The City of Memphis has owned and operated the T.E. Maxson Wastewater Treatment Facility (Maxson WWTF) since its construction and startup in 1975. The facility provides wastewater treatment for the southern portion of the City’s service area, treating both industrial and domestic flows. The facility treats an average flow of 72 million gallons per day (MGD) and has a peak hydraulic capacity of 170 MGD. In 2018, the City and CDM Smith Constructors began construction of the Maxson WWTF Process Upgrades project using the construction manager at risk (CMAR) collaborative delivery approach. The project consists of five guaranteed maximum price (GMP) packages, each focusing on improvements to different elements of the facility. The first two construction packages, completed in 2020 and 2021 respectively, included the construction of a disinfection tank, effluent hydraulic improvements, and an overhaul of the plant’s electrical system in GMP1, and the replacement of the existing coarse bar screens at the Headworks facility with new climber screens and washing presses for GMP2. This presentation will provide an overview of the improvements constructed as part of GMP3 and GMP4, which are scheduled for completion in the spring of 2024. Work included in GMP3 affected nearly every process within the facility. The coarse-bubble diffusers in the plant’s 28 aeration basins were demolished and replaced with fine-bubble diffusers. Two new 135-foot diameter final clarifiers were constructed at the effluent end of the plant, along with scum pumps and a new return activated sludge (RAS) pump station dedicated solely to the new clarifiers. A flow diversion structure was installed to improve plant hydraulics downstream of the trickling filters and upstream of the aeration basins. Finally, fiberglass reinforced plastic (FRP) ductwork systems were installed to provide odor control treatment for facilities throughout the plant. Constructing and commissioning all these improvements while minimizing impacts to plant operations is a significant challenge. Most of the improvements included in GMP4 are intended to improve the biological treatment process by providing supplemental oxygen to the RAS flow before it is returned to upstream plant processes. A RAS Reaeration Basin, outfitted with fine bubble diffusers, was constructed in a constrained area within the existing plant footprint. A new Blower Building with three 1,250-HP blowers dedicated solely to the RAS reaeration process was constructed adjacent to the new basin. Miscellaneous modifications to yard piping and flow distribution structures, along with new prefabricated electrical buildings, were also associated with GMP4. Supply chain issues, changes in influent water quality, and coordination between a wide array of equipment suppliers and subcontractors have all presented challenges during the construction of GMP3 and 4. This presentation will provide details on each upgraded facility within the plant and discuss several of the challenges that have arisen during the multi-year construction project, and strategies to mitigate those challenges.