments in these areas and EPA’s 

responses. 

Most commenters supported the riskbased approach of the LT2ESWTR in 

which filtered PWSs monitor for 

microbial contaminants and only those 

PWSs finding higher levels of 

contamination are required to provide 

additional treatment for 

Cryptosporidium. Among these 

comments, many stated support for the 

four treatment bins for filtered PWSs, 

with some noting that future research 

will indicate whether the bins should be 

restructured in a later rulemaking. 

Several commenters expressed support 

for EPA’s combination of the Stage 2 

DBPR and LT2ESWTR as essential to 

creating a balanced approach between 

DBP control and microbial risk. 

A few commenters opposed the 

expenditure of funds to reduce risk from 

Cryptosporidium on the basis that 

epidemiological evidence suggests this 

risk is low and most communities have 

not experienced cryptosporidiosis 

outbreaks. EPA agrees that additional 

treatment for Cryptosporidium in 

drinking water is not warranted in all 

communities. Under today’s rule, most 

PWSs are expected to be classified in 

the lowest bin, which requires no 

additional treatment. However, based on 

risk information presented in USEPA 

(2005a) and summarized in this 

preamble, EPA believes that additional 

treatment is necessary to protect public 

health in PWSs with the highest 

Cryptosporidium levels. Further, as 

described in USEPA (2005a), EPA’s 

assessment of Cryptosporidium risk in 

drinking water is consistent with the 

limited available epidemiological data 

on disease incidence. 

With respect to the role of States in 

bin classification, most commenters 

recommended that States assign or 

approve the bin classification for their 

PWSs. Commenters maintained that 

State approval of bin classification is an 

inherent governmental function and 

will avoid confusion as to the level of 

treatment each PWS must provide. 

Further, the approval process will 

provide an opportunity for dialog 

between States and PWSs. EPA agrees 

with these comments and today’s rule 

requires PWSs to submit their 

calculation of bin classification to the 

State for review. If the PWS does not 

hear back from the State, it must 

proceed to apply the level of treatment 

appropriate for its calculated bin 

classification in accordance with its 

applicable compliance schedule. 

In regard to the Cryptosporidium 

treatment credit that should be awarded 

to filtration plants, many commenters 

supported the 3-log Cryptosporidium 

removal credit for conventional 

treatment and slow sand filtration. 

Some comments included data showing 

that conventional treatment can achieve 

greater than 4-log removal of 

Cryptosporidium, and several 

commenters stated concerns that EPA 

has underestimated the level of 

treatment achievable through 

conventional treatment. Commenters 

supported the inclusion of plants using 

softening and dissolved air flotation for 

conventional treatment credit and 

requested that EPA extend this credit to 

similar treatment trains using other 

types of clarification processes. 

EPA recognizes that studies show 

conventional treatment can achieve 

more than 3-log Cryptosporidium 

removal under optimal conditions. 

However, studies also demonstrate that 

removal efficiencies can be significantly 

less for suboptimal plant set-up and 

operation. EPA does not expect that all 

plants will operate under optimal 

conditions at all times. Consequently, 

today’s rule awards a prescribed 3-log 

credit to conventional plants complying 

with the IESWTR or LT1ESWTR and 

allows plants to receive higher credit 

through demonstrating low finished 

water turbidity or through an alternative 

demonstration of performance, as 

describe in section IV.D. EPA agrees that 

plants using alternative clarification 

process that involves solids removal 

between coagulation and filtration 

should qualify for 3-log credit and 

today’s rule provides for this. 

C. Unfiltered System Cryptosporidium 

Treatment Requirements 

1. Today’s Rule 

Today’s rule requires all PWSs that 

use a surface water or GWUDI source 

and are unfiltered to provide treatment 

for Cryptosporidium. The degree of 

required treatment depends on the level 

of Cryptosporidium in the source water, 

as determined through required 

monitoring. Further, unfiltered PWSs 

must meet overall treatment 

requirements using at least two 

disinfectants and must continue to meet 

all applicable filtration avoidance 

criteria. Details of these requirements 

follow. 

a. Determination of mean 

Cryptosporidium level. Following 

completion of the required initial source 

water monitoring described in section 

IV.A, each unfiltered PWS must 

determine the arithmetic mean of all its 

Cryptosporidium sample results 

generated during the monitoring period. 

As required for filtered PWSs, 

individual sample results must be 

calculated as the total number of oocysts 

counted, divided by the volume assayed 

(see section V.K for details). Samples are 

not adjusted for method recovery and, 

in samples where no oocysts are 

detected, the result is treated as zero. 

Unfiltered PWSs must report their 

mean Cryptosporidium level to the State 

for approval (see section IV.G for 

specific reporting dates). The report 

must include a summary of the data 

used to determine the mean 

concentration. If the State does not 

respond to a PWS regarding its mean 

Cryptosporidium level, the PWS must 

comply with the Cryptosporidium 

treatment requirements of today’s rule, 

as described next, based on the reported 

level. 

If EPA does not amend today’s rule 

before the second round of monitoring 

described in section IV.A, unfiltered 

PWSs must recalculate their mean 

Cryptosporidium level using results 

from the second round of monitoring. 

Unfiltered PWSs must report this level 

to the State as described for the initial 

round of monitoring. 

b. Cryptosporidium treatment 

requirements. Unfiltered PWSs must 

comply with the following treatment 

requirements based on their mean 

source-water Cryptosporidium level: if 

the level is less than or equal to 0.01 

oocysts/L then at least 2-log 

Cryptosporidium inactivation is 

required; if the level is greater than 0.01 

oocysts/L, or if the unfiltered PWS 

chooses not to monitor for 

Cryptosporidium, then at least 3-log 

Cryptosporidium inactivation is 


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required. See section IV.G for treatment 

compliance dates. 

EPA has developed criteria, described 

in section IV.D, to award 

Cryptosporidium inactivation credit for 

treatment with chlorine dioxide, ozone, 

or UV light. Unfiltered PWSs may use 

any of these disinfectants to meet their 

Cryptosporidium inactivation 

requirements under today’s rule. 

Further, unfiltered PWSs must achieve 

the following with respect to 

disinfection treatment: 

(1) A PWS that uses chlorine dioxide 

or ozone and fails to achieve the 

required level of Cryptosporidium 

inactivation on more than one day in 

the calendar month is in violation of the 

treatment technique requirement. 

(2) A PWS that uses UV light and fails 

to achieve the required level of 

Cryptosporidium inactivation in at least 

95 percent of the water delivered to the 

public every month is in violation of the 

treatment technique requirement. 

c. Use of two disinfectants. Unfiltered 

PWSs must use at least two different 

disinfectants to provide 4-log virus, 3- 

log Giardia lamblia, and 2- or 3-log 

Cryptosporidium inactivation as 

required under 40 CFR 141.72(a) and 

today’s rule. Further, each of two 

disinfectants must achieve by itself the 

total inactivation required for one of 

these target pathogens. This requirement 

does not modify the existing 

requirement under 40 CFR 141.72(a) for 

PWSs to provide a disinfectant residual 

in the distribution system. 

2. Background and Analysis 

The intent of the Cryptosporidium 

treatment requirements for unfiltered 

PWSs in today’s final rule is to ensure 

that they achieve public health 

protection equivalent to that achieved 

by filtered PWSs. These requirements 

are unchanged from the August 11, 2003 

proposal (USEPA 2003a), and they 

reflect consensus recommendations by 

the Stage 2 M–DBP Advisory Committee 

(USEPA 2000a). The following 

discussion summarizes the Agency’s 

basis for establishing risk-targeted 

Cryptosporidium treatment 

requirements for unfiltered PWSs in 

today’s rule and for requiring the use of 

two disinfectants. 

a. Basis for Cryptosporidium 

treatment requirements. As described in 

section III, available data suggest that 

unfiltered PWSs must take additional 

steps to achieve public health protection 

against Cryptosporidium equivalent to 

that provided by filtered PWSs. 

In occurrence data from the ICR, the 

median Cryptosporidium level in 

unfiltered PWS sources was 0.0079 

oocysts/L, which is approximately 10 

times less than the median level of 

0.052 oocysts/L in filtered PWS sources. 

In translating these source water levels 

to finished water concentrations, EPA 

and the Advisory Committee assumed 

that conventional filtration treatment 

plants in compliance with the IESWTR 

or LT1ESWTR achieve an average of 3- 

log (99.9 percent) removal of 

Cryptosporidium. Existing regulations 

do not require unfiltered PWSs to 

provide any treatment for 

Cryptosporidium. 

If the median source water 

Cryptosporidium level in filtered PWSs 

is approximately 10 times higher than in 

unfiltered PWSs, and filtered PWSs 

achieve 3-log Cryptosporidium removal, 

then the median finished water 

Cryptosporidium level in filtered PWSs 

is approximately 100 times lower than 

in unfiltered PWSs. Thus, these data 

suggest that most unfiltered PWSs must 

provide 2-log Cryptosporidium 

treatment to ensure equivalent public 

health protection. 

Some unfiltered PWSs must provide 

greater than 2-log Cryptosporidium 

treatment to ensure equitable protection, 

depending on their source water level. 

Under today’s rule, the 

Cryptosporidium treatment 

requirements for filtered PWSs, as 

described in section IV.B.1, will achieve 

mean finished water Cryptosporidium 

levels of less than 1 oocyst/10,000 L. An 

unfiltered PWS with a mean source 

water Cryptosporidium concentration 

above 0.01 oocysts/L would have to 

provide at least 3-log inactivation to 

achieve an equivalent finished water 

Cryptosporidium level. 

As stated earlier, EPA has determined 

that UV light is a feasible technology for 

PWSs of all sizes, including unfiltered 

PWSs, to inactivate Cryptosporidium. In 

addition, treating for Cryptosporidium 

using ozone is feasible for some 

unfiltered PWSs. Inactivating 

Cryptosporidium with chlorine dioxide, 

while allowed under today’s rule, does 

not appear to be feasible for most 

unfiltered PWSs due to regulatory limits 

on chlorite—a chlorine dioxide 

byproduct. 

Based on these findings, today’s rule 

requires all unfiltered PWSs to provide 

at least 2-log Cryptosporidium 

inactivation, and to provide at least 3- 

log inactivation if the mean source 

water level exceeds 0.01 oocysts/L. 

These treatment requirements will 

ensure that unfiltered PWSs achieve 

public health protection against 

Cryptosporidium that is comparable to 

filtered PWSs in the finished water that 

is distributed to consumers. 

Available data indicate that no 

unfiltered PWSs will show measured 

mean source water Cryptosporidium 

levels of 0.075 oocysts/L or higher—the 

level at which a filtered PWS must 

provide at least 4-log Cryptosporidium 

under today’s rule. Consequently, EPA 

is not establishing treatment 

requirements in today’s rule to address 

Cryptosporidium at this higher level. 

Under existing regulations (40 CFR 

141.171 and 141.521), unfiltered PWSs 

must maintain a watershed control 

program that minimizes the potential for 

contamination by Cryptosporidium 

oocysts in the source water. If the 

measured mean Cryptosporidium level 

in an unfiltered PWS is 0.075 oocysts/ 

L or higher, EPA believes the State 

should critically evaluate the adequacy 

of the watershed control program. 

Under today’s rule, unfiltered PWSs 

using ozone or chlorine dioxide to treat 

for Cryptosporidium must demonstrate 

the required 2- or 3-log inactivation 

every day the PWS serves water to the 

public, except any one day each month. 

Existing regulations (40 CFR 

141.72(a)(1)) require unfiltered PWSs to 

ensure inactivation of 3-log Giardia 

lamblia and 4-log viruses every day 

except any one day per month. 

Consequently, today’s rule extends this 

compliance standard to 

Cryptosporidium inactivation. 

For unfiltered PWSs that use UV to 

treat for Cryptosporidium, today’s rule 

requires demonstration of the required 

2- or 3-log inactivation in at least 95 

percent of the water delivered to the 

public every month. EPA intends this 

standard to be comparable to the ‘‘every 

day except any one day per month’’

standard established for ozone and 

chlorine dioxide. Because UV 

disinfection systems will typically 

consist of multiple reactors that will be 

monitored continuously, EPA believes 

that a compliance standard based on the 

percentage of water disinfected to the 

required level is more appropriate than 

a single daily measurement. Section 

IV.D describes an equivalent standard 

for filtered PWSs. 

b. Basis for requiring the use of two 

disinfectants. Unfiltered PWSs must use 

at least two different disinfectants to 

meet the inactivation requirements for 

Cryptosporidium (2- or 3-log), Giardia 

lamblia (3-log) and viruses (4-log), and 

each of two disinfectants must achieve 

by itself the total inactivation required 

for one of these target pathogens. For 

example, a PWS could use UV light to 

achieve 3-log inactivation of Giardia 

lamblia and Cryptosporidium and use 

chlorine to provide 4-log virus 

inactivation. The use of two 

disinfectants protects public health by 

creating multiple barriers against 

microbial pathogens. This has two 


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general advantages over a single barrier: 

improved reliability and a broader 

spectrum of efficacy. 

Because unfiltered PWSs rely solely 

on inactivation for microbial treatment, 

an unfiltered PWS using only one 

disinfectant would provide no primary 

microbial treatment if that disinfection 

process were to fail. While disinfection 

processes should be designed for a high 

level of reliability, they are not generally 

100 percent reliable. Existing 

regulations and today’s rule recognize 

this limitation by allowing unfiltered 

PWSs to fail to achieve required 

disinfection levels one day per month. 

Consequently, EPA believes that for 

effective public health protection, 

unfiltered PWSs should use at least two 

primary disinfection processes. If one 

process fails, a second process will 

provide some degree of protection 

against pathogens. 

A second advantage of a PWS using 

multiple disinfectants is that this 

approach will typically be more 

effective against a broad spectrum of 

pathogens. The efficacy of different 

disinfectants against different types of 

pathogens varies widely. For example, 

UV light appears to be very effective for 

inactivating protozoa like 

Cryptosporidium and Giardia lamblia, 

but is less effective against certain 

enteric viruses like adenovirus. 

Chlorine, however, is highly effective 

against enteric viruses but less effective 

against protozoa. As a result, multiple 

disinfectants will generally provide 

more effective inactivation of a wide 

range of pathogens than a single 

disinfectant. 

c. Filtration avoidance. Today’s rule 

does not withdraw or modify any 

existing criteria for avoiding filtration 

under 40 CFR 141.71. Accordingly, 

unfiltered PWSs must continue to 

comply with all existing filtration 

avoidance criteria. EPA believes these 

criteria help to ensure that watershed 

protection provides a microbial barrier 

in those PWSs that do not filter. 

Further, today’s rule does not 

establish any new criteria for filtration 

avoidance. In the proposed LT2ESWTR, 

EPA indicated that compliance with 

DBP standards under the Stage 2 DBPR 

would be incorporated into the criteria 

for filtration avoidance. However, EPA 

has not done this in today’s final rule in 

order to give States more flexibility in 

working with unfiltered PWSs to 

comply with the Stage 2 DBPR. 

3. Summary of Major Comments 

EPA received significant public 

comment on the following treatment 

requirements for unfiltered PWSs in the 

LT2ESWTR proposal: the requirement 

for all unfiltered PWSs to provide at 

least 2-log Cryptosporidium 

inactivation, treatment requirements for 

unfiltered PWSs with high 

Cryptosporidium levels, and the 

requirement for unfiltered PWSs to use 

at least two disinfectants. A summary of 

these comments and EPA’s responses 

follows. 

Several commenters supported the 

requirement that all unfiltered PWSs 

achieve at least 2-log inactivation of 

Cryptosporidium, noting that this was 

part of the Agreement in Principle 

(USEPA 2000a). Some commenters, 

however, requested that EPA not 

establish a minimum Cryptosporidium 

treatment level due to the following 

factors: monitoring of unfiltered PWS 

sources has shown very low levels of 

Cryptosporidium, and some sources 

may have no Cryptosporidium; the 

Cryptosporidium in an unfiltered PWS 

source are likely to be of non-human 

origin and are less likely to infect 

humans; and disease incidence data 

have not established a link between 

unfiltered PWSs and cryptosporidiosis 

in consumers. 

In response, EPA continues to believe 

that all unfiltered PWSs should provide 

treatment for Cryptosporidium to 

protect public health. Monitoring has 

shown that unfiltered PWS sources are 

contaminated with Cryptosporidium, 

and no source is likely to be entirely 

free of Cryptosporidium due to the 

ubiquity of Cryptosporidium in both 

human and many animal populations. 

Studies, such as those cited in section 

III, have established that 

Cryptosporidium from animals can 

infect humans. EPA does not regard the 

absence of cryptosporidiosis cases 

attributed to drinking water in a 

particular community as evidence that 

no treatment for Cryptosporidium is 

needed. As described in section III, 

cryptosporidiosis incidence data 

generally do not indicate overall disease 

burden because most cases are 

undetected, unreported, and not traced 

to a particular source. 

Some commenters recommended that 

EPA require only 1-log Cryptosporidium 

inactivation for unfiltered PWSs that 

demonstrate source water levels below 

0.001 oocysts/L. EPA does not support 

this approach, though, due to concerns 

with the reliability of monitoring to 

establish such an extremely low level of 

Cryptosporidium. In addition, UV light 

is a feasible technology for unfiltered 

PWSs of all sizes to achieve at least 2- 

log Cryptosporidium inactivation. For 

these reasons, EPA has concluded that 

the minimum Cryptosporidium 

treatment level should be 2-log, as 

recommended by the Advisory 

Committee. 

In the proposed LT2ESWTR, EPA 

requested comment on the treatment 

that should be required if an unfiltered 

PWS measured a Cryptosporidium level 

of 0.075 oocysts/L or higher—the 

concentration at which a filtered PWS 

must provide at least 4-log treatment. 

Several commenters supported 

equivalent treatment requirements (i.e., 

at least 4-log reduction) for unfiltered 

and filtered PWSs with 

Cryptosporidium at this level. Other 

commenters stated that available data 

indicate no unfiltered PWSs are likely to 

measure Cryptosporidium at such a high 

level. 

EPA agrees that available data on 

Cryptosporidium occurrence suggest 

that no unfiltered PWSs will measure a 

mean level of 0.075 oocysts/L or higher. 

Moreover, establishing a 4-log treatment 

requirement on the precautionary basis 

that an unfiltered PWS might measure a 

high level of Cryptosporidium has a 

significant cost—it would require any 

unfiltered PWS to provide 4-log, rather 

than 3-log, inactivation to avoid 

Cryptosporidium monitoring. EPA 

expects that many small unfiltered 

PWSs will choose to provide 3-log 

Cryptosporidium inactivation rather 

than monitor for Cryptosporidium. 

Accordingly, EPA has concluded that 

establishing a 4-log Cryptosporidium 

treatment requirement for unfiltered 

PWSs that measure a Cryptosporidium 

level of 0.075 oocysts/L or higher is 

unnecessary and inappropriate at this 

time. In the event that an unfiltered 

PWS does measure Cryptosporidium at 

this level, the State can require the PWS 

to take steps to reduce the 

contamination under existing watershed 

control program requirements for 

unfiltered PWSs. 

Some commenters supported the 

requirement for unfiltered PWSs to use 

at least two disinfectants to meet overall 

inactivation requirements for 

Cryptosporidium, Giardia lamblia, and 

viruses and for each disinfectant to 

achieve the total inactivation required 

for one target pathogen. These 

commenters stated that this requirement 

will improve inactivation against a wide 

variety of pathogens and increase 

treatment reliability. Other commenters, 

though, opposed this requirement for a 

number of reasons: it will unnecessarily 

limit the ability of PWSs to minimize 

DBPs, there is no similar requirement 

for filtered PWSs, the requirement for 

each disinfectant to achieve the total 

inactivation for one pathogen goes 

beyond the Agreement in Principle, and 

EPA has not provided a risk analysis to 

justify the requirement. 


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In response, EPA believes that the 

benefits of both redundancy and a broad 

spectrum of microbial protection justify 

requiring the use of two disinfectants. 

Further, requiring each disinfectant to 

achieve the full inactivation of one 

target pathogen establishes a minimal 

performance level so that each 

disinfectant will serve as a substantive 

barrier. In most cases, PWSs will 

comply with this requirement by using 

UV or ozone to inactivate Giardia 

lamblia and Cryptosporidium and using 

chlorine to inactivate viruses. 

D. Options for Systems To Meet 

Cryptosporidium Treatment 

Requirements 

1. Microbial Toolbox Overview 

Today’s rule includes a variety of 

treatment and control options, 

collectively termed the ‘‘microbial 

toolbox,’’ that PWSs can implement to 

comply with additional 

Cryptosporidium treatment 

requirements. Options in the microbial 

toolbox include source protection and 

management programs, prefiltration 

processes, treatment performance 

programs, additional filtration 

components, and inactivation 

technologies. The Stage 2 M–DBP 

Advisory Committee recommended the 

microbial toolbox to provide PWSs with 

broad flexibility in selecting costeffective LT2ESWTR compliance 

strategies. 

Most options in the microbial toolbox 

carry prescribed credits toward 

Cryptosporidium treatment 

requirements. PWSs receive these 

credits by demonstrating compliance 

with required design and operational 

criteria, which are described in the 

sections that follow. In addition, States 

may award treatment credits other than 

the prescribed credit through a 

‘‘demonstration of performance,’’ which 

involves site-specific testing by a PWS 

with a State-approved protocol. Under a 

demonstration of performance, a State 

may award credit to a treatment plant or 

to a unit process of a treatment plant 

that is higher or lower than the 

prescribed credit. This option also 

allows States to award credit to a unit 

process that does not meet the design 

and operational criteria in the microbial 

toolbox for prescribed credit. 

To be eligible for treatment credit for 

a microbial toolbox option, PWSs must 

initially report compliance with design 

criteria, where required, to the State 

(some options do not require design 

criteria). Thereafter, for most options, 

PWSs must report compliance with 

required operational criteria to the State 

each month (the watershed control 

program option requires yearly 

reporting). Failure by a PWS in any 

month to demonstrate treatment credit 

equal to or greater than its 

Cryptosporidium treatment 

requirements under today’s rule is a 

treatment technique violation. This 

violation lasts until the PWS 

demonstrates that it is meeting criteria 

for sufficient treatment credit to satisfy 

its Cryptosporidium treatment 

requirements. 

As described in section IV.B, filtered 

PWSs may use any option or 

combination of options from the 

microbial toolbox to comply with the 

additional Cryptosporidium treatment 

requirements of Bin 2. PWSs in Bins 3 

or 4 must achieve at least 1-log of the 

additional Cryptosporidium treatment 

requirement by using ozone, chlorine 

dioxide, UV, membranes, bag filtration, 

cartridge filtration, or bank filtration. 

If allowed by the State, PWSs may use 

different microbial toolbox options in 

different months to comply with 

Cryptosporidium treatment 

requirements under today’s rule. For 

example, a PWS in Bin 2, which 

requires 1-log additional 

Cryptosporidium treatment, could 

comply with this requirement in one 

month using ‘‘individual filter 

performance,’’ which carries a 1-log 

credit; in a subsequent month, this PWS 

could use ‘‘combined filter 

performance’’ and ‘‘presedimentation 

basin with coagulation,’’ which each 

carry 0.5-log credit. This approach is 

intended to provide greater operational 

flexibility to PWSs. It allows a PWS to 

receive treatment credit for a microbial 

toolbox option in any month the PWS 

is able to meet required operational 

criteria, even if the PWS does not meet 

these criteria during all months of the 

year. 

Table IV.D–1 summarizes prescribed 

treatment credits and associated design 

and operational criteria for microbial 

toolbox options. The sections that 

follow describe each toolbox option in 

detail. In addition, EPA has developed 

three guidance documents to assist 

PWSs with selecting and implementing 

microbial toolbox options: Toolbox 

Guidance Manual, UV Disinfection 

Guidance Manual, and Membrane 

Filtration Guidance Manual. Each may 

be acquired from EPA’s Safe Drinking 

Water Hotline, which can be contacted 

as described under FOR FURTHER

INFORMATION CONTACT at the beginning of 

this notice. 

TABLE IV.D–1.—MICROBIAL TOOLBOX: OPTIONS, CREDITS AND CRITERIA

Toolbox option Cryptosporidium treatment credit with design and operational criteria 1

Source Protection and Management Toolbox Options 

Watershed control program ............ 0.5-log credit for State-approved program comprising required elements, annual program status report to 

State, and regular watershed survey. Unfiltered PWSs are not eligible for credit. 

Alternative source/intake management.No prescribed credit. PWSs may conduct simultaneous monitoring for treatment bin classification at alternative intake locations or under alternative intake management strategies. 

Prefiltration Toolbox Options 

Presedimentation basin with coagulation.0.5-log credit during any month that presedimentation basins achieve a monthly mean reduction of 0.5-log 

or greater in turbidity or alternative State-approved performance criteria. To be eligible, basins must be 

operated continuously with coagulant addition and all plant flow must pass through basins. 

Two-stage lime softening ................ 0.5-log credit for two-stage softening where chemical addition and hardness precipitation occur in both 

stages. All plant flow must pass through both stages. Single-stage softening is credited as equivalent to 

conventional treatment. 

Bank filtration .................................. 0.5-log credit for 25-foot setback; 1.0-log credit for 50-foot setback; horizontal and vertical wells only; aquifer must be unconsolidated sand containing at least 10 percent fines (as defined in rule); average turbidity in wells must be less than 1 NTU. PWSs using existing wells followed by filtration must monitor 

the well effluent to determine bin classification and are not eligible for additional credit. 


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TABLE IV.D–1.—MICROBIAL TOOLBOX: OPTIONS, CREDITS AND CRITERIA—Continued 

Toolbox option Cryptosporidium treatment credit with design and operational criteria 1

Treatment Performance Toolbox Options 

Combined filter performance .......... 0.5-log credit for combined filter effluent turbidity less than or equal to 0.15 NTU in at least 95 percent of 

measurements each month. 

Individual filter performance ............ 0.5-log credit (in addition to 0.5-log combined filter performance credit) if individual filter effluent turbidity is 

less than or equal to 0.15 NTU in at least 95 percent of samples each month in each filter and is never 

greater than 0.3 NTU in two consecutive measurements in any filter. 

Demonstration of performance ....... Credit awarded to unit process or treatment train based on a demonstration to the State with a State-approved protocol. 

Additional Filtration Toolbox Options 

Bag and cartridge filters .................. Up to 2-log credit with demonstration of at least 1-log greater removal in a challenge test when used singly. Up to 2.5-log credit with demonstration of at least 0.5-log greater removal in a challenge test when 

used in series. 

Membrane filtration ......................... Log credit equivalent to removal efficiency demonstrated in challenge test for device if supported by direct 

integrity testing. 

Second stage filtration .................... 0.5-log credit for second separate granular media filtration stage if treatment train includes coagulation 

prior to first filter. 

Slow sand filters .............................. 2.5-log credit as a secondary filtration step; 3.0-log credit as a primary filtration process. No prior 

chlorination. 

Inactivation Toolbox Options 

Chlorine dioxide .............................. Log credit based on measured CT in relation to CT table. 

Ozone .............................................. Log credit based on measured CT in relation to CT table. 

UV ................................................... Log credit based on validated UV dose in relation to UV dose table; reactor validation testing required to 

establish UV dose and associated operating conditions. 

1Table provides summary information only; refer to following preamble and regulatory language for detailed requirements. 

2. Watershed Control Program 

a. Today’s Rule 

Filtered PWSs can receive 0.5-log 

credit toward Cryptosporidium 

treatment requirements under today’s 

rule for implementing a State-approved 

watershed control program designed to 

reduce the level of Cryptosporidium. To 

be eligible to receive this credit initially, 

PWSs must perform the following steps: 

• Notify the State of the intent to 

develop a new or continue an existing 

watershed control program for 

Cryptosporidium treatment credit no 

later than two years prior to the date the 

PWS must comply with additional 

Cryptosporidium treatment 

requirements under today’s rule. 

• Submit a proposed watershed 

control plan to the State for approval no 

later than one year prior to the date the 

PWS must comply with additional 

Cryptosporidium treatment 

requirements under today’s rule. The 

watershed control plan must contain 

these elements: 

(1) The designation of an ‘‘area of 

influence’’ in the watershed, which is 

defined as the area outside of which the 

likelihood of Cryptosporidium 

contamination affecting the treatment 

plant intake is not significant; 

(2) The identification of both potential 

and actual sources of Cryptosporidium 

contamination, including a qualitative 

assessment of the relative impact of 

these contamination sources on water 

quality at the treatment plant intake; 

(3) An analysis of control measures 

that could mitigate the sources of 

Cryptosporidium contamination, 

including the relative effectiveness of 

control measures in reducing 

Cryptosporidium loading to the source 

water and their feasibility; and 

(4) A statement of goals and specific 

actions the PWS will undertake to 

reduce source water Cryptosporidium 

levels, including a description of how 

the actions will contribute to specific 

goals, watershed partners and their 

roles, resource requirements and 

commitments, and a schedule for plan 

implementation. 

If the State approves the watershed 

control plan for Cryptosporidium 

treatment credit, PWSs must perform 

the following steps to be eligible to 

maintain the credit: 

• Submit an annual watershed 

control program status report to the 

State no later than a date specified by 

the State. The status report must 

describe the following: (1) how the PWS 

is implementing the approved 

watershed control plan; (2) the 

adequacy of the plan to meet its goals; 

(3) how the PWS is addressing any 

shortcomings in plan implementation; 

and (4) any significant changes that 

have occurred in the watershed since 

the last watershed sanitary survey. 

• Notify the State prior to making any 

significant changes to the approved 

watershed control plan. If any change is 

likely to reduce the planned level of 

source water protection, the PWS must 

include in this notification a statement 

of actions that will be taken to mitigate 

this effect. 

• Perform a watershed sanitary 

survey no less frequently than the PWS 

must undergo a sanitary survey under 

40 CFR 142.16(b)(3)(i), which is every 

three to five years, and submit the 

survey report to the State for approval. 

The State may require a PWS to perform 

a watershed sanitary survey at an earlier 

date if the State determines that 

significant changes may have occurred 

in the watershed since the previous 

sanitary survey. A person approved by 

the State must conduct the watershed 

sanitary survey and the survey must 

meet applicable State guidelines. The 

watershed sanitary survey must 

encompass the area of influence as 

identified in the State-approved 

watershed control plan, assess the 

implementation of actions to reduce 

source water Cryptosporidium levels, 

and identify any significant new sources 

of Cryptosporidium. 

PWSs are eligible to receive 

Cryptosporidium treatment credit under 

today’s rule for preexisting watershed 

control programs (e.g., programs in 

place at the time of rule promulgation). 


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To be eligible for credit, such programs 

must meet the requirements stated in 

this section and the watershed control 

plan must address future actions that 

will further reduce source water 

Cryptosporidium levels. 

If the State determines that a PWS is 

not implementing the approved 

watershed control plan (i.e., the PWS is 

not carrying out the actions on the 

schedule in the approved plan), the 

State may revoke the Cryptosporidium 

treatment credit for the watershed 

control program. Failure by a PWS to 

demonstrate treatment credit at least 

equal to its Cryptosporidium treatment 

requirement under today’s rule due to 

such a revocation of credit is a treatment 

technique violation. The violation lasts 

until the State determines that the PWS 

is implementing an approved watershed 

control plan or is otherwise achieving 

the required level of Cryptosporidium 

treatment credit. 

PWSs must make the approved 

watershed control plan, annual status 

reports, and watershed sanitary surveys 

available to the public upon request. 

These documents must be in a plain 

language style and include criteria by 

which to evaluate the success of the 

program in achieving plan goals. If 

approved by the State, the PWS may 

withhold portions of these documents 

based on security considerations. 

Unfiltered PWSs are not eligible to 

receive Cryptosporidium treatment 

credit for a watershed control program 

under today’s rule. Under existing 

regulations (40 CFR 141.71), unfiltered 

PWSs must maintain a watershed 

control program that minimizes the 

potential for contamination by 

Cryptosporidium as a condition for 

avoiding filtration. 

b. Background and Analysis 

Cryptosporidium enters drinking 

water through fecal contamination of 

PWS source waters. Implementing a 

watershed control program that reduces 

or treats sources of fecal contamination 

in PWS sources will benefit public 

health by lowering the exposure of 

drinking water consumers to 

Cryptosporidium and other pathogenic 

microorganisms. In addition, a 

watershed control program may 

enhance treatment plant management 

practices through generating knowledge 

of the sources, fate, and transport of 

pathogens. 

The Stage 2 M–DBP Advisory 

Committee recommended 0.5-log 

Cryptosporidium treatment credit for a 

watershed control program (USEPA 

2000a), and the August 11, 2003 

proposal included criteria for PWSs to 

receive this credit (USEPA 2003a). The 

following discussion summarizes the 

basis for this credit and for differences 

in associated requirements between the 

proposal and today’s final rule. 

The efficacy of a watershed control 

program in reducing levels of 

Cryptosporidium and other microbial 

pathogens depends on the ability of a 

PWS to identify and control sources of 

fecal contamination. The fecal sources 

that are significant in a particular 

watershed and the control measures that 

will be effective in mitigating these 

sources are site specific. Consequently, 

EPA believes that States should 

determine whether a watershed control 

program developed by a PWS to reduce 

Cryptosporidium contamination 

warrants 0.5-log treatment credit. 

Accordingly, today’s rule requires State 

approval of watershed control programs 

for PWSs to receive credit. 

If a PWS intends to implement a 

watershed control program to comply 

with Cryptosporidium treatment 

requirements under today’s rule, EPA 

believes the PWS should notify the State 

at least two years prior to the required 

treatment compliance date. This 

notification will give the State an 

opportunity to communicate with the 

PWS regarding site-specific 

considerations for a watershed control 

program. Further, the PWS should 

submit the proposed watershed control 

plan to the State for approval at least 

one year prior to the treatment 

compliance date. This schedule will 

give the State time to evaluate the 

program for approval and, if necessary, 

allow the PWS to make modifications 

necessary for approval. Thus, today’s 

rule establishes these reporting 

deadlines. 

The required elements for a watershed 

control plan in today’s rule are the 

minimum necessary for a program that 

will be effective in reducing levels of 

Cryptosporidium and other pathogens 

in a treatment plant intake. These 

elements include defining the area of 

the watershed where contamination can 

affect the intake water quality, 

identifying sources of contamination 

within this area, evaluating control 

measures to reduce contamination, and 

developing an action plan to implement 

specific control measures. 

EPA encourages PWSs to leverage 

other Federal, State, and local programs 

in developing the elements of their 

watershed control plans. For example, 

SDWA section 1453 requires States to 

carry out a source water assessment 

program (SWAP) for PWSs. Depending 

on how a State implements this 

program, the SWAP may be used to 

define the area of influence in the 

watershed and identify actual and 

potential contamination sources. In 

2002, EPA launched the Watershed 

Initiative (67 FR 36172, May 23, 2002) 

(USEPA 2002b), which will provide 

grants to support watershed-based 

approaches to preventing, reducing, and 

eliminating water pollution. In addition, 

EPA recently promulgated regulations 

for Concentrated Animal Feeding 

Operations that will limit discharges 

that contribute microbial pathogens to 

watersheds. 

Many PWSs do not control the 

watersheds of their sources of supply. 

Their watershed control plans should 

involve partnerships with watershed 

landowners and government agencies 

that have authority over activities in the 

watershed that may contribute 

Cryptosporidium to the water supply. 

Stakeholders that control activities that 

could contribute to Cryptosporidium 

contamination include municipal 

government and private operators of 

wastewater treatment plants, livestock 

farmers and persons who spread 

manure, individuals with failing septic 

systems, logging operations, and other 

government and commercial 

organizations. 

After a State approves a watershed 

control plan for a PWS and initially 

awards 0.5-log Cryptosporidium 

treatment credit, the PWS must submit 

a watershed control program status 

report to the State each year. These 

reports are required for States to 

exercise oversight and ensure that PWSs 

implement the approved watershed 

control plan. They also provide a 

mechanism for PWSs to work with the 

States to address any shortcomings or 

necessary modifications in watershed 

control plans that are identified after 

plan approval. 

In addition, PWSs must undergo 

watershed sanitary surveys every three 

to five years by a State-approved party. 

These surveys will provide information 

to PWSs and States regarding significant 

changes in the watershed that may 

warrant modification of the approved 

watershed control plan. Also, they allow 

for an assessment of watershed control 

plan implementation. 

The proposed rule required watershed 

sanitary surveys annually, but EPA has 

reduced the frequency to every three to 

five years in today’s final rule. This 

frequency is consistent with existing 

requirements for PWS sanitary surveys. 

EPA is establishing this longer 

frequency on the basis that most 

watersheds will not undergo significant 

changes over the course of a single year. 

If significant changes in the watershed 

do occur, however, PWSs must identify 

these changes in their annual program 

status reports. In addition, States have 


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the authority to require that a watershed 

sanitary survey be conducted at an 

earlier date if the State determines that 

significant changes may have occurred 

in the watershed since the previous 

survey. 

In the proposed rule, approval of a 

watershed control program expired after 

a PWS completed the second round of 

source water monitoring, and the PWS 

had to reapply for program approval. 

Today’s final rule, however, does not 

include this requirement. Instead, 

today’s rule gives States authority to 

revoke Cryptosporidium treatment 

credit for a watershed control program 

at any point if a State determines that 

a PWS is not implementing the 

approved watershed control plan. EPA 

believes this approach is preferable to 

the automatic expiration of credit in the 

proposed rule for two reasons: (1) It 

assures PWSs that if they implement the 

approved watershed control plan, they 

will maintain the treatment credit; and 

(2) it gives States the authority to ensure 

PWSs implement watershed control 

programs for which they receive 

treatment credit and to take action at 

any time if a PWS does not. 

EPA believes that PWSs should be 

eligible to receive Cryptosporidium 

treatment credit for watershed control 

programs that are in place prior to the 

treatment compliance date. The same 

requirements for watershed control 

program treatment credit apply 

regardless of whether the program is 

new or existing at the time the PWS 

submits the watershed control plan for 

approval. In the case of existing 

programs, the watershed control plan 

must list future activities the PWS will 

undertake that will reduce source water 

contamination. 

The Toolbox Guidance Manual lists 

programmatic resources and guidance 

available to assist PWSs in building 

partnerships and implementing 

watershed protection activities. It also 

incorporates information on the 

effectiveness of different control 

measures to reduce Cryptosporidium 

levels and provides case studies of 

watershed control programs. This 

guidance is intended to assist both 

PWSs in developing watershed control 

programs and States in assessing and 

approving these programs. 

In addition to this guidance and other 

technical resources, EPA provides 

funding for watershed and source water 

protection through the Drinking Water 

State Revolving Fund (DWSRF) and 

Clean Water State Revolving Fund 

(DWSRF). Under the DWSRF program, 

States may fund source water protection 

activities by PWSs, including watershed 

management and pathogen source 

reduction plans. CWSRF funds can be 

used for agricultural best management 

practices to reduce pathogen loading in 

receiving waters and for the 

replacement of failing septic systems. 

c. Summary of Major Comments 

Public comments on the August 11, 

2003, LT2ESWTR proposal supported 

the concept of awarding credit towards 

Cryptosporidium treatment 

requirements for an effective watershed 

control program. Commenters expressed 

concerns, however, with specific criteria 

for awarding this credit, including 

annual watershed sanitary surveys, reapproval of watershed control programs, 

standards for existing watershed control 

programs, and public availability of 

documents related to the watershed 

control program. A summary of these 

comments and EPA’s responses follows. 

Regarding the proposed requirement 

for annual watershed sanitary surveys, 

commenters stated that this frequency is 

too high because activities to reduce 

Cryptosporidium contamination in the 

watershed will often take many years to 

implement. These commenters 

recommended that watershed sanitary 

surveys be performed every three to five 

years in conjunction with PWSs sanitary 

surveys or longer. In contrast, other 

commenters supported annual 

watershed sanitary surveys as being 

necessary to allow proper responses to 

new sources of contamination that can 

occur quickly in watersheds. Such 

sources can occur through development, 

new recreation programs, fires, 

unauthorized activities, and other 

factors. 

While EPA believes that regular 

watershed sanitary surveys are 

necessary to identify new sources of 

contamination and allow States to 

properly oversee watershed control 

programs, EPA agrees that significant 

changes typically will not occur over 

one year. Therefore, today’s final rule 

requires PWSs that receive 

Cryptosporidium treatment credit for a 

watershed control program to undergo 

watershed sanitary surveys every three 

to five years, rather than every year. To 

address the concern that new sources of 

watershed contamination can arise 

quickly, today’s rule requires PWSs to 

identify any significant changes that 

have occurred in their watersheds in 

their annual program status reports. 

States can then require a watershed 

sanitary survey at an earlier date if 

significant changes have occurred since 

the previous survey. 

Many commenters opposed the 

proposed requirement for PWSs to 

reapply for approval of their watershed 

control programs after completing the 

second round of source water 

monitoring. The concern was that this 

requirement would discourage PWSs 

from pursuing watershed control 

programs because they would be 

uncertain about whether they would 

continue to receive treatment credit for 

their programs in the future. As an 

alternative, commenters recommended 

that States monitor the progress of PWSs 

in implementing watershed control 

programs through the watershed 

sanitary surveys and annual status 

reports. A State could then deny 

treatment credit to a PWS if it failed to 

demonstrate adequate commitment to 

its approved watershed control plan. 

EPA agrees with these comments and 

today’s final rule does not include a 

requirement for re-approval of the 

watershed control program after the 

second round of monitoring. Instead, 

PWSs must submit annual program 

status reports to the State and undergo 

regular watershed sanitary surveys. If 

the State determines that a PWS is not 

implementing its approved watershed 

control plan on the basis of these 

measures, it can withdraw the treatment 

credit associated with the program. 

PWSs that implement their approved 

watershed control plans, however, can 

maintain the associated treatment credit 

indefinitely under today’s rule. 

Several commenters stated that PWSs 

with existing watershed control 

programs should be eligible for 

Cryptosporidium treatment credit under 

the same standards that apply to new 

programs. EPA agrees that both existing 

and new watershed control programs 

should be eligible for Cryptosporidium 

treatment credit under the same 

standards, and today’s rule allows this. 

As is required for new programs, PWSs 

with existing watershed control 

programs must submit a watershed 

control plan that details future activities 

the PWS will implement to reduce 

source water contamination. As with 

new programs, States will have the 

discretion to approve the proposed 

watershed control plan for 0.5-log 

Cryptosporidium treatment credit. 

With respect to a proposed 

requirement that the watershed control 

plan, annual status reports, and 

watershed sanitary surveys be made 

available to the public, commenters 

stated that homeland security concerns 

are associated with these documents. 

Homeland security concerns apply to 

information on the location of treatment 

plant intakes and other structures. EPA 

agrees that there are security concerns 

associated with watershed control 

program documents. EPA also believes, 

though, that the public should be 

allowed to learn about the actions PWSs 


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plan to take to address Cryptosporidium 

contamination and the progress of PWSs 

in implementing these actions. 

Consequently, today’s rule requires 

PWSs to make the approved watershed 

control plan, annual status reports, and 

watershed sanitary surveys available to 

the public. However, PWSs may 

withhold portions of these documents 

that raise security concerns with State 

approval. 

3. Alternative Source 

a. Today’s Rule 

If approved by the State, a PWS may 

determine its Cryptosporidium 

treatment requirements under today’s 

rule using additional source water 

monitoring results for an alternative 

treatment plant intake location or an 

alternative intake operational strategy. 

By meeting the requirements of this 

option, which are described as follows, 

a PWS may reduce its Cryptosporidium 

treatment requirements under today’s 

rule. 

• Monitoring for an alternative intake 

location or operational strategy, termed 

‘‘alternative source monitoring,’’ may 

only be performed in addition to 

monitoring the existing plant intake(s) 

(i.e., the intake(s) the PWS uses when it 

must begin monitoring under today’s 

rule). 

• Alternative source monitoring must 

meet the sample number, sample 

frequency, and data quality 

requirements that apply to source water 

monitoring for bin classification, as 

described in section IV.A. 

• PWSs that perform alternative 

source monitoring must complete this 

monitoring by the applicable deadline 

for treatment bin classification under 

today’s rule, as described in section 

IV.G. Unless a PWS grandfathers 

monitoring data for the existing plant 

intake, alternative source monitoring 

must be performed concurrently with 

monitoring the existing intake. 

• PWSs must submit the results of 

alternative source monitoring to the 

State, along with supporting 

information documenting the location 

and/or operating conditions under 

which the alternative source monitoring 

was conducted. If a PWS fulfills these 

requirements, the PWS may request that 

the State classify the PWS in a treatment 

bin under today’s rule using the 

alternative source monitoring results. 

• If the State approves bin 

classification for a PWS using 

alternative source monitoring results, 

the PWS must relocate the plant intake 

or implement the intake operational 

strategy to reflect the alternative source 

monitoring. The PWS must complete 

these actions no later than the 

applicable date for the PWS to comply 

with Cryptosporidium treatment 

requirements under today’s rule. The 

State may specify reporting 

requirements to verify operational 

practices. 

Failure by a PWS that is classified in 

a treatment bin using alternative source 

monitoring to relocate the intake or 

implement the new intake operational 

strategy, as required, by the applicable 

treatment compliance deadline is a 

treatment technique violation. This 

violation lasts until the State determines 

that the PWS has carried out required 

changes to the intake location or 

operation or is providing the level of 

Cryptosporidium treatment required for 

the existing intake location and 

operation. 

b. Background and Analysis 

Plant intake refers to the works or 

structures at the head of a conduit 

through which water is diverted from a 

source (e.g., river or lake) into a 

treatment plant. Plants may be able to 

reduce influent Cryptosporidium levels 

by changing the intake placement 

(either within the same source or to an 

alternate source) or managing the timing 

or level of withdrawal. 

The Stage 2 M–DBP Advisory 

Committee recommended that PWSs be 

allowed to modify their plant intakes to 

comply with today’s rule, and the 

August 11, 2003 proposal included this 

option (USEPA 2000a). The 

requirements for this option in today’s 

final rule are unchanged from the 

proposal. The following discussion 

summarizes the basis for these 

requirements. 

The effect of changing the location or 

operation of a plant intake on influent 

Cryptosporidium levels can only be 

ascertained through monitoring. 

Consequently, EPA is not establishing a 

prescriptive credit for this option. 

Rather, if a PWS expects that 

Cryptosporidium levels from a current 

plant intake will result in a bin 

classification requiring additional 

treatment under today’s rule, the PWS 

may conduct additional 

Cryptosporidium monitoring reflecting a 

different intake location or operational 

strategy (alternative source monitoring). 

The PWS may then request that the 

State approve bin classification for the 

plant based on alternative source 

monitoring results, provided the PWS 

will implement the corresponding 

changes to the intake location or 

operation. 

PWSs that conduct alternative source 

monitoring must also monitor their 

existing plant intakes. Monitoring the 

existing intake is required for the State 

to determine a treatment bin 

classification for a plant in the event the 

PWS does not modify the intake (to 

reflect alternative source monitoring) 

prior to the treatment compliance 

deadline under today’s rule. 

Further, PWSs must conduct 

alternative source monitoring within the 

applicable time frame for source water 

monitoring under today’s rule. This 

approach is required for the State to 

determine a bin classification for the 

plant based on alternative source 

monitoring by the bin classification 

deadline. In addition, this timing will 

allow the PWS to modify the intake or 

implement additional treatment, if 

necessary, by the treatment compliance 

deadline. This requirement means, 

however, that unless a PWS meets the 

requirement for monitoring its existing 

intake through grandfathering, the PWS 

must perform alternative source 

monitoring concurrently with existing 

intake monitoring, although it does not 

have to be on exactly the same schedule. 

Because alternative source monitoring 

will be used for bin classification, this 

monitoring must comply with all 

applicable requirements for source 

water monitoring that are described in 

section IV.A. Further, the PWS must 

provide the State with supporting 

information documenting the 

conditions, such as the source location, 

under which the alternative source 

monitoring was conducted. This 

documentation is required so that if bin 

classification is based on alternative 

source monitoring results, the State can 

ensure the PWS implements the 

corresponding modifications to the 

intake. 

c. Summary of Major Comments 

Public comments on the August 11, 

2003, LT2ESWTR proposal supported 

allowing PWSs to determine treatment 

bin classification by monitoring for an 

alternative intake location or 

operational strategy. Several 

commenters stated they were unsure if 

this option would be widely used due 

to the burden of performing 

Cryptosporidium monitoring at both the 

current intake and the alternative 

source. Commenters also recommended 

that PWSs first conduct source water 

assessments or watershed sanitary 

surveys to evaluate intake management 

strategies to reduce Cryptosporidium 

levels in the plant influent. 

In response, EPA believes that PWSs 

who choose alternative source 

monitoring must also monitor their 

current intake so that the State can 

determine the appropriate bin 

classification if the PWS does not 


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subsequently modify its intake. While 

few PWSs may choose to pursue 

alternative source monitoring, EPA 

believes this option should be available 

for PWSs that elect to do so. EPA agrees 

that it is appropriate for PWSs to assess 

contamination sources in the watershed 

when considering whether to relocate or 

change the operation of their intakes. 

The Toolbox Guidance Manual provides 

direction to PWSs on conducting these 

assessments. 

EPA requested comment on whether 

representative Cryptosporidium 

monitoring can be performed prior to 

implementation of a new intake strategy 

(e.g., monitoring a new source prior to 

constructing a new intake structure). 

Commenters stated that there may be 

situations where allowing 

Cryptosporidium monitoring to 

demonstrate a reduction in oocyst levels 

prior to implementation of a new intake 

strategy is appropriate. Incurring costs 

for constructing a new intake before 

determining whether the strategy will 

reduce oocyst levels is not cost effective. 

EPA agrees with this comment and 

today’s rule allows PWSs to conduct 

alternative source monitoring prior to 

constructing a new intake and to base 

their bin classification on these 

monitoring results with State approval. 

4. Pre-Sedimentation With Coagulant 

a. Today’s Rule 

Presedimentation is a preliminary 

treatment process used to remove 

gravel, sand and other particulate 

material from the source water through 

settling before the water enters the 

primary clarification and filtration 

processes in a treatment plant. PWSs 

receive 0.5-log credit towards 

Cryptosporidium treatment 

requirements under today’s rule for a 

presedimentation process that meets the 

following conditions: 

• Treats all flow reaching the 

treatment plant; 

• Continuously adds a coagulant to 

the presedimentation basin; 

• Achieves one of the following two 

performance criteria: 

(1) Demonstrates at least 0.5-log mean 

reduction of influent turbidity. This 

reduction must be determined using 

daily turbidity measurements in the 

presedimentation process influent and 

effluent and must be calculated as 

follows: log10 (monthly mean of daily 

influent turbidity)—log10 (monthly 

mean of daily effluent turbidity). 

(2) Complies with State-approved 

performance criteria that demonstrate at 

least 0.5-log mean removal of micronsized particulate material, such as 

aerobic spores, through the 

presedimentation process. 

PWSs may receive treatment credit for 

a presedimentation process during any 

month the process meets these 

conditions. To be eligible for credit, 

PWSs must report compliance with 

these conditions to the State each 

month. PWSs may earn 

presedimentation treatment credit for 

only part of the year if the process does 

not meet these conditions year-round. In 

this situation, PWSs must fully meet 

their Cryptosporidium treatment 

requirements under today’s rule using 

other microbial toolbox options during 

those months when the PWS does not 

receive treatment credit for 

presedimentation. 

Alternatively, PWSs may apply to the 

State for Cryptosporidium treatment 

credit for presedimentation processes 

using a demonstration of performance, 

as described in section IV.D.9. 

Demonstration of performance provides 

an option for PWSs with 

presedimentation processes that do not 

meet these prescribed conditions for 

treatment credit and for PWSs who seek 

greater than 0.5-log Cryptosporidium 

treatment credit for their 

presedimentation processes. 

PWSs are not eligible for 

Cryptosporidium treatment credit for a 

presedimentation process if their 

sampling point for the source water 

Cryptosporidium monitoring used for 

bin classification was after (i.e., 

downstream of) the presedimentation 

process. In this case, the removal 

achieved by the presedimentation 

process will be reflected in the 

monitoring results and bin 

classification. 

b. Background and Analysis 

Presedimentation involves passing 

raw water through retention basins in 

which particulate material is removed 

through settling. PWSs use 

presedimentation to reduce and 

stabilize particle concentrations prior to 

the primary clarification and filtration 

processes in a treatment plant. 

Presedimentation is often operated at 

higher hydraulic overflow rates than 

conventional sedimentation (the 

sedimentation process that directly 

precedes filtration in a conventional 

treatment plant) and may not involve 

coagulant addition. PWSs may operate a 

presedimentation process only during 

periods of high raw water turbidity. 

As a process for removing particles, 

presedimentation can reduce 

Cryptosporidium levels to some degree. 

In addition, presedimentation can 

improve the performance of subsequent 

treatment processes by dampening 

variability in raw water quality. The 

efficacy of presedimentation in 

removing particles, including 

Cryptosporidium, is influenced by the 

use of coagulant, the hydraulic loading 

rate, water quality parameters like 

temperature and turbidity, and physical 

characteristics of the sedimentation 

basin. 

The Stage 2 M–DBP Advisory 

Committee recommended 0.5-log 

Cryptosporidium treatment credit for 

presedimentation with coagulation 

(USEPA 2000a). The August 11, 2003 

proposal included criteria, which were 

similar to those in today’s final rule, for 

PWSs to receive this credit (USEPA 

2003a). The following discussion 

summarizes the basis for this credit and 

for differences in associated 

requirements between the proposal and 

today’s final rule. 

In the proposal, EPA reviewed 

published studies of Cryptosporidium 

removal through conventional 

sedimentation processes by Payment 

and Franco (1993), Kelly et al. (1995), 

Patania et al. (1995), States et al. (1997), 

Edzwald and Kelly (1998), and Dugan et 

al. (2001). These studies included 

bench-, pilot-, and full-scale processes, 

and the reported levels of 

Cryptosporidium removal varied 

widely, ranging from 0.4- to 3.8-log. In 

addition, these studies also supported 

two other significant findings: 

(1) Proper coagulation significantly 

improves Cryptosporidium removal through 

sedimentation. In Dugan et al. (2001), for 

example, average Cryptosporidium removal 

across a sedimentation basin was 1.3-log with 

optimal coagulation and decreased to 0.2-log 

when the coagulant dose was insufficient. 

(2) The removal of aerobic spores correlates 

well with the removal of Cryptosporidium 

when a coagulant is present. This indicates 

that aerobic spores, which are naturally 

present in surface waters, may be used as an 

indicator of Cryptosporidium removal in 

coagulated full-scale sedimentation 

processes. 

Cryptosporidium removal efficiencies 

in conventional sedimentation may be 

higher than in presedimentation due to 

differences in hydraulic loading rates, 

coagulant doses, and other factors. EPA 

identified no published studies of 

Cryptosporidium removal through 

presedimentation processes. In the 

proposal, however, EPA evaluated data 

on the removal of aerobic spores in the 

presedimentation processes of three 

PWSs as an indicator of 

Cryptosporidium removal (USEPA 

2003a). All three PWSs added a 

coagulant (polymer, metal salts, or 

recycled sludge) to the 

presedimentation process. The mean 

removal of aerobic spores through 

presedimentation in the three PWSs 

ranged from 0.5- to 1.1-log over time 


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spans ranging from several months to 

several years. 

These data support the finding that 

full-scale presedimentation processes 

can achieve Cryptosporidium removals 

of 0.5-log and greater under routine 

operating conditions and over an 

extended time period. Accordingly, EPA 

concluded that 0.5-log Cryptosporidium 

treatment credit for presedimentation 

processes is appropriate under certain 

conditions. Today’s rule establishes 

three conditions for PWSs to receive 

this credit. 

The first condition for 

presedimentation to receive 0.5-log 

Cryptosporidium treatment credit is that 

the process must treat all flow reaching 

the treatment plant. Presedimentation 

cannot reduce the Cryptosporidium 

level entering a treatment plant by 0.5- 

log or greater on a continuous basis if 

the process is operated intermittently or 

treats only a fraction of the plant flow. 

EPA recognizes that for some PWSs, 

operating a presedimentation process 

intermittently in response to high 

turbidity levels is preferable to 

continuous operation. By establishing a 

requirement for continuous operation as 

a condition for treatment credit, EPA is 

not recommending against intermittent 

operation of presedimentation 

processes. Rather, EPA is only 

identifying one of the conditions under 

which a 0.5-log Cryptosporidium 

treatment credit for presedimentation 

appears to be justified. 

A second condition for 

presedimentation treatment credit is 

that the process must operate with 

coagulant addition. Available data 

support awarding 0.5-log 

Cryptosporidium treatment credit to a 

presedimentation process only when a 

coagulant is present. The full-scale 

presedimentation data reviewed in the 

proposal involved coagulant addition, 

and literature studies indicate that 

Cryptosporidium removal through 

sedimentation can be substantially 

lower in the absence of sufficient 

coagulant. Further, the Stage 2 M–DBP 

Advisory Committee specifically 

recommended 0.5-log Cryptosporidium 

treatment credit for presedimentation 

with coagulation (USEPA 2000a). Based 

on these factors, EPA concluded that 

coagulation is a necessary condition for 

PWSs to receive treatment credit for 

presedimentation. 

The third condition for awarding 

treatment credit to presedimentation is 

that the process must achieve a monthly 

mean turbidity reduction of at least 0.5- 

log or meet alternative State-approved 

performance criteria. This requirement 

stems from a recommendation by the 

SAB, which reviewed data for awarding 

treatment credit to presedimentation 

under the LT2ESWTR. In their report, 

the SAB concluded that available data 

were minimal to support 0.5-log 

prescribed credit for presedimentation 

and recommended that performance 

criteria other than overflow rate be 

included if credit is given for 

presedimentation (SAB 2003). 

In response to this recommendation 

by the SAB, EPA analyzed the 

relationship between removal of aerobic 

spores (as an indicator of 

Cryptosporidium removal) and 

reduction in turbidity in the full-scale 

presedimentation processes of three 

PWSs. The results of this analysis, 

which are shown in Table IV.D–2, 

suggest that presedimentation processes 

achieving a monthly mean reduction in 

turbidity of at least 0.5-log have a high 

likelihood of reducing mean 

Cryptosporidium levels by 0.5-log or 

more. Consequently, EPA concluded 

that turbidity reduction is an 

appropriate performance criterion for 

awarding Cryptosporidium treatment 

credit to presedimentation basins. The 

Agency believes this performance 

criterion addresses the concern raised 

by the SAB. 

TABLE IV.D–2.—RELATIONSHIP BETWEEN MEAN TURBIDITY REDUCTION

AND THE PERCENT OF MONTHS

WHEN MEAN SPORE REMOVAL WAS

AT LEAST 0.5 LOG

Log reduction in turbidity 

(monthly mean) 

Percent of 

months with at 

least 0.5 Log 

Mean Reduction in spores 

(percent) 

at least 0.1-log ...................... 64 

at least 0.2-log ...................... 68 

at least 0.3-log ...................... 73 

at least 0.4-log ...................... 78 

at least 0.5-log ...................... 89 

at least 0.6-log ...................... 91 

at least 0.7-log ...................... 90 

at least 0.8-log ...................... 89 

at least 0.9-log ...................... 95 

at least 1.0-log ...................... 96 

Source: Data from Cincinnati Water Works, 

Kansas City Water Services Department, and 

St. Louis Water Division. 

The proposed rule required PWSs to 

achieve at least 0.5-log turbidity 

reduction through presedimentation in 

at least 11 of the 12 previous 

consecutive months to be eligible for 

presedimentation treatment credit. EPA 

recognizes, however, that some PWSs 

will not be able to demonstrate at least 

0.5-log turbidity reduction through 

presedimentation during months when 

raw water turbidity is lower. As a result, 

these PWSs would not be able to 

achieve treatment credit for their 

presedimentation basins. To provide 

more options for these PWSs, EPA has 

modified this requirement in today’s 

final rule in two respects. 

The first modification is that in 

today’s final rule, PWSs must 

demonstrate compliance with the 

conditions for presedimentation 

treatment credit on a monthly, rather 

that a yearly basis. This requirement 

allows treatment credit for 

presedimentation in any month a PWS 

can demonstrate at least 0.5-log 

turbidity reduction, even if the PWS 

cannot achieve this level of turbidity 

reduction in all months of the year. 

A PWS that meets the conditions for 

presedimentation treatment credit for 

only part of the year must implement 

other microbial toolbox options to 

comply with Cryptosporidium treatment 

requirements in the remainder of the 

year. Nevertheless, achieving 

presedimentation treatment credit for 

even part of the year may benefit certain 

PWSs. For example, a PWS may be able 

to reduce the level of disinfection it 

provides during the months it receives 

presedimentation treatment credit, or 

this treatment credit may provide a 

margin of safety to ensure compliance 

with Cryptosporidium treatment 

requirements. 

The second modification is the 

allowance for States to approve 

alternative performance criteria to 

turbidity reduction that demonstrate at 

least 0.5-log mean removal of micronsized particulate material through the 

presedimentation process. EPA believes 

that aerobic spores are an appropriate 

alternative criterion. As described 

earlier, studies support the use of 

aerobic spores as an indicator of 

Cryptosporidium removal in coagulated 

sedimentation processes. If approved by 

the State, a PWS could receive 0.5-log 

treatment credit for presedimentation by 

demonstrating at least 0.5-log reduction 

in aerobic spores. The Toolbox 

Guidance Manual provides information 

on analytical methods for measuring 

aerobic spores. This may provide an 

option for PWSs that are not able to 

demonstrate 0.5-log turbidity reduction 

but have a sufficient concentration of 

aerobic spores in their raw water. PWSs 

may work with States to identify other 

alternative criteria, as well as 

appropriate monitoring to support use 

of the criteria. 

c. Summary of Major Comments 

Public comments on the August 11, 

2003, LT2ESWTR proposal supported 

allowing PWSs to achieve 0.5-log credit 

towards Cryptosporidium treatment 

requirements for presedimentation with 


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coagulation. Some commenters also 

supported the proposed operational, 

monitoring, and performance conditions 

required for PWSs to receive this credit. 

Other commenters, however, opposed 

the proposed requirement for turbidity 

reduction as a condition for receiving 

presedimentation treatment credit. A 

summary of these commenters’ concerns 

and EPA’s responses follows. 

Commenters who opposed requiring 

turbidity reduction for presedimentation 

treatment credit were concerned that 

PWSs cannot achieve this criterion 

during periods when raw water 

turbidity is low. Further, these 

commenters stated that turbidity 

removal does not reflect the overall 

benefits of presedimentation, which 

improves the performance of the 

primary treatment train by equalizing 

water quality. Some commenters also 

provided data showing the reduction in 

turbidity and aerobic spore levels in the 

presedimentation processes of several 

PWSs and stated that turbidity removal 

may not be an appropriate indicator of 

acceptable performance for 

presedimentation basins. Several 

commenters suggested that EPA 

establish a limit on hydraulic overflow 

rate in place of a turbidity removal 

requirement. 

In response, EPA continues to 

believes that 0.5-log turbidity reduction 

is an appropriate performance indicator 

for 0.5-log Cryptosporidium reduction 

in presedimentation processes. EPA has 

reviewed the additional data submitted 

by commenters on the removal of 

turbidity and aerobic spores (as an 

indicator of Cryptosporidium removal) 

in full-scale presedimentation basins. 

These data are consistent with data 

reviewed for the proposal in showing 

that when turbidity removal was below 

0.5-log, removal of aerobic spores was 

also usually below 0.5-log. Conversely, 

when turbidity reduction exceeded 0.5- 

log, aerobic spore removal was typically 

higher than 0.5-log. Consequently, while 

there is not a one-to-one relationship 

between reduction in turbidity and 

reduction in aerobic spores, 0.5-log 

turbidity reduction is a reasonable 

indicator of when Cryptosporidium 

removal is likely to be at least 0.5-log. 

EPA recognizes, though, that 0.5-log 

turbidity reduction through 

presedimentation will not be feasible for 

some PWSs when raw water turbidity is 

low. Today’s final rule contains several 

provisions to address this concern. First, 

PWSs can receive credit for 

presedimentation during any month the 

process achieves 0.5-log turbidity 

removal. Thus, PWSs that cannot 

achieve 0.5-log turbidity reduction yearround may receive credit for 

presedimentation in those months when 

they can meet this condition. Today’s 

rule also allows PWSs to receive 

presedimentation credit using Stateapproved performance criteria other 

than turbidity reduction. If approved by 

the State, a PWS may receive credit for 

presedimentation by demonstrating, for 

example, 0.5-log reduction in aerobic 

spores. Finally, if presedimentation 

improves treatment plant performance 

by reducing and equalizing particle 

loading, a PWS can receive additional 

treatment credit under today’s rule for 

achieving lower filtered water turbidity 

(see section IV.D.7). 

5. Two-Stage Lime Softening 

a. Today’s Rule 

Lime softening in drinking water 

treatment involves the addition of lime 

and other chemicals to remove hardness 

(calcium and magnesium) through 

precipitation. In single-stage softening, 

chemical addition and hardness 

precipitation occur in a single 

clarification process prior to filtration. 

