They included a central and perimeter security system; closing of the central plaza of the building, which, along with other changes, increased its interior footage by 80000 sqft ; steel-jacketed underground parking garage columns capable of withstanding a powerful explosion; six fully staffed security screening points; concrete blockades built into the façade; communication, potable water, and utilities contained in blast-proof spaces; ventilation shafts for the parking garage in a secure area; and special security procedures to obtain access to the building's critical systems.