Workers began blasting a half-mile tunnel under Tysons Corner, Va., as part of an extension of the Metrorail to Dulles International Airport. The complex construction of the tunnel will cost $85 million and should not disturb hotels, offices or roads on the surface above. Dominic Cerulli, the engineer for Bechtel in charge of the tunneling project, said the busy intersection "makes for a very challenging tunneling environment."

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