In two-stage softening, chemical 

addition and hardness precipitation 

occur in each of two sequential 

clarification processes prior to filtration. 

In some water treatment plants, a 

portion of the raw water bypasses a 

softening process (i.e., split softening) in 

order to achieve a desired pH and 

alkalinity level in the treated water. 

Under today’s rule, single-stage 

softening with filtration receives a 

prescribed 3.0-log credit towards 

Cryptosporidium treatment 

requirements, which is equivalent to 

conventional treatment (see section 

IV.B). Two-stage softening receives an 

additional 0.5-log Cryptosporidium 

treatment credit during any month a 

PWS meets the following conditions: 

(1) Chemical addition and hardness 

precipitation occur in two separate and 

sequential softening stages prior to filtration; 

and 

(2) Both softening stages treat the entire 

plant flow taken from surface water sources 

or GWUDI (i.e., no portion of the plant flow 

from a surface water source may bypass 

either softening stage). 

Alternatively, PWSs may apply to the 

State for Cryptosporidium treatment 

credit for softening processes using a 

demonstration of performance, as 

described in section IV.D.9. 

Demonstration of performance provides 

an option for PWSs with softening 

processes that do not meet these 

conditions for prescribed treatment 

credit and for PWSs who seek greater 

than the prescribed Cryptosporidium 

treatment credit for their softening 

processes. 

b. Background and Analysis 

Lime softening is a common practice 

that PWSs use to reduce water hardness, 

which is primarily calcium and 

magnesium. The addition of lime 

elevates the pH of the raw water. 

Elevation to pH 9.4 or higher causes 

precipitation of calcium carbonate and 

further elevation to pH 10.6 or higher 

causes precipitation of magnesium 

hydroxide. Soda ash may be added with 

lime to precipitate non-carbonate 

hardness. Removal of the precipitate 

occurs through clarification (e.g., 

sedimentation basin) and filtration 

processes. Coagulants and recycled 

softening sludge are often used to 

enhance removal. In two-stage 

softening, the second stage is commonly 

used to precipitate magnesium, along 

with increased levels of calcium. 

In addition to reducing hardness, 

softening processes remove particulate 

material present in the raw water, 

including microbial pathogens like 

Cryptosporidium. Particulate material 

flocculates with the softening 

precipitate and is removed through the 

clarification and filtration processes, 

similar to a conventional treatment 

plant. The degree of Cryptosporidium 

removal will depend on the amount of 

precipitate formation, the use of 

coagulants, the raw water quality, and 

other factors. Available data indicate 

that the elevated pH used in softening 

does not inactivate Cryptosporidium or 

Giardia (Logsdon et al. 1994, Li et al. 

2001), though it does inactivate some 

microorganisms like viruses (Battigelli 

and Sobsey, 1993, Logsdon et al. 1994). 

The Stage 2 M–DBP Advisory 

Committee recommended that lime 

softening be eligible for up to 1.0-log 

additional Cryptosporidium treatment 

credit based on a site-specific 

demonstration of performance, but did 

not recommend any prescribed credit 

for this process (USEPA 2000a). After 

reviewing available data, however, EPA 

included a prescribed 0.5-log 

Cryptosporidium treatment credit for 

two-stage lime softening in the August 

11, 2003 proposal (USEPA 2003a). This 

approach reflected a recommendation 

by the SAB, which supported an 

additional 0.5-log treatment credit for 

two-stage lime softening if all the water 

passes through both stages (SAB 2003). 

The proposal also allowed for greater 

treatment credit through a 

demonstration of performance. The 

following discussion summarizes the 

basis for the lime softening treatment 

credit in today’s final rule and 

differences with the proposal. 

In the proposal, EPA reviewed a study 

by Logsdon et al. (1994) that evaluated 


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Cryptosporidium removal in full-scale 

lime softening plants. Cryptosporidium 

was detected in the raw water at 5 

plants: one single-stage plant and four 

two-stage plants. Based on measured 

levels, the removal of Cryptosporidium 

across the softening clarification 

(sedimentation) stages was 1.0-log in the 

single stage plant and ranged from 1.1- 

to 2.3-log in the two-stage plants. 

Cryptosporidium reductions from raw to 

filtered water were 0.6- and 2.2-log in 

the single stage plant and ranged from 

greater than 2.67- to greater than 3.85- 

log in the two-stage plants. 

EPA also evaluated data collected by 

PWSs on the removal of aerobic spores 

in full-scale lime softening plants. As 

discussed earlier, studies have shown 

the removal of aerobic spores to be an 

indicator for Cryptosporidium removal, 

and one pilot-scale study of a softening 

plant found significantly greater 

removal of Cryptosporidium than 

aerobic spores under similar treatment 

conditions (Clark et al., 2001). For the 

full-scale plants, average reductions in 

aerobic spores across the softening 

clarification stages were 2.4- and 2.8-log 

for two plants that practice two-stage 

softening and were 1.6- and 2.4-log for 

two plants that practice single-stage 

softening (USEPA 2003a). 

The Cryptosporidium removal data 

from Logsdon et al. (1994) and the 

aerobic spore removal data provided by 

PWSs indicate that a lime softening 

clarification stage can achieve greater 

than 0.5-log Cryptosporidium removal 

during routine operation. Consequently, 

EPA agrees with the SAB 

recommendation to award an additional 

0.5-log Cryptosporidium treatment 

credit for two-stage softening. Today’s 

rule establishes two-conditions for 

PWSs to receive this credit. 

The first condition for 0.5-log 

treatment credit for two-stage softening 

is that chemical addition and hardness 

precipitation must occur in two separate 

and sequential softening stages prior to 

filtration. The purpose of this condition 

is to ensure that plants receiving 

additional credit for two-stage softening 

actually have softening and associated 

particle removal occurring in each of 

two sequential clarification stages. 

Plants with other types of clarification 

processes in series with a softening 

stage are not eligible for two-stage 

softening credit. Such plants may, 

however, be eligible for additional 

treatment credit for other microbial 

toolbox options, such as 

presedimentation, or may achieve 

additional credit through a 

demonstration of performance. 

The second condition for two-stage 

softening treatment credit is that both 

softening stages must treat the entire 

plant flow taken from a surface water 

source or GWUDI. The SAB 

recommended this condition, which 

reflects the understanding that a 

softening stage is unlikely to reduce 

overall Cryptosporidium levels by 0.5- 

log or more if it treats only a fraction of 

the plant flow. 

EPA recognizes that some PWSs using 

softening will bypass a softening stage 

in order to maintain a desired pH and 

alkalinity level in the treated water, and 

EPA is not recommending against this 

practice generally. Rather, the 

restriction on bypassing a softening 

stage in today’s rule applies only to 

PWSs that seek additional treatment 

credit for softening. Additionally, plants 

that soften both surface water and 

ground water are eligible for softening 

treatment credit if they bypass a 

softening stage only with ground water 

that is not under the direct influence of 

surface water. 

The proposal also required that a 

coagulant be present in both clarifiers 

for a PWS to be eligible for additional 

treatment credit for two-stage softening. 

EPA is not establishing this requirement 

in today’s final rule. While many PWSs 

that practice softening add coagulants to 

improve the removal of precipitates and 

other particles, the SAB did not 

recommend coagulant addition as a 

condition for receiving treatment credit. 

Further, available data do not indicate 

that additional coagulant is necessary to 

achieve at least 0.5-log Cryptosporidium 

removal across a softening clarification 

stage if hardness precipitation is 

occurring. 

c. Summary of Major Comments 

Public comments on the August 11, 

2003, LT2ESWTR proposal supported 

awarding additional Cryptosporidium 

treatment credit for lime softening 

processes. EPA received specific 

comments on the types of lime softening 

processes eligible for additional 

treatment credit, the amount of 

additional treatment credit awarded, 

and the need for a coagulant. A 

summary of these commenters’ concerns 

and EPA’s responses follows. 

In regard to the types of lime 

softening processes eligible for 

treatment credit, commenters 

recommended that EPA better define 

two-stage softening. Commenters stated 

that two-stage softening involves two 

separate reaction chambers with the 

addition of the softening chemical at the 

beginning of each chamber. Some 

commenters recommended that 

eligibility for additional treatment credit 

should be based on the level of 

softening precipitate formed or the 

settled water turbidity and not on 

whether a plant practices single- or twostage softening. Another commenter 

recommended that any plant designs 

with multiple, continuously operated 

clarification processes in series should 

be eligible for additional treatment 

credit. 

In response, EPA has refined the 

definition of two-stage softening in 

today’s final rule, which requires that 

softening processes employ chemical 

addition and hardness precipitation in 

two sequential stages to be eligible for 

the prescribed additional treatment 

credit. EPA agrees with commenters that 

the level of precipitate formation will 

influence the degree of Cryptosporidium 

removal. Available data, however, 

indicate that two-stage softening will 

generally achieve more 

Cryptosporidium removal than singlestage softening. Consequently, EPA 

believes that two-stage softening should 

be eligible for the additional prescribed 

0.5-log treatment credit. Plants with 

single-stage softening may receive 

additional treatment credit under 

today’s rule through a demonstration of 

performance. Similarly, plants that 

employ multiple clarification process 

other than softening in series may 

receive additional treatment credit 

either as presedimentation or through a 

demonstration of performance. 

With respect to the amount of 

additional Cryptosporidium treatment 

credit for two-stage softening, most 

commenters supported awarding 3.0-log 

treatment credit to single-stage lime 

softening, equivalent to a conventional 

treatment plant, and an additional 

prescribed 0.5-log treatment credit for 

two-stage lime softening. A few 

commenters requested that two-stage 

lime be granted an additional 

Cryptosporidium treatment credit of 1.0- 

log, based on the level of aerobic spore 

removal measured across softening 

clarifiers. 

EPA agrees with most commenters 

and the SAB that 0.5-log is an 

appropriate level of additional 

prescribed Cryptosporidium treatment 

credit for two-stage softening. Where 

plants are able to demonstrate a 

significantly higher level of removal of 

Cryptosporidium or an indicator like 

aerobic spores, they may apply for 

additional treatment credit through a 

demonstration of performance. 

Commenters stated that achieving 

particle removal in lime softening is not 

dependent on a coagulant like a metal 

salt or organic polymer. Some 

commenters recommended that 

coagulant be defined to include 

softening chemicals like lime and 

magnesium hydroxide (a softening 


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precipitate). EPA agrees that available 

data do not demonstrate the need for a 

traditional metal salt or organic 

coagulant for effective particle removal 

in softening. Accordingly, today’s final 

rule does not require the use of a 

coagulant as a condition for additional 

treatment credit in two-stage softening. 

Instead, each stage must involve 

chemical addition and hardness 

precipitation. EPA intends this 

requirement to ensure that softening and 

associated particle removal occur in 

each stage if a plant is to receive 

additional treatment credit for two-stage 

softening. 

6. Bank Filtration 

a. Today’s Rule 

Bank filtration is a water treatment 

process that uses one or more pumping 

wells to induce or enhance natural 

surface water infiltration and to recover 

that surface water from the subsurface 

after passage through a river bed or 

bank(s). Under today’s rule, bank 

filtration that serves as pretreatment to 

a filtration plant is eligible for 

Cryptosporidium treatment credit if it 

meets the following criteria: 

• Wells with a ground water flow 

path of at least 25 feet receive 0.5-log 

treatment credit; wells with a ground 

water flow path of at least 50 feet 

receive 1.0-log treatment credit. The 

ground water flow path must be 

determined as specified in this section. 

• Only wells in granular aquifers are 

eligible for treatment credit. Granular 

aquifers are those comprised of sand, 

clay, silt, rock fragments, pebbles or 

larger particles, and minor cement. A 

system must characterize the aquifer at 

the well site to determine aquifer 

properties. Systems must extract a core 

from the aquifer and demonstrate that in 

at least 90 percent of the core length, 

grains less than 1.0 mm in diameter 

constitute at least 10 percent of the core 

material. 

• Only horizontal and vertical wells 

are eligible for treatment credit. 

• For vertical wells, the ground water 

flow path is the measured distance from 

the edge of the surface water body under 

high flow conditions (determined by the 

100 year floodplain elevation boundary 

or by the floodway, as defined in 

Federal Emergency Management Agency 

flood hazard maps) to the well screen. 

For horizontal wells, the ground water 

flow path is the measured distance from 

the bed of the river under normal flow 

conditions to the closest horizontal well 

lateral screen. 

• Systems must monitor each 

wellhead for turbidity at least once 

every four hours while the bank 

filtration process is in operation. If 

monthly average turbidity levels, based 

on daily maximum values in the well, 

exceed 1 NTU, the system must report 

this result to the State and conduct an 

assessment within 30 days to determine 

the cause of the high turbidity levels in 

the well. If the State determines that 

microbial removal has been 

compromised, the State may revoke 

treatment credit until the system 

implements corrective actions approved 

by the State to remediate the problem. 

• Springs and infiltration galleries are 

not eligible for treatment credit under 

this section, but are eligible for credit 

under the demonstration of performance 

provisions described in section IV.D.9. 

Alternatively, PWSs may apply to the 

State for Cryptosporidium treatment 

credit for bank filtration using a 

demonstration of performance. States 

may award greater than 1.0-log 

Cryptosporidium treatment credit for 

bank filtration based on a site-specific 

demonstration. For a bank filtration 

demonstration of performance study, 

today’s rule establishes the following 

criteria: 

• The study must follow a Stateapproved protocol and must involve the 

collection of data on the removal of 

Cryptosporidium or a surrogate for 

Cryptosporidium and related 

hydrogeologic and water quality 

parameters during the full range of 

operating conditions. 

• The study must include sampling 

both from the production well(s) and 

from monitoring wells that are screened 

and located along the shortest flow path 

between the surface water source and 

the production well(s). 

The Toolbox Guidance Manual provides 

guidance on conducting site-specific 

bank filtration studies, including 

analytical methods for measuring 

aerobic and anaerobic spores, which 

may serve as surrogates for 

Cryptosporidium removal. 

PWSs using existing bank filtration as 

pretreatment to a filtration plant at the 

time the PWS must begin source water 

Cryptosporidium monitoring under 

today’s rule must sample the well for 

the purpose of determining bin 

classification. These PWSs are not 

eligible to receive additional treatment 

credit for bank filtration. In these cases, 

the performance of the bank filtration 

process in reducing Cryptosporidium 

levels will be reflected in the 

monitoring results and bin 

classification. 

PWSs using bank filtration without 

additional filtration must collect source 

water samples in the surface water (i.e., 

prior to bank filtration) to determine bin 

classification unless the State approves 

an alternative monitoring location. This 

applies to systems using bank filtration 

to meet the Cryptosporidium removal 

requirements of the IESWTR or 

LT1ESWTR under the provisions for 

alternative filtration demonstration in 

40 CFR 141.173(b) or 141.552(a). Bank 

filtration criteria for Cryptosporidium 

removal credit under today’s rule do not 

apply to existing State actions regarding 

alternative filtration Cryptosporidium 

removal credit for IESWTR or 

LT1ESWTR compliance. PWSs using 

GWUDI sources must collect samples 

from the well (i.e., the ground water). 

b. Background and Analysis 

Bank filtration is a water treatment 

process that makes use of surface water 

that has naturally infiltrated into ground 

water through a river bed or bank and 

is recovered via a pumping well. River 

bed infiltration is typically enhanced by 

the pumping action of nearby wells. 

Bank filtrate is water that is drawn into 

a pumping well from a nearby surface 

water source after having traveled 

through the subsurface (i.e., aquifer) and 

mixing with other ground water. In bank 

filtration, microorganisms and other 

particles are removed by contact with 

the aquifer materials. 

The Stage 2 M–DBP Advisory 

Committee recommended a prescribed 

Cryptosporidium treatment credit of 1.0- 

log for bank filtration with the option 

for PWSs to receive greater treatment 

credit through a site-specific 

demonstration of performance (USEPA 

2000a). The August 11, 2003 proposal 

included criteria, similar to those in 

today’s final rule, for PWSs to receive 

prescribed treatment credits of 0.5- and 

1.0-log (USEPA 2000a). The following 

discussion summarizes the basis for 

these credits and for differences in 

associated requirements between the 

proposal and today’s final rule. 

Directly measuring the removal of 

Cryptosporidium through bank filtration 

is difficult due to the relatively low 

oocyst concentrations typically present 

in surface and ground water. In the 

proposal, EPA reviewed bank filtration 

field studies that measured the removal 

of Cryptosporidium surrogates, 

specifically aerobic and anaerobic 

bacterial endospores (Havelaar et al. 

1995, Rice et al. 1996, Pang et al. 1998, 

Arora et al. 2000, Medema et al. 2000, 

and Wang et al. 2001). These 

microorganisms are suitable surrogates 

because they are resistant to inactivation 

in the subsurface, similar in size and 

shape to Cryptosporidium, and present 

in both surface and ground water at 

concentrations that allow calculation of 

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ground water interface and within the 

aquifer. In addition, EPA reviewed 

studies of the transport of 

Cryptosporidium through soil materials 

in laboratory column studies (Harter et 

al. 2000). 

Based on these studies, EPA 

concluded that bank filtration processes 

can achieve significant Cryptosporidium 

removal and that prescribed 

Cryptosporidium treatment credits of 

0.5-log and 1.0-log are appropriate 

under certain conditions. These 

conditions are as follows: Only wells 

located in unconsolidated, 

predominantly sandy aquifers are 

eligible 

The bank filtration removal process 

performs most efficiently when the 

aquifer is comprised of granular 

materials with open pore-space for 

water flow around the grains. In these 

granular porous aquifers, the flow path 

is meandering, thereby providing ample 

opportunity for microorganisms to come 

into contact with and attach to a grain 

surface. Accordingly, only wells located 

in unconsolidated, granular aquifers are 

eligible for bank filtration treatment 

credit. 

Granular aquifers are those comprised 

of sand, clay, silt, rock fragments, 

pebbles or larger particles and minor 

cement. Specifically, a PWS must 

extract a core from the aquifer and 

demonstrate that in at least 90 percent 

of the core length, grains less than 1.0 

mm in diameter constitute at least 10 

percent of the core material. Laboratory 

column studies of Cryptosporidium 

transport (Harter et al., 2000) and field 

studies of aerobic bacterial endospore 

passage in the subsurface (Pang et al., 

1998) support these criteria. 

Only Horizontal and Vertical Wells Are 

Eligible 

A number of devices are used for the 

collection of ground water including 

horizontal and vertical wells, spring 

boxes, and infiltration galleries. Among 

these, only horizontal and vertical wells 

are eligible for log removal credit 

because spring boxes and infiltration 

galleries are components of engineered 

systems designed to speed transport 

through or by-pass the naturally 

protective riverbed or bank. 

Wells Must be Located 25 Feet From the 

Surface Water Source To Be Eligible for 

0.5-Log Credit and Located at Least 50 

Feet From the Surface Water Source To 

Be Eligible for 1.0-Log Credit 

A vertical or horizontal well located 

adjacent to a surface water body is 

eligible for bank filtration credit if there 

is sufficient ground water flow path 

length to effectively remove oocysts. 

Specifically, the ground water flow path 

must be at least 25 feet and 50 feet for 

0.5-log and 1.0-log Cryptosporidium 

treatment credit, respectively. The 

ground water flow path to a vertical 

well is the measured distance from the 

edge of the surface water body under 

high flow conditions (determined by the 

100 year floodplain elevation boundary 

or floodway, as defined in Federal 

Emergency Management Agency flood 

hazard maps) to the wellhead. The 

ground water flow path to a horizontal 

well is the measured distance from the 

bed of the river under normal flow 

conditions to the closest horizontal well 

lateral. 

These required flow path distances for 

Cryptosporidium treatment credit are 

based on pathogen and surrogate 

monitoring data from bank filtration 

field studies (Wang et al. 2001, Havelaar 

et al. 1995, Medema et al. 2000). Results 

from these studies show that significant 

removal of anaerobic and aerobic spores 

can occur during passage across the 

surface water—ground water interface, 

with lesser removal occurring during 

ground water transport within the 

aquifer away from that interface. The 

ground water—surface water interface is 

usually comprised of finer grained 

material that lines the bottom of the 

riverbed. Typically, the thickness of the 

interface is small, ranging from a few 

inches to a foot. 

These results suggest that during 

normal and low surface water 

elevations, the surface water-ground 

water interface will perform effectively 

to remove microbial contamination like 

Cryptosporidium. During short periods 

of flooding, substantially lower removal 

rates may occur due to scouring of the 

riverbed and removal of the protective, 

fine-grained material. Assessing the 

mean Cryptosporidium removal that a 

bank filtration process will achieve over 

the period of a year requires 

consideration of both high and low 

removal periods. By considering all time 

intervals with differing removal rates 

over the period of a year, EPA 

concluded that 0.5-log removal over 25 

feet and 1.0-log removal over 50 feet are 

appropriate estimates of the mean 

performance of a bank filtration process 

(USEPA 2003a). 

Wells Must Be Continuously Monitored 

for Turbidity 

Similar pathogen removal 

mechanisms are expected to occur in 

slow sand filtration and bank filtration. 

Under the 40 CFR 141.73(b)(1), the 

turbidity level of slow sand filtered 

water must be 1 NTU or less in 95 

percent of the measurements taken each 

month. Turbidity sampling is required 

once every four hours, but may be 

reduced to once per day under certain 

conditions. Just as turbidity monitoring 

is used to provide assurance that the 

removal credit assigned to a slow sand 

filter is being realized, today’s rule 

requires turbidity monitoring at least 

once every 4 hours for all bank filtration 

wells that receive treatment credit. 

If monthly average turbidity levels 

(based on daily maximum values in the 

well) exceed 1 NTU, the PWS must 

report this result to the State and 

conduct an assessment to determine the 

cause of the high turbidity levels in the 

well. If the State determines that 

microbial removal has been 

compromised, the State may revoke 

treatment credit until the PWS 

implements corrective actions to 

remediate the problem. 

Demonstration of Performance 

EPA recognizes that some bank 

filtration processes may achieve mean 

Cryptosporidium removal greater than 

1-log. Consequently, today’s rule allows 

PWSs to receive greater than 1.0-log 

Cryptosporidium treatment credit for 

bank filtration through a State-approved 

demonstration of performance study. 

This allowance is a change from the 

proposed rule, which did not explicitly 

recognize demonstration of performance 

for bank filtration (USEPA 2003a). This 

change reflects EPA’s agreement with 

public comment, described next, which 

recommended that EPA explicitly 

recognize the option to conduct a bank 

filtration performance study for greater 

than 1.0-log treatment credit. 

A demonstration of performance 

study must involve the collection of 

data on the removal of Cryptosporidium 

or surrogates and related hydrogeologic 

and water quality parameters during the 

full range of operating conditions. PWSs 

must sample from both the production 

well(s) and one or more monitoring 

wells that are screened and located 

along the shortest flow path between the 

surface water and the production 

well(s). This will allow determination of 

the removal efficiency of the aquifer. 

Because directly measuring 

Cryptosporidium removal will not be 

feasible for most PWSs, today’s rule 

allows PWSs to sample for a Stateapproved indicator, such as aerobic 

bacterial endospores. Research has 

shown that aerobic spores can be very 

mobile in the subsurface environment 

(Pang et al. 1998), and data collected by 

Wang et al. (2001) indicate that aerobic 

spores are present in some surface 

waters in sufficient quantity to allow 

measurement of log removal values. 

EPA has provided guidance on 

conducting site-specific bank filtration 


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studies in the Toolbox Guidance 

Manual. This guidance discusses data 

needs and analysis for a performance 

demonstration so that the State may 

tailor the study plan to meet sitespecific hydrogeological and operational 

conditions. 

In summary, EPA believes that fullscale field data support prescribed 

Cryptosporidium treatment credit up to 

1.0-log for bank filtration under the 

required conditions for set-back 

distance, aquifer material, collection 

device type, and turbidity monitoring. 

Demonstration of performance provides 

an appropriate opportunity for States to 

award higher Cryptosporidium 

treatment credit for bank filtration on a 

site-specific basis. 

For PWSs using bank filtration when 

they must conduct source water 

monitoring for bin classification, the 

required sampling locations reflect the 

intent for this monitoring to capture the 

level of Cryptosporidium entering a 

PWS’s primary filtration treatment 

process. Where bank filtration serves as 

pretreatment to a filtration plant, PWSs 

must collect source water samples after 

bank filtration but prior to the filtration 

plant. In this case, the Cryptosporidium 

removal that bank filtration achieves 

will be reflected in the monitoring 

results and bin classification for the 

filtration plant. In contrast, where bank 

filtration is the primary filtration 

process, meaning that a PWS uses bank 

filtration to comply with the 

Cryptosporidium treatment 

requirements of the IESWTR or 

LT1ESWTR, PWSs must collect samples 

in the surface water source (e.g, the 

river). 

c. Summary of Major Comments 

Public comments on the August 11, 

2003, LT2ESWTR proposal supported 

awarding Cryptosporidium treatment 

credit for bank filtration. Many 

commenters, however, stated that the 

proposed levels of credit (0.5- and 1.0- 

log) were insufficient. To address this 

issue, commenters supported allowing 

PWSs to obtain greater treatment credit 

by performing a site-specific study of 

bank filtration removal efficiency. 

Commenters recommended that sitespecific bank filtration studies involve 

the measurement of surrogates for 

Cryptosporidium removal using 

monitoring wells located along the 

shortest flow path between the surface 

water and the production well. 

EPA agrees that some bank filtration 

sites may achieve greater than 1.0-log 

Cryptosporidium removal. Today’s rule 

establishes the proposed bank filtration 

Cryptosporidium treatment credits of 

0.5- and 1.0-log and allows PWSs to 

apply to the State for higher levels of 

credit through a site-specific 

demonstration of performance. In such 

a study, PWSs must measure the 

removal of Cryptosporidium or a Stateapproved surrogate using monitoring 

wells located along the flow path, as 

recommended by commenters. 

Some commenters cited research 

addressing appropriate surrogate 

organisms for estimating 

Cryptosporidium removal in surface 

water treatment plants and bank 

filtration sites. Commenters 

recommended that EPA recognize 

aerobic endospores as a surrogate 

measure in Cryptosporidium removal 

studies, including those for bank 

filtration. 

EPA agrees that based on available 

information, aerobic spores are suitable 

Cryptosporidium removal surrogates for 

bank filtration processes due to their 

size, resistance to inactivation, and 

concentration in surface and ground 

waters. Data from several bank filtration 

sites on the use of aerobic spores as a 

Cryptosporidium removal surrogate are 

available. The Toolbox Guidance 

Manual identifies aerobic spores as 

suitable in conjunction with other 

hydrogeologic data for making sitespecific determinations for additional 

Cryptosporidium removal credit. 

In guidance, EPA suggests that where 

feasible, PWSs measure diatom species 

in conjunction with aerobic spores in 

bank filtration studies because 

Cryptosporidium oocysts are 

intermediate in size between the two 

surrogate groups. Further, EPA 

recognizes the current uncertainties and 

limitations in available information on 

surrogates for bank filtration and will 

update guidance as warranted by new 

information. 

7. Combined Filter Performance 

a. Today’s Rule 

For water treatment plants that use 

filtration, the turbidity of the filtered 

water is an indicator of how effectively 

the plant is removing particulate matter, 

including microbial pathogens, from the 

raw water. PWSs using conventional 

filtration treatment or direct filtration 

receive an additional 0.5-log 

Cryptosporidium treatment credit 

during any month the PWS meets the 

following standard: 

• The turbidity level of representative 

samples of a PWS’s filtered water (i.e., 

the combined filter effluent) is less than 

or equal to 0.15 NTU in at least 95 

percent of the measurements taken each 

month. PWSs must continue to measure 

turbidity as specified in 40 CFR 

141.74(a) and (c), which generally 

require sampling at least every four 

hours using approved methods. 

PWSs using other types of filtration 

processes, including slow sand, 

diatomaceous earth, membranes, bag, or 

cartridge filtration, are not eligible for 

this treatment credit. 

b. Background and Analysis 

Turbidity is a method defined 

parameter that is based on measuring 

the amount of light scattered by 

suspended particles in a solution. This 

measure can detect the presence of a 

wide variety of particles in water, 

including microorganisms, but cannot 

provide specific information on particle 

type, number, or size. In filtered water, 

the turbidity level indicates how well 

the filtration and other upstream 

clarification processes have performed 

in removing particles from the raw 

water, with lower turbidity indicating 

better particle removal. Thus, lower 

filtered water turbidity is associated 

with a decreased likelihood that 

microbial pathogens like 

Cryptosporidium have passed through 

the filtration plant and into the water 

distributed to consumers. 

Under existing regulations, PWSs that 

filter must monitor turbidity in the 

combined filter effluent (CFE) at least 

every four hours using approved 

methods, although States may reduce 

this frequency to once per day for PWSs 

serving 500 people or fewer (40 CFR 

141.74(a) and (c)). For PWSs using 

conventional or direct filtration, at least 

95 percent of the CFE turbidity 

measurements must be less than or 

equal to 0.3 NTU, and the turbidity 

must never exceed 1 NTU (40 CFR 

141.173(a) and 141.551(a)–(b)). 

The Stage 2 M–DBP Advisory 

Committee recommended an additional 

0.5-log Cryptosporidium treatment 

credit for PWSs that achieve a CFE 

turbidity less than or equal to 0.15 NTU 

in at least 95 percent of measurements 

per month (USEPA 2000a). This 95th 

percentile turbidity standard is one half 

the level required under existing 

regulations for PWSs using conventional 

or direct filtration, as stated earlier. The 

August 11, 2003 proposal included this 

treatment credit for PWSs using 

conventional or direct filtration (USEPA 

2003a), and EPA is establishing it in 

today’s final rule with no changes from 

the proposal. The following discussion 

summarizes the basis for this treatment 

credit. 

In the proposal, EPA analyzed the 

improvement in Cryptosporidium 

removal that conventional and direct 

filtration plants realize when operating 

at lower effluent turbidity levels. For 

this analysis, EPA estimated that PWSs 


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complying with the existing 95th 

percentile CFE turbidity standard of 0.3 

NTU will typically operate with filter 

effluent turbidity between 0.1–0.2 NTU; 

PWSs complying with a CFE standard of 

0.15 NTU were estimated to operate 

with filter effluent turbidity less than 

0.1 NTU. Accordingly, EPA compared 

Cryptosporidium removal efficiencies 

when effluent turbidity was below 0.1 

NTU with those when effluent turbidity 

was in the range of 0.1–0.2 NTU. 

Studies by Patania et al. (1995), 

Emelko et al. (1999), and Dugan et al. 

(2001) observed the average removal of 

Cryptosporidium to be 0.5-to 1.2-log 

greater when filter effluent turbidity was 

less than 0.1 NTU in comparison to 

removal with effluent turbidity between 

0.1–0.2 NTU. These studies, therefore, 

indicate that PWSs complying with a 

filter effluent turbidity standard of 0.15 

NTU will achieve at least 0.5-log greater 

Cryptosporidium removal than PWSs 

complying with the existing 0.3 NTU 

standard. Based on this finding, EPA 

concluded that an additional 0.5-log 

Cryptosporidium treatment credit is 

appropriate for PWSs using 

conventional or direct filtration that 

meet a 95th percentile CFE turbidity 

standard of 0.15 NTU. 

Other types of filtration processes, 

such as slow sand, diatomaceous earth, 

membranes, bag, or cartridge filtration, 

are not eligible for this treatment credit. 

These filtration processes remove 

Cryptosporidium through different 

mechanisms than those operative in 

rapid granular media filtration, which is 

used in conventional and direct 

filtration. Available data do not 

establish a similar relationship between 

lower filter effluent turbidity and 

improved Cryptosporidium removal 

efficiency for these other filtration 

processes. 

The SAB reviewed the proposed 

additional Cryptosporidium treatment 

credit for PWSs that operate with very 

low filtered water turbidity. In their 

report, the SAB stated that further 

lowering of turbidity would result in 

further reductions in Cryptosporidium 

in the effluent from filtration processes, 

but available data were limited in 

showing the exact removal that can be 

achieved. Based on the data provided, 

the SAB recommended that no 

additional treatment credit be given to 

plants that demonstrate a CFE turbidity 

of 0.15 NTU or less (SAB 2003). 

In addressing this SAB 

recommendation, EPA recognizes that 

precisely quantifying the increase in 

Cryptosporidium removal that a 

particular filtration plant will realize 

when operating at lower filter effluent 

turbidity is not generally feasible. 

Available data, though, consistently 

show that removal of Cryptosporidium 

is at least 0.5-log greater when filter 

effluent turbidity reflects compliance 

with a 0.15 NTU standard in 

comparison to a 0.3 NTU standard. 

Further, treatment plants operating at 

lower filter effluent turbidity will 

achieve increased removal of other 

microbial pathogens present in the raw 

water. In consideration of these factors, 

EPA believes that PWSs should receive 

an additional 0.5-log Cryptosporidium 

treatment credit when at least 95 

percent of CFE turbidity measurements 

are less than or equal to 0.15 NTU. 

Another key issue in establishing 

additional treatment credit based on low 

filtered water turbidity is the 

performance of analytical instruments 

(turbidimeters) to accurately measure 

turbidity at low levels. In the proposal, 

EPA reviewed studies of low level 

turbidity measurements by EPA (1998c), 

Sadar (1999), and Letterman et al. 

(2001). Among the significant findings 

of these studies are the following: 

(1) On-line turbidimeters typically had a 

positive bias (i.e., a higher turbidity reading) 

in comparison to bench-top turbidimeters. 

EPA expects that most PWSs that receive 

additional treatment credit for low filter 

effluent turbidity will use on-line 

turbidimeters. This finding suggests that the 

error in turbidimeter readings may be 

generally conservative, so that PWSs will 

operate at lower than required turbidity 

levels. 

(2) Different turbidimeters did not agree 

well when used to measure low level 

turbidity, which may be due to differences in 

instrument design. This finding suggests that 

low level turbidity measurements may be 

viewed as a relative indicator of water quality 

improvement at a particular PWS but may be 

less applicable for making comparisons 

among different PWSs. 

In addition, the American Society for 

Testing and Materials (ASTM) has 

issued standard test methods for 

measurement of turbidity below 5 NTU 

by on-line (ASTM 2001) and static 

(ASTM 2003) instruments. These 

methods specify that the instrument 

should permit detection of turbidity 

differences of 0.01 NTU or less in waters 

having turbidities of less than 1.00 NTU 

(ASTM 2001) and 5.0 NTU (ASTM 

2003), respectively. 

After reviewing these studies and the 

ASTM methods, EPA concluded that 

currently available monitoring 

equipment can reliably measure 

turbidity at levels of 0.15 NTU and 

lower. Rigorous calibration and 

maintenance of turbidity monitoring 

equipment is necessary, however. EPA 

has developed guidance on proper 

calibration, operation, and maintenance 

of turbidimeters (USEPA 1999c). 

c. Summary of Major Comments 

Public comment on the August 11, 

2003, LT2ESWTR proposal supported 

awarding additional Cryptosporidium 

treatment credit for PWSs that achieve 

lower filtered water turbidity. 

Commenters raised specific concerns 

with the criteria for PWSs to receive this 

credit, the available data that support 

this credit, and the performance of 

turbidimeters for measuring turbidity at 

very low levels. A summary of these 

comments and EPA’s responses follows. 

Most commenters supported awarding 

0.5-log additional Cryptosporidium 

treatment credit for PWSs that achieve 

at least 95 percent of CFE turbidity 

measurements less than or equal to 0.15 

NTU. A few commenters, however, 

recommended that PWSs only receive 

additional treatment credit for 

demonstrating this level of turbidity 

performance in each individual filter 

effluent (IFE), rather than the CFE. In 

addition, one commenter stated that 

PWSs should be required to monitor 

CFE turbidity every 15 minutes, rather 

than every four hours as required under 

current regulations. 

In response, EPA agrees with the 

recommendation of most commenters 

and has established additional 

Cryptosporidium treatment credit based 

on meeting a 95th percentile turbidity 

level of 0.15 NTU in the CFE. EPA 

recognizes, however, that achieving low 

turbidity in each IFE may represent a 

higher level of performance than 

achieving low turbidity in the CFE. As 

described in the next section, EPA has 

also established standards for additional 

Cryptosporidium treatment credit based 

on low IFE turbidity in today’s rule. 

EPA does not have data indicating that 

PWSs should monitor the CFE turbidity 

at a higher frequency than every four 

hours, as required under existing 

regulations. Consequently, EPA is not 

changing the frequency of required CFE 

turbidity monitoring as a condition for 

PWSs to receive additional treatment 

credit under today’s rule. 

One commenter summarized 

additional studies that provide data on 

the improvement in Cryptosporidium 

removal efficiency at lower filter 

effluent turbidity levels. According to 

this commenter, these studies 

demonstrate that lowering filter effluent 

turbidity from 0.3 to 0.15 NTU 

translates to an improvement in 

Cryptosporidium removal of more than 

1.5-log, with individual studies showing 

a range of >0.7-log to >3-log based on 

median removal. EPA finds that these 

studies bolster the conclusion that 

PWSs operating to meet 0.15 NTU in the 

filter effluent will achieve at least 0.5- 


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log greater Cryptosporidium removal 

than PWSs operating to meet 0.3 NTU. 

Thus, they support the additional 0.5- 

log Cryptosporidium treatment credit 

under today’s rule for PWSs meeting 

0.15 NTU at the 95th percentile in the 

CFE. 

In regard to the measurement of low 

level turbidity, some commenters raised 

concerns that turbidimeters used by the 

U.S. water supply industry do not agree 

when used to measure turbidity in the 

0.01 to 0.5 NTU range. Further, these 

differences are independent of the 

calibration method used and can be 

significant when comparing instruments 

by different manufacturers. Other 

commenters stated that turbidimeters 

can accurately reflect turbidity values 

less than 0.15 NTU if properly 

calibrated, and some commenters cited 

the ASTM method development process 

to support this assessment. In addition, 

commenters suggested that available 

guidance on turbidity measurement 

provides quality assurance measure that 

can reduce analytical uncertainty. 

EPA agrees with commenters that 

available methods and instruments are 

adequate to demonstrate compliance 

with a 0.15 NTU turbidity level. In 

particular, EPA believes that monitoring 

low level turbidity can be effective for 

demonstrating water quality 

improvements at individual plants, but 

also recognizes that the performance of 

turbidimeters used at different plants 

may vary. Further, calibration and 

maintenance of turbidity monitoring 

equipment is critical, and EPA has 

developed guidance on these 

procedures (USEPA 1999c). 

8. Individual Filter Performance 

a. Today’s Rule 

PWSs using conventional filtration 

treatment or direct filtration receive an 

additional 0.5-log Cryptosporidium 

treatment credit during any month the 

PWS meets the following criteria: 

• The filtered water turbidity for each 

individual filter is less than or equal to 

0.15 NTU in at least 95 percent of the 

measurements recorded each month; 

and 

• No individual filter has a measured 

turbidity level greater than 0.3 NTU in 

two consecutive measurements taken 15 

minutes apart. 

PWSs must continue to monitor 

turbidity for each individual filter 

continuously and record the results 

every 15 minutes, as required under 40 

CFR 141.174 and 141.560. 

PWSs that receive this 0.5-log 

Cryptosporidium treatment credit for 

individual filter performance also 

receive 0.5-log treatment credit for 

combined filter performance, as 

described in section IV.D.7, for a total 

additional treatment credit of 1.0-log. 

Conversely, PWSs are not required to 

pursue individual filter performance 

credit to remain eligible for combined 

filter performance credit. 

If a PWS has received credit for 

individual filter performance to comply 

with its Cryptosporidium treatment 

requirements and fails to meet the 

required criteria for this credit during 

any month, the PWS will not incur a 

treatment technique violation if the 

State determines the following: 

• The failure to meet the required 

criteria for individual filter performance 

treatment credit was due to unusual and 

short-term circumstances that could not 

reasonably be prevented through 

optimizing treatment plant design, 

operation, and maintenance; and 

• The PWS has experienced no more 

than two such failures in any calendar 

year. 

This treatment credit is not applicable 

to other types of filtration processes, 

including slow sand, diatomaceous 

earth, membranes, bag, or cartridge 

filtration. 

b. Background and Analysis 

Awarding additional treatment credit 

for individual filter performance is 

based on the expectation that achieving 

low filtered water turbidity in each 

individual filter will provide increased 

protection against microbial pathogens. 

Most treatment plants have multiple 

filters. Moderately elevated turbidity in 

the effluent from a single filter may not 

significantly affect the turbidity of the 

combined filter effluent, but may 

indicate a reduction in the overall 

pathogen removal efficiency of the 

filtration process. Consequently, a 

primary goal in optimizing water 

treatment plant performance is ensuring 

that each filter always produces very 

low turbidity water. 

The criteria for PWSs to achieve the 

additional 1.0-log Cryptosporidium 

treatment credit for individual filter 

performance reflect goals of Phase IV of 

the Partnership for Safe Water 

(Partnership). The Partnership is a 

voluntary cooperative program 

involving PWSs, professional 

associations, and Federal and State 

regulatory agencies that seeks to 

increase protection against microbial 

contaminants by optimizing water 

treatment plant performance. The Stage 

2 M–DBP Advisory Committee 

recommended 1.0-log treatment credit 

for PWSs that successfully participate in 

a peer review program and identified 

Phase IV of the Partnership as a program 

where such credit would be appropriate 

(USEPA 2000a). 

At the time of the Advisory 

Committee recommendation, the 

performance goals for Phase IV of the 

Partnership reflected those of the EPA 

Composite Correction Program (USEPA 

1991a) and involved an on-site 

evaluation by a third-party team. Phase 

IV performance goals for individual 

filters included filtered water turbidity 

less than 0.1 NTU at least 95 percent of 

the time based on daily maximum 

values and a maximum measurement of 

0.3 NTU. The purpose of the on-site 

evaluation was to confirm that a PWS 

had met Phase IV performance goals or 

had achieved the highest level of 

performance given its unique raw water 

quality. 

After the Stage 2 M–DBP Agreement 

in Principle was signed in September 

2000, the Partnership eliminated on-site 

third-party evaluation as a component 

of Phase IV. Instead, Phase IV required 

completion of an Optimization 

Assessment Spreadsheet in which the 

PWS entered water treatment data to 

demonstrate that it had achieved Phase 

IV performance levels. The application 

also required narratives related to the 

administrative support and operational 

capabilities necessary to sustain 

performance long-term. 

The August 11, 2003 LT2ESWTR 

proposal included a 1.0-log 

Cryptosporidium treatment credit for 

PWSs that met the individual filter 

performance goals of Phase IV of the 

Partnership (i.e., 95 percent of daily 

maximum values below 0.1 and no 

values above 0.3 NTU) (USEPA 2003a). 

Rather than requiring an application 

package with historical data and 

narratives, however, the proposed rule 

required PWSs to report filter effluent 

turbidity data to the State each month 

to demonstrate compliance with these 

filter performance goals. 

The Partnership modified the Phase 

IV goals for individual filter 

performance in 2003. A revised goal is 

filtered water turbidity less than 0.10 

NTU at least 95 percent of the time 

based on values recorded at 15 minute 

time intervals. Thus, where the earlier 

goal was based on daily maximum 

values for each filter, the revised goal is 

based on all values for each filter—a less 

stringent approach. The Partnership 

made this modification after finding that 

none of the water treatment plants that 

had been evaluated could consistently 

meet the 0.1 NTU goal using daily 

maximum values and, further, that this 

goal was biased against plants with 

more filters. 

In today’s final rule, EPA has adjusted 

the criteria from the proposal for PWSs 


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to receive additional treatment credit 

based on individual filter effluent 

turbidity. These adjustments are in 

response to the changes the Partnership 

made to Phase IV individual filter 

performance goals. Under today’s rule, 

PWSs receive 1.0-log additional 

Cryptosporidium treatment credit if 

effluent turbidity from each filter is less 

than or equal to 0.15 NTU at least 95 

percent of the time and never exceeds 

0.3 NTU in two consecutive 

measurements taken 15 minutes apart. 

EPA expects that PWSs will operate at 

less than 0.1 NTU in order to comply 

with a regulatory limit of 0.15 NTU. 

Further, EPA believes that assessing 

individual filter compliance with a 

maximum turbidity level of 0.3 NTU 

based on two consecutive measurements 

taken 15 minutes apart is appropriate. 

This approach allows for brief 

fluctuations in turbidimeter readings 

that may not indicate a degradation in 

filtered water quality to occur without 

penalizing a PWS, but it should catch 

filters that significantly exceed 0.3 NTU 

over the course of a month. EPA applied 

this approach to individual filter 

monitoring under the IESWTR and 

LT1ESWTR. Consequently, EPA regards 

these criteria as comparable to the 

revised Partnership Phase IV standards 

for individual filter performance. 

In addition, today’s rule gives States 

authority to determine whether to issue 

a treatment technique violation for 

PWSs that exceed individual filter 

performance limits. This authority 

applies in the case where a PWS 

receives credit for individual filter 

performance to meet the treatment 

requirements of today’s rule and fails to 

achieve the criteria to receive this credit 

during a month. If the State determines 

that this failure was due to unusual and 

short-term circumstances that could not 

reasonably be prevented through 

treatment optimization, the State may 

choose not to issue a treatment 

technique violation, which the PWS 

otherwise will incur. Because this 

authority should be applied only to 

unusual plant circumstances, a State 

cannot make this determination if a 

PWS has experienced more than two 

such failures in any calendar year. 

EPA is granting States this authority 

because PWSs that consistently meet the 

criteria for individual filter performance 

treatment credit may occasionally 

experience short-term deviations from 

these criteria due to circumstances 

largely beyond the PWS’s control. An 

example of such a circumstance may be 

malfunctioning equipment that a PWS 

quickly removes from service, but that 

nevertheless prevents the PWS from 

fully meeting individual filter 

performance criteria in a particular 

month. EPA believes that States should 

only apply this authority in cases where 

PWSs have consistently achieved the 

criteria for individual filter performance 

treatment credit in previous months. 

The approach in today’s final rule for 

valuing individual filter performance 

treatment credit differs from the 

approach in the proposal. EPA’s intent 

in both the proposal and today’s rule is 

to award an additional 1.0-log 

Cryptosporidium treatment credit to 

PWSs that meet the criteria for 

individual filter performance. In the 

proposal, however, PWSs could receive 

1.0-log additional treatment credit 

specifically for meeting the individual 

filter performance criteria, but were 

then not eligible to receive any 

treatment credit under the combined 

filter performance option. In today’s 

rule, PWSs receive 0.5-log credit for the 

individual filter performance option and 

also receive an additional 0.5-log 

treatment credit for the combined filter 

performance option (discussed in 

section IV.D.7), resulting in 1.0-log total 

additional credit. EPA has made this 

modification so that if a PWS fails in an 

attempt to achieve individual filter 

performance credit, the PWS is clearly 

still eligible to received combined filter 

performance credit. 

In a review of a draft LT2ESWTR 

proposal, the SAB recommended that 

PWSs receive 0.5-log, rather than 1.0- 

log, additional Cryptosporidium 

treatment credit for achieving 

individual filter effluent turbidity below 

0.15 NTU at the 95th percentile (SAB 

2003). In response to this SAB 

recommendation, today’s rule requires 

additional individual filter performance 

criteria to support 1.0-log total 

additional treatment credit. Specifically, 

today’s rule incorporates the 

Partnership Phase IV performance goal 

that individual filter effluent turbidity 

never exceed 0.3 NTU (as described 

earlier, EPA concluded that determining 

compliance with this standard based on 

two consecutive measurements taken 15 

minutes is appropriate and consistent 

with existing regulations). Thus, EPA 

believes that these criteria, in 

conjunction with the expectation that 

controlling effluent turbidity at all 

filters individually rather than just the 

combined filter effluent will generally 

result in lower microbial risk, justify 

1.0-log additional treatment credit. 

c. Summary of Major Comments 

Public comment on additional 

treatment credit for individual filter 

performance in the August 11, 2003 

proposal raised a number of issues: 

changes in the Partnership Phase IV 

criteria and achievability of the 

proposed criteria for this credit, credit 

for participating in peer review 

programs, and a review process for data 

that exceed regulatory limit. A summary 

of these comments and EPA’s responses 

follows. 

Several commenters stated that PWSs 

could not consistently achieve the 

proposed individual filter effluent 

turbidity criterion of 95 percent of daily 

maximum measurements less than or 

equal to 0.1 NTU. Commenters provided 

data on turbidity levels in PWSs to 

support this assertion and indicated that 

the Partnership modified this criterion 

in the Phase IV individual filter 

performance goals because PWSs could 

not meet it. Alternatives recommended 

by commenters for the final rule 

included the use of the revised 

Partnership Phase IV goals for 

individual filter effluent turbidity or a 

more stringent criterion for combined 

filter effluent turbidity. 

In response, EPA agrees that current 

Partnership Phase IV goals provide 

appropriate criteria for awarding 1.0-log 

total additional Cryptosporidium 

treatment credit. Today’s rule grants this 

total credit to PWSs that meet a 95th 

percentile individual filter effluent 

turbidity limit of 0.15 NTU, and EPA 

expects that PWSs complying with this 

limit will operate under the Partnership 

goal of 0.10 NTU. EPA does not support 

awarding a higher level of additional 

treatment credit for a more stringent 

combined filter effluent turbidity 

criterion, beyond the 0.5-log credit 

available under combined filter 

performance (see section IV.D.7). The 

purpose of the individual filter 

performance toolbox option is to 

recognize the higher pathogen removal 

PWSs will likely achieve by maintaining 

very low effluent turbidity for each 

individual filter. 

A few commenters suggested that as 

an alternative to establishing numerical 

criteria for individual filter 

performance, today’s rule should award 

additional treatment credit for PWSs 

that successfully participate in a peer 

review program. In addition to the 

Partnership, commenters listed the Area 

Wide Optimization Program and the 

Texas Optimization Program as 

examples of programs that will provide 

for comprehensive improvements in 

treatment performance. 

EPA agrees that participation in peer 

review programs is beneficial for PWSs. 

Further, such programs may assist PWSs 

in meeting the filtration performance 

criteria in today’s rule for additional 

Cryptosporidium treatment credit. EPA 

does not believe, however, that mere 

participation in a peer review program 


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is an appropriate basis for awarding 

additional treatment credit. Rather, to 

ensure national consistency in 

standards for compliance with treatment 

requirements, EPA has concluded that 

additional treatment credit should be 

based on PWSs meeting specified 

criteria for enhanced treatment 

performance. 

Another significant issue raised by 

commenters is the need for a review 

process for deviations from the criteria 

for individual filter performance due to 

circumstances that cannot be prevented 

through plant optimization. An example 

given by several commenters is a filter 

that malfunctions and is taken out of 

service, but that may have exceeded the 

individual filter performance turbidity 

criteria for a short period when the filter 

was operating. 

EPA agrees that circumstances may 

occur that are beyond the PWS’s control 

and that prevent the PWS from fully 

meeting the criteria for individual filter 

performance in a particular month. If a 

PWS relies on individual filter 

performance treatment credit to meet 

the treatment requirements of today’s 

rule and the PWS fails to meet all 

criteria for this credit in a given month, 

the State may review the reasons for this 

failure. If the State finds that the failure 

was due to circumstances that could not 

be prevented through plant 

optimization, the State may choose not 

to issue a treatment technique violation 

on up to two such occasions in a 

calendar year. 

9. Demonstration of Performance 

a. Today’s Rule 

A demonstration of performance is a 

site-specific test that assesses the 

Cryptosporidium removal efficiency of a 

water treatment plant or a treatment 

process within a plant. Under today’s 

rule, PWSs may undertake 

demonstration of performance testing 

for the following purposes: 

(1) To establish a Cryptosporidium 

treatment credit that is higher than the 

prescribed treatment credit in today’s rule for 

a water treatment plant or a treatment 

process in the microbial toolbox; or 

(2) To establish a Cryptosporidium 

treatment credit for a treatment process that 

is not included in the microbial toolbox or 

that does not meet the design or operational 

criteria for prescribed treatment credit in the 

microbial toolbox. 

The specific requirements that apply 

to demonstration of performance testing 

are as follows: 

• PWSs may receive Cryptosporidium 

treatment credit for a water treatment 

plant or a treatment process within a 

plant that is based on a site-specific 

demonstration of Cryptosporidium 

removal efficiency. This demonstration 

of performance treatment credit may be 

greater than or less than any prescribed 

treatment credit in today’s rule. 

• The site-specific demonstration of 

Cryptosporidium removal efficiency 

must follow a State-approved protocol 

and may involve the use of surrogates 

rather than Cryptosporidium. 

• The State must approve through 

written notification any treatment credit 

based on a demonstration of 

performance. As a condition of 

approval, the State may designate 

monitoring and treatment performance 

criteria the PWS must meet and report 

on an ongoing basis to remain eligible 

for the credit. The State may designate 

such criteria to verify that the PWS 

maintains the operating conditions 

under which the State approved the 

demonstration of performance treatment 

credit. 

• PWSs are not eligible for prescribed 

treatment credit for any treatment 

process that is included in a 

demonstration of performance credit. 

b. Background and Analysis 

The prescribed Cryptosporidium 

treatment credits in today’s rule for 

water treatment plants and for treatment 

processes in the microbial toolbox are 

based on conservative estimates of mean 

Cryptosporidium removal efficiencies. 

Due to site-specific conditions, 

however, some PWSs will achieve 

greater Cryptosporidium removal than 

reflected in the prescribed treatment 

credits. In addition, some PWSs will 

have treatment processes that are not 

included in the microbial toolbox or 

that do not meet microbial toolbox 

criteria for prescribed treatment credit. 

In all these cases, PWSs have the option 

to undertake demonstration of 

performance testing to establish an 

appropriate level of Cryptosporidium 

treatment credit for the treatment plant 

or treatment process. 

The option for demonstration of 

performance testing in today’s rule 

reflects a recommendation by the Stage 

2 M–DBP Advisory Committee. 

Specifically, the Committee stated that 

the LT2ESWTR should allow sitespecific testing both to establish 

Cryptosporidium treatment credit above 

the prescribed credit for microbial 

toolbox processes and to demonstrate 

Cryptosporidium removal for 

technologies not listed in the microbial 

toolbox. The August 11, 2003 

LT2ESWTR proposal included the 

demonstration of performance option 

(USEPA 2003a), and EPA is establishing 

it in today’s final rule. 

Demonstration of performance testing 

will be specific to a particular site and 

will depend on the treatment processes 

being tested, water quality, plant 

infrastructure, PWS resources, and other 

factors. Consequently, today’s rule does 

not establish specific protocols for 

demonstration of performance testing. 

Rather, today’s rule gives States the 

authority to approve testing protocols 

developed by PWSs and to determine 

what level of Cryptosporidium 

treatment credit is appropriate. The 

Toolbox Guidance Manual provides 

recommendations to PWSs and States 

on conducting demonstration of 

performance testing, including 

analytical methods for measuring 

aerobic and anaerobic spores. 

In general, demonstration of 

performance testing should encompass 

the full range of expected operating 

conditions and should conservatively 

assess the degree of Cryptosporidium 

removal that a treatment process can 

reliably achieve. Directly quantifying 

the removal of Cryptosporidium 

typically is not feasible in full-scale 

testing due to limitations in source 

water concentrations and analytical 

method performance. Consequently, 

demonstration of performance testing 

that is conducted at full-scale may 

involve the use of surrogates, such as 

aerobic spores, that have been shown to 

correlate with the removal of 

Cryptosporidium. PWSs and States may 

also consider the use of pilot-scale 

studies in conjunction with full-scale 

studies for demonstration of 

performance testing. 

As a condition of approving a 

demonstration of performance credit, 

the State may designate treatment 

performance criteria the PWS must meet 

on an ongoing basis to remain eligible 

for the credit. For example, if a PWS 

conducts a demonstration of 

performance study while operating with 

very low filtered water turbidity, the 

State may establish as a condition of 

approving treatment credit based on the 

study that the PWS must continue 

operating at the low filtered water 

turbidity. EPA believes this condition is 

necessary because, in this example, if 

the PWS were to begin operating at a 

higher filtered water turbidity level, the 

demonstration of performance study 

results might no longer represent the 

PWSs actual performance. 

PWSs are not eligible for prescribed 

treatment credit for any treatment 

process that is included in a 

demonstration of performance credit. 

For example, if a PWS receives a 

demonstration of performance treatment 

credit of 4-log for Cryptosporidium 

removal through a conventional 

treatment plant (i.e., coagulation/ 

sedimentation/filtration), the PWS is not 


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also eligible for additional treatment 

credit for combined filter performance. 

In this case, the demonstration of 

performance testing accounts for the 

removal achieved by filtration. 

c. Summary of Major Comments 

Public comment on the August 11, 

2003 LT2ESWTR proposed supported 

inclusion of the demonstration of 

performance option to award sitespecific treatment credit to PWSs. 

Commenters stated that many well-run 

surface water treatment plants achieve 

significantly greater Cryptosporidium 

removal than the prescribed treatment 

credit, and demonstration of 

performance testing is needed to award 

an appropriate level of credit in such 

cases. Two aspects of this option that 

received significant public comment are 

the provision for States to award less 

than the prescribed treatment credit if 

indicated by testing results and the need 

for guidance on demonstration of 

performance testing. These comments 

and EPA’s responses are summarized as 

follows. 

Several commenters recommended 

that EPA eliminate the provision that 

allows States to award less than the 

prescribed treatment credit based on 

demonstration of performance testing. 

These commenters stated that pilot- and 

full-scale testing is conservative and 

challenging to implement and that for 

past regulations, States generally have 

not awarded lower treatment credit 

based on a site-specific study. If this 

provision remains in the regulation, 

commenters suggested that EPA provide 

criteria addressing how it should be 

applied. Such criteria should recognize 

the conservative nature of testing with 

surrogates for Cryptosporidium removal 

and the potential for misleading or 

flawed testing results. 

In response, EPA believes that States 

should have the discretion to award 

either more or less treatment credit than 

the prescribed credit on a case-by-case 

basis where a State has site-specific 

information that an alternative credit is 

appropriate. Today’s rule allows this. 

EPA recognizes, however, that 

demonstration of performance testing 

should be designed to provide a 

conservative estimate of treatment 

efficiency and, as such, is not generally 

intended to reduce the level of 

treatment credit a PWS receives. 

Further, results from demonstration of 

performance testing should be 

rigorously evaluated for flaws and bias 

prior to being used to support either a 

higher or lower treatment credit. The 

Toolbox Guidance Manual identifies 

approaches States may wish to consider 

in awarding higher or lower treatment 

credit. 

Many commenters stated that EPA 

should provide thorough guidance on 

demonstration of performance testing. 

Topics for this guidance suggested by 

commenters include approaches to 

demonstrating treatment credit, 

minimum duration of testing, the use of 

safety factors, and periodic 

reconfirmation of testing results. Some 

commenters recommended that 

guidance address both full-scale testing 

with surrogates like aerobic spores and 

pilot-scale testing with Cryptosporidium 

or surrogates. Other commenters 

recommended that testing should be 

limited to full-scale processes and that 

testing with pilot-scale representations 

of full-scale equipment should be 

discouraged. 

In the Toolbox Guidance Manual, 

EPA provides direction on procedures 

for demonstration of performance 

testing that addresses issues raised by 

commenters. These issues include 

surrogates for full-scale testing, 

potential roles for pilot-scale testing in 

conjunction with full-scale testing, 

minimum duration of testing to capture 

the full range of operating conditions, 

the analysis of data from testing to 

establish treatment credit, and routine 

monitoring to verify that the conditions 

under which demonstration of 

performance credit is awarded are 

maintained during routine operation. 

EPA believes that this guidance will 

assist PWSs and States with 

implementing demonstration of 

performance testing appropriately. 

10. Bag and Cartridge Filtration 

a. Today’s Rule 

Under today’s rule, PWSs may receive 

Cryptosporidium treatment credit of up 

to 2.0-log for an individual bag or 

cartridge filter and up to 2.5-log for two 

or more bag or cartridge filters operated 

in series. To be eligible for this 

treatment credit, filters must meet the 

definition of a bag or cartridge filter and 

must undergo challenge testing to 

demonstrate removal efficiency with an 

applied safety factor, as described in 

this section. 

Today’s rule defines bag and cartridge 

filters as pressure driven separation 

processes that remove particulate matter 

larger than 1 micrometer using an 

engineered porous filtration media 

through either surface or depth 

filtration. Bag filters are constructed of 

a non-rigid, fabric filtration media 

housed in a pressure vessel in which the 

direction of flow is from the inside of 

the bag to the outside. Cartridge filters 

are typically constructed as rigid or 

semi-rigid, self-supporting filter 

elements housed in a pressure vessel in 

which flow is from the outside of the 

cartridge to the inside. 

Today’s rule treats bag and cartridge 

filters equivalently, with the following 

exception: If a cartridge filter meets the 

definition of a membrane filtration 

process and can be direct integrity 

tested according to the criteria specified 

in section IV.D.11, a PWS has the option 

to seek greater treatment credit for the 

filter as a membrane. Section IV.D.11 

describes criteria for awarding treatment 

credit to membranes. 

Today’s rule requires challenge 

testing to establish Cryptosporidium 

treatment credit for bag and cartridge 

filters. This challenge testing is productspecific and not site-specific. Once 

challenge testing is performed on a 

specific bag or cartridge filtration 

product, PWSs that install the specific 

filtration product are not required to 

repeat challenge testing at individual 

sites. For a PWS to receive 

Cryptosporidium treatment credit for a 

bag or cartridge filter, challenge testing 

must meet the following criteria: 

• Challenge testing must be 

conducted on full-scale filters that 

match the filters the PWS will use in 

materials, construction, and associated 

housing or pressure vessel. If treatment 

credit will be based on filters operated 

in series then challenge testing must be 

performed on the filters in series. 

• Challenge testing must involve 

measuring the removal by the filter of 

either Cryptosporidium or a surrogate 

that is removed no more efficiently than 

Cryptosporidium (i.e., the ‘‘challenge 

particulate’’). 

• The analytical method used to 

measure removal in the challenge test 

must discretely quantify the specific 

challenge particulate. The maximum 

allowable feed water concentration of 

the challenge particulate used during a 

challenge test is 10,000 times the 

analytical method detection limit of the 

challenge particulate in the filtrate. 

• During challenge testing, filters 

must be operated at the maximum 

design flow rate and for a duration 

sufficient to reach the maximum design 

pressure drop (i.e., ‘‘terminal pressure 

drop’’). PWSs may not operate bag or 

cartridge filters outside of these design 

parameters during routine use. In order 

to achieve terminal pressure drop 

during challenge testing, adding 

particulate matter, such as fine carbon 

test dust or bentonite clay particles, to 

the test water is allowed and may be 

necessary. 

• In each challenge test, the removal 

of the challenge particulate must be 

measured during three periods over the 


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filtration cycle: (1) Within two hours of 

start-up of a new filter, (2) when the 

pressure drop is between 45 and 55 

percent of the terminal pressure drop, 

and (3) when the pressure drop has 

reached 100 percent of the terminal 

pressure drop. A log removal value 

(LRV) must be calculated for each of 

these periods as follows: LOG10 (filter 

influent challenge particulate level) ¥ 

LOG10 (filter effluent challenge 

particulate level). For each filter tested, 

the LRV for the filter (LRVfilter) is equal 

to the minimum of these three LRVs. 

• The LRVfilter values for each filter 

that is tested are used to determine the 

removal efficiency that is assigned to 

the specific bag or cartridge filter 

product (i.e., a filter product line) or 

combination of filters in series. If fewer 

than twenty filters are tested, the 

removal efficiency of the filter product 

line is equal to the lowest LRVfilter

among the filters tested (today’s rule 

does not specify a minimum number of 

filters to test). If twenty or more filters 

are tested, the removal efficiency of the 

filter product line is equal to the 10th 

percentile of the LRVfilter values among 

the filters tested. 

• The Cryptosporidium treatment 

credit assigned to an individual bag or 

cartridge filter is equal to the removal 

efficiency established during challenge 

testing minus a 1.0-log factor of safety, 

up to a maximum treatment credit of 

2.0-log (e.g., if challenge testing 

demonstrates a removal efficiency of 

3.0-log or greater, the filter is eligible to 

receive 2.0-log Cryptosporidium 

treatment credit). 

• The Cryptosporidium treatment 

credit assigned to configurations of two 

or more bag or cartridge filters operated 

in series is equal to the removal 

efficiency established during challenge 

testing minus a 0.5-log factor of safety, 

up to a maximum treatment credit of 

2.5-log (e.g., if challenge testing 

demonstrates a removal efficiency of 3- 

log or greater, the filter receives 2.5-log 

Cryptosporidium treatment credit). 

If a previously tested bag or cartridge 

filter is modified in a manner that could 

change the removal efficiency of the 

filter product line, a new removal 

efficiency must be established for the 

modified filter through challenge 

testing. If approved by the State, data 

from challenge testing conducted prior 

to promulgation of today’s rule may be 

considered in lieu of additional testing. 

