Metro Water Services (MWS) is expanding and upgrading their treatment plants through the Advancing Metro Water project. This is a once-in-a-generation project that involves increasing the capacity of the Omohundro Water Treatment Plant (OMO WTP) in Nashville, TN, from 90 mgd to 150 mgd. This includes adding new pretreatment and chemical feed systems. Given the challenges with the existing filters and a desire to keep the plant operational, a new filter facility would be constructed with state-of-the-art filters. Built in the 1920s, the filters are a stunning example of craftsmanship and thoughtful design in public works that is one of the few water treatment facilities on the United States National Register of Historic Places. Features that make this facility an architectural centerpiece of the plant are the terrazzo floors, brick arcades along the filter deck, and high arched ceilings. However, rather than a museum piece, the existing historic filters will continue to be an integral part of the treatment process. As MWS modernizes and introduces new processes at OMO WTP, the original structural will converted to new post-filter granular activated carbon (GAC) contactors. Filters originally constructed in the 1960s had to be demolished to allow for construction of new facilities. Testing led to an empty bed contact time (EBCT) of 10 minutes at plant. As a result, the existing filters do not provide what is required for deep media contactor. Tools like rate-of-flow control, contactor-to-waste, features for tracking and optimization of GAC performance, and the ability to minimize waste water provide operational functionality. An innovative GAC media replacement system and access to equipment is desired for simplified maintenance. All of these changes resulted in substantial modifications to the existing building. However, this facility is to maintain the original visual features of the building architecture. Behind the original brick façade, the process requirements will change dramatically, requiring significant renovations to the structure and careful coordination. The existing clearwell below the filters will be demolished to allow for new walls to allow for deeper bed contactors. Structural design of these elements are to be carefully considered by engineer and contractor to avoid impacts to the exiting above grade structure. Piping in the center gallery will be removed and replaced with new inlet piping. External galleries are to be added to allow for better access to underdrains and construction of finished water and backwash piping. From an aesthetic perspective, the building will appear unaltered. This presentation will discuss the creative solutions that emerged from collaboration between MWS, design engineers, architects, and the construction manager to preserve historic elements while executing substantial modifications. Through careful planning, coordination, and outside the box thinking, a once in a generation overhaul of a historic building will preserve both the facility’s historic while providing robust process criteria, operational flexibility, and ease of maintenance.