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7 Table 2. Damage potential of hazards and threats. Damage Potential Structural Integrity Hazard or Threat Extended Loss of Utility Disruption Extended Public Contamination Health Issue Fire/Smoke Asset Use Flooding Loss Hazard Fire (Unintentional) Structural Integrity Loss by Natural Causes Introduction of Hazardous Materials Threat Introduction of Small, Medium-Sized, or Large IEDs Introduction of C/B/R Agents Cyber Attack Maritime Incident Fire (Arson) Sabotage of MEC Systems C/B/R = chemical/biological/radiological. IEDs = improvised explosive devices. MEC = mechanical, electrical, and communications. Extended loss of asset use: loss of the ability to safely to ascertain the applicability of the table to his or her own move passengers or allow vehicular traffic for more than situation. 25 hours. The following sections present hazard and threat scenarios, Extended public health issue: actual or potential ability to respectively, in relation to assets. Note that some scenarios, such cause illness in a significant portion of the population as fire, may be the result of an intentional act (i.e., a threat) or sufficient to overwhelm the medical treatment capacity of an unintentional event or circumstance (i.e., a hazard). the area. 2.3.1 Hazard Scenarios in Relation to Assets 2.3 Hazard and Threat Scenarios Fire (Unintentional) Hazard and threat scenarios are profiles that include the hazard or threat, the mode of delivery, the path to the tar- Unintentional fire is more probable than intentional fire get, the tactical delivery device, and the location of the tar- and has occurred in several tunnel systems. Fire may destroy get. Table 3 provides basic hazard and threat scenarios. The any structure or vehicle and kill people if not controlled. A assumptions made during the development of this table are tunnel structure may be completely ruined by a conflagra- based on past terrorist acts and current available intelli- tion. Fire sources may be disparate and triggered by any com- gence. The scenarios are intended to include categories bination of flammable material and ignition. Fire occurs in applicable to highway, rail, and transit tunnel systems. nature and does not necessarily require human intervention However, the needs, vulnerabilities, and points of access to spread. Fire, or the danger of fire as a smoke condition, will differ from mode to mode, as well as from tunnel to tunnel immediately have a negative impact on all tunnel assets by within a mode. The reader is encouraged to review the text inducing the evacuation of persons and equipment from

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8 Table 3. Hazard and threat scenarios. Hazard or Mode of Path to Target Tactical Delivery Device Location of Target Threat Delivery Explosive Container Very Large IED Ship Waterway Top of Tunnel (Depth Charge) Large IED Vehicle Tunnel Roadway Truck Liner Large IED Vehicle Tunnel Roadway Truck Column or Wall Surface Roadway Large IED Vehicle Truck Roof Slab over Tunnel Large IED Vehicle Tunnel Roadway Truck Ventilation Building Large IED Vehicle Surface Access Road Truck Ventilation Building C&C Center Above Large IED Vehicle Tunnel Roadway Truck Tunnel Stand-Alone C&C Large IED Vehicle Surface Access Road Truck Center Large IED Vehicle Surface Access Road Truck Stand-Alone Substation Large IED Vehicle Surface Access Road Truck Ventilation Shaft Large IED Vehicle Surface Access Road Truck Station Large IED Vehicle Surface Access Road Truck Ventilation Structure Rail or Transit Locomotive or Freight/ Large IED Trackway Liner Vehicle Passenger Car Rail or Transit Locomotive or Freight/ Large IED Trackway Column or Wall Vehicle Passenger Car Medium IED Vehicle Tunnel Roadway Car or Van Liner