However, the prior testing must have 

been conducted in a manner that 

demonstrates a removal efficiency for 

Cryptosporidium commensurate with 

the treatment credit awarded to the 

filter. 

b. Background and Analysis 

Bag and cartridge filters are widely 

used by very small PWSs and in pointof-entry applications to remove 

particulate material from raw water, 

including microbial pathogens like 

Cryptosporidium. Depending on water 

quality and treatment plant 

infrastructure, these filters may be used 

as the sole filtration step or as a 

polishing filter that follows primary 

filtration processes. A critical aspect of 

bag and cartridge filters as defined in 

today’s rule is that they cannot undergo 

direct integrity testing, which is used to 

detect leaks that could result in 

contamination of the treated water. 

Cartridge filters that meet the definition 

of a membrane process and can be direct 

integrity tested are considered 

membranes under today’s rule, and 

these are described in section IV.D.11. 

The Stage 2 M–DBP Advisory 

Committee recommended 

Cryptosporidium treatment credits of 

1.0- and 2.0-log for bag and cartridge 

filters, respectively (USEPA 2000a), and 

the August 11, 2003 LT2ESWTR 

proposal included criteria for PWSs to 

receive these treatment credits. The 

proposed criteria required challenge 

testing and the application of a 1.0-log 

factor of safety to establish treatment 

credit. In today’s final rule, EPA has 

modified these criteria to allow both bag 

and cartridge filters to be eligible for 

2.0-log credit and to allow 2.5-log credit 

with a 0.5-log factor of safety for bag or 

cartridge filters operated in series. The 

following discussion summarizes the 

basis for these criteria and for 

differences between the proposal and 

today’s final rule. 

In the proposal, EPA reviewed bag 

and cartridge filtration studies by Long 

(1983), Schaub et al. (1993), Goodrich et 

al. (1995), Ciardelli (1996a and 1996b), 

Li et al. (1997), Roessler (1998), 

Enriquez et al. (1999), NSF (2001a and 

2001b), and Cornwell and LeChevallier 

(2002). Results from these studies 

indicated that both bag and cartridge 

filters exhibit variable removal 

efficiency, ranging from 0.5- to 3.6-log. 

No correlation between the pore size 

rating established by the manufacturer 

and the removal efficiency of the filter 

was apparent. Additionally, available 

data did not indicate a strong 

relationship between commonly used 

process monitoring parameters, such as 

turbidity and pressure drop, and 

Cryptosporidium removal efficiency. 

Due to this lack of correlation 

between either design criteria or process 

monitoring and removal efficiency, 

today’s rule requires challenge testing of 

filters to establish Cryptosporidium 

treatment credit. Challenge testing must 

measure the removal across the filter of 

Cryptosporidium or a surrogate, like 

polystyrene microspheres, that is 

removed no more efficiently than 

Cryptosporidium (Long 1983, Li et al. 

1997, NSF 2002b). Further, because 

studies have shown the removal 

efficiency of some bag and cartridge 

filters to decrease over the course of a 

filtration cycle (Li et al. 1997, NSF 

2001a,b), challenge testing must assess 

removal efficiency during three periods: 

within two hours of startup of a new 

filter, between 45–55 percent of 

terminal pressure drop, and at the end 

of the run after terminal pressure drop 

is realized. 

Bag and cartridge filter challenge 

testing is product-specific and not sitespecific since the intent of this testing 

is to demonstrate the removal 

capabilities of the filtration device 

rather than evaluate the feasibility of 

implementing the technology at a 

specific plant. Challenge testing must be 

conducted using full-scale filter 

elements to assess the performance of 

the entire unit, including the filtration 

media, seals, filter housing and other 

components integral to the filtration 

system. To be eligible for treatment 

credit when operated in series, filters 

must be tested in series. Multiple filters 

of the same type can be tested to 

provide a better statistical basis for 

estimating removal efficiency. The 

Toolbox Guidance Manual provides 

information on bag and cartridge filter 

challenge testing. 

Today’s rule establishes the proposed 

requirement that a 1.0-log factor of 

safety be applied to the removal 

efficiency established during challenge 

testing for individual bag or cartridge 

filters when determining treatment 

credit. Thus, to receive a 2.0-log 

treatment credit, a removal efficiency of 

at least 3.0-log must be demonstrated 

during challenge testing. EPA believes 

that this factor of safety is necessary 

because integrity testing with bag and 

cartridge filters is not possible (note: 

under today’s rule, cartridge filters that 

can be integrity tested are classified as 

membranes and no safety factor is 

required; see section IV.D.11). 

Challenge testing provides an estimate 

of the removal efficiency of a bag or 

cartridge filter product line but does not 

involve testing every filter. Further, it 

does not fully capture the variation in 

filter performance that will occur over 

time during routine use. For 

membranes, the use of direct integrity 

tests, such as a pressure hold test, that 

is correlated to removal efficiency 

addresses this problem. With bag and 

cartridge filters, however, EPA is aware 


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of no equivalent test, and parameters 

like turbidity and pressure differential 

that may be monitored with these filters 

have not been shown to correlate with 

Cryptosporidium removal efficiency. 

Consequently, a safety factor is 

necessary to account for variation in 

individual filter performance relative to 

challenge test results. 

Individual bag and cartridge filters are 

eligible for a maximum 

Cryptosporidium treatment credit of 2.0- 

log. EPA proposed this level of credit for 

cartridge filters but proposed a 1.0-log 

maximum credit for bag filters, as 

recommended by the Advisory 

Committee. However, after further 

reviewing available data, EPA has 

concluded that treatment studies do not 

support establishing different limits on 

treatment credit for bag and cartridge 

filters. Accordingly, today’s rule treats 

bag and cartridge filters equivalently. 

EPA continues to believe that 2.0-log is 

an appropriate maximum treatment 

credit for a single bag or cartridge filter, 

based on available data on the removal 

of Cryptosporidium and surrogates by 

these processes and the absence of a 

direct integrity test. 

Today’s rule also establishes criteria 

for awarding treatment credit to bag or 

cartridge filters operated in series. EPA 

believes that the use of these filters in 

series provides clear advantages in 

comparison to operation of a single 

filter. Series operation will achieve both 

greater removal efficiency and improved 

reliability by lessening the impact of 

variation in the performance of a single 

filter. In consideration of these factors, 

bag or cartridge filters operated in series 

are eligible for a higher 

Cryptosporidium treatment credit of 2.5- 

log and require a lower safety factor of 

0.5-log applied to challenge test results 

when determining treatment credit. 

c. Summary of Major Comments 

In response to the August 11, 2003 

proposal, EPA received significant 

public comment on the following issues 

related to bag and cartridge filtration: 

the allowable treatment credit, the factor 

of safety applied to challenge testing 

results to determine treatment credit, 

and the procedure for determining the 

removal efficiency. A summary of these 

comments and EPA’s responses follows. 

In regard to the proposed treatment 

credits, several commenters 

recommended that bag and cartridge 

filters should be eligible for up to 2.0- 

and 2.5-log credit, respectively, if 

supported by the challenge test results. 

Others commented that filters should be 

allowed to qualify for removal credits at 

or below the 1.0- and 2.0-log credits in 

the proposal. EPA agrees that additional 

flexibility should be provided with 

respect to the removal credit awarded to 

bag and cartridge filters. After reviewing 

these comments and reassessing data 

presented in the proposal on the 

removal efficiencies of bag and cartridge 

filters, EPA revised the proposal to 

allow up to 2.0-log treatment credit for 

either a single bag or cartridge filter. In 

addition, today’s rule allows up to 2.5- 

log credit for bag or cartridge filters 

operated in series. 

With respect to the 1.0-log safety 

factor applied to challenge test results to 

determine treatment credit, some 

commenters supported this approach, 

while others recommended a reduced 

safety factor. In response, EPA 

continues to believe that a 1.0-log safety 

factor is appropriate to address 

variability in individual filter 

performance and in the absence of a 

direct integrity test for bag and cartridge 

filters. Where filters are operated in 

series, however, EPA agrees that the 

safety factor should be reduced. Series 

operation provides an intrinsic process 

safety and will dampen some of the 

variability in removal efficiency 

observed for individual filters. Thus, 

EPA is reducing the factor of safety to 

0.5-log for configurations consisting of 

two or more filters in series. 

Commenters requested that EPA 

clarify the procedure used to determine 

the removal efficiency of bag and 

cartridge filters. In response, expanded 

and clarified guidance on conducting 

challenge tests to determine removal 

efficiency for bag and cartridge filters 

has been included in the Toolbox 

Guidance Manual. 

11. Membrane Filtration 

a. Today’s Rule 

Today’s final rule establishes criteria 

for awarding Cryptosporidium treatment 

credit to membrane filtration processes. 

To receive removal credit, filters must 

meet the definition of a membrane 

filtration process and undergo challenge 

testing to establish removal efficiency; 

PWSs must periodically verify system 

integrity through direct integrity testing 

and perform continuous indirect 

integrity monitoring during use. The 

removal credit awarded to a membrane 

process is based on the removal 

efficiency demonstrated during 

challenge testing and the sensitivity of 

the direct integrity test. 

For the purpose of today’s rule, 

membrane filtration is defined as a 

pressure or vacuum driven separation 

process in which particulate matter 

larger than 1 micrometer is rejected by 

an engineered barrier, primarily through 

a size-exclusion mechanism, and which 

has a measurable removal efficiency of 

a target organism that can be verified 

through the application of a direct 

integrity test. 

Membrane Challenge Testing 

Any membrane filter used to meet the 

treatment requirements of today’s rule 

must undergo challenge testing to 

determine its Cryptosporidium removal 

efficiency. Challenge testing establishes 

the maximum Cryptosporidium 

treatment credit a membrane filtration 

process is eligible to receive, provided 

this value is less than or equal to the 

sensitivity of the direct integrity test, as 

described later in this section. Challenge 

testing for membranes is productspecific, and PWSs that install 

membranes that have successfully 

undergone challenge testing are not 

required to repeat testing at their sites. 

Membrane challenge testing must meet 

the following criteria: 

• Challenge testing must be 

conducted on either an identical fullscale module or a smaller-scale module 

identical in material and similar in 

construction to the membrane modules 

the PWS will use. A module is the 

smallest component of a membrane unit 

in which a specific membrane surface 

area is housed in a device with a filtrate 

outlet structure. 

• Either Cryptosporidium or a 

surrogate that is removed no more 

efficiently than Cryptosporidium must 

be used as the challenge particulate 

during challenge testing. 

• The analytical method used to 

measure removal in the challenge test 

must discretely quantify the specific 

challenge particulate. The maximum 

allowable feed water concentration used 

during a challenge test is 6.5-log (3.16 

× 106) times the detection limit of the 

challenge particulate in the filtrate. 

• Challenge testing must be 

conducted under representative 

hydraulic conditions at the maximum 

design flux and maximum design 

process recovery as specified by the 

manufacturer for the membrane 

filtration process. Flux is defined as the 

throughput of a pressure driven 

membrane process expressed as flow 

per unit of membrane area. Recovery is 

defined as the volumetric percent of 

feed water that is converted to filtrate 

over the course of an operating cycle 

uninterrupted by events such as 

chemical cleaning or a solids removal 

process (i.e., backwashing). 

• The removal efficiency for the 

membrane is determined from the 

results of the challenge test, expressed 

as a log removal value (LRV). A LRV 

must be calculated for each membrane 

module evaluated during the challenge 


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test based on the feed and filtrate 

concentrations of the challenge 

particulate for that module. The 

individual LRVs for each module are 

used to determine the overall removal 

efficiency of the membrane product. If 

fewer than twenty modules are tested, 

the overall removal efficiency is 

assigned a value equal to the lowest of 

the representative LRVs for the various 

modules tested. If twenty or more 

modules are tested, then the overall 

removal efficiency is assigned a value 

equal to the 10th percentile of the 

representative LRVs for the various 

modules tested. 

• As part of the challenge test, a 

quality control release value (QCRV) 

must be established for a nondestructive performance test (e.g., 

bubble point test, diffusive airflow test, 

pressure/vacuum decay test) that 

demonstrates the Cryptosporidium 

removal capability of the membrane 

module. The non-destructive 

performance test must be applied to 

each membrane module a PWS uses in 

order to verify Cryptosporidium 

removal capability. Membrane modules 

that do not meet the established QCRV 

are not eligible for the Cryptosporidium 

removal credit demonstrated during 

challenge testing. 

If a previously tested membrane 

product is modified in a manner that 

could change the removal efficiency of 

the membrane or the applicability of 

non-destructive performance test and 

associated QCRV, the modified 

membrane filter must be challenge 

tested to establish the removal 

efficiency and QCRV. If approved by the 

State, data from challenge testing 

conducted prior to promulgation of 

today’s rule may be considered in lieu 

of additional testing. However, the prior 

testing must have been conducted in a 

manner that demonstrates a removal 

efficiency for Cryptosporidium 

commensurate with the treatment credit 

awarded to the filter. 

Membrane Direct Integrity Testing 

In order to receive Cryptosporidium 

treatment credit for a membrane 

filtration process, PWSs must conduct 

direct integrity testing in a manner that 

demonstrates a removal efficiency equal 

to or greater than the removal credit 

awarded to the membrane filtration 

process. A direct integrity test is defined 

as a physical test applied to a membrane 

unit in order to identify and isolate 

integrity breaches (i.e., one or more 

leaks that could result in contamination 

of the filtrate). 

Each membrane unit must be 

independently direct integrity tested, 

where a membrane unit is defined as a 

group of membrane modules that share 

common valving which allows the unit 

to be isolated from the rest of the system 

for the purpose of integrity testing or 

other maintenance. The direct integrity 

test must be applied to the physical 

elements of the entire membrane unit 

including membranes, seals, potting 

material, associated valving and piping, 

and all other components which under 

compromised conditions could result in 

contamination of the filtrate. 

Common direct integrity tests include 

those that apply pressure or vacuum 

(such as the pressure decay test and 

diffusive airflow test) and those that 

measure the rejection of a particulate or 

molecular marker (such as spiked 

particle monitoring). Today’s final rule 

does not stipulate the use of a particular 

direct integrity test. Instead, the direct 

integrity test must meet performance 

criteria for resolution, sensitivity, and 

frequency. 

‘‘Resolution’’ is defined as the 

smallest leak that contributes to the 

response from a direct integrity test. 

Any direct integrity test applied to meet 

the requirements of this rule must have 

a resolution of 3 micrometers or less. 

The manner in which resolution is 

determined will depend on the type of 

direct integrity test used (i.e., pressurebased versus marker-based tests). 

‘‘Sensitivity’’ is defined as the 

maximum LRV that can be reliably 

verified by the direct integrity test. The 

sensitivity of the direct integrity test 

applied to a membrane filtration process 

to meet the Cryptosporidium treatment 

requirements of this rule must be equal 

to or greater than the removal credit 

awarded to the membrane filtration 

process. Furthermore, the increased 

concentration of suspended solids that 

occurs on the high pressure side of the 

membrane in some module designs 

must be considered in the sensitivity 

determination (i.e., the scouring action 

of some membrane designs keeps the 

accumulated solids in suspension where 

they may pass through an integrity 

breach). Specifically, the sensitivity of 

the direct integrity test is reduced by a 

factor that quantifies the increased 

concentration of suspended solids 

relative to the feed concentration. 

The ‘‘frequency’’ of direct integrity 

testing specifies how often the test is 

performed over an established time 

interval. Direct integrity tests available 

at the time of promulgation are applied 

periodically and must be conducted on 

each membrane unit at a frequency of 

not less than once per day that the unit 

is in operation, unless the State 

determines that less frequent testing is 

acceptable. If continuous direct integrity 

test methods become available that also 

meet the sensitivity and resolution 

criteria described earlier, such a 

continuous test may be used in lieu of 

periodic testing. 

PWSs must establish a direct integrity 

test control limit that is indicative of an 

integral membrane unit capable of 

meeting the Cryptosporidium removal 

credit awarded to the membrane. If the 

control limit for the direct integrity test 

is exceeded, the membrane unit must be 

taken off-line for diagnostic testing and 

repair. The membrane unit may only be 

returned to service after the repair has 

been completed and confirmed through 

the application of a direct integrity test. 

A monthly report must be submitted to 

the State summarizing all direct 

integrity test results above the control 

limit and the corrective action that was 

taken in each case. 

Continuous Indirect Integrity Monitoring 

Available direct integrity test methods 

are applied periodically since the 

membrane unit must be taken out of 

service to conduct the test. In order to 

provide some measure of process 

performance between direct integrity 

testing events, PWSs must perform 

continuous indirect integrity monitoring 

on each membrane unit. Continuous 

indirect integrity monitoring is defined 

as monitoring some aspect of filtrate 

water quality that is indicative of the 

removal of particulate matter at a 

frequency of at least once every 15 

minutes. If a continuous direct integrity 

test is implemented that meets the 

resolution and sensitivity criteria 

described previously in this section, 

continuous indirect integrity monitoring 

is not required. 

Unless the State approves an 

alternative parameter, continuous 

indirect integrity monitoring must 

include continuous filtrate turbidity 

monitoring. If the filtrate turbidity 

readings are above 0.15 NTU for a 

period greater than 15 minutes, the PWS 

must perform direct integrity testing on 

the associated membrane unit. 

If the State approves an alternate 

parameter for continuous indirect 

integrity monitoring, the State must 

approve a control limit for that 

parameter. If the parameter exceeds the 

control limit for a period greater than 15 

minutes, the PWS must perform direct 

integrity testing on the associated 

membrane unit. 

PWSs must submit a monthly report 

to the State summarizing all continuous 

indirect integrity monitoring results 

triggering direct integrity testing and the 

corrective action that was taken in each 

case. 

EPA has developed the Membrane 

Filtration Guidance Manual to assist 


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systems with implementation of these 

requirements. This guidance may be 

requested from EPA’s Safe Drinking 

Water Hotline, which may be contacted 

as described under FOR FURTHER

INFORMATION CONTACT in the beginning 

of this notice. 

b. Background and Analysis 

In the August 11, 2003 proposed 

LT2ESWTR, EPA proposed to establish 

criteria for awarding credit to membrane 

filtration processes for removal of 

Cryptosporidium (USEPA 2003g). The 

Agency based these criteria on data 

demonstrating the Cryptosporidium 

removal efficiency of membrane 

filtration processes, a critical evaluation 

of available integrity monitoring 

techniques, and study of State 

approaches to the regulation of 

membrane filtration for pathogen 

removal. This information is 

summarized in the report Low-Pressure 

Membrane Filtration for Pathogen 

Removal: Application, Implementation, 

and Regulatory Issues (USEPA 2001g). 

As summarized in this report, a 

number of studies demonstrate the 

ability of membrane filtration processes 

to remove pathogens, including 

Cryptosporidium, to below detection 

levels (USEPA 2001g). In some studies 

that used Cryptosporidium seeding, 

measured removal efficiencies were as 

high as 7-log (Jacangelo, et al., 1997; 

Hagen, 1998; Kachalsky and Masterson, 

1993). In other studies, removal 

efficiencies ranged from 4.4- to 6.5-log 

and were only limited by the seeded 

concentration of Cryptosporidium 

oocysts (Dwyer, et al. 1995, Jacangelo et 

al. 1989, Trussel, et al. 1998, NSF 

2000a–g, Olivieri 1989). Collectively, 

these results demonstrate that an 

integral membrane module (i.e., a 

membrane module without any leaks or 

defects, with an exclusion characteristic 

smaller than Cryptosporidium) is 

capable of removing this pathogen to 

below detection in the filtrate, 

independent of the influent 

concentration. 

The 2003 proposal included a 

provision for challenge testing 

membranes to demonstrate the removal 

efficiency of Cryptosporidium. EPA 

believes this requirement is necessary 

due to the proprietary nature of these 

products and the lack of any uniform 

design criteria for establishing the 

exclusion characteristic of a membrane. 

Guidance on the design and conduct of 

a challenge test to meet the 

requirements of this rule is presented in 

the Membrane Filtration Guidance 

Manual. 

Challenge testing is required on a 

product-specific basis, rather than a sitespecific basis; thus, modules used in 

full-scale facilities will generally not be 

directly challenge tested. The removal 

capability of production membrane 

modules is verified through the 

application of a non-destructive 

performance test, such as a bubble point 

test. A quality control release value 

(QCRV) for the non-destructive 

performance test can be related to the 

results of the challenge test and used to 

demonstrate the ability of production 

modules to achieve the 

Cryptosporidium removal efficiency 

demonstrated during challenge testing. 

Most membrane manufacturers have 

adapted some form of non-destructive 

testing for the purpose of product 

quality control and have established a 

QCRV that is indicative of an acceptable 

product. It may be possible to apply 

these existing practices to meet the 

requirements of today’s final rule. 

While challenge testing demonstrates 

the removal efficiency of an integral 

membrane module, defects or leaks in 

the membrane or other system 

components can result in contamination 

of the filtrate unless they are identified, 

isolated, and repaired. In order to verify 

continued performance of a membrane 

system, today’s final rule requires direct 

integrity testing of membrane filtration 

processes used to meet the 

Cryptosporidium treatment 

requirements of this rule. 

An evaluation of available direct 

integrity tests indicates that pressurebased tests are widely applied and 

sufficiently sensitive to provide 

verification of removal efficiencies in 

excess of 4-log. Marker-based direct 

integrity tests are also available, and 

new direct integrity tests may be 

developed that present an improvement 

over existing tests. Rather than specify 

a particular direct integrity test, today’s 

final rule defines performance criteria 

for direct integrity testing. These criteria 

are resolution, sensitivity, and 

frequency, as previously described. EPA 

believes that this approach will provide 

flexibility for the development and 

implementation of future innovations in 

direct integrity testing while ensuring 

that any test applied to meet the 

requirements of this rule will achieve 

the required level of performance. 

Since available direct integrity tests 

require taking the membrane unit out of 

service to conduct the test, today’s rule 

establishes a minimum test frequency 

for direct integrity testing. Currently, 

there is no standard frequency for direct 

integrity testing that has been adopted 

by all States and membrane treatment 

facilities. In a 2000 survey, the required 

frequency of integrity testing was found 

to vary from once every four hours to 

once per week; however, the most 

common frequency for conducting a 

direct integrity test was once every 24 

hours (USEPA 2001g). Specifically, 10 

out of 14 States that require periodic 

direct integrity testing specify a 

frequency of once per day. Furthermore, 

many membrane manufacturers of 

systems with automated integrity test 

systems set up the membrane units to 

automatically perform a direct integrity 

test once per day. 

EPA believes that daily direct 

integrity testing is appropriate for most 

membrane filtration installations, but 

under some circumstances, less frequent 

testing may be adequate. Thus, EPA is 

allowing States to approve less frequent 

direct integrity testing on the basis of 

demonstrated process reliability, use of 

multiple barriers effective for 

Cryptosporidium, or reliable process 

safeguards. 

Due to the periodic nature of direct 

integrity testing, today’s rule includes a 

provision for continuous indirect 

integrity monitoring. While indirect 

monitoring is not as sensitive as direct 

testing, it provides an indication of 

process performance to ensure that a 

major failure has not occurred between 

application of direct integrity tests. 

c. Summary of Major Comments 

In response to the 2003 proposal, the 

Agency received significant comments 

on the following issues related to 

membrane filtration: the frequency of 

direct integrity testing; the procedure 

necessary to determine removal credit 

for membrane filtration; and the 

requirement for continuous indirect 

integrity monitoring. 

The 2003 proposal requested 

comment on the proposed minimum 

direct integrity test frequency of once 

per day. Some commenters supported 

the daily frequency and commented that 

many states have already adopted this 

standard. Others commented that direct 

integrity testing once per day is too 

frequent, citing the lack of data in the 

proposal documenting the rate of 

membrane failure, as well as the loss in 

production that occurs when the 

membrane unit is taken off-line for 

testing. 

While EPA recognizes these concerns, 

a critical factor in establishing a testing 

frequency is the amount of time that 

water from a compromised membrane 

unit is supplied to the public before the 

integrity breach is detected. EPA 

believes that this factor is most 

important to public health protection 

and that daily direct integrity testing is 

appropriate for the majority of 

membrane systems. However, EPA also 

acknowledges that there may be 


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circumstances under which less 

frequent testing may provide adequate 

public health protection, and has 

revised the rule to allow States to permit 

less frequent direct integrity testing 

based on demonstrated process 

reliability, use of multiple barriers 

effective for Cryptosporidium, or 

reliable process safeguards. 

Several commenters expressed 

concern with the process needed to 

determine appropriate removal credit 

for membrane filtration. However, many 

commenters also supported the 

flexibility provided to States in 

determining the appropriate removal 

credit for membrane filtration based on 

the criteria defined in the 2003 

proposal. EPA believes that the 

proposed approach for awarding 

Cryptosporidium removal credit to 

membrane filtration is supported by the 

available data and analysis, and will 

allow higher removal credits to be 

considered on a scientifically sound 

basis. EPA recognizes that the flexibility 

provided in the regulation does increase 

the complexity of determining removal 

credits for membrane filtration. To 

address this issue, EPA has developed 

extensive guidance to support the 

implementation of requirements for 

membrane filtration. 

EPA received comment that 

continuous indirect integrity monitoring 

is unnecessary due to the poor 

sensitivity of currently available 

methods. EPA acknowledges that 

currently available indirect monitoring 

methods are less sensitive than available 

direct integrity tests. However, EPA 

believes that continuous indirect 

integrity monitoring is necessary to 

protect public health. Specifically, 

continuous monitoring may alert a 

system of potentially severe integrity 

breaches that could result in bypass of 

unfiltered water around the membrane 

filtration process and pose a risk to 

public health. Furthermore, EPA has 

provided States with the flexibility to 

permit use of more sensitive continuous 

indirect monitoring methods and/or to 

establish lower control limits. Also, 

implementation of continuous direct 

integrity testing would preclude the 

need to implement any form of indirect 

integrity monitoring. 

12. Second Stage Filtration 

a. Today’s Rule 

PWSs may receive 0.5-log credit 

towards the Cryptosporidium treatment 

requirements of today’s rule for a 

second filtration stage. To be eligible for 

this credit, the second-stage filtration 

must meet the following criteria: 

• The filter must be a separate second 

stage of granular media filtration, such 

as sand, dual media, or granular 

activated carbon (GAC), that follows a 

first stage of granular media filtration 

(e.g., follows a conventional treatment 

or direct filtration plant). 

• The first filtration stage must be 

preceded by a coagulation process. 

• Both filtration stages must treat 100 

percent of the treatment plant flow. 

• The State must approve the 

treatment credit based on an assessment 

of the design characteristics of the 

filtration process. 

This microbial toolbox option does 

not apply to bag filters, cartridge filters, 

membranes, or slow sand filters, which 

are addressed separately in the 

microbial toolbox. Further, this options 

does not apply to roughing filters, 

which are pretreatment processes that 

typically consist of coarse media and are 

not preceded by coagulation. States may 

consider awarding treatment credit to 

roughing filters under a demonstration 

of performance. 

PWSs may not receive additional 

treatment credit for both second-stage 

filtration and lower filter effluent 

turbidity (i.e., combined or individual 

filter performance) that is based on 

turbidity levels following the second 

filtration stage. PWSs may receive credit 

for both options based on turbidity 

following the first filtration stage. 

b. Background and Analysis 

The Stage 2 M–DBP Advisory 

Committee recommended a 0.5-log 

Cryptosporidium treatment credit for a 

roughing filter with the stipulation that 

EPA identify the design and operational 

conditions under which such credit is 

appropriate. After reviewing available 

data, however, EPA was unable to 

determine conditions under which a 

roughing filter is likely to achieve at 

least 0.5-log removal of 

Cryptosporidium. Roughing filters 

consist of coarse media like gravel and 

usually are not preceded by coagulation. 

They are used to remove sediment and 

large particulate matter from raw water 

prior to the primary treatment 

processes. EPA identified no studies 

indicating that roughing filters would be 

effective for removal of 

Cryptosporidium (USEPA 2003a). 

In contrast, numerous studies have 

demonstrated that granular media 

filtration can be effective for removing 

Cryptosporidium when preceded by 

coagulation (Patania et al. 1995, 

Nieminski and Ongerth 1995, Ongerth 

and Pecoraro 1995, LeChevallier and 

Norton 1992, LeChevallier et al. 1991, 

Dugan et al. 2001, Nieminski and 

Bellamy 2000, McTigue et al. 1998, 

Patania et al. 1999, Huck et al. 2000, 

Emelko et al. 2000). PWSs may 

implement a second granular media 

filtration stage to achieve various water 

quality objectives, such as increased 

removal of organic material in 

biologically active filters or removal of 

inorganic contaminants. Consequently, 

EPA believes that consideration of 

additional Cryptosporidium treatment 

credit for a second granular media 

filtration stage is appropriate. 

The August 11, 2003 LT2ESWTR 

proposal included an additional 0.5-log 

Cryptosporidium treatment credit for 

PWSs that use a second separate 

filtration stage consisting of rapid sand, 

dual media, GAC, or other fine grain 

media. A cap, such as GAC, on a single 

stage of filtration did not qualify. In 

addition, the proposal required the first 

stage of filtration to be preceded by a 

coagulation step and both stages had to 

treat 100 percent of the plant flow. 

Today’s final rule establishes this 

treatment credit with minimal changes 

from the proposal. The basis for this 

credit and for changes from the 

proposed rule are summarized in the 

following discussion. 

While the studies of Cryptosporidium 

removal by granular media filtration 

cited previously evaluated only a single 

stage of filtration, the same removal 

mechanisms will be operative in a 

second stage of granular media 

filtration. Secondary filters may remove 

Cryptosporidium that were destabilized 

but not trapped in primary filters or that 

were trapped but subsequently detached 

from primary filters prior to backwash. 

Thus, EPA believes these studies are 

supportive of additional removal credit 

for a second filtration stage. 

An important finding of these studies 

is that coagulation is necessary to 

achieve significant Cryptosporidium 

removal by granular media filtration 

(does not apply to slow sand filtration, 

which is addressed in the next section). 

Consequently, today’s rule requires that 

the first filtration stage be preceded by 

coagulation for a PWS to receive 

treatment credit for second-stage 

filtration. This requirement is necessary 

to ensure that both filtration stages are 

effective for Cryptosporidium removal. 

PWSs will already comply with this 

requirement where a second filtration 

stage is applied after conventional 

treatment or direct filtration. 

In the proposal, EPA also reviewed 

data provided by a PWS on the removal 

of aerobic spores through GAC filters 

(i.e., contactors) following conventional 

treatment. As discussed earlier, studies 

have demonstrated that aerobic spores 

can serve as an indicator of 

Cryptosporidium removal by granular 


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media filtration (Dugan et al. 2001, 

Emelko et al. 1999 and 2000, Yates et al. 

1998, Mazounie et al. 2000). Over a two 

year period, the mean removal of 

aerobic spores across the GAC filters 

exceeded 0.5-log. These results support 

the finding that a second stage of 

granular media filtration can reduce 

Cryptosporidium levels by 0.5-log or 

greater. 

Today’s rule does not establish design 

criteria such as filter depth or media 

size for second-stage filters to be eligible 

for treatment credit. While filter design 

will influence Cryptosporidium removal 

efficiency, EPA recognizes that 

appropriate filter designs will vary 

depending on the application. States 

have traditionally provided oversight for 

treatment process designs in PWSs. 

Accordingly, today’s rule requires State 

review and approval of second-stage 

filter design as a condition for PWSs to 

receive additional treatment credit for 

this process. The Microbial Toolbox 

Guidance Manual addresses secondstage filtration for Cryptosporidium 

treatment credit. 

c. Summary of Major Comments 

Public comment on the August 11, 

2003 LT2ESWTR proposal generally 

supported additional treatment credit 

for second-stage filtration. Commenters 

raised specific concerns with EPA 

establishing design requirements for 

filtration, the sufficiency of data to 

support prescribed treatment credit, and 

the expansion of this credit to include 

other filtration technologies. These 

comments and EPA’s responses are 

summarized as follows. 

In the proposal, EPA requested 

comment on whether a minimum filter 

depth should be required for PWSs to 

receive treatment credit for a second 

filtration stage. All commenters opposed 

EPA setting regulatory design standards 

for filters on the basis that PWSs and 

States need the flexibility to determine 

appropriate treatment designs. In 

response, EPA agrees that effective filter 

designs will vary depending on the 

application. Consequently, EPA is not 

establishing filter design criteria in 

today’s rule, but is requiring that States 

approve designs for PWSs to receive 

treatment credit for second-stage 

filtration. 

Many commenters stated that 

available data support the prescribed 

0.5-log Cryptosporidium treatment 

credit for second-stage filtration. Some 

commenters provided additional data 

on the removal of aerobic spores 

through GAC filters following 

conventional treatment that showed a 

mean reduction greater than 1-log. In 

contrast, other commenters were 

concerned about the lack of data to 

support increased removal through a 

second filtration stage. These 

commenters recommended that 

treatment credit for second-stage 

filtration should be awarded only on a 

site-specific basis through a 

demonstration of performance. 

EPA has concluded that available data 

are sufficient to support the prescribed 

0.5-log treatment credit for second-stage 

filtration. Studies of granular media 

filtration demonstrate high levels of 

Cryptosporidium removal and one study 

has shown greater than 1.0-log removal 

through secondary GAC filters. 

Secondary filters can remove 

Cryptosporidium that pass through or 

detach from the primary filters. This 

added removal will help to stabilize 

finished water quality by providing a 

barrier during periods of the filtration 

cycle when the primary filters are not 

performing optimally. Therefore, EPA is 

establishing this credit in today’s rule. 

Several commenters recommended 

that EPA expand the second-stage 

filtration option to include membranes, 

bag filters, and DE filtration. EPA notes 

that today’s rule establishes prescribed 

treatment credits specifically for bag 

and cartridge filters and membranes as 

microbial toolbox options, and 

prescribed credit for DE filtration is 

addressed in section IV.B. PWSs may 

seek treatment credit for other filtration 

technologies through a demonstration of 

performance under today’s rule. 

13. Slow Sand Filtration 

a. Today’s Rule 

PWSs may receive a 2.5-log credit 

towards the Cryptosporidium treatment 

requirements in today’s rule for 

implementing slow sand filtration as a 

secondary filtration stage following a 

primary filtration process. To be eligible 

for this credit, the slow sand filtration 

must meet the following criteria: 

• The slow sand filter must be a 

separate second stage of filtration that 

follows a first stage of filtration like 

conventional treatment or direct 

filtration; 

• There must be no disinfectant 

residual in the influent water to the 

slow sand filtration process; 

• Both filtration stages must treat 100 

percent of the treatment plant flow from 

a surface water or GWUDI source; and 

• The State must approve the 

treatment credit based on an assessment 

of the design characteristics of the 

filtration process. 

Slow sand filtration used as a primary 

filtration process receives a prescribed 

3-log Cryptosporidium treatment credit, 

as described in section IV.B. 

b. Background and Analysis 

Slow sand filtration is a process 

involving passage of raw water through 

a bed of sand at low velocity (generally 

less than 0.4 m/h), resulting in 

substantial particulate removal. Several 

studies have demonstrated that slow 

sand filtration can achieve significant 

Cryptosporidium removal (Schuler and 

Ghosh, 1991, Timms et al. 1995, Hall et 

al. 1994). Slow sand filtration is 

typically used as a primary filtration 

process, usually in small systems, rather 

than as a secondary filtration stage 

following conventional treatment or 

another primary filtration process. EPA 

expects, however, that slow sand 

filtration would be effective for 

Cryptosporidium removal in such an 

application, which warrants 

consideration of treatment credit under 

today’s rule. 

The Stage 2 M–DBP Advisory 

Committee recommended that slow 

sand filtration receive 2.5-log or greater 

Cryptosporidium treatment credit when 

used in addition to existing treatment 

that achieves compliance with the 

IESWTR or LT1ESWTR. The August 11, 

2003 LT2ESWTR proposal included 2.5- 

log treatment credit for slow sand as a 

secondary filtration process, with the 

only associated condition being no 

disinfectant residual in the water 

influent to the filter. In today’s rule, 

EPA is establishing this treatment credit 

with minimal changes from the 

proposal. The following discussion 

summarizes the basis for this credit and 

for changes from the proposal. 

Removal of microbial pathogens in 

slow sand filters is complex and is 

believed to occur through a combination 

of physical, chemical, and biological 

mechanisms, both on the surface and in 

the interior of the filter bed. In 

particular, biological activity in the 

upper layers of the filter is believed to 

promote microbial removal. Based on 

previously cited studies demonstrating 

greater than 4-log removal of 

Cryptosporidium through slow sand 

filtration, today’s rule awards a 

prescribed 3-log Cryptosporidium 

removal credit to slow sand filtration as 

a primary filtration process. 

The effectiveness of slow sand as a 

secondary filtration process is more 

uncertain. In general, EPA expects that 

the same microbial removal 

mechanisms will be operative. However, 

due to the quality of treated water 

following a primary filtration process, 

filter ripening and development of the 

biologically active layer in a secondary 

slow sand filter may be inhibited. One 

study that evaluated Cryptosporidium 

removal by slow sand filtration alone 


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and slow sand filtration preceded by a 

rapid sand filter observed similar 

removal levels in the two treatment 

trains (Hall et al. 1994). Because of the 

uncertainty regarding the performance 

of slow sand as a secondary filtration 

step and in consideration of the 

Advisory Committee recommendation, 

today’s rule establishes a 2.5-log 

additional Cryptosporidium treatment 

credit for this application. 

Due to the importance of biological 

activity to slow sand filter performance, 

PWSs may not receive the prescribed 

treatment credit if the influent water to 

the slow sand filter contains a 

disinfectant residual. EPA is not 

establishing design standards for slow 

sand filters in today’s rule. Studies have 

shown, however, that design 

deficiencies in slow sand filters may 

lead to poor Cryptosporidium removal 

(Fogel et al. 1993). Consequently, States 

must approve slow sand filter designs as 

a secondary filtration stage for PWSs to 

receive treatment credit under today’s 

rule. 

c. Summary of Major Comments 

Public comment on the August 11, 

2003 proposal focused on the question 

of whether the 2.5-log Cryptosporidium 

treatment credit for slow sand as a 

secondary filtration process is 

appropriate. Many commenters 

supported the proposed treatment 

credit. These commenters cited studies 

demonstrating greater than 4-log 

Cryptosporidium removal by slow sand 

filtration and concluded that the data 

justify a 2.5-log treatment credit for slow 

sand filtration added to a clarification 

and filtration treatment train. 

Several commenters, however, stated 

that this treatment credit is not justified 

due to the lack of data on the 

performance of slow sand as a 

secondary filtration step. Available 

studies on slow sand filter performance 

for Cryptosporidium removal have 

mostly been conducted on raw (i.e., 

unfiltered) water. These commenters 

were concerned that if slow sand 

filtration is applied following a primary 

filtration process, the filter ripening 

period and other factors will be 

significantly affected. As a result, the 

slow sand filtration may provide only 

limited removal over a long ripening 

period. 

In response, EPA recognizes that little 

testing has been conducted on the 

performance of slow sand filtration 

specifically as a second filtration stage 

in a treatment train. However, available 

data do not indicate that slow sand 

filtration would be substantially less 

effective when used in this capacity. 

Slow sand filtration is recommended 

only for higher quality source waters, 

and water quality following a primary 

filtration process would be well within 

recommended design limits for slow 

sand filtration (USEPA 1991a). EPA 

agrees that filter ripening is critical to 

slow sand filtration achieving its full 

performance level, and this process may 

require more time when slow sand 

filtration follows a primary filtration 

process. However, this effect may be 

counterbalanced by very long filter run 

times between cleaning the filter due to 

the high quality influent water. 

Consequently, EPA believes that 2.5-log 

Cryptosporidium treatment credit for 

slow sand as a secondary filtration 

process is warranted. 

14. Ozone and Chlorine Dioxide 

a. Today’s Rule 

PWSs may use ozone and chlorine 

dioxide to meet Cryptosporidium 

treatment requirements under today’s 

rule. To receive treatment credit, PWSs 

must measure the water temperature, 

disinfectant contact time, and residual 

disinfectant concentration at least once 

each day and determine the log 

inactivation credit using the tables in 

this section. Specific criteria are as 

follows: 

• The temperature of the disinfected 

water must be measured at least once 

per day at each residual disinfectant 

concentration sampling point. 

• The disinfectant contact time(s) 

(‘‘t’’) must be determined for each day 

during peak hourly flow. 

• The residual disinfectant 

concentration(s) (‘‘C’’) of the water 

before or at the first customer must be 

measured each day during peak hourly 

flow. 

• Tables IV.D–3 or IV.D–4 must be 

used to determine Cryptosporidium log 

inactivation credit for ozone or chlorine 

dioxide, respectively, based on the 

water temperature and the product of 

disinfectant concentration and contact 

time (CT). 

TABLE IV.D–3.—CT VALUES FOR CRYPTOSPORIDIUM INACTIVATION BY OZONE 1 (MG/L × MIN) 

Log credit 

Water temperature, °C 

≤0.5 1 2 3 5 7 10 15 20 25 30 

0.25 ............................ 6 .0 5 .8 5 .2 4 .8 4 .0 3 .3 2 .5 1 .6 1 .0 0 .6 0 .39 

0.5 .............................. 12 12 10 9 .5 7 .9 6 .5 4 .9 3 .1 2 .0 1 .2 0 .78 

1.0 .............................. 24 23 21 19 16 13 9 .9 6 .2 3 .9 2 .5 1 .6 

1.5 .............................. 36 35 31 29 24 20 15 9 .3 5 .9 3 .7 2 .4 

2.0 .............................. 48 46 42 38 32 26 20 12 7 .8 4 .9 3 .1 

2.5 .............................. 60 58 52 48 40 33 25 16 9 .8 6 .2 3 .9 

3.0 .............................. 72 69 63 57 47 39 30 19 12 7 .4 4 .7 

1PWSs may use this equation to determine log credit between the indicated values: Log credit = (0.0397 × (1.09757) Temp) × CT. 

TABLE IV.D–4.—CT VALUES FOR CRYPTOSPORIDIUM INACTIVATION BY CHLORINE DIOXIDE 1 (MG/L × MIN) 

Log credit 

Water temperature, °C 

≤0.5 1 2 3 5 7 10 15 20 25 30 

0.25 ............................ 159 153 140 128 107 90 69 45 29 19 12 

0.5 .............................. 319 305 279 256 214 180 138 89 58 38 24 

1.0 .............................. 637 610 558 511 429 360 277 179 116 75 49 

1.5 .............................. 956 915 838 767 643 539 415 268 174 113 73 

2.0 .............................. 1275 1220 1117 1023 858 719 553 357 232 150 98 

2.5 .............................. 1594 1525 1396 1278 1072 899 691 447 289 188 122 

3.0 .............................. 1912 1830 1675 1534 1286 1079 830 536 347 226 147 

1PWSs may use this equation to determine log credit between the indicated values: Log credit = (0.001506 × (1.09116) Temp) × CT. 


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PWSs may have several disinfection 

segments in sequence along the 

treatment train, where a disinfectant 

segment is defined as a treatment unit 

process with a measurable disinfectant 

residual level and a liquid volume. In 

determining the total log inactivation, 

the PWS may calculate the CT for each 

disinfection segment and use the sum of 

these values to determine the log 

inactivation achieved through the plant. 

The Toolbox Guidance Manual provides 

information on recommended 

methodologies for determining CT 

values for different disinfection reactor 

designs and operations. 

Alternatively, the State may approve 

alternative CT values to those specified 

in Tables IV.D–3 or IV.D–4 based on a 

site-specific study a PWSs conducts 

following a State-approved protocol. 

The Toolbox Guidance Manual 

describes recommended approaches for 

making such demonstrations. 

b. Background and Analysis 

Ozone and chlorine dioxide are 

chemical disinfectants that have been 

shown to be effective for inactivating 

Cryptosporidium. The Stage 2 M–DBP 

Advisory Committee recommended that 

EPA develop criteria for PWSs to 

achieve Cryptosporidium inactivation 

credit with these disinfectants. The 

August 11, 2003 LT2ESWTR proposal 

included CT values for 0.5- to 3-log 

Cryptosporidium inactivation credit by 

ozone or chlorine dioxide at 

temperatures ranging from less than 0.5 

C to 25 C, along with daily required 

monitoring (USEPA 2003a). Today’s 

final rule establishes these criteria with 

no changes from the proposed rule, but 

expands the CT tables down to 0.25-log 

inactivation and up to a water 

temperature of 30 C. The following 

discussion summarizes the basis for 

these criteria. 

The requirements for at least daily 

monitoring of the water temperature, 

residual disinfectant concentration, and 

contact time during peak hourly flow to 

determine a daily inactivation level 

reflect existing requirements for Giardia 

inactivation by chemical disinfection in 

40 CFR 141.74. EPA expects that in 

practice, many PWSs using ozone or 

chlorine dioxide will monitor more 

frequently and for multiple disinfectant 

segments. In the Toolbox Guidance 

Manual, EPA provides information on 

recommended approaches for 

monitoring and calculating CT values 

for ozone and chlorine dioxide reactors. 

The CT values for both ozone and 

chlorine dioxide are based on analyses 

by Clark et al. (2002a,b), with additional 

procedures to assess confidence bounds. 

Clark et al. (2002a,b) developed 

predictive equations for 

Cryptosporidium inactivation through 

evaluating studies on ozone by 

Rennecker et al. (1999), Li et al. (2001), 

Owens et al. (2000), and Oppenheimer 

et al. (2000) and on chlorine dioxide by 

Li et al. (2001), Owens et al. (1999) and 

Ruffell et al. (2000). EPA applied 

confidence bounds to these predictive 

equations to ensure that PWSs operating 

at a given CT value are likely to achieve 

at least the corresponding log 

inactivation level in the CT table. 

In identifying confidence bounds for 

CT values, EPA was primarily 

concerned with uncertainty in the 

estimations by Clark et al. (2002a,b) of 

the linear relationship between log 

inactivation and CT (i.e., uncertainty in 

the regression) and with real variability 

in the inactivation rate. Such real 

variability could be associated with 

different populations of oocysts and 

different water matrices. In contrast, 

variability associated with experimental 

error, such as the assays used to 

measure loss of infectivity, was a lessor 

concern. The purpose of the CT tables 

is to ensure a given level of inactivation 

and not to predict the measured result 

of an individual experiment. 

For developing earlier CT values, EPA 

has used bounds for confidence in 

prediction, which account for both real 

variability and experimental error. EPA 

believes that this approach was 

appropriate due to limited inactivation 

data and uncertainty in the sources of 

variability in the data. However, the 

high doses of ozone and chlorine 

dioxide necessary to inactivate 

Cryptosporidium create an offsetting 

concern with the formation of DBPs 

(e.g., bromate and chlorite). In 

consideration of this concern, EPA has 

employed a less conservative method to 

calculate confidence bounds for the 

ozone and chlorine dioxide CT values in 

today’s rule; specifically, EPA has 

attempted to exclude experimental error 

from the confidence bounds. 

In order to estimate confidence 

bounds that exclude experimental error, 

EPA assessed the relative contribution 

of experimental error to the variance 

observed in the Cryptosporidium 

inactivation data sets. This assessment 

was done by comparing variance among 

data points with consistent 

experimental conditions, which was 

attributed to experimental error, with 

the total variance in a data set. By this 

analysis, EPA estimated that 87.5 and 62 

percent of the variance in the 

Cryptosporidium inactivation data for 

ozone and chlorine dioxide, 

respectively, could be ascribed to 

experimental error (Sivaganesan 2003, 

Messner 2003). EPA then applied these 

estimates to the predictive equations 

developed by Clark et al. (2002a,b) 

using a modified form of a formula for 

calculating a 90 percent confidence 

bound (Messner 2003). 

This analysis produced the CT values 

shown in tables IV.D–3 and IV.D–4 for 

ozone and chlorine dioxide, 

respectively. CT values are provided for 

inactivation as low as 0.25-log. Such a 

low inactivation level may be used by 

PWSs applying ozone in combination 

with other disinfectants. Available data 

do not support the determination of 

conditions for inactivation greater than 

3-log, so the CT values in today’s rule 

do not go beyond this level. The 

temperature range of CT values in 

today’s rule goes to 30 C (86 F), which 

will accommodate most natural waters. 

If the water temperature is higher than 

30 C, temperature should be set to 30 C 

for the log inactivation calculation. 

PWSs may use the equations provided 

as footnotes to tables IV.D–3 and IV.D–

4 to interpolate between CT values. 

EPA recognizes that inactivation rates 

may be sensitive to water quality and 

operational conditions at individual 

PWSs. To reflect this potential, PWSs 

are allowed to perform a site-specific 

inactivation study to determine CT 

requirements. The State must approve 

the protocols or other information used 

to derive alternative CT values. EPA has 

provided guidance for such studies in 

the Toolbox Guidance Manual. 

c. Summary of Major Comments 

Public comment on the August 11, 

2003 LT2ESWTR proposal supported 

the inclusion of ozone and chlorine 

dioxide in the microbial toolbox for 

Cryptosporidium inactivation. 

Commenters stated concerns with the 

required criteria for achieving 

Cryptosporidium treatment credit, 

including the conservatism EPA applied 

in developing the CT tables, the ability 

of PWSs with different types of source 

waters to use these disinfectants, and 

the range of conditions covered by the 

CT tables. Commenters also made 

recommendations for guidance. These 

comments and EPA’s responses are 

summarized as follows. 

Some commenters supported the 

proposed CT tables, but others stated 

that the statistical approach used to 

calculate the confidence bounds from 

which the CT values are derived is 

overly conservative. These commenters 

were concerned that this approach will 

increase capital and operating costs and 

lead to higher byproduct levels. 

In response, EPA believes that the 

confidence bounds used for the ozone 

and chlorine dioxide CT tables in 

today’s rule are appropriate and 


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necessary to ensure that PWSs achieve 

intended levels of Cryptosporidium 

inactivation. They account only for 

uncertainty in the regression of 

inactivation data and for variability in 

inactivation data that cannot be 

attributed to experimental error. This 

approach is significantly less 

conservative than the approaches used 

in CT tables for earlier rules. EPA 

employed this less conservative 

approach in recognition of the high 

disinfectant doses necessary for 

Cryptosporidium inactivation and 

concern with byproducts. 

Commenters were concerned that due 

to the relatively high ozone and chlorine 

dioxide doses necessary for 

Cryptosporidium inactivation, some 

PWSs will be unable to use these 

disinfectants to achieve required levels 

of Cryptosporidium treatment. In 

particular, using ozone for high 

Cryptosporidium inactivation levels 

will be difficult in areas where cold 

water temperatures would necessitate 

especially high doses or where high 

source water bromide levels would 

cause problems with bromate formation. 

The use of chlorine dioxide for 

Cryptosporidium inactivation may be 

difficult due to chlorite formation. 

EPA recognizes that the use of ozone 

and chlorine dioxide to achieve 

Cryptosporidium inactivation will 

depend on source water factors and will 

not be feasible for all PWSs. Due to the 

availability of UV, which EPA has 

determined to be a feasible technology 

for Cryptosporidium inactivation by all 

PWS sizes, the feasibility of today’s rule 

does not depend on the widespread use 

of ozone or chlorine dioxide for 

compliance. In assessing the impact of 

today’s rule on PWSs, EPA used ICR 

survey data to estimate the fraction of 

PWSs that could use ozone or chlorine 

dioxide to achieve different levels of 

Cryptosporidium inactivation without 

exceeding DBP MCLs (see Economic 

Analysis for the LT2ESWTR). While 

EPA expects that some PWSs will use 

these disinfectants, the microbial 

toolbox provides many other options for 

PWSs to comply with the 

Cryptosporidium treatment 

requirements of today’s rule. 

Commenters recommended that EPA 

expand the range of conditions 

encompassed in the CT tables. 

Specifically, commenters asked that CT 

tables include values for water 

temperatures above 25 C and supported 

this request by providing data showing 

temperature profiles for water sources 

with maximum temperatures near 30 C. 

Commenters also requested CT values 

for Cryptosporidium inactivation levels 

below 0.5-log for PWSs that will use 

multiple disinfectants to meet the 

treatment requirements in today’s rule. 

In addition, commenters suggested that 

EPA provide equations that PWSs can 

use to interpolate between the listed CT 

values. 

EPA has addressed these 

recommendations in today’s final rule. 

The CT tables for ozone and chlorine 

dioxide include values for a water 

temperature of 30 C and for 0.25-log 

inactivation. Footnotes to these tables 

contain equations that PWSs can use to 

calculate log inactivation credit for 

conditions between those provided in 

the tables. PWSs may use these 

equations in their process control 

systems. 

Commenters made recommendations 

for guidance on the use of ozone and 

chlorine dioxide to comply with today’s 

rule. These recommendations concern 

topics like monitoring disinfection 

reactors, procedures for calculating 

disinfectant concentration and contact 

time, site specific studies, and 

synergistic effects of multiple 

disinfectants. EPA has addressed these 

topics in the Toolbox Guidance Manual. 

15. Ultraviolet Light 

a. Today’s Rule 

PWSs may use ultraviolet (UV) light 

to comply with Cryptosporidium 

treatment requirements in today’s rule, 

as well as Giardia lamblia and virus 

treatment requirements in existing 

regulations. To receive treatment credit, 

PWSs must operate UV reactors 

validated to achieve the required UV 

dose, as shown in the table in this 

section, and monitor their UV reactors 

to demonstrate operation within 

validated conditions. Specific criteria 

are as follows: 

Required UV Doses 

• UV dose (fluence) is the product of 

the UV intensity over a surface area 

(fluence rate) and the exposure time. 

PWSs must use validation testing to 

demonstrate that a UV reactor achieves 

the UV doses shown in Table IV.D–5 in 

order to receive the associated 

inactivation credit. 

TABLE IV.D–5.—UV DOSE REQUIREMENTS FOR CRYPTOSPORIDIUM, GIARDIA LAMBLIA, AND VIRUS INACTIVATION CREDIT

Log credit Cryptosporidium UV 

dose (mJ/cm2) 

Giardia lamblia UV 

dose (mJ/cm2) 

Virus UV dose (mJ/ 

cm2) 

0.5 ........................................................................................................ 1 .6 1 .5 39 

1.0 ........................................................................................................ 2 .5 2 .1 58 

1.5 ........................................................................................................ 3 .9 3 .0 79 

2.0 ........................................................................................................ 5 .8 5 .2 100 

2.5 ........................................................................................................ 8 .5 7 .7 121 

3.0 ........................................................................................................ 12 11 143 

3.5 ........................................................................................................ 15 15 163 

4.0 ........................................................................................................ 22 22 186 

• The dose values in Table IV.D–5 are 

for UV light at a wavelength of 254 nm 

as delivered by a low pressure mercury 

vapor lamp. However, PWSs may use 

this table to determine treatment credits 

for other lamp types through validation 

testing, as described in the UV 

Disinfection Guidance Manual. The 

dose values in Table IV.D–5 apply to 

post-filter applications of UV in 

filtration plants and to PWSs that meet 

all applicable filtration avoidance 

criteria. 

UV Reactor Validation Testing 

• The validation test may be reactorspecific or site-specific. Unless the State 

approves an alternative approach, this 

testing must involve the following: (1) 

Full scale testing of a reactor that 

conforms uniformly to the UV reactors 

used by the PWS, and (2) inactivation of 

a test microorganism whose dose 

response characteristics have been 

quantified with a low pressure mercury 

vapor lamp. 

• Validation testing must identify 

ranges for parameters the PWS can 

monitor to ensure that the required UV 

dose is delivered during operation. 

These parameters must include flow 

rate, UV intensity as measured by UV 

sensors, and UV lamp status. 

• The operating parameters 

determined by validation testing must 


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account for the following factors: (1) UV 

absorbance of the water, (2) lamp 

fouling and aging, (3) measurement 

uncertainty of UV sensors, (4) dose 

distributions arising from the flow 

velocity profiles through the reactor, (5) 

failure of UV lamps or other critical 

system components, and (6) inlet and 

outlet piping or channel configurations 

of the UV reactor. In the UV 

Disinfection Guidance Manual, EPA 

describes recommended approaches for 

reactor validation that address these 

factors. 

UV Reactor Monitoring 

• PWSs must monitor for the 

parameters necessary to demonstrate 

operation within the validated 

conditions of the required UV dose. 

These parameters must include flow 

rate, UV intensity as measured by UV 

sensors, and UV lamp status. PWSs 

must check the calibration of UV 

sensors and recalibrate in accordance 

with a protocol approved by the State. 

• For PWSs using UV light to meet 

microbial treatment requirements, at 

least 95 percent of the water delivered 

to the public every month must be 

treated by UV reactors operating within 

validated conditions for the required UV 

dose. 

b. Background and Analysis 

Numerous studies have demonstrated 

that UV light is effective for inactivating 

Cryptosporidium, Giardia lamblia, and 

other microbial pathogens at relatively 

low doses (Clancy et al. 1998, 2000, 

2002, Bukhari et al. 1999, Craik et al. 

2000, 2001, Landis et al. 2000, Sommer 

et al. 2001, Shin et al. 2001, and 

Oppenheimer et al. 2002). EPA has 

determined that UV light is a feasible 

technology for PWSs of all sizes to 

inactivate Cryptosporidium. 

Accordingly, EPA expects that UV is 

one of the primary technologies PWSs 

will use to comply with 

Cryptosporidium treatment 

requirements in today’s rule. 

The Stage 2 M–DBP Advisory 

Committee recommended that EPA 

establish standards for the use of UV to 

comply with drinking water treatment 

requirements. These standards include 

the UV doses necessary for different 

levels of Cryptosporidium, Giardia 

lamblia, and virus inactivation and a 

protocol for validating the disinfection 

performance of UV reactors. The 

Committee also directed EPA to develop 

a UV disinfection guidance manual to 

familiarize States and PWSs with 

important design and operational issues 

for UV installations. 

The August 11, 2003 LT2ESWTR 

proposal included UV doses for PWSs to 

achieve treatment credit of up to 3-log 

for Cryptosporidium and Giardia 

lamblia and up to 4-log for viruses, 

along with associated reactor validation 

and monitoring requirements. The 

proposal also required unfiltered PWSs 

using UV to achieve the UV dose for the 

required level of Cryptosporidium 

inactivation in at least 95 percent of the 

water delivered to the public every 

month (USEPA 2003a). 

Today’s final rule establishes these 

criteria with no changes from the 

proposed rule. However, EPA has 

expanded the UV dose table to include 

4-log inactivation of Cryptosporidium 

and Giardia lamblia and has expanded 

the 95 percent compliance requirement 

to include filtered PWSs and to cover 

Giardia lamblia and virus inactivation. 

The following discussion summarizes 

the basis for these criteria. 

The UV dose values in Table IV.D–5 

are based on meta-analyses of UV 

inactivation studies with 

Cryptosporidium parvum, Giardia 

lamblia, Giardia muris, and adenovirus 

(Qian et al. 2004, USEPA 2003a). EPA 

has expanded the dose values for 

Cryptosporidium and Giardia lamblia 

from 3- to 4-log inactivation because 

available data support criteria for this 

level of treatment. Neither today’s rule 

nor any existing regulations require 

PWSs to provide Cryptosporidium 

inactivation above this level, so EPA has 

not expanded the UV dose tables 

further. While today’s rule requires up 

to 5.5-log Cryptosporidium treatment by 

filtered PWSs, at least 2.0-log of this 

treatment must be achieved by physical 

removal. 

The required UV doses for 

inactivation of viruses are based on the 

dose-response of adenovirus because 

among waterborne pathogenic viruses 

that have been studied, it appears to be 

the most UV resistant. As summarized 

in Embrey (1999), adenoviruses have 

been identified as the second most 

important agent of gastroenteritis in 

children and can cause significant 

adverse health effects, including death, 

in persons with compromised immune 

systems. They are associated with fecal 

contamination in water and have been 

implicated in waterborne disease 

outbreaks. 

EPA used data from studies 

performed with low pressure mercury 

vapor lamps on water with turbidity 

representative of filtered water to derive 

the UV dose values in Table IV.D–5. 

Studies with low pressure mercury 

vapor lamps were selected because they 

allow the UV dose to be accurately 

quantified (see USEPA 2003a for 

specific studies). The UV dose values in 

Table IV.D–5 can be applied to medium 

pressure mercury vapor lamps and other 

lamp types through UV reactor 

validation testing, as described in the 

UV Disinfection Guidance Manual. Due 

to the potential for particulate matter to 

interfere with UV disinfection, the 

application of these dose values is 

limited to post-filtration in filtered 

PWSs and to unfiltered PWSs. 

Flow-through UV reactors deliver a 

distribution of doses due to variations in 

light intensity and particle flow path 

through the reactor. To best account for 

the dose distribution, the validation test 

must use a challenge microorganism to 

determine the degree of inactivation 

achieved by the UV reactor. This level 

of performance must then be associated 

to the UV dose requirements in Table 

IV.D–5 through known dose-response 

relationships for the challenge 

microorganism and target pathogen in 

order to assign disinfection credit to the 

UV reactor. States may approve an 

alternative basis for awarding UV 

disinfection credit. 

Today’s rule requires full-scale testing 

of UV reactors to validate the operating 

conditions under which the reactors can 

deliver a required UV dose. EPA 

believes this testing is necessary due to 

the uncertainty associated with 

predicting reactor disinfection 

performance entirely through modeling 

or through reduced-scale testing. Under 

today’s rule, EPA intends UV reactor 

validation testing to be reactor-specific 

and not site-specific. This means that 

once a UV reactor has been validated for 

a range of operating conditions, the 

validation test results can be applied by 

all PWSs that will operate within those 

conditions without the need for 

retesting at each individual site. 

Validation testing must account for 

factors that will influence the dose 

delivered by UV reactors during routine 

operation. These factors include UV 

absorbance, lamp fouling, lamp aging, 

the performance of UV intensity 

sensors, hydraulic flow path and 

residence time distributions, UV lamp 

failure, and reactor inlet and outlet 

hydraulics. The successful outcome of 

validation testing is the determination 

of acceptable operating ranges for 

parameters the PWSs can monitor to 

ensure delivery of the required UV dose 

during treatment. The specific 

parameters will vary depending on the 

reactor control strategy. In all cases, 

however, PWSs must monitor UV 

intensity within the reactor as measured 

by UV sensors, the flow rate, and the 

status of lamps. EPA believes that any 

effective UV reactor control strategy will 

involve monitoring for these parameters. 

Today’s rule requires all PWSs using 

UV for disinfection compliance to treat 


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at least 95 percent of the water 

distributed to the public each month 

with UV reactors operating within 

validated conditions for the required UV 

dose. EPA views this 95 percent limit as 

a feasible minimum level of 

performance for PWSs to achieve, while 

ensuring the desired level of health 

protection is provided. For purposes of 

design and operation, PWSs should 

strive to deliver the required UV dose at 

all times during treatment. 

EPA developed these requirements 

and the associated UV Disinfection 

Guidance Manual solely for public 

water systems using UV light to meet 

drinking water disinfection standards 

established under SDWA. EPA has not 

addressed and did not consider the 

extension of these requirements and 

guidance to other applications, 

including point of entry or point of use 

devices for residential water treatment 

that are not operated by public water 

systems to meet SDWA disinfection 

standards. 

c. Summary of Major Comments 

Public comment on the August 11, 

2003 LT2ESWTR proposal supported 

the inclusion of UV light in the 

microbial toolbox for Cryptosporidium 

inactivation. EPA received significant 

comment on the UV dose tables, the use 

of adenovirus as the basis for virus UV 

dose requirements, UV compliance 

standards for filtered systems, and 

safety factors associated with draft 

guidance. These comments and EPA’s 

responses are summarized as follows. 

Commenters generally supported the 

proposed UV dose values for 

Cryptosporidium and Giardia lamblia 

inactivation and recommended that EPA 

incorporate these values into the final 

rule. Several commenters requested that 

EPA provide values for 3.5-, 4.0- or 

higher log inactivation of 

Cryptosporidium and Giardia lamblia 

because available dose-response data 

include this range. Due to factors like 

tailing and censoring in the underlying 

dose-response data, some commenters 

stated that the proposed UV dose values 

are conservative and advised EPA to 

consider this conservatism when 

recommending additional safety factors 

in guidance. 

In response, EPA has extended the UV 

dose table in today’s rule to cover 3.5- 

and 4.0-log Cryptosporidium and 

Giardia lamblia inactivation. None of 

EPA’s regulations require inactivation of 

Cryptosporidium or Giardia lamblia 

above these levels, so EPA has not 

established UV dose requirements for 

inactivation above 4-log. EPA believes 

that the statistical analysis used to 

determine the required UV doses 

appropriately accounts for variability, 

tailing, and censoring in the underlying 

dose-response data. However, the 

required UV dose values do not account 

for bias and uncertainty associated with 

UV reactor validation and monitoring, 

which are addressed in guidance. 

Several commenters were concerned 

with the use of adenovirus to set UV 

dose requirements for virus inactivation 

because the resulting dose values are 

several times higher than typical UV 

doses for drinking water disinfection. 

These high dose values impact the 

feasibility of PWSs using UV to fully 

meet virus treatment requirements, 

which will hinder the use of UV to 

reduce DBPs and for point-of-entry 

treatment. Commenters requested that 

EPA consider waterborne viruses that 

are more UV-sensitive, such as rotavirus 

or hepatitus, when setting UV dose 

requirements. Commenters noted that 

adenovirus commonly causes infections 

of the lung or eye, which are not 

transmitted through water consumption, 

and that no drinking water outbreaks 

associated with adenovirus have been 

reported in the United States. 

