The George W. Bush Presidential Center

Challenge

After construction of the building, the landscape architects were left with 100,000 cubic yards of excess fill created from excavations. The fill needed to be dispersed on the landscape in a manner which would support the design goals.

Solution

The fill was reused on-site as an asset to transform the flat and faceless site into a system of valleys, ridges, and plateaus. This topography added a complexity for every biotic system in the park by creating distinct balances of sun, water, and wind. Instead of creating a landscape which was solely a collection of plants, this project aimed to establish functioning ecological systems. The calculated changes in topography assisted in creating the microclimates needed to support various functioning systems.

• The park provides the largest open space on the Southern Methodist University campus and the University Park neighborhood.
• The intricate topography of the site was created with 100,00 cubic yards of fill from the building excavation process.
• Approximately 2,650 linear feet of vegetated bioswales, seeps, and a wet prairie create a dynamic stormwater system, which slows, filters, and collects nearly all rainwater that falls on the site. Underground pipes direct runoff from the parking lots into the seeps and swales.
• Water flows from the wet prairie to a 250,000-gallon underground cistern located at the bottom of the site where it can then be used for irrigation.
• The landscape plan includes over 90 native species, with grasses like big bluestem and switchgrass and wildflowers such as goldenrod, coneflowers and eryngo.
• More than 900 native trees were planted, including Possumhaw, Live Oak and Texas Persimmon.
• Over 350,000 native plant plugs were installed. Plant plugs were chosen instead of seeds to ensure establishment.
• The lawn is the largest use Habiturf™, a mix of native grass species that was specially formulated for the project by the Lady Bird Johnson Wildflower Center.
• Over 65,000 cubic yards of quality soil was repurposed from a neighboring field.
• Soil mixes, specialized for each vegetation type, were made using only organic soil amendments. A unique organic soil amendment was composed for each type of vegetation type.
• Locally-sourced limestone was used for all of the stone work, including the walls, seeps, outdoor amphitheater, and boulders.
• The three pedestrian bridges are made from lumber sourced from US-grown Black Locust.
• The landscape is maintained with solely organic amendments.

In an effort to gain knowledge about the performance of certain plant species, Michael Van Valkenburgh Associates (MVVA) led the creation of a 8,150-sf mock-up on the site. The mock-up allowed the team to test which prairie species and native lawn mixes would best suit the climate and proposed soils. In addition to plants, the mock-up provided the design team with a chance to test erosion control systems, shade structures, irrigation techniques, and various soil mixtures. Data on slope stability, water use and plant growth were compiled every two weeks. After monitoring the mock-up for 15 months, the observations were used to create the final design for the Bush Presidential Center landscape.

The mock-up assisted the design team greatly when it came to deciding on an ideal grass mix for the native lawn. Unlike most lawn construction, there was no pre-grown sod to use for establishing the native lawn because there were no growers yet specializing in this type of lawn. The landscape architects had to choose between seeds and a few small scale providers of plant plugs. The mock-up proved to the designers that seeds would be successful for this large lawn.

Black Locust was used for the construction of the pedestrian bridges. It is a US-sourced hardwood resistant to rot and insects. Because of its strength, the wood does not require chemical pressure treatments. Black locust also has a longer service life than chemically treated woods common for outdoor use, such as pine and cedar. The cost of black locust is $169.26/plank compared to $44.97/plank for pressure treated wood. For all three bridges, the total cost was about $51,300 for the black locust compared to $13,600 for standard pressure treated wood. The designers and client felt that the benefit of using a sustainably sourced and long-lasting wood outweighed the higher cost.

