This generational project took place in one of the largest office buildings in the country which houses clinical research and associated facilities including patient and animal care, offices, conference rooms, storage areas and others. The facility requires city water service to supply both laboratory and domestic water services to these locations. Several main isolation valves had failed thus requiring replacement. The project required GMS to replace fourteen primary isolation valves on the domestic water system within a twelve-hour, overnight window. Work had to be completed within the time frame to allow for normal operations of the clinical center to resume on schedule. During the project, GMS worked to dismantle, remove and install fourteen 6-inch to 10-inch butterfly and open stem & yoke gate valves. Several valves were located in confined spaces which added a layer of complexity to the project. GMS performed the planning and rigging and then used multiple crew teams to drain the system and perform the valve replacements throughout the building. Once the system was filled, GMS performed leak tests on all valves and after completion, the customer was able to resume business as usual.