EPA recognizes that the UV doses for 

virus inactivation in today’s rule are 

relatively high and that this will limit 

the degree to which PWSs can use UV 

for virus treatment. Based on occurrence 

and health effects, however, EPA 

continues to believe that UV dose 

requirements should be protective for 

adenovirus. The existing requirement 

for 4-log virus treatment, as established 

under the SWTR, applies to all 

waterborne viruses of public health 

concern in PWSs. Adenovirus is 

consistently found in water subject to 

fecal contamination and can be 

transmitted through consumption of or 

exposure to contaminated water. It is a 

common cause of diarrheal illness, 

particularly in children, and fecal 

shedding is prevalent in asymptomatic 

adults. While illness from adenovirus is 

typically self-limiting, severe health 

effects, including death, can occur. 

Consequently, EPA regards adenovirus 

as a potential health concern in PWSs 

and has established UV dose 

requirements to address it. 

Many commenters recommended that 

EPA establish a compliance standard for 

the operation of UV reactors within 

validated conditions by filtered PWSs, 

similar to the 95 percent standard 

proposed for unfiltered PWSs. 

Commenters were concerned that 

without a clear compliance standard in 

the rule, filtered PWSs would be held to 

inconsistent and unclear standards, 

which would impede the design and 

implementation of UV systems. Some 

commenters recommended that filtered 

PWSs by held to the same 95 percent 

standard as unfiltered PWSs, while 

others recommended a lower 90 percent 

standard on the basis that filtered PWSs 

have more barriers of protection. 

EPA agrees that establishing a clear 

compliance standard for the use of UV 

to meet inactivation requirements is 

appropriate. For filtered PWSs using UV 

to meet microbial treatment 

requirements, today’s final rule requires 

at least 95 percent of the water 

distributed to consumers to be treated 

by UV reactors operating within 

validated conditions. This is the same 

standard that applies to unfiltered 

PWSs. EPA believes that a 95th 

percentile standard is feasible for all 

PWSs and represents the minimum 

level of performance that should be 

achieved. During routine operation, 

PWSs should endeavor to maintain UV 

reactors within validated conditions for 

the required UV dose at all times. 

E. Disinfection Benchmarking for 

Giardia lamblia and Viruses 

1. Today’s Rule 

The purpose of disinfection 

benchmarking under today’s rule is to 

ensure that PWSs maintain protection 

against microbial pathogens as they 

implement the Stage 2 DBPR and 

LT2ESWTR. If a PWS proposes to make 

a significant change in disinfection 

practice, the PWS must perform the 

following: 

• Develop a disinfection profile for 

Giardia lamblia and viruses. A 

disinfection profile consists of 

documenting Giardia lamblia and virus 

log inactivation levels at least weekly 

over a period of at least one year. PWSs 

that operate for less than one year must 

profile only during the period of 

operation. The calculated log 

inactivation levels must include the 

entire treatment plant and must be 

based on operational and water quality 

data, such as disinfectant residual 

concentration(s), contact time(s), 

temperature(s), and, where necessary, 

pH. PWSs may create profiles by 

conducting new weekly (or more 

frequent) monitoring and/or by using 

previously collected data. A PWS that 

created a Giardia lamblia disinfection 

profile under the IESWTR or 

LT1ESWTR may use the operational 

data collected for the Giardia lamblia 

profile to create a virus disinfection 

profile. 

• Calculate a disinfection benchmark, 

using the following procedure: (1) 

Determine the calendar month with the 

lowest log inactivation; (2) The lowest 

month becomes the critical period for 

that year; (3) If acceptable data from 


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multiple years are available, the average 

of critical periods for each year becomes 

the benchmark; (4) If only one year of 

data is available, the critical period for 

that year is the benchmark. 

• Notify the State before 

implementing the significant change in 

disinfection practice. The notification to 

the State must include a description of 

the proposed change, the disinfection 

profiles and inactivation benchmarks for 

Giardia lamblia and viruses, and an 

analysis of how the proposed change 

will affect the current inactivation 

benchmarks. 

For the purpose of these 

requirements, significant changes in 

disinfection practice are defined as (1) 

moving the point of disinfection (this is 

not intended to include routine seasonal 

changes already approved by the State), 

(2) changing the type of disinfectant, (3) 

changing the disinfection process, or (4) 

making other modifications designated 

as significant by the State. The 

Disinfection Profiling and 

Benchmarking Guidance Manual 

provides information to PWSs and 

States on the development of 

disinfection profiles, identification and 

evaluation of significant changes in 

disinfection practices, and 

considerations for setting an alternative 

benchmark (USEPA 1999d). 

2. Background and Analysis 

A goal in the development of rules to 

control microbial pathogens and 

disinfection byproducts (DBPs) is the 

balancing risks between these two 

classes of contaminants. EPA 

established disinfection profiling and 

benchmarking under the IESWTR and 

LT1ESWTR, based on a 

recommendation by the Stage 1 M–DBP 

Advisory Committee, to ensure that 

PWSs maintained adequate protection 

against pathogens as they reduced risk 

from DBPs. EPA is extending profiling 

and benchmarking requirements to the 

LT2ESWTR for the same objective. 

Some PWSs will make significant 

changes in their current disinfection 

practice to meet TTHM and HAA5 

requirements under the Stage 2 DBPR 

and to provide additional treatment for 

Cryptosporidium under the LT2ESWTR. 

To ensure that these PWSs maintain 

disinfection that is effective against a 

broad spectrum of microbial pathogens, 

EPA believes that PWSs and States 

should evaluate the effects of significant 

changes in disinfection practice on 

current microbial treatment levels. 

Disinfection profiling and 

benchmarking serves as a tool for 

making such evaluations. 

The August 11, 2003 LT2ESWTR 

proposal included disinfection profiling 

and benchmarking requirements. Under 

the proposal, profiling for Giardia 

lamblia and viruses was required if a 

PWS was required to monitor for 

Cryptosporidium or, in the case of small 

PWSs, exceeded 80 percent of the 

TTHM or HAA5 MCL based on a 

locational running annual average. 

Under this approach, most large PWSs 

and a significant fraction of small PWSs 

were required to develop profiles. The 

proposal also included a schedule for 

disinfection profile development. Those 

PWSs that developed profiles were then 

required to calculate a disinfection 

benchmark and notify the State if they 

proposed to make a significant change 

in disinfection practice. 

In today’s final rule, EPA has 

significantly modified the applicability 

requirements for disinfection profiling. 

PWSs are only required to develop a 

disinfection profile if they propose to 

make a significant change in 

disinfection practice after completing 

the first round of source water 

monitoring. EPA has made this change 

from the proposal because under the 

LT2ESWTR and Stage 2 DBPR, most 

PWSs will not be required to make 

significant changes to their disinfection 

practice. Consequently, most PWSs will 

not need a disinfection profile. EPA 

believes that disinfection profiling 

requirements should be targeted to those 

PWSs that will make significant 

disinfection changes. 

EPA has also eliminated the 

scheduling requirements for 

development of the disinfection profile 

in order to provide more flexibility to 

PWSs and States. Today’s rule only 

requires that PWSs notify States prior to 

making a significant change in their 

disinfection practice and that this 

notification include the disinfection 

profiles and benchmarks, along with an 

analysis of how the proposed change 

will affect the current benchmarks. EPA 

believes that PWSs should collect the 

operational data needed to develop 

disinfection profiles, such as 

disinfectant residual, water temperature, 

and flow rate, as part of routine practice. 

PWSs that do not have current 

disinfection profiles should record this 

operational information at least weekly 

for one year so that they can use it to 

develop disinfection profiles if required. 

Today’s rule retains the proposed 

requirement that when disinfection 

profiling is required, PWSs must 

develop profiles for both Giardia 

lamblia and viruses. EPA believes that 

profiling for both target pathogens is 

appropriate because the types of 

treatment changes that PWSs will make 

to comply with the Stage 2 DBPR or 

LT2ESWTR could lead to a significant 

change in the inactivation level for one 

pathogen but not the other. For 

example, a PWS that switches from 

chlorine to UV light to meet Giardia 

lamblia inactivation requirements is 

likely to maintain a high level of 

treatment for this pathogen. The level of 

treatment for viruses, however, may be 

significantly reduced. In general, viruses 

are much more sensitive to chlorine 

than Giardia but are more resistant to 

UV. The situation for a PWS switching 

to microfiltration is similar. The same 

operational data are used to develop 

disinfection profiles for both Giardia 

lamblia and viruses. 

As was the case with the IESWTR and 

LT1ESWTR, the disinfection benchmark 

under today’s rule is not intended to 

function as a regulatory standard. 

Rather, the objective of these provisions 

is to facilitate interactions between the 

States and PWSs to assess the impact on 

microbial risk of proposed changes to 

disinfection practice. Final decisions 

regarding levels of disinfection for 

Giardia lamblia and viruses beyond the 

minimum required by regulation will 

continue to be left to the States and 

PWSs. To ensure that the level of 

treatment for both protozoan and viral 

pathogens is appropriate, States and 

PWSs should consider site-specific 

factors such as source water 

contamination levels and the reliability 

of treatment processes. 

3. Summary of Major Comments 

EPA received significant public 

comment on disinfection profiling and 

benchmarking requirements in the 

August 11, 2003 proposal. A few 

commenters supported the proposed 

requirements but most raised concerns 

with the burden and usefulness of 

disinfection profiling and requested 

greater flexibility. These comments and 

EPA’s responses are summarized as 

follows. 

Commenters stated that disinfection 

profiling diverts PWS and State 

resources from other public health 

protection activities and presents an 

incomplete picture of the information 

that should be considered when 

evaluating disinfection changes. 

Further, some States can only require 

the level of treatment specified in 

regulations (e.g., the SWTR, IESWTR, 

LT1ESWTR) and cannot use a 

disinfection benchmark to enforce a 

higher treatment standard. Some 

commenters also disagreed with 

requiring a disinfection profile for 

viruses, since current disinfection 

practices targeting Giardia lamblia 

typically achieve much greater virus 

inactivation than required. 


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To address these concerns, 

commenters requested that profiling 

only be required for PWSs prior to 

switching disinfectants or that States be 

allowed to grant waivers from 

disinfection profiling requirements. 

Commenters also recommended that 

States be given flexibility to determine 

the appropriate time for PWSs to 

develop disinfection profiles, if 

necessary. In regard to virus profiling, 

some commenters suggested that it only 

be required for PWSs that have not 

developed profiles for Giardia lamblia 

or that are switching disinfectants to 

UV. 

In response, EPA has modified the 

proposed requirements for disinfection 

profiling and benchmarking from the 

proposal to significantly reduce the 

burden on PWSs and States. In today’s 

final rule, profiling is only required for 

PWSs that propose to make a significant 

change in disinfection practice. EPA 

projects that most PWSs will not be 

required to make treatment changes to 

comply with the LT2ESWTR and Stage 

2 DBPR and, as a result, will not be 

required to develop disinfection 

profiles. Further, today’s rule gives 

PWSs and States flexibility to determine 

the timing for developing disinfection 

profiles and only requires that the 

profiles and benchmarks be included in 

a notification to the State before a PWS 

implements a significant change in 

disinfection practice. For PWSs that 

have not developed disinfection 

profiles, EPA recommends recording the 

necessary operational data at least 

weekly over one year so that a profile 

can be prepared if needed. 

For PWSs that propose to make a 

significant change in disinfection 

practice, today’s rule maintains the 

proposed requirement for a disinfection 

profile for viruses. EPA recognizes that 

current disinfection practices with 

chlorine typically achieve far more virus 

inactivation than required. However, the 

types of treatment changes that PWSs 

will make to comply with the Stage 2 

DBPR or LT2ESWTR, such as 

implementing UV or microfiltration, are 

likely to maintain high levels of 

treatment for Giardia lamblia but may 

result in a significant decrease in 

treatment for viruses. Consequently, 

EPA believes that States and PWSs 

should consider whether such a 

decrease in virus treatment will occur 

when evaluating proposed treatment 

changes. 

Moreover, developing a virus 

disinfection profile does not require the 

collection of operational data beyond 

that necessary to develop a Giardia 

lamblia disinfection profile. Therefore, 

today’s rule allows PWSs to use 

previously developed Giardia lamblia 

disinfection profiles and allows the 

operational data that underlie the 

Giardia lamblia profile to be used for a 

virus disinfection profile. 

F. Requirements for Systems With 

Uncovered Finished Water Storage 

Facilities 

1. Today’s Rule 

Today’s rule requires PWSs that store 

treated water in an open reservoir (i.e., 

use uncovered finished water storage 

facilities) to do either of the following: 

• Cover the finished water storage 

facility; or 

• Treat the discharge of the 

uncovered finished water storage 

facility that is distributed to consumers 

to achieve inactivation and/or removal 

of 4-log virus, 3-log Giardia lamblia, and 

2-log Cryptosporidium. 

PWSs must notify the State if they use 

uncovered finished water storage 

facilities no later than April 1, 2008. 

PWSs must either meet the 

requirements of today’s rule for covering 

or treating each facility or be in 

compliance with a State-approved 

schedule for meeting these requirements 

no later than April 1, 2009. 

Today’s rule revises the definition of 

an uncovered finished water storage 

facility as follows: uncovered finished 

water storage facility is a tank, reservoir, 

or other facility used to store water that 

will undergo no further treatment to 

reduce microbial pathogens except 

residual disinfection and is directly 

open to the atmosphere. 

2. Background and Analysis 

The requirements in today’s rule for 

PWSs that use uncovered finished water 

storage facilities (open reservoirs) are 

based on an assessment of the types and 

sources of contaminants in open 

reservoirs, the efficacy and feasibility of 

regulatory approaches to reduce risks 

from this contamination, and comments 

on the August 11, 2003 proposal. The 

following discussion summarizes this 

assessment. 

a. Types and sources of contaminants 

in open reservoirs. The storage of treated 

drinking water in open reservoirs can 

lead to significant water quality 

degradation and health risks to 

consumers (USEPA 1999e). Examples of 

such water quality degradation include 

increases in algal cells, coliform 

bacteria, heterotrophic plate count 

bacteria, turbidity, particulates, DBPs, 

metals, taste and odor, insect larvae, 

Giardia, Cryptosporidium, and nitrate 

(USEPA 1999e). Contamination of open 

reservoirs occurs through surface water 

runoff, bird and animal wastes, human 

activity, algal growth, insects and fish, 

and airborne deposition. Additional 

information on these sources of 

contamination follows. 

If a reservoir receives surface water 

runoff, the SWTR requires that it be 

treated as raw water storage, rather than 

a finished water reservoir (40 CFR 

141.70(a)). Nevertheless, many 

uncovered finished water reservoirs 

have been found to be affected by 

surface water runoff, which may include 

agricultural fertilizers, pesticides, 

microbial pathogens, automotive fluids 

and residues, sediment, nutrients, 

natural organic matter, and metals 

(USEPA 1999e, LeChevallier et al. 

1997). 

Birds are a significant cause of 

contamination in open reservoirs, and 

bird feces may contain coliform 

bacteria, viruses, and other human 

pathogens, including vibrio cholera, 

Salmonella, Mycobacteria, Typhoid, 

Giardia, and Cryptosporidium 

(Geldreich and Shaw 1993). Birds can 

ingest pathogens at landfills or 

wastewater treatment plants prior to 

visiting a reservoir and have been 

shown to carry and pass infectious 

Cryptosporidium parvum (Graczyk et al. 

1996). Five to twenty percent of birds 

are estimated to be periodically infected 

with human pathogens like Salmonella 

(USEPA 1999e). A 1993 Salmonella 

outbreak in Gideon, MO that resulted in 

seven deaths was traced to pigeons 

roosting in a finished water storage tank. 

Animals that are either known or 

suspected to contaminate open 

reservoirs include dogs, cats, deer, rats, 

mice, opossums, squirrels, muskrats, 

raccoons, beavers, rabbits, and frogs. 

Some animals are infected with human 

pathogens like Cryptosporidium, which 

can be discharged to the reservoirs in 

feces or transmitted by direct contact 

between animals and the water (Fayer 

and Unger 1986, Current 1986, USEPA 

1999e). 

Open reservoirs are exposed to 

contamination through human 

activities. Pesticides and fertilizers can 

enter open reservoirs through runoff and 

airborne drifts from spray applications. 

Swimming in reservoirs can result in 

pathogens being passed from the feces, 

shedded skin, and mucus membranes of 

infected persons. PWSs routinely find a 

great variety of items that have been 

thrown into open reservoirs, despite the 

use of high fences and set-back 

distances. Such items include baby 

carriages, beer bottles, bicycles, bullets, 

dead animals, dog waste bags, fireworks, 

garbage cans, a pay phone, shoes, and 

shovels (USEPA 1999e). These items are 

a potential source of pathogens and 

toxic substances and clearly indicate the 


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susceptibility of open reservoirs to 

intentional contamination. 

Algal growth is common in open 

reservoirs and can lead to aesthetic 

problems like color, taste, and odor, and 

may generate cyanobacterial toxins, 

which cause headaches, fever, diarrhea, 

abdominal pain, nausea, and vomiting. 

In addition, algae can increase other 

contaminants like DBPs by increasing 

biomass within reservoirs, and 

corrosion products like lead, through 

causing significant pH fluctuations. 

Algae have been shown to shield 

bacteria from the effects of disinfection 

(Geldreich and Shaw 1993). 

Open reservoirs may be infested with 

the larvae of insects such as midge flies, 

water fleas, and gnats, which can be 

carried through the distribution system 

from the reservoir (USEPA 1999e). 

Chlorination is ineffective against midge 

fly larvae. Fly outbreaks may increase 

the presence of insect-eating birds, 

which present another source of 

contamination as described earlier. 

Some open finished water reservoirs 

have been found to support fish 

populations. 

Open reservoirs also are subject to 

airborne deposition of contaminants, 

such as industrial pollutants, 

automobile emissions, pollen, dust, 

particulate matter, and bacteria. 

Deposition occurs during all types of 

weather conditions, but is likely to be 

accelerated during precipitation events 

as air pollutants are transported from 

the air column above the reservoir by 

rain or snow. 

b. Regulatory approaches to reduce 

risk from contamination in open 

reservoirs. For many decades, public 

health agencies and professional 

associations like the American Public 

Health Association, the U.S. Public 

Health Service, and the American Water 

Works Association have recommended 

that all finished water reservoirs be 

covered (USEPA 1999e). In the IESWTR 

and LT1ESWTR, EPA prohibited the 

construction of new uncovered finished 

water reservoirs (40 CFR 141.170(c) and 

141.511). These regulations did not 

address existing uncovered finished 

water reservoirs, however. In the 

preamble to the IESWTR, EPA stated 

that a requirement to cover existing 

reservoirs would be considered when 

data to develop national cost estimates 

were available. 

EPA has now collected the necessary 

data to estimate costs associated with 

regulatory control strategies for 

uncovered finished water reservoirs. 

The August 11, 2003 LT2ESWTR 

proposal included three options for 

PWSs with uncovered finished water 

reservoirs to reduce risk: (1) cover the 

reservoir, (2) treat the discharge to 

achieve 4-log virus inactivation, or (3) 

implement a State-approved risk 

mitigation plan (USEPA 2003a). These 

options reflected recommendations from 

the Stage 2 M–DBP Advisory Committee 

(USEPA 2000a). Today’s final rule 

includes the first option to cover, 

modifies the second option to also 

require 3-log Giardia and 2-log 

Cryptosporidium treatment, and does 

not establish an option for a risk 

mitigation plan. The following 

discussion describes the basis for these 

changes. 

As described earlier, studies have 

shown that small mammals and birds 

that live near water may be infected 

with Cryptosporidium and Giardia and 

may shed infectious oocysts and cysts 

into the water (Graczyk et al. 1996, 

Fayer and Unger 1986, Current 1986). 

LeChevallier et al. (1997) evaluated 

Cryptosporidium and Giardia levels in 

six uncovered finished water reservoirs. 

The geometric mean concentration of 

Cryptosporidium was 1.2 oocysts/100 L 

in the inlet samples and 8.1 oocysts/100 

L in the effluent samples (i.e., 600 

percent increase in the reservoir). For 

Giardia, the geometric mean 

concentrations in the inlet and effluent 

samples were 1.9 and 6.1 cysts/100 L, 

respectively (i.e., 200 percent increase 

in reservoir). 

Most, if not all, PWSs would treat to 

achieve 4-log virus inactivation with 

chlorine. Based on EPA guidance, the 

dose of chlorine necessary for 4-log 

virus inactivation would not achieve 

even 0.5-log Giardia inactivation and 

would produce no inactivation of 

Cryptosporidium (USEPA 1991b). 

Consequently, PWSs treating for viruses 

in open reservoirs, as proposed, would 

provide very little protection against 

contamination by Giardia and 

Cryptosporidium. 

Due to the demonstrated potential for 

contamination by Giardia and 

Cryptosporidium in open reservoirs and 

the ineffectiveness of virus treatment 

against these pathogens, today’s rule 

requires PWSs to treat for Giardia and 

Cryptosporidium in addition to viruses 

if they do not cover their finished water 

reservoirs. Specifically, today’s rule 

specifies the same baseline treatment as 

required for a raw unfiltered source, 

which is 4-log virus, 3-log Giardia, and 

2-log Cryptosporidium reduction. 

EPA believes that requiring treatment 

for viruses, Giardia, and 

Cryptosporidium in uncovered finished 

water reservoirs is consistent with 

SDWA section 1412(b)(7)(A), which 

authorizes the use of a treatment 

technique to prevent adverse health 

effects to the extent feasible if 

measuring the contaminant is not 

feasible. Monitoring for these pathogens 

at the very low levels that would cause 

public health concern and at the 

frequency necessary to detect 

contamination events is not feasible 

with available analytical methods. EPA 

has determined that with the 

availability of technologies like UV, 

treating for Giardia, Cryptosporidium, 

and viruses is feasible for all PWS sizes. 

Today’s rule does not allow PWSs to 

implement a risk mitigation plan as an 

alternative to covering a reservoir or 

treating the discharge because EPA does 

not believe that a risk mitigation plan 

would provide equivalent public health 

protection. Consequently, a risk 

mitigation plan would not meet the 

statutory provision for a treatment 

technique to prevent adverse health 

effects from pathogens like Giardia and 

Cryptosporidium to the extent feasible 

(SDWA section 1412(b)(7)(A)). 

As discussed earlier, open reservoirs 

are subject to contamination from many 

sources, including runoff, birds, 

animals, humans, algae, insects, and 

airborne deposition. Control measures 

can provide a degree of protection 

against some of these sources (e.g., bird 

deterrent wires, security fences with 

setback distances). All PWSs are 

significantly constrained, however, in 

the degree to which they can implement 

such measures with existing open 

reservoirs due to factors like the size of 

the reservoir, the location of the 

reservoir (e.g., within residential 

communities or parks), and the existing 

infrastructure. For example, many open 

finished water reservoirs are impacted 

by runoff, despite the fact that this has 

been prohibited for many years under 

existing regulations (USEPA 1999e). 

EPA has concluded that implementing 

control measures that would be highly 

effective against all sources of 

contamination of open reservoirs would 

not be feasible for PWSs. Accordingly, 

today’s rule does not allow this option. 

c. Definition of uncovered finished 

water storage facility. The IESWTR 

established the following definition for 

an uncovered finished water storage 

facility: uncovered finished water 

storage facility is a tank, reservoir, or 

other facility used to store water that 

will undergo no further treatment 

except residual disinfection and is open 

to the atmosphere. 

In the August 11, 2003, proposed 

LT2ESWTR, EPA requested comment on 

whether this definition should be 

revised. EPA was concerned that it 

would not include certain cases in 

which water is stored in an open 

reservoir after a PWS completes 

treatment to reduce microbial 


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pathogens. Such a case would be a PWS 

that applies a corrosion inhibitor to the 

effluent of an open reservoir where 

water is stored after filtration and 

primary disinfection. In this case, the 

PWS could claim that the corrosion 

inhibitor constitutes additional 

treatment and, consequently, the open 

reservoir does not meet EPA’s definition 

of an uncovered finished water storage 

facility. However, the water stored in 

the open reservoir would be subject to 

microbial contamination from the 

sources described in this section and 

would undergo no further treatment for 

this contamination. 

Today’s rule revises the definition of 

an uncovered finished water storage 

facility in two ways: (1) The phrase ‘‘to 

reduce microbial pathogens’’ is inserted 

following the word ‘‘treatment;’’ and (2) 

the word ‘‘directly’’ is inserted prior to 

‘‘open to the atmosphere.’’ The first 

change ensures that an open reservoir 

where water is stored after a PWS has 

completed filtration (where required) 

and primary disinfection will be 

appropriately classified as an uncovered 

finished water storage facility. Whether 

a PWS applies corrosion control or other 

treatment to maintain water quality in 

the distribution system will not affect 

this determination. 

The second change clarifies that 

covered reservoirs with air vents or 

overflow lines are not uncovered 

finished water storage facilities. Such 

air vents and overflow lines are open to 

the atmosphere but are usually hooded 

or screened to prevent contamination of 

the water. Consequently, these 

reservoirs are not directly open to the 

atmosphere and are not subject to the 

requirements of today’s rule for 

uncovered finished water storage 

facilities. 

3. Summary of Major Comments 

EPA received significant public 

comment on requirements for 

uncovered finished water storage 

facilities in the August 11, 2003 

proposal. Major issues raised by 

commenters include whether to require 

all reservoirs to be covered, requiring 

treatment for Giardia and 

Cryptosporidium, support for the 

proposed options, and revising the 

definition of an uncovered finished 

water storage facilities. A summary of 

these comments and EPA’s responses 

follows. 

Several commenters recommended 

that EPA require all finished water 

reservoirs to be covered. These 

commenters stated that making an 

uncovered reservoir equal in quality to 

a covered reservoir is not possible—

open reservoirs will always be 

contaminated by fecal material from 

birds and small mammals, as well as 

increased DBPs due to algae and other 

aquatic organisms, airborne 

contaminants, and sediment stirred up 

by wind. Commenters were also 

concerned that uncovered reservoirs are 

a major vulnerability for PWS security 

(i.e., intentional contamination). Some 

commenters cited the fact that there are 

hundreds of thousands of covered 

finished water reservoirs in comparison 

to approximately 100 uncovered 

finished water reservoirs as evidence 

that the public health risks of open 

reservoirs are widely recognized. 

EPA agrees that storing treated water 

in open reservoirs presents a risk to 

public health. With today’s final rule, 

EPA expects that many PWSs will cover 

or eliminate uncovered finished water 

reservoirs. For reservoirs where 

covering is not feasible, EPA believes 

that treating the water for Giardia, 

Cryptosporidium, and viruses will 

provide protection against the range of 

pathogens likely to contaminate the 

reservoir. 

Many commenters supported 

requiring treatment for Giardia and 

Cryptosporidium for PWSs that treat the 

reservoir discharge. Commenters stated 

that reservoirs should either be covered 

or treated as unfiltered sources 

(meaning 3-log Giardia, 2-log 

Cryptosporidium, and 4-log virus 

treatment). The LeChevallier et al. 

(1997) study was cited as demonstrating 

increases in Giardia and 

Cryptosporidium in uncovered finished 

water reservoirs, and commenters noted 

that treatment for viruses would not be 

effective against these protozoa. EPA 

agrees with these comments and today’s 

rule requires treatment for Giardia and 

Cryptosporidium, as well as viruses, by 

PWSs that do not cover their reservoirs. 

Some commenters expressed support 

for the proposed options, including 

allowing risk mitigation plans as an 

adequate remedy for an uncovered 

reservoir. These commenters 

characterized the proposal as providing 

reasonable alternatives to the substantial 

costs involved in covering reservoirs or 

providing alternative storage. 

Commenters stated that strategies 

included in a risk management plan 

could address the range of 

microorganisms for which treatment is 

necessary, depending on site-specific 

circumstances. 

EPA recognizes that covering or 

finding alternative storage for uncovered 

finished water reservoirs can be costly. 

While EPA believes that covering 

finished water reservoirs is the most 

effective approach to protecting public 

health, today’s rule allows PWSs to 

provide treatment for Giardia, 

Cryptosporidium, and viruses as a 

feasible alternative. As described earlier, 

EPA does not believe that providing 

treatment only for viruses, as proposed, 

would be protective against the range of 

pathogens that contaminate open 

reservoirs. Further, EPA has concluded 

that implementing a risk mitigation plan 

that would provide equivalent 

protection to covering or treating a 

reservoir is not feasible. This is due to 

the many potential sources of 

contamination and the significant 

limitations that all PWSs have in the 

control measures they can implement 

for existing open reservoirs. 

Commenters supported revising the 

definition of uncovered finished water 

storage facilities to include situations 

where PWSs apply a treatment like 

corrosion control to water stored in an 

open reservoir after the water has 

undergone filtration, where required, 

and primary disinfection. In addition, 

commenters recommended that EPA 

clarify that ‘‘open to the atmosphere’’ in 

the definition does not include vents 

and overflow lines in covered 

reservoirs. EPA agrees with these 

comments and today’s rule is consistent 

with them. 

G. Compliance Schedules 

1. Today’s Rule 

This section specifies compliance 

dates for the monitoring and treatment 

technique requirements in today’s rule. 

As described in sections IV.A through 

IV.F of this preamble, today’s rule 

requires PWSs to carry out the following 

activities: 

• Conduct initial source water 

monitoring on a reported schedule. 

PWSs may grandfather previously 

collected monitoring results and may 

elect to provide the maximum 

Cryptosporidium treatment level of 5.5- 

log for filtered PWSs or 3.0-log for 

unfiltered PWSs instead of monitoring. 

• Determine a treatment bin 

classification (or mean Cryptosporidium 

level for unfiltered PWSs) based on 

monitoring results. 

• For filtered PWSs in Bins 2–4 and 

all unfiltered PWSs, provide additional 

treatment for Cryptosporidium by 

selecting technologies from the 

microbial toolbox. 

• Report disinfection profiles and 

benchmarks prior to making a 

significant change in disinfection 

practice. 

• Report the use of uncovered 

finished water storage facilities and 

cover or treat the discharge of such 

reservoirs on a State-approved schedule. 


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• Conduct a second round of source 

water monitoring approximately six 

years after initial bin classification. 

Compliance dates for these activities 

vary by PWS size. Tables IV.G–1 and 

IV.G–2 specify source water monitoring 

and treatment compliance dates for 

large and small PWSs, respectively. 

Table IV.G–3 shows compliance dates 

for PWSs using uncovered finished 

water storage facilities. Wholesale PWSs 

must comply with the requirements of 

today’s rule based on the population of 

the largest PWS in the combined 

distribution system. 

TABLE IV.G–1.—MONITORING AND TREATMENT COMPLIANCE DATES FOR PWSS SERVING AT LEAST 10,000 PEOPLE

Requirement 

Compliance dates by PWS Size 

PWSs serving at least 

100,000 people 

PWSs serving at least 

50,000 but less than 

100,000 people 

PWSs serving at least 

10,000 but less than 

50,000 people 

Report sampling schedule and sampling location description for initial source water monitoring for 

Cryptosporidium (plus E. coli and turbidity at filtered 

PWSs) 1, 2.

No later than July 1, 2006. No later than January 1, 

2007.

No later than January 1, 

2008. 

Report notice of intent to grandfather previously collected Cryptosporidium data, if applicable.

Report intent to provide the maximum Cryptosporidium 

treatment level in lieu of monitoring, if applicable 1.

Begin initial source water monitoring for 

Cryptosporidium (plus E. coli and turbidity at filtered 

PWSs) 1,2.

No later than the month 

beginning October 1, 

2006.

No later than the month 

beginning April 1, 2007.

No later than the month 

beginning April 1, 2008. 

Submit previously collected Cryptosporidium data and 

required documentation for grandfathering, if applicable.

No later than December 1, 

2006.

No later than June 1, 

2007..

No later than June 1, 

2008. 

Report Cryptosporidium treatment bin classification (or 

mean Cryptosporidium concentration for unfiltered 

PWSs) and supporting data for approval.

No later than the month 

beginning April 1, 2009.

No later than the month 

beginning October 1, 

2009.

No later than the month 

beginning October 1, 

2010. 

Report disinfection profiles and benchmarks, if applicable.Prior to making a significant change in disinfection practice. 

Comply with additional Cryptosporidium treatment requirements based on treatment bin classification (or 

mean Cryptosporidium concentration for unfiltered 

PWSs) 3.

No later than April 1, 

2012 3.

No later than October 1, 

2013 3.

No later than October 1, 

2012 3. 

Report sampling schedule and sampling location description for second round of source water monitoring 

for Cryptosporidium (plus E. coli and turbidity at filtered PWSs) 1.

No later than January 1, 

2015.

No later than July 1, 2015. No later than July 1, 2016. 

Report intent to provide maximum Cryptosporidium 

treatment level in lieu of monitoring, if applicable 1.

Begin second round of source water monitoring for 

Cryptosporidium (plus E. coli and turbidity at filtered 

PWSs) 1.

No later than the month 

beginning April 1, 2015.

No later than the month 

beginning October 1, 

2015.

No later than the month 

beginning October 1, 

2016. 

Report Cryptosporidium treatment bin classification (or 

mean Cryptosporidium concentration for unfiltered 

PWSs) and supporting data from second round of 

monitoring for approval.

No later than the month 

beginning October 1, 

2017.

No later than the month 

beginning April 1, 2018.

No later than the month 

beginning April 1, 2019. 

Comply with additional Cryptosporidium treatment requirements if bin classification (or mean 

Cryptosporidium concentration for unfiltered PWSs) 

changes based on second round of monitoring.

On a schedule the State approves. 

1PWS are not required to conduct source water monitoring if they submit a notice of intent to provide the maximum Cryptosporidium treatment 

level: 5.5-log for filtered PWSs or 3.0-log for unfiltered PWSs. 2 Not required if PWS grandfathers at least 2 years of Cryptosporidium data. 

3States may grant up to an additional 2 years for systems making capital improvements. 

TABLE IV.G–2.—MONITORING AND TREATMENT COMPLIANCE DATES FOR PWSS SERVING FEWER THAN 10,000 PEOPLE

Requirement Compliance dates 

Indicator (E. coli) Monitoring Requirements for Filtered PWSs Only 

Report sampling schedule and sampling location description for initial 

source water monitoring for E. coli or alternative State-approved indicator1 2.

No later than July 1, 2008. 

Report notice intent to grandfather previously collected E. coli data, if 

applicable.

Report intent to provide the maximum Cryptosporidium treatment level 

in lieu of monitoring, if applicable 1.

Begin initial source water monitoring for E. coli1 2 ................................... No later than the month beginning October 1, 2008. 

Report E. coli data for grandfathering, if applicable ................................ No later than December 1, 2008. 


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TABLE IV.G–2.—MONITORING AND TREATMENT COMPLIANCE DATES FOR PWSS SERVING FEWER THAN 10,000 

PEOPLE—Continued 

Requirement Compliance dates 

Report sampling schedule and sampling location description for second 

round of source water monitoring for E. coli 1.

No later than July 1, 2017. 

Report intent to provide the maximum Cryptosporidium treatment level 

in lieu of monitoring, if applicable 1.

Begin second round of source water monitoring for E. coli 1. No later than the month beginning October 1, 2017. 

Requirement 

Compliance dates by monitoring option 

PWSs monitoring twice-per-month 

for 1 year 

PWSs monitoring monthly for 2 

years 

Cryptosporidium Monitoring Requirements for Filtered PWSs That Exceed Indicator (E. coli) Trigger Concentration 3 and All Unfiltered 

PWSs 

Report sampling schedule and sampling location description (if not reported previously) for initial source water monitoring for 

Cryptosporidium 1 4.

No later than January 1, 2010. 

Report notice of intent to grandfather previously collected 

Cryptosporidium data, if applicable. 

Begin initial source water monitoring for Cryptosporidium 1 4 ................. No later than the month beginning April 1, 2010. 

Submit previously collected Cryptosporidium data and required documentation for grandfathering, if applicable.No later than June 1, 2010.

Report Cryptosporidium treatment bin classification (or mean 

Cryptosporidium concentration for unfiltered PWSs) and supporting 

data for approval.

No later than the month beginning 

October 1, 2011.

No later than the month beginning 

October 1, 2012. 

Report disinfection profiles and benchmarks, if applicable .................... Prior to making a significant change in disinfection practice. 

Comply with additional Cryptosporidium treatment requirements based 

on treatment bin classification (or mean Cryptosporidium concentration for unfiltered PWSs) 5.

No later than October 1, 2014 5.

Report sampling schedule sampling location description (if not reported previously) for second round of source water 

Cryptosporidium monitoring 1.

No later than than January 1, 

2019.

Begin second round of source water monitoring for Cryptosporidium 1. No later than the month beginning 

April 1, 2019.

Report Cryptosporidium treatment bin classification (or mean 

Cryptosporidium concentration for unfiltered PWSs) and supporting 

data from second round of monitoring for approval.

No later than the month beginning 

October 1, 2020.

No later than the month beginning 

October 1, 2021. 

Comply with additional Cryptosporidium treatment requirements if bin 

classification (or mean Cryptosporidium concentration for unfiltered 

PWSs) changes based on second round of monitoring.

On a schedule the State approves. 

1PWS are not required to conduct source water monitoring if they submit a notice of intent to provide the maximum Cryptosporidium treatment 

level: 5.5-log for filtered PWSs or 3.0-log for unfiltered PWSs. 2 Not required if PWS grandfathers at least 1 year of E. coli data. 

3Filtered PWSs must conduct Cryptosporidium monitoring if the E. coli annual mean concentration exceeds 10/100 mL for PWSs using lake or 

reservoir sources or exceeds 50/100 mL for PWSs using flowing stream sources or a trigger value for an alternative State-approved indicator is 

exceeded. 4 Not required if PWS grandfathers at least 1 year of twice-per-month or 2 years of monthly Cryptosporidium data. 

5States may grant up to an additional 2 years for PWSs making capital improvements. 

TABLE IV.G–3.—COMPLIANCE DATES FOR PWSS USING UNCOVERED FINISHED WATER STORAGE FACILITIES

Report the use of uncovered finished water storage facilities, if applicable.No later than April 1, 2008. 

Either comply with requirement to cover or treat uncovered finished 

water storage facilities or comply with State-approved schedule to 

meet this requirement.

No later than April 1, 2009. 

2. Background and Analysis 

The compliance schedule in today’s 

final rule stems from its risk-targeted 

approach, wherein PWSs initially 

conduct monitoring to determine 

additional treatment requirements. A 

primary objective of this schedule is to 

ensure that PWSs provide additional 

treatment without delay for higher risk 

sources. This is especially important 

with a risk-targeted rule, given the 

significant time required for initial 

monitoring. However, the compliance 

schedule balances this objective with 

the need to provide PWSs and States 

with time to prepare for implementation 

activities. 

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. 


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In general, PWSs serving at least 

10,000 people conduct two years of 

source water monitoring for 

Cryptosporidium (as well as E. coli and 

turbidity in filtered PWSs). At the 

conclusion of this monitoring, these 

PWSs have six months to analyze 

monitoring results and report their 

treatment bin classification to the State 

for approval. Where required, PWSs 

must provide the necessary level of 

additional Cryptosporidium treatment 

within three years of bin classification, 

though States may allow an additional 

two years for PWSs making capital 

improvements. A second round of 

source water monitoring must be 

initiated six years after initial bin 

classification. 

For PWSs serving at least 10,000 

people, the timing of monitoring and 

treatment activities in today’s rule 

partially reflects recommendations by 

the Stage 2 M–DBP Advisory Committee 

and the schedule in the August 11, 2003 

proposed LT2ESWTR. EPA has 

modified the proposed compliance 

schedule to stagger monitoring start 

dates for PWSs serving 10,000 to 99,999 

people. The following discussion 

addresses these changes from the 

proposal. 

The proposed rule required all PWSs 

serving at least 10,000 people to begin 

source water monitoring six months 

after the rule was established, as 

recommended by the Advisory 

Committee. Under today’s final rule, 

PWSs serving at least 100,000 people 

maintain this schedule. The monitoring 

start date for PWSs serving 50,000 to 

99,999 people is staggered by six 

months and begins 12 months after the 

rule is effective. For PWSs serving 

10,000 to 49,999, the monitoring start 

date is staggered by 18 months and 

begins 24 months after the rule is 

effective. Dates to comply with 

additional treatment requirements are 

staggered accordingly. 

This staggering of monitoring start 

dates for PWSs serving 10,000 to 99,999 

people is advantageous in several 

respects: 

• Provides more time for PWSs that 

have not monitored for 

Cryptosporidium previously to prepare 

for monitoring (PWSs serving at least 

100,000 people monitored for 

Cryptosporidium under the ICR). PWSs 

can use this time to develop budgets, 

establish contracts with 

Cryptosporidium laboratories, identify 

appropriate sampling locations, and 

learn sampling procedures. 

• Provides more time for 

Cryptosporidium analytical laboratories 

to build capacity as needed to 

accommodate the sample analysis needs 

of PWSs. 

• Spreads out the transactional 

demand for regulatory oversight. EPA 

anticipates that the period of greatest 

transactional demand for States and 

EPA that oversee monitoring will be 

when PWSs begin monitoring. The 

staggered schedule will allow States and 

EPA to provide more assistance to 

individual PWSs. 

• Eliminates the gap between the end 

of large PWS monitoring and the start of 

small PWS monitoring (under the 

proposed rule schedule, a gap of 18 

months existed between the time that 

large PWSs completed and small PWSs 

started Cryptosporidium monitoring). 

Such a gap could create difficulties with 

maintaining Cryptosporidium sampling 

and laboratory analysis expertise to 

support monitoring by small PWSs. 

The timing of monitoring and 

treatment activities in today’s rule for 

PWSs serving fewer than 10,000 people 

is nearly identical to the schedule in the 

August 11, 2003 proposed LT2ESWTR 

and reflects recommendations by the 

Advisory Committee. The only change 

is allowing these PWSs the option to 

spread their Cryptosporidium 

monitoring over two years in order to 

facilitate budgeting for this monitoring. 

However, this change does not affect the 

treatment compliance dates for these 

PWSs. 

Specifically, filtered PWSs serving 

fewer than 10,000 people initially 

conduct one year of source water 

monitoring for E. coli or an alternative 

indicator if approved by the State, 

beginning 30 months after the rule is 

effective. At the conclusion of this 

monitoring, these PWSs have six 

months to prepare for Cryptosporidium 

monitoring, if required based on their 

indicator monitoring results. Filtered 

PWSs that exceed the indicator trigger 

value and all unfiltered PWSs serving 

fewer than 10,000 people must begin 

Cryptosporidium monitoring 48 months 

after the rule is effective. This 

Cryptosporidium monitoring may 

consist of sampling twice-per-month for 

one year or once-per-month for two 

years. PWSs must report their bin 

classification to the State for approval 

within six months of the scheduled 

completion of Cryptosporidium 

monitoring. 

Regardless of the Cryptosporidium 

sampling frequency, PWSs serving 

fewer than 10,000 people must comply 

with any additional Cryptosporidium 

treatment requirements within 102 

months (8.5 years) after the rule is 

effective. States may allow an additional 

two years for PWSs making capital 

improvements. PWSs must begin a 

second round of source water 

monitoring for E. coli or an alternative 

State-approved indicator within 11.5 

years (138 months) after the rule is 

effective (six years after the bin 

classification date for PWSs that 

sampled for Cryptosporidium twice-permonth during initial source water 

monitoring). 

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. These PWSs 

serve the majority of people that 

consume water from surface sources. 

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. 

3. Summary of Major Comments 

EPA received significant public 

comment on the compliance schedule in 

the August 11, 2003 proposal. Major 

issues raised by commenters include 

providing more time for PWSs to 

prepare for monitoring, giving States 

more time to oversee monitoring, 

ensuring that laboratory capacity can 

accommodate the compliance schedule, 

and establishing consistent schedules 

for consecutive PWSs. A summary of 

these comments and EPA’s responses 

follows. 

Commenters were concerned that 

some PWSs, in particular PWSs serving 

10,000 to 50,000 people, would need 

more than the three months allowed 

under the proposed rule to report 

sampling schedules for monitoring. In 

order to develop sampling schedules, 

PWSs must establish contracts with 

laboratories, which may involve using 

municipal procurement procedures. For 

smaller PWSs, budgeting for this 

expense may require substantial time 

and planning. 

EPA recognizes this concern and 

today’s final rule provides significantly 

more time for many PWSs to submit 

sampling schedules. Specifically, PWSs 

serving 50,000 to 99,999 people and 

those serving 10,000 to 49,999 people 

must submit sampling schedules 9 and 

21 months after the rule is effective, 

respectively. EPA believes that these 

PWSs will have sufficient time to 

develop sampling schedules with these 

compliance dates. Today’s rule still 

requires PWSs serving at least 100,000 

people to submit sampling schedules 3 

months after the rule is effective. 

Because these PWSs have monitored for 

Cryptosporidium previously, however, 


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EPA believes that this compliance date 

is feasible for these PWSs. 

Several commenters recommended 

that States, rather than EPA, oversee 

monitoring due to States’ existing 

relationships with and knowledge of 

their PWSs. 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. States 

need sufficient time to become familiar 

with the rule, train their staff, prepare 

primacy packages, and train PWSs. 

In general, EPA would prefer that 

States oversee monitoring by their PWSs 

and will work with States to facilitate 

their involvement with rule 

implementation. Where States are 

unable to implement today’s rule, 

however, EPA is prepared to oversee 

implementation. Moreover, EPA 

believes that the staggered compliance 

schedule in today’s final rule will 

enhance States’ ability to implement the 

rule. 

While EPA does not consider waiting 

until 24 months after rule promulgation 

to start monitoring for all PWSs to be 

appropriate, most PWSs will not begin 

monitoring until this time or later under 

today’s rule. Among large PWSs (i.e., 

those serving at least 10,000 people), the 

majority are in the 10,000 to 49,999 

person size category and these PWSs do 

not begin monitoring until 24 months 

after rule promulgation. Further, all 

PWSs serving fewer than 10,000 people 

do not begin monitoring until 30 

months after rule promulgation. These 

smaller PWSs are likely to need the 

most assistance from States. By 

staggering monitoring start dates, 

today’s rule also reduces the number of 

PWSs that will begin monitoring at any 

one time, when the most assistance from 

regulatory agencies will be required. 

Many commenters were concerned 

that the capacity at Cryptosporidium 

analytical laboratories would not be 

sufficient for the proposed 

implementation schedule. Commenters 

noted that the proposed rule schedule 

had a break of 18 months between the 

end of large PWS Cryptosporidium 

monitoring and the start of small PWS 

Cryptosporidium monitoring and 

thought that this break would 

discourage laboratories from making 

investments to improve capacity. Other 

commenters stated that excess 

laboratory capacity exists and that upon 

indication that a final rule is imminent, 

commercial laboratories will hire staff to 

handle the expected number of samples. 

Laboratories will, however, need time to 

train analysts. 

EPA recognizes the concern with 

ensuring that capacity at 

Cryptosporidium laboratories will be 

sufficient. Through EPA’s laboratory 

approval program (described in section 

IV.K), the Agency has evaluated 

capacity at Cryptosporidium 

laboratories. Based on information 

provided by laboratories, EPA believes 

that current capacity at 

Cryptosporidium laboratories will be 

sufficient for the monitoring that PWSs 

serving at least 100,000 people will 

begin six months after the rule is 

effective. EPA expects that commercial 

laboratories will increase capacity as 

needed to serve the demand of smaller 

PWSs that begin monitoring later. 

Approximately six months are required 

to train Cryptosporidium analysts. 

Consequently, the staggered compliance 

schedule should allow time for 

laboratories to hire and train staff as 

necessary. In addition, with the 

compliance schedule in today’s final 

rule, no break exists between the time 

that large PWSs end and small PWSs 

begin Cryptosporidium monitoring. 

Thus, EPA has eliminated this potential 

disincentive to laboratories investing in 

capacity. 

However, EPA will continue to 

monitor laboratory capacity and the 

ability of PWSs to contract with 

laboratories to meet their monitoring 

requirements under the LT2ESWTR. 

The Agency will assist with 

implementation of the rule to help 

maximize the use of available laboratory 

capacity by PWSs. If evidence emerges 

during implementation of the rule that 

PWSs are experiencing problems with 

insufficient laboratory capacity, the 

Agency will undertake appropriate 

action at that time. 

In regard to consecutive PWSs (i.e., 

PWSs that buy and sell treated water), 

commenters recommended that 

compliance schedules in the Stage 2 

DBPR and LT2ESWTR should be 

consistent. Some commenters also 

suggested that where a small PWS sells 

water to a large PWS, the small PWS 

should comply on the large PWS 

schedule. In response, today’s final rule 

requires PWSs that sell treated drinking 

water to other PWSs to comply 

according to the schedule that applies to 

the largest PWS in the combined 

distribution system. This approach will 

ensure that PWSs have the same 

compliance schedule under both the 

LT2ESWTR and Stage 2 DBPR. 

H. Public Notice Requirements 

1. Today’s Rule 

Today’s rule establishes the following 

public notice requirements: 

• For violations of treatment 

technique requirements, which today’s 

rule establishes for Cryptosporidium 

treatment and for covering or treating 

uncovered finished water reservoirs, 

PWSs must issue a Tier 2 public notice 

and must use existing health effects 

language (except as provided below) for 

microbiological contaminant treatment 

technique violations, as stated in 40 

CFR 141 Subpart Q, Appendix B. 

• For violations of monitoring and 

testing procedure requirements, 

including the failure to collect one or 

two source water Cryptosporidium 

samples, PWSs must issue a Tier 3 

public notice. If the State determines 

that a PWS has failed to collect three or 

more Cryptosporidium samples, the 

PWS must provide a Tier 2 special 

public notice. Violations for failing to 

monitor continue until the State 

determines that the PWS has begun 

sampling on a revised schedule that 

includes dates for collection of missed 

samples. This schedule may also 

include a revised bin determination date 

where necessary. 

• PWSs must report their bin 

classification no later than six months 

after the end of the scheduled 

monitoring period (specific dates in 

section IV.G.). Failure by a PWS to 

collect the required number of 

Cryptosporidium samples to report its 

bin classification by the compliance 

date is a treatment technique violation 

and the PWS must provide a Tier 2 

public notice. The treatment technique 

violation persists until the State 

determines that the PWS is 

implementing a State-approved 

monitoring plan to allow bin 

classification or will install the highest 

level of treatment required under the 

rule. If the PWS has already provided a 

Tier 2 special public notice for missing 

3 sampling dates and is successfully 

meeting a State-approved schedule for 

sampling and bin determination, it need 

not provide a second Tier 2 notice for 

missing the bin determination deadline 

in today’s rule. 

2. Background and Aalysis 

In 2000, EPA published the Public 

Notification Rule (65 FR 25982, May 4, 

2000) (USEPA 2000b), which revised 

the general public notification 

regulations for PWSs in order to 

implement the public notification 

requirements of the 1996 SDWA 

amendments. This regulation 

established the requirements that PWSs 

must follow regarding the form, manner, 

frequency, and content of a public 

notice. Public notification of violations 

is an integral part of the public health 

protection and consumer right-to-know 


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720 Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules and Regulations 

provisions of the 1996 SDWA 

Amendments. 

Owners and operators of PWSs are 

required to notify persons served when 

they fail to comply with the 

requirements of a NPDWR, have a 

variance or exemption from the drinking 

water regulations, or are facing other 

situations posing a risk to public health. 

The public notification requirements 

divide violations into three categories 

(Tier 1, Tier 2 and Tier 3) based on the 

seriousness of the violations, with each 

tier having different public notification 

requirements. 

EPA has limited its list of violations 

and situations routinely requiring a Tier 

1 notice to those with a significant 

potential for serious adverse health 

effects from short term exposure. Tier 1 

violations contain language specified by 

EPA that concisely and in non-technical 

terms conveys to the public the adverse 

health effects that may occur as a result 

of the violation. States and water 

utilities may add additional information 

to each notice, as deemed appropriate 

for specific situations. A State may 

elevate to Tier 1 other violations and 

situations with significant potential to 

have serious adverse health effects from 

short-term exposure, as determined by 

the State. 

Tier 2 public notices address other 

violations with potential to have serious 

adverse health effects on human health. 

Tier 2 notices are required for the 

following situations: 

• All violations of the MCL, 

maximum residual disinfectant level 

(MRDL) and treatment technique 

requirements, except where a Tier 1 

notice is required or where the State 

determines that a Tier 1 notice is 

required; and 

• Failure to comply with the terms 

and conditions of any existing variance 

or exemption. Tier 3 public notices 

include all other violations and 

situations requiring public notice, 

including the following situations: 

• A monitoring or testing procedure 

violation, except where a Tier 1 or 2 

notice is already required or where the 

State has elevated the notice to Tier 1 

or 2; and 

• Operation under a variance or 

exemption. 

The State, at its discretion, may 

elevate the notice requirement for 

specific monitoring or testing 

procedures from a Tier 3 to a Tier 2 

notice, taking into account the potential 

health impacts and persistence of the 

violation. 

As part of the IESWTR, EPA 

established health effects language for 

violations of treatment technique 

requirements for microbiological 

contaminants. EPA believes this 

language, which was developed with 

consideration of Cryptosporidium 

health effects, is appropriate for 

violations of some Cryptosporidium 

treatment requirements under the 

LT2ESWTR. However, for persistent 

monitoring violations and missing the 

deadline for bin determination, EPA is 

promulgating alternative language that 

better informs consumers of the nature 

and potential health consequences of 

the violation. 

As described in section IV.C, EPA 

proposed automatically classifying 

PWSs in the highest treatment bin (Bin 

4) if they fail to complete required 

monitoring. For today’s final rule, EPA 

has determined that providing more 

flexibility to States in dealing with 

PWSs that fail to monitor is appropriate. 

EPA also believes, however, that 

responses to monitoring failures must 

reasonably ensure that PWSs complete 

monitoring as required to determine a 

bin classification within the compliance 

date, or as soon thereafter as possible. 

Moreover, consistent with the public 

health protection and consumer right-toknow provisions of the 1996 SDWA 

Amendments, consumers should be 

informed of these monitoring failures. 

Instead of the proposed automatic Bin 

4 classification for monitoring failures 

under today’s rule, PWSs must provide 

a Tier 3 public notice for monitoring 

violations including up to two missed 

Cryptosporidium samples. If a PWS 

misses three or more Cryptosporidium 

samples (other than the specifically 

exempted situations described in 

section IV.A.1.c), this persistent 

violation requires a Tier 2 public notice. 

This elevated public notice level reflects 

significant concern that persistent 

failure to collect required samples will 

result in the PWS being unable to 

determine its Cryptosporidium 

treatment bin classification and the 

corresponding required treatment level 

by the compliance date. 

Further, if a PWS is unable to 

determine a bin classification by the 

compliance date due to failure to collect 

the required number of 

Cryptosporidium samples, this is a 

treatment technique violation that also 

requires a Tier 2 public notice, unless 

the system is already complying with an 

alternate State-approved schedule for 

monitoring and bin determination. A 

PWS that does not determine its bin 

classification by the required date may 

not be able to comply with the 

Cryptosporidium treatment technique 

requirements of today’s rule by the 

required date and provide the 

appropriate level of public health 

protection. 

3. Summary of Major Comments 

In the August 11, 2003, proposal, EPA 

requested comment on whether 

violations of the treatment requirements 

for Cryptosporidium under the 

LT2ESWTR should require a Tier 2 

public notice and whether the proposed 

health effects language is appropriate 

(USEPA 2003a). Most commenters 

supported requiring a Tier 2 public 

notice for violations of Cryptosporidium 

treatment requirements under the 

LT2ESWTR and agreed that no new 

health effects language is needed for this 

notification. One commenter stated that 

a failure to meet Cryptosporidium 

removal requirements under 

LT2ESWTR should require Tier 1 public 

notice. 

Today’s final rule reflects the views of 

most commenters and is consistent with 

existing regulations in requiring a Tier 

2 public notice for Cryptosporidium 

treatment technique violations. A State 

may elevate a violation to Tier 1 if the 

State determines that the violation 

creates significant potential for serious 

adverse health effects from short-term 

exposure. 

Another commenter agreed that Tier 2 

notice was appropriate but 

recommended that the LT2ESWTR and 

any associated guidance be more 

explicit as to when a treatment 

technique violation occurs with the use 

of microbial toolbox options. As 

described in section IV.D, EPA has 

stated in today’s final rule that failure 

by a PWS in any month to demonstrate 

treatment credit with microbial toolbox 

options equal to or greater than its 

Cryptosporidium treatment 

requirements is a treatment technique 

violation. This violation lasts until the 

PWS demonstrates that it is meeting 

criteria for sufficient treatment credit to 

satisfy its Cryptosporidium treatment 

requirements. 

I. Reporting Source Water Monitoring 

Results 

This section presents specific 

reporting requirements that apply to 

source water monitoring under today’s 

rule, including EPA’s data system for 

reporting and reviewing monitoring 

results. For related requirements, see 

section IV.A for monitoring parameters 

frequency, section IV.J for required 

analytical methods, and section IV.K for 

approved laboratories. General reporting 

requirements under today’s rule and 

associated compliance dates are shown 

in section IV.G. 

1. Today’s Rule 

PWSs must report results from the 

required source water monitoring 


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described in section IV.A no later than 

10 days after the end of the first month 

following the month when the sample is 

collected. For Cryptosporidium 

analyses, PWSs must report the data 

elements specified in Table IV.I–1. For 

samples in which at least 10 L is filtered 

and all of the sample volume is 

analyzed, only the sample volume 

filtered and the number of oocysts 

counted must be reported. Table IV.I–2 

presents the data elements that PWSs 

must report for E. coli and turbidity 

analyses. PWSs, or approved 

laboratories acting as the PWSs’ agents, 

must retain results from 

Cryptosporidium and E. coli monitoring 

until 36 months after bin determination 

for the particular round of monitoring. 

TABLE IV.I–1.—CRYPTOSPORIDIUM DATA ELEMENTS TO BE REPORTED

Data element Reason for data 

element 

Identifying information: 

PWSID ............................................................................................... Needed to associate plant with public water system. 

Facility ID ........................................................................................... Needed to associate sample result with facility. 

Sample collection point ..................................................................... Needed to associate sample result with sampling point. 

Sample collection date ...................................................................... Needed to determine that utilities are collecting samples at the frequency required. 

Sample type (field or matrix spike) 1 ................................................. Needed to distinguish field samples from matrix samples for recovery 

calculations. 

Sample results: 

Sample volume filtered (L), to nearest 1⁄4 L 2 ................................... Needed to verify compliance with sample volume requirements. 

Was 100% of filtered volume examined? 3 ....................................... Needed to calculate the final concentration of oocysts/L and determine 

if volume analyzed requirements are met. 

Number of oocysts counted .............................................................. Needed to calculate the final concentration of oocysts/L. 

1For matrix spike samples, sample volume spiked and estimated number of oocysts spiked must be reported. These data are not required for 

field samples. 2For samples in which <10 L is filtered or <100% of the sample volume is examined, the number of filters used and the packed pellet volume 

must also be reported to verify compliance with LT2ESWTR sample volume analysis requirements. These data are not required for most samples. 3For samples in which <100% of sample is examined, the volume of resuspended concentrate and volume of this resuspension processed 

through IMS must be reported to calculate the sample volume examined. These data are not required for most samples. 

TABLE IV.I–2.—E. COLI AND TURBIDITY DATA ELEMENTS TO BE REPORTED

Data element Reason for collecting data element 

Identifying Information: 

PWS ID .............................................................................................. Needed to associate analytical result with public water system. 

Facility ID ........................................................................................... Needed to associate plant with public water system. 

Sample collection point ..................................................................... Needed to associate sample result with sampling point. 

Sample collection date ...................................................................... Needed to determine that utilities are collecting samples at the frequency required. 

Analytical method number ................................................................. Needed to associate analytical result with analytical method. 

Method Type ..................................................................................... Needed to verify that an approved method was used and call up correct web entry form. 

Source water type ............................................................................. Needed to assess Cryptosporidium indicator relationships. 

E. coli/100 mL ................................................................................... Sample result (although not required, the laboratory also will have the 

option of entering primary measurements for a sample into the 

LT2ESWTR internet-based database to have the database automatically calculate the sample result). 

Turbidity Information: 

Turbidity result ................................................................................... Needed to assess Cryptosporidium indicator relationships. 

PWSs serving at least 10,000 people 

must submit sampling schedules 

(described in section IV.A) and 

monitoring results for the initial source 

water monitoring to EPA electronically 

at the following Internet site: https:// 

intranet.epa.gov/lt2/. These PWSs 

should instruct their laboratories to 

electronically enter results at this site 

using web-based manual entry forms or 

by uploading XML files (extensible 

markup language files—a standard 

format that enables information 

exchange between different systems) 

from laboratory information 

management systems (LIMS). After 

laboratories enter sample results, PWSs 

must review the results on-line at this 

site. The State may approve an 

alternative approach for reporting 

source water monitoring schedules and 

sample results if, for example, a PWS or 

laboratory does not have the capability 

to report data electronically. 

If a PWS believes that its laboratory 

entered a sample result into the data 

system erroneously, the PWS may notify 

the laboratory to rectify the entry. In 

addition, if a PWS believes that a result 

is incorrect, the PWS may electronically 

mark the result as contested and 

petition the State to invalidate the 

sample. If a PWS contests a sample 

result, the PWS should submit a 

rationale to the State, including a 

supporting statement from the 

laboratory, providing a justification. 

PWSs may arrange with laboratories to 

review their sample results prior to the 

results being entered into the EPA data 

system. 

PWSs serving fewer than 10,000 

people must submit sampling schedules 

and monitoring results for the initial 

round of source water monitoring to the 

State. Further, all PWSs must submit 

sampling schedules and monitoring 

results for the second round of 


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722 Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules and Regulations 

monitoring to the State. Regardless of 

the reporting process used, PWSs must 

report an analytical monitoring result to 

the State no later than 10 days after the 

end of the first month following the 

month when the sample was collected. 

2. Background and Analysis 

The reporting requirements for source 

water monitoring in today’s final rule 

reflect those in the August 11, 2003 

proposed LT2ESWTR (USEPA 2003a). 

The data elements that PWSs must 

report for Cryptosporidium and E. coli 

analyses are the minimum necessary to 

identify the sample, determine the 

sample concentration, and verify that 

the PWS complied with rule 

requirements like minimum sample 

volume and approved analytical 

methods. PWSs or laboratories must 

keep bench sheets and slide reports for 

Cryptosporidium analyses for three 

years after bin determination for the 

particular round of monitoring, at which 

time PWSs must be in compliance with 

any additional Cryptosporidium 

treatment requirements based on the 

monitoring results. 

Due to the early implementation 

schedule, EPA expects to partner with 

States to implement initial source water 

monitoring by large PWSs under today’s 

rule. EPA has developed an Internetbased data system to allow electronic 

reporting and review of source water 

monitoring results by laboratories, 

PWSs, States, and EPA. States may use 

this data system to oversee monitoring 

by their PWSs. Where States are unable 

to provide this oversight, the data 

system will allow EPA to implement 

today’s rule. Accordingly, PWSs serving 

at least 10,000 people must use this data 

system to report sampling schedules 

and sample results for the initial round 

of source water monitoring unless the 

State approves an alternative method for 

reporting. 

EPA expects laboratories to report 

analytical results for Cryptosporidium, 

E. coli, and turbidity analyses directly to 

the data system using web forms and 

software that are available free of 

charge. The data system will perform 

logic checks on data entered and will 

calculate results from primary data 

where necessary. This is intended to 

reduce reporting errors and limit the 

time involved in investigating, 

checking, and correcting errors at all 

levels. The LT2ESWTR proposal 

describes the analysis functions of the 

data system in more detail (USEPA 

2003a). 

In general, EPA expects that States 

will implement the initial source water 

monitoring by small PWSs and the 

second round of monitoring by all 

PWSs. Thus, PWSs must submit 

sampling schedules and monitoring 

results for this monitoring to the State. 

Note that where States do not assume 

primacy for the rule, however, EPA will 

act as the State. 

3. Summary of Major Comments 

EPA received significant public 

comment on the following aspects of 

reporting requirements for source water 

monitoring in the August 11, 2003 

proposed LT2ESWTR: the deadline for 

reporting sample results, EPA’s 

electronic data system, and reporting 

results to EPA rather than the State. A 

summary of these comments and EPA’s 

responses follows. 

Some commenters were concerned 

with requiring PWSs to report sample 

results no later than the 10th of the 

second month after the month when the 

sample is collected. Commenters stated 

that this will cause most PWSs to 

sample in the first part of the month, 

which will exacerbate laboratory 

capacity problems. As an alternative, 

commenters recommended that PWSs 

be required to report sample results 72 

days after collection. This approach 

would give all PWSs the same time 

period to report sample results 

regardless of the collection date and 

would facilitate PWSs and laboratories 

scheduling sample collection dates 

more uniformly throughout the month. 

