U.S. Department of Transportation Headquarters
Completed in 2007, the headquarters for the U.S. Department of Transportation (DOT) was the first new cabinet-level headquarters to be designed and constructed in the Capital in over three decades. The massive 2.1 million square-foot complex spans two city blocks, amounting to 11 acres, and is home to the agency’s more than 5,000 employees.
The DOT Headquarters includes a nine-story western tower and an eight-level eastern tower situated on opposite sides of Third Street. Two levels of below-grade parking can accomodate 1,000 spaces. Although a highly-secured facility, the building presents an open appearance to the public and surrounding community. A multi-story lobby leads to adjacent first floor space, which contains a large assembly area. Matching 70-foot-wide central linear atriums provide a visual connection between the two towers. Third Street, which divides the two buildings, was converted into a pedestrian promenade, and heavy landscaping softens the mandated 50-foot security setbacks. In addition to the office structures, Clark also constructed new streets, sidewalks, plazas, and retail pavilions, as well as a “walking museum” that illustrates the important functions of the DOT.
Clark Foundations work on site offered a glimpse into Washington’s multimodal transportation history. Along with the logistics and planning required for such a massive site, the excavation program required an archeological search for artifacts from the Old Washington Canal, which connected the Anacostia and Potomac rivers in the 18th Century. More than 100,000 cubic yards of contaminated soil had to be removed from the site, which had served as the Washington Navy Yard factory for fabricating battleship gun barrels.
Clark Foundations overcame the challenges posed by the site and scope and completed the DOT Headquarters on-time and within budget while meeting the needs of the project's stakeholders. The success of this project was the result of strong teamwork between all project participants, including the subcontractors, architects, client, and Federal Government.
Concrete work at the site was no easy task. The project’s sheer size and complex design specifications created a challenge for craftsmen, but one they completed with ease.
As a security measure, architects encased concrete garage columns in ½” steel jackets to help resist the potential impact of a blast. To make this work, concrete subcontractors Clark Concrete and its subcontractor partner were forced to meet strict tolerances at the gaps in the tops and bottoms of the columns. To achieve this objective, each blast jacket was carefully engineered to fit a specific location and orientation prior to installation. Their attention to detail paid off. Despite sloping floor slabs and soffits, each of the column jackets was placed without problems or delays and all tolerances were met.
Controlling the temperature in the mat foundation also proved to be a challenge due to the large quantities and depths of concrete being placed. Project specifications required controlling the ultimate temperature achieved in the core of the slab, as well as the differential between the core and the surface. Craftsmen used a number of methods to control the ultimate temperature of the core, including using flyash as an alternate to cement, which provides a slower heat of hydration. In addition, they also used chilled water and ice in the concrete mix. Maintaining a differential or less than 50 degrees Fahrenheit between the surface and core proved to be challenging, but was achieved through careful monitoring. Craftsmen also covered slabs, even in warm weather, to slow heat loss at the surface.
Despite numerous design changes along the way, the team managed to save time in the schedule and complete their work in a 10-month period.
The DOT Headquarters features a green roof on both buildings. The green roof helps reduce heating costs, cooling costs, and rainfall runoff. The entire roof area for DOT Headquarters is 158,000 square feet; the green roofs − composed of soil and sedum—account for 69,000 square feet.