Background

The operation and maintenance of the wastewater collection system is the responsibility of OOAPASN, while the sewage is treated in the Nogales International Wastewater Treatment Plant (NIWTP) in Rio Rico, Arizona.

The wastewater system currently has about 27,300 connections, providing service to 80% of the city. Some neighborhoods located to the east and southeast of the city are not connected to the system. However, the system is working at full capacity, as the lines were designed for a smaller population. As a result, the current sewer mains are too small to
accept additional flows from new urban developments.

Most of the wastewater collection lines have exceeded their useful life and are in various stages of deterioration. It is estimated that OOAPASN has to make 200 monthly sewer repairs in addition to routinely scheduled maintenance. Moreover, the continuous build up of silts in the pipes, as well as increased flows from storm water during the rainy season further reduce the system’s capacity.

These problems have given rise to chronic sewage spills that run down streets or puddle in open areas. Eventually the untreated wastewater runs off into the Nogales Wash, thus posing a health risk to the residents of both Nogales, Sonora and Nogales, Arizona.

Description

The project consists of the rehabilitation of approximately 30 kilometers (18.7 miles) of primary and secondary sanitary sewer lines, which covers almost the entire wastewater collection system. All the work will be carried out in developed areas that already have water and wastewater systems.

Benefits

Replacing deteriorated sewer lines and mains will help prevent ground and surface water contamination by eliminating potential sewage overflows and leaks, thus providing a healthier environment for residents in and around Nogales, as well as across the border in Arizona. In addition, the project is expected to reduce storm and ground water infiltration into the sewer system.