Over several years, the Gold Bar Waste Water Treatment Plant upgraded its secondary treatment facility to a tertiary (BNR) treatment process. The Bioreactor Upgrade Project was a significant part of the service expansion. The project involved the conversion of the existing 40 bioreactor cells to the BNR process, retrofitting the secondary clarifiers and performing significant upgrades to the piping systems in the tunnels throughout the plant. Maple Reinders’ crews fabricated, installed and/or retrofitted over 60,000 fine bubble aeration diffusers, 15,000 feet of stainless steel air piping, 6,000 feet of standard steel process piping, 100 mixers, 28 pumps, 88 slide and weir gates and a completely new Delta-V controls system. The project was expected to take 18 months to complete. Although progress of the project was complicated by the fact that only two secondary process trains could be out of service at any given time, work progressed rapidly and early completion was achieved.