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Water: Long Term 2 Enhanced Surface Water Treatment Rule

Basic Information

Questions and Answers

EPA has developed the Long Term 2 Enhanced Surface Water Treatment Rule (LT2 rule) to improve your drinking water quality and provide additional protection from disease-causing microorganisms and contaminants that can form during drinking water treatment.

Your drinking water comes from source water locations such as:

  • Lakes
  • Rivers
  • Reservoirs
  • Ground water aquifers

Pathogens, such as Giardia and Cryptosporidium, are often found in water, and can cause gastrointestinal illness (e.g., diarrhea, vomiting, cramps) and other health risks. In many cases, this water needs to be disinfected through the use of additives such as chlorine to inactivate (or kill) microbial pathogens.

Cryptosporidium is a significant concern in drinking water because it contaminates surface waters used as drinking water sources, it is resistant to chlorine and other disinfectants, and it has caused waterborne disease outbreaks. Consuming water with Cryptosporidium, a contaminant in drinking water sources, can cause gastrointestinal illness, which may be severe in people with weakened immune systems (e.g., infants and the elderly) and sometimes fatal in people with severely compromised immune systems (e.g., cancer and AIDS patients).

The purpose of the LT2 rule is to reduce disease incidence associated with Cryptosporidium and other pathogenic microorganisms in your drinking water. The rule applies to all public water systems that use surface water or ground water that is under the direct influence of surface water. The rule will bolster existing regulations and provide a higher level of protection of your drinking water supply by:

  • Targeting additional Cryptosporidium treatment requirements to higher risk systems
  • Requiring provisions to reduce risks from uncovered finished water storage facilities
  • Providing provisions to ensure that systems maintain microbial protection as they take steps to reduce the formation of disinfection byproducts

This combination of steps, combined with the existing regulations, is designed to provide protection from microbial pathogens while simultaneously minimizing health risks to the population from disinfection byproducts.

Questions and Answers

Why is EPA concerned about Cryptosporidium?
Who does this rule apply to?
What are the requirements of this final rule?
How soon after publishing the final rule will the changes take effect?
How will this regulation protect public health?
How much will this rule cost?
Is there funding associated with this rule?
How did EPA develop this rule?
Why are unfiltered water systems required to add treatment?
Where can I find information on contacting a laboratory to analyze my monitoring samples?


Why is EPA concerned about Cryptosporidium?
Cryptosporidium is a significant concern in drinking water because it contaminates most drinking water sources, it is resistant to chlorine and other disinfectants, and it has caused waterborne disease outbreaks. Consuming water with Cryptosporidium can cause gastrointestinal illness, which may be severe and sometimes fatal for people with weakened immune systems (which may include infants, the elderly, and people who have AIDS).

Current regulations require filtered water systems to reduce source water Cryptosporidium levels by 99 percent (2-log). Recent data on Cryptosporidium indicate that this treatment is sufficient for most systems, but additional treatment is necessary for certain higher risk systems. These higher risk systems include filtered water systems with high levels of Cryptosporidium in their water sources and all unfiltered water systems, which do not treat for Cryptosporidium.

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Who does this rule apply to?
The LT2ESWTR applies to all public water systems (systems) that use surface water or ground water under the direct influence of surface water. This includes about 14,000 systems serving approximately 180 million people.

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What are the requirements of the rule?

Systems initially monitor their water sources to determine treatment requirements. This monitoring involves two years of monthly sampling for Cryptosporidium. To reduce monitoring costs, small filtered water systems will first monitor for E. coli–a bacterium that is less expensive to analyze than Cryptosporidium–and will be monitor for Cryptosporidium only if their E. coli results exceed specified concentration levels.

Treatment: Filtered water systems will be classified in one of four treatment categories (bins) based on their monitoring results. Most systems are expected to be classified in the lowest bin and will face no additional requirements. Systems classified in higher bins must provide additional water treatment to further reduce Cryptosporidium levels by 90 to 99.7 percent (1.0 to 2.5-log), depending on the bin. Systems will select from different treatment and management options in a “microbial toolbox” to meet their additional treatment requirements. All unfiltered water systems must provide at least 99 or 99.9 percent (2 or 3-log) inactivation of Cryptosporidium, depending on the results of their monitoring.

