North Carolina Botanical Garden Education Center
Landscape Performance Benefits
- Captures and treats approximately 6,247,000 gallons of stormwater runoff annually, including all rain events under 1.5 in, or 75% of all storms.
- Eliminates the use of potable water for irrigation.
- Reduces summer parking lot surface temperature by 13.4° F using high-albedo pavers as compared to nearby asphalt.
- Saved over 5.5 billion BTUs in embodied energy by using recycled concrete to construct site walls instead of cast-in-place concrete.
- Attracts 6,300 participants annually with an average of 189 programs, classes, and events.
- Provides opportunities for approximately 250 volunteers and generates 10,700 volunteer hours annually, with an estimated value of $230,000. Total volunteer hours increased by 35% after the Education Center’s opening.
At a Glance
Swanson + Associates, P.A.
Former Land Use
100 Old Mason Farm Rd
Chapel Hill, North Carolina 27517
The North Carolina Botanical Garden (NCBG), a unit of the University of North Carolina-Chapel Hill, was founded in 1966 and is nationally known for its conservation programs, collections, and diverse educational offerings, including native plant studies, botanical illustration, and horticultural therapy. The mission of the NCBG is to inspire understanding, appreciation, and conservation of plants in gardens and natural areas and to advance a sustainable relationship between people and nature. The new NCBG Education Center was constructed in 2009 to replace a smaller, outdated 1970s building adjacent to an early-successional pine forest infested by pine beetles. The Education Center includes 3 adjoining buildings that surround a central courtyard and gardens. These facilities support diverse garden programs as well as plant-based research, camps, and a variety of public events. The Education Center is the first publicly-owned facility in North Carolina to earn LEED Platinum Certification.
- Development was sited on a ridge to minimize site grading and avoid disturbing nearby wetlands and sensitive habitats.
- Carefully-sited paths provide universal accessibility without the need for steps or ramps.
- A north/south building orientation optimizes passive and active solar energy opportunities.
- Patios and terraces create transitional spaces that enable patrons to move seamlessly from the more formal interior to the informal garden.
- 5,200 board-ft of pine and 100 board-ft of walnut window and door trim were timbered from on-site trees infested with southern pine beetle.
- Site walls are made of recycled broken concrete that was recovered from other projects in coordination with University Solid Waste officials.
- A 38,208-sf parking lot, made up of permeable concrete pavers over a 12- to 18-in-deep gravel base, provides storage for stormwater and allows captured runoff to infiltrate into the soil below.
- 3 bioretention basins treat excess runoff from parking surfaces.
- 15,000 sf of previously-existing paved vehicular roadway was rerouted and removed from within the garden’s boundaries to eliminate the potential conflicts caused by allowing vehicular traffic to bisect the site. Existing large, flat areas were dedicated to vehicular movement and parking to minimize grading impacts
- More than 340 regionally-appropriate species were planted, including Andropogon, Asclepias, Helianthus, Ilex, Panicum, Symphyotrichum, and Vaccinium.
- 8 aluminum above-ground cisterns with a total capacity of 54,400 gallons collect building roof runoff for dedicated irrigation reuse.
- 40 geothermal wells provide a ground-source heat pump for heating and cooling the building.
- New bus stops along 2 existing public bus routes service NCBG visitors.
The overarching challenge was to develop a low-impact, high-performance cultural venue capable of integrating indoor and outdoor educational exhibits while preserving and enhancing both natural and cultivated landscapes. The secondary challenge was to unify building and landscape to exemplify sustainable development practices. Lastly, the project required approval from numerous stakeholders and agencies, including the University of North Carolina at Chapel Hill, the Town of Chapel Hill, and the State of North Carolina. Although it was not a requirement, the NCBG took the initiative to pursue a LEED Platinum rating, the USGBC’s highest, in order to illustrate their environmental mission, demonstrate their commitment to conservation, and promote regional sustainability.
