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Nogales plant overloaded with neighbor’s sewage

The Arizona Republic


The Arizona Republic

NOGALES – Every day, more than 14 million gallons of raw sewage rush beneath the streets here through a pipeline crumbling from age and overuse.

The rancid stream carries waste from both sides of the border. It starts from a dilapidated system in the other Nogales, a Mexican city 20 times more populous than its Arizona sibling and just uphill enough to make retrieving the waste too costly.

An antiquated treatment plant near Rio Rico swishes the water around and spits it into the Santa Cruz River, unfit even for fish.

Along the way, waste seeps out of a leaky collector system and contaminates the aquifer and the Nogales Wash, a cross-border tributary to the Santa Cruz that bypasses the treatment plant.

Ignored, the untamed wastewater undermines quality of life on both sides of the border. The Mexican side continues to swell with people who add to the need for a modern system. Without it, neither city can attract the investment required to sustain the economy.

Governments at every level in both countries know about the wastewater and the risks it poses. They have discussed dozens of possible solutions, prodded by environmental groups, health organizations and courts.

So far just one idea has survived nearly a decade of talks. Using hard-fought grant money, Nogales is about to start work on a $62 million upgrade to the treatment plant. The project will help the city meet the terms of a federal consent decree, but it will not repair the deteriorating pipeline or address any other problems.

The long-term question of how to deal with 5 billion gallons of wastewater a year remains mired in politics and a sticky web of conflicting laws and treaties. Adding to the confusion is an evolving view of the waste stream, which has helped restore a riparian area in Arizona and could provide a badly needed water source for the growing border region.

“We’ll probably never see an end to the issues,” said Nogales Mayor Ignacio Barraza, who was elected last fall. “But we can’t say because it originates in Mexico, it’s not our problem. This is our health and economics and safety, our quality of life.”

Although the waste stream has not contaminated drinking-water supplies, officials believe it could seep into shallow aquifers and contaminate wells in the area.

“We know it’s a tremendous undertaking,” said Joy Herr-Cardillo, who monitors progress at the Arizona Center for Law in the Public Interest. “If this situation existed anywhere else in this state, it wouldn’t have been tolerated so long.”

The situation probably could not exist anywhere else in Arizona.

Nogales clings to the desert hills at the end of Interstate 19, a city shoehorned into a narrow valley along the Santa Cruz. About 20,500 people live on the Arizona side of the border; as many as 400,000 people, perhaps more, live on the Mexican side.

The river flows north, downhill into Arizona from Mexico, an unexpected reversal of the rule that north is up and south is down. In that quirk of geology lies the real culprit in the two cities’ wastewater troubles: gravity.

“If the water didn’t flow from south to north, if we didn’t have to treat Mexico’s wastewater, we wouldn’t be in this situation,” said Barraza. “But now it has become our issue.”

Nogales uses less than one-third of the plant’s capacity but pays two-thirds of its $2 million annual operating cost. Mexico pays based on the cost of treating waste in its country and has resisted efforts to adjust that formula.

The two cities were once served by one water system, on the Arizona side. As wastewater became an issue, the cities again looked for one answer. In 1951, working with the International Boundary and Water Commission, the two countries opened a shared plant. The plant was expanded twice since then, but it always struggled to keep up with the flows.

“When they first decided to build the plant, we argued that they were underplanning,” said Michael Gregory, executive director of Arizona Toxics Information, a group that worked on behalf of Nogales residents. “We knew the growth rate in Sonora was going to be higher, yet they underbuilt each time.”

Fixing infrastructure also will not solve the broader issue of whether the treated effluent could be used to fill water needs in the growing region.

Terry Sprouse, a senior research analyst for the University of Arizona’s Water Resources Research Center, said the border muddies the question.

“Mexico retains the rights to the effluent based on the 1944 treaty,” Sprouse said. “Legally, they could stop it at the border.”

Gravity makes that unlikely.

Because Mexico legally owns the effluent, it can’t be used in Arizona by developers who need to prove a 100-year water supply. Sprouse said some lawyers would argue once the water percolates into Arizona’s aquifers, it belongs to Arizona. But Mexico would probably dispute that.

“Technically,” he said, “nobody should be using it.”

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