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Pacific Southwest, Region 9

Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations

Drinking Water

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The Office of Ground Water and Drinking Water (OGWDW), together with states, tribes, and its many partners, protects public health by ensuring safe drinking water and protecting ground water.

OGWDW, along with EPA's ten regional drinking water programs, oversees implementation of the Safe Drinking Water Act (SDWA), which is the national law safeguarding tap water in America.

The SDWA includes a requirement that EPA establish and enforce standards to which public drinking water systems must adhere.  These public drinking water systems, which may be publicly- or privately-owned, serve at least 25 people or 15 service connections for at least 60 days per year. EPA does not regulate drinking water wells that supply water to fewer than 25 people.

States and tribes are given primary enforcement responsibility (e.g., primacy) for public water systems in their state if they meet certain requirements. These requirements are found in 40 CFR Part 142. Included in these requirements is a provision that the state or tribe must adopt and enforce regulations that are at least as strict as the Federal standards.

A state or a tribe with primacy has direct oversight of the regulated public water systems, and is responsible for ensuring that the system is meeting all of the requirements of the drinking water regulations. In Region 9, the following agencies have been delegated primacy for the drinking water program:

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Arizona: Arizona Department of Environmental Quality

California: California Department of Health Services

Hawaii: Hawaii Bureau of Health Protection

Nevada: Nevada Department of Environmental Protection

Navajo Nation: Navajo Environmental Protection Agency

Pacific Island Territories (American Samoa, Guam, Northern Mariana Islands)

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Click image for the full-size map (PDF 379 KB, About PDF)

Because the primacy agencies receive system specific water quality data, they can be the best resource for questions about a specific system or about general water quality questions specific to that State or Tribe.

Public water systems on tribal lands other than Navajo are regulated by EPA Region 9. Designated staff members (PDF) (1 pg, 379K, About PDF) work with specific tribes to ensure the safety of drinking water (shown on this map).

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