The Arizona Department of Environmental Quality (ADEQ) and local officials confirmed an intermittent sanitary sewer overflow (SSO) in a tunnel under the international border, which transports stormwater from Nogales, Sonora to Nogales, Arizona. A SSO is a release of untreated wastewater and contains raw sewage.  

When flowing, the SSO originates from Nogales, Sonora and is exiting the tunnel into the Nogales Wash about one mile north of the international border. Depending on volume of flow and frequency, the SSO could reach the Santa Cruz River.

The Arizona Department of Environmental Quality (ADEQ) is issuing a High Pollution Advisory (HPA) for fine particulate matter (PM-2.5) effective December 23 & 24 in Nogales. PM-2.5 is made up of small particles (soot) found in smoke. ADEQ recommends that people limit outdoor activity while the HPA is in effect, especially children and adults with respiratory problems.

Access the latest air quality forecast information at:

ADEQ Air Quality Hourly Forecast


The recent flows from summer monsoon rains have eroded embankments at a number of locations within Nogales Wash, exposing and threatening critical infrastructure and property. The U.S. Army Corps of Engineers (USACOE) is working to stabilize banks along the Nogales Wash.

The Arizona Department of Transportation delivered 70, 20-foot sections of concrete barrier to assist in the erosion mitigation along the banks of the Nogales Wash.

Officials with the Santa Cruz County Emergency Operations Center received an update from the United States Section of the International Boundary and Waster Commission (USIBWC). At 2 a.m. on August 2, crews in Nogales, Arizona completed installation of a bypass system to divert sewage that had been leaking from the partial breach. The sewage is now being conveyed for treatment at the Nogales International Wastewater Treatment Plant and is no longer flowing into the Nogales Wash.

Progress is ongoing in repairing the partial breach in the International Outfall Interceptor (IOI).

Officials ask that the public refrain from entering this area to allow agencies representatives to conduct their surveys and for the safety of the employees working in the area.

The Nogales International Airport has issued a Notice to Airmen (NOTAM) for a one nautical mile around the worksite. Officials have requested that drone use be restricted in the areas crews are working.

The United States Section of the International Boundary and Water Commission (USIBWC) is investigating a leak from the International Outfall Interceptor (IOI) and is participating in the repair of leak. The leakage has been identified as occurring at manhole 89 which is approximately seven miles from the International Boundary. The IOI conveys the City of Nogales, Arizona’s sewage along with Mexican sewage to the Nogales International Wastewater Treatment Plant in Rio Rico, Arizona.

Governor Doug Ducey today declared a state of emergency following the rupture of a sewage conveyance pipeline near Nogales, Arizona and sent a letter of request to the U.S. Army Corps of Engineers asking for assistance in flood and damage mitigation efforts. The emergency declaration follows similar declarations from Santa Cruz County and the City of Nogales and makes available additional state resources for the response effort.

The La Sierra fire is burning in the Nogales Ranger District of the Coronado National Forest, approximately 9 miles west of Nogales, Arizona.  The fire is approximately 4,900 acres and is estimated at 30 percent contained. 

Seven crews are working on the fire line. Three helicopters continue to support firefighting efforts on the ground by dipping water from Pena Blanca Lake to provide water drops from buckets suspended below the helicopters. Additionally two air attack platforms are assigned to the fire to provide aircraft coordination and communication with ground forces.


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