Medium IED Vehicle Tunnel Roadway Car or Van Column or Wall Medium IED Vehicle Tunnel Roadway Car or Van Ventilation Building Medium IED Vehicle Surface Access Road Car or Van Ventilation Building Car or Van C&C Center Above Medium IED Vehicle Tunnel Roadway Tunnel Car or Van Stand-Alone C&C Medium IED Vehicle Surface Access Road Center Medium IED Vehicle Surface Access Road Car or Van Stand-Alone Substation Medium IED Vehicle Surface Access Road Car or Van Ventilation Shaft Medium IED Vehicle Surface Access Road Car or Van Ventilation Structure Motor Vehicle Surface Roadway Medium IED Truck or Multiple Backpacks Roof Slab or Foot over Tunnel Medium IED Transit Vehicle Trackway Car or Engine Liner Medium IED Transit Vehicle Trackway Car or Engine Column or Wall Freight/Passenger Car, Medium IED Rail Car or Foot Trackway Engine, or Multiple Liner Backpacks Freight/Passenger Car, Medium IED Rail Car or Foot Trackway Engine, or Multiple Column or Wall Backpacks Small IED Foot Tunnel Roadway Backpack Liner Small IED Foot Tunnel Roadway Backpack Column or Wall Small IED Stations/Shops/ Foot Backpack Column or Wall Tunnel Portals Small IED Stations/Shops/ Foot Backpack Liner Tunnel Portals

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9 Table 3. (Continued). Hazard or Mode of Tactical Delivery Path to Target Location of Target Threat Delivery Device Small IED Foot Tunnel Roadway Backpack Exposed Ductbank Small IED Foot Surface Access Road Backpack Inside Ventilation Building Small IED Foot Surface Access Road Backpack Inside C&C Center Small IED Inside a Stand-Alone Foot Surface Access Road Backpack Substation Small IED Exposed Ductbank or MEC Foot Tunnel Trainway Backpack Equipment Small IED Foot Tunnel Trainway Transit Vehicle Station Small IED Foot Surface Access Road Backpack Station Small IED Foot Surface Access Road Backpack Inside Substation Small IED Foot Surface Access Road Backpack Inside Ventilation Structure Large Fire Vehicle Tunnel Roadway Tanker Liner Large Fire Vehicle Tunnel Roadway Tanker Column/Wall/Roof Slab Large Fire Vehicle Tunnel Roadway Tanker Portal Any Tunnel Location Large Fire Vehicle Tunnel Roadway Tanker Adjacent to Critical Facility Large Fire Rail/Transit Car Trackway IED on Train Liner Large Fire Rail/Transit Car Trackway IED on Train Column/Wall/Roof Slab Large Fire Rail/Transit Car Trackway IED on Train Portal Any Tunnel Location Large Fire Rail/Transit Car Trackway IED on Train Adjacent to Critical Facility Tunnel Air Supply Vial/Aerosol/Small Tunnel Occupants and C/B/R Foot System Package Surrounding Population Surface Access Road Vial/Aerosol/Small Tunnel Occupants and C/B/R Foot to Tunnel Vent Intakes Package Surrounding Population Tunnel Air Supply Vial/Aerosol/Small Tunnel Occupants and C/B/R Vehicle System Package Surrounding Population Vial/Aerosol/Small Tunnel Occupants and C/B/R Vehicle Tunnel Roadway Package Surrounding Population Surface Access Road Vial/Aerosol/Large Tunnel Occupants and C/B/R Vehicle to Tunnel Vent Intakes Package on Truck Surrounding Population Surface Access Road Vial/Aerosol/Large Tunnel Occupants and C/B/R Vehicle to Tunnel Vent Intakes Package Surrounding Population On Foot in Vial/Aerosol/Large Tunnel Occupants and C/B/R Tunnel Roadway Transit Car Package Surrounding Population Vial/Aerosol/Large Tunnel Occupants and C/B/R Transit Car Tunnel Trainway Package on Train Surrounding Population Hazardous Vehicle Tunnel Roadway Truck Any Place in Tunnel Materials Hazardous Transit Car Tunnel Trainway Device on Train Any Place in Tunnel Materials Cyber Attack Digital Virtual Virus Code C&C Maritime Incident Ship Water Above Tunnel Passing Ship Tunnel Shell (Anchor Drag) C&C = command & control. IEDs = improvised explosive devices. MEC = mechanical, electrical, and communications.