In response, EPA believes that 

requiring PWSs to report monitoring 

results by the 10th of the second month 

after sample collection is appropriate. 

This will maintain consistency with 

existing drinking water regulations, 

which typically require monitoring 

results to be reported by the 10th of the 

following month. Thus, specifying this 

reporting date under today’s rule will 

avoid causing PWSs and States to 

develop different reporting dates for 

different regulations. Due to the time 

required for laboratories to analyze 

Cryptosporidium samples, today’s rule 

gives PWSs an extra month to report 

monitoring results; i.e., the minimum 

time PWSs have to report results is 

approximately 40 days (one month plus 

10 days). This time frame, however, is 

greater than what is necessary for 

laboratories to analyze samples and for 

PWSs to review results. Consequently, 

EPA does not believe that PWSs will 

benefit by collecting a sample at the 

start of a month in comparison to the 

end of a month. 

Many commenters expressed concern 

with the readiness of the electronic data 

system for reporting and reviewing 

monitoring results under today’s rule. 

Commenters stated that PWSs have 

experienced significant problems with 

data systems that supported earlier 

rules, such as the Information Collection 

Rule and the Unregulated Contaminant 

Monitoring Rule. Commenters 

recommended that the data system be in 

place and fully tested prior to 

finalization of the rule and that EPA 

provide training for users. If the data 

system is not available when the rule is 

finalized, commenters asked that the 

monitoring be delayed as specified in 

the Agreement in Principle (USEPA 

2000a). 

EPA has ensured that the LT2 data 

system has been fully tested and 

deployed prior to finalizing the rule. 

During development of the data system, 

EPA has involved stakeholders in a joint 

requirements workgroup, which has 

made recommendations for data system 

characteristics and has participated in 

data system testing. EPA has developed 

guidance and other training materials 

for PWSs, States, and laboratories on 

how to use the data system and will 

provide technical assistance on a 

ongoing basis to data system users. EPA 

believes these steps will help to avoid 

problems that stakeholders experienced 

with data systems for earlier rules. 

Some commenters expressed concerns 

about large PWSs reporting monitoring 

results to EPA. Commenters stated that 

implementation of the rule should be 

administered by States, due to the 

existing relationships States have with 

the PWSs they regulate. For States that 

will implement the rule, commenters 

recommended allowing PWSs to report 

to States, rather than EPA. Commenters 

also requested that EPA provide copies 

of all monitoring data and PWS 

correspondence to States when they 

assume primacy. 

EPA will work with States to 

implement today’s rule and to help 

States assume as much responsibility for 

implementation as they can. Through 

the LT2ESWTR data system, States will 

have full access to monitoring results 

reported by their PWSs. Today’s rule 

also allows States to direct their PWSs 

to report monitoring results directly to 

them, rather than EPA. Further, States 

may require PWSs to submit 

descriptions of monitoring locations for 

approval. In general, EPA will seek to 

involve States in any communications 

with and decisions for their PWSs and 

will allow States to take responsibility 

for these activities if they choose to do 

so. However, because monitoring for the 

largest systems begins before States will 

have had time to assume primacy, EPA 

must be prepared to oversee monitoring 

for these PWSs where States are unable 

to do so. 


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Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules and Regulations 723 

J. Analytical Methods 

1. Analytical Methods Overview 

Today’s final rule requires public 

water systems to conduct LT2ESWTR 

source water monitoring using approved 

methods for Cryptosporidium, E. coli, 

and turbidity analyses. PWSs must meet 

the quality control criteria stipulated by 

the approved methods and additional 

method-specific requirements, as stated 

in this section. Related requirements for 

reporting source water monitoring 

results and using approved laboratories 

are discussed in sections IV.I and IV.K, 

respectively. 

EPA has developed guidance for 

sampling and analyses under the 

LT2ESWTR. The Source Water 

Monitoring Guidance Manual for Public 

Water Systems under the LT2ESWTR 

provides recommendations on activities 

like collecting samples and setting up 

contracts with laboratories. The 

Microbial Laboratory Manual for the 

LT2ESWTR provides information for 

laboratories that conduct analyses. 

These guidance documents may be 

requested from EPA’s Safe Drinking 

Water Hotline, which may be contacted 

as described in the FOR FURTHER

INFORMATION CONTACT section in the 

beginning of this notice, and are 

available on the Internet at 

www.epa.gov/safewater/disinfection/lt2. 

2. Cryptosporidium Methods 

a. Today’s Rule 

Cryptosporidium analysis for source 

water monitoring under today’s rule 

must be conducted using either Method 

1622: Cryptosporidium in Water by 

Filtration/IMS/FA (EPA 815–R–05–001, 

USEPA 2005c) or Method 1623: 

Cryptosporidium and Giardia in Water 

by Filtration/IMS/FA (EPA 815–R–05–

002, USEPA 2005d). Additional method 

requirements for today’s rule include 

the following: 

• For each Cryptosporidium sample, 

at least a 10–L sample volume must be 

analyzed unless a PWS meets one of the 

two exceptions stated in this section. 

PWSs may collect and analyze greater 

than a 10–L sample volume. 

• The first exception to the sample 

volume requirement stems from sample 

turbidity. If a sample is very turbid, it 

may generate a large packed pellet 

volume upon centrifugation (a packed 

pellet refers to the concentrated sample 

after centrifugation has been performed 

in EPA Methods 1622 and 1623). 

Samples resulting in large packed 

pellets must have the sample 

concentrate aliquoted into multiple 

‘‘subsamples’’ for independent 

processing through IMS, staining, and 

examination. PWSs are not required to 

analyze more than 2 mL of packed pellet 

volume per sample. 

• The second exception to the sample 

volume requirement stems from filter 

clogging. In cases where the filter clogs 

prior to filtration of 10 L, the PWS must 

analyze as much sample volume as can 

be filtered by 2 filters, up to a packed 

pellet volume of 2 mL. This condition 

applies only to filters that have been 

approved by EPA for nationwide use 

with Methods 1622 and 1623—the Pall 

Gelman EnvirochekTM and 

EnvirochekTM HV filters, the IDEXX 

Filta-MaxTM foam filter, and the 

Whatman CrypTestTM cartridge filter. 

• Methods 1622 and 1623 include 

fluorescein isothiocyanate (FITC) as the 

primary antibody stain for 

Cryptosporidium detection, DAPI 

staining to detect nuclei, and DIC to 

detect internal structures. Under today’s 

rule, PWSs must report total 

Cryptosporidium oocysts as detected by 

FITC as determined by the color (apple 

green or alternative stain color approved 

for the laboratory under the Lab QA 

Program described in section IV.K), size 

(4–6 micrometers) and shape (round to 

oval). This total includes all of the 

oocysts identified as described here, less 

any atypical organisms identified by 

FITC, DIC, or DAPI (e.g., possessing 

spikes, stalks, appendages, pores, one or 

two large nuclei filling the cell, red 

fluorescing chloroplasts, crystals, 

spores, etc.). 

• As required by Method 1622 and 

1623, PWSs must have 1 matrix spike 

(MS) sample analyzed for each 20 

source water samples. The volume of 

the MS sample must be within ten 

percent of the volume of the unspiked 

sample that is collected at the same 

time, and the samples must be collected 

by splitting the sample stream or 

collecting the samples sequentially. The 

MS sample and the associated unspiked 

sample must be analyzed by the same 

procedure. MS samples must be spiked 

and filtered in the laboratory. However, 

if the volume of the MS sample is 

greater than 10 L, the PWS is permitted 

to filter all but 10 L of the MS sample 

in the field, and ship the filtered sample 

and the remaining 10 L of source water 

to the laboratory. In this case, the 

laboratory must spike the remaining 10 

L of water and filter it through the filter 

that was used to collect the balance of 

the sample in the field. 

• Laboratories must use flow 

cytometer-counted spiking suspensions 

for spiked QC samples. 

b. Background and Analysis 

The M–DBP Advisory Committee 

recommended the use of Methods 1622 

or 1623 and a minimum sample volume 

of 10 L for source water 

Cryptosporidium analyses under the 

LT2ESWTR. The August 11, 2003 

proposed rule reflected these 

recommendations, with associated QC 

requirements and exceptions to the 

minimum sample volume for samples 

that are highly turbid or cause 

significant filter clogging (USEPA 

2003a). Today’s final rule is unchanged 

from the proposal in these respects. 

Today’s rule requires the use of 

methods 1622 or 1623 because they are 

the best available methods that have 

undergone full validation testing. As 

described in section III.E, these methods 

were used during the ICRSS, where MS 

samples indicated a mean recovery and 

relative standard deviation of 43 and 47 

percent, respectively (Connell et al. 

2000). EPA expects that PWSs will 

achieve comparable performance with 

these methods during source water 

monitoring under today’s rule. With the 

minimum sample volume and QC 

requirements in today’s rule, this level 

of performance will be sufficient to 

assign PWSs to Cryptosporidium 

treatment bins and realize the public 

health goals intended by EPA and the 

Advisory Committee for the 

LT2ESWTR. EPA has also approved 

these methods for ambient water 

monitoring under a separate rulemaking 

(68 FR 43272, July 21, 2003) (USEPA 

2003b). 

The proposed LT2ESWTR required 

the use of April 2001 versions of 

Methods 1622 or 1623 and requested 

comment on approving revised versions 

of these methods in the final rule 

(USEPA 2003a). The revised methods 

were included in the proposal as draft 

June 2003 versions. The revisions in 

these versions included increased 

flexibility in some QC requirements, 

clarification of certain method 

procedures, an increase in the allowable 

sample storage temperature to 10°C, the 

addition of several approved analysis 

modifications, and other refinements 

(see the proposed rule for 

details)(USEPA 2003a). 

Today’s rule requires the use of the 

revised versions of Methods 1622 and 

1623. In the versions of these methods 

finalized with today’s rule, the upper 

temperature limit for sample receipt has 

been increased to 20°C. This change 

responds to public comment and recent 

publications (Ware and Schafer 2005, 

Francy et al. 2004, Nichols et al. 2004). 

As described in section IV.A, PWSs may 

grandfather data generated with earlier 

approved versions of these methods 

(i.e., 1999 or 2001 versions). 


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724 Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules and Regulations 

c. Summary of Major Comments 

Public comment on the August 11, 

2003 proposed LT2ESWTR supported 

approval of the revised versions of 

Methods 1622 and 1623, which today’s 

rule establishes for source water 

Cryptosporidium monitoring. EPA also 

received comment regarding the lack of 

viability and infectivity information 

with these methods and requirements 

for analyzing QC samples. 

Several commenters were concerned 

that Methods 1622 and 1623 do not 

indicate whether a Cryptosporidium 

oocyst is viable and infectious. While 

EPA recognizes that these methods do 

not provide information on 

Cryptosporidium infectivity, EPA’s 

analysis indicates that they can perform 

effectively for identifying those PWSs 

that should provide additional 

Cryptosporidium treatment (USEPA 

2005a). This analysis is based on the 

actual performance of these methods in 

the ICRSS. Further, EPA and the M–DBP 

Advisory Committee, which 

recommended Methods 1622 and 1623, 

accounted for this lack of information 

on infectivity when designing the 

Cryptosporidium treatment bins in 

today’s rule. EPA has not identified any 

feasible methods for quantifying 

Cryptosporidium infectivity in a 

national monitoring program. 

Several commenters suggested that 

laboratories should only be required to 

perform one OPR test per day instead of 

one for every 20 samples, as Methods 

1622 and 1623 require. EPA believes, 

however, that the frequency of one OPR 

test per 20 samples is appropriate for 

identifying and correcting problems. For 

example, if an OPR test is performed 

once per day for a laboratory that 

processes 60 samples per day, a problem 

that occurs at sample 10 will be 

continued through the next 50 samples. 

If an OPR test is performed once per 20 

samples, a problem that occurs at 

sample 10 would only affect 10 

additional samples. Consequently, EPA 

is maintaining the current QC criteria in 

Methods 1622 and 1623. 

3. E. coli Methods 

a. Today’s Rule 

For enumerating source water E. coli 

density under the LT2ESWTR, EPA is 

approving the same methods that are 

currently approved for ambient water 

monitoring under 40 CFR 136.3. EPA 

established these methods through the 

rulemaking ‘‘Guidelines Establishing 

Test Procedures for the Analysis of 

Pollutants; Analytical Methods for 

Biological Pollutants in Ambient Water’’

(USEPA 2003b). Table IV.J–1 

summarizes these methods. Method 

identification numbers are provided for 

applicable standards published by EPA 

and voluntary consensus standards 

bodies including Standard Methods, 

American Society of Testing Materials 

(ASTM), and the Association of 

Analytical Chemists (AOAC). 

TABLE IV.J–1.—LIST OF APPROVED ANALYTICAL METHODS FOR E. COLI 1

Method EPA Standard Methods 18th, 

19th, 20th Ed. ASTM AOAC Other 

MPN 234, multiple tube ........................... ..................... 9221B.1/9221F 567.

Multiple tube/multiple well ...................... ..................... 9223B5 8 ........................... ..................... 991.15 9 ....... Colilert 8 10, Colilert18 8 10 11. 

MF 2 3 12 13 14 two step, or ........................ 1103.1 16 ..... 9222B/9222G5 15 9213D 5 D5392–93 17.

Single step .............................................. 1603 18, 

1604 19.

.......................................... ..................... ..................... mColiBlue 24 20. 

1 Recommended for enumeration of E. coli in ambient water only, number per 100 ml. 

2Tests must be conducted to provide organism enumeration (density). Select the appropriate configuration of tubes/filtrations and dilutions/volumes to account for the quality, character, consistency, and anticipated organism density of the water sample. 3To assess the comparability of results obtained with individual methods, it is suggested that side-by-side tests be conducted across seasons 

of the year with the water samples routinely tested in accordance with the most current Standard Methods for the Examination of Water and 

Wastewater or EPA alternate test procedure (ATP) guidelines. 4Samples shall be enumerated by the multiple-tube or multiple-well procedure. Using multiple-tube procedures, employ an appropriate tube 

and dilution configuration of the sample as needed and report the Most Probable Number (MPN). Samples tested with Colilert may be enumerated with the multiple-well procedures, Quanti-tray, or Quanti-tray 2000, and the MPN calculated from the table provided by the manufacturer. 5APHA. 1998, 1995, 1992. Standard Methods for the Examination of Water and Wastewater. American Public Health Association. 20th, 19th, 

and 18th Editions. Amer. Publ. Hlth. Assoc., Washington, DC. 6The multiple-tube fermentation test is used in 9221.B.1. Lactose broth may be used in lieu of lauryl tryptose broth (LTB), if at least 25 parallel 

tests are conducted between this broth and LTB using the water samples normally tested, and this comparison demonstrates that the false-positive rate and false-negative rate for total coliform using lactose broth is less than 10 percent. No requirement exists to run the completed phase 

on 10 percent of all total coliform-positive tubes on a seasonal basis. 7After prior enrichment in a presumptive medium for total coliform using 9221B.1, all presumptive tubes or bottles showing any amount of gas, 

growth or acidity within 48± 3 h of incubation shall be submitted to 9221F. Commercially available EC–MUG media or EC media supplemented in 

the laboratory with 50 μg/ml of MUG may be used. 8These tests are collectively known as defined enzyme substrate tests, where, for example, a substrate is used to detect the enzyme glucuronidase produced by E. coli. 9AOAC. 1995. Official Methods of Analysis of AOAC International, 16th Edition, Volume 1, Chapter 17. Association of Official Analytical Chemists International. 481 North Frederick Avenue, Suite 500, Gaithersburg, Maryland 20877–2417. 10 Descriptions of the Colilert, Colilert-18, Quanti-Tray and Quanti-Tray 2000 may be obtained from IDEXX Laboratories, Inc., One IDEXX 

Drive, Westbrook, Maine 04092. 11 Colilert-18 is an optimized formulation of the Colilert for the determination of total coliforms and E. coli that provides results within 18 h of 

incubation at 35 °C rather than the 24 h required for the Colilert test and is recommended for marine samples. 12A 0.45 μm membrane filter (MF) or other pore size certified by the manufacturer to fully retain organisms to be cultivated and to be free of 

extractables which could interfere with their growth. 13Because the MF technique usually yields low and variable recovery from chlorinated wastewaters, the Most Probable Number method will be 

required to resolve any controversies. 14When the MF method has not been used previously to test ambient water with high turbidity, large number of noncoliform bacteria, or samples that may contain organisms stressed by chlorine, a parallel test should be conducted with a multiple-tube technique to demonstrate applicability and comparability of results. 15Subject total coliform positive samples as determined by 9222B or other membrane filter procedure to 9222G using NA–MUG media. 16 USEPA. 2002c. Method 1103.1: Escherichia coli (E. coli) In Water By Membrane Filtration Using membrane-Thermotolerant Escherichia coli 

Agar (mTEC). U.S. Environmental Protection Agency, Office of Water, Washington, DC. EPA–821–R–02–020. 17ASTM. 2000, 1999, 1996. Annual Book of ASTM Standards—Water and Environmental Technology. Section 11.02. American Society for 

Testing and Materials. 100 Barr Harbor Drive, West Conshohocken, PA 19428. 


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Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules and Regulations 725 

18 USEPA. 2002. Method 1610: Escherichia coli (E. coli) In Water By Membrane Filtration Using Modified membrane-Thermotolerant Escherichia coli Agar (modified mTEC). U.S. Environmental Protection Agency, Office of Water, Washington, DC. EPA–821–R–02–023. 19Preparation and use of MI agar with a standard membrane filter procedure is set forth in the article, Brenner et al. 1993. ‘‘New Medium for 

the Simultaneous Detection of Total Coliform and Escherichia coli in Water.’’ Appl. Environ. Microbiol. 59:3534–3544 and in USEPA. 2002. Method 1604: Total Coliforms and Escherichia coli (E. coli) in Water by Membrane Filtration by Using a Simultaneous Detection Technique (MI Medium). U.S. Environmental Protection Agency, Office of Water, Washington, DC. EPA–821–R–02–024. 20A description of the mColiBlue24 test, Total Coliforms and E. coli, is available from Hach Company, 100 Dayton Ave., Ames, IA 50010. 

For most PWSs, the time from sample 

collection to initiation of analysis (i.e., 

the holding time) for source water E. 

coli samples may not exceed 30 hours 

for all approved E. coli methods. 

However, if the State determines on a 

case-by-case basis that analyzing an E. 

coli sample within 30 hours is not 

feasible, the State may approve the 

holding of an E. coli sample for up to 

48 hours between collection and 

initiation of analysis. E. coli samples 

held between 30 to 48 hours must be 

analyzed by the Colilert reagent version 

of Standard Method 9223B as listed in 

40 CFR 136.3. All E. coli samples must 

be maintained below 10° C and not 

allowed to freeze. 

The E. coli sample holding time 

established for source water monitoring 

under the LT2ESWTR does not apply to 

E. coli sample holding time 

requirements that have been established 

under other programs and regulations. 

b. Background and Analysis 

In the August 11, 2003 proposed 

LT2ESWTR, EPA planned to approve 

the same E. coli methods that the 

Agency had proposed for ambient water 

monitoring in an earlier rulemaking, 

‘‘Guidelines Establishing Test 

Procedures for the Analysis of 

Pollutants; Analytical Methods for 

Biological Pollutants in Ambient Water’’

(USEPA 2001h). EPA selected these 

methods based on data generated by 

EPA laboratories, submissions to the 

EPA alternate test procedures program 

and voluntary consensus standards 

bodies, peer reviewed journal articles, 

and publicly available study reports. 

On July 21, 2003, EPA finalized 

‘‘Guidelines Establishing Test 

Procedures for the Analysis of 

Pollutants; Analytical Methods for 

Biological Pollutants in Ambient Water’’

(USEPA 2003b). The only method from 

the proposal of this rule that was not 

included in the final rule was Colisure, 

which was excluded due to insufficient 

data on its performance with surface 

water. For the other methods, EPA 

revised certain titles and added method 

numbers to be consistent with other 

microbiological methods, but the 

technical content of these methods in 

the final rule did not change from the 

versions included in the proposed rule. 

EPA is approving these same E. coli 

methods for analyses under the 

LT2ESWTR. The source water E. coli 

analyses that PWSs will conduct under 

the LT2ESWTR are similar to the 

ambient water analyses for which EPA 

approved E. coli methods under 

‘‘Guidelines Establishing Test 

Procedures for the Analysis of 

Pollutants; Analytical Methods for 

Biological Pollutants in Ambient Water’’

(USEPA 2003b). EPA continues to 

support the findings of this rule and 

believes that the E. coli methods 

approved therein have the necessary 

sensitivity and specificity to meet the 

data quality objectives of the 

LT2ESWTR. 

An important aspect of monitoring for 

E. coli is the allowable sample holding 

time (i.e., the time between sample 

collection and initiation of analysis). 

Existing regulations, such as 40 CFR 

141.74, limit the holding time for E. coli 

samples to 8 hours. However, for PWSs 

that must ship E. coli samples to an offsite laboratory for analysis, meeting an 

8 hour holding time is generally not 

feasible. For example, during the ICRSS, 

all of the PWSs that shipped samples 

off-site for E. coli analysis exceeded an 

8 hour holding time, and 12 percent of 

these samples had holding times in 

excess of 30 hours. 

While most large PWSs that will 

monitor for E. coli under the 

LT2ESWTR will conduct these analyses 

on-site, most small PWSs must ship 

samples off-site to an approved 

laboratory. To address the concern that 

PWSs using off-site laboratories cannot 

meet an 8-hour holding time, EPA 

participated in studies to assess the 

effect of increased sample holding time 

on E. coli analysis results. These studies 

are summarized in the proposed rule 

(USEPA 2003a) and are described in 

detail in Pope et al. (2003). Based on 

these studies, EPA has concluded that 

the holding time for E. coli samples can 

be extended beyond 8 hours prior to 

analysis without compromising the data 

quality objectives of LT2ESWTR 

monitoring. 

In the proposed LT2ESWTR, EPA 

required analysis of E. coli samples to 

be initiated within 24 hours of sample 

collection and required that samples be 

kept below 10° C and not allowed to 

freeze (USEPA 2003a). These proposed 

requirements were based on data 

showing that most samples maintained 

within these temperature conditions 

were not significantly different at 24 

hours than at the standard holding time 

of 8 hours. The proposal also noted that 

data indicated no significant sample 

degradation after longer time periods, 

such as 30 or 48 hours, for certain 

methods. Accordingly, EPA requested 

comment on establishing a longer E. coli 

holding time in the final rule. 

For today’s final rule, EPA is 

establishing a holding time of 30 hours 

for all approved E. coli methods. After 

reviewing public comment on this issue, 

which is summarized in the following 

section, and reassessing the studies 

described in the proposed rule, EPA has 

concluded that a 30 hour holding time 

limit for E. coli samples is appropriate 

and consistent with the data quality 

objectives of LT2ESWTR source water 

monitoring. Further, EPA believes that 

meeting a 30 hour holding time is 

feasible for most PWSs that must ship 

E. coli samples to an off-site laboratory 

for analysis. This longer holding time, 

however, does not apply to E. coli 

monitoring conducted under other 

programs and regulations. 

EPA recognizes that in rare cases, 

having an E. coli sample analyzed 

within 30 hours may not be feasible for 

a PWS due to distance to an approved 

laboratory and limited transportation 

options. In these cases, today’s rule 

allows the State to approve up to a 48 

hour holding time for E. coli samples. 

Samples held between 30 to 48 hours 

must be analyzed by the Colilert reagent 

version of Standard Method 9223B. This 

is the only method evaluated in Pope et 

al. (2003) where no significant sample 

degradation occurred at 48 hours. 

PWSs must maintain samples below 

10°C and not allow them to freeze. EPA 

has developing guidance for PWSs on 

packing and shipping E. coli samples to 

maintain these temperature conditions. 

See the overview at the beginning of this 

section for information on how to access 

this guidance. 

c. Summary of Major Comments 

In the August 11, 2003 LT2ESWTR 

proposal, EPA requested comment on 

whether the E. coli methods proposed 

for approval under the LT2ESWTR are 

appropriate and whether there are 

additional methods not proposed that 

should be considered. EPA also 

requested comment on the proposal to 

extend the holding time for E. coli 


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samples to 24 hours; whether EPA 

should limit the extended holding time 

to only those E. coli analytical methods 

that were evaluated in the holding time 

studies described in the proposal; and 

whether EPA should increase the source 

water E. coli holding time to 30 or 48 

hours for samples evaluated by one 

method, ONPG–MUG, and retain a 24- 

hour holding time for samples analyzed 

by other methods. 

Most commenters stated that the 

proposed E. coli analytical methods are 

appropriate. Commenters also agreed 

with the proposal to extend the holding 

time for source water E. coli samples, 

but recommendations about the 

maximum holding time and the 

methods to which the extended holding 

time should apply differed among 

commenters. Some suggested that EPA 

increase the holding time to 30 hours for 

the ONPG–MUG method, but retain a 

24-hour holding time for the other 

methods. Other commenters 

recommended a 48-hour holding time 

for some or all methods. Several 

commenters advised that holding times 

for all methods should be the same to 

limit confusion. Some commenters were 

concerned that a 30-hour holding time 

would not be sufficient for small PWSs 

in remote areas to ship samples to 

distant laboratories. 

After consideration of the comments 

received, as well as the holding time 

study data presented in the proposed 

rule and the time required to ship 

samples off-site for analysis as 

evidenced in the ICRSS, EPA has 

concluded that allowing a 30-hour 

holding time for all E. coli methods 

approved under today’s final rule is 

appropriate. Data indicate that a 30-hour 

holding time for E. coli samples will not 

adversely impact the data quality 

objectives of LT2ESWTR monitoring. 

Further, establishing the same holding 

time for all methods will limit 

confusion, and a 30-hour holding time 

will allow most PWSs that ship samples 

off site for analysis to meet the holding 

time requirements. Today’s rule also 

allows the State to authorize a 48-hour 

holding time for rare cases where a 30- 

hour holding time is not feasible. 

4. Turbidity Methods 

a. Today’s Rule 

Today’s rule requires PWSs to use the 

analytical methods that have been 

previously approved by EPA for 

analysis of turbidity in drinking water, 

as listed in 40 CFR 141.74. These are 

Method 2130B as published in Standard 

Methods for the Examination of Water 

and Wastewater (APHA 1992), EPA 

Method 180.1 (USEPA 1993), Great 

Lakes Instruments Method 2 (Great 

Lakes Instruments 1992), and Hach 

FilterTrak Method 10133. 

b. Background and Analysis 

As stated in section IV.A, today’s rule 

requires filtered PWSs serving at least 

10,000 people to monitor for turbidity 

when they conduct source water 

monitoring. EPA may use these data to 

modify the indicator criteria that trigger 

Cryptosporidium monitoring by small 

filtered PWSs, as recommended by the 

M–DBP Advisory Committee (USEPA 

2000a). In addition, PWSs using 

conventional or direct filtration may 

achieve additional Cryptosporidium 

treatment credit by demonstrating very 

low turbidity in the combined filter 

effluent, as described in section IV.D.7, 

or the individual filter effluent, as 

described in section IV.D.8. 

The August 11, 2003 proposed 

LT2ESWTR required PWSs to use 

turbidity methods that EPA had 

previously approved under 40 CFR 

141.74 for analyzing drinking water 

(USEPA 2003a). These are EPA Method 

180.1 and Standard Method 2130B, 

which are based on a comparison of the 

intensity of light scattered by the sample 

with the intensity of light scattered by 

a standard reference suspension; Great 

Lakes Instruments Method 2, which is a 

modulated four beam infrared method 

using a ratiometric algorithm to 

calculate the turbidity value from the 

four readings that are produced; and 

Hach FilterTrak (Method 10133), which 

is a laser-based method used to analyze 

finished drinking water. 

Today’s final rule is unchanged from 

the proposal in regard to analytical 

methods for turbidity. Hence, PWSs 

must use methods currently approved in 

40 CFR 141.74 for turbidity analysis. 

EPA believes the currently approved 

methods are appropriate for turbidity 

analyses that will be conducted under 

the LT2ESWTR. PWSs must use 

turbidimeter instruments as described 

in the EPA-approved methods, which 

may be either on-line or bench top 

instruments. If a PWS chooses to use online instruments for monitoring 

turbidity, the PWS must validate the 

continuous measurements for accuracy 

on a regular basis using a protocol 

approved by the State, as required in 40 

CFR 141.74. 

c. Summary of Major Comments 

EPA received public comment on the 

turbidity methods required in the 

August 11, 2003 proposed LT2ESWTR. 

While commenters, in general, agreed 

that currently approved turbidity 

methods are adequate to meet the 

requirements of the rule, several 

commenters were concerned with 

turbidity measurement variation among 

different instruments. One commenter 

suggested voluntary third party testing, 

while another recommended more 

rigorous calibration and verification 

processes. 

As described in section IV.D.7, EPA 

has reviewed studies of low level 

turbidity measurements, as well as 

standard test methods for measurement 

of turbidity below 5 NTU. After 

reviewing this information, EPA 

concluded that currently available 

monitoring equipment can reliably 

measure turbidity at levels of 0.15 NTU 

and lower. However, EPA agrees that 

rigorous calibration and maintenance of 

turbidity monitoring equipment is 

necessary for PWSs pursuing the low 

filtered water turbidity performance 

options in the microbial toolbox. EPA 

has developed guidance on proper 

calibration, operation, and maintenance 

of turbidimeters (USEPA 1999c). 

A few commenters stated that the 

LT2ESTWR does not recognize 

advancements in turbidity measurement 

and newly developed turbidity 

measurement technologies. In response, 

EPA has not received information that 

supports approval of analytical methods 

for turbidity in addition to those 

currently approved under 40 CFR 

141.74, which are also approved for 

turbidity monitoring under today’s rule. 

If other turbidity methods are approved 

and added to 40 CFR 141.74 in the 

future, these methods will also be 

approved under the LT2ESWTR. 

One commenter requested that the 

LT2ESWTR specifically address 

turbidity measurements in plants that 

practice lime softening. EPA notes that 

additional treatment credit for 

combined filter effluent turbidity is 

based on measurements collected under 

40 CFR 141.173 or 40 CFR 141.551 (the 

IESWTR or LT1ESWTR). These 

regulations allow PWSs that use lime 

softening to acidify samples prior to 

analysis in order to address the effects 

of lime softening on turbidity 

measurements. In regard to treatment 

credit based on individual filter effluent 

turbidity, EPA does not believe that 

acidifying samples while measuring 

turbidity every 15 minutes at each 

individual filter, as the IESWTR and 

LT1ESWTR require, is feasible. 

However, PWSs that practice lime 

softening could use the demonstration 

of performance toolbox option to 

demonstrate that a plant is achieving 

removal efficiencies equivalent to the 

additional credit allowed for individual 

filter performance. 


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K. Laboratory Approval 

Given the potentially significant 

implications for PWSs and drinking 

water consumers of microbial 

monitoring under the LT2ESWTR, 

laboratory analyses for 

Cryptosporidium, E. coli, and turbidity 

should be accurate and reliable within 

the limits of approved methods. 

Therefore, today’s final rule requires 

PWSs to use laboratories that have been 

approved to conduct analyses for these 

parameters by EPA or the State. 

1. Cryptosporidium Laboratory 

Approval 

a. Today’s Rule 

Analysis of samples for 

Cryptosporidium under today’s rule 

must be conducted by a laboratory that 

is approved under EPA’s Laboratory 

Quality Assurance Evaluation Program 

(Lab QA Program) for Analysis of 

Cryptosporidium in Water (described in 

67 FR 9731, March 4, 2002, USEPA 

2002d). A list of laboratories that are 

approved under this program is 

available on the Internet at 

www.epa.gov/safewater/disinfection/lt2. 

If a State adopts an equivalent approval 

process under a State laboratory 

certification program, then PWSs can 

use laboratories approved by the State. 

b. Background and Analysis 

Because States do not currently 

approve laboratories for 

Cryptosporidium analyses, EPA has 

assumed initial responsibility for 

Cryptosporidium laboratory approval. 

EPA initiated the Cryptosporidium Lab 

QA Program prior to LT2ESWTR 

promulgation to ensure that adequate 

analytical capacity will be available at 

approved laboratories to support 

required monitoring, which begins 6 

months after rule promulgation. The 

August 11, 2003 proposed LT2ESWTR 

required PWSs to have Cryptosporidium 

samples analyzed by laboratories 

approved under the EPA Lab QA 

Program. Today’s final rule is 

unchanged from the proposal with 

respect to this requirement. 

Laboratories seeking approval under 

the EPA Lab QA Program for 

Cryptosporidium analysis must submit 

an interest application to EPA, 

successfully analyze a set of initial 

performance testing samples, and 

undergo an on-site evaluation. 

Laboratories that pass the quality 

assurance evaluation are approved for 

Cryptosporidium analysis under the 

LT2ESWTR. To maintain approval, 

laboratories must successfully analyze a 

set of three ongoing proficiency testing 

samples approximately every four 

months. The Lab QA Program is 

described in detail in USEPA (2002d) 

and additional information can be found 

on the Internet at www.epa.gov/ 

safewater/disinfection/lt2. 

EPA tracks the Cryptosporidium 

sample analysis capacity of approved 

laboratories through the Lab QA 

Program. Using information provided by 

laboratories, EPA expects that existing 

capacity should be sufficient to support 

initial source water monitoring by large 

PWSs under the LT2ESWTR. Further, 

the implementation schedule for today’s 

rule, which is described in section IV.G, 

provides time for laboratories to 

increase capacity through steps like 

training new analysts as the demand for 

sample analysis grows. 

c. Summary of Major Comments 

In regard to approval of laboratories 

for Cryptosporidium analysis, major 

comments on the August 11, 2003 

proposal addressed the following issues: 

laboratory capacity, State approval 

programs, and analyst experience 

criteria. Comments regarding 

Cryptosporidium laboratory capacity are 

summarized in section IV.G, while those 

on the other issues are summarized as 

follows. 

EPA requested comment on States 

approving Cryptosporidium 

laboratories. Most commenters, 

however, recommended that EPA 

maintain the Lab QA Program, due to 

the specialized nature of the work. EPA 

intends to maintain the Lab QA 

Program, but today’s rule does allow 

States to certify Cryptosporidium 

laboratories by setting up an equivalent 

program. 

EPA also requested comment on the 

experience criteria that Methods 1622 

and 1623 include for Cryptosporidium 

analysts. Some commenters 

recommended lowering analyst training 

and experience requirements, while 

others recommended no change or an 

increase in microscopy training. After 

evaluating these comments, EPA has 

concluded that the analyst criteria 

included in Methods 1622 and 1623 are 

reasonable for ensuring that analysts 

have the experience to evaluate source 

water samples under today’s rule. 

Consequently, EPA has not altered these 

criteria from the approved methods. 

2. E. coli Laboratory Approval 

a. Today’s Rule 

PWSs must have E. coli samples 

analyzed by a laboratory that has been 

certified by EPA, the National 

Environmental Laboratory Accreditation 

Conference (NELAC) or the State for 

total coliform or fecal coliform analysis 

in drinking water under 40 CFR 141.74. 

The laboratory must use the same 

technique for E. coli analysis under 

today’s rule that the laboratory is 

certified to use for drinking water under 

40 CFR 141.74 (e.g., membrane 

filtration, multiple-well, multiple-tube). 

b. Background and Analysis 

The August 11, 2003 proposed 

LT2ESWTR required PWSs to have E. 

coli samples analyzed by laboratories 

that are certified to conduct total or 

fecal coliform analyses in drinking 

water (i.e., under 40 CFR 141.74) by 

EPA, NELAC or the State. The proposal 

required laboratories to use the same E. 

coli analytical technique that they are 

certified to use for coliform analyses in 

drinking water. Today’s final rule is 

unchanged from the proposal in regard 

to these requirements. EPA believes that 

laboratories that are certified to conduct 

coliform analyses in drinking water 

have the expertise to conduct E. coli 

analyses under today’s rule, provided 

they use the analytical technique for 

which they are certified. 

c. Summary of Major Comments 

Two commenters on the August 11, 

2003 proposal suggested that 

laboratories should be certified 

specifically for quantitative analyses of 

total or fecal coliform in a source water 

matrix. However, the methods approved 

for source water E. coli analyses under 

today’s rule are also approved under the 

drinking water certification program. 

EPA believes that analysts certified for 

these methods under the drinking water 

certification program have the capability 

to perform the same methods for a 

source water matrix, even though 

additional steps may be required (such 

as dilutions). EPA has revised the 

Laboratory Certification Manual to 

suggest Performance Evaluation (PE) 

samples for source water matrix 

analyses and States have the option to 

require PE samples as needed in their 

State laboratory certification programs. 

3. Turbidity Analyst Approval 

a. Today’s Rule 

Under today’s rule, measurements of 

turbidity must be made by a party 

approved by the State. 

b. Background and Analysis 

The August 11, 2003 proposed 

LT2ESWTR required that measurements 

of turbidity be made by a party 

approved by the State. This reflects 

existing requirements in 40 CFR 141.74 

for measurement of turbidity in drinking 

water. Today’s final rule is unchanged 

from the proposal in this respect. 


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c. Summary of Major Comments 

Commenters on requirements for 

turbidity analyst approval in the August 

11, 2003 proposal agreed that turbidity 

analyses should be consistent with 40 

CFR 141.74. Specifically, any person 

that is currently approved to conduct 

turbidity analysis under existing 

drinking water regulations should be 

approved to conduct turbidity analyses 

under the LT2ESWTR. EPA agrees with 

this comment and it is reflected in 

today’s final rule. 

L. Requirements for Sanitary Surveys 

Conducted by EPA 

1. Today’s Rule 

Today’s final rule establishes 

requirements for PWSs to respond to 

significant deficiencies identified in 

sanitary surveys that EPA conducts. 

These requirements give EPA authority 

equivalent to that exercised by States 

under existing regulations to ensure that 

PWSs address significant deficiencies. 

• For sanitary surveys conducted by 

EPA under SDWA section 1445 or other 

authority, PWSs must respond in 

writing to significant deficiencies 

outlined in sanitary survey reports no 

later than 45 days after receipt of the 

report, indicating how and on what 

schedule the PWS will address 

significant deficiencies noted in the 

survey. 

• PWSs must correct significant 

deficiencies identified in sanitary 

survey reports according to the schedule 

approved by EPA, or if there is no 

approved schedule, according to the 

schedule the PWS reported if such 

deficiencies are within the control of the 

PWS. 

• A sanitary survey, as conducted by 

EPA, is an onsite review of the water 

source (identifying sources of 

contamination by using results of source 

water assessments where available), 

facilities, equipment, operation, 

maintenance, and monitoring 

compliance of a PWS to evaluate the 

adequacy of the PWS, its sources and 

operations, and the distribution of safe 

drinking water. A significant deficiency 

includes a defect in design, operation, 

or maintenance, or a failure or 

malfunction of the sources, treatment, 

storage, or distribution system that EPA 

determines to be causing, or has the 

potential for causing the introduction of 

contamination into the water delivered 

to consumers. 

2. Background and Analysis 

As established by the IESWTR in 40 

CFR 142.16(b)(3), primacy States must 

conduct sanitary surveys for PWSs 

using surface water sources every three 

or five years. The sanitary survey is an 

onsite review of the following: (1) 

Source, (2) treatment, (3) distribution 

system, (4) finished water storage, (5) 

pumps, pump facilities, and controls, 

(6) monitoring, reporting, and data 

verification, (7) system management and 

operation, and (8) operator compliance 

with State requirements. 

Under the IESWTR, primacy States 

must have the authority to assure that 

PWSs respond in writing to significant 

deficiencies identified in sanitary 

survey reports no later than 45 days 

after receipt of the report, indicating 

how and on what schedule the system 

will address the deficiency (40 CFR 

142.16(b)(1)(ii)). Further, primacy States 

must have the authority to assure that 

systems take necessary steps to address 

significant deficiencies identified in 

sanitary survey reports if such 

deficiencies are within the control of the 

system and its governing body (40 CFR 

142.16(b)(1)(iii)). 

EPA conducts sanitary surveys under 

SDWA section 1445 for PWSs not 

regulated by primacy States (e.g., Tribal 

systems, Wyoming). However, the 

authority required of primacy States 

under 40 CFR 142 to ensure that PWSs 

address significant deficiencies 

identified during sanitary surveys does 

not extend to EPA. Consequently, the 

sanitary survey requirements 

established by the IESWTR created an 

unequal standard. PWSs regulated by 

primacy States are subject to the States’

authority to require correction of 

significant deficiencies noted in sanitary 

survey reports, while PWSs for which 

EPA has direct implementation 

authority did not have to meet an 

equivalent requirement. 

In the August 11, 2003 proposal, EPA 

requested comment on establishing 

requirements under 40 CFR 141 for 

PWSs to correct significant deficiencies 

identified in sanitary surveys conducted 

by EPA. The requirements in today’s 

final rule follow closely on the language 

presented in the proposal. Today’s rule 

ensures that PWSs in non-primacy 

States are subject to comparable 

requirements for sanitary surveys as 

PWS regulated by States with primacy. 

3. Summary of Major Comments 

Most public comment on the August 

11, 2003 proposal supported requiring 

PWSs to correct significant deficiencies 

identified in sanitary surveys conducted 

by EPA. Commenters stated that 

requirements for sanitary surveys 

should be consistent for PWSs and 

should not depend on the primacy 

agency. EPA believes the requirements 

in today’s final rule will establish this 

consistency. 

One commenter requested that EPA 

include a process for PWSs to appeal a 

significant deficiency determination. 

EPA expects that PWSs will raise any 

concerns regarding significant 

deficiency determinations with the 

primacy agency, either the State or EPA, 

that conducts the sanitary survey. States 

or EPA may withdraw or amend their 

significant deficiency determinations as 

appropriate. The IESWTR did not 

establish a separate appeal process for 

sanitary surveys conducted by States, 

and EPA has not established such a 

process for sanitary surveys conducted 

by EPA under today’s rule. 

M. Variances and Exemptions 

SDWA section 1415 allows States to 

grant variances from national primary 

drinking water regulations under certain 

conditions; section 1416 establishes the 

conditions under which States may 

grant exemptions to MCL or treatment 

technique requirements. These 

conditions and EPA’s view on their 

applicability to the LT2ESWTR are 

summarized as follows: 

1. Variances 

Section 1415 specifies two provisions 

under which general variances to 

treatment technique requirements may 

be granted: 

(1) A State that has primacy may grant a 

variance to a PWS from any requirement to 

use a specified treatment technique for a 

contaminant if the PWS demonstrates to the 

satisfaction of the State that the treatment 

technique is not necessary to protect public 

health because of the nature of the PWS’s raw 

water source. EPA may prescribe monitoring 

and other requirements as conditions of the 

variance (section 1415(a)(1)(B)). 

(2) EPA may grant a variance from any 

treatment technique requirement upon a 

showing by any person that an alternative 

treatment technique not included in such 

requirement is at least as efficient in lowering 

the level of the contaminant (section 

1415(a)(3)). 

EPA does not believe that the first 

variance provision is applicable to 

filtered PWSs under today’s rule. 

Filtered PWSs are required to 

implement additional treatment under 

the LT2ESWTR only when source water 

monitoring demonstrates higher levels 

of Cryptosporidium contamination. 

Thus, this treatment technique 

requirement accounts for the nature of 

the PWS’s raw water source. Unfiltered 

PWS treatment requirements also 

account for the nature of a PWS’s raw 

water source with respect to whether 2- 

or 3-log Cryptosporidium inactivation is 

required. 

In theory, the first variance provision 

could be applied to the requirement that 

all unfiltered PWSs provide at least 2- 


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log Cryptosporidium inactivation. If an 

unfiltered PWS could show a raw water 

Cryptosporidium level 3-log lower than 

the Bin 1 cutoff for filtered PWSs (i.e., 

below 0.075 oocysts/1,000 L), this could 

demonstrate that no treatment for 

Cryptosporidium is necessary. The 

unfiltered PWS would already be 

achieving public health protection 

against Cryptosporidium equivalent to 

filtered PWSs due to the nature of the 

raw water source. 

In practice, EPA has not identified an 

approach that is economically or 

technologically feasible for a PWS to 

demonstrate such a low level of 

Cryptosporidium to support granting a 

variance. This is due to the extremely 

large volume and number of samples 

that would be necessary to make such 

a demonstration with confidence. 

However, unfiltered PWSs may choose 

to pursue the development and 

implementation of monitoring programs 

to apply for a variance from 

Cryptosporidium inactivation 

requirements based on the nature of the 

raw water source. A sufficient 

monitoring program may be feasible in 

site-specific circumstances or with the 

use of innovative approaches. 

The second provision for granting a 

variance is not applicable to the 

LT2ESWTR because the rule provides 

broad flexibility in how PWSs achieve 

the required level of Cryptosporidium 

reduction through the microbial 

toolbox. Moreover, the microbial 

toolbox contains an option for 

Demonstration of Performance, under 

which States can award treatment credit 

based on the demonstrated efficiency of 

a treatment process in reducing 

Cryptosporidium levels. Thus, there is 

no need for this type of variance under 

the LT2ESWTR. 

SDWA section 1415(e) describes small 

PWS variances, but these cannot be 

granted for a treatment technique for a 

microbial contaminant. Hence, small 

PWS variances are not allowed for the 

LT2ESWTR. 

2. Exemptions 

Under SDWA section 1416(a), a State 

may exempt any PWS from a treatment 

technique requirement upon a finding 

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 PWS was in operation on 

the effective date of the treatment 

technique requirement, or for a PWS 

that was not in operation by that date, 

no reasonable alternative source of 

drinking water is available to the new 

PWS; (3) the exemption will not result 

in an unreasonable risk to health; and 

(4) management or restructuring 

changes (or both) cannot reasonably 

result in compliance with the Act or 

improve the quality of drinking water. 

EPA believes that granting an 

exemption to the Cryptosporidium 

treatment requirements of the 

LT2ESWTR would result in an 

unreasonable risk to health. As 

described in section III.C, 

Cryptosporidium causes acute health 

effects, which may be severe in sensitive 

subpopulations and include risk of 

mortality. Moreover, the additional 

Cryptosporidium treatment 

requirements of the LT2ESWTR are 

targeted to PWSs with the highest 

degree of risk. Due to these factors, EPA 

does not support the granting 

exemptions from the LT2ESWTR. 

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 LT2ESWTR, 

States must adopt revisions to the 

following sections: 

§ 141.2—Definitions 

Subpart Q—Public Notification 

New Subpart W—Additional treatment 

technique requirements for 

Cryptosporidium 

§ 142.14—Records kept by States 

§ 142.15—Reports by States 

§ 142.16—Special primacy requirements 

1. Special State primacy requirements 

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 perform the 

following: 

• Approve an alternative to the E. coli 

levels that trigger Cryptosporidium 

monitoring by filtered systems serving 

fewer than 10,000 people (see section 

IV.A.1); 

• Approve watershed control 

programs for the 0.5 log watershed 

control program credit in the microbial 

toolbox (see section IV.D.2); 

• Assess significant changes in the 

watershed and source water as part of 

the sanitary survey process and 

determine appropriate follow-up action 

(see section IV.A); and 

• Approve protocols for treatment 

credit under the Demonstration of 

Performance toolbox option (see section 

IV.D.9), for site specific chlorine dioxide 

and ozone CT tables (see section 

IV.D.14), and for alternative UV reactor 

validation testing (see section IV.D.15). 

A State program can be more, but not 

less, stringent than Federal regulations. 

As such, some of the elements listed 

here may not be applicable to a specific 

State program. 

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: 

• Results of source water E. coli and 

Cryptosporidium monitoring for not less 

than 1 year; 

• Cryptosporidium treatment bin 

classification for each filtered PWS after 

the initial and after the second round of 

source water monitoring. Also, any 

change in treatment requirements for 

filtered systems due to watershed 

assessment during sanitary surveys; 

• Determination of whether each 

unfiltered PWS has a mean source water 

Cryptosporidium level above 0.01 

oocysts/L after the initial and after the 

second round of source water 

monitoring; 

• The treatment processes or control 

measures that each PWS employs to 

meet Cryptosporidium treatment 

requirements under the LT2ESWTR, 

including measures that systems may 

use for only part of the year; and 

• A list of PWSs required to cover or 

treat the effluent of an uncovered 

finished water storage facilities. 

3. State Reporting Requirements 

Today’s rule requires States to report 

the following information: 

• The Cryptosporidium treatment bin 

classification for each filtered PWS after 

the initial and after the second round of 

source water monitoring. Also, any 

change in treatment requirements for 

filtered systems due to watershed 

assessment during sanitary surveys; and 

• The determination of whether each 

unfiltered PWS has a mean source water 

Cryptosporidium level above 0.01 

oocysts/L after the initial and after the 

second round of source water 

monitoring. 

4. Interim Primacy 

States that have primacy (including 

interim 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 


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for future NPDWRs must obtain primacy 

for today’s rule. As described in Section 

IV.A, EPA expects to work with States 

to oversee the initial source water 

monitoring that begins six months 

following rule promulgation. 

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. EPA 

currently requires in 40 CFR 142.15 that 

States report to EPA information such as 

violations, variance and exemption 

status, and enforcement actions, and 

today’s rule adds additional reporting 

requirements related to monitoring and 

treatment 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 

1998c). 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 

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. 

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. One 

commenter expressed concern that a 

State that adopted this rule by reference 

would lose the flexibility intended in 

the proposal. In response, EPA 

recognizes that some States may be 

limited by their statutes in applying the 

flexibility allowed under today’s rule. 

However, EPA believes that providing 

flexibility for States to approve sitespecific approaches that achieve the 

public health goals of the LT2ESWTR is 

appropriate and will benefit some States 

and PWSs. 

A few commenters were concerned 

that the special primacy requirement to 

assess changes in watersheds as part of 

the sanitary survey process would be 

difficult to meet due to a lack of 

resources or large watersheds that 

overlap State boundaries. In response, 

EPA notes that States are required to 

evaluate PWS sources under the existing 

sanitary survey requirements (40 CFR 

142.16(b)(3)). If a State determines 

during a sanitary survey that significant 

changes have occurred in the watershed 

that could lead to increased 

contamination of the source by 

Cryptosporidium, today’s rule gives the 

State the authority to require the PWS 

to take actions to mitigate or treat the 

contamination. Because the treatment 

requirements in today’s rule depend on 

the degree of source water 

contamination, EPA believes that this 

assessment of changes in a PWS’s 

source water following initial bin 

classification is necessary. 

EPA also received comments on State 

approval processes for laboratories 

analyzing for Cryptosporidium to meet 

LT2ESWTR requirements. Most 

commenters stated that EPA should 

maintain a national certification 

program for laboratories approved for 

Cryptosporidium analysis for 

LT2ESTWR compliance. Commenters 

indicated that requiring States to 

approve laboratories for 

Cryptosporidium analysis placed too 

great a demand on State resources. 

Today’s rule does not include a State 

primacy requirement for laboratory 

certification for Cryptosporidium 

analysis. 

Some commenters were concerned 

with the data tracking and review 

burden on States from the reporting 

requirements for the individual toolbox 

components. EPA agrees with 

commenters that, in some cases, 

allowing PWSs to report summaries or 

to self-certify that the PWS met the 

performance requirements for microbial 

toolbox treatment credit may be 

appropriate. Today’s rule allow States to 

modify the level of reporting required 

for toolbox components and 

specifically, permit PWSs to self-certify 

to the State that a toolbox component 

has met its performance requirements. 

VI. Economic Analysis 

This section summarizes the 

economic analysis (EA) for the final 

LT2ESWTR. The EA is an assessment of 

the benefits, both health and nonhealthrelated, and costs to the regulated 

community of the final regulation, along 

with those of regulatory alternatives that 

the Agency considered. EPA developed 

the EA to meet the requirement of 

SDWA section 1412(b)(3)(C) for a Health 

Risk Reduction and Cost Analysis 

(HRRCA), as well as the requirements of 

Executive Order 12866, Regulatory 

Planning and Review, under which EPA 

must estimate the costs and benefits of 

the LT2ESWTR. The full EA is 

presented in Economic Analysis for the 

Long Term 2 Enhanced Surface Water 

Treatment Rule (USEPA 2005a), which 

includes additional details and 

discussion on the topics presented 

throughout this section of the preamble. 

The LT2ESWTR is the second in a 

staged set of rules that address public 

health risks from microbial 

contamination of surface and GWUDI 

drinking water supplies and, more 

specifically, prevent Cryptosporidium 


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from reaching consumers. As described 

in section III, EPA promulgated the 

IESWTR and LT1ESWTR to provide a 

baseline of protection against 

Cryptosporidium in large and small 

PWSs, respectively. Today’s final rule 

will achieve further reductions in 

Cryptosporidium exposure for PWSs 

with the highest vulnerability. This EA 

considers only the incremental 

reduction in exposure beyond the two 

previously promulgated rules (IESWTR 

and LT1ESWTR) from the alternatives 

evaluated for the LT2ESWTR. 

A. What Regulatory Alternatives Did the 

Agency Consider? 

Regulatory alternatives considered by 

the Agency for the LT2ESWTR were 

developed through the deliberations of 

the Stage 2 M–DBP Federal Advisory 

Committee (described in section III). 

The Advisory Committee considered 

several general approaches for reducing 

the risk from Cryptosporidium in 

drinking water. These approaches 

included both additional treatment 

requirements for all PWSs and risktargeted treatment requirements for 

PWSs with the highest vulnerability to 

Cryptosporidium following 

implementation of the IESWTR and 

LT1ESWTR. In addition, the Advisory 

Committee considered related issues 

such as alternative monitoring 

strategies. 

After considering these general 

approaches, the Advisory Committee 

focused on four regulatory alternatives 

for filtered PWSs (see Table VI.A–1). 

With the exception of Alternative 1, 

which requires all PWSs to provide 

additional treatment for 

Cryptosporidium, these alternatives 

incorporate a risk-targeting approach in 

which PWSs are classified in different 

treatment bins based on the results of 

source water monitoring. Additional 

Cryptosporidium treatment 

requirements are directly linked to the 

treatment bin classification. 

Accordingly, these rule alternatives are 

differentiated by two criteria: (1) The 

Cryptosporidium concentrations that 

define the bin boundaries and (2) the 

degree of treatment required for each 

bin. 

The Advisory Committee reached 

consensus regarding additional 

treatment requirements for unfiltered 

PWSs without formally identifying 

regulatory alternatives other than 

requiring no treatment for 

Cryptosporidium (i.e., no new 

regulation). 

TABLE VI.A–1.—SUMMARY OF REGULATORY ALTERNATIVES FOR FILTERED PWSS

Mean source water 

Cryptosporidium monitoring result (oocysts/L) 

Additional treatment 

requirements 1

Alternative A1 

2.0-log inactivation required for all PWSs 

Alternative A2 

< 0.03 .......................... No additional treatment. 

≥ 0.03 and < 0.1 ......... 0.5-log. 

≥ 0.1 and < 1.0 ........... 1.5-log. 

≥ 1.0 ............................ 2.5-log. 

Alternative A3—Today’s Final Rule 

< 0.075 ........................ No additional treatment. 

≥ 0.075 and < 1.0 ....... 1-log. 

≥ 1.0 and < 3.0 ........... 2-log. 

≥ 3.0 ............................ 2.5-log. 

Alternative A4 

< 0.1 ............................ No additional treatment. 

≥ 0.1 and < 1.0 ........... 0.5-log. 

≥1.0 ............................. 1.0-log. 

1 Note: ‘‘Additional treatment requirements’’

are in addition to levels already required under 

existing rules (e.g., the IESWTR and 

LT1ESWTR) for PWSs using conventional 

treatment or equivalent. 

B. What Analyses Support Today’s Final 

Rule? 

EPA has quantified benefits and costs 

for each of the filtered PWS regulatory 

alternatives in Table VI.A–1 and for 

unfiltered PWS requirements. 

Quantified benefits stem from estimated 

reductions in the incidence of 

cryptosporidiosis resulting from the 

regulation. To make these estimates, the 

Agency employed Monte Carlo 

modeling to account for uncertainty and 

variability in key parameters like 

Cryptosporidium occurrence, 

infectivity, and treatment efficiency. 

Costs result largely from the installation 

of additional treatment, with lesser costs 

due to monitoring and other 

implementation activities. 

Cryptosporidium occurrence 

significantly influences the estimated 

benefits and costs of regulatory 

alternatives. As discussed in section 

III.E, EPA analyzed data collected under 

the ICR, the ICR Supplemental Surveys 

of medium PWSs (ICRSSM), and the ICR 

Supplemental Surveys of large PWSs 

(ICRSSL) to estimate the national 

occurrence distribution of 

Cryptosporidium in surface water. EPA 

evaluated these distributions 

independently when assessing benefits 

and costs for different regulatory 

alternatives. 

Another parameter that significantly 

influences estimated benefits is 

Cryptosporidium infectivity (i.e., the 

likelihood of infection after exposure to 

a given dose of Cryptosporidium). As 

discussed in section III.E, EPA 

considered results from human 

volunteer feeding studies and applied 

six different model forms to estimate 

dose-response relationships. 

To address uncertainty in these 

estimates, benefits are presented for 

three different dose response models: A 

‘‘high’’ estimate based on the model that 

showed the highest mean baseline risk, 

a ‘‘medium’’ estimate based on the 

model and data used at proposal, which 

is in the middle of the range of estimates 

produced by the six models, and a 

‘‘low’’ estimate, based on the model that 

showed the lowest mean baseline risk. 

These estimates are not upper and lower 

bounds. For each model, a distribution 

of effects is estimated, and the ‘‘high’’

and ‘‘low’’ estimates show only the 

means of these distributions for two 

different model choices. 

Both benefits and costs are 

determined as annualized present 

values, which allows comparison of cost 

and benefit streams that are variable 

over time. The time frame used for both 

benefit and cost comparisons is 25 

years. The Agency uses social discount 

rates of both 3 percent and 7 percent to 

calculate present values from the stream 

of benefits and costs and also to 

annualize the present value estimates 

over 25 years (see EPA’s Guidelines for 

Preparing Economic Analyses (USEPA 

2000c) for a discussion of social 

discount rates). 

Results of these analyses are 

summarized in this section of the 

preamble. Detailed results and 

descriptions of the supporting analyzes 

are shown in the LT2ESWTR EA 

(USEPA 2005a). 

In evaluating the regulatory 

alternatives shown in Table VI.A–1, 

EPA and the Advisory Committee were 

concerned with the following questions: 

(1) Do the treatment requirements 

adequately control Cryptosporidium 

concentrations in finished water? (2) 

How many PWSs will be required to 

add treatment? and (3) What is the 

likelihood that PWSs will be 

misclassified in higher or lower 

treatment bins through monitoring? 

Consistent with the consensus 

recommendation of the Advisory 

Committee, EPA selected Alternative A3 

for today’s final rule. EPA has 

determined that this alternative will 

significantly reduce the incidence of 

cryptosporidiosis due to drinking water 


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in vulnerable PWSs and is feasible for 

PWSs to implement. 

Alternative A1 (across-the-board 2-log 

inactivation) was not selected because it 

would impose costs but provide few 

benefits to PWSs with relatively low 

Cryptosporidium risk. EPA was also 

concerned about the feasibility of 

requiring every surface water treatment 

plant to install additional treatment 

processes (e.g., UV) for 

Cryptosporidium. With Alternative A2, 

EPA was concerned with the feasibility 

of accurately classifying PWSs in 

treatment bins at a Cryptosporidium 

concentration of 0.03 oocysts/L. EPA 

does not believe that Alternative A4 

would reduce risks from 

Cryptosporidium in vulnerable PWSs to 

the extent feasible, as required under 

SDWA section 1412(b)(7)(A), because of 

the low levels of treatment required. 

C. What Are the Benefits of the 

LT2ESWTR? 

EPA has quantified and monetized 

health benefits for reductions in 

endemic cryptosporidiosis due to the 

LT2ESWTR. In addition, today’s rule is 

expected to provide additional health 

and nonhealth-related benefits that EPA 

was unable to quantify. Table VI.C–1 

summarizes these unquantified benefits. 

1. Nonquantified Benefits 

TABLE VI.C–1.—SUMMARY OF NONQUANTIFIED BENEFITS

Benefit type Potential effect on 

benefits Comments 

Reducing outbreak risks and response 

costs.

Increase ..................... Some human or equipment failures may occur even with the requirements of 

today’s rule; however, by adding barriers of protection for some PWSs, the 

rule will reduce the possibility of such failures leading to outbreaks. 

Reducing averting behavior (e.g., boiling tap water or purchasing bottled 

water).

Increase/No Change Consumers in PWSs that cease using uncovered finished water reservoirs 

(through covering or taking such reservoirs off-line) may have greater confidence in water quality. This may result in less averting behavior that reduces both out-of-pocket costs (e.g., purchase of bottled water) and opportunity costs (e.g., time to boil water). 

Improving aesthetic water quality ......... Increase ..................... Some technologies installed for this rule (e.g., ozone) are likely to reduce 

taste and odor problems. 

Reducing risk from co-occurring and 

emerging pathogens.

Increase ..................... Although focused on removal of Cryptosporidium from drinking water, PWSs 

that change treatment processes will also increase removal of pathogens 

that the rule does not specifically regulate. 

Increased source water monitoring ...... Increase ..................... The greater understanding of source water quality that results from monitoring 

may enhance the ability of plants to optimize treatment operations in ways 

other than those addressed in this rule. 

Reduced contamination due to covering or treating finished water storage facilities.Increase ..................... Contaminants introduced through uncovered finished water storage facilities 

will be reduced, which will produce positive public health benefits. 

Change in the levels of disinfection byproducts.Increase/Decrease .... PWSs that install ozone to comply with the LT2ESWTR may experience an increase in certain DBPs. PWSs that install UV or microfiltration may reduce 

the use of chlorine and experience a decrease in DBPs. 

Source: Chapter 5 of the LT2ESWTR Economic Analysis (USEPA 2005a). 

2. Quantified Benefits 

In quantifying benefits for the 

LT2ESWTR based on reductions in the 

risk of endemic cryptosporidiosis, EPA 

considered several categories of 

monetized benefits. First, EPA estimated 

the number of cases expected to result 

in premature mortality (primarily for 

members of sensitive subpopulations 

such as AIDS patients). The mortality 

estimate was developed using data from 

the Milwaukee cryptosporidiosis 

outbreak of 1993 (described in section 

III), with adjustments to account for the 

subsequent decrease in the mortality 

rate among people with AIDS and for 

the difference between the portion of 

people living with AIDS in 1993 in 

Milwaukee and the current and 

projected national levels. EPA estimated 

a mortality rate of 26.3 deaths per 

100,000 illnesses for those served by 

unfiltered PWSs and a mortality rate of 

16.7 deaths per 100,000 illnesses for 

those served by filtered PWSs. These 

different rates are associated with the 

incidence of AIDS in populations served 

by unfiltered and filtered PWSs. A 

complete discussion on how EPA 

derived these rates can be found in 

subchapter 5.2 of the LT2ESWTR EA 

(USEPA 2005a). 

Reductions in mortalities were 

monetized using EPA’s standard 

methodology for monetizing mortality 

risk reduction. This methodology is 

based on a distribution of value of 

statistical life (VSL) estimates from 26 

labor market and stated preference 

studies. The mean VSL is $7.4 million 

in 2005 with a 5th to 95th percentile 

range of $1.2 to $16.9 million. A more 

detailed discussion of these studies and 

the VSL estimate can be found in EPA’s 

Guidelines for Preparing Economic 

Analyses (USEPA 2000c). A real income 

growth factor was applied to these 

estimates of approximately 1.9 percent 

per year for the 20-year time span 

following implementation. Income 

elasticity for VSL was estimated as a 

triangular distribution that ranged from 

0.08 to 1.00, with a mode of 0.40. VSL 

values for the 20-year span are shown in 

the LT2ESWTR EA in Exhibit 5.24 

(USEPA 2005a). 

The substantial majority of cases are 

not expected to be fatal and the Agency 

separately estimated the value of nonfatal illnesses avoided that would result 

from the LT2ESWTR. For these, EPA 

first divided projected cases into three 

categories, mild, moderate, and severe, 

and then calculated a monetized value 

per case avoided for each severity level. 

These were then combined into a 

weighted average value per case based 

on the relative frequency of each 

severity level. According to a study 

conducted by Corso et al. (2003), the 

majority of illness fall into the mild 

category (88 percent). Approximately 11 

percent of illness fall into the moderate 

category, which is defined as those who 

seek medical treatment but are not 

hospitalized. The final 1 percent have 

severe symptoms that result in 

hospitalization. EPA estimated different 

medical expenses and time losses for 

each category. 

