United States
Environmental Protection
Agency
Office of Water
(4606)
EPA816-F-01-011
May 2001
vwvw.epa.gov/safewater
&EPA
Interim Enhanced Surface Water
Treatment Rule:
A Quick Reference Guide
Overview of the Rule
Title
Purpose
General
Description
Utilities
Covered
Interim Enhanced Surface Water Treatment Rule (IESWTR)
63 FR 69478 - 69521, December 16, 1998, Vol. 63, No. 241
Revisions to the Interim Enhanced Surface Water Treatment Rule (IESWTR), the Stage 1
Disinfectants and Disinfection Byproducts Rule (Stage 1 DBPR), and Revisions to State
Primacy Requirements to Implement the Safe Drinking Water Act (SDWA) Amendments
66 FR 3770, January 16, 2001, Vol 66, No. 29
Improve public health control of microbial contaminants, particularly Cryptosporidium.
Prevent significant increases in microbial risk that might otherwise occur when systems
implement the Stage 1 Disinfectants and Disinfection Byproducts Rule.
Builds upon treatment technique approach and requirements of the 1989 Surface Water
Treatment Rule. Relies on existing technologies currently in use at water treatment plants.
Sanitary survey requirements apply to all public water systems using surface water or
ground water under the direct influence of surface water, regardless of size. All remaining
requirements apply to public water systems that use surface water or ground water under
the direct influence of surface water and serve 10,000 or more people.
Major Provisions
Regulated Contaminants
Cryptosporidium
Turbidity Performance
Standards
> Maximum contaminant level goal (MCLG) of zero.
* 99 percent (2 -log) physical removal for systems that filter.
> Include in watershed control program for unfiltered systems.
Conventional and direct filtration combined filter effluent:
* < 0.3 nephelometric turbidity units (NTU) in at least 95 percent of
measurements taken each month.
» Maximum level of 1 NTU.
Turbidity Monitoring Requirements
(Conventional and Direct Filtration)
Combined Filter Effluent
Individual Filter Effluent
* Performed every 4 hours to ensure compliance with turbidity
performance standards.
* Performed continuously (every 15 minutes) to assist treatment plant
operators in understanding and assessing filter performance.
Additional Requirements
> Disinfection profiling and benchmarking.
* Construction of new uncovered finished water storage facilities prohibited.
* Sanitary surveys, conducted by the state, for all surface water and ground water under the
direct influence of surface water systems regardless of size (every 3 years for community water systems
and every 5 years for noncommunity water systems).
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Profiling and Benchmarki
For additional information
on the IESWTR
Call the Safe Drinking Water
Hotline at 1-800-426-4791;
visit the EPA web site at
www.epa.gov/safewater; or
contact your State drinking
water representative.
Additional material is
available at www.epa.gov/
safewater/mdbp/
implement.html.
Public water systems must evaluate impacts on microbial risk before changing
disinfection practices to ensure adequate protection is maintained. The three major steps
are:
* Determine if a public water system needs to profile based on TTHM and HAAS levels
(applicability monitoring)
* Develop a disinfection profile that reflects daily Giardia lamblia inactivation for at least a year
(systems using ozone or chloramines must also calculate inactivation of viruses)
* Calculate a disinfection benchmark (lowest monthly inactivation) based on the profile and
consult with the state prior to making a significant change to disinfection practices
Critical Deadlines and Requirements
For Drinking Water Systems
February 16, 1999
March 1999
April 16, 1999
December 31, 1999
April 1,2000
March 31, 2001
January 1, 2002
Construction of uncovered finished water reservoirs is prohibited.
Public water systems lacking ICR or other occurrence data begin 4 quarters of
applicability monitoring for TTHM and HAAS to determine if disinfection
profiling is necessary.
Systems that have 4 consecutive quarters of HAAS occurrence data that meet
the TTHM monitoring requirements must submit data to the state to determine
if disinfection profiling is necessary.
Public water systems with ICR data must submit it to states to determine if
disinfection profiling is necessary.
Public water systems must begin developing a disinfection profile if their annual
average (based on 4 quarters of data) for TTHM is greater than or equal to
0.064 mg/L or HAAS is greater than or equal to 0.048 mg/L.
Disinfection profile must be complete.
Surface water systems or ground water under the direct influence of surface
water systems serving 10,000 or more people must comply with all IESWTR
provisions (e.g., turbidity standards, individual filter monitoring).
For States
December 16, 2000
January 2002
December 16, 2002
December 2004
December 2006
States submit IESWTR primacy revision applications to EPA (triggers interim
primacy).
States begin first round of sanitary surveys.
Primacy extension deadline - all states with an extension must submit primacy
revision applications to EPA.
States must complete first round of sanitary surveys for community water
systems.
States must complete first round of sanitary surveys for noncommunity water
systems.
Public Health Benefits
Implementation of
the IESWTR will
result in ...
Estimated impacts of
the IESWTR
include ...
Increased protection against gastrointestinal illnesses from
Cryptosporidium and other pathogens through improvements in filtration.
Reduced likelihood of endemic illness from Cryptosporidium by 110,000 to
463,000 cases annually.
Reduced likelihood of outbreaks of cryptosporidiosis.
National total annualized cost: $307 million
92 percent of households will incur an increase of less than $1 per month.
Less than 1 percent of households will incur an increase of more than $5 per
month (about $8 per month).
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