The Nogales International Wastewater Treatment Plant is located in Nogales, Arizona, and discharges its effluent to the Santa Cruz River. A unique facility, the plant receives approximately 70% of the flow and load from Nogales, Sonora (Mexico), with the remainder from Nogales and Rio Rico, Arizona. With wastewater flows originating from two countries, a number of project complexities emerged, one of which was the number of project stakeholders, each with varying interests and priorities. They included the City of Nogales, the International Boundary and Water Commission (IBWC), the US Environmental Protection Agency, the Arizona Department of Environmental Quality, and NAD Bank.
For this design-build project, the PCL/Stantec team provided the only compliant bid and was awarded the project in 2007. The team completed the project on budget and well ahead of schedule despite an owner-initiated change order during the project that increased the plant capacity from 14 MGD to 14.74 MGD.
Because of the success of the project, the City and IBWC were able to construct sludge stabilization facilities and UV upgrades with the original project contingency, after previously removing them from the scope due to cost constraints. The sludge stabilization has resulted in significant cost reductions for the owner, with the payback estimated at less than five years.