Hensel Phelps and their design partner Fentress Architects was awarded a design-build contract with NAVFAC Washington for the P646 Defense Security Service (DSS) Facility Addition at Marine Corps Base Quantico, Virginia. The 40,000 SF secure facility is an addition to the existing Military Department Investigative Agencies (MDIA) Headquarters—the Russell-Knox Building—that was completed by the Hensel Phelps/Fentress team in 2010. The project scope includes design and construction of the addition and an elevated parking garage. The existing facility will remain in full operation during the design and construction.