both of whom were partners with SOM, proposed a tower with floors in the lower part of the building, as well as a series of setbacks with gradually tapering floor plates, giving the tower its distinctive look. During the design process, one of the architects reportedly pulled out nine cigars and staggered them vertically until the pair both agreed to the arrangement. This allowed Sears to occupy the large lower stories, while providing more conventional office space that could be rented out on the upper stories. The firm of Saphier, Lerner, Schindler was responsible for determining Sears's space requirements and designing furniture for the company. It conducted a year-long study to determine how 16 of the company's departments should be laid out within the building. As Sears continued to offer optimistic growth projections, the height of the proposed tower also increased. Under Chicago's relatively lax zoning laws, the site could theoretically accommodate a 300-story building with . In practice, most potential tenants did not want excessively high offices. Additionally, the Federal Aviation Administration (FAA) restricted the height of structures in the area to protect air traffic. FAA officials publicly denied that they had imposed a height limit; however, the area's minimum safe altitude would need to be raised by if the building was just taller. Plans for the tower were announced on July 27, 1970. The building would contain 109 stories as measured from Wacker Drive and 110 stories as measured from Franklin Street. This would make Sears's new tower the tallest in the world, as measured by roof height, although New York City's under-construction World Trade Center Twin Towers would have a taller antenna. Although the Sears Tower would contain of space, only about would be used as offices. Construction Early construction Work on the building's foundation commenced in August 1970. Contractors excavated the lot to a depth of , and they removed of dirt from the site. By that November, Spencer, White & Prentis Inc. was excavating a trench around the site, measuring deep and across. The contractors then built a slurry wall within the trench, made of concrete and reinforced steel. Workers used steel bracing to prevent the slurry wall from collapsing inward, then used caissons to drill 201 holes into the ground. They also rerouted a sewer that had run underneath Quincy Street, which was to be closed permanent as part of the tower's construction. The