Nogales has a sewage problem

In the borderlands, members of Congress work to resolve wastewater woes.


The binational city of Nogales, named in Spanish for the stands of walnut trees that once grew on its lush hillsides, sprawls across the Santa Cruz River Valley. These days a wall grows in the desert, dividing the city into Nogales, Sonora, and Nogales, Arizona.

Still, like any city, Ambos Nogales – the combined cities with their interconnected maquiladora system, tourism industry, and fresh produce port of entry – functions much like a single superorganism. It drinks water, consumes raw materials, and makes waste. Its digestive system is responsible for processing millions of gallons of sewage each day. And, lately, Ambos Nogales has had a stomachache – one Arizona’s members of Congress are trying to treat.

Sewage produced by Ambos Nogales flows through the nine-mile-long International Outfall Interceptor tunnel, or IOI, to the Nogales International Wastewater Treatment Plant, in Rio Rico, Arizona. Originally designed to treat 8.2 million gallons of sewage each day, the 45-year-old plant currently treats up to 17 million gallons per day, releasing cleaned effluent into the Santa Cruz River north of the U.S.-Mexico border.

The IOI is in terrible condition: the unlined, unsupported concrete tunnel is riddled with cracks where groundwater seeps in and worn away in places to less than half its original thickness, according to a 2012 report by the International Boundary and Water Commission (IBWC). Untreated water escapes from the tunnel, carrying with it contaminants that include raw sewage, trash, and industrial wastewater laden with heavy metals. The IOI runs three feet below the Nogales Wash, a concrete channel that carries water to the Santa Cruz River. During storms sections of the IOI and Nogales Wash have failed, releasing untreated sewage and industrial wastewater into the valley’s aquatic system, according to a 2012 Arizona Department of Environmental Quality press release. Meanwhile, the Ambos Nogales population keeps outgrowing the sewage pipe.

Still, once treated, the water that the IOI transports is necessary for both human and non-human communities north of the border. This binational effluent makes up the bulk of the upper Santa Cruz River’s permanent flow, supporting a riparian ecosystem, providing habitat for the endangered Gila topminnow, and recharging drinking water aquifers for southern Arizona communities.

But the city of Nogales, Arizona, and the U.S. government have fought for years over who should pay to repair the disintegrating tunnel. In a 2013 budget request, the IBWC estimated that work could cost $100 million. (A spokesperson for the IBWC gave High Country News a cost estimate of $30 to $40 million and stated that the IOI posed no risk to human health or the environment.) While Mexico pays for treatment of much of its portion of the sewage that the IOI transports, neither the city of Nogales, Arizona, nor the U.S. government can agree to pay the remaining costs of the IOI. In 2004, a district court settlement ruled that the city of Nogales, Arizona would pay 23 percent of the treatment plant’s operating costs, even though it only produces about 14 percent of the sewage. It also ruled that the city must pay to replace the IOI.

The Nogales International Wastewater Treatment Plant in Rio Rico, Arizona, treats more than 17 million gallons of Ambos Nogales sewage carried by the International Outfall Interceptor a day, releasing the cleaned effluent into the Santa Cruz River.
PCL Construction

Unsurprisingly, Nogales, Arizona, denies full responsibility for the IOI. According to the Nogales International, in the last quarter of 2015, Nogales, Sonora, contributed 12.4 million gallons daily, while Nogales, Arizona, contributed 2 million gallons daily to the IOI. Nogales, Arizona, paid the IBWC according to how much sewage it contributed to the treatment plant. The IBWC called these “partial payments.”

Now, Arizona’s members of Congress have stepped in to try to establish, once and for all, who’s responsible for the IOI. On March 7, Republican Sens. John McCain and Jeff Flake introduced Senate Bill 551, the Nogales Wastewater Fairness Act. The next day Arizona Reps. Martha McSally, R, and Raúl Grijalva, D, introduced a companion bill in the House.

In a nutshell, the bills establish that the IBWC – which is part of the State Department and exists to manage boundary and water issues along the U.S.-Mexico border – must pay for IOI repairs and most operating and maintenance costs. The city of Nogales, Arizona, would only cover costs proportional to the sewage it produced. “Nogales residents should not have to pay for runoff and sewage not under their control,” McCain said in a statement.

A previous bipartisan effort to address this issue legislatively failed: In December 2016, a pair of amendments for IOI repairs, introduced by Grijalva and McCain, were stripped from federal water infrastructure bill.

In 2013, McCain and Flake wrote to then-Secretary of State John Kerry, urging actions on the IOI, citing concerns about severe flooding, high sewage volumes from Mexico, and blockages caused by drug smugglers. “If the [Nogales] wash and IOI fail,” the letter stated, “large swaths of the southern Arizona region could be affected by serious water contamination.

Arizonans rely on water from the IOI to keep the upper Santa Cruz River functional, so turning away Mexico’s water isn’t an option. Plans for how to fix the tunnel already have been designed; all that’s needed is the funding to build on the borderlands one construction project that will keep Ambos Nogales healthy. Until the money appears, the IOI will keep disintegrating, and monsoon storms will lead to more crumbled pipes and leaking sewage.

Maya L. Kapoor is an associate editor with High Country News.

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