Tennessee Valley Authority Economic Development
Sustainable Development Guide
Section 3: Site Development
These are the basic principles of better site development:
Protect and create natural open space
Promote the use of combined-access roads off collector roads
Direct rooftop runoff to vegetated areas
Plan for open-space management
Protect and create natural open spaces
This principle reduces the built area on a site and increases the amount of open space that works as part of a storm-water management system. It can improve the overall appearance of an industrial park, minimize total impervious area, reduce construction costs, conserve natural areas, provide recreational space, and promote watershed protection. Studies show that open space design can reduce imperviousness by 40 to 60 percent. (1) Less impervious cover translates into less storm-water runoff. (2)
Open space should be more than the unbuildable areas of a site. Formal open space is a planned and structured area that includes designed landscape plantings. It is regularly maintained and may include streetscape furnishings, recreational improvements (playground, swimming pool, tennis courts, etc.), and street improvements. Examples include squares, plazas, and parks.
Informal open space, on the other hand, is typically larger than formal open space, is more amorphous in configuration, and often incorporates environmentally sensitive lands such as a floodplain, forested area, steep slopes, or wetlands. Informal open space may have minimal improvements such as bike or walking trails. Examples include greenways, large parks, pastoral spaces, and recreational fields. Open space left in a natural or informal state has few maintenance needs or costs — an incentive to use this approach. (3)
Two examples from the Georgia Stormwater Management Manual demonstrate the benefits of applying conservation-design as opposed to conventional principles to industrial development. Figures 3a and 3b compare conventional and conservation designs for an office park development. In Figure 3a the site is graded to fit the building layout and parking area. All of the vegetated areas of this site are replanted. The layout in Figure 3b preserves undisturbed vegetated buffers and open space areas on the site. Both the parking areas and buildings are designed to fit the natural site terrain. In addition, a modular porous paver system is used for the overflow parking. (4)
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3a. Conventional Design for an Office Park (from Office Park Example: page 1.4-34 Georgia Stormwater Management Manual) |
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3b. Conservation Design for an Office Park (from Office Park Example: page 1.4-34 Georgia Stormwater Management Manual) |
Figure 3c shows a typical commercial development containing a supermarket, drugstore, smaller shops, and a restaurant on an outlot. The majority of the parcel is a concentrated parking lot area. The only pervious area is a small replanted vegetation area acting as a buffer between the shopping center and adjacent land. Storm-water quality and quantity control are provided by a wet extended detention pond in the corner of the site.
Figure 3d shows a conservation design for commercial development. Retail buildings are dispersed on the property, providing more of an "urban village" feel, with pedestrian access between buildings. Parking is broken into smaller areas, and bioretention areas for storm-water treatment are built into islands. A large bioretention area located at the main entrance to the shopping center serves as open green space. A larger buffer is preserved. Because bioretention areas and the buffer provide water quality treatment, only a dry extended detention basin is needed for water quantity control. (5)
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3c. Conventional Design for Commercial Development (from Commercial Development Example: page 1.4-37, Georgia Stormwater Management Manual Volume 2 (Technical Handbook)) |
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3d. Conservation Design for Commercial Development (from Commercial Development Example: page 1.4-37, Georgia Stormwater Management Manual Volume 2 (Technical Handbook)) |
Refer to the following document for more information about these best practices:
Environmental Protection Agency Post-Construction Storm Water Management
Minimize setbacks
Establishing front and side setback distances helps ensure uniform development. Although building codes may not dictate setbacks on industrial lots, aesthetic choices may dictate how far buildings should be from the street and from other buildings. As these requirements increase, density decreases. Setbacks can limit or prevent planners from designing open spaces and they tend to increase site imperviousness.
Smaller setbacks and frontage distances are essential for open space design. Reducing front setbacks for parcels can shorten driveways, one of the main sources of imperviousness in industrial developments. Shortening setbacks may raise concerns about reducing sight lines for roadways. However, front setbacks that provide adequate sight lines are often less than the 30 feet required by many communities. (6)
Promote the use of combined access roads off connector roads
Shared access roads reduce the overall impervious area of a site. They also require developers and owners to clearly define maintenance obligations.
Direct rooftop runoff to vegetated areas
Many industrial buildings have large rooftops. Directing their runoff away from roadways and storm-water conveyances can reduce water volume and pollutants entering streams. Rooftop runoff can be routed to underground storage or infiltration basins. It is relatively free of pollutants that clog filter fabric and fill up sediment forebays, compromising their useful life. Other conventional practices (like ponds) that receive only water from the roof can be designed more simply. The Challenger Center in Chattanooga has a constructed wetland that receives roof and parking lot runoff.
Use green roofs
Rooftop greening is increasingly common in Europe and elsewhere. This practice involves growing vegetation on roofs to intercept rainfall and promote evaporation rather than runoff.
Roofs cover a significant portion of the urban landscape and generate large volumes of storm-water runoff. Green roofs are designed with extra support and special membranes to hold the soil and plants. They absorb and slowly release excess rainwater.
The benefits extend beyond water quality. Green roofs also have substantial aesthetic benefits. They make a building more pleasant to look at, and some vegetated roofs, known as "intensive" green roofs, are designed to be accessible and used as park and building amenities.
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| Fencing Academy of Philadelphia vegetated roof cover. |
Green roofs conserve energy by keeping roofs cool in the summer and insulated in the winter. They save money by reducing the land area needed for storm-water management, which is especially important in densely populated areas with high real estate values, and by extending the life of a roof. Vegetated cover reduces the wear caused by temperature-related expansion and contraction and protects the roof from the ultraviolet radiation and cold winds that break down traditional roofing materials. Roof gardens typically have a 50-year lifespan. (7)
Plan for open-space management
To successfully work as part of a storm-water management system, clear performance criteria are needed for open space maintenance, allowable uses, and future management. A legal document recorded with the deed can establish maintenance requirements. This document should:
- Delineate the location, area, and type of all open spaces and the requirements for maintenance.
- Designate an entity with perpetual responsibility for maintaining them.
- Outline a procedure for routinely inspecting and reporting maintenance to the local storm-water authority.
Four options for designating responsibility for open space management are:
- Conservation easements
- Land trusts
- Community associations
- Public ownership
Refer to the following document for more information about these best practices:
Environmental Protection Agency Post-Construction Storm Water Management