Indian Bend Wash Area

Overview

The Indian Bend Wash Area is a 13-square-mile Superfund site in Scottsdale and Tempe, Arizona. Companies disposed of industrial solvents directly onto soil and into dry wells until the 1970s, contaminating both soil and groundwater. EPA added the site to the National Priorities List in September 1983 and has divided cleanup into ten operable units. The site is well into long-term cleanup but two units are still in active investigation phases, with Records of Decision expected around 2028 for each.

Contaminants include chlorinated solvents such as trichloroethylene (TCE), tetrachloroethene, and chloroform found in groundwater, soil, and soil gas. Benzene, toluene, xylenes, and various other volatile organic compounds (VOCs) appear in southern portions of the site. Per- and polyfluoroalkyl substances (PFAS), sometimes called "forever chemicals," have also been detected and are the subject of a new investigation launched in 2023. TCE is a known human carcinogen linked to fetal heart defects. PFAS have been associated with cancer, thyroid disease, elevated cholesterol, and immune and endocrine system problems.

In Scottsdale, five groundwater treatment plants extract and treat contaminated water using air stripping and carbon filtration, then blend the treated water into the municipal supply. The oldest plant has operated since 1994 and has treated over 145 billion gallons, removing more than 99,205 pounds of TCE. Soil vapor extraction has addressed several former industrial source areas. Buildings near remaining soil contamination at Area 7, a former Siemens facility in downtown Scottsdale, have been fitted with sub-slab depressurization systems to block chemical vapors from entering indoor air. In Tempe, groundwater has met cleanup goals for VOCs, though three municipal supply wells were suspended after PFAS was detected above federal health advisory levels.

EPA assessments indicate human exposure is currently under control, groundwater migration is stabilized, and construction cleanup is complete. The site achieved sitewide ready for anticipated reuse in September 2012. Fifty-eight businesses now operate on or near the site, employing over 1,200 people. Institutional controls restrict certain land uses, and Arizona requires permits before drilling new wells to protect against groundwater risks.

Community members can stay involved through the upcoming Five-Year Review, which EPA will complete by September 30, 2026. EPA is also updating its Community Involvement Plan and invites residents to participate in interviews. People can contact Community Involvement Coordinator Kaitlyn Mansoorieh to ask questions, provide input, or join the mailing list. Remedial Project Managers Vicky Wiraatmadja and Ethan Finkel handle technical questions for the North and South sections of the site, respectively. The state point of contact is Katelyn Kane-DeVries with the Arizona Department of Environmental Quality.