Benefits for non-fatal cases were 

calculated using a cost-of-illness (COI) 


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approach. Traditional COI valuations 

focus on medical costs and lost wages, 

and leave out significant categories of 

benefits, specifically the reduced utility 

from being sick (i.e., lost personal or 

non-work time, including activities such 

as child care, homemaking, community 

service, time spent with family, 

recreation, and pain and suffering), 

although some COI studies also include 

an estimate for unpaid labor (household 

production) valued at an estimated wage 

rate designed to reflect the market value 

of such labor (e.g., median wage for 

household domestic labor). Ideally, a 

comprehensive willingness to pay 

(WTP) estimate would be used that 

includes all categories of loss in a single 

number. However, a review of the 

literature indicated that the available 

studies were not suitable for valuing 

cryptosporidiosis; hence, estimates from 

this literature are inappropriate for use 

in this analysis. Instead, EPA presents 

two COI estimates: A traditional 

approach that only includes valuation 

for medical costs and lost work time 

(including some portion of unpaid 

household production); and an 

enhanced approach that also factors in 

valuations for lost unpaid work time for 

employed people, reduced utility (or 

sense of well-being) associated with 

decreased enjoyment of time spent in 

non-work activities, and lost 

productivity at work on days when paid 

workers are ill but go to work anyway. 

Table VI.C–2 shows the various 

categories of loss and how they were 

valued for each estimate for a ‘‘typical’’

case in 2003 (weighted average based on 

severity level). 

TABLE VI.C–2.—TRADITIONAL AND ENHANCED COI FOR CRYPTOSPORIDIOSIS, 2003$ 

[Weighted average cost per case] 

Loss category Traditional 

COI Enhanced COI 

Direct Medical Costs .................................................................................................................................................. $106.91 106.91 

Lost Paid Work Days ................................................................................................................................................. 120.13 120.13 

Lost Unpaid Work Days 1 ........................................................................................................................................... 24.32 48.64 

Lost Leisure Time 2 .................................................................................................................................................... not included 217.79 

Lost Caregiver Days 3 ................................................................................................................................................ 22.98 61.50 

Lost Leisure Productivity 4 .......................................................................................................................................... not included 162.98 

Lost Productivity at Work ........................................................................................................................................... not included 126.29 

Total .................................................................................................................................................................... 274.34 844.24 

1Assigned to 39.7% of the population not engaged in market work; assumes 40 hr. unpaid work week, valued at $6.23/hr in traditional COI 

and $12.46/hr in enhanced COI. Does not include lost unpaid work for employed people and may not include all unpaid work for people outside 

the paid labor force. 2 Includes child care and homemaking (to the extent not covered in lost unpaid work days above), time with family, and recreation for people 

within and outside the paid labor force, on days when subject is too sick to work. 3Values lost work or leisure time for people caring for the ill. Traditional approach does not include lost leisure time. Detail may not calculate to 

totals due to independent rounding; Source: Appendix L in LT2ESWTR EA (USEPA 2005a) 4Analogous to lost productivity at work. Includes reduced productivity in unpaid work and reduced enjoyment of recreation on days when subject is sick but engages in unpaid work or leisure activities anyway. 

The various loss categories were 

calculated as follows: Medical costs are 

a weighted average across the three 

illness severity levels of actual costs for 

doctor and emergency room visits, 

medication, and hospital stays. Lost 

paid work represents missed work time 

of paid employees, valued at the median 

pre-tax wage, plus benefits, of $20.82 

hour. The average number of lost work 

hours per illness day is 3.4 (this 

assumes that 60 percent of the 

population is in the paid labor force and 

the loss is averaged over 7 days). The 

weighted average number of lost work 

days per case is 1.7 days. Medical costs 

and lost work days reflect market 

transactions. Medical costs are always 

included in COI estimates and lost work 

days are usually included in COI 

estimates. 

In the traditional COI estimate, an 

equivalent amount of lost unpaid work 

time was assigned to the 40 percent of 

the population that are not in the paid 

labor force. This includes homemakers, 

students, children, retires, and 

unemployed persons. This estimate 

attempts to capture market-like work 

(e.g., homemaking, volunteer work) that 

is unpaid. EPA did not attempt to 

calculate what percent of cases falls in 

each of these five groups, or how many 

hours per week each group works, but 

rather assumed an across-the-board 40 

hour unpaid work week. For this reason, 

it likely overstates the value of unpaid, 

market-like work, but EPA does not 

have data on this. This time is valued 

at $6.23 per hour, which is one half the 

median post-tax wage (since work 

performed by these groups is not taxed). 

This is also approximately the median 

wage for paid household domestic labor. 

In the enhanced COI estimate, an 

estimate of lost unpaid work days for 

people outside the paid labor force was 

made by assigning the value of $12.46 

per hour to the same number of unpaid 

work hours valued in the traditional 

COI approach (i.e., 40 unpaid work 

hours per week). Lost unpaid work for 

employed people and any unpaid labor 

beyond 40 hours per week for those not 

in the labor market is shown as lost 

leisure time in Table VI.C–2 for the 

enhanced approach and is not included 

in the traditional approach. 

In the enhanced approach, all time 

other than paid and market-like work 

and sleep (8 hours per work day and 16 

hours per non-work day) is valued at the 

median after tax wage, or $12.46 per 

hour. This includes lost unpaid 

personal work (e.g., chores, errands, 

housework) and leisure time for people 

within and outside the paid labor force. 

The average number of unpaid work 

hours per illness day is 2.3 (40 hours 

per week averaged over 7 days × 40 

percent of the population). Implicit in 

this approach is that people would pay 

the same amount not to be sick during 

their leisure time as they require to give 

up their leisure time to work (i.e., the 

after tax wage). In reality, people might 

be willing to pay either more than this 

amount (if they were very sick and 

suffering a lot) or less than this amount 

(if they were not very sick and still got 

some enjoyment out of activities such as 

resting, reading, and watching TV), not 

to be sick. Multiplying 10.3 hours by 

$12.46 gives a value of about $128 for 

a day of ‘‘lost’’ unpaid personal work 

and leisure (i.e., lost utility of being 

sick). The weighted average number of 

lost leisure days per case is the same as 

the weighted average number of lost 

work days (1.7 days per case). 


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In addition, for days when an 

individual is well enough to work but 

is still experiencing symptoms, such as 

diarrhea, the enhanced estimate also 

includes a 30 percent loss of work and 

leisure productivity, based on a study of 

giardiasis illness (Harrington et al. 

1985), which is similar to 

cryptosporidiosis. Appendix P in the EA 

describes similar productivity losses for 

other illnesses such as influenza (35%–

73% productivity losses). In the 

traditional COI analysis, productivity 

losses are not included for either work 

or nonwork time. The weighted average 

number of reduced productivity days 

per case, for both work and leisure, is 

1.3 days. 

EPA believes that losses in 

productivity and lost leisure time are 

unquestionably present and that these 

categories have positive value; 

consequently, the traditional COI 

estimate understates the true value of 

these loss categories. EPA notes that 

these estimates should not be regarded 

as upper and lower bounds. In 

particular, the enhanced COI estimate 

may not fully incorporate the value of 

pain and suffering, as people may be 

willing to pay more than $228 (the sum 

of the valuation of lost work and leisure) 

to avoid a day of illness. The traditional 

COI estimate may not be a lower bound 

because it includes a valuation for a lost 

40 hour work week for all persons not 

in the labor force, including children 

and retirees. This may be an 

overstatement of lost productivity for 

these groups, which would depend on 

the impact of such things as missed 

school work or volunteer activities that 

may be affected by illness. 

As with the avoided mortality 

valuation, the real wages used in the 

COI estimates were increased by a real 

income growth factor that varies by 

year, but is the equivalent of about 1.9 

percent over the 20 year period. This 

approach of adjusting for real income 

growth was recommended by the SAB 

(USEPA 2000d) because the median real 

wage is expected to grow each year (by 

approximately 1.9 percent). 

Correspondingly, the real income 

growth factor of the COI estimates 

increases by the equivalent of 1.9 

percent per year (except for medical 

costs, which are not directly tied to 

wages). This approach gives a total COI 

valuation per case in 2010 of $306 

(undiscounted) for the traditional COI 

estimate and $985 (undiscounted) for 

the enhanced COI estimate; the 

valuation in 2029 is $381 

(undiscounted) for the traditional COI 

estimate and $1,316 (undiscounted) for 

the enhanced COI estimate. There is no 

difference in the methodology for 

calculating the COI over this 20 year 

period of implementation; the change in 

valuation is due to the underlying 

change in projected real wages. 

Table VI.C–3 summarizes the annual 

cases of cryptosporidiosis illness and 

associated deaths avoided due to the 

LT2ESWTR proposal. Today’s rule, on 

average, is expected to reduce 89,375 to 

1,459,126 illnesses and 20 to 314 deaths 

annually after full implementation 

(range based on the ICRSSL, ICRSSM, 

and ICR data sets and model choice for 

Cryptosporidium infectivity). 

Tables VI.C–4a and VI.C–4b show the 

monetized present value of the benefit 

for reductions in endemic 

cryptosporidiosis estimated to result 

from the LT2ESWTR for the enhanced 

and traditional COI values, respectively. 

Estimates are given for the ICR, ICRSSL, 

and ICRSSM occurrence data sets and 

for the three infectivity models. 

With the enhanced COI and a 3 

percent discount rate, the annual 

present value of the mean benefit 

estimate ranges from $177 million to 

$2.8 billion; at a 7 percent discount rate, 

the mean estimate ranges from $144 

million to $2.3 billion. With the 

traditional COI, the corresponding mean 

benefit estimate at a 3 percent discount 

rate ranges from $130 million to $2.0 

billion; for a 7 percent discount rate, the 

mean estimate ranges from $105 million 

to $1.7 billion. None of these values 

include the unquantified and 

nonmonetized benefits listed in Table 

VI.C–1. 

BILLING CODE 6560–50–P 


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BILLING CODE 6560–50–C 

a. Filtered PWSs. Benefits to the 

approximately 168 million people 

served by filtered surface water and 

GWUDI PWSs range from 34,000 to 

702,000 reduction in mean annual cases 

of endemic illness based on three 

infectivity models and ICRSSL, 

ICRSSM, and ICR data sets. In addition, 

premature mortality is expected to be 

reduced by an average of 6 to 116 deaths 

annually. 

b. Unfiltered PWSs. The 10 million 

people served by unfiltered surface 

water or GWUDI PWSs will see a 

significant reduction in 

cryptosporidiosis as a result of the 

LT2ESWTR. In this population, the rule 

is expected to reduce approximately 

55,000 to 758,000 cases of illness and 14 

to 197 premature deaths annually. 

For unfiltered PWSs, only the ICR 

data set is used to directly calculate 

illness reduction because it is the only 

data set that includes sufficient 

information on unfiltered PWSs. Illness 

reduction in unfiltered PWSs was 

estimated for the ICRSSL and ICRSSM 


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data sets by multiplying the ICR 

unfiltered PWS result by the ratio, for 

the quantity estimated, between filtered 

PWS results from the supplemental 

survey data set (SSM or SSL) and 

filtered PWS results from the ICR. 

3. Timing of Benefits Accrual (latency) 

In previous rulemakings, some 

commenters have argued that the 

Agency should consider an assumed 

time lag or latency period in its benefits 

calculations. The Agency has not 

conducted a latency analysis for this 

rule because cryptosporidiosis is an 

acute illness; therefore, very little time 

elapses between exposure, illness, and 

mortality. However, EPA does account 

for benefits and costs that occur in 

future years by converting these to 

present value estimates. 

D. What Are the Costs of the 

LT2ESWTR? 

In order to estimate the costs of 

today’s rule, the Agency considered 

impacts on PWSs and on States 

(including territories and EPA 

implementation in non-primacy States). 

Summary information on these costs 

follows, with more detailed information 

in chapter 6 of the LT2ESWTR EA 

(USEPA 2005a). A detailed discussion 

of the requirements of today’s rule is 

located in section IV of this preamble. 

1. Total Annualized Present Value Costs 

Tables VI.D–1 summarizes the 

annualized present value cost estimates 

for the LT2ESWTR at 3 percent and 7 

percent discount rates. The mean 

annualized present value costs of the 

LT2ESWTR are estimated to range from 

approximately $93 to $133 million 

using a 3 percent discount rate and $107 

to $150 million using a 7 percent 

discount rate. This range in mean cost 

estimates is associated with the different 

Cryptosporidium occurrence data sets. 

In addition to mean estimates of costs, 

the Agency calculated 90 percent 

confidence bounds by considering the 

uncertainty in Cryptosporidium 

occurrence estimates and the 

uncertainty around the mean unit 

technology costs (USEPA 2005a). 

PWSs will incur approximately 99 

percent of the rule’s total annualized 

present value costs. States incur the 

remaining rule costs. Table VI.D–2 

shows the undiscounted initial capital 

and one-time costs broken out by rule 

component. A comparison of 

annualized present value costs among 

the rule alternatives considered by the 

Agency is located in section VI.F of this 

preamble. 

BILLING CODE 6560–50–P 


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2. PWS Costs 

Table VI.D–3 shows the number of 

filtered and unfiltered PWSs that will 

incur costs by rule provision. All PWSs 

that treat surface water or GWUDI (i.e., 

nonpurchased PWSs) will incur onetime costs that include time for staff 

training on rule requirements. PWSs 

will incur monitoring costs to assess 

source water Cryptosporidium levels, 

though monitoring requirements vary by 

PWS size (large vs. small) and PWS type 

(filtered vs. unfiltered). Some PWSs will 

incur costs for additional 

Cryptosporidium treatment, where 

required, and for covering or treating 

uncovered finished water reservoirs. 

a. Source water monitoring costs. 

Source water monitoring costs are 

structured on a per-plant basis. There 

are three types of monitoring that plants 

may be required to conduct—turbidity, 

E. coli, and Cryptosporidium. Source 

water turbidity is a common water 

quality parameter used for plant 

operational control. Also, to meet 

SWTR, LT1ESWTR, and IESWTR 

requirements, most PWSs have turbidity 

analytical equipment in-house and 

operators are experienced with turbidity 

measurement. Thus, EPA assumes that 

the incremental turbidity monitoring 

burden associated with the LT2ESWTR 

is negligible. 

Filtered plants in small PWSs initially 

will be required to conduct 1 year of 

biweekly E. coli source water 

monitoring. These plants will be 

required to monitor for 

Cryptosporidium if E. coli levels exceed 

10 E. coli/100 mL for lakes and reservoir 

sources or 50 E. coli/100 mL for flowing 

stream sources. EPA estimated the 

percent of small plants that would be 

triggered into Cryptosporidium 

monitoring as being equal to the percent 

of large plants that would fall into any 

bin requiring additional treatment. 

Estimates of laboratory fees, shipping 

costs, labor hours for sample collection, 

and hours for reporting results were 

used to predict PWS costs for initial 

source water monitoring under the 

LT2ESWTR. Table VI.D–4 summarizes 

the present value of monitoring costs for 

initial bin classification. Total present 

value monitoring costs for initial bin 

classification range from $45 million to 

$59 million depending on the 

occurrence data set and discount rate. 

Appendix D of the LT2ESWTR EA 

provides a full explanation of how these 

costs were developed (USEPA 2005a). 

b. Filtered PWSs treatment costs. The 

Agency calculated treatment costs by 

estimating the number of plants that 

will add treatment technologies and 

coupling these estimates with unit costs 

($/plant) of the selected technologies. 

Table VI.D–5 shows the number of 

plants estimated to select different 

treatment technologies; Table VI.D–6 

summarizes the present value treatment 

costs and annualized present value costs 

for both filtered and unfiltered PWSs. 


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To estimate the number of filtered 

plants that would select a particular 

treatment technology, EPA followed a 

two step process. First, the number of 

plants that will be assigned to treatment 

bins requiring additional treatment was 

estimated. Second, the treatment 

technologies that plants will choose to 

meet these requirements was estimated 

using a ‘‘least-cost decision tree.’’ In this 

estimate, EPA assumed that PWSs will 

select the least expensive technology or 

combination of technologies to meet the 

log removal requirements of a given 

treatment bin. Technology selections 

were constrained by maximum use 

percentages, which recognize that some 

plants will not be able to implement 

certain technologies because of sitespecific conditions. In addition, certain 

potentially lower cost components of 

the microbial toolbox, such as changes 

to the plant intake, were not included 

because EPA lacked data to estimate the 

number of plants that could select it. 

These limitations on technology use 

may result in an overestimate of costs. 

An in-depth discussion of the 

technology selection methodology and 

unit cost estimates can be found in 

Appendices E and F of the LT2ESWTR 

EA (USEPA 2005a). 

c. Unfiltered PWSs treatment costs. 

The LT2ESWTR requires all unfiltered 

PWSs to achieve 2-log of inactivation if 

their mean source water 

Cryptosporidium concentration is less 

than or equal to 0.01 oocysts/L and 3- 

log of inactivation if it is greater than 

0.01 oocysts/L. For most PWSs, UV 

appears to be the least expensive 

technology that can achieve these levels 

of Cryptosporidium inactivation, and 

EPA expects UV to be widely used by 

unfiltered PWSs to meet today’s rule 

requirements. However, as with filtered 

PWSs, EPA estimated that a small 

percentage of plants would elect to 

install a technology more expensive 

than UV due to the configuration of 


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existing equipment or other factors. 

Ozone is the next least expensive 

technology that will meet the 

inactivation requirements for some 

PWSs and EPA estimated that it will be 

used by plants that do not use UV. 

All unfiltered PWSs must meet 

requirements of the LT2ESWTR; 

therefore, 100 percent of unfiltered 

PWSs are estimated to add technology. 

This assumes that no unfiltered PWSs 

currently use these additional treatment 

technologies. For this cost analysis, EPA 

assumed that all very small unfiltered 

PWSs will use UV; for all other 

unfiltered PWS sizes, EPA estimated 

that 90 percent will install UV and 10 

percent will add ozone. Treatment costs 

for unfiltered PWSs are included in 

Table VI.D–6. 

d. Uncovered finished water storage 

facilities. As part of the LT2ESWTR, 

PWSs with uncovered finished water 

storage facilities must either cover the 

storage facility or treat the discharge to 

achieve inactivation and/or removal of 

at least 2-log Cryptosporidium, 3-log 

Giardia lamblia, and 4-log viruses. To 

develop national cost estimates for 

PWSs to comply with these provisions, 

unit costs for each compliance 

alternative and the percentage of PWSs 

selecting each alternative were 

estimated for the inventory of 

uncovered finished water storage 

facilities. From a recent survey of EPA 

Regions, EPA estimates that there are 

currently 81 uncovered finished water 

storage facilities for which PWSs must 

take steps to comply with the 

LT2ESWTR. A full description of the 

unit costs and other assumptions used 

in this analysis is presented in Chapter 

6 and Appendix I of the LT2ESWTR EA 

(USEPA 2005a). 

To comply with the treatment 

requirements, EPA determined that the 

least-cost treatment option is a 

combination of chlorine and UV. For 

PWSs with uncovered storage facility 

capacities of 5 million gallons (MG) or 

less, covering the storage facilities is the 

least expensive alternative. Although 

disinfection is the least expensive 

alternative for the remaining PWSs, the 

ability of a PWS to use booster 

chlorination depends on their current 

residual disinfectant type. Somewhat 

less than half of all surface water PWSs 

are predicted to use chloramination 

following implementation of the Stage 2 

DBPR. Adding chlorine to water that has 

been treated with chloramines is not a 

feasible alternative; therefore, the 

fraction of PWSs projected to add UV 

and booster chlorination to the effluent 

from the uncovered storage facility was 

estimated at 50 percent, with the 

remaining 50 percent projected to add 

covers. 

Table VI.D–7 summarizes total 

annualized present value costs for the 

uncovered finished water storage 

facility requirements using both 3 and 7 

percent discount rates. EPA estimates 

the total annualized present value cost 

for covering or treating the water from 

uncovered finished water storage 

facilities to be approximately $10 

million at a 3 percent discount rate and 

$13 million at a 7 percent discount rate. 


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e. Future monitoring costs. Six years 

after initial bin classification, filtered 

and unfiltered PWSs must conduct a 

second round of monitoring to assess 

whether source water Cryptosporidium 

levels have changed significantly. EPA 

will evaluate new analytical methods 

and surrogate indicators of microbial 

water quality in the interim. While the 

costs of monitoring are likely to change 

in the 9 years following rule 

promulgation, it is difficult to predict 

how they will change. In the absence of 

any other information, EPA assumed 

that the laboratory costs will be the 

same as for the initial monitoring. 

All PWSs that conducted initial 

monitoring were assumed to conduct 

the second round of monitoring, except 

for those PWSs that installed treatment 

that achieves a total of 5.5-log or greater 

treatment for Cryptosporidium as a 

result of the rule. These PWSs are 

exempt from monitoring under the 

LT2ESWTR. EPA estimates that the cost 

of the second round of source water 

monitoring will range from $21 million 

to $36 million, depending on the 

occurrence data set and discount rate 

used in the estimate. Appendix D of the 

EA provides further details (USEPA 

2005a). 

f. Sensitivity analysis-influent 

bromide levels on technology selection 

for filtered plants. One concern with the 

ICR data set is that it may not reflect 

influent bromide levels in some PWSs 

during droughts. High influent bromide 

levels (the precursor for bromate 

formation) limits ozone use because 

some PWSs would not be able to meet 

the MCL for bromate. EPA conducted a 

sensitivity analysis to estimate the 

impact that higher influent bromide 

levels would have on technology 

decisions. The sensitivity analysis 

assumed influent bromide 

concentrations of 50 parts per billion 

(ppb) above the ICR concentrations. 

Results of the analysis indicate that this 

higher bromide level has a minimal 

impact on costs. 

3. State/Primacy Agency Costs 

EPA estimates that States (including 

primacy agencies) will incur an 

annualized present value cost of $1.1 to 

1.2 million using a 3 percent discount 

rate and $1.4 million at 7 percent. State 

implementation activities include 

regulation adoption, program 

implementation, training State staff, 

training PWS staff, providing technical 

assistance to PWSs, and updating 

management systems. To estimate 

implementation costs to States, the 

number of full-time employees (FTEs) 

per activity is multiplied by the number 

of labor hours per FTE, the cost per 

labor hour, and the number of States 

and Territories. 

In addition to implementation costs, 

States will also incur costs associated 

with managing monitoring data. 

Because EPA will directly manage 

reporting, approval, and analysis of 

results from the initial round of 

monitoring by large PWSs (serving at 

least 10,000 people), States are not 

predicted to incur costs for these 

activities. States will, however, incur 

costs associated with small PWS 

monitoring. This is a result of the later 

start of small PWS monitoring, which 

will mean that some States will assume 

primacy for small PWS monitoring. In 

addition, States will review the second 

round of monitoring results. States will 

also incur costs for reviewing 

technology compliance data and 

consulting with PWSs regarding 

disinfection benchmarking (for PWSs 

that change their disinfection 

procedures to comply with today’s rule). 

Appendix D of the LT2ESWTR EA 

provides more information about the 

State cost analysis (USEPA 2005a). 

4. Non-Quantified Costs 

EPA has quantified all the major costs 

for this rule and has provided 

uncertainty analyses to bound the over 

or underestimates in the costs. There are 

some costs that EPA has not quantified, 

however, because of lack of data. For 

example, some PWSs may merge with 

neighboring PWSs to comply with this 

rule. Such changes have both costs 

(legal fees and connecting 

infrastructure) and benefits (economies 

of scale). Likewise, PWSs would incur 

costs for procuring a new source of 

water that may result in lower overall 

treatment costs. 

In addition, the Agency was unable to 

predict the usage or estimate the costs 

of several options in the microbial 

toolbox. These options include intake 

management and demonstrations of 

performance. They have not been 

included in the quantified analysis 

because data are not available to 

estimate the number of PWSs that may 

use these toolbox options to comply 

with the LT2ESWTR. Not including 

these generally lower-cost options may 

result in overestimation of costs. 

E. What Are the Household Costs of the 

LT2ESWTR? 

Another way to assess a rule’s impact 

is to consider how it may impact 

residential water bills. This analysis 

considers the potential increase in a 

household’s water bill if a CWS passed 

the entire cost increase resulting from 

this rule on to its customers. This serves 

as a tool to gauge potential impacts and 

should not be construed as precise 

estimates of potential changes to 

individual water bills. 

Included in this analysis are all PWS 

costs, including rule implementation, 

initial and future monitoring for bin 

classification, additional 

Cryptosporidium treatment, and treating 


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or covering uncovered finished water 

storage facilities. Costs for 

Cryptosporidium monitoring by small 

PWSs, additional Cryptosporidium 

treatment, and uncovered finished water 

storage facilities are assigned only to the 

subset of PWSs expected to incur them. 

Although implementation and 

monitoring represent relatively small, 

one-time costs, they have been included 

in the analysis to provide a complete 

distribution of the potential household 

cost. A detailed description of the 

derivation of household costs is in 

Chapter 6 and Appendix J of the 

LT2ESTWR EA (USEPA 2005a). 

For PWSs that purchase treated water 

(i.e., purchased PWSs) from larger 

nonpurchased PWSs, the households 

costs are calculated based on the unit 

treatment costs of the larger PWS but 

included in the distribution for the size 

category of the purchased PWS. 

Households costs for these purchased 

PWSs are based on the household usage 

rates appropriate for the retail PWS and 

not the PWS selling (wholesaling) the 

water. This approach for purchased 

PWSs reflects the fact that although they 

will not face increased costs from 

adding their own treatment, whatever 

costs the wholesale PWS incurs will 

likely be passed on as higher water 

costs. 

Table VI.E–1 shows the results of the 

household cost analysis. In addition to 

mean and median estimates, EPA 

calculated the 90th and the 95th 

percentiles. EPA estimates that all 

households served by surface and 

GWUDI sources will face some increase 

in household costs due to 

implementation of the LT2ESWTR. Of 

all the households subject to the rule, 

from 22 to 41 percent are projected to 

incur costs for adding treatment, 

depending on the Cryptosporidium 

occurrence data set used. 

Approximately 92 percent of the 

households potentially subject to the 

rule are served by PWSs serving at least 

10,000 people and 99.8 percent are 

served by PWSs serving at least 500 

people; these PWSs experience the 

lowest increases in costs due to 

significant economies of scale. Over 95 

percent of all households are estimated 

to face an annual cost increase of less 

than $12. Households served by small 

PWSs that install advanced technologies 

will face the greatest increases in annual 

costs. EPA expects that the model’s 

projections for these PWSs are, in some 

cases, overstated. Some PWSs are likely 

to find alternative treatment techniques 

such as other toolbox options not 

included in this analysis, or sources of 

water (ground water, purchased water, 

or consolidating with another PWS) that 

would be less costly than installing 

more expensive treatment technologies. 


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F. What Are the Incremental Costs and 

Benefits of the LT2ESWTR? 

Incremental costs and benefits are 

those that are incurred or realized in 

reducing Cryptosporidium exposures 

from one regulatory alternative to the 

next. Estimates of incremental costs and 

benefits are useful in considering the 

economic efficiency of different 

regulatory alternatives evaluated by 

EPA. Generally, the goal of an 

incremental analysis is to identify the 

most efficient regulatory alternative. 

However, this analysis is incomplete 

because some benefits from this rule are 

unquantified and not monetized. 

Incremental analyses should consider 

both quantified and unquantified 

(where possible) benefits and costs. 

Usually an incremental analysis 

implies increasing levels of stringency 

along a single parameter, with each 

alternative providing all the protection 

of the previous alternative, plus 

additional protection. However, the 

regulatory alternatives evaluated for the 

LT2ESWTR vary by multiple parameters 

(e.g., treatment bin boundaries, 

treatment requirements). The 

comparison between any two 

alternatives is, therefore, between two 

separate sets of benefits, in the sense 

that they may be distributed to 

somewhat different population groups. 

The regulatory alternatives, however, 

do achieve increasing levels of benefits 

at increasing levels of costs. As a result, 

displaying incremental net benefits from 

the baseline and alternative to 

alternative is possible. Tables VI.F–1a 

and VI.F–1b show incremental costs, 

benefits, and net benefits for the four 

regulatory alternatives, A1–A4, shown 

in Table VI.A–1, using the enhanced 

and traditional COI, respectively. All 

values are annualized present values 

expressed in Year 2003 dollars. The 

displayed values are the mean estimates 

for each occurrence distribution and 

infectivity model. 

With the enhanced COI, incremental 

costs are generally closest to 

incremental benefits for A2, a more 

stringent alternative than A3, which is 

today’s final rule. For the traditional 

COI, incremental costs most closely 

equal incremental benefits for A3 under 

the majority of conditions evaluated. 

G. Are There Benefits From the 

Reduction of Co-Occurring 

Contaminants? 

While the quantified and monetized 

benefits for the LT2ESWTR includes 

only reductions in illness and mortality 

attributable to Cryptosporidium, today’s 

rule will reduce exposure to and disease 

from other microbial pathogens and, in 

some cases, chemical contaminants. 


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All of the options in the microbial 

toolbox that PWSs will implement to 

comply with today’s rule will also 

reduce levels of other microbial 

pathogens. For example, watershed 

control programs and intake relocation 


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will cut overall pathogen levels by 

reducing fecal contamination in the 

source water. Membrane, bag, and 

cartridge filters will remove pathogenic 

protozoa like Giardia lamblia that are 

similar in size to or larger than 

Cryptosporidium. Lowering finished 

water turbidity from conventional and 

direct filtration will improve removal of 

pathogens across a broad size range, 

including viruses, bacteria, and 

protozoa. Inactivation technologies like 

ozone and UV are highly effective 

against a large number of different 

pathogen types. 

Some membrane technologies that 

PWSs may install to comply with the 

LT2ESWTR can also reduce or eliminate 

chemical contaminants including 

arsenic, DBPs, and atrazine. The use of 

UV for inactivation of Cryptosporidium 

may reduce the chlorine dosage that 

some PWSs must apply, which can 

reduce levels of DBPs. EPA has recently 

finalized a rule to further control arsenic 

levels in drinking water and is 

concurrently establishing the Stage 2 

DBPR to address DBP control. 

The extent to which the LT2ESWTR 

can reduce the overall risk from other 

contaminants has not been 

quantitatively evaluated because EPA 

lacks sufficient data on the cooccurrence among Cryptosporidium and 

other microbial pathogens and 

contaminants. Further, due to the 

difficulties in establishing which PWSs 

would have multiple problems, such as 

microbial contamination, arsenic, and 

DBPs or any combination of the three, 

no estimate was made of the potential 

cost savings from addressing more than 

one contaminant simultaneously. 

H. Are There Increased Risks From 

Other Contaminants? 

It is unlikely that the LT2ESWTR will 

result in a significant increase in risk 

from other contaminants for most PWSs. 

Many of the options that PWSs will 

select to comply with the LT2ESWTR, 

such as UV, additional or improved 

filtration, and watershed control, do not 

form DBPs. Ozone, another technology 

that is effective against 

Cryptosporidium, does form DBPs (e.g., 

bromate). However, bromate is currently 

regulated under the Stage 1 DBPR, and 

PWSs will have to comply with this 

regulation if they implement ozone to 

meet the LT2ESWTR. 

I. What Are the Effects of the 

Contaminant on the General Population 

and Groups Within the General 

Populations That Are Identified as 

Likely To be at Greater Risk of Adverse 

Health Effects? 

Section III of this preamble discusses 

the health effects associated with 

Cryptosporidium on the general 

population as well as the effects on 

other sensitive sub-populations. In 

addition, health effects associated with 

children and pregnant women are 

discussed in greater detail in section 

VII.G of this preamble. 

J. What Are the Uncertainties in the 

Risk, Benefit, and Cost Estimates for the 

LT2ESWTR? 

For today’s final rule, EPA has 

modeled the current baseline risk from 

Cryptosporidium exposure through 

drinking water, along with the reduction 

in risk and the 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 LT2ESWTR 

EA has an extensive discussion of 

relevant uncertainties (USEPA 2005a), 

and a brief summary of the major 

uncertainties follows. 

In regard to the risk estimates, the 

most significant areas of uncertainty are 

Cryptosporidium occurrence, treatment, 

and infectivity. Among the three 

available occurrence data sets, the ICR 

plant-mean data were higher than the 

ICRSSM or ICRSSL plant-mean data at 

the 90th percentile. The reasons for 

these differing results are not well 

understood but may stem from year-toyear variation in occurrence and 

differences in the sampling and 

measurement methods employed. The 

ICRSSM and ICRSSL data sets use a 

newer, more reliable sampling method 

but include fewer plants and a shorter 

time frame. Additional uncertainty is 

associated with estimating finished 

water occurrence because the analysis is 

based on estimates of treatment plant 

performance in removing 

Cryptosporidium. 

EPA has addressed some of the 

uncertainty in occurrence by evaluating 

benefits and costs for regulatory 

alternatives with each Cryptosporidium 

data set. Further, in the 2-dimensional 

Monte Carlo simulation models used to 

estimate risk, key parameters like 

occurrence and treatment efficiency are 

treated as both variable and uncertain. 

This approach is intended to account for 

the limitations in available data and the 

recognized variability in these 

parameters among PWSs. 

EPA has also considered occurrence 

data from additional sources. For 

example, the LT2ESWTR EA discusses 

a study of infectious Cryptosporidium 

in the finished water of 82 filtration 

plants by Aboytes et.al, 2004. The mean 

level of infectious Cryptosporidium 

measured in this study is higher than 

EPA has estimated using the ICR, 

ICRSSM, or ICRSSL data sets. This 

result suggests that Cryptosporidium 

occurrence at these plants may have 

exceeded levels during the ICR and 

ICRSS surveys or that EPA may have 

overestimated the efficiency of 

treatment plants in removing 

Cryptosporidium. 

In regard to Cryptosporidium 

infectivity, EPA evaluated data from 

human feeding studies conducted with 

different Cryptosporidium isolates. The 

measured infectivity of these isolates 

varied widely, however, and how well 

these isolates represent 

Cryptosporidium that causes disease in 

PWSs is uncertain. In addition, 

extrapolating from the higher 

Cryptosporidium dosing levels used in 

the human feeding studies to the 

exposure levels typical for drinking 

water (e.g., one oocyst) is uncertain. 

Another source of uncertainty is 

differences that exist among populations 

groups, such as individuals that are 

more sensitive (e.g., children, 

immunocompromised) or less sensitive 

(previously infected adults). 

EPA accounted for some of this 

uncertainty in infectivity by treating the 

human feeding study results for 

different Cryptosporidium isolates as 

random samples from a larger and 

unknown environmental distribution of 

Cryptosporidium infectivity. EPA used a 

variety of models for this analysis, as 

recommended by the SAB, and presents 

results for a range of models to account 

for uncertainty in model selection. In 

addition, limited data on levels of 

Cryptosporidium in the 1993 

Milwaukee outbreak and associated 

disease incidence suggest that the 

infectivity of the Cryptosporidium 

responsible for that outbreak is within 

the range EPA has estimated for the risk 

assessment in today’s rule. 

Unquantified benefits from the 

reduction of co-occurring microbial 

pathogens, as described earlier, are a 

significant source of uncertainty in the 

estimate of benefits for the LT2ESWTR. 

EPA is also uncertain about the 

monetization of avoided disease from 

Cryptosporidium and has addressed this 

uncertainty through the use of both 

traditional and enhanced COI values for 

benefits estimates. 

While all of the significant costs of 

today’s rule have been identified by 


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EPA, there are uncertainties in the 

estimates. Occurrence is the most 

significant source of uncertainty in 

costs, and EPA has attempted to account 

for this uncertainty through the use of 

different occurrence data sets and 

Monte Carlo modeling as described 

previously. EPA has also estimated 

uncertainty in unit process costs for 

treatment technologies. In addition, the 

cost assessment for today’s rule includes 

sensitivity analyses, such an assessment 

of the impact of influent bromide levels 

on technology selection. Chapter 6 of 

the LT2ESWTR EA provides a fuller 

description of uncertainties in the cost 

estimates (USEPA 2005a). 

Last, EPA has recently finalized or is 

currently finalizing new regulations for 

arsenic, radon, Cryptosporidium in 

small surface water PWSs, filter 

backwash recycling, microbial 

pathogens in PWSs using ground water, 

and DBPs. These rules may have 

overlapping impacts on some PWSs, but 

the extent is not possible to estimate 

due to lack of information on cooccurrence. However, PWSs may choose 

treatment technologies that will address 

multiple contaminants. Therefore, while 

the total cost impact of these drinking 

water rules is uncertain, it is most likely 

less than the estimated total cost of all 

individual rules combined. 

K. What Is the Benefit/Cost 

Determination for the LT2ESWTR? 

The Agency has determined that the 

benefits of the LT2ESWTR justify the 

costs. As discussed in section VII.C, the 

rule provides a large reduction in 

endemic cryptosporidiosis illness and 

mortalities. More stringent alternatives 

provide greater reductions but at higher 

costs. Alternative A1 provides the 

greatest overall reduction in illnesses 

and mortalities but the incremental 

benefits between this option and 

alternative A3 (today’s final rule) are 

relatively small while the incremental 

costs are significant. In addition, today’s 

rule, unlike alternative A1, specifically 

targets those PWSs whose source water 

requires higher levels of treatment. 

Tables VI.K–1a and VI.K–1b present 

net benefits for the four regulatory 

alternatives that were evaluated. 

Generally, analysis of net benefits is 

used to identify alternatives where 

benefits exceed costs, as well as the 

alternative that maximizes net benefits. 

However, as with the analysis of 

incremental net benefits discussed 

previously, the usefulness of this 

analysis in evaluating regulatory 

alternatives for the LT2ESWTR is 

somewhat limited because many 

benefits from this rule are unquantified 

and nonmonetized. Analyses of net 

benefits should consider both quantified 

and unquantified (where possible) 

benefits and costs. 

Also, as noted earlier, the regulatory 

alternatives considered for the 

LT2ESWTR vary both in the population 

that experiences benefits and costs (i.e., 

treatment bin boundaries) and the 

magnitude of the benefits and costs (i.e., 

treatment requirements). Consequently, 

the more stringent regulatory 

alternatives provide benefits to 

population groups that do not 

experience any benefit under less 

stringent alternatives. 

As shown by Tables VI.K–1a and 

VI.K–1b, net benefits are positive for all 

four regulatory alternatives evaluated 

under most occurrence and discount 

rate scenarios. With both the enhanced 

COI and traditional COI, net benefits are 

highest for the alternative A3, which is 

today’s final rule, under the majority of 

occurrence distributions and discount 

rates evaluated. 


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In addition to the net benefits of the 

LT2ESWTR, the Agency used several 

other techniques to compare costs and 

benefits. For example, EPA calculated 

the cost of the rule per case avoided. 

Tables VI.K–2a, b and c show both the 

cost of the rule per illness avoided and 

cost of the rule per death 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. With the 

exception of alternative A1, the rule 

options look favorable when the cost per 

case avoided is compared to both the 

weighted cost of cryptosporidiosis 

illness ($844 and $274 for the two COI 

approaches) and the mean value of a 

statistical death avoided—

approximately $7 million dollars. 

Additional information about this 

analysis and other methods of 

comparing benefits and costs can be 

found in chapter 8 of the LT2ESWTR 

EA (USEPA 2005a). 


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L. Summary of Major Comments 

EPA received significant public 

comment on the analysis of benefits and 

costs of the August 11, 2003 proposed 

LT2ESWTR in the following areas: 

Cryptosporidium occurrence, drinking 

water consumption, Cryptosporidium 

infectivity (i.e., dose-response), and 

valuation of benefits. The following 

discussion summarizes public comment 

in these areas and EPA’s responses. 

1. Cryptosporidium Occurrence 

With respect to the analysis of 

Cryptosporidium occurrence, two areas 

that received significant public 

comment are the quality of the ICR and 

ICRSS data sets (i.e., whether the 

estimates derived from them should be 

regarded as equally plausible) and the 

treatment of samples in which no 

Cryptosporidium is detected (i.e., 

observed zeros). 

a. Quality of the ICR and ICRSS data 

sets. As noted earlier, the ICR, ICRSSM, 

and ICRSSL data sets differ significantly 

in the high concentration portion of the 

occurrence distribution (e.g., 90th 

percentile). While the measurement 

method employed in the ICRSS had 

higher recovery and less variable 

volumes assayed, the ICR produced a 

much greater number of assays and 

source waters sampled. Lacking a 

technical basis to conclude that one data 

set provides a better estimate, EPA 

conducted separate analyses of costs 

and benefits for all three data sets. EPA 

requested comment on this approach. 

The majority of commenters on this 

issue supported EPA’s approach of 

analyzing the three data sets separately 

to represent uncertainty about 

occurrence. Two commenters suggested 

that the ICR data would be more reliable 

for estimating national occurrence due 

to the larger number of samples, while 

two others viewed the ICRSS data as 

more reliable due to the improved 

analytical method. No commenters 

provided a technical analysis indicating 

that one data set is more accurate. Given 

these comments, EPA has retained the 

approach of analyzing costs and benefits 

separately for each occurrence data set 

in today’s final rule. 

b. Treatment of observed zeros. One 

commenter remarked that the majority 

of samples in which no oocysts were 

detected (i.e., observed zeros) likely 

contained no oocysts in the volume 

assayed. This commenter was 

concerned with a parameter in EPA’s 

occurrence analysis model for ‘‘true 

zero,’’ which characterizes the 

likelihood that a source water is entirely 

free of Cryptosporidium at all times. In 

EPA’s model, the true zero parameter 

was assigned a value of 0.1 percent. As 

described in USEPA (2005b), EPA based 

this assumption on the finding that 

intensive sampling of surface waters 

usually detects Cryptosporidium, even 

in protected watersheds. The 

commenter concluded, however, that 

the true zero parameter resulted in the 

model assigning a value of at least 1 

oocyst to 99.9 percent of samples. 

EPA responds that the true zero 

parameter in the occurrence analysis 

model does not operate in this way. 

While the model is set-up to estimate 

mean source water concentrations and 

not the concentrations in individual 

volumes assayed, the model recognizes 

that the majority of samples in the ICR 

and ICRSS contained no oocysts. The 

model does assume that few, if any, of 

the source waters sampled in these 

surveys never contained a single oocyst 

(the meaning of the true zero 

parameter). EPA has clarified the 

definition of the true zero parameter in 

USEPA (2005b). EPA has also 

conducted a sensitivity analysis in 

which the true zero parameter was 

varied from values of 0 to 50 percent, 

with little effect on estimates of risk, 

benefit, and cost for today’s rule. 

2. Drinking Water Consumption 

Two commenters were concerned 

with the distribution for drinking water 

consumption that EPA used in the 

proposed LT2ESWTR. This distribution, 

which was based on a 1994–1996 survey 

by the United States Department of 

Agriculture (USDA), reflects water 

consumption from all sources. 

Commenters recommended two 

modifications to this approach: (1) 

Adjust the distribution to account for 

factors like bottled water and boiled 

water use; and (2) use an alternative 

distribution from the USDA survey that 

reflects consumption of community 

water system (CWS) water only. 


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In response, EPA agrees that the 

distribution should be adjusted to 

remove consumption attributable to 

bottled water. For the consumption 

distribution in today’s final rule, EPA 

subtracted bottled water usage, based on 

information in the USDA survey, which 

had the effect of reducing consumption 

by approximately 14 percent in 

comparison to the proposal. EPA does 

not have information on the 

effectiveness of heating water to make 

coffee or tea for inactivating 

Cryptosporidium and has not modified 

the consumption distribution on this 

basis. 

EPA continues to believe that the 

USDA distribution for consumption of 

water from all sources, minus bottled 

water consumption, provides the best 

available estimate for consumption of 

water from CWSs for people served by 

CWSs. The USDA distribution for 

consumption of CWS water only, which 

a commenter recommended, includes 

people not served by CWSs (e.g., people 

with private wells). Inclusion these 

individuals has the effect of 

underestimating the consumption of 

CWS water for people served by CWSs 

in this distribution. In contrast, the 

distribution for consumption of water 

from all sources includes people not 

served by CWSs and the sources those 

people use (e.g., private wells). This 

avoids the problem of underestimating 

consumption for individuals served by 

CWS. Accordingly, EPA has retained the 

use of this distribution in today’s final 

rule, with the adjustment stated 

previously for bottled water 

consumption. 

3. Cryptosporidium Infectivity 

In regard to Cryptosporidium 

infectivity (i.e., dose-response 

assessment), EPA received significant 

comment on limitations in the human 

feeding studies (e.g. representativeness 

of Cryptosporidium isolates used in the 

studies, numbers of subjects) and 

uncertainty in extrapolating from high 

study doses to low drinking water 

doses. EPA believes that the statistical 

analysis of dose-response data, as 

described in USEPA (2005a), properly 

accounted for these limitations and 

uncertainties. 

The statistical models used by EPA 

treated the isolates studied as a random 

sample from a larger population of 

environmental isolates, treated the 

subjects studied as a random sample 

from the larger population of healthy 

individuals, and treated each 

individual’s outcome as a chance event, 

where the infection probability is a 

function of the challenge dose. 

Collectively, these uncertainties 

contributed to the significant 

uncertainty in EPA’s estimate of the 

likelihood of infection given one oocyst 

ingested. 

Since the LT2ESWTR proposal, EPA 

has reviewed results from additional 

human feeding studies with 

Cryptosporidium isolates and analyzed 

data from these and the feeding studies 

considered for the proposal with 

additional dose-response models 

(USEPA 2005a). As described in Chapter 

5 and Appendix N of the LT2ESWTR 

EA, the infectivity estimates from the 

proposal are near the middle of the 

range of estimates derived with the 

additional feeding study data and doseresponse models. Further, the mean 

estimates from these new analyses fall 

within the 90th percentile uncertainty 

bounds for infectivity estimates from the 

proposal (USEPA 2005a). Consequently, 

EPA believes that the infectivity 

estimates from the additional feeding 

study data and dose-response models 

are consistent with and supportive of 

the estimates of infectivity from the 

proposal. Further, EPA’s estimates of 

infectivity are consistent with data on 

the infectivity of Cryptosporidium in 

the 1993 Milwaukee outbreak (USEPA 

2005a). 

4. Valuation of Benefits 

In the area of benefits valuation, EPA 

received significant public comment on 

the valuation of morbidity, valuation of 

lost time under the Enhanced COI 

approach, and unquantified benefits. 

a. Valuation of morbidity. EPA 

received a comment that endemic cases 

that do not show up in public health 

surveillance data may be too mild (and 

perhaps even asymptomatic) to be 

economically significant. EPA believes 

endemic cases are significant in terms of 

public health risk and economic 

impacts. As discussed earlier, only a 

small fraction of the millions of cases of 

gastrointestinal illnesses are traced to a 

specific illness (such as 

cryptosporidiosis); yet endemic disease 

clearly exists and those illnesses, even 

if mild, have public health 

consequences and economic impacts 

(e.g., missed work). For example, the 

benefits model in the EA assumes that 

88 percent of all cases are mild, and yet 

those illnesses represent significant 

impacts nationally. Further, the risk 

assessment model separately computes 

infections and illnesses. Thus, 

asymptomatic infections are excluded; 

only avoided illnesses are assigned 

monetary benefits. 

b. Valuation of lost time under the 

enhanced cost of illness (COI) approach. 

One commenter extensively questioned 

the approach used to value lost leisure 

and nonwork time under the Enhanced 

COI approach, noting concerns about 

the relationship of the approach to 

standard economics practices, the 

plausibility of the resulting values, and 

the extent of peer review. The following 

discussion summarizes EPA’s responses 

on these issues. 

As discussed in detail in the EA 

(USEPA 2005a), EPA recognizes that the 

preferred approach for valuing health 

risk reductions is to rely on estimates of 

individual willingness to pay (WTP). In 

the absence of suitable WTP estimates, 

analysts often rely on approaches 

similar to the Traditional COI approach 

used for this rule, as noted by the 

commenter. However, empirical 

research as well as theoretic concerns 

suggest that these types of COI 

approaches will generally understate 

true WTP. 

EPA designed the Enhanced COI 

approach to correct for one potential 

source of understatement—the impact of 

illness on unpaid work and leisure time. 

While the Enhanced COI approach is 

innovative, it is rooted in standard 

welfare economic theory and builds on 

approaches used to value time in 

numerous studies in the labor, 

transportation, recreation, and health 

economics literature. The commenter is 

concerned, however, that the Enhanced 

COI approach values nonwork time at a 

higher rate than many recreational 

studies, several of which value travel 

time at one-third of the wage rate. EPA’s 

extensive review of the recreational 

literature suggests, however, that there 

is no consensus regarding the value of 

travel time, as discussed in the 

Appendix P of the EA (USEPA 2005a). 

In addition, travel has both pleasant and 

unpleasant aspects and hence may be 

valued less than other leisure activities, 

many of which may be valued at a rate 

higher than foregone wages. 

To test the plausibility of the results, 

the commenter compares the value of a 

‘‘lifetime case’’ of cryptosporidiosis to 

the value of statistical life (VSL) and 

suggests that the results (which show 

that such a case would be roughly 70 

percent of VSL) are improbably high. 

However, EPA believes that this 

comparison is seriously flawed. There is 

no generally accepted standard for 

determining whether values for nonfatal 

risk reductions are ‘‘reasonable’’

compared to values for fatal risk 

reductions. In addition, the calculation 

of the value of a lifetime case of 

cryptosporidiosis contains several 

computational errors, and represents the 

loss of all waking time (not just losses 

attributable to cryptosporidiosis) and so 

is seriously overstated. Perhaps most 

important, the approach used to value 


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time losses in the Enhanced COI 

estimate is appropriate only for 

marginal changes in time use; it is not 

appropriate for the types of lifetime 

changes considered in the comparison. 

The Enhanced COI estimates are 

based on an approach developed in the 

EPA report, Valuing Time Losses Due to 

Illness under the 1996 Amendments to 

the Safe Drinking Water Act (USEPA 

2005e). This report has been subject to 

two rounds of independent peer review. 

In conclusion, EPA believes that 

including the Enhanced COI in 

conjunction with the Traditional COI is 

justified theoretically and that including 

both measures increases EPA’s ability to 

understand the impacts of the rule. 

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’’ because it may have an annual 

effect on the economy of $100 million 

or more (estimated annual costs are $93 

to 133 million and $107 to 150 million 

at 3 and 7 percent discount rates, 

respectively). As such, this action was 

submitted to OMB for review. Changes 

made in response to OMB suggestions or 

recommendations are 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 2040–0266. 

The information collected as a result 

of this rule will allow the States and 

EPA to determine appropriate 

requirements for specific PWSs and to 

evaluate compliance with the rule. For 

the first 3 years after LT2ESWTR 

promulgation, the major information 

requirements concern monitoring 

activities and compliance tracking. The 

information collection requirements are 

mandatory (40 CFR part 141) and the 

information collected is not 

confidential. 

The estimate of annual average 

burden hours for the LT2ESWTR during 

the first three years following 

promulgation is 141,295 hours. The 

annual average cost estimate is $4.4 

million for labor and $7 million per year 

for operation and maintenance 

including lab costs (which is a purchase 

of service). The burden hours per 

response is 0.63 hours and the cost per 

response is $50.35. The frequency of 

response (average responses per 

respondent) is 90.3, annually. The 

estimated number of likely respondents 

is 2,503 (the product of burden hours 

per response, frequency, and 

respondents does not total the annual 

average burden hours due to rounding). 

Note that the burden hour estimates for 

the first 3-year cycle include some large 

PWS but not small PWS monitoring. 

Conversely, burden estimate for the 

second 3-year cycle will include 

remaining monitoring for large systems 

(those serving between 10,000 and 

49,999 people) and small PWS 

monitoring, but not for large PWS 

serving 50,000 or more, which will have 

been completed by then. 

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 Counsel 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. 


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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 directly regulated by 

this final rule are PWSs serving fewer 

than 10,000 people. We have 

determined that 152 of the 6,574 small 

PWSs, or 2.3 percent, regulated by the 

LT2ESWTR will experience an impact 

of 1 percent or greater of average annual 

revenues; further, 18 PWSs, which are 

0.3 percent of the small PWSs regulated 

by this rule, will experience an impact 

of 3 percent or greater of average annual 

revenues (see Table VII.C–1). 

TABLE VII.C–1.—ANNUALIZED COMPLIANCE COST AS A PERCENTAGE OF REVENUES FOR SMALL ENTITIES (2003$) 

PWSs by ownership type and system 

size 

Number of 

small 

systems 

Percent of 

small 

systems 

Average 

annual 

estimated 

revenues 

per system($) 

Systems experiencing 

costs of ≥1% of their 

revenues 

Systems experiencing 

costs of ≥3% of their 

revenues 

Number of 

systems 

Percent of 

systems 

Number of 

systems 

Percent of 

systems 

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

Small Government PWSs ........................ 2,827 43 2,649,186 65 2.3 8 0.3 

Small Business PWSs ............................. 2,452 37 2,555,888 57 2.3 7 0.3 

Small Organization PWSs ....................... 1,295 20 4,750,838 5 0.4 2 0.1 

All Small Entity PWSs ...................... 6,574 100 2,981,331 152 2.3 18 0.3 

Note: Detail may not add due to independent rounding. Data are based on the means of the highest modeled distributions using Information 

Collection Rule occurrence data set. Costs are discounted at 3 percent, summed to present value, and annualized over 25 years. Source: Chapter 7 and Appendix H of the LT2ESWTR EA (USEPA 2005a). 

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 

LT2ESWTR contains a number of 

provisions to minimize the impact of 

the rule on PWSs generally, and on 

small PWSs in particular. The risktargeted approach of the LT2ESWTR 

will impose additional treatment 

requirements only on the subset of 

PWSs with the highest vulnerability to 

Cryptosporidium, as indicated by source 

water pathogen levels. This approach 

will spare the majority of PWSs from the 

cost of installing additional treatment. 

Also, development of the microbial 

toolbox under the LT2ESWTR will 

provide both large and small PWSs with 

broad flexibility in selecting costeffective compliance options to meet 

additional treatment requirements. 

Small PWSs will monitor for E. coli 

as a screening analysis for source waters 

with low levels of fecal contamination. 

Cryptosporidium monitoring will only 

be required of small PWSs if they 

exceed the E. coli trigger value. Because 

E. coli analysis is much cheaper than 

Cryptosporidium analysis, the use of E. 

coli as a screen will significantly reduce 

monitoring costs for the majority of 

small PWSs. Further, small PWSs will 

not be required to initiate their 

monitoring until large PWS monitoring 

has been completed. This will provide 

small PWSs with additional time to 

become familiar with the rule and to 

prepare for monitoring and other 

compliance activities. 

Funding may be available from 

programs administered by EPA and 

other Federal agencies to assist small 

PWSs in complying with the 

LT2ESWTR. 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 $1.275 

billion for the DWSRF program in fiscal 

year 1997, and has provided an 

additional $4.113 billion for the DWSRF 

program for fiscal years 1999 through 

2003. 

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, 


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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 

contains a Federal mandate that may 

result in expenditures of $100 million or 

more for State, local, and Tribal 

governments, in the aggregate, or the 

private sector in any one year. 

Accordingly, EPA has prepared under 

section 202 of the UMRA a written 

statement which is summarized below. 

Table VII.D–1 illustrates the 

annualized public and private costs for 

the LT2ESWTR. 

A more detailed description of this 

analysis is presented in Economic 

Analysis for the LT2ESWTR (USEPA 

2005a). 

As noted in section III, 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. 

Section VI of this preamble discusses 

the cost and benefits associated with the 

LT2ESWTR. Details are presented in the 

Economic Analysis for the LT2ESTWR 

(USEPA 2005a). EPA quantified costs 

and benefits for four regulatory 

alternatives. The four alternatives are 

described in section VI. Table VII.D–2 

summarizes the range of annual costs 

and benefits for each alternative. 


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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, 

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 7 of Economic Analysis for 

the LT2ESWTR (USEPA 2005a). 

EPA has concluded that the 

LT2ESWTR will not cause a 

disproportionate budgetary effect. This 

rule imposes the same requirements on 

PWSs nationally and does not 

disproportionately affect any segment. 

This rule will treat similarly situated 

PWSs (in terms of size, water quality, 

available data, installed technology, and 

presence of uncovered finished storage 

facilities) in similar (proportionate) 

ways, without regard to geographic 

location, type of community, or segment 

of industry. The LT2ESWTR is a rule 

where requirements are proportionate to 

risk. Although some groups may have 

differing budgetary effects as a result of 

the LT2ESWTR, those costs are 

proportional to the need for greater 

information (monitoring) and risk posed 

(degree of treatment required). The 

variation in cost between large and 

small PWSs is due to economies of scale 

(a larger PWS can distribute cost across 

more customers). Regions will have 

varying impacts due to the number of 

affected PWSs. 

Under UMRA section 202, EPA is 

required to estimate the potential 

macro-economic effects of the 

regulation. These types of effects 

include those on productivity, economic 

growth, full employment, creation of 

productive jobs, and international 

competitiveness. Macro-economic 

effects tend to be measurable in 

nationwide econometric models only if 

the economic impact of the regulation 

reaches 0.25 percent to 0.5 percent of 

Gross Domestic Product (GDP). In 2003, 

real GDP was $10,398 billion, so a rule 

would have to cost at least $26 billion 

to have a measurable effect. A regulation 

with a smaller aggregate effect is 

unlikely to have any measurable impact 

unless it is highly focused on a 

particular geographic region or 

economic sector. 

The macro-economic effects on the 

national economy from the LT2ESWTR 

should not have a measurable effect 

because the total annual costs for 

today’s rule range from $93 million to 

$133 million based on median 

Cryptosporidium occurrence 

distributions from the ICRSSL and 

Information Collection Rule data sets 

and a discount rate of 3 percent ($107 

to $150 million at a 7 percent discount 

rate). These annualized figures will 

remain constant over the 25-year 

implementation period that was 

evaluated, while GDP will probably 

continue to rise. Thus, the LT2ESWTR 

costs as a percentage of the national 

GDP will only decline over time. Costs 

will not be highly focused on a 

particular geographic region or sector. 

Consistent with the intergovernmental 

consultation provisions of section 204 of 

the UMRA, EPA initiated consultations 

with the governmental entities affected 

by this rule prior to the proposal. A 

description of the consultations is found 

in the proposed rule (USEPA 2003a). 

As required under section 205 of 

UMRA, EPA considered several 

regulatory alternatives to address PWSs 

at risk for contamination by microbial 

pathogens, specifically including 

Cryptosporidium. A detailed discussion 

of these alternatives can be found in 

section VI of the preamble and also in 

the Economic Analysis for the 

LT2ESWTR (USEPA 2005a). 

Among the regulatory alternatives 

considered for the LT2ESWTR, as 

described in section VI, EPA believes 

the alternative in today’s rule is the 

most cost-effective that achieves the 

objectives of the rule. The objective of 

the LT2ESWTR is to achieve feasible 

risk reduction from Cryptosporidium 

and other pathogens in vulnerable PWSs 

where current regulations do not 

provide sufficient protection. 

EPA evaluated a less costly and less 

burdensome alternative. However, that 

alternative would provide no benefit to 

several thousand consumers who, under 

the alternative in today’s final rule, will 

receive benefits that most likely exceed 

their costs, based on EPA estimates. 

This is illustrated in the LT2ESWTR 

Economic Analysis (USEPA 2005a). By 

failing to reduce risk for consumers 

where additional treatment 

requirements would be cost-effective, 

the less costly alternative does not 

appear to achieve the objectives of the 

LT2ESWTR. 

The other alternatives considered by 

the Agency achieve the objectives of the 

rule, but are more costly, more 

burdensome, and potentially less costeffective. The alternative in today’s rule 

targets additional treatment 

requirements to PWSs with the highest 

vulnerability to Cryptosporidium and 

maximizes net benefits under a broad 

range of conditions (USEPA 2005a). 

Consequently, EPA has found the 

alternative in today’s rule to be the most 

cost-effective among those that achieve 

the objectives of the rule. 

EPA has determined that this rule 

contains no regulatory requirements that 

might significantly or uniquely affect 

small governments. Thus, today’s rule is 

not subject to the requirements of 

section 203 of UMRA. 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 PWSs to 

comply with the LT2ESWTR range from 


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$8.1 to $13.4 million at a 3% discount 

rate and $8.3 to $13.5 million at a 7% 

discount rate. While the treatment 

requirements of the LT2ESWTR apply 

uniformly to both small and large PWSs, 

large PWSs bear a majority of the total 

costs of compliance with the rule. This 

is due to the fact that large PWSs treat 

a majority of the drinking water that 

originates from surface water sources. 

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.’’

Under Executive Order 13132, EPA 

may not issue a regulation that has 

federalism 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 State and 

local governments, or EPA consults with 

State and local officials early in the 

process of developing the regulation. 

EPA has concluded that this final rule 

may have federalism implications, 

because it may impose substantial direct 

compliance costs on State or local 

governments, and the Federal 

government will not provide the funds 

necessary to pay those costs. The final 

rule may result in expenditures by State, 

local, and Tribal governments, in the 

aggregate of $100 million or more in any 

one year. Costs are estimated to range 

from $93 to $133 million at a 3 percent 

discount rate and $107 to $150 million 

using a 7 percent discount rate based on 

the median distribution modeled from 

ICRSSL and Information Collection Rule 

Cryptosporidium occurrence data sets. 

Accordingly, EPA provides the 

following federalism summary impact 

statement as required by section 6(b) of 

Executive Order 13132. 

EPA consulted with representatives of 

State and local officials early in the 

process of developing today’s rule to 

permit them to have meaningful and 

timely input into its development. As 

described in the proposed rule (USEPA 

2003a), this consultation included State 

and local government representatives on 

the Stage 2 M–DBP Federal Advisory 

Committee (whose recommendations 

were largely adopted in today’s rule), 

the representatives from small local 

governments to the SBAR panel, a 

meeting with representatives from the 

Association of State Drinking Water 

Administrators, the National Governors’

Association, the National Conference of 

State Legislatures, the International 

City/County Management Association, 

the National League of Cities, the 

County Executives of America, and 

health departments, consultation with 

Tribal governments at four meetings and 

through the Advisory Committee 

process, and comments from State and 

local governments on a pre-proposal 

draft of the LT2ESWTR. 

Representatives of State and local 

officials were generally concerned with 

ensuring that drinking water regulations 

are adequately protective of public 

health and that any additional 

regulations achieve significant health 

benefits in return for required 

expenditures. They were specifically 

concerned with the burden of the rule, 

both in cost and technical complexity, 

giving flexibility to PWSs and States, 

balancing the control of microbial risks 

and DBP risks, funding for 

implementing new regulations, equal 

protection for small PWSs, and early 

implementation of monitoring by large 

PWSs. 

EPA has concluded that the 

LT2ESWTR is needed to reduce the 

public health risk associated with 

Cryptosporidium in drinking water. As 

shown in section VI, estimated benefits 

for the rule are significantly higher than 

costs. Further, EPA believes that today’s 

rule addresses many of the concerns 

expressed by representatives of 

government officials. 

Under the LT2ESWTR, expenditures 

for additional treatment are targeted to 

the fraction of PWSs with the highest 

vulnerability to Cryptosporidium, 

thereby minimizing burden for the 

majority of PWSs, which will not be 

required to provide additional 

treatment. The microbial toolbox of 

compliance options will provide 

flexibility to PWSs in meeting 

additional treatment requirements, and 

States have the flexibility to award 

treatment credits based on site-specific 

demonstrations. Disinfection profiling 

provisions are intended to ensure that 

PWSs do not reduce microbial 

protection as they take steps to reduce 

exposures to DBPs. 

The LT2ESWTR achieves equal public 

health protection for small PWSs. 

However, the use of E. coli monitoring 

by small PWSs as a screening analysis 

to determine the need for 

Cryptosporidium monitoring will 

reduce monitoring costs for most small 

PWSs. Capital projects related to the 

rule will be eligible for funding from the 

Drinking Water State Revolving Fund, 

which includes specific funding for 

small communities. EPA is planning to 

support the initial monitoring by large 

PWSs that takes place within the first 

few years after rule promulgation. This 

will substantially reduce the burden on 

States associated with early 

implementation of monitoring 

requirements. 

In the spirit of Executive Order 13132, 

and consistent with EPA policy to 

promote communications between EPA 

and State and local governments, EPA 

specifically solicited comment on the 

proposed rule from State and local 

officials. 

As required by section 8(a) of 

Executive Order 13132, EPA included a 

certification from its Federalism Official 

stating that EPA had met the Executive 

Order’s requirements in a meaningful 

and timely manner, when it sent the 

draft of this final rule to OMB for review 

pursuant to Executive Order 12866. A 

copy of this certification has been 

included in the public version of the 

official record for this final rule. 

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. EPA has 

identified 93 Tribal water systems 

serving a total population of 82,216 that 

may be subject to the LT2ESWTR. They 

will bear an estimated total annualized 

cost of $207,105 at a 3 percent discount 

rate ($309,583 at 7 percent) to 


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implement this rule. Estimated mean 

annualized cost per system ranges from 

$1,944 to $7,068 at a 3 percent discount 

rate ($2,905 to $10,681 at 7 percent) 

depending on PWS size (see Chapter 7 

of the LT2ESWTR Economic Analysis 

(USEPA 2005a) for details). 

Accordingly, EPA provides the 

following Tribal summary impact 

statement as required by section 5(b). 

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. This consultation is 

described in the proposed rule (USEPA 

2003a). Tribal officials were represented 

on the M–DBP Advisory Committee. 

As required by section 7(a), EPA’s 

Tribal Consultation Official has certified 

that the requirements of the Executive 

Order have been met in a meaningful 

and timely manner. A copy of this 

certification is included in the docket 

for this rule. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

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 Executive 

Order 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. 

