Once the street was legally "opened" with the approval by the court of the commission's figures, the city collected the assessment from the landowners along the street, and once the assessment was totally collected, the streets could be built, or "worked". The land was cleared, hills were excavated or hollows filled in, the right of way was leveled and the street was paved. Many years could pass between when a street was "opened" and when it finally began to resemble a city street, having been cleared, leveled, graded and paved. The grading was often difficult because of the rocky nature of the island, especially on the West Side. In 1843, Isaacher Cozzens described the ground as "a tough cement of clay, gravel, and boulders, very hard to dig. In digging through 42nd Street, the pickaxes had to be used for every shovelful of this clayey cement which formed what is called, a hard-pan, of about fourteen feet or more."