Renovation of St. Louis’ Gateway Arch landscape and museum involves numerous sitework challenges.
When the Gateway Arch opened in downtown St. Louis in 1965, the 630-foot monument exemplified innovation in architecture, structural engineering, and construction expertise. Five decades later, the sitework challenges of renovating the Arch’s historic landscape and expanding its subterranean museum are a showcase of logistical complexity.
Constraints on all four sides limited access points and the ability to transport materials to the iconic monument, which is situated at the center of a 70-acre site. To the east is the Mississippi River, the region’s foremost waterway (and the source of two flood events that significantly impacted construction activities). And to the west is a major interstate highway that separates the Arch from the densely occupied downtown area.
Further complicating this scenario, the Gateway Arch had to remain open, accessible, and fully operational throughout the three-year project. Because this tourist destination attracts about 4 million visitors annually, our team had to be constantly vigilant in managing pedestrian traffic while maintaining a safe, orderly site so visitors could fully enjoy their experience.
As a designated National Historic Landmark, the site was subject to requirements that included archaeological monitoring as well as protection and documentation of existing historic elements.
The project’s scale and complexity necessitated development of a comprehensive site logistics and phasing plan. This coordinated strategy involved completing all sitework on the north and south park areas prior to executing the museum expansion portion of the assignment. Essentially, it was the opposite approach to working from the inside-out.
Construction barriers that were erected to allow visitors to safely access the Arch also restricted site-wide access for construction workers. To overcome this obstacle, we had to use duplicate equipment in some cases to facilitate efficient transporting of materials between the north and south parcels of the site.
Creating a pedestrian-friendly experience
The goal of the project’s first phase was to create a more pedestrian-friendly experience for visitors, with easier access from downtown St. Louis and the riverfront. This includes a new land bridge that spans over the highway to provide safe, convenient access to the Arch from downtown.
The renovated park grounds feature a new circulation loop that encompasses more than five miles of accessible pedestrian pathways. Our work involved re-grading the site and installing new landscaping, a new irrigation system, and amended soil and sod.
However, as sitework began we discovered that the condition of the existing soils was much worse than the geotechnical report indicated. Just below the grassy surface lay decades of debris from abandoned and demolished buildings previously located on the site.
To address this issue, we created a large area onsite for evaluating and sorting the existing subgrade material into soil that could be reused and rubble that was transported offsite. Specialized skeleton buckets and screeners helped us complete this sorting process and retain as much geotechnical material as possible.
Though labor intensive, this double handling of soil material was a vital step for implementing the overall landscape design, which involved replacing the 800 existing Ash trees on the grounds’ processional allées with London Plane trees.
A considerable portion of the site consisted of a vegetation protection zone (VPZ) that was not permitted to be compressed or compacted by installations because of its fragile root systems. All work in those areas had to be completed by hand or by directionally boring below the surface using trenchless technology.
Over the decades, the urban site had undergone significant construction activity, yet the available records of buried utility lines and other hazards were incomplete and potentially inaccurate.
Our team used a combination of leading-edge subsurface utility mapping technologies to ensure the Arch and existing subterranean museum remained fully operational during construction, with no interruption to critical utility systems. Ground penetrating radar and other electronic locating devices helped us supplement historical data and other traditional approaches to underground surveying. This data now provides an accurate record of the site for future use.
Expanding the museum
The project’s second phase involved a 50,000-square-foot subterranean addition to the existing 100,000-square-foot museum, including creation of a dramatic new entrance and upper-level lobby facing downtown St. Louis.
Constructed with cantilevered solid steel beams and custom glazing, the reinforced roof deck features 2,400 cubic yards of post-tensioned concrete, as well as 189,000 cubic feet of geofoam blocks to eliminate additional excessive weight on the roof deck.
Mass excavation for the museum involved a fully shored hole approximately 30 feet deep. We used a resonant breaking machine to limit vibration in the removal of concrete pavement and specialty conveyors for installation of the reinforced soil slopes along the east bank of the Arch grounds and around the museum. This specialty slope is stabilized with layers of geogrid and fiber-infused soil.
Overall, this ambitious project required extensive coordination among a large team of consultants, architects, archeologists, governmental agencies, and subcontractors working on the project — often simultaneously.
In total, the project involved moving 300,000 cubic yards of earth, which is the equivalent of 19 football fields each piled with 10 feet of dirt. This included 80,000 cubic yards of mass excavation and haul off and the installation of more than 150,000 cubic yards of specialty and amended soils. The project involved creating nine acres of exposed aggregate walkways as well as constructing a new infrastructure of storm sewers, extensive underdrain systems, sanitary sewers, water mains, and underground electrical duct banks.
More than 50 pieces of sitework equipment were commissioned, including bulldozers, high lifts, 300- and 400-size excavators, a tractor with 17-cubic-yard pans, and a directional boring machine. Smaller specialty equipment included conveyors and low-impact skid loaders.
With the July 2018 opening of the reimagined Gateway Arch National Park, visitors have new opportunities to access and experience the tallest man-made monument in the Western Hemisphere.
By weaving the international icon into the fabric of the region, the expansive park strengthens connections to downtown St. Louis and the riverfront while creating an inspiring urban oasis. Ultimately, it revitalizes an enduring symbol of St. Louis and the Gateway of the West for generations to come.
Museum at the Gateway Arch
As part of Michael Van Valkenburgh Associates (MVVA) team that won the 2010 City+Arch+River international design competition, Cooper Robertson and James Carpenter Design Associates (JCDA) with Trivers Associates designed the significant expansion and renovation of the Eero Saarinen-designed Museum of Westward Expansion, located directly below the iconic Gateway Arch. The museum is scheduled to open July 3, 2018. The museum improvements are one part of MVVA’s comprehensive expansion and renewal of the National Park’s Dan Kiley-designed 91-acre landscape with dramatically improved connections to downtown St. Louis.
JCDA’s work has primarily focused on planning and design of the museum expansion’s new West Entry and public spaces. JCDA applied its design approach founded on the experience of light in the built environment, to the entry sequence and the new main public spaces of the Museum Arrivals Hall, which lead down to and connect with renewed exhibitions and the renovated Saarinen museum below the Arch. Beyond transforming, modernizing, and improving the museum, the project goal was to better integrate the new and original museum within the National Park Service’s Gateway Arch landscape and improve connectivity between the park to the Old Courthouse and into downtown St. Louis. JCDA and Cooper Robertson created a new civic space that engages with and reinforces the presence of the international icon of the Arch, while directly supporting the revitalization of downtown St. Louis.
Watch a time lapse video of museum construction at https://vimeo.com/268616120.
Information provide by v2com (www.v2com-newswire.com), an international newswire specializing in design, architecture, and lifestyle.
Michael Pranger is vice president of operations at Castle Contracting, LLC (www.digcastle.com), which provides turnkey site preparation services, site utilities, earthwork, subsurface utility mapping, and trenchless technology directly to owners; general contractors; and mechanical, electrical, plumbing, and fire protection contractors. He can be reached at firstname.lastname@example.org.