Proposed Long Term 2 Enhanced Surface 

Water Treatment Rule 

Summary 

EPA is proposing the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) to reduce

disease incidence associated with Cryptosporidium and other pathogenic microorganisms in drinking

water. The LT2ESWTR will supplement existing regulations by targeting additional

Cryptosporidium treatment requirements to higher risk systems. This regulation also contains

provisions to mitigate risks from uncovered finished water storage facilities and to ensure that

systems maintain microbial protection as they take steps to reduce the formation of disinfection

byproducts (DBPs).

Background

Cryptosporidium is a protozoan parasite that is of particular concern in drinking water because it is

resistant to disinfectants like chlorine and it has been associated with waterborne disease outbreaks. 

Ingestion of Cryptosporidium can cause acute gastrointestinal illness, and health effects in sensitive

subpopulations (e.g., infants, AIDS patients, the elderly) may be severe, including the risk of death.

Existing drinking water regulations require public water systems (systems) that use surface water

sources and provide filtration to achieve at least a 99 percent (2-log) removal of Cryptosporidium. 

New data on Cryptosporidium infectivity, occurrence, and treatment indicate that current treatment

requirements are adequate for the majority of systems, but there is a subset of systems with higher

vulnerability to Cryptosporidium where additional treatment is necessary. This vulnerable subset

includes those filtered systems with the highest source water Cryptosporidium levels, along with

unfiltered systems (systems that use surface water sources and do not provide filtration). 

About this Regulation 

The LT2ESWTR will protect public health by supplementing existing drinking water regulations 

with additional risk-targeted treatment requirements for Cryptosporidium. This regulation will apply 

to all systems that use surface water or ground water under the direct influence of surface water. 

Cryptosporidium treatment: Under the LT2ESWTR, systems initially conduct source water 

monitoring for Cryptosporidium to determine their treatment requirements. Filtered systems will be 

classified in one of four risk bins based on their monitoring results. EPA projects that the majority of 

systems will be classified in the lowest risk bin, which carries no additional treatment requirements. 

Systems classified in higher risk bins must provide 90 to 99.7 percent (1.0 to 2.5-log) additional 

reduction of Cryptosporidium levels. The regulation specifies a range of treatment and management 

strategies, collectively termed the “microbial toolbox,” that systems may select to meet their 

additional treatment requirements. All unfiltered systems must provide at least 99 or 99.9 percent (2 

or 3-log) inactivation of Cryptosporidium, depending on the results of their monitoring. 

Monitoring: Cryptosporidium monitoring by large systems (serving at least 10,000 people) will 

begin six months after the LT2ESWTR is finalized and will last for a duration of two years. Small 

systems (serving less than 10,000 people) are on a delayed schedule and will start monitoring when 

the required large system monitoring is finished. To reduce monitoring costs, small filtered systems 

will initially conduct one year of monitoring for E. coli, which is a bacterium that is less expensive to 

analyze than Cryptosporidium. These systems will be required to monitor for Cryptosporidium for 
one year only if their E. coli results exceed specified triggering concentrations. Systems must

conduct a second round of monitoring beginning six years after the initial bin classification. Systems

may grandfather equivalent previously collected data in lieu of conducting new monitoring, and

systems are not required to monitor if they provide the maximum level of treatment required under

the rule.

Other requirements: The LT2ESWTR proposal also contains disinfection profiling requirements to

ensure that systems maintain protection against microbial pathogens as they take steps to reduce the

formation of DBPs. These requirements are needed because EPA is concurrently developing a Stage

2 Disinfection Byproducts Rule that will establish more stringent standards for certain DBPs. 

Disinfection profiling involves systems assessing the level of disinfection they currently provide and

then determining the impact that a proposed change in their disinfection practice would have on this

level. Additionally, the proposed LT2ESWTR has requirements that address risk in uncovered

finished water storage facilities, which are subject to contamination if not properly managed or

treated. 

The LT2ESWTR proposal reflects a consensus Agreement in Principle of the Stage 2 Microbial and

Disinfection Byproducts Federal Advisory Committee. 

Environmental and Public Health Benefits

The LT2ESWTR will improve the control of Cryptosporidium and other microbiological pathogens

in drinking water systems with the highest risk levels. EPA estimates that full implementation of the

LT2ESWTR will reduce the incidence of cryptosporidiosis - the gastrointestinal illness caused by

ingestion of Cryptosporidium - by 256,000 to 1,019,000 cases per year, with an associated reduction

of 37 to 141 premature deaths. The additional Cryptosporidium treatment requirements of the

LT2ESWTR will also reduce exposure to other microbial pathogens, such as Giardia, that co-occur

with Cryptosporidium. Additional protection from microbial pathogens will come from the

provisions of this regulation that address disinfection profiling and uncovered finished water storage

facilities, though these benefits have not been quantified. 

Cost of the Regulation 

The LT2ESWTR will result in increased costs to public water systems and States. The mean 

annualized present value costs of the LT2ESWTR are estimated to range from approximately $73.5 

to $111 million (using a three percent discount rate). Public water systems will bear approximately 

99 percent of this total cost ($72.5 to $110 million total annualized), with States incurring the 

remaining 1 percent ($0.9 to $1.0 million total annualized). The average annual household cost is 

estimated to be $1.07 to $1.68 per year, with 98 to 99 percent of households experiencing annual 

costs of less than $12 per year. 

How to Get Additional Information 

For general information on the LT2ESWTR, contact the Safe Drinking Water Hotline, at (800)

426-4791. For copies of the Federal Register notice of the proposed regulation or technical fact

sheets, visit the EPA Safewater website, www.epa.gov/safewater/lt2/index.html. The Safe

Drinking Water Hotline is open Monday through Friday, excluding legal holidays, from 9:00 a.m. to

5:30 p.m. Eastern Time.

Office of Water (4607M) EPA 815-F-03-005 July 2003 www.epa.gov/safewater