Anyone shopping for a complex masonry job involving concrete and limestone units will find more than they bargained for on the National Mall in Washington, D.C. Rising on the mall's last open building plot, at the foot of the U.S. Capitol, is the Smithsonian Institution's National Museum of the American Indian. The 260,000-sq.-ft. structure combines curved walls of cast-in-place concrete or concrete masonry construction, and will be enclosed with a limestone-faced wall system engineered for a 100-year service life.

In June 2001, the Smithsonian Institution awarded a contract to Clark/TMR, A Joint Venture, to build the museum over a schedule that would allow dedication on the fall 2004 equinox. Partners in the venture are Clark Construction Co. of Bethesda, Md., and Table Mountain Rancheria Enterprises Inc., a construction subsidiary of the Table Mountain Rancheria of Friant, Calif.

The museum occupies a 4.25-acre site east of the National Air and Space Museum. Since a September 1999 groundbreaking, the museum's unusual footprint has been etched into the landscape through excavation, drainage, sheeting and shoring, pile driving, and most recently, concrete, masonry and steel placement. Clark Construction's $56.7 million contract covers the foundation, structure and stonework. Total construction cost of the project will be nearly $200 million, with an additional $20 million for exhibitions, public programs, and opening events.

Since November 2001, the main construction activity has been the coordination and installation of underground utilities and the pouring of concrete. The concrete pile caps have been poured, and the placement of foundation walls, basement walls and circular basement columns followed. Once cast-in-place work reached grade level, project officials elected to switch to self-consolidating concrete mixes for the heavily reinforced vertical members that support large exhibit areas and walkways. Aggregate Industries of Greenbelt, Md., has delivered much of the ready mixed, including the SCC.

In February 2002, five exterior Kasota stone wall samples were erected on-site to help confirm the approved color range and assembly of the exterior walls. The museum will have an exterior cladding of Kasota dolomitic limestone from Minnesota. The pieces of Kasota stone will vary in size, coursing, and surface treatment, giving the building the appearance of a stratified stone mass that has been carved by wind and water. Additional building materials include American-mist granite and imperial plaster.