For the people of Nogales, Arizona, the sight of an approaching storm has become something to dread.

Water pouring onto the drought-parched desert of southern Arizona is great. All that water flowing into – and overflowing out of -- the fast-disintegrating waste-water sewage system the community shares with Nogales, Mexico, is the stuff of nightmares. Rapidly worsening nightmares that may cost tens of millions of dollars to properly fix.

As a part of the long-running effort to resolve the sewage issues, the co-owner of the area’s sewage-treatment facility, has announced plans for a public meeting in the town of Tubac on September 13.

The purpose of the forum, sponsored by the U.S. Section of the International Boundary and Water Commission, or USIBWC, will be to promote the exchange of information between the USIBWC and the community regarding Commission projects and related activities in Pima, Cochise, and Santa Cruz counties. Specifically, the discussion will air issues regarding source metals that are being found in Nogales wastewater, as well as the health of the Santa Cruz River.

The Nogales sewage problems begin with a woefully over-taxed 8.8-mile sewage-drainage system known as the International Outflow Interceptor, or “IOI.”

At times, especially during storms, millions of gallons of untreated sewage have been spilling out of breaks in the nearly 70-year-old IOI and elsewhere in the system. In July 2017, the IOI ruptured under the strain of storm water surging up from Mexico, which, as reported by the Arizona Daily Star, spilled “raw sewage into a tributary of the Santa Cruz River and [caused] a significant spike in E. coli bacteria levels near the breach.”

And not just human waste, either. Untreated industrial wastes from Nogales, Mexico – which include regulated mater­­­­ials such as cadmium, lead, copper and zinc -- have been discovered in “significant levels” in the wastewater. The pollutants are contaminating the Nogales Wash, under which the IOI is buried, as well as water leaching into the Upper Santa Cruz aquifer and the Santa Cruz River itself.

Health officials, including those from the Arizona Department of Environmental Quality, now believe that the overtaxed wastewater system is becoming a serious environmental threat to the health of the river, to say nothing of the thousands of Arizonans that rely on groundwater wells tapping into the area aquifer.

The Santa Cruz relies heavily on treated effluent from the Nogales International Wastewater Treatment Plant, or NIWTP, near Rio Rico. Co-owned by the U.S. Boundary and Water Commission and the City of Nogales, Arizona, the plant is designed to treat nearly 15 million gallons of water daily, which accounts for about 38 percent of the Santa Cruz flow at that point.

Roughly 10 million gallons of that daily capacity are allocated to Nogales, Sonora, a much larger community (pop. 212,500) than Nogales, Arizona (pop. 20,000). On the U.S. side, Nogales and Rio Rico are allocated 4.84 million gallons of capacity. Annually, Nogales, Arizona, uses just 12 percent of the IOI system providing the as-yet untreated sewage to the plant, while the vast majority of the rest flows north across the border from Sonora.

At the September 13 public meeting in Tubac, a hydrologist from the Arizona Department of Environmental Quality will talk about metals in wastewater treated at the NIWTP.

The meeting also will include a presentation by representatives of the Sonoran Institute on the health of the Santa Cruz River.

Who: The International Boundary and Water Commission United States Section

What: A southeast Arizona citizens forum

When: Thursday, September 13; 3 – 5 p.m. 

Where: Tubac Community Center; 50 Bridge Road; Tubac, Arizona 85646