The new, 1.2-million-sq-ft U.S. Coast Guard headquarters in Washington, D.C., is set on a hillside that overlooks the Potomac and Anacostia rivers. Given the sprawling building footprint over the site's steep, 160-ft vertical elevation change, 1.6 million cu yards of soils were excavated, which required 300,000 sq ft of timber lagging and 1,500 soldier piles.
Post-award, geotechnical analysis of the soils determined the existing marine clay would not support the originally designed foundation system. A revised foundations plan called for 1,500 caissons, measuring up to eight feet wide and 100 ft deep. Clark Concrete poured 250,000 cu yd of concrete.
Nine of the buiding's 11 floors are located below grade, which meant that 60% of the foundation work was below ground. As seven full-time employees would have been required, traditional survey techniques proved to be unaffordable; instead, robotic-station measurements were used. Monitoring points were equipped with mounted prisms, and software allowed measurements to be programmed without operator intervention.
Several interior revisions were made during construction. The building's future tenants needed every level of the structure to be reprogrammed, with changes to the majority of partitions and associated MEP infrastructure. Security and IT requirements evolved during the project, also prompting end-user changes.
More than 200,000 plants and 300 canopy trees were planted. Beginning with a series of courtyards at the lowest level, employees walk through landscaped exterior space up to Lower Level 3. Each courtyard represents a distinct North American climate zone, and the interior features were designed to match as a means of way-finding.
The project included 450,000 sq ft of green roof, installed on top of the headquarters and a 800,00-sq-ft parking garage. The roof and courtyard irrigation system is fed from the retention pond at the lowest level, the pond collecting runoff from the entire campus. The design also focused on maximizing energy efficiency and minimizing waste. The project earned LEED-Gold certification.
Completed in May, the project also includes, besides the parking garage, a central utility plant and the U.S. Dept. of Homeland Security National Operations Center.
U.S. Coast Guard HeadquartersWashington, D.C.
Owner U.S. General Services Administration
Design-Builder Clark Construction Group
Construction Manager Tishman-AECOM
Architect of Record for Headquarters WDG
Interior Fit-out Architect HOK Interior
Landscape Architect HOK Landscape
Architect of Record for CUP, Garage McKissack & McKissack
Quality Control McKissack & McKissack
Structural Engineer Cagley & Associates
Electrical-Mechanical Engineer Girard Engineering
Civil Engineer Loiderman Soltesz Associates
Skin Consultant Tadjer Cohen Edelson
Geotechnical Consultant ECS Mid-Atlantic
Fire, Life Safety Consultant ARUP
Cast-In-Place Concrete Subcontractor Clark Concrete
Foundations Subcontractor Clark Foundations
Excavation Subcontractor Metrol-Total, a joint venture
Electrical Design-Assist Subcontractor Dynalectric
Mechanical Design-Assist Subcontractor John J. Kirlin
Glazing Design-Assist Subcontractor Harmon