Los Alisos

A pipeline leads into the still-under-construction Los Alisos wastewater treatment plant in Nogales, Sonora in this slide included in a 2012 presentation by Octavio Gastelum Ceballos, then-director of the city’s water utility known by its Spanish acronym OOMAPAS.

Authorities have finally identified the source of the intermittent flow of untreated wastewater containing raw sewage from Nogales, Sonora into the Nogales Wash, but have yet to stop the problem.

As of Thursday morning, only one of five pumps were functioning to pump water into the Los Alisos Wastewater Treatment Plant in Nogales, Sonora, causing a feeder pipeline to back up, according to Lori Kuczmanski, spokeswoman for the U.S. Section of the International Boundary Water Commission.

“The pumps are about five years old and the inspection revealed that they are worn out due to excessive grit and they’re not being maintained,” Kuczmanski said, adding that during heavy periods of water flow, “the pipeline can’t handle the water and it’s overflowing into the Nogales Wash.”

Kuczmanski was unable to say when the problem would be resolved, since workers are having to clean the pumps manually.

“The solution to this, they think, is that a grit basin ahead of the wet well would prevent any grit from getting into these pumps, so the pumps don’t get clogged up,” she said.

The Arizona Department of Environmental Quality announced on Jan. 25 that untreated wastewater containing raw sewage was being intermittently released into a tunnel that transports stormwater across the border, then exiting the tunnel into the Nogales Wash approximately one mile north of the border. 

Kuczmanski said Thursday that the wastewater is still being intermittently released into the wash during high water usage periods in Nogales, Sonora, such as in the morning when people get ready to start their days and in the evening when they return home.

The $19.3-million Los Alisos treatment plant was meant to provide treated water to more homes and neighborhoods in Nogales, Sonora while also taking some of the pressure off the Nogales International Wastewater Treatment Plant in Rio Rico, which processes sewage from both sides of the border.

At the time of its inauguration in August 2012, it was praised by officials from both sides of the border as a model for Mexico and the rest of Latin America.

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