The primary challenge was solved through the use of unprogrammed flex spaces as a method of integrating indoor and outdoor educational exhibits. These areas are united by porches and terraces, which effectively create a third, hybrid space that enables patrons and programs to easily flow from inside to outside, and vice versa. Likewise, these adaptable and integrated spaces allow the NCBG to host a wider range of activities, maximizing the potential for programmatic use. To create a regional model of sustainability, the design team carefully placed the building within the site to minimize disturbance and maximize natural energy alternatives. Related strategies included using garden areas to cloak the buildings and reduce their perceived scale and using developed areas of the site to support geothermal heating/cooling and rainwater capture/reuse systems. The design addresses regulatory and LEED program requirements in numerous ways, the most significant of which was the protection of large areas of natural landscape. Not only did this preservation-focused approach support the NCBG’s identity as a conservation garden, it also helped to mitigate construction-related impacts and, in turn, reduce stormwater and drainage issues.
The permeable parking lot system cost about $324,000 more than a conventional asphalt or concrete lot. The client and the design team agreed early in the process to pursue a Platinum LEED rating, resulting in the acceptance of additional upfront capital costs that would be outweighed by other benefits.The cost of installing the parking lot permeable unit paving system, including subsurface structural gravels and concrete containment bands, was $460,000.The cost of a concrete lot would have been $145,190, and asphalt would have cost $126,821.
- Patience and persistence across the design team, client, and stakeholders are necessary to achieve high design standards. A designer’s ability to continually develop and refine these traits is essential, because these attributes foster the sustained commitment required to design, develop, and calibrate high-performance systems, which is required for long-term project success. For instance, the NCBG’s Education Center took over 15 years to complete, including 10 years in the design and construction phases and an additional 5 years of adjustments to the new landscape.
- As a major construction project with tight budget constraints, there were challenges to maintaining the design’s integrity and high standard of quality. The most significant conflicts emerged when cost-cutting measures collided with regulatory requirements. During the bidding, negotiating, and construction processes, many features were value-engineered out, resulting in certain compromises related to both design quality and sustainability. Some of the stormwater BMPs, as originally proposed, became impractical and expensive due to changing and newly-introduced regulatory requirements that were not necessarily intended for projects of this size and scope. The design team had to be agile in their ability to adapt the design and implementation when regulators were not very flexible in their interpretation of the rules. For instance, the basic structural components of many rain garden areas were installed by the contractor to meet code and acquire the Certificate of Occupancy, while the majority of plantings were phased in over time by donations and volunteer time to reduce the project’s upfront construction costs.
Permeable Paving: Belgard “Drainstone”, Belgard “Aqua-Bric”, Belgard “Holland”, Nicolock “SF-Rima”
Walkways: Chapel Hill Gravel (quarried in Chatham County, NC)
Bioretention Media: Carolina Stalite Company
Owner: North Carolina Botanical Garden
Landscape Architect (Lead): Swanson and Associates, P.A.
Landscape Architect (Stormwater): Howard A. Partner, PLA
Architect: Frank Harmon Architect
Schematic Design Program Facilitator: The Natural Learning Initiative
Civil Engineer: CMS Engineering
Structural Engineer: SGI Structural Engineers
PME Engineer: Padia Consulting, Inc
Sustainability Engineer: Consider Design
LEED Consultant: Systemworx
Role of the Landscape Architect
The landscape architect was involved with all phases of the design, including assisting with preliminary workshops and meetings to create a program document and, ultimately, a conceptual design for the site and buildings. The landscape architect was instrumental in obtaining approvals from local regulatory agencies, the University of North Carolina at Chapel Hill, the Town of Chapel Hill, and the State of North Carolina. The landscape architect worked with the design team to prepare design development plans for budgeting and material selection. Because of the project’s intention to obtain a LEED Platinum designation, the landscape architect was involved in every aspect of site development. The landscape architect developed site plans and construction documents and coordinated with other disciplines including another landscape architect who specializes in stormwater management. Finally, the landscape architect was involved in the site’s construction administration.
Case Study Prepared By
Research Fellow: Andrew Fox, PLA, ASLA, Associate Professor/University Faculty Scholar, North Carolina State University
Research Assistant: Sadie Walters, Student ASLA, MLA Candidate, North Carolina State University
Research Volunteer: Pei Chi (Peggy) Huang, MLA Candidate, North Carolina State University
Firm Liaison: David Swanson, PLA, ASLA