Green design in civil engineering

May 2014 » Project + Technology Portfolio » Environmental
Rain gardens and low-impact channels pay long-term dividends.
Chris Weigand, P.E.


Rain gardens typically will not increase the cost of a project when they are planned appropriately to replace other landscaping or mandatory water quality or retention measures. Photo: Courtesy of Big Red Dog, DWG Landscape Architecture, and City of Austin, Texas

Every time you see a new building enter a skyline, chances are it incorporates some type of green element into its design. When it comes to civil engineering, the term “green” is ambiguous, and many people have misconceptions regarding implementing eco-friendly materials and designs into a project. The good news is that advances in technology allow buildings to be green in new and innovative ways.

Green design not only benefits the environment, but also provides value to the owner or tenant because the buildings are much more efficient. Such designs include wastewater reuse, rooftop gardens, and solar energy systems. Some of these details may seem small at first, but the benefits of using them pay off in the long run. 

Big Red Dog has implemented several rain gardens in Austin, Texas, and low-impact channels in San Antonio. In the case of rain gardens, the structure is designed to capture certain depths of rainwater, which then filters through dirt and tree roots to remove hydrocarbon from parking lots. In essence, it’s a natural filter as opposed to a man-made filter.

Hydrocarbons are removed in a process that is designed to mimic the way nature filters water. With properly selected soils and plants, the hydrocarbons are captured on the surface of the soil particles and absorbed by the plants’ roots. Plants also can significantly reduce nitrogen and phosphorus in stormwater.

Rain gardens vary significantly depending on the storm size, the area of the country, application, and other factors. When designed correctly, rain gardens can remove more than 95 percent of total suspended solids, as well as 75 percent or more of nitrogen and phosphorus.

These rain gardens typically will not increase the cost of the project when they are planned appropriately to replace other landscaping or mandatory water quality or retention measures. These systems are typically utilized when the regulating entity mandates water quantity or quality measures. As an added bonus, the systems do not have a significant effect on the timing of construction.

At Big Red Dog, most single-family and multifamily building clients are interested in these opportunities. However, they are most cost effective on new suburban developments, where there is space to include these opportunities. Developers of urban sites often struggle to find the land area to implement these measures. 

As regulators continue to provide incentives for green technologies, we anticipate that 35 to 50 percent of developers will implement these technologies. As more developments include these measures, it can reduce the cost of maintaining underground drainage systems within urban environments. This may reduce the necessary capital expenditures by regulating entities within these watersheds. 


When designed correctly, rain gardens can remove more than 95 percent of total suspended solids, as well as 75 percent or more of nitrogen and phosphorus from stormwater. Photo: Courtesy of Big Red Dog, DWG Landscape Architecture, and City of Austin, Texas

In addition to rain gardens, Big Red Dog has completed projects designed with low-impact channels as a part of parking lot structures. Although these projects may require more work from the design standpoint, their aesthetics, dual purpose, and long-term savings make them a home run for clients and the general public. Water is such a precious resource, especially in Texas, that we can’t afford not to pay attention to how we use it.

The goal of low-impact channel design is to mimic the effect of natural streams, including small eddies and pools within the channel to slow water flow. These areas of slower water allow particulates to settle in the channel and prevent them from getting into natural water systems. In addition, specific natural grasses and plants are planted; a low-impact channel shouldn’t use concrete. However, it is not necessary that concrete be used in traditionally designed channels. 

Over time, these green features will reduce the cost of irrigation. However, proper maintenance will likely mimic the cost of maintaining other landscaping or other water quality measures. On the bright side, construction does not take additional time and there typically isn’t any significant additional cost.


Low-impact channels may require more work from a design standpoint, but community benefits include aesthetics, dual purpose, and long-term savings. Photo: Big Red Dog

Developers rarely request low-impact channels, but we often recommend them. Because they are used primarily by private developers, they will not significantly reduce taxpayers’ costs directly. However, their use in public developments provides a better end product for trail systems linear parks similar to the Mission Reach redevelopment project completed by Bexar County in 2013.

When designing a new building, whether a skyscraper or a modest apartment complex, clients are asking engineers and architects to design more energy-efficient buildings. This push from the public means designers and engineers are at liberty to integrate green initiatives into their building designs.

With citywide revitalization efforts currently taking place in San Antonio, integrating green technology into new and existing buildings will give our city not only a cleaner environment but a better working ambience. In addition, tourists will have a cleaner city to visit and remember for years to come. And as government entities begin to regulate eco-friendly technologies, we hope they will make the process as smooth as possible to encourage engineers and developers alike down the green path. Technology and public policy are always evolving, and as an advocate for green designs, it’s a great time to be a civil engineer.

Chris Weigand, P.E., is president of Big Red Dog’s (www.bigreddog.com) San Antonio, Texas, operations. The firm specializes in civil engineering design, permitting, and land use consulting for real estate and natural resource development.


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