The $66-million upgrade on the Nogales International Wastewater Treatment Plant in Rio Rico, Arizona, near the Mexican border has been completed. The facility, which discharges 15 million gallons of wastewater to the Santa Cruz River everyday can now comply with all the required permit limits for suspended solids and better serve the 200,000 residents of Nogales, Arizona and Nogales, Sonora. The US Environmental Protection Agency (EPA) marked the development with a ceremony last Wednesday (June 24).

Prior to the upgrade, the facility has been using an aerated lagoon system since 1991 to treat the sewage from the Nogales communities. The technology failed to meet state permit limits, thus allowing the facility’s discharge to badly affect the Santa Cruz River. The river is home to the Gila topminnow (poeciliopsis occidentalis), an endangered, live-bearing, guppy-like fish.

A federal consent decree was issued in 2001 ordering facility owners, the city of Nogales and the International Boundary and Water Commission (IBWC), to meet discharge permit limits. Engineers from the state, the national government, and the University of Arizona helped the plant to develop and implement a solution. Presently, the treated wastewater discharged by the upgraded facility to the Santa Cruz River already has a “significantly improved clarity” and lower concentrations of organic and ammonia compounds.

“We’re celebrating completion of this project which dramatically improves water quality in the Santa Cruz River. Local citizens have already noticed the difference,” said EPA’s Pacific Southwest Region Water Division director, Alexis Strauss.


-  Jen Balboa

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Sources:

¹ http://ecos.fws.gov/speciesProfile/profile/speciesProfile.action?spcode=E00C
² http://yosemite.epa.gov/opa/admpress.nsf/3881d73f4d4aaa0b85257359003f5348...