DIA ATCT Modernization

GENERAL The work described here is representative at best and is not all-encompassing of the project scope modernization and refurbishment of the Federal Aviation Administration's Airport Traffic Control Tower (ATCT) and Base Building located at the Denver International Airport. The ATCT is a 24/7 operational facility. This project is to complete the facility modernization; most of the work in the upper floors of the ATCT was completed before the original construction contract was terminated due to COVID in 2020. The ATCT and Base Building are constructed of architectural precast concrete panels. The ATCT panels cover cast-in-place concrete up to 240 feet in building elevation and above this level, the tower is constructed of precast panels over structural steel. Adjacent to the ATCT is the 3-story Base Building and the Mechanical / Cooling Tower Building. Coordination will be required with all Mechanical, Plumbing, and Fire Suppression refurbishment and replacement work, along with movement of parts, equipment and labor when using the ATCT's elevator. Periods of sustained elevator usage will need to be coordinated with the facility so as to avoid impacting air traffic operations. Refurbishment will be designed and sequenced to prevent interruption of operations in the Base Building and ATCT, and may include night work. Any required interruption of services will require advanced scheduling and coordination with the responsible authorities and managers of the FAA and in some case the Denver International Airport. Estimated value is between $5,000,000.00 and $10,000,000.00. Architectural Work includes: Replacement of all interior finishes in the Base Building and stairways with Class A finishes. Penetrations and openings at fire-rated floor and wall assemblies will be repaired with the appropriate fire-stopping assemblies. Repair and refinishing of the exterior soffit at the ATCT Junction Level, approximately 22 stories above ground level Remodel Base Building restrooms and break rooms to meet ABA/ADA requirements. ABA/ADA compliant signage will be provided inside and outside of the stair enclosures. Handrails and metal stair tread riser panels will be added between ground level and junction level to the existing fire exit stairs in the ATCT. Replace new room signage in both the Base Building and ATCT. Remediate mold contamination, previously identified at interior walls and at perimeter unit heaters. Replace drywall in areas where it has been damaged by water, primarily due to leaking mechanically/plumbing systems. Replace backflow preventer, hose bibs, and valves. Remove and relocate water heater and mop sink, necessary to accommodate mold remediation work. Water closets, sinks and water coolers will be replaced and installed in compliance with the ABA/ADA accessibility requirements. Remediate exterior sealant joints at the 2nd Floor Base Building window perimeters due to water infiltration with a weeped two-stage joint added at the architectural concrete panel joints at the windows heads of the north and west facing windows. Fire and Life Safety Work includes repair or replacement to existing fire-rated walls and door assemblies, adjustment or replacement where damaged or deficient in order to restore fire ratings. Listed firestop assemblies will be provided where missing at all rated barriers. Provide UL approved fire-stopping assemblies at penetrations of fire rated walls and floor assemblies. Replace fire rated doors with full flush steel construction, minimum 1-3/4 thick. All exterior hollow metal doors and frames will be galvanized and insulated meeting NFPA 80 requirements. Provide flush, solid core wood doors with paint, veneer, or plastic laminate clad finish to match facility standard and meeting NFPA 80 requirements. Access Doors: Replace existing floor hatch at Cable Access level with fire rated hatch. Replace existing door knobs with ADA-ABA compliant levers. Provide power assist door openers and door closers at fire rated door assemblies and meeting NFPA 80A requirements. Install pre-finished steel semi-recessed Fire Extinguisher cabinets with solid doors and magnetic flashlight. Install stair access and fall protection atop of the diesel fuel tank and a guardrail around the access hatch to the cooling towers. Fire Suppression work includes: Maintenance and service to all existing fire suppression riser assemblies including new gaskets, valve packing replacement and verification of each risers operation. Provide releasing modules at each pre-action riser assembly. Install butterfly valves above each pre-action riser assembly. Replace sprinkler head escutcheons in ceiling. Provide automatic chemical suppression system at one (1) break room in the Base Building with a range hood with manual electric disconnect and manual suppression system activation. Replace existing ATCT fire pump. Add damper control and damper control strategy through DDC to the ATCT Stairwell as well as the fire alarm system. The sequence will interrupt the stair pressurization to allow occupancy. Fire Alarm work includes: Relocating the smoke detector in the supply ductwork of AHU-1 to be upstream of the duct humidifier. Fire alarm system devices where affected or modified, will be coordinated with the FAA Building Management and the local fire alarm control panel to avoid all trouble/alarm signals. The existing Fire Alarm System will be modified