CONFIDENTIAL Structural Assessment of the Amtrak Under River Tunnels in NYC Inundated by Super Storm Sandy September 2014 Table of Contents Executive Summary ...................................................................................................................................... 2 Introduction.................................................................................................................................................... 4 Purpose and Scope ....................................................................................................................................... 4 History and Existing Conditions .................................................................................................................... 5 General ...................................................................................................................................................... 5 East River Tunnel ...................................................................................................................................... 5 North River Tunnel .................................................................................................................................... 8 Effects of Chlorides and Sulfates ................................................................................................................ 12 Inspection Approach ................................................................................................................................... 13 Phase 1 –Tunnel Scanning ..................................................................................................................... 13 Phase 2 – Visual Inspection and Testing ................................................................................................ 15 Visual Inspection Limits and Approach ................................................................................................ 15 Definitions Used for Visual Inspection ................................................................................................. 16 Visual Inspection Summary – East River Tunnel ................................................................................ 18 Visual Inspection Summary – North River Tunnel ............................................................................... 30 Material Testing ........................................................................................................................................... 46 Impact of Inundation on Structural Loading ................................................................................................ 47 Changes to Tunnel Lining Stresses ........................................................................................................ 47 Loads Resulting from Increases in Internal Pressure ............................................................................. 47 Loads Resulting from Changes in Tunnel Buoyancy .............................................................................. 48 Assessment ................................................................................................................................................. 50 Concrete Lining ....................................................................................................................................... 50 Cast Iron Lining ....................................................................................................................................... 50 Lining Bolts .............................................................................................................................................. 50 Bench Walls ............................................................................................................................................. 50 Rail and Ballast System ........................................................................................................................... 51 Recommendations ...................................................................................................................................... 52 Cost Estimate .............................................................................................................................................. 53 References .................................................................................................................................................. 54 Appendix A .................................................................................................................................................. 55 Appendix B .................................................................................................................................................. 55 September 18, 2014 CONFIDENTIAL New York City Under River Tunnels Superstorm Sandy Impact Assessment Executive Summary Superstorm Sandy (Sandy) created a storm surge that resulted in sea water inundating two of Amtrak’s New York City tunnels. The inundated tunnels were Amtrak’s North (Hudson) River tunnel and East River tunnel. Sea water entered into ventilation shafts at First and Eleventh Avenues in Manhattan, at the portal from Lines 1 and 2 in Long Island City, Queens, and at the portal for the North River tubes in Manhattan. The sea water, which contains highly reactive salts, caused significant damage to Amtrak’s signal and power systems, as well as to electrical and mechanical systems housed in the ventilation structures and these are the subject of an assessment being performed by others. This report addresses the damage that was caused to the structural components of the tunnels and presents recommendations to remedy this damage to meet the current state of practice for rail tunnels. The limit of inundation was different for each of the tunnels. The East River Tunnel experienced more sea water exposure, with water levels reaching the crowns at mid-river. In contrast, the North River Tunnel experienced less sea water exposure, with water levels reaching above the bench walls at mid- river. Based on observations and discussions with Amtrak’s personnel the majority of the sea water entered the East River Tunnel from the Queens portal and entered North River Tunnel from the Manhattan portal. The water was subsequently pumped out of the tunnels in a process commonly referred to as dewatering. The dewatering process, however, did not remove the salts, principally chlorides and sulfates that infiltrated the tunnels and coated various components. Tunnel inspections were performed throughout the limits of the inundation in the tunnels. These inspections commenced with high resolution laser scanning, along with digital and thermal imaging. These were followed by visual inspection, investigation of notable deficiencies, and material sampling and testing. The inspections revealed a number of features in the tunnels have been and are being damaged by chlorides and sulfates. These include exposed steel members, delaminated and cracked concrete, embedded reinforcing steel, running and third rail systems, track ballast and the numerous electrical and mechanical systems. There were elements in the tunnels that were not accessible for inspection. These may, during the course of the work, exhibit damage and require remedial action. In addition to the tunnel inspections, structural analyses were performed to determine whether the inundation caused either adverse stressing in the tunnel lining due to a change in the internal pressure or excessive stress in the linings and bolts due to their significant change in buoyancy. These analyses showed that in both instances additional stresses were induced in the tunnel lining. Although in one instance the induced stresses were significantly higher than the in-situ stress, these stresses were below the yield stress for the materials. The most serious damage in the tunnels was found in the concrete bench walls. These bench walls, which run portal to portal, are an essential component of the tunnels. The structures provide emergency egress from trains when necessary as well as access to trains and track for emergency and other personnel. The interiors house ducts that contain electrical wiring, equipment, cables, and other essential equipment. These bench walls were found to have a significant number of longitudinal cracks, severe spalls with exposed steel, and corrosion of embedded steel elements. Due to the porous nature of concrete, the continuous duct work, the cracks and various other factors, there were a multitude of paths into the structure of the bench walls for chlorides and sulfates. To a substantial degree, these substances could not be removed by the dewatering process and, when they were exposed to oxygen and moisture in the air after the dewatering was completed, they became damage-causing agents on their own. Due to their thorough infiltration of the bench wall surfaces and the ducts, these substances cannot be reliably removed. One example of the damage being caused by the chlorides and sulfates was evident in an August 19th dislodgement in one of the North River tubes. A piece of the bench wall fell onto the tracks, which led to emergency repairs and train delays. Unless the damaged bench walls are replaced, such incidences will continue and worsen due to the processes known generally as chloride attack and sulfate attack. It is accordingly recommended that the bench walls be replaced with new bench walls, constructed at the September 18, 2014 CONFIDENTIAL Page