down for the lobby floor. Ayres confronted a vitally important design problem concerning the nature of the soil. Due to the formerly marshy condition of the soil and the existence of several submerged streams nearby, Ayres designed a structure that would stand on more than 18,000 pilings. However, water pressure from the submerged Tiber Creek would make it difficult to drive the piles. Ayres and his team devised a plan whereby a deep-sea diver descended into the underground Tiber Creek and drilled a hole deep into the earth. A hose would be inserted into the hole, and water pumped from the earth until the water table dropped and the driving of the piles could be accomplished. The building's foundation was more than three feet thick in places in order to withstand the hydraulic pressure put on it by the submerged Tiber Creek. Water from the Tiber was utilized as an air conditioning system to cool the building. Ayres submitted his design for the Commerce building to the Public Buildings Commission, which gave its approval on November 1, 1927. The previous size of the building was reaffirmed. Excavation of the site began on November 21, 1927. However, although Ayres had proposed an Italian Renaissance style for the Commerce building, few of the other building proposals had adopted a classical design. On November 25, 1927, the Commission on Fine Arts adopted a requirement that all the Federal Triangle buildings have a "uniform appearance" and height (six stories), limiting the Board's design deliberations (and Ayres' proposal for the Commerce building). Treasury Secretary Andrew W. Mellon imposed a requirement in December 1927 that all the buildings be built in the Neoclassical architectural style. Ayres modified the exterior design of his structure accordingly. By March 1928, newspapers were reporting that the Commerce and Internal Revenue buildings would be constructed first. Ayres' design, however, was still in flux, as the Board of Architectural Consultants refused to give its approval to his plan. Although the size of the Commerce building had stabilized by March 1928, some Board members still suggested that both 15th and 14th Streets NW be submerged in tunnels beneath the structure. Despite the ongoing dispute over the design, additional demolition contracts were awarded for the site in April 1928. The Board of Architectural Consultants and Ayres met in July 1928 to consider ways in which the construction program might be sped up, and devised