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Pacific Southwest, Region 9

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

Tribal Water Protection

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Underground Injection Control (UIC)

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EPA Region 9, with support from tribal water quality agencies, directly implements the UIC program for 145 federally recognized tribes.

The UIC Program regulates the subsurface injection of waste fluids below, into, and above underground sources of drinking water (USDWs).

UIC Wells on Tribal Lands

For tribal lands in Region 9, Class V wells, commonly known as shallow injection wells, are among the greatest threats to the quality of underground sources of drinking water, due to their prevalence and lack of proper operation and maintenance. There are more than 30 varieties of Class V wells (PDF) (3 pp, 34 K) recognized by EPA Region 9.

The most common UIC wells on Tribal lands are:

Septic Systems

The most common underground injection wells (Class V wells) on tribal lands in Region 9 are large-capacity septic systems and wastewater treatment plant effluent disposal wells.

Large-capacity septic systems are defined as receiving, or having the capacity to receive, solely sanitary waste from at least 20 persons per day. See the Class V Well Types to help you determine if your septic system is a Class V well.

Several tribes in Region 9 have installed and are operating technically advanced, onsite wastewater treatment plants (i.e., sequential batch reactors (SBRs), membrane bio-reactors (MBRs), small package plants, etc.) that dispose wastewater via subsurface distribution systems. When these systems treat waste from 20 or more people per day, they are regulated under the UIC program.

For more information, see EPA Region 9’s web page on onsite sewage treatment.

Examples of facilities served by large capacity septic systems and wastewater treatment plants include:

  • casinos
  • housing clusters
  • public buildings
  • administration buildings
  • daycare centers
  • gymnasiums
  • stores

EPA Region 9 developed Tribal Management of Onsite Wastewater Treatment Systems (PDF) (PDF, 2 pages, 428 KB) guidance to help tribes manage their onsite wastewater systems.

Requirements for UIC well owners/operators

Owners/operators of UIC wells are required to submit inventory information (PDF) (3 pp, 1.1 MB) and are prohibited from contaminating underground sources of drinking water. For more information on UIC regulations and guidance, go to EPA’s National UIC Web site.

If you think you may own or operate a Class V UIC well, please contact

Aaron Setran (setran.aaron@epa.gov)
(415) 972-3457

Emmanuelle Rapicavoli (rapicavoli.emmanuelle@epa.gov)
(415) 972-3969

Region 9 Tribal UIC Program Activities

The EPA Region 9 Tribal UIC Program:

  • Collects UIC inventory information
  • Provides technical assistance directly to tribes
  • Conducts inspections and compliance assistance site visits on tribal lands
  • Provides outreach on banned Class V wells (large capacity cesspools and motor vehicle disposal wells)
  • Funds Rural Community Assistance Corporation (RCAC) which provides technical assistance on wastewater issues (CA and Western AZ areas)
  • Reviews and comments on Tribal Environmental Assessment documents and pre-construction designs.

Free technical assistance for UIC wells

Under EPA Region 9, the Rural Community Assistance Corporation (RCAC) provides technical assistance to tribes in California and western Arizona. The technical assistance focuses on the proper operation and maintenance of tribal onsite wastewater systems. To learn more about this opportunity please contact:

Aaron Setran (setran.aaron@epa.gov)
(415) 972-3457

Emmanuelle Rapicavoli (rapicavoli.emmanuelle@epa.gov)
(415) 972-3969

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