Most Popular Change Type Size Nogales grapples with murky issue: Mexico’s sewage
Shaun McKinnon
The Arizona Republic
Feb. 25, 2007 12:00 AM
NOGALES – Every day, more than 14 million gallons of raw sewage rushes beneath the streets here through a pipeline crumbling from age and overuse.
The rancid stream carries waste from both sides of the border, starting from a dilapidated system in the other Nogales, a Sonoran city 20 times more populous than its Arizona sibling and just enough uphill to make retrieving the waste too costly. An antiquated treatment plant near Rio Rico, about an hour south of Tucson, swishes the water around and spits it into the Santa Cruz River, still 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. High flows could overwhelm the nine-mile main line and inundate streets and neighborhoods on the Arizona side, spreading disease and forcing thousands of people from their homes. advertisement
Ignored, the untamed wastewater undermines quality of life on both sides of the border, or Ambos Nogales, a term used to describe the two cities together. The Sonoran side continues to swell with people who add to the need for a modern system, but 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, and 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, Ariz., will start work next month on a $62 million upgrade to the treatment plant. The project will help the city meet the terms of a federal consent decree; it will not repair the deteriorating pipeline or address any of the 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.”
Among the most serious problems:
• Inadequate wastewater systems. Scores of colonias, the clusters of ramshackle homes, cling to the edge of the Nogales wash in Sonora. Most lack modern plumbing, so their drains and toilets empty directly into the wash, where storm runoff carries raw sewage into Arizona.
• Lax enforcement of environmental laws. Mexico has increased efforts to require pretreatment of hazardous wastewater, especially at the border maquiladoras, or factories. But some factories ignore the laws.
• Contaminated groundwater and surface water. The sewer lines on both sides of the border leak badly, but in Sonora, the system fails in numerous locations, releasing raw sewage into the aquifers and the wash. A sample of wash water in December found levels of fecal coliform so high they could not be counted using the typical measuring units.
• Outdated treatment systems. The 50-year-old International Outfall Interceptor carries waste from the border to the treatment plant. It leaks, allowing waste to escape and groundwater to seep in. The extra groundwater overwhelms the plant, especially during rains. Pressure in the main line has blown manhole covers into the air.
Although the waste stream has not contaminated drinking-water supplies, officials believe it could seep into shallow aquifers and contaminate wells in the area.
In March 2000, the Sierra Club filed suit alleging that the treatment plant was violating water-quality permits issued by the U.S. Environmental Protection Agency. A consent decree issued by the court mandated reductions in contaminant levels in the treated wastewater, mostly nitrogen and ammonia. High concentration of those organic materials can be toxic to humans, wildlife and aquatic systems.
“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.”
‘It has become our issue’
The truth is, 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 Sonoran 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, the Nogales mayor. “But now it has become our issue.”
Nogales, Ariz., uses less than one-third of the plant’s capacity but pays two-thirds of its $2 million annual operating cost, a disparity that persists even as Mexico tests limits on how much water it can send north. 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, and 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.”
For an operation with such an imposing name, the Nogales International Wastewater Treatment Plant cuts an unimpressive profile. It sits in a shallow basin off I-19, hidden by a row of produce warehouses. An electronic gate guards the entrance, but the plant itself offers no hint that it serves such a large population.
The main sewer line, the interceptor, ends at a concrete structure, where grit settles and a screen removes trash and other non-biological debris.
What remains flows into aerating and settling ponds, and from there the water is filtered, chlorinated, de-chlorinated and emptied into the Santa Cruz River, where it flows north for about 16 miles before percolating into the ground.
John Earl, the on-site construction manager for the upgrade project, moved his office to the plant earlier this month to oversee site preparations. Earl, an engineer for the international firm of Faithful-Gould, said the politics and the issues between the two countries do not matter once the front gates close behind him.
“This is a standard-issue plant,” he said. “Nothing much special.”
The upgrade will improve water quality and bring the effluent into compliance with EPA standards, Earl said. But the upgrade will not solve two significant problems:
• The main delivery line, the International Outfall Interceptor, needs to be replaced. That project would cost as much as $40 million, and the city says it does not have the money. Until the line is replaced, problems such as groundwater infiltration, spills and storm-caused floods will remain, problems the plant upgrade can’t solve.
• Contaminated wastewater continues to flow into the Nogales Wash, mostly on the Mexican side.
‘A mixed blessing’
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 that 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.”
But somebody is using it, or, rather, some things. The effluent from the treatment plant flows down the usually dry Santa Cruz River and helps sustain a vibrant riparian system that would not exist otherwise.
At first glance, the river looks like any other as it gurgles past Santa Gertrudis Lane outside Tumacacori. Winter has stripped the trees of their warm-weather wardrobe, but green plants still hug the banks and watercress floats on the surface in some places.
Then the wind shifts, carrying an unmistakable odor.
“It’s a mixed blessing, but a blessing,” said Sherrie Sass, one of the founders of the Friends of the Santa Cruz. “Without what comes out of the plant, there probably wouldn’t be any water here on account of groundwater pumping.”
The group collects water samples from the river monthly, mostly below the plant. They have found chlorine, nitrates, nitrites, phosphates and ammonia, among other contaminants. Levels of nitrates and ammonia have risen steadily in recent years as flow into the treatment plant tested its limits.
Sass reviewed recent reports from water taken in the Nogales Wash, not far from the treatment plant. Below the plant, levels of fecal coliform, an indicator of raw sewage, were low. At another location, above the plant, the reading was “TNTC” – too numerous to count.
Upgrading the plant will improve water quality in the river significantly, Sass said, but the water will remain contaminated until Mexico addresses more serious issues on its side of the border. The Nogales Wash still bypasses the plant and it still carries polluted water from Sonoran streets and colonias.
The Arizona Department of Environmental Quality also monitors water quality at the border and has charted contamination from the wash as it enters the state.
“We’ve seen a lot of unauthorized discharges into the Nogales Wash,” said department director Steve Owens. “We’ve seen leaks in the interceptor, rain events that cause overflows of raw sewage into the wash. We’ve had emergency situations where we’ve had to buy bags of chlorine to disinfect the wash.”
Owens said efforts to improve water quality run into the same border issues that have stymied other agencies.
“In the past there have been commitments from Mexican authorities to do monitoring and assessment work,” he said. “The level of commitment comes and goes depending on what’s happening on the Mexican side of the border. The Number 1 concern we have is that drinking-water supplies on the Arizona side are not affected, and so far they have not been.”
Along the Santa Cruz, when the wind shifts, most people would not guess the source of the water. The nearby Juan Bautista de Anza Trail attracts thousands of visitors. The National Park Service recently bought a stretch of the river that is already popular among birdwatchers.
“Riparian vegetation is so adapted to flood and drought regimes here, it’s hard to kill, as long as you have hydrology,” Sass said. “It will survive, even if the water’s polluted, and we’re really grateful for it.”