This final rule is subject to the 

Executive Order because it is an 

economically significant regulatory 

action as defined in Executive Order 

12866, and we believe that the 

environmental health or safety risk 

addressed by this action may have a 

disproportionate effect on children. 

Accordingly, we have evaluated the 

environmental health or safety effects of 

Cryptosporidium on children. The 

results of this evaluation are contained 

in Cryptosporidium: Risk for Infants and 

Children (USEPA 2001d), which is 

available in the public docket for this 

action, and are summarized in this 

section of the preamble. Further, while 

available information is not adequate to 

conduct a quantitative risk assessment 

specifically for children, EPA has 

assessed the risk associated with 

Cryptosporidium in drinking water for 

the general population, including 

children. This assessment is described 

in the Economic Analysis for the 

LT2ESWTR (USEPA 2005a) and is 

summarized in section VI of this 

preamble. 

Children’s Environmental Health 

Cryptosporidiosis in children is 

similar to adult disease (USEPA 2001d). 

Diarrhea is the most common symptom. 

Other common symptoms in otherwise 

healthy (i.e., immunocompetent) 

children include anorexia, vomiting, 

abdominal pain, fever, dehydration and 

weight loss. 

The risk of illness and death due to 

cryptosporidiosis depends on several 

factors, including age, nutrition, 

exposure, genetic variability, disease 

and the immune status of the 

individual. Mortality resulting from 

diarrhea generally occurs at a greater 

rate among the very young and elderly 

(Gerba et al., 1996). During the 1993 

Milwaukee drinking water outbreak, 

associated mortalities in children were 

reported. Also, children with laboratoryconfirmed cryptosporidiosis were more 

likely to have an underlying disease that 

altered their immune status (Cicirello et 

al., 1997). In that study, the observed 

association between increasing age of 

children and increased numbers of 

laboratory-confirmed cryptosporidiosis 

suggested to the authors that the data 

are consistent with increased tap water 

consumption of older children. 

Asymptomatic infection can have a 

substantial effect on childhood growth 

(Bern et al., 2002). 

Cryptosporidiosis appears to be more 

prevalent in populations, such as 

children, that may not have established 

immunity against the disease and may 

be in greater contact with 

environmentally contaminated surfaces 

(DuPont et al., 1995). In the United 

States, children aged one to four years 

are more likely than adults to have the 

disease. The most recent reported data 

on cryptosporidiosis shows the 

occurrence rate (for the year 1999) is 

higher in children ages one to four (3.03 

incidence rate per 100,000) than in any 

adult age group (CDC, 2001). Evidence 

from blood sera antibodies collected 

from children during the 1993 

Milwaukee outbreak suggest that 

children had greater levels of 

Cryptosporidium infection than 

predicted for the general community 

(based on the random-digit dialing 

telephone survey method) (McDonald et 

al., 2001). 

Data indicate a lower incidence of 

cryptosporidiosis infection during the 

first year of life. This is attributed to 

breast-fed infants consuming less tap 

water and, hence, having less exposure 

to Cryptosporidium, as well as the 

possibility that mothers confer short 

term immunity to their children. For 

example, in a survey of over 30,000 

stool sample analyses from different 

patients in the United Kingdom, the one 

to five year age group suffered a much 

higher infection rate than individuals 

less than one year of age. For children 

under one year of age, those older than 

six months of age showed a higher rate 

of infection than individuals aged less 

than six months (Casemore, 1990). 

Similarly, in the U.S., of 2,566 reported 

Cryptosporidium illnesses in 1999, 525 

occurred in ages one to four (incidence 

rate of 3.03 per 100,000) compared with 

58 cases in infants under one year 

(incidence rate of 1.42 per 100,000) 

(CDC, 2001). 

An infected child may spread the 

disease to other children or family 

members (Heijbel et al., 1987, Osewe et 

al., 1996). Millard et al. (1994) 

documented greater household 

secondary transmission of 

cryptosporidiosis from children than 

from adults to household and other 

close contacts. Children continued to 

shed oocysts for more than two weeks 

(mean 16.5 days) after diarrhea 

cessation (Tangerman et al., 1991). 

While Cryptosporidium may have a 

disproportionate effect on children, 

available data are not adequate to 

distinctly assess the health risk for 

children resulting from 

Cryptosporidium-contaminated 

drinking water. In assessing risk to 

children when evaluating regulatory 

alternatives for the LT2ESWTR, EPA 

assumed the same risk for children as 

for the population as a whole. 

Section VI of this preamble presents 

the regulatory alternatives that EPA 

evaluated for the proposed LT2ESWTR. 

Among the four alternatives the Agency 

considered, three involved a risktargeting approach in which additional 

Cryptosporidium treatment 

requirements are based on source water 

monitoring results. A fourth alternative 

involved additional treatment 

requirements for all PWSs. The 

alternative requiring additional 

treatment by all PWSs was not selected 

because of concerns about feasibility 

and because it imposed costs but 

provided few benefits to PWSs with 

high quality source water (i.e., relatively 

low Cryptosporidium risk). The three 

risk-targeting alternatives were 

evaluated based on several factors, 

including costs, benefits, net benefits, 

feasibility of implementation, and other 

specific impacts (e.g., impacts on small 

PWSs or sensitive subpopulations). 


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The alternative that today’s final rule 

establishes was recommended by the 

M–DBP Federal Advisory Committee 

and selected by EPA as the Preferred 

Regulatory Alternative because it was 

deemed feasible and provides 

significant public health benefits in 

terms of avoided illnesses and deaths. 

EPA’s analysis of benefits and costs 

indicates that this alternative ranks 

highly among those evaluated with 

respect to maximizing net benefits, as 

shown in the LT2ESWTR Economic 

Analysis (USEPA 2005a). This 

document is available in the docket for 

this action. 

The result of the LT2ESWTR will be 

a reduction in the risk of illness for the 

entire population, including children. 

Because available evidence indicates 

that children may be more vulnerable to 

cryptosporidiosis than the rest of the 

population, the LT2ESWTR may, 

therefore, result in greater risk reduction 

for children than for the general 

population. 

H. Executive Order 13211: Actions 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 

LT2ESWTR would adversely affect the 

supply of energy. The LT2ESWTR does 

not regulate power generation, either 

directly or indirectly. The public and 

private utilities that the LT2ESWTR 

regulates do not, as a rule, generate 

power. Further, the cost increases borne 

by customers of water utilities as a 

result of the LT2ESWTR are a low 

percentage of the total cost of water, 

except for a very few small PWSs that 

might install advanced technologies and 

then need to 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 

LT2ESWTR. In sum, the LT2ESWTR 

does not regulate the supply of energy, 

does not generally regulate the utilities 

that supply energy, and is unlikely to 

affect significantly the customer base of 

energy suppliers. Thus, the LT2ESWTR 

would not translate into adverse effects 

on the supply of energy. 

The second consideration is whether 

the LT2ESWTR would adversely affect 

the distribution of energy. The 

LT2ESWTR does not regulate any aspect 

of energy distribution. The utilities that 

are regulated by the LT2ESWTR 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 0.036 percent. 

Therefore, EPA estimates that the 

existing connections are adequate and 

that the LT2ESWTR has no discernable 

adverse effect on energy distribution. 

The third consideration is whether 

the LT2ESWTR 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 LT2ESWTR 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 LT2ESWTR, and compares that 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 LT2ESWTR. Energy use 

is not directly stated in Technologies 

and Costs for Control of Microbial 

Contaminants and Disinfection ByProducts (USEPA 2003c), but the annual 

cost of energy for each technology 

addition or upgrade necessitated by the 

LT2ESWTR 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 $0.070/ 

kWh (USDOE 2004a). These 

calculations are shown in detail in 

Chapter 7 of the Economic Analysis for 

the LT2ESWTR (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. Results of the analysis are 

shown in Table VII.H–1 for each of the 

modeled Cryptosporidium occurrence 

distributions. The incremental national 

annual energy usage is estimated at 165 

million megawatt-hours (mW) based on 

the modeled Information Collection 

Rule occurrence distribution. 


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To determine if the additional energy 

required for PWSs to comply with the 

rule would have a significant adverse 

effect on the use of energy, the numbers 

in Table VII.H–1 are compared to the 

national production figures for 

electricity. According to the U.S. 

Department of Energy’s Information 

Administration, electricity producers 

generated 3,848 million mW of 

electricity in 2003 (USDOE 2004b). 

Therefore, even using the highest 

assumed energy use for the LT2ESWTR, 

the rule when fully implemented would 

result in only a 0.004 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 are 

highest in the summer months, so the 

most significant effects on supply would 

be seen then. In the year of 2003, U.S. 

generation capacity exceeded 

consumption by 15 percent, or 

approximately 160,00 mW (USDOE EIA 

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 19 mW for the 

modeled Information Collection Rule 

occurrence distribution. A more 

detailed derivation of this value is 

shown in Chapter 7 of the Economic 

Analysis for the LT2ESWTR (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 38 mW 

could be needed for treatment 

technologies installed to comply with 

the LT2ESWTR. This is only 0.024 

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, or use. 

While certain areas, notably California, 

have experienced shortfalls in 

generating capacity in the recent past, a 

peak incremental power requirement of 

38 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 LT2ESWTR is not likely 

to have a significant adverse effect on 

the supply, distribution, or use of 

energy. 

I. National Technology Transfer and 

Advancement Act 

As noted in the proposed rule, 

Section 12(d) of the National 

Technology Transfer and Advancement 

Act (‘‘NTTAA’’) of 1995, 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 

methods previously approved in 40 CFR 

136.3 for the analysis of E. coli in 

surface waters. These include several 

voluntary consensus methods that were 

developed or adopted by the following 

organizations: American Public Health 

Association in Standard Methods for the 

Examination of Water and Wastewater, 

20th, 19th, and 18th Editions, the 

American Society of Testing Materials 

in Annual Book of ASTM Standards—

Water and Environmental Technology, 

and the Association of Analytical 

Chemists in Official Methods of 

Analysis of AOAC International, 16th 

Edition. EPA has concluded that these 

methods have the necessary sensitivity 

and specificity to meet the data quality 

objectives of the LT2ESWTR. 

The Agency conducted a search to 

identify potentially applicable voluntary 

consensus standards for analysis of 

Cryptosporidium. However, we 

identified no such standards. Therefore, 


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EPA approves the use of the following 

methods for Cryptosporidium analysis: 

Method 1623: Cryptosporidium and 

Giardia in Water by Filtration/IMS/FA, 

2004, United States Environmental 

Protection Agency, EPA–815–R–05–002 

or Method 1622: Cryptosporidium in 

Water by Filtration/IMS/FA, 2004, 

United States Environmental Protection 

Agency, EPA–815–R–05–001. 

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 

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 did 

consult 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 charged the SAB panel with 

reviewing the following aspects of the 

LT2ESWTR proposal: 

• The analysis of Cryptosporidium 

occurrence; 

• The pre- and post-LT2ESWTR 

Cryptosporidium risk assessment; and 

• The treatment credits for the 

following four microbial toolbox 

components: raw water off-stream 

storage, pre-sedimentation, lime 

softening, and lower finished water 

turbidity. 

EPA met with the SAB to discuss the 

LT2ESWTR on June 13, 2001 

(Washington, DC), September 25–26, 

2001 (teleconference), and December 

10–12, 2001 (Los Angeles, CA). The 

SAB issued its final report for this 

review, Disinfection Byproducts and 

Surface Water Treatment: A EPA 

Science Advisory Board Review of 

Certain Elements of the Stage 2 

Regulatory Proposals, in May 2003. 

Comments from the SAB were 

generally supportive of EPA’s analysis 

of Cryptosporidium occurrence and the 

Cryptosporidium risk assessment for 

today’s rule. The SAB recommended 

some additional quality assurance 

checks for statistical models, improved 

descriptions of underlying data sets, and 

better characterization of uncertainty for 

key parameters. USEPA 2005a and 

2005b provide information on revisions 

EPA made in response to these 

comments. 

SAB comments on microbial toolbox 

options and the Agency’s responses to 

those comments are described in section 

IIII.D of this preamble. In general, the 

SAB supported treatment credit for twostage softening, recommended 

additional performance criteria to award 

treatment credit to presedimentation 

basins, recommended modifications to 

the treatment credit for combined and 

individual filter performance, and 

opposed treatment credit for off-stream 

raw water storage. 

EPA met with the NDWAC on 

November 8, 2001, in Washington, DC, 

to discuss the LT2ESWTR proposal. 

EPA specifically requested comments 

from the NDWAC on the regulatory 

approach taken in the proposed 

microbial toolbox (e.g., proposal of 

specific design and implementation 

criteria for treatment credits). The 

Council was generally supportive of 

EPA establishing criteria for awarding 

treatment credit to toolbox components, 

but recommended that EPA provide 

flexibility for States to address PWS 

specific situations. EPA believes that the 

demonstration of performance credit, 

described in section IV.D.9 provides this 

flexibility by allowing States to award 

higher or lower levels of treatment 

credit for microbial toolbox components 

based on site specific conditions. 

EPA has consulted with the U.S. 

Department of Health and Human 

Services (HHS) regarding 

Cryptosporidium health effects and has 

provided HHS with today’s 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 LT2ESWTR on the 

Technical, Financial, and Managerial 

Capacity of Public Water Systems 

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

amended, requires that in promulgating 

an NPDWR, the Administrator shall 

include an analysis of the likely effect 

of compliance with the regulation on 

the technical, managerial, and financial 

capacity of public water systems. This 

analysis can be found in the LT2ESWTR 

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. Technical, managerial, 

and financial capacity can be assessed 

through key issues and questions, 

including the following: 

Technical Capacity 

Source water adequacy .................. Does the system have a reliable source of water with adequate quantity? Is the source generally of good 

quality and adequately protected? 


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Infrastructure adequacy .................. Can the system provide water that meets SDWA standards? What is the condition of its infrastructure, including wells or source water intakes, treatment and storage facilities, and distribution systems? What is 

the infrastructure’s life expectancy? Does the system have a capital improvement plan? 

Technical knowledge and implementation.Are the system’s operators certified? Do the operators have sufficient knowledge of applicable standards? 

Can the operators effectively implement this technical knowledge? Do the operators understand the system’s technical and operational characteristics? Does the system have an effective O&M program? 

Managerial Capacity 

Ownership accountability ................ Are the owners clearly identified? Can they be held accountable for the system? 

Staffing and organization ................ Are the operators and managers clearly identified? Is the system properly organized and staffed? Do personnel understand the management aspects of regulatory requirements and system operations? Do they 

have adequate expertise to manage water system operations (i.e., to conduct implementation, monitor 

for E. coli and Cryptosporidium, install treatment, and cover or disinfect reservoir discharge to meet the 

LT2ESWTR requirements)? Do personnel have the necessary licenses and certifications? 

Effective external linkages .............. Does the system interact well with customers, regulators, and other entities? Is the system aware of available external resources, such as technical and financial assistance? 

Financial Capacity 

Revenue sufficiency ........................ Do revenues cover costs? 

Creditworthiness ............................. Is the system financially healthy? Does it have access to capital through public or private sources? 

Fiscal management and controls .... Are adequate books and records maintained? Are appropriate budgeting, accounting, and financial planning methods used? Does the system manage its revenues effectively? 

After determining the type and 

number of systems to which each 

requirement applies, EPA evaluated the 

capacity impact of each rule 

requirement on large and small systems 

affected by that particular requirement. 

EPA determined that the overall impacts 

on small systems’ technical, managerial, 

and financial capacity will vary. 

Monitoring and familiarization with 

new rules will have no significant 

effects on small systems, with the 

exception of moderate revenue 

constraints on those systems that need 

to implement monitoring for 

Cryptosporidium. The largest impacts 

will occur as a result of attaining 2.5 log 

treatment levels, covering uncovered 

reservoirs, or disinfecting reservoir 

discharge. EPA assumed that large 

systems will have the technical, 

financial, and managerial capacity to 

implement LT2ESWTR requirements 

based on the scale and complexity of 

their operations. The nature of their 

operations generally assures that they 

have access to the technical and 

managerial expertise to carry out all 

activities required by the LT2ESWTR. It 

is also generally easier for large systems 

to fund capital improvements than 

small systems, since costs can be spread 

over a larger customer base, making 

them smaller on a per-household basis. 

To meet challenges posed by rule 

requirements, it is likely that some 

small and medium systems will need to 

develop or enhance linkages with 

technical and financial assistance 

providers (including State extension 

agents). Technical and financial 

assistance providers can help systems 

analyze their needs as well as the tradeoffs between cost and health protection. 

In addition, they may be able to assist 

systems in finding the funding 

necessary to install and operate new 

equipment. The Safe Drinking Water 

Act, as amended in 1996, established 

the Drinking Water State Revolving 

Fund to make funds available to 

drinking water systems to finance 

infrastructure improvements. EPA also 

works closely with organizations such 

as the National Rural Water Association 

and the American Water Works 

Association to develop technical and 

managerial tools, materials, and 

assistance to aid small systems. 

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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Application, Implementation and 

Regulatory Issues. EPA 815–C–01–001. 

USEPA. 2001h. Guidelines Establishing Test 

Procedures for the Analysis of 

Pollutants; Analytical Methods for 

Biological Pollutants in Ambient Water; 

Proposed Rule. Federal Register. August 

30, 2001. 

USEPA. 2002a. National Primary Drinking 

Water Regulations: Long Term 1 


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Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules and Regulations 767 

Enhanced Surface Water Treatment Rule; 

Final Rule. Federal Register. January 14, 

2002. 67 FR 1812. EPA 815–Z–02–001. 

USEPA. 2002b. Process for Designing a 

Watershed Initiative. 67 FR 36172, May 

23, 2002. 

USEPA. 2002c. Method 1103.1: Escherichia 

coli (E. coli) In Water By Membrane 

Filtration Using membraneThermotolerant Escherichia coli Agar 

(mTEC). U.S. Environmental Protection 

Agency, Office of Water, Washington, 

DC. EPA–821–R–02–020. 

USEPA. 2002d. Laboratory Quality 

Assurance Evaluation Program for 

Analysis of Cryptosporidium Under the 

Safe Drinking Water Act; Agency 

Information Collection: Proposed 

Collection; Comment Request. Federal 

Register: March 4, 2002. 67 FR 9731. 

USEPA. 2003a. National Primary Drinking 

Water Regulations: Long Term 2 

Enhanced Surface Water Treatment Rule; 

Proposed Rule. 68 FR 47640, August 11, 

2003. 

USEPA. 2003b. Guidelines Establishing Test 

Procedures for the Analysis of 

Pollutants; Analytical Methods for 

Biological Pollutants in Ambient Water. 

68 FR 43272, July 21, 2003. 

USEPA. 2005a. Economic Analysis for the 

Long Term 2 Enhanced Surface Water 

Treatment Rule. U.S. Environmental 

Protection Agency, Office of Water, 

Washington, DC. EPA–821–R–06–001. 

USEPA. 2005b. Occurrence and Exposure 

Assessment for the Long Term 2 

Enhanced Surface Water Treatment Rule. 

U.S. Environmental Protection Agency, 

Office of Water, Washington, DC. EPA–

821–R–06–002. 

USEPA. 2005c. Method 1622: 

Cryptosporidium in Water by Filtration/ 

IMS/FA. EPA 815–R–05–001. 

USEPA. 2005d. Method 1623: 

Cryptosporidium and Giardia in Water 

by Filtration/IMS/FA. EPA 815–R–05–

002. 

USEPA. 2005e. Valuing Time Losses Due to 

Illness under the 1996 Amendments to 

the Safe Drinking Water Act. EPA Office 

of Water. Prepared by IEC Consultants. 

Wang, J., R. Song, and S. Hubbs. 2001. 

Particle removal through riverbank 

filtration process, in W. Julich and J. 

Schubert, eds., Proceedings of the 

Internation Riverbank Filtration 

Conference, November 2–4, 2000, 

Dusseldorf, Germany, Internationale 

Arbeitsgemeinschaft der Wasserwork im 

Rheineinzugsgebiet. 

Ware and Schaefer. 2005. The effects of time 

and temperature on flow cytometry 

enumerated live Cryptosporidium 

parvum oocysts. Letters in Applied 

Microbiology 41:385–389. 

Yang, S., S.K. Benson, C. Du, and M.C. 

Healey. 2000. Infection of 

immunosuppressed C57BL/6N adult 

mice with a single oocyst of 

Cryptosporidium parvum. J Parasitol. 

86(4):884–7. 

Yates, R., K. Scott, J. Green, J. Bruno, and R. 

De Leon. 1998. Using Aerobic Spores to 

Evaluate Treatment Plant Performance. 

Proceedings, Annual Conference of the 

American Water Works Association, 

Denver, CO. 

List of Subjects 

40 CFR Part 9 

Reporting and recordkeeping. 

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—[AMENDED] 

■ 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 ‘‘§ 141.706–141.710, 

141.713–141.714, 141.716–141.723’’. 

■ b. Under the heading ‘‘National 

Primary Drinking Water Regulations 

Implementation’’ by removing entries 

§ 142.15(c), 142.15(c)(6)–(7) and adding 

entries in numerical order for 

‘‘142.14(a)(9), 142.15(c)(6), and 

142.16(n)’’ as follows: 

§ 9.1 OMB approvals under the Paperwork 

Reduction Act. 

* * * * * 

40 CFR citation OMB control No. 

* * * * * * * 

National Primary Drinking Water Regulations 

* * * * * * * 

141.706–141.710 ........................................................................................................................................................................... 2040–0266 

141.713–141.714 ........................................................................................................................................................................... 2040–0266 

141.716–141.723 ........................................................................................................................................................................... 2040–0266 

National Primary Drinking Water Regulations Implementation 

* * * * * * * 

142.14(a)(9) ................................................................................................................................................................................... 2040–0266 

* * * * * * * 

142.15(c)(6) ................................................................................................................................................................................... 2040–0266 

* * * * * * * 

142.16(n) ........................................................................................................................................................................................ 2040–0266 

* * * * * * * 


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768 Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules and Regulations 

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 ‘‘Bag filters’’, ‘‘Bank 

filtration’’, ‘‘Cartridge filters’’, ‘‘Flowing 

stream’’, ‘‘Lake/reservoir’’, ‘‘Membrane 

filtration’’, ‘‘Plant intake’’, 

‘‘Presedimentation’’, and ‘‘Two-stage 

lime softening’’, and revising the 

definition for ‘‘Uncovered finished 

water storage facility’’ to read as 

follows: 

§ 141.2 Definitions. 

* * * * * 

Bag filters are pressure-driven 

separation devices that remove 

particulate matter larger than 1 

micrometer using an engineered porous 

filtration media. They are typically 

constructed of a non-rigid, fabric 

filtration media housed in a pressure 

vessel in which the direction of flow is 

from the inside of the bag to outside. 

Bank filtration is a water treatment 

process that uses a well to recover 

surface water that has naturally 

infiltrated into ground water through a 

river bed or bank(s). Infiltration is 

typically enhanced by the hydraulic 

gradient imposed by a nearby pumping 

water supply or other well(s). 

* * * * * 

Cartridge filters are pressure-driven 

separation devices that remove 

particulate matter larger than 1 

micrometer using an engineered porous 

filtration media. They are typically 

constructed as rigid or semi-rigid, selfsupporting filter elements housed in 

pressure vessels in which flow is from 

the outside of the cartridge to the inside. 

* * * * * 

Flowing stream is a course of running 

water flowing in a definite channel. 

* * * * * 

Lake/reservoir refers to a natural or 

man made basin or hollow on the 

Earth’s surface in which water collects 

or is stored that may or may not have 

a current or single direction of flow. 

* * * * * 

Membrane filtration is a pressure or 

vacuum driven separation process in 

which particulate matter larger than 1 

micrometer is rejected by an engineered 

barrier, primarily through a sizeexclusion mechanism, and which has a 

measurable removal efficiency of a 

target organism that can be verified 

through the application of a direct 

integrity test. This definition includes 

the common membrane technologies of 

microfiltration, ultrafiltration, 

nanofiltration, and reverse osmosis. 

* * * * * 

Plant intake refers to the works or 

structures at the head of a conduit 

through which water is diverted from a 

source (e.g., river or lake) into the 

treatment plant. 

* * * * * 

Presedimentation is a preliminary 

treatment process used to remove 

gravel, sand and other particulate 

material from the source water through 

settling before the water enters the 

primary clarification and filtration 

processes in a treatment plant. 

* * * * * 

Two-stage lime softening is a process 

in which chemical addition and 

hardness precipitation occur in each of 

two distinct unit clarification processes 

in series prior to filtration. 

Uncovered finished water storage 

facility is a tank, reservoir, or other 

facility used to store water that will 

undergo no further treatment to reduce 

microbial pathogens except residual 

disinfection and is directly open to the 

atmosphere. 

* * * * * 

■ 5. Subpart Q of part 141 is amended 

by adding § 141.211 to read as follows: 

§ 141.211 Special notice for repeated 

failure to conduct monitoring of the source 

water for Cryptosporidium and for failure to 

determine bin classification or mean 

Cryptosporidium level. 

(a) When is the special notice for 

repeated failure to monitor to be given? 

The owner or operator of a community 

or non-community water system that is 

required to monitor source water under 

§ 141.701 must notify persons served by 

the water system that monitoring has 

not been completed as specified no later 

than 30 days after the system has failed 

to collect any 3 months of monitoring as 

specified in § 141.701(c). The notice 

must be repeated as specified in 

§ 141.203(b). 

(b) When is the special notice for 

failure to determine bin classification or 

mean Cryptosporidium level to be 

given? The owner or operator of a 

community or non-community water 

system that is required to determine a 

bin classification under § 141.710, or to 

determine mean Cryptosporidium level 

under § 141.712, must notify persons 

served by the water system that the 

determination has not been made as 

required no later than 30 days after the 

system has failed report the 

determination as specified in 

§ 141.710(e) or § 141.712(a), 

respectively. The notice must be 

repeated as specified in § 141.203(b). 

The notice is not required if the system 

is complying with a State-approved 

schedule to address the violation. 

(c) What is the form and manner of 

the special notice? The form and 

manner of the public notice must follow 

the requirements for a Tier 2 public 

notice prescribed in § 141.203(c). The 

public notice must be presented as 

required in § 141.205(c). 

(d) What mandatory language must be 

contained in the special notice? The 

notice must contain the following 

language, including the language 

necessary to fill in the blanks. 

(1) The special notice for repeated 

failure to conduct monitoring must 

contain the following language: 

We are required to monitor the source of 

your drinking water for Cryptosporidium. 

Results of the monitoring are to be used to 

determine whether water treatment at the 

(treatment plant name) is sufficient to 

adequately remove Cryptosporidium from 

your drinking water. We are required to 

complete this monitoring and make this 

determination by (required bin determination 

date). We ‘‘did not monitor or test’’ or ‘‘did 

not complete all monitoring or testing’’ on 

schedule and, therefore, we may not be able 

to determine by the required date what 

treatment modifications, if any, must be 

made to ensure adequate Cryptosporidium 

removal. Missing this deadline may, in turn, 

jeopardize our ability to have the required 

treatment modifications, if any, completed by 

the deadline required, (date). 

For more information, please call (name of 

water system contact) of (name of water 

system) at (phone number). 

(2) The special notice for failure to 

determine bin classification or mean 

Cryptosporidium level must contain the 

following language: 

We are required to monitor the source of 

your drinking water for Cryptosporidium in 

order to determine by (date) whether water 

treatment at the (treatment plant name) is 

sufficient to adequately remove 

Cryptosporidium from your drinking water. 

We have not made this determination by the 

required date. Our failure to do this may 

jeopardize our ability to have the required 

treatment modifications, if any, completed by 

the required deadline of (date). For more 

information, please call (name of water 

system contact) of (name of water system) at 

(phone number). 

(3) Each special notice must also 

include a description of what the system 

is doing to correct the violation and 

when the system expects to return to 

compliance or resolve the situation. 

■ 6. Appendix A to Subpart Q of part 

141 is amended by adding entry number 

10 under I.A. to read as follows: 

Subpart Q—Public Notification of 

Drinking Water Violations 


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Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules and Regulations 769 

APPENDIX A TO SUBPART Q OF PART 141—NPDWR VIOLATIONS AND OTHER SITUATIONS REQUIRING PUBLIC NOTICE 1

Contaminant 

MCL/MRDL/TT violations 2 Monitoring & testing procedure violations 

Tier of 

public notice 

required 

Citation 

Tier of 

public notice 

required 

Citation 

I. Violations of National Primary Drinking 

Water Regulations (NPDWR): 3

A. Microbiological Contaminants 

* * * * * * * 

10. LT2ESWTR violations ......................... 2 141.710–141.720 22 2, 3 141.701–141.705 and 141.708–141.709. 

* * * * * * * 

1Violations and other situations not listed in this table (e.g., failure to prepare Consumer Confidence Reports) do not require notice, unless 

otherwise determined by the primary agency. Primacy agencies may, at their option, also require a more stringent public notice tier (e.g., Tier 1 

instead of Tier 2 or Tier 2 instead of Tier 3) for specific violations and situations listed in this Appendix, as authorized under § 141.202(a) and 

§ 141.203(a). 

2 MCL—Maximum contaminant level, MRDL—Maximum residual disinfectant level, TT—Treatment technique. 3The term Violations of National Primary Drinking Water Regulations (NPDWR) is used here to include violations of MCL, MRDL, treatment 

technique, monitoring, and testing procedure requirements. 

* * * * * * * 

22Failure to collect three or more samples for Cryptosporidium analysis is a Tier 2 violation requiring special notice as specified in § 141.211. 

All other monitoring and testing procedure violations are Tier 3. 

■ 7. Part 141 is amended by adding a 

new subpart W to read as follows: 

Subpart W—Enhanced Treatment for 

Cryptosporidium 

General Requirements 

Sec. 

141.700 General requirements. 

Source Water Monitoring Requirements 

141.701 Source water monitoring. 

141.702 Sampling schedules. 

141.703 Sampling locations. 

141.704 Analytical methods. 

141.705 Approved laboratories. 

141.706 Reporting source water monitoring 

results. 

141.707 Grandfathering previously 

collected data. 

Disinfection Profiling and Benchmarking 

Requirements 

141.708 Requirements when making a 

significant change in disinfection 

practice. 

141.709 Developing the disinfection profile 

and benchmark. 

Treatment Technique Requirements 

141.710 Bin classification for filtered 

systems. 

141.711 Filtered system additional 

Cryptosporidium treatment 

requirements. 

141.712 Unfiltered system Cryptosporidium 

treatment requirements. 

141.713 Schedule for compliance with 

Cryptosporidium treatment 

requirements. 

141.714 Requirements for uncovered 

finished water storage facilities. 

Requirements for Microbial Toolbox 

Components 

141.715 Microbial toolbox options for 

meeting Cryptosporidium treatment 

requirements. 

141.716 Source toolbox components. 

141.717 Pre-filtration treatment toolbox 

components. 

141.718 Treatment performance toolbox 

components. 

141.719 Additional filtration toolbox 

components. 

141.720 Inactivation toolbox components. 

Reporting and Recordkeeping Requirements 

141.721 Reporting requirements. 

141.722 Recordkeeping requirements. 

Requirements for Sanitary Surveys 

Performed by EPA 

141.723 Requirements to respond to 

significant deficiencies identified in 

sanitary surveys performed by EPA. 

Subpart W—Enhanced Treatment for 

Cryptosporidium 

General Requirements 

§ 141.700 General requirements. 

(a) The requirements of this subpart 

W are national primary drinking water 

regulations. The regulations in this 

subpart establish or extend treatment 

technique requirements in lieu of 

maximum contaminant levels for 

Cryptosporidium. These requirements 

are in addition to requirements for 

filtration and disinfection in subparts H, 

P, and T of this part. 

(b) Applicability. The requirements of 

this subpart apply to all subpart H 

systems, which are public water systems 

supplied by a surface water source and 

public water systems supplied by a 

ground water source under the direct 

influence of surface water. 

(1) Wholesale systems, as defined in 

§ 141.2, must comply with the 

requirements of this subpart based on 

the population of the largest system in 

the combined distribution system. 

(2) The requirements of this subpart 

for filtered systems apply to systems 

required by National Primary Drinking 

Water Regulations to provide filtration 

treatment, whether or not the system is 

currently operating a filtration system. 

(3) The requirements of this subpart 

for unfiltered systems apply only to 

unfiltered systems that timely met and 

continue to meet the filtration 

avoidance criteria in subparts H, P, and 

T of this part, as applicable. 

(c) Requirements. Systems subject to 

this subpart must comply with the 

following requirements: 

(1) Systems must conduct an initial 

and a second round of source water 

monitoring for each plant that treats a 

surface water or GWUDI source. This 

monitoring may include sampling for 

Cryptosporidium, E. coli, and turbidity 

as described in §§ 141.701 through 

141.706, to determine what level, if any, 

of additional Cryptosporidium treatment 

they must provide. 

(2) Systems that plan to make a 

significant change to their disinfection 

practice must develop disinfection 

profiles and calculate disinfection 

benchmarks, as described in §§ 141.708 

through 141.709. 

(3) Filtered systems must determine 

their Cryptosporidium treatment bin 

classification as described in § 141.710 

and provide additional treatment for 

Cryptosporidium, if required, as 

described in § 141.711. All unfiltered 

systems must provide treatment for 

Cryptosporidium as described in 

§ 141.712. Filtered and unfiltered 

systems must implement 

Cryptosporidium treatment according to 

the schedule in § 141.713. 


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(4) Systems with uncovered finished 

water storage facilities must comply 

with the requirements to cover the 

facility or treat the discharge from the 

facility as described in § 141.714. 

(5) Systems required to provide 

additional treatment for 

Cryptosporidium must implement 

microbial toolbox options that are 

designed and operated as described in 

§§ 141.715 through 141.720. 

(6) Systems must comply with the 

applicable recordkeeping and reporting 

requirements described in §§ 141.721 

through 141.722. 

(7) Systems must address significant 

deficiencies identified in sanitary 

surveys performed by EPA as described 

in § 141.723. 

Source Water Monitoring Requirements 

§ 141.701 Source water monitoring. 

(a) Initial round of source water 

monitoring. Systems must conduct the 

following monitoring on the schedule in 

paragraph (c) of this section unless they 

meet the monitoring exemption criteria 

in paragraph (d) of this section. 

(1) Filtered systems serving at least 

10,000 people must sample their source 

water for Cryptosporidium, E. coli, and 

turbidity at least monthly for 24 months. 

(2) Unfiltered systems serving at least 

10,000 people must sample their source 

water for Cryptosporidium at least 

monthly for 24 months. 

(3)(i) Filtered systems serving fewer 

than 10,000 people must sample their 

source water for E. coli at least once 

every two weeks for 12 months. 

(ii) A filtered system serving fewer 

than 10,000 people may avoid E. coli 

monitoring if the system notifies the 

State that it will monitor for 

Cryptosporidium as described in 

paragraph (a)(4) of this section. The 

system must notify the State no later 

than 3 months prior to the date the 

system is otherwise required to start E. 

coli monitoring under § 141.701(c). 

(4) Filtered systems serving fewer 

than 10,000 people must sample their 

source water for Cryptosporidium at 

least twice per month for 12 months or 

at least monthly for 24 months if they 

meet one of the following, based on 

monitoring conducted under paragraph 

(a)(3) of this section: 

(i) For systems using lake/reservoir 

sources, the annual mean E. coli 

concentration is greater than 10 E. coli/ 

100 mL. 

(ii) For systems using flowing stream 

sources, the annual mean E. coli 

concentration is greater than 50 E. coli/ 

100 mL. 

(iii) The system does not conduct E. 

coli monitoring as described in 

paragraph (a)(3) of this section. 

(iv) Systems using ground water 

under the direct influence of surface 

water (GWUDI) must comply with the 

requirements of paragraph (a)(4) of this 

section based on the E. coli level that 

applies to the nearest surface water 

body. If no surface water body is nearby, 

the system must comply based on the 

requirements that apply to systems 

using lake/reservoir sources. 

(5) For filtered systems serving fewer 

than 10,000 people, the State may 

approve monitoring for an indicator 

other than E. coli under paragraph (a)(3) 

of this section. The State also may 

approve an alternative to the E. coli 

concentration in paragraph (a)(4)(i), (ii) 

or (iv) of this section to trigger 

Cryptosporidium monitoring. This 

approval by the State must be provided 

to the system in writing and must 

include the basis for the State’s 

determination that the alternative 

indicator and/or trigger level will 

provide a more accurate identification 

of whether a system will exceed the Bin 

1 Cryptosporidium level in § 141.710. 

(6) Unfiltered systems serving fewer 

than 10,000 people must sample their 

source water for Cryptosporidium at 

least twice per month for 12 months or 

at least monthly for 24 months. 

(7) Systems may sample more 

frequently than required under this 

section if the sampling frequency is 

evenly spaced throughout the 

monitoring period. 

(b) Second round of source water 

monitoring. Systems must conduct a 

second round of source water 

monitoring that meets the requirements 

for monitoring parameters, frequency, 

and duration described in paragraph (a) 

of this section, unless they meet the 

monitoring exemption criteria in 

paragraph (d) of this section. Systems 

must conduct this monitoring on the 

schedule in paragraph (c) of this section. 

(c) Monitoring schedule. Systems 

must begin the monitoring required in 

paragraphs (a) and (b) of this section no 

later than the month beginning with the 

date listed in this table: 

SOURCE WATER MONITORING STARTING DATES TABLE

Systems that serve . . . 

Must begin the first round of source water 

monitoring no later than the month 

beginning . . . 

And must begin the second round of source 

water monitoring no later than the month beginning . . . 

(1) At least 100,000 people ................................ (i) October 1, 2006 ........................................... (ii) April 1, 2015. 

(2) From 50,000 to 99,999 people ..................... (i) April 1, 2007 ................................................ (ii) October 1, 2015. 

(3) From 10,000 to 49,999 people ..................... (i) April 1, 2008 ................................................ (ii) October 1, 2016. 

(4) Fewer than 10,000 and monitor for E. coli a (i) October 1, 2008 ........................................... (ii) October 1, 2017. 

(5) Fewer than 10,000 and monitor for 

Cryptosporidium b.

(i) April 1, 2010 ................................................ (ii) April 1, 2019. 

aApplies only to filtered systems. 

bApplies to filtered systems that meet the conditions of paragraph (a)(4) of this section and unfiltered systems. 

(d) Monitoring avoidance. (1) Filtered 

systems are not required to conduct 

source water monitoring under this 

subpart if the system will provide a total 

of at least 5.5-log of treatment for 

Cryptosporidium, equivalent to meeting 

the treatment requirements of Bin 4 in 

§ 141.711. 

(2) Unfiltered systems are not 

required to conduct source water 

monitoring under this subpart if the 

system will provide a total of at least 3- 

log Cryptosporidium inactivation, 

equivalent to meeting the treatment 

requirements for unfiltered systems 

with a mean Cryptosporidium 

concentration of greater than 0.01 

oocysts/L in § 141.712. 

(3) If a system chooses to provide the 

level of treatment in paragraph (d)(1) or 

(2) of this section, as applicable, rather 

than start source water monitoring, the 

system must notify the State in writing 

no later than the date the system is 

otherwise required to submit a sampling 

schedule for monitoring under 

§ 141.702. Alternatively, a system may 

choose to stop sampling at any point 

after it has initiated monitoring if it 

notifies the State in writing that it will 

provide this level of treatment. Systems 

must install and operate technologies to 

provide this level of treatment by the 


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Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules and Regulations 771 

applicable treatment compliance date in 

§ 141.713. 

(e) Plants operating only part of the 

year. Systems with subpart H plants that 

operate for only part of the year must 

conduct source water monitoring in 

accordance with this subpart, but with 

the following modifications: 

(1) Systems must sample their source 

water only during the months that the 

plant operates unless the State specifies 

another monitoring period based on 

plant operating practices. 

(2) Systems with plants that operate 

less than six months per year and that 

monitor for Cryptosporidium must 

collect at least six Cryptosporidium 

samples per year during each of two 

years of monitoring. Samples must be 

evenly spaced throughout the period the 

plant operates. 

(f)(1) New sources. A system that 

begins using a new source of surface 

water or GWUDI after the system is 

required to begin monitoring under 

paragraph (c) of this section must 

monitor the new source on a schedule 

the State approves. Source water 

monitoring must meet the requirements 

of this subpart. The system must also 

meet the bin classification and 

Cryptosporidium treatment 

requirements of §§ 141.710 and 141.711 

or § 141.712, as applicable, for the new 

source on a schedule the State approves. 

(2) The requirements of § 141.701(f) 

apply to subpart H systems that begin 

operation after the monitoring start date 

applicable to the system’s size under 

paragraph (c) of this section. 

(3) The system must begin a second 

round of source water monitoring no 

later than 6 years following initial bin 

classification under § 141.710 or 

determination of the mean 

Cryptosporidium level under § 141.712, 

as applicable. 

(g) Failure to collect any source water 

sample required under this section in 

accordance with the sampling schedule, 

sampling location, analytical method, 

approved laboratory, and reporting 

requirements of §§ 141.702 through 

141.706 is a monitoring violation. 

(h) Grandfathering monitoring data. 

Systems may use (grandfather) 

monitoring data collected prior to the 

applicable monitoring start date in 

paragraph (c) of this section to meet the 

initial source water monitoring 

requirements in paragraph (a) of this 

section. Grandfathered data may 

substitute for an equivalent number of 

months at the end of the monitoring 

period. All data submitted under this 

paragraph must meet the requirements 

in § 141.707. 

§ 141.702 Sampling schedules. 

(a) Systems required to conduct 

source water monitoring under 

§ 141.701 must submit a sampling 

schedule that specifies the calendar 

dates when the system will collect each 

required sample. 

(1) Systems must submit sampling 

schedules no later than 3 months prior 

to the applicable date listed in 

§ 141.701(c) for each round of required 

monitoring. 

(2)(i) Systems serving at least 10,000 

people must submit their sampling 

schedule for the initial round of source 

water monitoring under § 141.701(a) to 

EPA electronically at https:// 

intranet.epa.gov/lt2/. 

(ii) If a system is unable to submit the 

sampling schedule electronically, the 

system may use an alternative approach 

for submitting the sampling schedule 

that EPA approves. 

(3) Systems serving fewer than 10,000 

people must submit their sampling 

schedules for the initial round of source 

water monitoring § 141.701(a) to the 

State. 

(4) Systems must submit sampling 

schedules for the second round of 

source water monitoring § 141.701(b) to 

the State. 

(5) If EPA or the State does not 

respond to a system regarding its 

sampling schedule, the system must 

sample at the reported schedule. 

(b) Systems must collect samples 

within two days before or two days after 

the dates indicated in their sampling 

schedule (i.e., within a five-day period 

around the schedule date) unless one of 

the conditions of paragraph (b)(1) or (2) 

of this section applies. 

(1) If an extreme condition or 

situation exists that may pose danger to 

the sample collector, or that cannot be 

avoided and causes the system to be 

unable to sample in the scheduled fiveday period, the system must sample as 

close to the scheduled date as is feasible 

unless the State approves an alternative 

sampling date. The system must submit 

an explanation for the delayed sampling 

date to the State concurrent with the 

shipment of the sample to the 

laboratory. 

(2)(i) If a system is unable to report a 

valid analytical result for a scheduled 

sampling date due to equipment failure, 

loss of or damage to the sample, failure 

to comply with the analytical method 

requirements, including the quality 

control requirements in § 141.704, or the 

failure of an approved laboratory to 

analyze the sample, then the system 

must collect a replacement sample. 

(ii) The system must collect the 

replacement sample not later than 21 

days after receiving information that an 

analytical result cannot be reported for 

the scheduled date unless the system 

demonstrates that collecting a 

replacement sample within this time 

frame is not feasible or the State 

approves an alternative resampling date. 

The system must submit an explanation 

for the delayed sampling date to the 

State concurrent with the shipment of 

the sample to the laboratory. 

(c) Systems that fail to meet the 

criteria of paragraph (b) of this section 

for any source water sample required 

under § 141.701 must revise their 

sampling schedules to add dates for 

collecting all missed samples. Systems 

must submit the revised schedule to the 

State for approval prior to when the 

system begins collecting the missed 

samples. 

§ 141.703 Sampling locations. 

(a) Systems required to conduct 

source water monitoring under 

§ 141.701 must collect samples for each 

plant that treats a surface water or 

GWUDI source. Where multiple plants 

draw water from the same influent, such 

as the same pipe or intake, the State 

may approve one set of monitoring 

results to be used to satisfy the 

requirements of § 141.701 for all plants. 

(b)(1) Systems must collect source 

water samples prior to chemical 

treatment, such as coagulants, oxidants 

and disinfectants, unless the system 

meets the condition of paragraph (b)(2) 

of this section. 

(2) The State may approve a system to 

collect a source water sample after 

chemical treatment. To grant this 

approval, the State must determine that 

collecting a sample prior to chemical 

treatment is not feasible for the system 

and that the chemical treatment is 

unlikely to have a significant adverse 

effect on the analysis of the sample. 

(c) Systems that recycle filter 

backwash water must collect source 

water samples prior to the point of filter 

backwash water addition. 

(d) Bank filtration. (1) Systems that 

receive Cryptosporidium treatment 

credit for bank filtration under 

§ 141.173(b) or § 141.552(a), as 

applicable, must collect source water 

samples in the surface water prior to 

bank filtration. 

(2) Systems that use bank filtration as 

pretreatment to a filtration plant must 

collect source water samples from the 

well (i.e., after bank filtration). Use of 

bank filtration during monitoring must 

be consistent with routine operational 

practice. Systems collecting samples 

after a bank filtration process may not 

receive treatment credit for the bank 

filtration under § 141.717(c). 


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(e) Multiple sources. Systems with 

plants that use multiple water sources, 

including multiple surface water 

sources and blended surface water and 

ground water sources, must collect 

samples as specified in paragraph (e)(1) 

or (2) of this section. The use of 

multiple sources during monitoring 

must be consistent with routine 

operational practice. 

(1) If a sampling tap is available 

where the sources are combined prior to 

treatment, systems must collect samples 

from the tap. 

(2) If a sampling tap where the 

sources are combined prior to treatment 

is not available, systems must collect 

samples at each source near the intake 

on the same day and must follow either 

paragraph (e)(2)(i) or (ii) of this section 

for sample analysis. 

(i) Systems may composite samples 

from each source into one sample prior 

to analysis. The volume of sample from 

each source must be weighted according 

to the proportion of the source in the 

total plant flow at the time the sample 

is collected. 

(ii) Systems may analyze samples 

from each source separately and 

calculate a weighted average of the 

analysis results for each sampling date. 

The weighted average must be 

calculated by multiplying the analysis 

result for each source by the fraction the 

source contributed to total plant flow at 

the time the sample was collected and 

then summing these values. 

(f) Additional Requirements. Systems 

must submit a description of their 

sampling location(s) to the State at the 

same time as the sampling schedule 

required under § 141.702. This 

description must address the position of 

the sampling location in relation to the 

system’s water source(s) and treatment 

processes, including pretreatment, 

points of chemical treatment, and filter 

backwash recycle. If the State does not 

respond to a system regarding sampling 

location(s), the system must sample at 

the reported location(s). 

§ 141.704 Analytical methods. 

(a) Cryptosporidium. Systems must 

analyze for Cryptosporidium using 

Method 1623: Cryptosporidium and 

Giardia in Water by Filtration/IMS/FA, 

2005, United States Environmental 

Protection Agency, EPA–815-R–05–002 

or Method 1622: Cryptosporidium in 

Water by Filtration/IMS/FA, 2005, 

United States Environmental Protection 

Agency, EPA–815–R–05–001, which 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. You may obtain a copy of 

these methods online from http:// 

www.epa.gov/safewater/disinfection/lt2 

or from the United States Environmental 

Protection Agency, Office of Ground 

Water and Drinking Water, 1201 

Constitution Ave., NW, Washington, DC 

20460 (Telephone: 800–426–4791). You 

may inspect a copy at the Water Docket 

in the EPA Docket Center, 1301 

Constitution Ave., NW, Washington, 

DC, (Telephone: 202–566–2426) 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. 

(1) Systems must analyze at least a 10 

L sample or a packed pellet volume of 

at least 2 mL as generated by the 

methods listed in paragraph (a) of this 

section. Systems unable to process a 10 

L sample must analyze as much sample 

volume as can be filtered by two filters 

approved by EPA for the methods listed 

in paragraph (a) of this section, up to a 

packed pellet volume of at least 2 mL. 

(2)(i) Matrix spike (MS) samples, as 

required by the methods in paragraph 

(a) of this section, must be spiked and 

filtered by a laboratory approved for 

Cryptosporidium analysis under 

§ 141.705. 

(ii) If the volume of the MS sample is 

greater than 10 L, the system may filter 

all but 10 L of the MS sample in the 

field, and ship the filtered sample and 

the remaining 10 L of source water to 

the laboratory. In this case, the 

laboratory must spike the remaining 10 

L of water and filter it through the filter 

used to collect the balance of the sample 

in the field. 

(3) Flow cytometer-counted spiking 

suspensions must be used for MS 

samples and ongoing precision and 

recovery (OPR) samples. 

(b) E. coli. Systems must use methods 

for enumeration of E. coli in source 

water approved in § 136.3(a) of this title. 

(1) The time from sample collection to 

initiation of analysis may not exceed 30 

hours unless the system meets the 

condition of paragraph (b)(2) of this 

section. 

(2) The State may approve on a caseby-case basis the holding of an E. coli 

sample for up to 48 hours between 

sample collection and initiation of 

analysis if the State determines that 

analyzing an E. coli sample within 30 

hours is not feasible. E. coli samples 

held between 30 to 48 hours must be 

analyzed by the Colilert reagent version 

of Standard Method 9223B as listed in 

§ 136.3(a) of this title. 

(3) Systems must maintain samples 

between 0°C and 10°C during storage 

and transit to the laboratory. 

(c) Turbidity. Systems must use 

methods for turbidity measurement 

approved in § 141.74(a)(1). 

§ 141.705 Approved laboratories. 

(a) Cryptosporidium. Systems must 

have Cryptosporidium samples analyzed 

by a laboratory that is approved under 

EPA’s Laboratory Quality Assurance 

Evaluation Program for Analysis of 

Cryptosporidium in Water or a 

laboratory that has been certified for 

Cryptosporidium analysis by an 

equivalent State laboratory certification 

program. 

(b) E. coli. Any laboratory certified by 

the EPA, the National Environmental 

Laboratory Accreditation Conference or 

the State for total coliform or fecal 

coliform analysis under § 141.74 is 

approved for E. coli analysis under this 

subpart when the laboratory uses the 

same technique for E. coli that the 

laboratory uses for § 141.74. 

(c) Turbidity. Measurements of 

turbidity must be made by a party 

approved by the State. 

§ 141.706 Reporting source water 

monitoring results. 

(a) Systems must report results from 

the source water monitoring required 

under § 141.701 no later than 10 days 

after the end of the first month 

following the month when the sample is 

collected. 

(b)(1) All systems serving at least 

10,000 people must report the results 

from the initial source water monitoring 

required under § 141.701(a) to EPA 

electronically at https:// 

intranet.epa.gov/lt2/. 

(2) If a system is unable to report 

monitoring results electronically, the 

system may use an alternative approach 

for reporting monitoring results that 

EPA approves. 

(c) Systems serving fewer than 10,000 

people must report results from the 

initial source water monitoring required 

under § 141.701(a) to the State. 

(d) All systems must report results 

from the second round of source water 

monitoring required under § 141.701(b) 

to the State. 

(e) Systems must report the applicable 

information in paragraphs (e)(1) and (2) 

of this section for the source water 

monitoring required under § 141.701. 

(1) Systems must report the following 

data elements for each Cryptosporidium 

analysis: 

Data element. 

1. PWS ID. 

2. Facility ID. 


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Data element. 

3. Sample collection date. 

4. Sample type (field or matrix spike). 

5. Sample volume filtered (L), to nearest 1⁄4

L. 

6. Was 100% of filtered volume examined. 

7. Number of oocysts counted. 

(i) For matrix spike samples, systems 

must also report the sample volume 

spiked and estimated number of oocysts 

spiked. These data are not required for 

field samples. 

(ii) For samples in which less than 10 

L is filtered or less than 100% of the 

sample volume is examined, systems 

must also report the number of filters 

used and the packed pellet volume. 

(iii) For samples in which less than 

100% of sample volume is examined, 

systems must also report the volume of 

resuspended concentrate and volume of 

this resuspension processed through 

immunomagnetic separation. 

(2) Systems must report the following 

data elements for each E. coli analysis: 

Data element. 

1. PWS ID. 

2. Facility ID. 

3. Sample collection date. 

4. Analytical method number. 

5. Method type. 

6. Source type (flowing stream, lake/reservoir, 

GWUDI). 

7. E. coli/100 mL. 

8. Turbidity.1

1Systems serving fewer than 10,000 people 

that are not required to monitor for turbidity 

under § 141.701 are not required to report 

turbidity with their E. coli results. 

§ 141.707 Grandfathering previously 

collected data. 

(a)(1) Systems may comply with the 

initial source water monitoring 

requirements of § 141.701(a) by 

grandfathering sample results collected 

before the system is required to begin 

monitoring (i.e., previously collected 

data). To be grandfathered, the sample 

results and analysis must meet the 

criteria in this section and the State 

must approve. 

(2) A filtered system may grandfather 

Cryptosporidium samples to meet the 

requirements of § 141.701(a) when the 

system does not have corresponding E. 

coli and turbidity samples. A system 

that grandfathers Cryptosporidium 

samples without E. coli and turbidity 

samples is not required to collect E. coli 

and turbidity samples when the system 

completes the requirements for 

Cryptosporidium monitoring under 

§ 141.701(a). 

(b) E. coli sample analysis. The 

analysis of E. coli samples must meet 

the analytical method and approved 

laboratory requirements of §§ 141.704 

through 141.705. 

(c) Cryptosporidium sample analysis. 

The analysis of Cryptosporidium 

samples must meet the criteria in this 

paragraph. 

(1) Laboratories analyzed 

Cryptosporidium samples using one of 

the analytical methods in paragraphs 

(c)(1)(i) through (vi) of this section, 

which 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. You may obtain a copy 

of these methods on-line from the 

United States Environmental Protection 

Agency, Office of Ground Water and 

Drinking Water, 1201 Constitution Ave, 

NW, Washington, DC 20460 (Telephone: 

800–426–4791). You may inspect a copy 

at the Water Docket in the EPA Docket 

Center, 1301 Constitution Ave., NW, 

Washington, DC, (Telephone: 202–566– 

2426) 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. 

(i) Method 1623: Cryptosporidium 

and Giardia in Water by Filtration/IMS/ 

FA, 2005, United States Environmental 

Protection Agency, EPA–815–R–05–002. 

(ii) Method 1622: Cryptosporidium in 

Water by Filtration/IMS/FA, 2005, 

United States Environmental Protection 

Agency, EPA–815–R–05–001. 

(iii) Method 1623: Cryptosporidium 

and Giardia in Water by Filtration/IMS/ 

FA, 2001, United States Environmental 

Protection Agency, EPA–821–R–01–025. 

(iv) Method 1622: Cryptosporidium in 

Water by Filtration/IMS/FA, 2001, 

United States Environmental Protection 

Agency, EPA–821–-R–01–026. 

(v) Method 1623: Cryptosporidium 

and Giardia in Water by Filtration/IMS/ 

FA, 1999, United States Environmental 

Protection Agency, EPA–821–R–99–006. 

(vi) Method 1622: Cryptosporidium in 

Water by Filtration/IMS/FA, 1999, 

United States Environmental Protection 

Agency, EPA–821–R–99–001. 

(2) For each Cryptosporidium sample, 

the laboratory analyzed at least 10 L of 

sample or at least 2 mL of packed pellet 

or as much volume as could be filtered 

by 2 filters that EPA approved for the 

methods listed in paragraph (c)(1) of 

this section. 

(d) Sampling location. The sampling 

location must meet the conditions in 

§ 141.703. 

(e) Sampling frequency. 

Cryptosporidium samples were 

collected no less frequently than each 

calendar month on a regular schedule, 

beginning no earlier than January 1999. 

Sample collection intervals may vary for 

the conditions specified in 

§ 141.702(b)(1) and (2) if the system 

provides documentation of the 

condition when reporting monitoring 

results. 

(1) The State may approve 

grandfathering of previously collected 

data where there are time gaps in the 

sampling frequency if the system 

conducts additional monitoring the 

State specifies to ensure that the data 

used to comply with the initial source 

water monitoring requirements of 

§ 141.701(a) are seasonally 

representative and unbiased. 

(2) Systems may grandfather 

previously collected data where the 

sampling frequency within each month 

varied. If the Cryptosporidium sampling 

frequency varied, systems must follow 

the monthly averaging procedure in 

§ 141.710(b)(5) or § 141.712(a)(3), as 

applicable, when calculating the bin 

classification for filtered systems or the 

mean Cryptosporidium concentration 

for unfiltered systems. 

(f) Reporting monitoring results for 

grandfathering. Systems that request to 

grandfather previously collected 

monitoring results must report the 

following information by the applicable 

dates listed in this paragraph. Systems 

serving at least 10,000 people must 

report this information to EPA unless 

the State approves reporting to the State 

rather than EPA. Systems serving fewer 

than 10,000 people must report this 

information to the State. 

(1) Systems must report that they 

intend to submit previously collected 

monitoring results for grandfathering. 

This report must specify the number of 

previously collected results the system 

will submit, the dates of the first and 

last sample, and whether a system will 

conduct additional source water 

monitoring to meet the requirements of 

§ 141.701(a). Systems must report this 

information no later than the date the 

sampling schedule under § 141.702 is 

required. 

(2) Systems must report previously 

collected monitoring results for 

grandfathering, along with the 

associated documentation listed in 

paragraphs (f)(2)(i) through (iv) of this 

section, no later than two months after 

the applicable date listed in 

§ 141.701(c). 

(i) For each sample result, systems 

must report the applicable data 

elements in § 141.706. 

(ii) Systems must certify that the 

reported monitoring results include all 

results the system generated during the 

time period beginning with the first 

reported result and ending with the 

final reported result. This applies to 

samples that were collected from the 


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sampling location specified for source 

water monitoring under this subpart, 

not spiked, and analyzed using the 

laboratory’s routine process for the 

analytical methods listed in this section. 

(iii) Systems must certify that the 

samples were representative of a plant’s 

source water(s) and the source water(s) 

have not changed. Systems must report 

a description of the sampling 

location(s), which must address the 

position of the sampling location in 

relation to the system’s water source(s) 

and treatment processes, including 

points of chemical addition and filter 

backwash recycle. 

(iv) For Cryptosporidium samples, the 

laboratory or laboratories that analyzed 

the samples must provide a letter 

certifying that the quality control 

criteria specified in the methods listed 

in paragraph (c)(1) of this section were 

met for each sample batch associated 

with the reported results. Alternatively, 

the laboratory may provide bench sheets 

and sample examination report forms 

for each field, matrix spike, IPR, OPR, 

and method blank sample associated 

with the reported results. 

(g) If the State determines that a 

previously collected data set submitted 

for grandfathering was generated during 

source water conditions that were not 

normal for the system, such as a 

drought, the State may disapprove the 

data. Alternatively, the State may 

approve the previously collected data if 

the system reports additional source 

water monitoring data, as determined by 

the State, to ensure that the data set 

used under § 141.710 or § 141.712 

represents average source water 

conditions for the system. 

(h) If a system submits previously 

collected data that fully meet the 

number of samples required for initial 

source water monitoring under 

§ 141.701(a) and some of the data are 

rejected due to not meeting the 

requirements of this section, systems 

must conduct additional monitoring to 

replace rejected data on a schedule the 

State approves. Systems are not required 

to begin this additional monitoring until 

two months after notification that data 

have been rejected and additional 

monitoring is necessary. 

Disinfection Profiling and 

Benchmarking Requirements 

§ 141.708 Requirements when making a 

significant change in disinfection practice. 

(a) Following the completion of initial 

source water monitoring under 

§ 141.701(a), a system that plans to 

make a significant change to its 

disinfection practice, as defined in 

paragraph (b) of this section, must 

develop disinfection profiles and 

calculate disinfection benchmarks for 

Giardia lamblia and viruses as 

described in § 141.709. Prior to 

changing the disinfection practice, the 

system must notify the State and must 

include in this notice the information in 

paragraphs (a)(1) through (3) of this 

section. 

(1) A completed disinfection profile 

and disinfection benchmark for Giardia 

lamblia and viruses as described in 

§ 141.709. 

(2) A description of the proposed 

change in disinfection practice. 

(3) An analysis of how the proposed 

change will affect the current level of 

disinfection. 

(b) Significant changes to disinfection 

practice are defined as follows: 

(1) Changes to the point of 

disinfection; 

(2) Changes to the disinfectant(s) used 

in the treatment plant; 

(3) Changes to the disinfection 

process; or 

(4) Any other modification identified 

by the State as a significant change to 

disinfection practice. 

§ 141.709 Developing the disinfection 

profile and benchmark. 

(a) Systems required to develop 

disinfection profiles under § 141.708 

must follow the requirements of this 

section. Systems must monitor at least 

weekly for a period of 12 consecutive 

months to determine the total log 

inactivation for Giardia lamblia and 

viruses. If systems monitor more 

frequently, the monitoring frequency 

must be evenly spaced. Systems that 

operate for fewer than 12 months per 

year must monitor weekly during the 

period of operation. Systems must 

determine log inactivation for Giardia 

lamblia through the entire plant, based 

on CT99.9 values in Tables 1.1 through 

1.6, 2.1 and 3.1 of § 141.74(b) as 

applicable. Systems must determine log 

inactivation for viruses through the 

entire treatment plant based on a 

protocol approved by the State. 

(b) Systems with a single point of 

disinfectant application prior to the 

entrance to the distribution system must 

conduct the monitoring in paragraphs 

(b)(1) through (4) of this section. 

Systems with more than one point of 

disinfectant application must conduct 

the monitoring in paragraphs (b)(1) 

through (4) of this section for each 

disinfection segment. Systems must 

monitor the parameters necessary to 

determine the total inactivation ratio, 

using analytical methods in § 141.74(a). 

(1) For systems using a disinfectant 

other than UV, the temperature of the 

disinfected water must be measured at 

each residual disinfectant concentration 

sampling point during peak hourly flow 

or at an alternative location approved by 

the State. 

(2) For systems using chlorine, the pH 

of the disinfected water must be 

measured at each chlorine residual 

disinfectant concentration sampling 

point during peak hourly flow or at an 

alternative location approved by the 

State. 

(3) The disinfectant contact time(s) (t) 

must be determined during peak hourly 

flow. 

(4) The residual disinfectant 

concentration(s) (C) of the water before 

or at the first customer and prior to each 

additional point of disinfectant 

application must be measured during 

peak hourly flow. 

(c) In lieu of conducting new 

monitoring under paragraph (b) of this 

section, systems may elect to meet the 

requirements of paragraphs (c)(1) or (2) 

of this section. 

(1) Systems that have at least one year 

of existing data that are substantially 

equivalent to data collected under the 

provisions of paragraph (b) of this 

section may use these data to develop 

disinfection profiles as specified in this 

section if the system has neither made 

a significant change to its treatment 

practice nor changed sources since the 

data were collected. Systems may 

develop disinfection profiles using up to 

three years of existing data. 

(2) Systems may use disinfection 

profile(s) developed under § 141.172 or 

§§ 141.530 through 141.536 in lieu of 

developing a new profile if the system 

has neither made a significant change to 

its treatment practice nor changed 

sources since the profile was developed. 

Systems that have not developed a virus 

profile under § 141.172 or §§ 141.530 

through 141.536 must develop a virus 

profile using the same monitoring data 

on which the Giardia lamblia profile is 

based. 

(d) Systems must calculate the total 

inactivation ratio for Giardia lamblia as 

specified in paragraphs (d)(1) through 

(3) of this section. 

(1) Systems using only one point of 

disinfectant application may determine 

the total inactivation ratio for the 

disinfection segment based on either of 

the methods in paragraph (d)(1)(i) or (ii) 

of this section. 

(i) Determine one inactivation ratio 

(CTcalc/CT99.9) before or at the first 

customer during peak hourly flow. 

(ii) Determine successive CTcalc/ 

CT99.9 values, representing sequential 

inactivation ratios, between the point of 

disinfectant application and a point 

before or at the first customer during 

peak hourly flow. The system must 


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calculate the total inactivation ratio by 

determining (CTcalc/CT99.9) for each 

sequence and then adding the (CTcalc/ 

CT99.9) values together to determine (S 

(CTcalc/CT99.9)). 

(2) Systems using more than one point 

of disinfectant application before the 

first customer must determine the CT 

value of each disinfection segment 

immediately prior to the next point of 

disinfectant application, or for the final 

segment, before or at the first customer, 

during peak hourly flow. The (CTcalc/ 

CT99.9) value of each segment and (S 

(CTcalc/CT99.9)) must be calculated 

using the method in paragraph (d)(1)(ii) 

of this section. 

(3) The system must determine the 

total logs of inactivation by multiplying 

the value calculated in paragraph (d)(1) 

or (d)(2) of this section by 3.0. 

