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Press Release
Waste Division

Nogales, Ariz. -- Officials from the Arizona Department of Environmental Quality (ADEQ) and the United States Section of the International Boundary and Water Commission (USIBWC) today announced a Settlement Agreement that addresses Clean Water Act (CWA) issues and sets forth a comprehensive plan to mitigate future discharges of untreated wastewater into the Nogales Wash and Santa Cruz River in Nogales, Arizona. With $38,790,000 in federal, state and local non-profit resources, this plan will bring much-needed infrastructure improvements to Santa Cruz County.

The scope of the settlement includes:

  • Upgrade the aged wastewater conveyance pipeline, commonly known as the International Outfall Interceptor (IOI), from the U.S.-Mexico Border to the Nogales International Wastewater Treatment Plant (NIWTP) in Rio Rico, Arizona.
  • Install protective measures for the upgraded IOI in locations vulnerable to damage from stormwater and debris. 

Treated water from the Rio Rico plant is an important contribution to the Santa Cruz River basin which supplies water for drinking, ranching, farming and other activities critical to the Arizona economy. The river also sustains habitat critical to migratory birds, bobcat, deer, javelina and many other species.

“This agreement is a major win for Southern Arizona, helping resolve a decades-old issue that threatened the health and safety of residents and the environment in Nogales and Santa Cruz County,” said Governor Doug Ducey. “Working together, ADEQ and USIBWC have developed a plan that will upgrade this critical infrastructure, reduce hazards from storms and flooding and protect people and businesses in this border community. Arizona is grateful for their hard work to reach this important agreement.”

“Reaching this agreement ushers in a new era of partnership and problem solving among local, state, federal and international government entities, ” said ADEQ Director Misael Cabrera, P.E. “While there is still work to do, this settlement supports the necessary rehabilitation of critical infrastructure at the border to prevent ongoing catastrophic failures, and protect public health and the environment.”

“I have been working with Commissioner Harkins and Director Cabrera on this issue for a long time and I thank them for their tireless work getting this agreement in place,” said U.S. Senator Martha McSally. “Now we will be able to begin fixing this infrastructure that is critical to the safety and operation of the DeConcini Port of Entry and City of Nogales. This settlement makes it even more important that Congress acts to provide certainty for maintaining the IOI by passing the Nogales Wastewater Fairness Act I introduced to ensure the City of Nogales, Santa Cruz County and all of Arizona can rely on continued beneficial trade with Mexico.”

“I’m pleased we’ve identified a path forward that will improve environmental conditions in the region,” said USIBWC Commissioner Jayne Harkins, P.E. “The USIBWC looks forward to getting to work to rehabilitate the IOI as soon as possible.”

Settlement details and path forward:

  • USIBWC has identified $34.2 million of existing funds to immediately begin upgrading the IOI.
  • USIBWC has already finalized engineering plans and in cooperation with state and local officials, has begun negotiating agreements necessary to access the IOI from various locations along its length. USIBWC will put the construction contract out to bid this fall.
  • Arizona is supporting the project with $2.59 million in state funds.
  • Additional support from other partners includes:
    • $1 million from Freeport McMoRan Foundation, and$1 million (in process) from the U.S. Environmental Protection Agency (EPA) through the North American Development Bank for a companion project to work on City of Nogales, Arizona sewer pipelines that connect to the IOI.
    • $1 million (in process) from the U.S. Environmental Protection Agency (EPA) through the North American Development Bank for a companion project to work on City of Nogales, Arizona sewer pipelines that connect to the IOI.
  • ADEQ is currently working to find funds to install a metal screen in the IOI near the border to capture large debris that could otherwise cause sewage spills, estimated at $2.6 – $3.3 million to install, and $360,000 for yearly maintenance.
  • USIBWC is negotiating with the Mexican Section of the IBWC  to secure Mexico’s cost participation in the pipeline rehabilitation.

“The Bank actively seeks out opportunities to collaborate and leverage several sources of funds through local, state and federal partners to deliver environmental infrastructure that improves the quality of life for border residents,” said Dr. Calixto Mateos-Hanel, Managing Director of the North American Development Bank. “It is important to highlight the partnership between EPA and the Bank over the last 25 years through the Border Environmental Infrastructure Fund including this Nogales, Arizona project, which will correct lateral connections to the IOI.”

Critical to this success are the long-standing contributions and cooperation among many local, state and federal officials and the expertise and dedication of ADEQ staff:

ADEQ acknowledges:

  • U.S. Senator Kyrsten Sinema
  • U.S. Representative Ann Kirkpatrick and U.S. Representative Raul M. Grijalva
  • State Senator Frank Pratt, State Representative Gail Griffin, and State Representative Rosanna Gabaldon
  • Santa Cruz County Supervisor Bruce Bracker
  • Arizona-Mexico Commission Vice Chair Juan Ciscomani
  • Arizona Department of Water Resources Director Thomas Buschatzke
  • Arizona Office of the Attorney General

ADEQ gives special recognition:

  • Edna Mendoza, ADEQ Office of Regional and Border Assistance - Manager
  • Hans Huth, ADEQ Associate Hydrologist
  • Mindi Cross, ADEQ Senior Environmental Scientist & Specialist


In 2012, ADEQ filed suit against USIBWC for alleged CWA violations. To establish a path forward for the much needed infrastructure upgrades for the IOI, ADEQ and USIBWC entered into settlement discussions in 2018.

The IOI conveys wastewater from Nogales, Sonora, and Nogales, Arizona for nine miles north of the border to the NIWTP in Rio Rico. The IOI is intersected by piping from the City of Nogales, Arizona, and the unincorporated community of Rio Rico, Arizona, which also contributes wastewater to the NIWTP that the USIBWC operates. 

Roughly 12 million gallons per day (13,442 acre-feet per year) is discharged from the NIWTP facility into the Santa Cruz River. The majority of that discharge originates in Mexico. This large quantity of water:

  1. Replenishes roughly 38 percent of safe groundwater yield in the Santa Cruz active management area (AMA);
  2. Maintains perennial surface water flows in an 18-mile stretch of the Santa Cruz River (accounts for roughly 12 miles of the 18);
  3. Sustains the Audubon‐designated Important Bird Area and provides critical habitat for two endangered species, the Southwest Willow Flycatcher and the Gila Topminnow;
  4. Constitutes a significant portion of the underflow from the Santa Cruz AMA to the Tucson AMA (over 15,000 acre-feet per year); and
  5. Supports ranching, farming and domestic water use in Santa Cruz and Pima counties.

Economic Impact of rivers, lakes and streams in Santa Cruz County | View >

More Information:
Updates on the Nogales IOI | View >


Caroline Oppleman-ADEQ Communications Administrator | 602-540-8072 | Email > 
Sally Spener-US International Boundary and Water Commission | 915-832-4175 | Email >