May 01, 2009

Streamlining Sustainability

Madison, Ala., a suburb of Huntsville, has about 37,000 people and is growing fast. To help maintain its small-town charm, commercial developers are encouraged to use “green” building practices. This means engineering firms are being asked to integrate U.S. Green Building Council Leadership in Energy and Environmental Design (LEED)-certified building principles and other cutting-edge sustainable concepts into their designs.

Design Software

Recently, a pair of office buildings comprising about 85,000 sq ft was being planned in Madison. 4Site Inc., a Huntsville engineering firm specializing in environmentally friendly design, was selected to design the project’s innovative rain gardens.

The challenge encountered on this LEED commercial development site was to find a more efficient way to model sustainable designs for rain gardens and residential storm water networks. In the past, the firm’s mostly manual approach had proved time-consuming and left room for error.

4Site researched available low-impact development modeling options before selecting BOSS Intl.’s StormNET, which enables engineers to perform urban storm water quality modeling using rain gardens, green roofs, retention ponds, wetlands and more. The software program integrates water quality capabilities and EPA-SWMM, allowing the firm to model the entire project in a single application.

“What we had in house did not effectively address low-impact development or sustainable design,” said Jerry Cargile, P.E., principal partner for 4Site. “It really hampered productivity, especially with projects as complicated as residential storm water networks. We needed a modeling program that could handle sustainable design and work well with Civil 3D.”

Implementation & Benefits

Using the software, engineers noted 10- to 15-percent higher flow rates, enhancing project accuracy. Rather than develop a conventional storage detention pond with a typical outflow structure containing orifices and weirs, Madison project engineers were able to specify the soil types of the underlying infiltration layer to better manage runoff and infiltration.

Project Manager Jackie Whitaker used EPA-SWMM along with HEC-1 in StormNET. With the advanced detention storage modeling capabilities, Whitaker specified infiltration rates based on the types of soil 4Site planned to use in the rain gardens to control discharge rates. At the same time, he could adjust storm water pipe sizes directly in the model, and with each change, he could run the model to determine the impact of various storm events and make adjustments in real time.

“[The software] lets us model the entire project as a whole instead of in parts,” Whitaker said. “It handles flow calculations, hydraulic grade lines and lets us update pipe sizes—all within the software.”

Modeling in one application—without manual calculations and with tight Civil 3D integration—reduces errors, enhances design accuracy and saves time.

“With this LEED rain garden project, we saved at least a day’s worth of time,” Whitaker said. “We have more time left over to look at designs and pull them together into the complete package to send out.”

About the author

Casey Hibbard is with Compelling Cases Inc. Hibbard can be reached at 303.494.5785 or by e-mail at [email protected].