A New York-Style Drilling Solution
The word "Manhattan" translates from the Lenape language as "island of many hills." The island of Manhattan in New York City doesn't have many hills any longer. Over the centuries, massive amounts of rock have been removed and excavated to create one of the largest commercial, financial and cultural centers in the world. John S. Civetta of Civetta & Sons, Inc., specialists in excavation and foundations from the Bronx, NY, is following in the tradition of removing rock from Manhattan, only he is doing it a bit differently.
When an old eight-story building on the corner of Madison Avenue and 53rd Street was demolished to make way for a 30-story building with 350,000 square feet of office space, Civetta was called on to remove rock 20 feet to 35 feet below the city surface. Since 2001, blasting in Manhattan has become a cumbersome process, and since the rock Civetta had to move was near a subway tunnel, he had to be creative. To crack the rock he turned to a chemical product called Da-mite.
"Everybody is still blasting, but we are experimenting with this," Civetta said.
To drill all the holes necessary for excavation, Civetta turned to an ECM-590 drill from Atlas Copco. The ECM-590 was a much-needed upgrade for Civetta. He had been using a first-generation hydraulic drill. To pull off the job on Madison Avenue, Civetta needed a versatile yet powerful drill. Not only would he be drilling hundreds of 2-1/2-inch holes — 15 feet deep — to hold the chemical mixture that would break up the bulk of the rock, he needed a drill that could line drill 4-inch holes 8 inches apart around the perimeter of the foundation — a sizeable undertaking for any drill, but the ECM-590 handled it without a problem.
"This drill is great. It is so much better than the old one we had, and we keep it running all the time. We drill holes for the chemical and while that is heating up, because it has to sit a while, we line drill around the foundation," Civetta said.
Drilling in the rock of Manhattan is a challenge. The pegmatite and Manhattan schist that support large concentrations of skyscrapers are extremely hard.
"That rock over there, you can stand on that with a hammer all day and you're not going to get anywhere," Civetta said.
The Daigh Company of Georgia distributes Da-mite, a highly expansive, rock-splitting mortar. When it is mixed and poured into a hole, it creates 18,000 psi to 20,000 psi of pressure after 24 hours. If it sits for several days, 40,000 psi to 50,000 psi of breaking force can be generated.
Civetta required every psi the chemical could muster. Holes for the chemical were generally drilled 2-1/2 feet apart for most of the project. Civetta said in softer rock the spacing can be opened up to create a larger pattern, but there isn't much soft rock in Manhattan. After the chemical is in the hole, a large steel slug is placed in the hole and blasting mats are placed over the area. After the rock cracks, it is hit with a 12,000-pound hammer to break it into pieces.
As the ECM-590 revved its engine at the site on Madison Ave., Civetta was standing at the edge of the foundation his crew was creating in Midtown Manhattan when asked how he liked working in the city.
"It's crazy. You know, to get the equipment down here, and even to get in and out of the city each day, it's crazy," Civetta said. Then, as he looked at the glass, steel and stone buildings, knowing he is a part of the construction tradition towering around him, he added, "How can you not love it?"