Expert Says Tysons Tunnel Wouldn't Face Geologic Hitch
From today's Metro section:
The head of an engineering panel advising the state said yesterday that the geologic makeup under Tysons Corner would allow for a tunnel for the proposed Metrorail extension to Dulles International Airport.
Virginia Transportation Secretary Pierce R. Homer has asked the panel to recommend to the state at the end of the month whether it should build the four-mile Tysons Corner section of the 23-mile extension above or below ground. Fairfax County officials, Tysons landowners and some Metro officials say a tunnel would be less disruptive for motorists during construction and would contribute more to the hoped-for transformation of Tysons into a walkable quasi-city.
Contractors hired for the $4 billion project say a tunnel would be prohibitively expensive. They say that there is insufficient information about the rock and soil beneath Tysons and that it is possible that tunnel borings could run into unforeseen problems.
Robert O'Neil, a Potomac engineer leading the advisory panel, disputed this yesterday in a conference call. After initially believing that additional borings might be needed to test the soil, the panel has concluded, even without further tests, that tunneling beneath Tysons would not be a problem from a geological standpoint, he said.
-- Alec MacGillis