Background

The city of Nogales provides water and wastewater service to local residents.  The Nogales International Wastewater Treatment Plant (NIWTP) provides wastewater treatment for the communities of Nogales, Arizona and Nogales, Sonora.  The International Outfall Interceptor (IOI) transports wastewater originating in both communities to the NIWTP, located in the area of Rio Rico, Arizona.  The treated effluent is discharged into the Santa Cruz River, where it forms a perennial surface water stream extending 16 miles from the NIWTP to the area of Tubac, Arizona.  This treated effluent is a valuable source of water for the preservation of an important river habitat and as a source of groundwater for downstream users.

Currently, there are structural and hydraulic capacity problems with the wastewater collection system, which allows excessive amounts of extraneous water to enter the system as infiltration and inflow, and also results in wastewater outflows to the environment.  In addition, the NIWTP is unable to meet newly established EPA effluent quality standards.

Description

This project will replace portions of the sanitary sewer system, as well as make improvements to the NIWTP.
 Nogales International Wastewater Treatment Plant

• The improved facility will have a capacity of 14 million gallons per day (mgd), and will accommodate flows from both Nogales, Arizona and Nogales, Sonora.
• The treatment process will now include the removal of ammonia nitrogen to reduce the toxicity of the effluent, especially for the aquatic species.

International Outfall Interceptor

The existing line which has deteriorated with age will be replaced to minimize extraneous flows entering the system and to increase hydraulic capacity to relieve surcharges in the system.

 Wastewater Collection System

Portions of the wastewater collection system in Nogales, Arizona will be replaced.

Benefits

By addressing the structural and hydraulic capacity problems of the wastewater collection system, this project will prevent excessive amounts of extraneous water from entering the system and causing overflows to the environment.  Also, by upgrading the international wastewater treatment plant, appropriate measures are being taken to protect the Ambos Nogales communities, now and for the future including maintaining and enhancing the aquatic ecosystem existing downstream of the plant.