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Water: Water Security

Basic Information about Water Security

Safe drinking water and properly treated wastewater are critical to modern life. This web site provides information to help drinking water and wastewater utilities:

  • Assess and reduce vulnerabilities to potential terrorist attacks
  • Plan for and practice response to emergencies and incidents
  • Develop new security technologies to detect and monitor contaminants and prevent security breaches

It is important for drinking water and wastewater utility managers, board members, elected and appointed officials to understand the benefits of investing in preparedness, prevention and mitigation activities at the utility. This video features testimonials from drinking water and wastewater utilities. Each testimonial includes information about real world events that have impacted drinking water and wastewater utilities.

EPA Water Security & Resiliency Highlights brochure (PDF) (4 pp, 985K, About PDF)
This brochure provides a brief overview of EPA’s water security mission and program goals.  The brochure also describes the water security projects and partnerships managed or funded by EPA.
EPA 817-F-12-012, December 2012

Drinking Water

There are approximately 160,000 public water systems (PWSs) in the U.S., each of which regularly supplies drinking water to at least 25 persons or 15 service connections. 84% of the total U.S. population is served by PWSs, while the remainder is served primarily by private wells. PWSs are divided into community water systems (CWSs) and non-community water systems (NCWSs). Examples of CWSs include municipal water systems that serve mobile home parks or residential developments. Examples of NCWSs include schools, factories, and churches, commercial campgrounds, hotels, and restaurants.


Community water systems serve by far the largest proportion of the U.S. population - 273 million out of a total population of 290 million (as of 2003). The figure below shows that 84% of the systems serve 3,300 persons or fewer and these systems provide drinking water to only 9% of the population served by CWSs. In contrast, systems that serve 3,301 persons or more, and are required to conduct vulnerability assessments under the Bioterrorism Act, provide drinking water to 91% of the population served by CWSs.

Because drinking water is consumed directly, health effects associated with contamination have long been major concerns. In addition, interruption or cessation of the drinking water supply can disrupt society, impacting human health and critical activities such as fire protection. The general public correctly perceives drinking water as central to the life of an individual and of society. Consumers are highly sensitive to the threat of contamination or disruption.

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Wastewater treatment is important for preventing disease and protecting the environment. Wastewater is treated by publicly owned treatment works (POTWs) and by private facilities such as industrial plants. There are approximately 2.3 million miles of distribution system pipes and approximately 16,255 POTWs in the U.S. 75% of the total U.S. population is served by POTWs, while the remainder is served by decentralized or private septic systems. POTWs treat 32 billion gallons of wastewater every day.


EPA's initial security focus has been on POTWs. The distribution of POTWs by size and percentage of population served is shown below. POTWs with existing flows greater than 10 million gallons per day (mgd) are considered large; they number approximately 533 systems. POTWs with existing flows between 1 and 10 mgd are considered medium; they number approximately 2,665 systems. POTWs with existing flows of less than 1 mgd are considered small; they number approximately 13,057 systems. For purposes of determining population served, 1 mgd equals approximately 10,000 persons served.

The graphic below shows that while 80% of the systems treat less than 1mgd, these systems provide wastewater treatment to only 11% of the population served by POTWs. In contrast, systems that treat more than 1 mgd provide wastewater treatment to 89% of the population served by POTWs.

Disruption of a wastewater treatment system or service can cause loss of life, economic impacts, and severe public health incidents. If structural damage occurs, wastewater systems can become vulnerable to inadequate treatment. The public is much less sensitive to wastewater as an area of vulnerability than it is to drinking water, however wastewater systems do provide opportunities for terrorist threats.

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EPA's Role in Water Security

Federal and state agencies have long been active in addressing these risks and threats to water and wastewater utilities through regulations, technical assistance, research, and outreach programs. As a result, an extensive system of regulations governing maximum contaminant levels of 90 conventional contaminants (most established by EPA), construction and operating standards (implemented mostly by the states), monitoring, emergency response planning, training, research, and education have been developed to better protect the nation's drinking water supply and receiving waters.

Since the events of 9/11, EPA has been designated as the sector-specific agency responsible for infrastructure protection activities for the nation's drinking water and wastewater systems. EPA is utilizing its position within the water sector and working with its stakeholders to provide information to help protect the nation's drinking water supply from terrorist or other intentional acts.

Safe Drinking Water Hotline and Data Sources

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