Guide for the Preservation of Highway Tunnel Systems (2015)

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82.1 Tunnel Systems The AASHTO Technical Committee for Tunnels (T-20) defines tunnels as “enclosed road- ways with vehicle access that is restricted to portals regardless of type of structure or method of construction.”(9) They further define road tunnels “not to include enclosed roadways created by highway bridges, railroad bridges, or other bridges.”(9) Highway tunnels are complex facilities containing multiple systems that contribute to their overall functionality and the safety of the traveling public in the event of fires and accidents. Each of these multiple systems also includes many subsystems. FHWA’s 2015 Specifications for National Tunnel Inventory categorizes these systems as shown in the following: • Structural systems: These systems make up the primary structure of the tunnel or support its equipment and include the walls, roof, ceiling slabs, roof beams, portals, invert slabs, slabs on-grade, cross-passageways, equipment supports, joints, and gaskets. • Civil systems: These systems consist of the wearing surface, traffic barriers, and pedestrian railings. • Mechanical systems: These systems consist of the ventilation system, drainage system, emer- gency generator system, and flood gates. The ventilation and drainage systems contain fans, fan motors, pumps, pump motors, pump controllers, piping, and drains. The emergency generator system includes a generator, fuel storage tank, fuel day tanks, exhaust air louvers, damper actuator, generator control equipment, and conduits. • Electrical systems: These systems include the tunnel’s electrical distribution and emergency distribution systems. The electrical distribution system includes switchgear, motor control centers, starters, transformers, transfer switches, panel boards, conduits, raceways, and electri- cal outlets/receptacles. The emergency distribution system consists of uninterruptable power supply, batteries, and battery charging equipment. • Lighting systems: These systems include the tunnel and emergency lighting systems. Both of these systems consist of light fixtures, fixture supports, bulb housings, lenses, light switches, junction boxes, wiring, conduit, cable, sensors, and controllers. • Fire/life safety/security systems: These systems consist of fire detection, fire protection, emergency communication, and operations and security systems. Fire detection systems consist of control panels, initiating devices (heat and smoke detectors, pull-stations, etc.), notification appliances (strobes, horns, etc.), wiring, conduit, and cable. Emergency commu- nication systems include communication devices [intercom, public address, emergency over- ride frequency modulation (FM) radio rebroadcast, private emergency radios, cell phones, receivers, wiring, exchange devices, signs, controllers, speakers, and audio input equipment]. Tunnel operations and security systems include communication equipment [closed-circuit television (CCTV) cameras, telephones, radios, etc.]. C H A P T E R 2 Description of Tunnel Assets

Description of Tunnel Assets 9 • Signs: Signs include traffic signs, over-height detection systems, pedestrian signs, variable message boards, lane signals, fixture control cabinets, and conduits. • Protective systems: These systems include steel corrosion, concrete corrosion, and fire protective coating systems.(10) See Appendix A for detailed information on many of these systems taken from the 2005 FHWA Highway and Rail Transit Tunnel Inspection Manual and the 2015 FHWA TOMIE Manual. 2.2 Life Safety Systems The NFPA 502 standard became a standard for life safety design of tunnels in 1981 but has since undergone significant revisions. Although NFPA 5000 has not been adopted as the govern- ing code in most states, NFPA 502 has been, and continues to be, the standard for life safety design in new highway tunnels. As system rehabilitation or replacement occurs to preserve older existing tunnels, many owners are looking to upgrade tunnel systems to implement life safety system recommendations from NFPA 502. Although older tunnels are grandfathered in and not required to be retrofitted to meet the NFPA standard, many owners are considering preservation actions for operational and safety upgrades by complying with this standard to the degree possible. The major systems and tunnel elements addressed in NFPA 502 include: • Fire protection systems, • Fire detection systems, • Life safety systems, • Emergency ventilation, • Communication systems, • Traffic control systems, and • Electrical systems.(8) See Chapter 4, Section 4.3, for examples of the types of preservation actions to upgrade these systems to meet life safety standards.