1,4-Dioxane

About 1,4-Dioxane

1,4-dioxane was used as a stabilizer in industrial solvents in aircraft manufacturing facilities from the 1940s to the 1970s. It was detected in groundwater at the Tucson Airport Remediation Project (TARP) well field. The EPA does not regulate 1,4-dioxane; however, it issued a new health advisory for drinking water utilities. Tucson Water constructed a new treatment facility with state-of-the-art technology to effectively remove 1,4-dioxane from water.

Construction of the Advanced Oxidation Process (AOP) Water Treatment Facility began in July 2012 and was completed in January 2014. It operates in conjunction with the adjacent TARP facility to produce up to seven million gallons of purified water a day.

Unified Community Advisory Board

A Unified Community Advisory Board (UCAB) was formed in 1995, comprised of area residents and government agencies. Anyone interested in preserving groundwater quality and learning more about the process of removing TARP-area contaminants may attend a UCAB quarterly meeting.

Visit the EPA's Tucson International Airport Area page for UCAB meeting dates and topics.

Contacts: Yolanda Herrera (520) 991-3307 or Carolyn Cooper (415) 972-3147

Frequently Asked Questions

Is my water safe?

Yes. Tucson Water ensures that all the water it delivers meets all federal drinking water standards as established by the U.S. Environmental Protection Agency (EPA) and is safe at all times for drinking, cooking, bathing and other uses.

What is 1,4-Dioxane?

1,4-Dioxane is a stabilizing agent for Trichloroethane (TCA), a hazardous chemical used in industrial and defense related activities in the 1950s - 1970s. For more information, visit the EPA Fact Sheet.

Where is the 1,4-Dioxane located?

1,4-Dioxane is found in groundwater pumped from a contamination plume on Tucson’s south side. The water from this plume is pumped to the Tucson Airport Remediation Project (TARP) Treatment Plant where, since 1995, the groundwater has been treated to remove trichloroethylene (TCE) as part of the cleanup of that contamination. However, the TARP plant did not remove 1,4-Dioxane from the water.

What does the EPA say about 1,4-Dioxane?

The EPA currently has a Health Advisory level for 1,4-Dioxane of ≤ 0.35 parts per billion. No federal Maximum Contaminant Level (MCL) has been established. 1,4-Dioxane is classified as “likely to be carcinogenic to humans” by all routes of exposure. EPA advisories and technical fact sheets on the contaminant are provided as guidelines for water utilities across the county and are not enforced by the agency.

How is 1,4-Dioxane removed from the water?

Tucson Water constructed an Advanced Oxidation Process Water Treatment Facility, which began operation in January 2014. The technology combines ultraviolet (UV) light with hydrogen peroxide to create a strong oxidant that removes 1,4-Dioxane from water. Granular-activated carbon then removes any hydrogen peroxide left in treated water.

Where is this water being delivered?

As of June 2021, treated water pumped from TARP is no longer served as drinking water to Tucson Water customers. Treated water from TARP is now delivered to the reclaimed water system and is also recharged to the Santa Cruz River.

Is there 1,4-Dioxane in the water delivered to the area around the TARP well field?

There is no 1,4-Dioxane in the water delivered to the southern part of Tucson Water’s service area – the area near and around the TARP well field. Water delivered here comes from the Santa Cruz Well Field, the Clearwater Facility, and the Southern Avra Valley Well Field. Tucson Water tests water in this area to verify that no 1,4-Dioxane is present.

Who is responsible for oversight of the TARP Plant and Tucson’s water quality?

Tucson Water reports regularly about the TARP Plant to the Unified Community Action Board (UCAB) - the citizens group charged with monitoring the TCE remediation process and 1, 4-Dioxane levels. Tucson Water reports the results of all water quality testing to the Arizona Department of Environmental Quality (ADEQ) on a regular basis. ADEQ is responsible for overseeing and enforcing all EPA water quality regulations in Arizona.

Does Tucson Water test my water to make sure it’s safe?

Yes. Tucson Water is committed to providing safe, high-quality water to all its customers. We perform about 14,500 water quality tests on samples collected from all over our service area. The testing is done at our Water Quality Laboratory at the Hayden-Udall Facility in Avra Valley. We also send samples to independent labs. Tucson Water is responsible for reporting regularly to the Arizona Department of Environmental Quality on all water quality testing.

What exactly is a “part per billion”?

One part per billion is like one drop of water in 22,000 gallons. Another analogy for one part per billion is one inch in 16 miles. In other words, one part per billion is a very small amount. Tucson Water’s testing in the water delivery area shows 1,4-Dioxane at undetectable levels of less than ≤ 0.1 parts per billion.