The scope of work includes, but is not limited to the following: 1.Architecture - The two cooling towers are located in a 'courtyard' portion of the building roof that is surrounded on three sides by exterior walls, the east side of this roof courtyard is a screen wall constructed of vertical steel members that supports a steel-louvered screen wall, which is in fair to poor condition. The louvered screen wall and associated vertical support structure shall be replaced in its entirety. The larger steel columns and beams will remain. The existing steel louvers shall be replaced by light-weight pre-finished pre-manufactured aluminum louvered panels, 4 feet x 12 feet in size, to match existing. The vertical support channels every 3 panels shall be replaced by new vertical structure constructed of two steel angles welded together. This structure shall be separated from the aluminum louvers by rubber/neoprene flashing to prevent long-term corrosion that can be caused by the variance in metals. All new or existing to remain steel shall be sanded/grinded down and painted with Kynar or a high performance coating. All pipe penetrations at the new and/or replacement piping shall be resealed at the roof and interior locations for moisture and thermal protection, and fireproofing. 2. Structural - The existing cooling tower support framing in the 'courtyard' portion of the building roof shall be replaced to accommodate the new cooling towers. The existing primary W30 and W24 framing members will be refurbished and remain in place. The existing vertical and horizontal channels supporting the louvered screen wall shall be removed and replaced. The new steel framing will be designed for current wind loadings per ASCE 7-16. The existing equipment pads located in the mechanical room shall be repaired and extended. New equipment pads will be installed as required for new mechanical equipment. 3. Mechanical - The two (2) existing centrifugal chillers and their associated housekeeping pads shall be removed and replaced with new, high-efficiency magnetic bearing chillers. The magnetic bearing chiller will come with an integral VFD to modulate compressor speed which provides capacity control while the integral control system varies the diffuser geometry increasing system efficiency. The two (2) existing cooling towers shall be removed and replaced with high efficiency cooling towers with stainless steel construction and variable speed direct drive tower fans. The two (2) existing condenser water pumps, two (2) chilled water pumps, and their associated inertia bases shall be removed and replaced, as well as all the associated condenser water piping and chilled water piping and specialties within the mechanical room. The existing chilled water and condenser water chemical treatment systems shall be removed and replaced. A side-stream filtration system shall be added to the condenser water loop to extend the life of the condenser water system and provide more efficient heat transfer. New variable frequency drives shall be provided for each new pump. The existing refrigerant exhaust fan, associated ductwork, and refrigerant monitoring system shall be removed and replaced. The existing refrigerant relief piping shall be reused to the extent indicated with new piping connecting to the chillers. The new refrigerant exhaust system will be sized based on the volume of refrigerant in the new chillers. All new equipment and control valves and devices shall be provided with adequate controls interface to integrate into the facility's existing to remain building automation system (BAS). The new condenser water piping located outdoors shall be insulated and provided with heat tracing to prevent freezing. Temporary cooling will be provided by two (2) 300-ton air cooled chillers located in the parking lot adjacent to the access hatches to the mechanical room or in another location as approved by USPS. Temporary chilled water piping will be routed from the chillers down through the access hatch and tie into the existing chilled water piping in the mechanical room. 4. Electrical - The existing motor control center (MCC-1) and all associated breakers, conduit, conductors, and disconnect switches serving the existing mechanical equipment being removed shall be demolished. Three (3) new breakers shall be installed in the existing main switchboard (MSB) to supply the chillers and MCC. Provide new conductors, conduit, and safety disconnect switches for (2) chillers. Install new MCC-1 with (14) new circuit breakers/contactors and provide new conductors, conduit and safety disconnect switches to supply the (2) chilled water pumps, (4) cooling tower fans, (2) condenser water pumps, and (1) refrigerant exhaust fan, existing AHU-17, existing EF-13, side stream filter, and heat trace freeze protection. New branch circuits and duplex receptacles shall be included for new BAS control panels and heat trace system as required. Modify existing lightning protection system at cooling towers and louvered wall.