• The planting design called for a large amount of native plant material. Finding the various plants was difficult as many nurseries did not carry these species. As a direct result of the demand for native plants from this project, more nurseries in the region have begun to grow a larger variety of native species for large-scale commercial purchase.
• The client requested that the park landscape be developed by the time of the grand opening. All ecologies were to be in place and functioning within a very short time period. In an effort to expedite the construction and implementation process of the project, MVVA hired various consultants to work on the project simultaneously. This endeavor proved to be quite difficult to manage, though the end result was positive. Three landscape contractors, one which focused on soil, one on tree installations, and the third on plantings alongside three stone work contractors, one focusing on flat work, one formal walls and the third on the naturalized features all had to be managed by the MVVA team.
• In order to meet the grand opening date, certain areas of the landscape that were known to take more time to establish had to advance ahead of others and many plants had to be seeded or planted outside of the ideal planting window. Planting in the middle of the summer meant that there were additional maintenance and irrigation costs. Contractors had to observe plant health and in some cases overplant to account for plant mortality. The positive outcome of this process was that the team was able to observe which plants were resilient even in such harsh conditions and learn from this.
• Establishing the Habiturf™ provided many lessons to both the designers and the botanists at the Lady Bird Johnson Wildflower Center because it was the first large-scale implementation of the “native lawn”. One critical lesson took place during the establishment of the lawns north of the building. This area would be highly visible and under high foot traffic. Due to the short construction time, the lawn had to be seeded during the hot summer, outside of the typical seeding window. The seeds were failing, which lead the team to to take planting plugs out of another section of healthier lawn. The transplant mended the high traffic area but it also opened up areas for invasion in the once healthy plot. Two years later there are still maintenance issues in the section of lawn where the plugs were taken.

Engineered Planting Soils: Greenchoice, Corsicana, TX
Stone Pavement: Leuders Limestone, Supplied by Mezger Enterprises, LTD, Lampasas, TX
Granular Walkways: Stabilizer Solutions, Inc., Phoenix, AZ
Trash and Recycling Receptacles, Ash Urns: Landscape Forms, Kalamazoo, MI
Wood Bench: Country Casual, Gaithersburg, MD
Bike Racks: Creative Pipe, Inc., Rancho Mirage, CA
Geofibers: Stabilizer Solutions, Inc., Phoenix, AZ
Geogrids: Tensar International Corporation, Alpharetta, GA
Stone Wall, Seep, and Forebay: Leuders
Limestone: Mezger Enterprises, LTD, Lampasas, TX
Poles: King Luminaire Company, Northport, AL
Prairie Lights: HessAmerica, Gaffney, SC
Irrigation System: Rainbird Sprinkler Manufacturing Co, Azusa, CA
Bridge Decking: CitiLogs, Pittstown, NJ
Irrigation Cistern: Atlantis Corporation, Chatswood, Australia

Project Team

Landscape Architect: Michael Van Valkenburgh Associates, Inc.
Architect: Robert A.M. Stern Architects LLP
Irrigation Consultant: Jeffrey L. Bruce & Company, LLC
Soil Scientist: Olsson Associates
Ecologist & Prairie Consultant: Lady Bird Johnson Wildflower Center
Prairie Consultant: Sustainable Growth Texas, LLC
Fountain Designer: Waterscape Consultants, Inc.
Civil Engineer: URS Corporation
Traffic and Parking Engineer: DeShazo, Tang & Associates, Inc.
Structural/Blast Engineer: Walter P. Moore
Security Consultant: Kroll Security Group, Inc.
SMU Boulevard Civil Engineer: Raymond L. Goodson Jr., Inc.
Surveyor: Raymond L. Goodson Jr., Inc
Geotechnical Engineer: Terracon Consultants, Inc.
Construction Manager: Manhattan Construction Company
Arborist: Environmental Design, Inc.

Role of the Landscape Architect

MVVA contracted directly with the Bush Foundation to enable a reciprocal exchange with the architect and client. As the leaders of the site planning and designers of the park, they presented ideas to President and Mrs. Bush, the community, public agencies, and the President of SMU. MVVA led the design for stormwater management, worked to obtain LEED credits for the site, and hired specialty consultants for soil, the prairie, and irrigation. To test their design concepts, the designers organized the making and monitoring of a 8,150-sf mockup of the plant systems, and they continue to be involved in the establishment and management of the park.