Uncovered Finished Water Reservoirs: Systems that store treated water in open reservoirs must either cover the reservoir or treat the reservoir discharge to inactivate 4-log virus, 3-log Giardia lamblia, and 2-log Cryptosporidium. These requirements are necessary to protect against the contamination of water that occurs in open reservoirs.

Disinfection Benchmarking: Systems must review their current level of microbial treatment before making a significant change in their disinfection practice. This review will assist systems in maintaining protection against microbial pathogens as they take steps to reduce the formation of disinfection byproducts under the Stage 2 Disinfection Byproducts Rule, which EPA is finalizing along with the LT2ESWTR.

How soon after publishing the final rule will the changes take effect?
Monitoring starting dates are staggered by system size. The largest systems (serving at least 100,000 people) will begin monitoring in October 2006 and the smallest systems (serving fewer than 10,000 people) will not begin monitoring until October 2008. After completing monitoring and determining their treatment bin, systems generally have three years to comply with any additional treatment requirements. Systems must conduct a second round of monitoring six years after completing the initial round to determine if source water conditions have changed significantly.

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How will this rule protect public health?

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 compliance with the LT2ESWTR will reduce the incidence of cryptosporidiosis - the gastrointestinal illness caused by ingestion of Cryptosporidium - by 89,000 to 1,459,000 cases per year, with an associated reduction of 20 to 314 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 provisions in this rule for reviewing disinfection practices and for covering or treating uncovered finished water reservoirs, though EPA has not quantified these benefits.

How much will this rule cost?
The LT2ESWTR will result in increased costs to public water systems and States. The average annualized present value costs of the LT2ESWTR are estimated to range from $92 to $133 million (using a three percent discount rate). Public water systems will bear approximately 99 percent of this total cost, with States incurring the remaining 1 percent. The average annual household cost is estimated to be $1.67 to $2.59 per year, with 96 to 98 percent of households experiencing annual costs of less than $12 per year.

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Is funding associated with this rule?
Funding may be available from programs administered by EPA and other Federal agencies to assist systems in complying with the LT2ESWTR. The Drinking Water State Revolving Fund (DWSRF) assists systems 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 low-cost loans and other types of assistance to eligible systems.

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. The CDBG program includes direct grants to States, which in turn are awarded to smaller communities, rural areas, and colonias in Arizona, California, New Mexico, and Texas and direct grants to U.S. territories and trusts.

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How did EPA develop this rule?
The Cryptosporidium monitoring and treatment requirements in the LT2ESWTR reflect a consensus Agreement in Principle of the Stage 2 M-DBP Federal Advisory Committee. This Committee consisted of organizational members representing EPA, state and local public health and regulatory agencies, local elected officials, tribes, drinking water suppliers, chemical and equipment manufacturers, and public interest groups. EPA published the Agreement in a December 29, 2000, Federal Register notice.

EPA proposed the LT2ESWTR on August 11, 2003. Approximately 200 organizations and individuals submitted comments on the proposal. In the final LT2ESWTR, we made a number of changes from the proposal to address these comments. In response to concerns with both laboratory capacity and the implementation schedule, we have moved back the dates when many systems will begin monitoring. This approach will provide sufficient time for Cryptosporidium laboratories to develop adequate laboratory to support monitoring under the rule. Further, it will allow states the time to play a greater role in providing oversight for monitoring by their systems.

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Why are unfiltered water systems required to add treatment?

Existing regulations did not require unfiltered systems to provide any treatment for Cryptosporidium. Although unfiltered systems maintain watershed control programs to protect water quality, recent surveys have shown Cryptosporidium to be present in the sources of unfiltered systems. Without treatment, these Cryptosporidium will pass into the water distributed to consumers. Available data indicate that the average risk from Cryptosporidium in unfiltered systems is higher than in filtered systems, so that treatment by unfiltered systems is required to achieve comparable public health protection. Further, with available technologies like UV and ozone, treatment for Cryptosporidium is feasible for all unfiltered systems. Consequently, EPA is establishing requirements under the LT2ESWTR for all unfiltered systems to treat for Cryptosporidium, with the required degree of treatment depending on the source water contamination level.

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Where can I find information on contacting a laboratory to analyze my monitoring samples?

EPA's program for identifying laboratories that can reliably measure the occurrence of Cryptosporidium in surface water using approved EPA methods is available at:

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