US-based McCarthy Building has completed a 47,000ft² subterranean expansion and renovation of the Museum of the Gateway Arch as part of the $380m redevelopment of the monument in downtown St Louis.
On average, nearly four million individuals visit the 630ft structure each year.
The renovated museum and visitors centre features a new circular entrance and upper-level lobby facing downtown St Louis, which replaces the previous underground entrances at the base of each Arch leg.
Visitors will now enter the monument through a custom-built glass and stainless-steel entry enclosure system at street level.
The reinforced roof deck of the expanded museum features 2,400yd³ of post-tensioned concrete slabs, as well as 189,000ft³ of GeoFoam blocks, which eliminates additional excessive weight on the roof deck.
The Gateway Arch remained open, accessible and fully operational throughout the three-year construction project.
Through the new main entrance, visitors enter into a daylight-filled, climate-controlled plaza that provides views of the Old Courthouse landmark and downtown St Louis.
A grand mezzanine features a terrazzo floor with a giant US map illustrating the westward migration from St Louis and other cities.
It leads to new galleries that trace St Louis’ role in westward expansion from the mid-1600s to the present. The tram lobby includes a 100ft video wall, which will project scenes from the original construction of the Gateway Arch and other examples of American innovation.
Designed and constructed to pursue LEED Silver certification from the US Green Building Council, the expansion is the first renovation since the 106,000ft² Museum of Westward Expansion opened in 1976.
As part of the project, the north and south grounds surrounding the 50-year-old historic monument were renovated to create a more pedestrian-friendly experience, providing easier access from downtown St Louis and the riverfront.
The renovated park grounds consist of more than five miles of bike and walking paths, an outdoor natural amphitheatre, and a new land bridge that connects the Arch to downtown for the first time.
Over 800 existing Ash trees have been replaced with London plane trees that are resistant to emerald ash borer disease.
McCarthy collaborated with sister company Castle Contracting to re-grade the site and install new landscaping, new irrigation system, and amended soil and sod.
Cooper Robertson and James Carpenter Associates, both of New York, designed the museum expansion with Trivers Associates, St Louis.
Michael Van Valkenburgh Associates of New York oversaw the landscape design. Gateway Arch Park Foundation and the National Park Service led the redevelopment projects.
Image: The Gateway Arch in downtown St Louis. Photo: courtesy of McCarthy Building Companies, Inc.