Evaluating storm impacts in real time

January 2012 » Web Exclusive » PROJECT CASE STUDY
Integrated civil engineering design software and hydrology & hydraulic modeling tools improve efficiency and project quality.

For many years, civil engineering firm 4Site Inc. has used model-based design software to develop and deliver its master planning and land design solutions. But until recently, the firm was forced to use manual methods to analyze its stormwater management designs.

LEED Gold commercial development with associated site improvements

Civil engineer

4Site Inc.

Product application

Civil engineers quickly test and evaluate multiple design options using Autodesk Storm and Sanitary Analysis software and AutoCAD Civil 3D software.

Based in Huntsville, Ala., 4Site has served clients throughout the Southeastern United States for more than 25 years, delivering designs that balance creativity with the demands of science, technology, and business. 4Site recently adopted Autodesk Storm and Sanitary Analysis software, a fully dynamic hydrology and hydraulic modeling tool that is closely integrated with AutoCAD Civil 3D, the firm’s existing design software. This software combination helps 4Site quickly test multiple design options and evaluate their impacts in real time — an approach that results in designs that are more sustainable and cost effective, helping to provide a higher return on investment for the firm’s clients.

Before adopting Storm and Sanitary Analysis software, 4Site designers initially defined projects in Civil 3D software, but had to alternate between Civil 3D, manual calculations, and non-integrated software until they discovered the optimum pipe sizes by trial and error. This time-consuming, cumbersome approach seriously hampered productivity, especially on projects that involved complex stormwater networks and numerous integrated management practices such as bio-swales and rain gardens. And not only was the process inefficient, it did not effectively address low-impact development or sustainable design.

At a minimum, 4Site wanted a solution that included the U.S. Environmental Protection Agency Storm Water Management Model (EPA-SWMM), a dynamic rainfall-runoff simulation model that would enable them to consolidate all project modeling in Civil 3D. After careful research, 4Site selected the Storm and Sanitary Analysis software for its ability to quickly model and analyze stormwater systems containing a variety of elements, including rain gardens, green roofs, retention ponds, and wetlands. Plus, the analysis software integrates easily with Civil 3D and has very broad stormwater modeling capabilities, which helps the firm handle almost any design situation it encounters.

LEED site development
One of 4Site’s first projects with the software was an 85,000-square-foot commercial development project in Madison, Ala. The owner hoped to achieve LEED for Core and Shell certification on the project, which included two office buildings and associated site improvements (Figure 1).

Figure 1: Civil 3D and Storm and Sanitary Analysis helped 4Site plan and size individual rain gardens more efficiently, saving time. Image: 4Site Inc.

4Site engineers designed the project using Civil 3D and then exported data from the Civil 3D model into Autodesk Storm and Sanitary Analysis software to analyze the stormwater network. During the design process, 4Site’s engineers were able to model the entire project as a whole instead of in parts, adjust stormwater pipe sizes on the fly, see the impact that various storm events would have on the proposed system, and then make adjustments in real time. The analysis software handled flow calculations and hydraulic grade lines, and enabled the firm’s engineers to update pipe sizes in a single step, without lengthy manual calculations.

Using Autodesk Storm and Sanitary Analysis software advanced modeling tools, the firm was able to accurately model the many rain gardens throughout the site by specifying their individual infiltration rates instead of relying on traditional outflow structures (Figure 2). This enabled 4Site to better manage runoff and infiltration throughout the site and limit the size and cost of the associated stormwater infrastructure.

Figure 2: Civil 3D and Storm and Sanitary Analysis helped 4Site model infiltration of stormwater accurately for a parking lot incorporating multiple rain gardens. Image: 4Site Inc.

The project was extremely successful and achieved LEED Gold Certification utilizing site credits for both stormwater quality and quantity, with more than 50-percent reduction in potable water use for irrigation. The combination of Civil 3D and Storm and Sanitary Analysis software from Autodesk helped 4Site designers more efficiently and accurately model the stormwater runoff flow than was possible with its previous modeling approaches, while also providing the documentation necessary for validation of the LEED credits. The resulting design was more accurate because the level of detail was greater, and the project was more cost effective and completed faster. Plus, there was a seamless transition from model to final construction documents, which made sharing the project design with the client and local governing agencies easier and clearer.

Storm and Sanitary Analysis increased the firm’s design efficiency and improved its QA/QC by limiting manual input and eliminating the use of non-integrated software. Ultimately, the reliance on integrated civil engineering design software and hydrology & hydraulic modeling tools increases 4Site’s efficiency and flexibility, as well as improves productivity and client satisfaction.

Jackie Whitaker, P.E., LEED AP, is with 4Site; and Teresa Elliott is with Autodesk.

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