(4) Systems must calculate the log of 

inactivation for viruses using a protocol 

approved by the State. 

(e) Systems must use the procedures 

specified in paragraphs (e)(1) and (2) of 

this section to calculate a disinfection 

benchmark. 

(1) For each year of profiling data 

collected and calculated under 

paragraphs (a) through (d) of this 

section, systems must determine the 

lowest mean monthly level of both 

Giardia lamblia and virus inactivation. 

Systems must determine the mean 

Giardia lamblia and virus inactivation 

for each calendar month for each year of 

profiling data by dividing the sum of 

daily or weekly Giardia lamblia and 

virus log inactivation by the number of 

values calculated for that month. 

(2) The disinfection benchmark is the 

lowest monthly mean value (for systems 

with one year of profiling data) or the 

mean of the lowest monthly mean 

values (for systems with more than one 

year of profiling data) of Giardia lamblia 

and virus log inactivation in each year 

of profiling data. 

Treatment Technique Requirements 

§ 141.710 Bin classification for filtered 

systems. 

(a) Following completion of the initial 

round of source water monitoring 

required under § 141.701(a), filtered 

systems must calculate an initial 

Cryptosporidium bin concentration for 

each plant for which monitoring was 

required. Calculation of the bin 

concentration must use the 

Cryptosporidium results reported under 

§ 141.701(a) and must follow the 

procedures in paragraphs (b)(1) through 

(5) of this section. 

(b)(1) For systems that collect a total 

of at least 48 samples, the bin 

concentration is equal to the arithmetic 

mean of all sample concentrations. 

(2) For systems that collect a total of 

at least 24 samples, but not more than 

47 samples, the bin concentration is 

equal to the highest arithmetic mean of 

all sample concentrations in any 12 

consecutive months during which 

Cryptosporidium samples were 

collected. 

(3) For systems that serve fewer than 

10,000 people and monitor for 

Cryptosporidium for only one year (i.e., 

collect 24 samples in 12 months), the 

bin concentration is equal to the 

arithmetic mean of all sample 

concentrations. 

(4) For systems with plants operating 

only part of the year that monitor fewer 

than 12 months per year under 

§ 141.701(e), the bin concentration is 

equal to the highest arithmetic mean of 

all sample concentrations during any 

year of Cryptosporidium monitoring. 

(5) If the monthly Cryptosporidium 

sampling frequency varies, systems 

must first calculate a monthly average 

for each month of monitoring. Systems 

must then use these monthly average 

concentrations, rather than individual 

sample concentrations, in the applicable 

calculation for bin classification in 

paragraphs (b)(1) through (4) of this 

section. 

(c) Filtered systems must determine 

their initial bin classification from the 

following table and using the 

Cryptosporidium bin concentration 

calculated under paragraphs (a)–(b) of 

this section: 

BIN CLASSIFICATION TABLE FOR FILTERED SYSTEMS

For systems that are: With a Cryptosporidium bin concentration of . . .1 The bin classification is . . . 

. . . required to monitor for Cryptosporidium under 

§ 141.701.

Cryptosporidium <0.075 oocyst/L ............................. Bin 1. 

0.075 oocysts/L ≤Cryptosporidium <1.0 oocysts/L Bin 2. 

1.0 oocysts/L ≤Cryptosporidium <3.0 oocysts/L ... Bin 3. 

Cryptosporidium ≥3.0 oocysts/L ............................ Bin 4. 

. . . serving fewer than 10,000 people and NOT required 

to monitor for Cryptosporidium under § 141.701(a)(4).

NA ............................................................................. Bin 1. 

1Based on calculations in paragraph (a) or (d) of this section, as applicable. 

(d) Following completion of the 

second round of source water 

monitoring required under § 141.701(b), 

filtered systems must recalculate their 

Cryptosporidium bin concentration 

using the Cryptosporidium results 

reported under § 141.701(b) and 

following the procedures in paragraphs 

(b)(1) through (4) of this section. 

Systems must then redetermine their 

bin classification using this bin 

concentration and the table in paragraph 

(c) of this section. 

(e)(1) Filtered systems must report 

their initial bin classification under 

paragraph (c) of this section to the State 

for approval no later than 6 months after 

the system is required to complete 

initial source water monitoring based on 

the schedule in § 141.701(c). 

(2) Systems must report their bin 

classification under paragraph (d) of this 

section to the State for approval no later 

than 6 months after the system is 

required to complete the second round 

of source water monitoring based on the 

schedule in § 141.701(c). 

(3) The bin classification report to the 

State must include a summary of source 

water monitoring data and the 

calculation procedure used to determine 

bin classification. 

(f) Failure to comply with the 

conditions of paragraph (e) of this 

section is a violation of the treatment 

technique requirement. 

§ 141.711 Filtered system additional 

Cryptosporidium treatment requirements. 

(a) Filtered systems must provide the 

level of additional treatment for 

Cryptosporidium specified in this 

paragraph based on their bin 

classification as determined under 

§ 141.710 and according to the schedule 

in § 141.713. 


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If the system 

bin classification is . . . 

And the system uses the following filtration treatment in full compliance with subparts H, P, and T of this part (as applicable), 

then the additional Cryptosporidium treatment requirements are . . . 

Conventional filtration treatment 

(including softening) 

Direct filtration Slow sand or diatomaceous 

earth filtration 

Alternative filtration technologies 

Bin 1 ............. No additional treatment .......... No additional treatment .......... No additional treatment .......... No additional treatment. 

Bin 2 ............. 1-log treatment ....................... 1.5-log treatment .................... 1-log treatment ....................... (1) 

Bin 3 ............. 2-log treatment ....................... 2.5-log treatment .................... 2-log treatment ....................... (2) 

Bin 4 ............. 2.5-log treatment .................... 3-log treatment ....................... 2.5-log treatment .................... (3) 

1 As determined by the State such that the total Cryptosporidium removal and inactivation is at least 4.0-log. 2 As determined by the State such that the total Cryptosporidium removal and inactivation is at least 5.0-log. 3 As determined by the State such that the total Cryptosporidium removal and inactivation is at least 5.5-log. 

(b)(1) Filtered systems must use one 

or more of the treatment and 

management options listed in § 141.715, 

termed the microbial toolbox, to comply 

with the additional Cryptosporidium 

treatment required in paragraph (a) of 

this section. 

(2) Systems classified in Bin 3 and 

Bin 4 must achieve at least 1-log of the 

additional Cryptosporidium treatment 

required under paragraph (a) of this 

section using either one or a 

combination of the following: bag filters, 

bank filtration, cartridge filters, chlorine 

dioxide, membranes, ozone, or UV, as 

described in §§ 141.716 through 

141.720. 

(c) Failure by a system in any month 

to achieve treatment credit by meeting 

criteria in §§ 141.716 through 141.720 

for microbial toolbox options that is at 

least equal to the level of treatment 

required in paragraph (a) of this section 

is a violation of the treatment technique 

requirement. 

(d) If the State determines during a 

sanitary survey or an equivalent source 

water assessment that after a system 

completed the monitoring conducted 

under § 141.701(a) or § 141.701(b), 

significant changes occurred in the 

system’s watershed that could lead to 

increased contamination of the source 

water by Cryptosporidium, the system 

must take actions specified by the State 

to address the contamination. These 

actions may include additional source 

water monitoring and/or implementing 

microbial toolbox options listed in 

§ 141.715. 

§ 141.712 Unfiltered system 

Cryptosporidium treatment requirements. 

(a) Determination of mean 

Cryptosporidium level. (1) Following 

completion of the initial source water 

monitoring required under § 141.701(a), 

unfiltered systems must calculate the 

arithmetic mean of all Cryptosporidium 

sample concentrations reported under 

§ 141.701(a). Systems must report this 

value to the State for approval no later 

than 6 months after the month the 

system is required to complete initial 

source water monitoring based on the 

schedule in § 141.701(c). 

(2) Following completion of the 

second round of source water 

monitoring required under § 141.701(b), 

unfiltered systems must calculate the 

arithmetic mean of all Cryptosporidium 

sample concentrations reported under 

§ 141.701(b). Systems must report this 

value to the State for approval no later 

than 6 months after the month the 

system is required to complete the 

second round of source water 

monitoring based on the schedule in 

§ 141.701(c). 

(3) If the monthly Cryptosporidium 

sampling frequency varies, systems 

must first calculate a monthly average 

for each month of monitoring. Systems 

must then use these monthly average 

concentrations, rather than individual 

sample concentrations, in the 

calculation of the mean 

Cryptosporidium level in paragraphs 

(a)(1) or (2) of this section. 

(4) The report to the State of the mean 

Cryptosporidium levels calculated 

under paragraphs (a)(1) and (2) of this 

section must include a summary of the 

source water monitoring data used for 

the calculation. 

(5) Failure to comply with the 

conditions of paragraph (a) of this 

section is a violation of the treatment 

technique requirement. 

(b) Cryptosporidium inactivation 

requirements. Unfiltered systems must 

provide the level of inactivation for 

Cryptosporidium specified in this 

paragraph, based on their mean 

Cryptosporidium levels as determined 

under paragraph (a) of this section and 

according to the schedule in § 141.713. 

(1) Unfiltered systems with a mean 

Cryptosporidium level of 0.01 oocysts/L 

or less must provide at least 2-log 

Cryptosporidium inactivation. 

(2) Unfiltered systems with a mean 

Cryptosporidium level of greater than 

0.01 oocysts/L must provide at least 3- 

log Cryptosporidium inactivation. 

(c) Inactivation treatment technology 

requirements. Unfiltered systems must 

use chlorine dioxide, ozone, or UV as 

described in § 141.720 to meet the 

Cryptosporidium inactivation 

requirements of this section. 

(1) Systems that use chlorine dioxide 

or ozone and fail to achieve the 

Cryptosporidium inactivation required 

in paragraph (b) of this section on more 

than one day in the calendar month are 

in violation of the treatment technique 

requirement. 

(2) Systems that use UV light and fail 

to achieve the Cryptosporidium 

inactivation required in paragraph (b) of 

this section by meeting the criteria in 

§ 141.720(d)(3)(ii) are in violation of the 

treatment technique requirement. 

(d) Use of two disinfectants. 

Unfiltered systems must meet the 

combined Cryptosporidium inactivation 

requirements of this section and Giardia 

lamblia and virus inactivation 

requirements of § 141.72(a) using a 

minimum of two disinfectants, and each 

of two disinfectants must separately 

achieve the total inactivation required 

for either Cryptosporidium, Giardia 

lamblia, or viruses. 

§ 141.713 Schedule for compliance with 

Cryptosporidium treatment requirements. 

(a) Following initial bin classification 

under § 141.710(c), filtered systems 

must provide the level of treatment for 

Cryptosporidium required under 

§ 141.711 according to the schedule in 

paragraph (c) of this section. 

(b) Following initial determination of 

the mean Cryptosporidium level under 

§ 141.712(a)(1), unfiltered systems must 

provide the level of treatment for 

Cryptosporidium required under 

§ 141.712 according to the schedule in 

paragraph (c) of this section. 

(c) Cryptosporidium treatment 

compliance dates. 


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Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules and Regulations 777 

CRYPTOSPORIDIUM TREATMENT

COMPLIANCE DATES TABLE

Systems that serve 

. . . 

Must comply with 

Cryptosporidium treatment requirements no 

later than . . . a

(1) At least 100,000 

people.

(i) April 1, 2012. 

(2) From 50,000 to 

99,999 people.

(i) October 1, 2012. 

(3) From 10,000 to 

49,999 people.

(i) October 1, 2013. 

(4) Fewer than 

10,000 people.

(i) October 1, 2014. 

aStates may allow up to an additional two 

years for complying with the treatment requirement for systems making capital 

improvements. 

(d) If the bin classification for a 

filtered system changes following the 

second round of source water 

monitoring, as determined under 

§ 141.710(d), the system must provide 

the level of treatment for 

Cryptosporidium required under 

§ 141.711 on a schedule the State 

approves. 

(e) If the mean Cryptosporidium level 

for an unfiltered system changes 

following the second round of 

monitoring, as determined under 

§ 141.712(a)(2), and if the system must 

provide a different level of 

Cryptosporidium treatment under 

§ 141.712 due to this change, the system 

must meet this treatment requirement 

on a schedule the State approves. 

§ 141.714 Requirements for uncovered 

finished water storage facilities. 

(a) Systems using uncovered finished 

water storage facilities must comply 

with the conditions of this section. 

(b) Systems must notify the State of 

the use of each uncovered finished 

water storage facility no later than April 

1, 2008. 

(c) Systems must meet the conditions 

of paragraph (c)(1) or (2) of this section 

for each uncovered finished water 

storage facility or be in compliance with 

a State-approved schedule to meet these 

conditions no later than April 1, 2009. 

(1) Systems must cover any uncovered 

finished water storage facility. 

(2) Systems must treat the discharge 

from the uncovered finished water 

storage facility to the distribution 

system to achieve inactivation and/or 

removal of at least 4-log virus, 3-log 

Giardia lamblia, and 2-log 

Cryptosporidium using a protocol 

approved by the State. 

(d) Failure to comply with the 

requirements of this section is a 

violation of the treatment technique 

requirement. 

Requirements for Microbial Toolbox 

Components 

§ 141.715 Microbial toolbox options for 

meeting Cryptosporidium treatment 

requirements. 

(a)(1) Systems receive the treatment 

credits listed in the table in paragraph 

(b) of this section by meeting the 

conditions for microbial toolbox options 

described in §§ 141.716 through 

141.720. Systems apply these treatment 

credits to meet the treatment 

requirements in § 141.711 or § 141.712, 

as applicable. 

(2) Unfiltered systems are eligible for 

treatment credits for the microbial 

toolbox options described in § 141.720 

only. 

(b) The following table summarizes 

options in the microbial toolbox: 

MICROBIAL TOOLBOX SUMMARY TABLE: OPTIONS, TREATMENT CREDITS AND CRITERIA

Toolbox Option Cryptosporidium treatment credit with design and implementation criteria 

Source Protection and Management Toolbox Options 

(1) Watershed control program .......................... 0.5-log credit for State-approved program comprising required elements, annual program status report to State, and regular watershed survey. Unfiltered systems are not eligible for 

credit. Specific criteria are in § 141.716(a). 

(2) Alternative source/intake management ......... No prescribed credit. Systems may conduct simultaneous monitoring for treatment bin classification at alternative intake locations or under alternative intake management strategies. 

Specific criteria are in § 141.716(b). 

Pre Filtration Toolbox Options 

(3) Presedimentation basin with coagulation ..... 0.5-log credit during any month that presedimentation basins achieve a monthly mean reduction of 0.5-log or greater in turbidity or alternative State-approved performance criteria. To 

be eligible, basins must be operated continuously with coagulant addition and all plant flow 

must pass through basins. Specific criteria are in § 141.717(a). 

(4) Two-stage lime softening .............................. 0.5-log credit for two-stage softening where chemical addition and hardness precipitation occur 

in both stages. All plant flow must pass through both stages. Single-stage softening is credited as equivalent to conventional treatment. Specific criteria are in § 141.717(b). 

(5) Bank filtration ................................................ 0.5-log credit for 25-foot setback; 1.0-log credit for 50-foot setback; aquifer must be unconsolidated sand containing at least 10 percent fines; average turbidity in wells must be less than 

1 NTU. Systems using wells followed by filtration when conducting source water monitoring 

must sample the well to determine bin classification and are not eligible for additional credit. 

Specific criteria are in § 141.717(c). 

Treatment Performance Toolbox Options 

(6) Combined filter performance ......................... 0.5-log credit for combined filter effluent turbidity less than or equal to 0.15 NTU in at least 95 

percent of measurements each month. Specific criteria are in § 141.718(a). 

(7) Individual filter performance .......................... 0.5-log credit (in addition to 0.5-log combined filter performance credit) if individual filter effluent turbidity is less than or equal to 0.15 NTU in at least 95 percent of samples each month 

in each filter and is never greater than 0.3 NTU in two consecutive measurements in any filter. Specific criteria are in § 141.718(b). 

(8) Demonstration of performance ..................... Credit awarded to unit process or treatment train based on a demonstration to the State with a 

State- approved protocol. Specific criteria are in § 141.718(c). 


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MICROBIAL TOOLBOX SUMMARY TABLE: OPTIONS, TREATMENT CREDITS AND CRITERIA—Continued 

Toolbox Option Cryptosporidium treatment credit with design and implementation criteria 

Additional Filtration Toolbox Options 

(9) Bag or cartridge filters (individual filters) ...... Up to 2-log credit based on the removal efficiency demonstrated during challenge testing with 

a 1.0-log factor of safety. Specific criteria are in § 141.719(a). 

(10) Bag or cartridge filters (in series) ............... Up to 2.5-log credit based on the removal efficiency demonstrated during challenge testing 

with a 0.5-log factor of safety. Specific criteria are in § 141.719(a). 

(11) Membrane filtration ..................................... Log credit equivalent to removal efficiency demonstrated in challenge test for device if supported by direct integrity testing. Specific criteria are in § 141.719(b). 

(12) Second stage filtration ................................ 0.5-log credit for second separate granular media filtration stage if treatment train includes coagulation prior to first filter. Specific criteria are in § 141.719(c) 

(13) Slow sand filters .......................................... 2.5-log credit as a secondary filtration step; 3.0-log credit as a primary filtration process. No 

prior chlorination for either option. Specific criteria are in § 141.719(d). 

Inactivation Toolbox Options 

(14) Chlorine dioxide .......................................... Log credit based on measured CT in relation to CT table. Specific criteria in § 141.720(b) 

(15) Ozone .......................................................... Log credit based on measured CT in relation to CT table. Specific criteria in § 141.720(b). 

(16) UV ............................................................... Log credit based on validated UV dose in relation to UV dose table; reactor validation testing 

required to establish UV dose and associated operating conditions. Specific criteria in 

§ 141.720(d). 

§ 141.716 Source toolbox components. 

(a) Watershed control program. 

Systems receive 0.5-log 

Cryptosporidium treatment credit for 

implementing a watershed control 

program that meets the requirements of 

this section. 

(1) Systems that intend to apply for 

the watershed control program credit 

must notify the State of this intent no 

later than two years prior to the 

treatment compliance date applicable to 

the system in § 141.713. 

(2) Systems must submit to the State 

a proposed watershed control plan no 

later than one year before the applicable 

treatment compliance date in § 141.713. 

The State must approve the watershed 

control plan for the system to receive 

watershed control program treatment 

credit. The watershed control plan must 

include the elements in paragraphs 

(a)(2)(i) through (iv) of this section. 

(i) Identification of an ‘‘area of 

influence’’ outside of which the 

likelihood of Cryptosporidium or fecal 

contamination affecting the treatment 

plant intake is not significant. This is 

the area to be evaluated in future 

watershed surveys under paragraph 

(a)(5)(ii) of this section. 

(ii) Identification of both potential 

and actual sources of Cryptosporidium 

contamination and an assessment of the 

relative impact of these sources on the 

system’s source water quality. 

(iii) An analysis of the effectiveness 

and feasibility of control measures that 

could reduce Cryptosporidium loading 

from sources of contamination to the 

system’s source water. 

(iv) A statement of goals and specific 

actions the system will undertake to 

reduce source water Cryptosporidium 

levels. The plan must explain how the 

actions are expected to contribute to 

specific goals, identify watershed 

partners and their roles, identify 

resource requirements and 

commitments, and include a schedule 

for plan implementation with deadlines 

for completing specific actions 

identified in the plan. 

(3) Systems with existing watershed 

control programs (i.e., programs in place 

on January 5, 2006) are eligible to seek 

this credit. Their watershed control 

plans must meet the criteria in 

paragraph (a)(2) of this section and must 

specify ongoing and future actions that 

will reduce source water 

Cryptosporidium levels. 

(4) If the State does not respond to a 

system regarding approval of a 

watershed control plan submitted under 

this section and the system meets the 

other requirements of this section, the 

watershed control program will be 

considered approved and 0.5 log 

Cryptosporidium treatment credit will 

be awarded unless and until the State 

subsequently withdraws such approval. 

(5) Systems must complete the actions 

in paragraphs (a)(5)(i) through (iii) of 

this section to maintain the 0.5-log 

credit. 

(i) Submit an annual watershed 

control program status report to the 

State. The annual watershed control 

program status report must describe the 

system’s implementation of the 

approved plan and assess the adequacy 

of the plan to meet its goals. It must 

explain how the system is addressing 

any shortcomings in plan 

implementation, including those 

previously identified by the State or as 

the result of the watershed survey 

conducted under paragraph (a)(5)(ii) of 

this section. It must also describe any 

significant changes that have occurred 

in the watershed since the last 

watershed sanitary survey. If a system 

determines during implementation that 

making a significant change to its 

approved watershed control program is 

necessary, the system must notify the 

State prior to making any such changes. 

If any change is likely to reduce the 

level of source water protection, the 

system must also list in its notification 

the actions the system will take to 

mitigate this effect. 

(ii) Undergo a watershed sanitary 

survey every three years for community 

water systems and every five years for 

noncommunity water systems and 

submit the survey report to the State. 

The survey must be conducted 

according to State guidelines and by 

persons the State approves. 

(A) The watershed sanitary survey 

must meet the following criteria: 

encompass the region identified in the 

State-approved watershed control plan 

as the area of influence; assess the 

implementation of actions to reduce 

source water Cryptosporidium levels; 

and identify any significant new sources 

of Cryptosporidium. 

(B) If the State determines that 

significant changes may have occurred 

in the watershed since the previous 

watershed sanitary survey, systems 

must undergo another watershed 

sanitary survey by a date the State 

requires, which may be earlier than the 

regular date in paragraph (a)(5)(ii) of 

this section. 

(iii) The system must make the 

watershed control plan, annual status 

reports, and watershed sanitary survey 

reports available to the public upon 


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request. These documents must be in a 

plain language style and include criteria 

by which to evaluate the success of the 

program in achieving plan goals. The 

State may approve systems to withhold 

from the public portions of the annual 

status report, watershed control plan, 

and watershed sanitary survey based on 

water supply security considerations. 

(6) If the State determines that a 

system is not carrying out the approved 

watershed control plan, the State may 

withdraw the watershed control 

program treatment credit. 

(b) Alternative source. (1) A system 

may conduct source water monitoring 

that reflects a different intake location 

(either in the same source or for an 

alternate source) or a different 

procedure for the timing or level of 

withdrawal from the source (alternative 

source monitoring). If the State 

approves, a system may determine its 

bin classification under § 141.710 based 

on the alternative source monitoring 

results. 

(2) If systems conduct alternative 

source monitoring under paragraph 

(b)(1) of this section, systems must also 

monitor their current plant intake 

concurrently as described in § 141.701. 

(3) Alternative source monitoring 

under paragraph (b)(1) of this section 

must meet the requirements for source 

monitoring to determine bin 

classification, as described in §§ 141.701 

through 141.706. Systems must report 

the alternative source monitoring results 

to the State, along with supporting 

information documenting the operating 

conditions under which the samples 

were collected. 

(4) If a system determines its bin 

classification under § 141.710 using 

alternative source monitoring results 

that reflect a different intake location or 

a different procedure for managing the 

timing or level of withdrawal from the 

source, the system must relocate the 

intake or permanently adopt the 

withdrawal procedure, as applicable, no 

later than the applicable treatment 

compliance date in § 141.713. 

§ 141.717 Pre-filtration treatment toolbox 

components. 

(a) Presedimentation. Systems receive 

0.5-log Cryptosporidium treatment 

credit for a presedimentation basin 

during any month the process meets the 

criteria in this paragraph. 

(1) The presedimentation basin must 

be in continuous operation and must 

treat the entire plant flow taken from a 

surface water or GWUDI source. 

(2) The system must continuously add 

a coagulant to the presedimentation 

basin. 

(3) The presedimentation basin must 

achieve the performance criteria in 

paragraph (3)(i) or (ii) of this section. 

(i) Demonstrates at least 0.5-log mean 

reduction of influent turbidity. This 

reduction must be determined using 

daily turbidity measurements in the 

presedimentation process influent and 

effluent and must be calculated as 

follows: log10(monthly mean of daily 

influent turbidity)¥log10(monthly mean 

of daily effluent turbidity). 

(ii) Complies with State-approved 

performance criteria that demonstrate at 

least 0.5-log mean removal of micronsized particulate material through the 

presedimentation process. 

(b) Two-stage lime softening. Systems 

receive an additional 0.5-log 

Cryptosporidium treatment credit for a 

two-stage lime softening plant if 

chemical addition and hardness 

precipitation occur in two separate and 

sequential softening stages prior to 

filtration. Both softening stages must 

treat the entire plant flow taken from a 

surface water or GWUDI source. 

(c) Bank filtration. Systems receive 

Cryptosporidium treatment credit for 

bank filtration that serves as 

pretreatment to a filtration plant by 

meeting the criteria in this paragraph. 

Systems using bank filtration when they 

begin source water monitoring under 

§ 141.701(a) must collect samples as 

described in § 141.703(d) and are not 

eligible for this credit. 

(1) Wells with a ground water flow 

path of at least 25 feet receive 0.5-log 

treatment credit; wells with a ground 

water flow path of at least 50 feet 

receive 1.0-log treatment credit. The 

ground water flow path must be 

determined as specified in paragraph 

(c)(4) of this section. 

(2) Only wells in granular aquifers are 

eligible for treatment credit. Granular 

aquifers are those comprised of sand, 

clay, silt, rock fragments, pebbles or 

larger particles, and minor cement. A 

system must characterize the aquifer at 

the well site to determine aquifer 

properties. Systems must extract a core 

from the aquifer and demonstrate that in 

at least 90 percent of the core length, 

grains less than 1.0 mm in diameter 

constitute at least 10 percent of the core 

material. 

(3) Only horizontal and vertical wells 

are eligible for treatment credit. 

(4) For vertical wells, the ground 

water flow path is the measured 

distance from the edge of the surface 

water body under high flow conditions 

(determined by the 100 year floodplain 

elevation boundary or by the floodway, 

as defined in Federal Emergency 

Management Agency flood hazard 

maps) to the well screen. For horizontal 

wells, the ground water flow path is the 

measured distance from the bed of the 

river under normal flow conditions to 

the closest horizontal well lateral 

screen. 

(5) Systems must monitor each 

wellhead for turbidity at least once 

every four hours while the bank 

filtration process is in operation. If 

monthly average turbidity levels, based 

on daily maximum values in the well, 

exceed 1 NTU, the system must report 

this result to the State and conduct an 

assessment within 30 days to determine 

the cause of the high turbidity levels in 

the well. If the State determines that 

microbial removal has been 

compromised, the State may revoke 

treatment credit until the system 

implements corrective actions approved 

by the State to remediate the problem. 

(6) Springs and infiltration galleries 

are not eligible for treatment credit 

under this section, but are eligible for 

credit under § 141.718(c). 

(7) Bank filtration demonstration of 

performance. The State may approve 

Cryptosporidium treatment credit for 

bank filtration based on a demonstration 

of performance study that meets the 

criteria in this paragraph. This treatment 

credit may be greater than 1.0-log and 

may be awarded to bank filtration that 

does not meet the criteria in paragraphs 

(c)(1)–(5) of this section. 

(i) The study must follow a Stateapproved protocol and must involve the 

collection of data on the removal of 

Cryptosporidium or a surrogate for 

Cryptosporidium and related 

hydrogeologic and water quality 

parameters during the full range of 

operating conditions. 

(ii) The study must include sampling 

both from the production well(s) and 

from monitoring wells that are screened 

and located along the shortest flow path 

between the surface water source and 

the production well(s). 

§ 141.718 Treatment performance toolbox 

components. 

(a) Combined filter performance. 

Systems using conventional filtration 

treatment or direct filtration treatment 

receive an additional 0.5-log 

Cryptosporidium treatment credit 

during any month the system meets the 

criteria in this paragraph. Combined 

filter effluent (CFE) turbidity must be 

less than or equal to 0.15 NTU in at least 

95 percent of the measurements. 

Turbidity must be measured as 

described in § 141.74(a) and (c). 

(b) Individual filter performance. 

Systems using conventional filtration 

treatment or direct filtration treatment 

receive 0.5-log Cryptosporidium 

treatment credit, which can be in 


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addition to the 0.5-log credit under 

paragraph (a) of this section, during any 

month the system meets the criteria in 

this paragraph. Compliance with these 

criteria must be based on individual 

filter turbidity monitoring as described 

in § 141.174 or § 141.560, as applicable. 

(1) The filtered water turbidity for 

each individual filter must be less than 

or equal to 0.15 NTU in at least 95 

percent of the measurements recorded 

each month. 

(2) No individual filter may have a 

measured turbidity greater than 0.3 NTU 

in two consecutive measurements taken 

15 minutes apart. 

(3) Any system that has received 

treatment credit for individual filter 

performance and fails to meet the 

requirements of paragraph (b)(1) or (2) 

of this section during any month does 

not receive a treatment technique 

violation under § 141.711(c) if the State 

determines the following: 

(i) The failure was due to unusual and 

short-term circumstances that could not 

reasonably be prevented through 

optimizing treatment plant design, 

operation, and maintenance. 

(ii) The system has experienced no 

more than two such failures in any 

calendar year. 

(c) Demonstration of performance. 

The State may approve Cryptosporidium 

treatment credit for drinking water 

treatment processes based on a 

demonstration of performance study 

that meets the criteria in this paragraph. 

This treatment credit may be greater 

than or less than the prescribed 

treatment credits in § 141.711 or 

§§ 141.717 through 141.720 and may be 

awarded to treatment processes that do 

not meet the criteria for the prescribed 

credits. 

(1) Systems cannot receive the 

prescribed treatment credit for any 

toolbox box option in §§ 141.717 

through 141.720 if that toolbox option is 

included in a demonstration of 

performance study for which treatment 

credit is awarded under this paragraph. 

(2) The demonstration of performance 

study must follow a State-approved 

protocol and must demonstrate the level 

of Cryptosporidium reduction the 

treatment process will achieve under 

the full range of expected operating 

conditions for the system. 

(3) Approval by the State must be in 

writing and may include monitoring 

and treatment performance criteria that 

the system must demonstrate and report 

on an ongoing basis to remain eligible 

for the treatment credit. The State may 

designate such criteria where necessary 

to verify that the conditions under 

which the demonstration of 

performance credit was approved are 

maintained during routine operation. 

§ 141.719 Additional filtration toolbox 

components. 

(a) Bag and cartridge filters. Systems 

receive Cryptosporidium treatment 

credit of up to 2.0-log for individual bag 

or cartridge filters and up to 2.5-log for 

bag or cartridge filters operated in series 

by meeting the criteria in paragraphs 

(a)(1) through (10) of this section. To be 

eligible for this credit, systems must 

report the results of challenge testing 

that meets the requirements of 

paragraphs (a)(2) through (9) of this 

section to the State. The filters must 

treat the entire plant flow taken from a 

subpart H source. 

(1) The Cryptosporidium treatment 

credit awarded to bag or cartridge filters 

must be based on the removal efficiency 

demonstrated during challenge testing 

that is conducted according to the 

criteria in paragraphs (a)(2) through 

(a)(9) of this section. A factor of safety 

equal to 1-log for individual bag or 

cartridge filters and 0.5-log for bag or 

cartridge filters in series must be 

applied to challenge testing results to 

determine removal credit. Systems may 

use results from challenge testing 

conducted prior to January 5, 2006 if the 

prior testing was consistent with the 

criteria specified in paragraphs (a)(2) 

through (9) of this section. 

(2) Challenge testing must be 

performed on full-scale bag or cartridge 

filters, and the associated filter housing 

or pressure vessel, that are identical in 

material and construction to the filters 

and housings the system will use for 

removal of Cryptosporidium. Bag or 

cartridge filters must be challenge tested 

in the same configuration that the 

system will use, either as individual 

filters or as a series configuration of 

filters. 

(3) Challenge testing must be 

conducted using Cryptosporidium or a 

surrogate that is removed no more 

efficiently than Cryptosporidium. The 

microorganism or surrogate used during 

challenge testing is referred to as the 

challenge particulate. The concentration 

of the challenge particulate must be 

determined using a method capable of 

discreetly quantifying the specific 

microorganism or surrogate used in the 

test; gross measurements such as 

turbidity may not be used. 

(4) The maximum feed water 

concentration that can be used during a 

challenge test must be based on the 

detection limit of the challenge 

particulate in the filtrate (i.e., filtrate 

detection limit) and must be calculated 

using the following equation: 

Maximum Feed Concentration = 1 × 10 4

× (Filtrate Detection Limit) 

(5) Challenge testing must be 

conducted at the maximum design flow 

rate for the filter as specified by the 

manufacturer. 

(6) Each filter evaluated must be 

tested for a duration sufficient to reach 

100 percent of the terminal pressure 

drop, which establishes the maximum 

pressure drop under which the filter 

may be used to comply with the 

requirements of this subpart. 

(7) Removal efficiency of a filter must 

be determined from the results of the 

challenge test and expressed in terms of 

log removal values using the following 

equation: 

LRV = LOG10(Cf)¥LOG10(Cp) 

Where: 

LRV = log removal value demonstrated 

during challenge testing; Cf = the 

feed concentration measured during 

the challenge test; and Cp = the 

filtrate concentration measured 

during the challenge test. In 

applying this equation, the same 

units must be used for the feed and 

filtrate concentrations. If the 

challenge particulate is not detected 

in the filtrate, then the term Cp must 

be set equal to the detection limit. 

(8) Each filter tested must be 

challenged with the challenge 

particulate during three periods over the 

filtration cycle: within two hours of 

start-up of a new filter; when the 

pressure drop is between 45 and 55 

percent of the terminal pressure drop; 

and at the end of the cycle after the 

pressure drop has reached 100 percent 

of the terminal pressure drop. An LRV 

must be calculated for each of these 

challenge periods for each filter tested. 

The LRV for the filter (LRVfilter) must be 

assigned the value of the minimum LRV 

observed during the three challenge 

periods for that filter. 

(9) If fewer than 20 filters are tested, 

the overall removal efficiency for the 

filter product line must be set equal to 

the lowest LRVfilter among the filters 

tested. If 20 or more filters are tested, 

the overall removal efficiency for the 

filter product line must be set equal to 

the 10th percentile of the set of LRVfilter

values for the various filters tested. The 

percentile is defined by (i/(n+1)) where 

i is the rank of n individual data points 

ordered lowest to highest. If necessary, 

the 10th percentile may be calculated 

using linear interpolation. 

(10) If a previously tested filter is 

modified in a manner that could change 

the removal efficiency of the filter 

product line, challenge testing to 

demonstrate the removal efficiency of 


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the modified filter must be conducted 

and submitted to the State. 

(b) Membrane filtration. (1) Systems 

receive Cryptosporidium treatment 

credit for membrane filtration that meets 

the criteria of this paragraph. Membrane 

cartridge filters that meet the definition 

of membrane filtration in § 141.2 are 

eligible for this credit. The level of 

treatment credit a system receives is 

equal to the lower of the values 

determined under paragraph (b)(1)(i) 

and (ii) of this section. 

(i) The removal efficiency 

demonstrated during challenge testing 

conducted under the conditions in 

paragraph (b)(2) of this section. 

(ii) The maximum removal efficiency 

that can be verified through direct 

integrity testing used with the 

membrane filtration process under the 

conditions in paragraph (b)(3) of this 

section. 

(2) Challenge Testing. The membrane 

used by the system must undergo 

challenge testing to evaluate removal 

efficiency, and the system must report 

the results of challenge testing to the 

State. Challenge testing must be 

conducted according to the criteria in 

paragraphs (b)(2)(i) through (vii) of this 

section. Systems may use data from 

challenge testing conducted prior to 

January 5, 2006 if the prior testing was 

consistent with the criteria in 

paragraphs (b)(2)(i) through (vii) of this 

section. 

(i) Challenge testing must be 

conducted on either a full-scale 

membrane module, identical in material 

and construction to the membrane 

modules used in the system’s treatment 

facility, or a smaller-scale membrane 

module, identical in material and 

similar in construction to the full-scale 

module. A module is defined as the 

smallest component of a membrane unit 

in which a specific membrane surface 

area is housed in a device with a filtrate 

outlet structure. 

(ii) Challenge testing must be 

conducted using Cryptosporidium 

oocysts or a surrogate that is removed 

no more efficiently than 

Cryptosporidium oocysts. The organism 

or surrogate used during challenge 

testing is referred to as the challenge 

particulate. The concentration of the 

challenge particulate, in both the feed 

and filtrate water, must be determined 

using a method capable of discretely 

quantifying the specific challenge 

particulate used in the test; gross 

measurements such as turbidity may not 

be used. 

(iii) The maximum feed water 

concentration that can be used during a 

challenge test is based on the detection 

limit of the challenge particulate in the 

filtrate and must be determined 

according to the following equation: 

Maximum Feed Concentration = 3.16 × 

106 × (Filtrate Detection Limit) 

(iv) Challenge testing must be 

conducted under representative 

hydraulic conditions at the maximum 

design flux and maximum design 

process recovery specified by the 

manufacturer for the membrane module. 

Flux is defined as the throughput of a 

pressure driven membrane process 

expressed as flow per unit of membrane 

area. Recovery is defined as the 

volumetric percent of feed water that is 

converted to filtrate over the course of 

an operating cycle uninterrupted by 

events such as chemical cleaning or a 

solids removal process (i.e., 

backwashing). 

(v) Removal efficiency of a membrane 

module must be calculated from the 

challenge test results and expressed as 

a log removal value according to the 

following equation: 

LRV = LOG10(Cf) × LOG10(Cp) 

Where: 

LRV = log removal value demonstrated 

during the challenge test; Cf = the 

feed concentration measured during 

the challenge test; and Cp = the 

filtrate concentration measured 

during the challenge test. 

Equivalent units must be used for 

the feed and filtrate concentrations. 

If the challenge particulate is not 

detected in the filtrate, the term Cp

is set equal to the detection limit for 

the purpose of calculating the LRV. 

An LRV must be calculated for each 

membrane module evaluated during 

the challenge test. 

(vi) The removal efficiency of a 

membrane filtration process 

demonstrated during challenge testing 

must be expressed as a log removal 

value (LRVC-Test). If fewer than 20 

modules are tested, then LRVC-Test is 

equal to the lowest of the representative 

LRVs among the modules tested. If 20 or 

more modules are tested, then LRVC-Test

is equal to the 10th percentile of the 

representative LRVs among the modules 

tested. The percentile is defined by 

(i/(n+1)) where i is the rank of n 

individual data points ordered lowest to 

highest. If necessary, the 10th percentile 

may be calculated using linear 

interpolation. 

(vii) The challenge test must establish 

a quality control release value (QCRV) 

for a non-destructive performance test 

that demonstrates the Cryptosporidium 

removal capability of the membrane 

filtration module. This performance test 

must be applied to each production 

membrane module used by the system 

that was not directly challenge tested in 

order to verify Cryptosporidium removal 

capability. Production modules that do 

not meet the established QCRV are not 

eligible for the treatment credit 

demonstrated during the challenge test. 

(viii) If a previously tested membrane 

is modified in a manner that could 

change the removal efficiency of the 

membrane or the applicability of the 

non-destructive performance test and 

associated QCRV, additional challenge 

testing to demonstrate the removal 

efficiency of, and determine a new 

QCRV for, the modified membrane must 

be conducted and submitted to the 

State. 

(3) Direct integrity testing. Systems 

must conduct direct integrity testing in 

a manner that demonstrates a removal 

efficiency equal to or greater than the 

removal credit awarded to the 

membrane filtration process and meets 

the requirements described in 

paragraphs (b)(3)(i) through (vi) of this 

section. A direct integrity test is defined 

as a physical test applied to a membrane 

unit in order to identify and isolate 

integrity breaches (i.e., one or more 

leaks that could result in contamination 

of the filtrate). 

(i) The direct integrity test must be 

independently applied to each 

membrane unit in service. A membrane 

unit is defined as a group of membrane 

modules that share common valving 

that allows the unit to be isolated from 

the rest of the system for the purpose of 

integrity testing or other maintenance. 

(ii) The direct integrity method must 

have a resolution of 3 micrometers or 

less, where resolution is defined as the 

size of the smallest integrity breach that 

contributes to a response from the direct 

integrity test. 

(iii) The direct integrity test must 

have a sensitivity sufficient to verify the 

log treatment credit awarded to the 

membrane filtration process by the 

State, where sensitivity is defined as the 

maximum log removal value that can be 

reliably verified by a direct integrity 

test. Sensitivity must be determined 

using the approach in either paragraph 

(b)(3)(iii)(A) or (B) of this section as 

applicable to the type of direct integrity 

test the system uses. 

(A) For direct integrity tests that use 

an applied pressure or vacuum, the 

direct integrity test sensitivity must be 

calculated according to the following 

equation: 

LRVDIT = LOG10 (Qp /(VCF × Qbreach)) 

Where: 

LRVDIT = the sensitivity of the direct 

integrity test; Qp = total design 

filtrate flow from the membrane 

unit; Qbreach = flow of water from an 


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integrity breach associated with the 

smallest integrity test response that 

can be reliably measured, and VCF 

= volumetric concentration factor. 

The volumetric concentration factor 

is the ratio of the suspended solids 

concentration on the high pressure 

side of the membrane relative to 

that in the feed water. 

(B) For direct integrity tests that use 

a particulate or molecular marker, the 

direct integrity test sensitivity must be 

calculated according to the following 

equation: 

LRVDIT = LOG10(Cf)¥LOG10(Cp) 

Where: 

LRVDIT = the sensitivity of the direct 

integrity test; Cf = the typical feed 

concentration of the marker used in 

the test; and Cp = the filtrate 

concentration of the marker from an 

integral membrane unit. 

(iv) Systems must establish a control 

limit within the sensitivity limits of the 

direct integrity test that is indicative of 

an integral membrane unit capable of 

meeting the removal credit awarded by 

the State. 

(v) If the result of a direct integrity 

test exceeds the control limit 

established under paragraph (b)(3)(iv) of 

this section, the system must remove the 

membrane unit from service. Systems 

must conduct a direct integrity test to 

verify any repairs, and may return the 

membrane unit to service only if the 

direct integrity test is within the 

established control limit. 

(vi) Systems must conduct direct 

integrity testing on each membrane unit 

at a frequency of not less than once each 

day that the membrane unit is in 

operation. The State may approve less 

frequent testing, based on demonstrated 

process reliability, the use of multiple 

barriers effective for Cryptosporidium, 

or reliable process safeguards. 

(4) Indirect integrity monitoring. 

Systems must conduct continuous 

indirect integrity monitoring on each 

membrane unit according to the criteria 

in paragraphs (b)(4)(i) through (v) of this 

section. Indirect integrity monitoring is 

defined as monitoring some aspect of 

filtrate water quality that is indicative of 

the removal of particulate matter. A 

system that implements continuous 

direct integrity testing of membrane 

units in accordance with the criteria in 

paragraphs (b)(3)(i) through (v) of this 

section is not subject to the 

requirements for continuous indirect 

integrity monitoring. Systems must 

submit a monthly report to the State 

summarizing all continuous indirect 

integrity monitoring results triggering 

direct integrity testing and the 

corrective action that was taken in each 

case. 

(i) Unless the State approves an 

alternative parameter, continuous 

indirect integrity monitoring must 

include continuous filtrate turbidity 

monitoring. 

(ii) Continuous monitoring must be 

conducted at a frequency of no less than 

once every 15 minutes. 

(iii) Continuous monitoring must be 

separately conducted on each 

membrane unit. 

(iv) If indirect integrity monitoring 

includes turbidity and if the filtrate 

turbidity readings are above 0.15 NTU 

for a period greater than 15 minutes 

(i.e., two consecutive 15-minute 

readings above 0.15 NTU), direct 

integrity testing must immediately be 

performed on the associated membrane 

unit as specified in paragraphs (b)(3)(i) 

through (v) of this section. 

(v) If indirect integrity monitoring 

includes a State-approved alternative 

parameter and if the alternative 

parameter exceeds a State-approved 

control limit for a period greater than 15 

minutes, direct integrity testing must 

immediately be performed on the 

associated membrane units as specified 

in paragraphs (b)(3)(i) through (v) of this 

section. 

(c) Second stage filtration. Systems 

receive 0.5-log Cryptosporidium 

treatment credit for a separate second 

stage of filtration that consists of sand, 

dual media, GAC, or other fine grain 

media following granular media 

filtration if the State approves. To be 

eligible for this credit, the first stage of 

filtration must be preceded by a 

coagulation step and both filtration 

stages must treat the entire plant flow 

taken from a surface water or GWUDI 

source. A cap, such as GAC, on a single 

stage of filtration is not eligible for this 

credit. The State must approve the 

treatment credit based on an assessment 

of the design characteristics of the 

filtration process. 

(d) Slow sand filtration (as secondary 

filter). Systems are eligible to receive 

2.5-log Cryptosporidium treatment 

credit for a slow sand filtration process 

that follows a separate stage of filtration 

if both filtration stages treat entire plant 

flow taken from a surface water or 

GWUDI source and no disinfectant 

residual is present in the influent water 

to the slow sand filtration process. The 

State must approve the treatment credit 

based on an assessment of the design 

characteristics of the filtration process. 

This paragraph does not apply to 

treatment credit awarded to slow sand 

filtration used as a primary filtration 

process. 

§ 141.720 Inactivation toolbox 

components. 

(a) Calculation of CT values. (1) CT is 

the product of the disinfectant contact 

time (T, in minutes) and disinfectant 

concentration (C, in milligrams per 

liter). Systems with treatment credit for 

chlorine dioxide or ozone under 

paragraph (b) or (c) of this section must 

calculate CT at least once each day, with 

both C and T measured during peak 

hourly flow as specified in §§ 141.74(a) 

through (b). 

(2) Systems with several disinfection 

segments in sequence may calculate CT 

for each segment, where a disinfection 

segment is defined as a treatment unit 

process with a measurable disinfectant 

residual level and a liquid volume. 

Under this approach, systems must add 

the Cryptosporidium CT values in each 

segment to determine the total CT for 

the treatment plant. 

(b) CT values for chlorine dioxide and 

ozone. (1) Systems receive the 

Cryptosporidium treatment credit listed 

in this table by meeting the 

corresponding chlorine dioxide CT 

value for the applicable water 

temperature, as described in paragraph 

(a) of this section. 

CT VALUES (MG·MIN/L) FOR Cryptosporidium INACTIVATION BY CHLORINE DIOXIDE 1

Log credit 

Water Temperature, °C 

<=0.5 1 2 3 5 7 10 15 20 25 30 

(i) 0.25 .................................................................... 159 153 140 128 107 90 69 45 29 19 12 

(ii) 0.5 ..................................................................... 319 305 279 256 214 180 138 89 58 38 24 

(iii) 1.0 .................................................................... 637 610 558 511 429 360 277 179 116 75 49 

(iv) 1.5 .................................................................... 956 915 838 767 643 539 415 268 174 113 73 

(v) 2.0 ..................................................................... 1275 1220 1117 1023 858 719 553 357 232 150 98 

(vi) 2.5 .................................................................... 1594 1525 1396 1278 1072 899 691 447 289 188 122 


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CT VALUES (MG·MIN/L) FOR Cryptosporidium INACTIVATION BY CHLORINE DIOXIDE 1—Continued 

Log credit 

Water Temperature, °C 

<=0.5 1 2 3 5 7 10 15 20 25 30 

(vii) 3.0 ................................................................... 1912 1830 1675 1534 1286 1079 830 536 347 226 147 

1Systems may use this equation to determine log credit between the indicated values: Log credit = (0.001506 × (1.09116) Temp) × CT. 

(2) Systems receive the 

Cryptosporidium treatment credit listed 

in this table by meeting the 

corresponding ozone CT values for the 

applicable water temperature, as 

described in paragraph (a) of this 

section. 

CT VALUES (MG·MIN/L) FOR Cryptosporidium INACTIVATION BY OZONE 1

Log credit 

Water Temperature, °C 

<=0.5 1 2 3 5 7 10 15 20 25 30 

(i) 0.25 .................................................................... 6.0 5.8 5.2 4.8 4.0 3.3 2.5 1.6 1.0 0.6 0.39 

(ii) 0.5 ..................................................................... 12 12 10 9.5 7.9 6.5 4.9 3.1 2.0 1.2 0.78 

(iii) 1.0 .................................................................... 24 23 21 19 16 13 9.9 6.2 3.9 2.5 1.6 

(iv) 1.5 .................................................................... 36 35 31 29 24 20 15 9.3 5.9 3.7 2.4 

(v) 2.0 ..................................................................... 48 46 42 38 32 26 20 12 7.8 4.9 3.1 

(vi) 2.5 .................................................................... 60 58 52 48 40 33 25 16 9.8 6.2 3.9 

(vii) 3.0 ................................................................... 72 69 63 57 47 39 30 19 12 7.4 4.7 

1Systems may use this equation to determine log credit between the indicated values: Log credit = (0.0397 × (1.09757)Temp) × CT. 

(c) Site-specific study. The State may 

approve alternative chlorine dioxide or 

ozone CT values to those listed in 

paragraph (b) of this section on a sitespecific basis. The State must base this 

approval on a site-specific study a 

system conducts that follows a Stateapproved protocol. 

(d) Ultraviolet light. Systems receive 

Cryptosporidium, Giardia lamblia, and 

virus treatment credits for ultraviolet 

(UV) light reactors by achieving the 

corresponding UV dose values shown in 

paragraph (d)(1) of this section. Systems 

must validate and monitor UV reactors 

as described in paragraphs (d)(2) and (3) 

of this section to demonstrate that they 

are achieving a particular UV dose value 

for treatment credit. 

(1) UV dose table. The treatment 

credits listed in this table are for UV 

light at a wavelength of 254 nm as 

produced by a low pressure mercury 

vapor lamp. To receive treatment credit 

for other lamp types, systems must 

demonstrate an equivalent germicidal 

dose through reactor validation testing, 

as described in paragraph (d)(2) of this 

section. The UV dose values in this 

table are applicable only to post-filter 

applications of UV in filtered systems 

and to unfiltered systems. 

UV DOSE TABLE FOR Cryptosporidium, Giardia lamblia, AND VIRUS INACTIVATION CREDIT

Log credit Cryptosporidium 

UV dose (mJ/cm2) 

Giardia lamblia 

UV dose (mJ/cm2) 

Virus 

UV dose (mJ/cm2) 

(i) 0.5 .......................................................................................................................... 1.6 1.5 39 

(ii) 1.0 ......................................................................................................................... 2.5 2.1 58 

(iii) 1.5 ........................................................................................................................ 3.9 3.0 79 

(iv) 2.0 ........................................................................................................................ 5.8 5.2 100 

(v) 2.5 ......................................................................................................................... 8.5 7.7 121 

(vi) 3.0 ........................................................................................................................ 12 11 143 

(vii) 3.5 ....................................................................................................................... 15 15 163 

(viii) 4.0 ...................................................................................................................... 22 22 186 

(2) Reactor validation testing. Systems 

must use UV reactors that have 

undergone validation testing to 

determine the operating conditions 

under which the reactor delivers the UV 

dose required in paragraph (d)(1) of this 

section (i.e., validated operating 

conditions). These operating conditions 

must include flow rate, UV intensity as 

measured by a UV sensor, and UV lamp 

status. 

(i) When determining validated 

operating conditions, systems must 

account for the following factors: UV 

absorbance of the water; lamp fouling 

and aging; measurement uncertainty of 

on-line sensors; UV dose distributions 

arising from the velocity profiles 

through the reactor; failure of UV lamps 

or other critical system components; 

and inlet and outlet piping or channel 

configurations of the UV reactor. 

(ii) Validation testing must include 

the following: Full scale testing of a 

reactor that conforms uniformly to the 

UV reactors used by the system and 

inactivation of a test microorganism 

whose dose response characteristics 

have been quantified with a low 

pressure mercury vapor lamp. 

(iii) The State may approve an 

alternative approach to validation 

testing. 

(3) Reactor monitoring. (i) Systems 

must monitor their UV reactors to 

determine if the reactors are operating 

within validated conditions, as 

determined under paragraph (d)(2) of 

this section. This monitoring must 

include UV intensity as measured by a 

UV sensor, flow rate, lamp status, and 

other parameters the State designates 


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based on UV reactor operation. Systems 

must verify the calibration of UV 

sensors and must recalibrate sensors in 

accordance with a protocol the State 

approves. 

(ii) To receive treatment credit for UV 

light, systems must treat at least 95 

percent of the water delivered to the 

public during each month by UV 

reactors operating within validated 

conditions for the required UV dose, as 

described in paragraphs (d)(1) and (2) of 

this section. Systems must demonstrate 

compliance with this condition by the 

monitoring required under paragraph 

(d)(3)(i) of this section. 

Reporting and Recordkeeping 

Requirements 

§ 141.721 Reporting requirements. 

(a) Systems must report sampling 

schedules under § 141.702 and source 

water monitoring results under 

§ 141.706 unless they notify the State 

that they will not conduct source water 

monitoring due to meeting the criteria of 

§ 141.701(d). 

(b) Systems must report the use of 

uncovered finished water storage 

facilities to the State as described in 

§ 141.714. 

(c) Filtered systems must report their 

Cryptosporidium bin classification as 

described in § 141.710. 

(d) Unfiltered systems must report 

their mean source water 

Cryptosporidium level as described in 

§ 141.712. 

(e) Systems must report disinfection 

profiles and benchmarks to the State as 

described in §§ 141.708 through 141.709 

prior to making a significant change in 

disinfection practice. 

(f) Systems must report to the State in 

accordance with the following table for 

any microbial toolbox options used to 

comply with treatment requirements 

under § 141.711 or § 141.712. 

Alternatively, the State may approve a 

system to certify operation within 

required parameters for treatment credit 

rather than reporting monthly 

operational data for toolbox options. 

MICROBIAL TOOLBOX REPORTING REQUIREMENTS

Toolbox option Systems must submit the following information On the following schedule 

(1) Watershed control program (WCP).(i) Notice of intention to develop a new or continue an 

existing watershed control program.

No later than two years before the applicable treatment 

compliance date in § 141.713 

(ii) Watershed control plan .............................................. No later than one year before the applicable treatment

compliance date in § 141.713. 

(iii) Annual watershed control program status report ..... Every 12 months, beginning one year after the applicable treatment compliance date in § 141.713. 

(iv) Watershed sanitary survey report ............................. For community water systems, every three years beginning three years after the applicable treatment compliance date in § 141.713. For noncommunity water 

systems, every five years beginning five years after 

the applicable treatment compliance date in 

§ 141.713. 

(2) Alternative source/intake 

management.

Verification that system has relocated the intake or 

adopted the intake withdrawal procedure reflected in 

monitoring results.

No later than the applicable treatment compliance date 

in § 141.713. 

(3) Presedimentation ............ Monthly verification of the following: (i) Continuous 

basin operation (ii) Treatment of 100% of the flow (iii) 

Continuous addition of a coagulant (iv) At least 0.5- 

log mean reduction of influent turbidity or compliance 

with alternative State-approved performance criteria.

Monthly reporting within 10 days following the month in 

which the monitoring was conducted, beginning on 

the applicable treatment compliance date in 

§ 141.713. 

(4) Two-stage lime softening Monthly verification of the following: (i) Chemical addition and hardness precipitation occurred in two separate and sequential softening stages prior to filtration 

(ii) Both stages treated 100% of the plant flow.

Monthly reporting within 10 days following the month in 

which the monitoring was conducted, beginning on 

the applicable treatment compliance date in 

§ 141.713. 

(5) Bank filtration .................. (i) Initial demonstration of the following: (A) Unconsolidated, predominantly sandy aquifer (B) Setback distance of at least 25 ft. (0.5-log credit) or 50 ft. (1.0- 

log credit).

No later than the applicable treatment compliance date 

in § 141.713. 

(ii) If monthly average of daily max turbidity is greater 

than 1 NTU then system must report result and submit an assessment of the cause..

Report within 30 days following the month in which the 

monitoring was conducted, beginning on the applicable treatment compliance date in § 141.713. 

(6) Combined filter performance.Monthly verification of combined filter effluent (CFE) 

turbidity levels less than or equal to 0.15 NTU in at 

least 95 percent of the 4 hour CFE measurements 

taken each month.

Monthly reporting within 10 days following the month in 

which the monitoring was conducted, beginning on 

the applicable treatment compliance date in 

§ 141.713. 

(7) Individual filter performance.Monthly verification of the following: (i) Individual filter 

effluent (IFE ) turbidity levels less than or equal to 

0.15 NTU in at least 95 percent of samples each 

month in each filter (ii) No individual filter greater 

than 0.3 NTU in two consecutive readings 15 minutes apart.

Monthly reporting within 10 days following the month in 

which the monitoring was conducted, beginning on 

the applicable treatment compliance date in 

§ 141.713.] 

(8) Demonstration of performance.(i) Results from testing following a State approved protocol.

(ii) As required by the State, monthly verification of operation within conditions of State approval for demonstration of performance credit.

No later than the applicable treatment compliance date 

in § 141.713. 

Within 10 days following the month in which monitoring 

was conducted, beginning on the applicable treatment compliance date in § 141.713. 


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MICROBIAL TOOLBOX REPORTING REQUIREMENTS—Continued 

Toolbox option Systems must submit the following information On the following schedule 

(9) Bag filters and cartridge 

filters.

(i) Demonstration that the following criteria are met: (A) 

Process meets the definition of bag or cartridge filtration; (B) Removal efficiency established through challenge testing that meets criteria in this subpart.

No later than the applicable treatment compliance date 

in § 141.713. 

(ii) Monthly verification that 100% of plant flow was filtered.Within 10 days following the month in which monitoring 

was conducted, beginning on the applicable treatment compliance date in § 141.713. 

(10) Membrane filtration ....... (i) Results of verification testing demonstrating the following: (A) Removal efficiency established through 

challenge testing that meets criteria in this subpart; 

(B) Integrity test method and parameters, including 

resolution, sensitivity, test frequency, control limits, 

and associated baseline.

No later than the applicable treatment compliance date 

in § 141.713. 

(ii) Monthly report summarizing the following: (A) All direct integrity tests above the control limit; (B) If applicable, any turbidity or alternative state-approved indirect integrity monitoring results triggering direct integrity testing and the corrective action that was taken.Within 10 days following the month in which monitoring 

was conducted, beginning on the applicable treatment compliance date in § 141.713. 

(11) Second stage filtration .. Monthly verification that 100% of flow was filtered 

through both stages and that first stage was preceded by coagulation step.

Within 10 days following the month in which monitoring 

was conducted, beginning on the applicable treatment compliance date in § 141.713. 

(12) Slow sand filtration (as 

secondary filter).

Monthly verification that both a slow sand filter and a 

preceding separate stage of filtration treated 100% of 

flow from subpart H sources..

Within 10 days following the month in which monitoring 

was conducted, beginning on the applicable treatment compliance date in § 141.713. 

(13) Chlorine dioxide ............ Summary of CT values for each day as described in 

§ 141.720..

Within 10 days following the month in which monitoring 

was conducted, beginning on the applicable treatment compliance date in § 141.713. 

(14) Ozone ........................... Summary of CT values for each day as described in 

§ 141.720..

Within 10 days following the month in which monitoring 

was conducted, beginning on the applicable treatment compliance date in § 141.713. 

(15) UV ................................. (i) Validation test results demonstrating operating conditions that achieve required UV dose.

(ii) Monthly report summarizing the percentage of water 

entering the distribution system that was not treated 

by UV reactors operating within validated conditions 

for the required dose as specified in 141.720(d)..

No later than the applicable treatment compliance date 

in § 141.713. 

Within 10 days following the month in which monitoring 

was conducted, beginning on the applicable treatment compliance date in § 141.713. 

§ 141.722 Recordkeeping requirements. 

(a) Systems must keep results from 

the initial round of source water 

monitoring under § 141.701(a) and the 

second round of source water 

monitoring under § 141.701(b) until 3 

years after bin classification under 

§ 141.710 for filtered systems or 

determination of the mean 

Cryptosporidium level under § 141.710 

for unfiltered systems for the particular 

round of monitoring. 

(b) Systems must keep any 

notification to the State that they will 

not conduct source water monitoring 

due to meeting the criteria of 

§ 141.701(d) for 3 years. 

(c) Systems must keep the results of 

treatment monitoring associated with 

microbial toolbox options under 

§§ 141.716 through 141.720 and with 

uncovered finished water reservoirs 

under § 141.714, as applicable, for 3 

years. 

Requirements for Sanitary Surveys 

Performed by EPA 

§ 141.723 Requirements to respond to 

significant deficiencies identified in sanitary 

surveys performed by EPA. 

(a) A sanitary survey is an onsite 

review of the water source (identifying 

sources of contamination by using 

results of source water assessments 

where available), facilities, equipment, 

operation, maintenance, and monitoring 

compliance of a PWS to evaluate the 

adequacy of the PWS, its sources and 

operations, and the distribution of safe 

drinking water. 

(b) For the purposes of this section, a 

significant deficiency includes a defect 

in design, operation, or maintenance, or 

a failure or malfunction of the sources, 

treatment, storage, or distribution 

system that EPA determines to be 

causing, or has the potential for causing 

the introduction of contamination into 

the water delivered to consumers. 

(c) For sanitary surveys performed by 

EPA, systems must respond in writing 

to significant deficiencies identified in 

sanitary survey reports no later than 45 

days after receipt of the report, 

indicating how and on what schedule 

the system will address significant 

deficiencies noted in the survey. 

(d) Systems must correct significant 

deficiencies identified in sanitary 

survey reports according to the schedule 

approved by EPA, or if there is no 

approved schedule, according to the 

schedule reported under paragraph (c) 

of this section if such deficiencies are 

within the control of the system. 

PART 142—NATIONAL PRIMARY 

DRINKING WATER REGULATIONS 

IMPLEMENTATION 

■ 8. 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, 300j9 and 300j-11. 

■ 9. Section 142.14 is amended by 

adding paragraph (a)(9) to read as 

follows: 

§ 142.14 Records kept by States. 

* * * * * 

(a) * * * 


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786 Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules and Regulations 

(9) Any decisions made pursuant to 

the provisions of part 141, subpart W of 

this chapter. 

(i) Results of source water E. coli and 

Cryptosporidium monitoring. 

(ii) The bin classification after the 

initial and after the second round of 

source water monitoring for each 

filtered system, as described in 

§ 141.710 of this chapter. 

(iii) Any change in treatment 

requirements for filtered systems due to 

watershed assessment during sanitary 

surveys, as described in § 141.711(d) of 

this chapter. 

(iv) The determination of whether the 

mean Cryptosporidium level is greater 

than 0.01 oocysts/L after the initial and 

after the second round of source water 

monitoring for each unfiltered system, 

as described in § 141.712(a) of this 

chapter. 

(v) The treatment processes or control 

measures that systems use to meet their 

Cryptosporidium treatment 

requirements under § 141.711 or 

§ 141.712 of this chapter. 

(vi) A list of systems required to cover 

or treat the effluent of an uncovered 

finished water storage facility, as 

specified in § 141.714 of this chapter. 

* * * * * 

■ 10. Section 142.15 is amended by 

adding paragraph (c)(6) to read as 

follows: 

§ 142.15 Reports by States. 

(c) * * * 

(6) Subpart W. (i) The bin 

classification after the initial and after 

the second round of source water 

monitoring for each filtered system, as 

described in § 141.710 of this chapter. 

(ii) Any change in treatment 

requirements for these systems due to 

watershed assessment during sanitary 

surveys, as described in § 141.711(d) of 

this chapter. 

(iii) The determination of whether the 

mean Cryptosporidium level is greater 

than 0.01 oocysts/L both after the initial 

and after the second round of source 

water monitoring for each unfiltered 

system, as described in § 141.712(a) of 

this chapter. 

* * * * * 

■ 11. Section 142.16 is amended by 

adding paragraph (n) to read as follows: 

§ 142.16 Special primacy conditions. 

* * * * * 

(n) Requirements for States to adopt 

40 CFR part 141, subpart W. 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, subpart W, 

must contain a description of how the 

State will accomplish the following 

program requirements where allowed in 

State programs. 

(1) Approve an alternative to the E. 

coli levels that trigger Cryptosporidium 

monitoring by filtered systems serving 

fewer than 10,000 people, as described 

in § 141.701(a)(5). 

(2) Assess significant changes in the 

watershed and source water as part of 

the sanitary survey process and 

determine appropriate follow-up action 

for systems, as described in § 141.711(d) 

of this chapter. 

(3) Approve watershed control 

programs for the 0.5-log treatment credit 

in the microbial toolbox, as described in 

§ 141.716(a) of this chapter. 

(4) Approve protocols for 

demonstration of performance treatment 

credits in the microbial toolbox, as 

allowed under § 141.718(c) of this 

chapter. 

(5) Approve protocols for alternative 

ozone and chlorine dioxide CT values in 

the microbial toolbox, as allowed under 

§ 141.720(c) of this chapter. 

(6) Approve an alternative approach 

to UV reactor validation testing in the 

microbial toolbox, as allowed under 

§ 141.720(d)(2)(iii) of this chapter. 

* * * * * 

[FR Doc. 06–4 Filed 1–4–06; 8:45 am] 

BILLING CODE 6560–50–P 


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