and/or expanded to include additional fire detection devices, release of sprinkler system detection, and notification devices including strobes, and combination horn/strobe appliances where deficiencies have been identified. The system devices will be addressable, non-coded, with sufficient capacity for required coverage. Manufacturer type will be compatible with existing system. Mechanical work includes: Below is a list of major mechanical equipment that is to be replaced as part of this project. This equipment will be identified in the project design documents and is not all encompassing of the project scope: Replacement of existing Air-Handling units in the Base Building. Replacement Existing Boiler units and Control Panels in the Base Building. Replacement Existing Hot Water System Pumps in the Base Building. Replacement Existing Exhaust Fans in the Base Building & ATCT. Replacement Existing Unit Heaters in the ATCT pipe chase. Replace AHU-1 on a one-for-one basis in the Base Building. Replace AHU-2, AHU-3, and AHU-4 and all ancillary devices with CRAC units of similar capacity in the Base Building. Replace AHU-5 and AHU-6 and all ancillary devices with vertical air handling units of similar capacity in the Base Building. Replace AHU-7 and AHU-8 and all ancillary devices with CRAC units of similar capacity in the Base Building. The supply air will be ducted above the ceiling to supply diffusers to better distribute airflow between racks of equipment. Replace AHU-11 and AHU-12 and all ancillary devices on a one-for-one basis on the Sub-junction level of the ATCT. Provide temporary, portable AHUs and ducting during the replacement. Remove portion of wall at sub-junction level to allow for replacement of AHU-12. Infill opening after replacement is complete. Replace AHU-13 and 14 on a one-for-one basis on the Junction level of the ATCT. Remove and provide new finned tube elements, control valves, balancing valves, shut off valves and associated piping on a one-for-one basis in the Base Building. The covers for the existing finned tube heating will be removed and re-installed. New valves will be installed in the hot water piping branch lines to facilitate work. Provide a full capacity temporary boiler plant with 100% redundancy during the removal and replacement of existing boilers, pumps and heat exchanger. Including (2) new boilers, (2) Tower hot water pumps, (2) Base Building hot water pumps, insulated steel piping between temporary boilers and temporary pumps, flexible piping between temporary pumps and existing system, temporary heated pump enclosures for winter operation, and temporary controls that mimic the existing configuration. Note: the temporary boiler plant was partially constructed at the time of original contract termination. The temporary boilers, pumps and associated piping and electrical supplies have already been purchased and are stored off-site and will be available for use, along with the original design drawings. Remove the existing boilers and replace with high efficiency boilers. The new boilers will be capable of local DDC control. Replace the hot water expansion tank and air separator on a one-for-one basis. The existing three hot water pumps were designed at 50% heating load each which provided partial redundancy. Replace with two (2) new hot water pumps designed each at 100% of the heating load providing 100% redundancy. New pumps provided with VFD for balancing to match existing flow characteristics. Replace hot water heat exchanger in the mechanical room of the Base Building. Replacement will include adding a second heat exchanger and the required valves, piping, and accessories for a fully redundant system. Replace all hydronic unit heaters in the pipe chase from the ground floor to the 13th floor with electric unit heaters. Existing hydronic piping taken back to the mains and capped. Re-locate humidifier wand diffusers for AHU-1 downstream of the duct smoke detector in the mechanical room of the Base Building. Add air handling units and humidifier to the 10th floor of the tower to serve the 11th floor of the tower. Remove AHU from the ASDE equipment room on the 11th floor above the Cab of the ATCT. Increase outside air circulation for ATCT stairwell free-cooling. This will include tying a new fan into the supply ductwork for the stair pressurization system to provide ventilation air into the space, and using the relief air damper and louver near the top of the stairwell to relieve air from the space. Controls will be modified to disable the ventilation system in case of emergency, and allow the stair pressurization system to function. Replace the chemical feed system for the heating hot water system. In the UPS room in the Base Building, install a filter bank on the air intake hood. Thermostat protection for cab under architectural scope of work. Provide 13th floor battery room ventilation. Replacement of duct electric coil EDH-11 located on the cable access level of the tower. Install electric unit heater in boiler room. Cap existing grilles in ATCT stairwell. The Electrical Work As part of this project, includes additional receptacles, fire alarm, telecommunications outlets and additional electrical equipment associated with new Architectural, Mechanical and Plumbing installations. Other miscellaneous electrical work is to be performed in various panels (for code and FAA order compliance) as noted in the design drawiings