April 3, 2023

Sustainable Design in Civil Engineering

For over 60 years, Progressive Companies has been committed to innovative and sustainable designs that benefit our clients and communities. In this Earth Day blog series, we’re sharing knowledge and best practices we’ve learned along the way.

So far in this series, we’ve explored sustainable design best practices within the building itself, including architecture, mechanical, electrical, and structural engineering. The next two installments will focus on designing a sustainable site through civil engineering and landscape architecture.

Green Over Grey Everyday

When we approach site design, we are interested in preserving as much of the natural landscape as possible. We coordinate with architectural designers and landscape architects early in the design process to ensure buildings are positioned on the site to maximize passive environmental design, such as daylighting and ventilation, while also minimizing earth disturbance and preserving mature trees and natural elements. In addition to preserving the natural environment, smart grading and selective demolition can provide large reductions in operational carbon and substantial cost savings by limiting heavy equipment operating time. Our team relies on software such as SITEOPS and AutoCAD’s grading optimization tool to ensure that the project can incorporate many aspects of sustainable design early in the design process.

Low-impact development (LID) describes the practice of designing sites and stormwater management systems that most closely mimic nature. Historically, development practices have treated stormwater management as an afterthought, trying to handle the runoff from an entire site in a single isolated location. This hinders natural systems and creates a single point of failure when proper maintenance is neglected. In contrast to the old ways of development, the goal of LID is to capture storm runoff close to its source and use design techniques that infiltrate, filter, store and evaporate that water. Some of the best examples include green roofs, bioretention gardens, and permeable pavers. With LID, stormwater is treated as a resource rather than a liability. When we incorporate natural elements and systems into our site design, not only does it improve water quality and surrounding ecosystems, but it also elevates site aesthetics and improves the wellbeing of the people who use the site.

The Grand Rapids Downtown Market incorporates green roofs, live walls, pervious pavement, rain gardens, and curb bioswales

Materials

For site construction, the most prevalent materials we use are for pavements and pipes. The more innovative we can be with our material selection for these products the more sustainable our projects will be.

In the world of pavement selection, concrete is ubiquitous for its high strength and versatility. However, concrete has one of the largest carbon footprints of any construction material. With this knowledge, our site design process seeks to minimize the carbon impact of concrete pavement by replacing, reducing, and specifying. The first goal is to replace concrete with other more sustainable pavement materials, where possible. Next, where concrete is required, we aim to reduce the paving area to the required needs of the site and eliminate unnecessary pavement. Finally, we are continually reviewing and improving our concrete specifications so that we are using the best mixtures for performance and carbon reduction.

There are many new products entering the market that provide sustainable solutions. Pervious pavements and permeable pavers that allow groundwater to filter through can minimize runoff into storm drains, reducing the size of drainage pipes. Pavers are becoming especially popular because they look great and perform well throughout their lifecycle, especially in northern climates with freeze-thaw cycles.

Ada Village utilized pervious pavers in their downtown redesign

One of the pervious pavement options is Flexi®-Pave. It’s an environmentally friendly material that is made partially of recycled tires and can be used for walkways, tree surrounds, and more. It doesn’t require heavy equipment to install it, further reducing its carbon footprint. Another product growing in popularity is decomposed granite, which we recently used on the Rosa Parks Circle project in Downtown Grand Rapids.

Flexi®-Pave used for a parking area and walking trail

Pipe materials are another way we can limit carbon. Although concrete is still a popular material with many municipalities, high density polyethylene (HDPE) pipes are a more sustainable option. HDPE pipes are made of largely recycled materials and research has shown that plastic pipes have a lower total greenhouse gas contribution when compared to alternatives in most applications. Corrugated metal pipes are another option, which use recycled steel.

Product manufacturers within our industry are beginning to share how much carbon was emitted in producing their materials through an Environmental Product Declaration (EPD). Being able to select manufacturers that track and limit their carbon output is another way we can lead in sustainable design. As manufacturers continue to provide EPDs, engineering firms can make changes to their specifications to select for materials that have a lower carbon footprint.