The Army Corps of Engineers' New York District has undertaken a series of estuary initiatives with the Port Authority of New York and New Jersey, and the states of New York and New Jersey to deepen the channels of the third-largest container port in the nation. Part of this work involves deepening the Kill Van Kull channel, which connects Upper New York Bay with Newark Bay, and serves as the main route for ships docking at the busy New Jersey harbors of Port Newark and Port Elizabeth. In the Kill Van Kull, they're dredging nine diverse types of materials, each of which poses its own engineering challenge. Where the harbor composition makes it possible, the Corps is drilling and dredging. Materials that the Corps is dredging include glacial till, which was left by the glaciers as they receded; red-brown clay, which is hard to dig; and four varieties of rocks. The project is using a liquid explosive for the blasting, and trying to do that during the day, so as not to disturb residents.