DOT Proposes National Tunnel Inspection Standards

They would apply to about 350 tunnels in the United States located on federal-aid highways. The Federal Highway Administration would model them after the existing National Bridge Inspection Standards.

Moving to fulfill an NTSB recommendation stemming from the ceiling collapse in Boston's Central Artery Tunnel in July 2006 that killed a passenger in a car, DOT's Federal Highway Administration has proposed creating National Tunnel Inspection standards that would apply to about 350 tunnels in the United States located on federal-aid highways. FHWA said it would model them after the existing National Bridge Inspection Standards, but key members of Congress said Wednesday they believe FHWA oversight of more than 600,000 bridges is not doing enough to ensure those bridges' safety. DOT's inspector general also called for such an inspection regime during 2007 testimony before Congress.

The standards would apply to structures including Boston's Central Artery tunnel, New York City's Lincoln Tunnel, and Baltimore's Fort McHenry and Baltimore Harbor tunnels, all of which are heavily used. The Lincoln Tunnel carries about 120,000 vehicles per day, making it the busiest vehicular tunnel in the world, FHWA said, and the Fort McHenry Tunnel handles more than 115,000 vehicles daily.

Comments are due by Sept. 20 (www.regulations.gov). The standards would include requirements for inspecting structural elements and mechanical, electrical, hydraulic, and ventilation systems; qualifications for inspectors; inspection frequencies; and a National Tunnel Inventory.

Tunnel inspection frequency is not consistent nationwide; it ranges from daily to every 10 years, according to FHWA. The proposed standards would require state transportation departments and federal agencies owning tunnels not only to adhere to the standards but also to report inspection findings to FHWA and fix problems they find in a timely manner.

The agency's notice cited a tunnel problem that was detected in time: "The importance of tunnel inspection was demonstrated in the summer of 2007 in the I-70 Hanging Lake tunnel in Colorado when a ceiling and roof inspection uncovered a crack in the roof that was compromising the structural integrity of the tunnel. This discovery prompted the closure of the tunnel for several months for needed repairs. The repairs included removal of more than 30 feet of soil fill material from the top of the tunnel roof, temporary support of the roof from the inside of the tunnel, removal of the suspended ceiling, and the design and construction of a new slab cast on top of the existing roof to reinforce and add extra structural capacity. To accomplish the repair, the eastbound tube under the cracked roof was closed to traffic, and the adjacent westbound tube was converted to a tube with bi-directional traffic. Even though the eastbound tunnel was closed for 7 months, and the repair cost approximately $6 million, the repairs helped prevent a potential safety incident."

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