New Orleans Museum of Art (NOMA) engaged Impetus (formerly Palmisano) as the Design-Assist Contractor to lead the 6.5-acre expansion of the Sydney and Walda Besthoff Sculpture Garden located within City Park’s existing landscape and lagoons. Completed in partnership with Massachusetts-based Reed Hilderbrand Landscape Architects, this expansion furthers the museum’s mission for increased community access to the arts through indoor and outdoor learning environments.
New Orleans, LA
The New Orleans Museum of Art
Reed Hilderbrand + Lee Ledbetter & Associates
Arts & Culture
ENR Texas and Louisiana, Best Regional Projects, 2019
ABC Bayou Chapter, Excellence in Construction, 2019
ACI LA Chapter, Excellence in Concrete Construction, 2019
Impetus a highly organized and professional demeanor throughout the project. It was a pleasure to work with such a creative and energetic construction team on this project, and we believe that the project’s success is in large part due to the collaborative design-build approach that Impetus set forth.
In particular, the on-site superintendent and the project manager were both extremely knowledgeable, good-natured and dedicated to the project’s success.
LESLIE CARTER, SENIOR ASSOCIATE, REED HILDERBRAND
The focus of the project is the 11-mile-long water system. Impetus’ Civil division led activities to reshape the existing lagoon to enhance the spatial experience of the open water and stabilize the shoreline to improve water quality and reduce flow into municipal systems. A portion of the lagoon was reclaimed for a stage and in-grade amphitheater formed from a variety of soils.
AMOUNT OF SOIL REMOVED FROM THE LAGOON
0 CUBIC YARDS
The introduction of a new concrete weir allows for changes in water levels to address flooding potential and re-oxygenate the system as it flows through the garden.
The previous weir structure had a manual weir plate that was removed to control water levels. It was easily accessible to visitors and constantly tampered with, creating challenges for maintaining the water level. The flood control functions built into the new weir require no human interaction to manage the water to the proper elevation.
The water elevation is initially controlled by a five-foot-wide opening in the weir, and as water rises, it flows over two additional sections that span an additional 25 feet. To control water during heavy rain events, the additional 40 feet of weir kick into operation, bringing the total area of the weir structure that is draining water up to 70 feet, ranging in depths that water can flow over from 2 feet to 1 foot. After construction, the lagoon now holds an additional 560,000 gallons of water upstream of the weir and an additional 228,000 gallons of water downstream of the weir.
The new weir structure used 15% less concrete than the original concrete design, which allowed Impetus to accelerate the schedule. Using precast concrete created efficiencies for both production and install, as the sheet pile weir and concrete were constructed at the same time. The team was able to work on both elements simultaneously, and immediately hang the concrete on weir on the sheet pile weir.
A network of pedestrian paths respond to the landscape and create fluid paths through the site, including 800-linear-feet of bridges. The two sculpture gardens are connected by the Canal Bridge, a 300-foot-long submerged concrete shell structure that is footed in piles and dips into the lagoon, creating the sensation of walking through water. This bridge is the second of its kind in the world.
LENGTH OF BRIDGES THROUGHOUT THE GARDEN
0 LINEAR FEET
The bridge’s railing elevations are designed to perform in unison with the weir structure. Until there is a heavy rain event, the railing elevations match the weir structure and do not overtop. But in the event of heavy rain, there is a drainage system built into the bottom slab of the bridge that ties back in to subsurface drainage system. As the weir controls the water back to a normal elevation, the bridge’s automatic pumps drain the water back into the lagoon.
Concrete was chosen for its ability to achieve an aesthetic that does not compete with the landscape, and to achieve the complexity of the architectural and structural design. Ensuring the bridge is water tight was also important since it is designed is to connect the two sculpture gardens. Should a leak exist, there would be a buildup of algae, creating a dangerous, slick walking surface. Total Station was used to create accurate layouts of a 16th of an inch or less for the architectural concrete on the canal bridge.
Two elevated boardwalks made of structural steel, stainless-steel handrails, and Cumaru wood decking span the open water. A 70-foot long site-specific structural steel and glass bridge featuring artwork by Elyn Zimmerman is made of 30 components depicting the avulsions of the Mississippi River. The surface of the bridge is made of laminated tempered glass.
Building the bridges within the lagoon site was completely dependent on the lagoon remaining dry. The schedule for the expansion project allotted for three rain days per month during the 15-month-long project, but Mother Nature had other plans. In total, there were 95 rain days during construction.
In one instance, the site received six inches of rain in a mere four hours. The main drainage canal pump station lost power, and excessive rainfall pushed water into the City Park water system and strained the AquaDams positioned to keep the lagoon dry. One AquaDam failed and water began to release back into the site. The team was alerted by float systems attached to the pumps that monitor the water levels. The dam was recovered, stabilized, and reinforced with an earthen dam.
TOTAL RAIN DAYS
0 MONTHS EARLY
Designed by Lee Ledbetter and Associates, The Pavilion is a single-story ellipse-shaped interior exhibition space made of structural steel frame and is home to indoor sculptures. The building also holds MEP equipment and restrooms. The roof is made of PVC and contains 46 skylights. A 60-foot-long mosaic tile wall by Teresita Fernández wraps around a radial precast paver courtyard.
Impetus created an environmental protection plan in coordination with New Orleans City Park management, the Louisiana Department of Wildlife and Fisheries, the Louisiana Department of Environmental Quality and private environmental consultants. The plan included a phased protocol for protecting birds and fish within the expansion site, aiming to minimize the impact to wildlife, water quality, and visitor experience. When de-watering the lagoon, consultants ventured into the open lagoon on kayaks to relocate turtles and fish.
Impetus reduced the number of new plantings in the original scope to drive value for the long-term health and cost of the garden. The limited plantings allowed the garden to grown at a stable pace, reduce near-term replanting, and manage maintenance costs. Ground cover and shrubs were strategically placed throughout the site.