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Green Infrastructure for Stormwater Management

FOX Engineering Associates, Inc. began initial phases of planning and design for the Ames Water Treatment Plant (WTP) in 2008. Through analysis of the city’s facilities, it was determined that a new, larger facility was needed to meet future water demands. For the new site, Ames selected a 44-acre property previously used by the United States Department of Agriculture as a research facility. This location allowed the use of existing infrastructure for future operations. The new facility’s planned development included improvements to approximately 19 acres of the property to meet the city’s needs.

On April 22, 2014, the city adopted a “Post Construction Stormwater Management Ordinance” requiring that new developments meet more stringent stormwater management criteria. However, design and approval of plans for the new Ames WTP would be completed prior to full adoption of the ordinance. The Water Pollution Control Department staff decided that it was essential that this facility be designed to include water quality practices that would demonstrate the city’s commitment to the benefits of such practices. They wanted to meet the requirements of the new ordinance and go beyond to include additional practices. This would create a landscape of Best Management Practices (BMPs) to showcase water quality practices within Ames.

Stormwater management has an essential purpose; manage surface runoff and prevent ill effects from development downstream. This is vital in urban areas where the ground surface is not permeable and infiltration is reduced. Highly developed areas have impervious surfaces, such as pavement and roofs, that prevent precipitation from naturally soaking into the ground.  Instead, water runs away from these surfaces into storm drains, storm sewers, and drainage channels, sometimes at a high rate of flow. This can cause downstream flooding, stream bank erosion, increased turbidity, habitat destruction, and even damaged infrastructure or contaminated water bodies in extreme cases.

Traditional stormwater management generally includes restricting the peak flows from a development to match the flows prior to development. Unfortunately, this does not mitigate the volume of water that is produced from the increase in impervious areas and only dislocates high water loads. Modern approaches require that the natural water cycle be rebuilt to allow stormwater runoff to infiltrate and recharge the groundwater where possible.

Green infrastructure, often referred to in stormwater management as Low Impact Development, generally includes approaches and technologies to reduce the impacts of development by promoting infiltration, evapotranspiration, and capture/reuse of stormwater to maintain or restore the natural hydrology in the environment.

FOX Engineering completed a site design for the facility that incorporates a variety of Green Infrastructure stormwater practices. This includes an extended detention facility to meet the required stormwater site discharge requirements, two bioretention facilities to provide water quality treatment of runoff from impervious parking areas, a bioswale to treat runoff from the city’s maintenance area, grass swales to promote infiltration in drainage channels, and restoration of habitat to native plantings to further reduce runoff.

The locations of these practices were chosen because they provide a “treatment train” of practices to reduce runoff and to promote infiltration prior to discharge from the site. In addition, by including over 10 acres of native grass seeding within the 19-acre development, the facility improvements are able to return a large portion of the development back to a native landscape.

Incorporation of stormwater management practices into the site development greatly reduces the stormwater runoff and provides water quality treatment from impervious areas.  Incorporating these water quality practices greatly enhanced the city’s facility and provides the city an opportunity to demonstrate the benefits of these practices to ensure clean water for future generations.

 

FOX Engineering is an environmental engineering firm based in Ames, Iowa. We specialize in water and wastewater solutions for our diverse municipal and industrial clients. Our work varies in size and scope and can be found throughout the Midwest and beyond.