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Press Release
Water Quality

Nogales, Arizona (August 12, 2022) — Officials with the Arizona Department of Environmental Quality (ADEQ) and Santa Cruz County continue to caution against contact with water in the Nogales Wash and Potrero Creek due to ongoing intermittent transboundary sanitary sewer overflows (SSOs), in addition to elevated levels of pollutants that may be present during any storm event resulting in increased runoff.

Due to recent and ongoing monsoon activity there have been several instances of transboundary flows of surface water from Nogales, Sonora to Nogales, Arizona. Most of this flow is typical stormwater runoff. However, a portion of the flow is due to intermittent SSOs, which occur in Nogales, Sonora, when stormwater and debris overwhelm the local sanitary sewer. The volume of wastewater that may have reached Santa Cruz County is unclear and ADEQ is continuing to coordinate with the U.S. section of the International Boundary and Water Commission (IBWC), the utility in Nogales, Sonora, the City of Nogales, Arizona, and Santa Cruz County to assess current risks and provide ongoing technical assistance.

The U.S. and Mexico sections of IBWC are also in contact with the utility in Nogales, Sonora, which is working to resolve factors contributing to the intermittent SSOs. During storm events, water levels may be higher than normal in local washes. Normally, there is persistent low flow in the Nogales Wash from a natural spring, plus water runoff and discharge originating in Nogales, Sonora. This water is not due to an SSO, but an SSO can mix with this water.

As is the case with most high volume runoff storm events, ADEQ urges people to avoid accessing local washes in this area. This recommendation is based on potential health risks to people and animals from contact with typical storm runoff,which contains elevated levels of pollutants and the additional concerns posed by wastewater originating from the intermittent SSOs. Both storm runoff and SSO wastewater carry pathogens that pose a risk to human health and the environment. People and animals that come into contact with these types of water are at risk of infection from those pathogens.

Recommended Actions:

  • Avoid contact with the water in this area, including wading, drinking and washing. If you have contact with the water, rinse using soap and clean water immediately.
  • Take care that pets and livestock do not drink potentially affected water. Pets can be especially susceptible because they tend to drink while in the water and lick their fur after exposure. Rinse pets using soap and clean water.
  • If you think that your health or that of your pet or livestock has been affected from exposure to impacted waters, seek medical treatment immediately. Be sure to tell the medical professional about contact with the SSO. Also, make sure to advise your local county public health department about the exposure details.


Santa Cruz County Health Services Agency | View >


ADEQ Public Information Officer
602-540-8072 | Email >

Santa Cruz County Public Information Officer
520-375-8285 | Email >