DEP Invoice or Financial Record, September 30, 2001

NYC 9/11 Public Portal Document

ngine^j's.. .Water is an old problem for the trade center. The Hudson River used to flow where it was built When Europeans first laid eyes on what would be New York, the eastern shore of the Hudson River ran along what is now Greenwich Street, a Mock east of where the trade center towers would rise. It was here that the Dutch explorer Adriaen Block sank his ship, Tijger, in 1613, after it had burned. Part of that ship was found during digging for the IRT afcljisC subway line in 1916, and Mr. Tamaro said engineers had hoped to find the rest of it during the excavation for the trade center towers. What they dug up instead, he said, was garbage, animal carcasses, leather shoes, bottles, cannonballs, oyster shells, timber and other de­ bris that had been dumped on the The New York Times shore and used to extend the shore­ line west over 300 years, to the other The World Trade Center excavation in 1969, with its waterproof side of what is now West Street “bathtub” at right In the center are the original PATH tracks. Below that was river bottom, and below that was glacial till — gravel bedrock — around the entire 16-acre “You could see the tubes hanging scooped up and left by the glaciers construction site. As each 22-foot- in the air,” said Thomas J. Glennon, that once covered New York — and long section was being dug, it was 'a plumbing inspector at the site. That hardpan clay. About 75 feet below the filled with slurry, a mixture of clay station was subsequently demolished ground was mica-schistthe-bedrock and ’iiquid “ttiat -can--witbstand -the to become -part of-the site lor .4 and 5 that defines all Manhattan geology pressure of soil trying to close the World Trade Center, and the tracks and high-rise real estate. trench. -Then a cage of reinforced were rerouted to a new terminal in -According to Dr. Christopher J. the bottom of the basement The ex­ Schuberth, a professor at Armstrong steel was dropped into the slurry and concrete pumped into the trench cavated dirt, about 1.2 million cubic Atlantic State University in Savan­ yards, was dumped in the river nah, Ga., who is the author of a book from the bottom, pushing the slurry out the top, where it was captured across the street to create land for on New York geology, mica schist is part of Battery Park City. a hard, unyielding rock, 700 million and used in the next section. It took a year, from March 1967 to Once the basement structure was or. 800 million years old, left over done, Mr. Tamaro said, the tiebacks from an ancient mountain range. The were cut and their openings welded ; glaciers “tore the daylights out of the over with steel plate — partly be­ rock,” scooping it out in some spots and dumping gravel in others, he What lies beneath cause the basement floors were there to support the walls, partly to said. The schist is closest to the sur­ face in Midtown and at the southern the ruined plaza? avoid having a permanent part of the end of the island, making it easier to structure encroach on other people’s build skyscrapers there, and deeper Facts are elusive. property, and partly because they in other places, like Greenwich Vil­ serve as conduits for river water. lage. “Each one leaks water. They leak The present concern over the state forever, and it smells like hell,” Mr. March 1968, to complete what Mr. Tamaro said. of the basement arises from the way Tamaro calls the bathtub, a water­ Port Authority engineers got down to But without the floors in place to proof wall more than 3,000 feet long provide lateral support, there is a that bedrock for the foundations of encircling the oblong excavation site. the iwo 110-story towers, the Marri­ risk that the bathtub’s walls could To support this wall while the collapse inward if the wreckage in- ! ott Hotel and 6 World Trade Center. basement was being dug, bundles of To hold the river muck at bay and side it is not removed carefully. long steel rods known as tiebacks “You can’t just go digging next to prevent collapses of the unstable were drilled at a downward angle ground during excavation, the engi­ those walls,” Mr. Tamaro warned. through the wall and anchored in the He said new anchors might have to neers first dug a 3-foot-wide trench surrounding bedrock. As the bathtub 70 fe<»t deep — all the way down to be installed as the debris was exca­ deepened, tiebacks sprouted from its vated. “We have to stage our way walls like wild carrot tops, pre- down,” he said, excavating a level, stretdied so they would exert an putting in a row of anchors and then outward pull on the wall. digging some more, not unlike the The excavation proceeded around process they went through 33 years : and even under two PATH train tun­ ago to excavate the bathtub in the i nels that crossed the bathtub on the first place. way to a station on Church Street. It will be harder this time around.

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