Two New York City rail tunnels along the congested Northeast Corridor will require an estimated $689 million in repairs after Superstorm Sandy-related inundation, states a report conducted by HNTB Corp. for the commuter railroad Amtrak.

Amtrak officials used the report, released on Oct. 2, to re-emphasize their call for the so-called Gateway program (ENR 1/23/12 p. 16). The scheme envisions two new trans-Hudson River tunnels, but, so far, no source of funding has been identified.

The report notes that a two-tube tunnel underneath the Hudson River and a four-tube tunnel below the East River got between 2,300 ft to 4,200 ft of inundation. The tubes range from 12,000 to 13,500 ft. Each tunnel consists of an outer cast-iron lining and an inner cast-in-place concrete lining, unreinforced and about 2 ft thick, says the report.

Inspectors used photogrammetry, lasers and infrared scans as well as visual inspections and concrete sampling. They found no evidence that the linings are structurally unsound but did find significant damage to key concrete and steel components from chlorides and sulfates. Structural deterioration continues, the report says.

The report recommends pressure- washing, replacement of some concrete, epoxy grouting of cracks greater than an eighth-inch thick, replacement of the concrete bench walls that surround the electrical ducts and replacement of the ballasted track system with a direct-fixation track system. HNTB referred inquiries to Amtrak.

"The main focus now is to address the findings and do the necessary work," says Amtrak spokesman Craig Schulz. But the proposed new Gateway tunnels are needed before the existing ones can undergo truly long-term fixes. "Throughout [Amtrak's] history, it's been subject to annual appropriations," Schulz says. "Any time you're looking at a large-scale program like Gateway, it is extremely difficult to plan."