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10 within the structure and surrounding areas. Fire and smoke Substations. Fire may damage or destroy the physical will decrease visibility to unsafe levels, precipitate collision of structures containing utility equipment and connections. vehicles and equipment, and cause personal injury. A fire con- A fire may also sever the power feed and monitoring sys- trolled by firefighting may still result in smoke and water tems of a substation, thereby rendering the station unfit for damage at a level sufficient to render a tunnel unfit for use or use. Equipment rendered unusable by the effects of a fire occupancy. The related assets are the following: will need to be replaced prior to the operation of a tunnel to maintain the ability to evacuate water and provide Tunnel structures. A fire may cause damage to the power. Substations may also be adversely impacted by fire- integrity of a structure and its engineered support bracing. fighting techniques that may send soiled water and debris The heat of a flame may distort all standard tunnel mate- into the plenums, thereby jamming lines and pump rotors. rials sufficient to require closure for repair. The damaging Utility building. Fire may damage the utility terminus effects of a fire are consistent across bored, cut-and-cover, structures, rendering them unusable. and immersed tube tunnel construction. Portals. Smoke and flame damage may threaten engineered Structural Integrity Loss by Natural Causes works to weaken a portal. Damage or destruction may also be inflicted on monitoring equipment situated at the portal to a Despite the best efforts of engineering and maintenance, tunnel such as over height detection units, heat sensors, car- the potential danger of structural integrity loss to tunnels and bon monoxide detectors, and closed-circuit camera units. supporting infrastructure from unforeseen circumstances Vent shafts. Fire, heat, and water damage may affect air will always exist. There is no known method to guarantee that intake and exhaust towers, machinery, and required air fil- a structure will never fail or deteriorate. Proper design, con- tering equipment. The damage would require replacement. struction, and maintenance may drastically reduce the likeli- Stations (passenger tunnels only). A fire may damage or hood of a sudden failure. However, unseen geotechnical or destroy wood, metal, and masonry structures that are nec- aquatic forces may go undetected by asset owners. Inconsis- essary for normal human occupancy. Certificates of occu- tencies and lapses in the design, construction, and mainte- pancy are routinely revoked when a fire causes damage to nance of a tunnel may collude to create the conditions for a a structure. A small conflagration, with flame and smoke, sudden structural integrity loss. may render a station unfit for occupancy and disallow its Structural integrity loss may be sudden or slow acting. The use by persons, vehicles, and equipment; it will be unfit scope of this damage may be minimal, such as a crack in the until environmental abatement is complete and repairs are wall requiring remediation or a pavement ripple requiring the made to meet regulatory code. A station unfit for occu- temporary relocation of traffic. Integrity loss may also be cat- pancy eliminates its primary function within the system, astrophic, resulting in total collapse or flooding of a structure, which is the transfer of passengers to railcar. wreaking widespread loss of assets, and loss of life. The related Distribution channels. The destructive path of flame and assets are the following: smoke may melt sheathing, iron piping, polyvinyl chloride (PVC), and metal conduit, thereby damaging the contents Tunnel structures. Loss of structural integrity threatens to beyond repair. Pipes carrying water could serve as conduits collapse the bore, tube, or constructed below-grade area for burning oil. Water used in firefighting efforts may have wholly or partially. A whole or partial collapse will force the a destructive effect on power and communication lines. closure of the asset for an undetermined amount of time. The loss of a utility in or near the tunnel structure will deny Minor integrity losses also drastically increase the oppor- service to the surrounding areas, including any businesses, tunity for water inflow, thereby inducing a progressive loss homes, or schools. Utilities may also facilitate the flow of of material strength. Loss of integrity directly affecting a water and other materials along their pathways and in rail bed or track may unsettle the transit area of the tube. entry and exit locations. Disturbances to only the transited area will slow road Control centers. Flame and smoke may destroy the physi- traffic until repair; these disturbances will likely halt rail cal structure and all mechanical equipment of a control traffic because of the deflection of the rail. center and endanger the lives of personnel assigned to that Portals. Portal construction is subject to the same stresses facility. Water damage to equipment and structure may as the tube areas. Whole or partial collapse will force a clo- also occur in firefighting efforts. The loss of a control cen- sure of the transit areas and nearby access paths. ter would severely affect the ability of a transportation sys- Vent shafts. Loss of structural integrity may destroy air tem to operate. The impact would be particularly severe on intake and exhaust plenums, shafts, and towers. A shift in rail systems that rely on remote monitoring and sensors to the support of a vent shaft area can alter the load-bearing control movement. capability to support heavy machinery necessary for air