Success Story: Street-side Bioswales
Hillsborough partnership builds street-side bioswales to manage stormwater runoff
Project Purpose
Odie Street in northwest Hillsborough was home to a mobile home community developed in the 1970s, with outdated infrastructure and a gravel road. Staff and volunteers from Habitat for Humanity of Orange County were rehabilitating the neighborhood with 22 new homes when they noticed recurring roadway flooding. Stormwater runoff was causing ditches to become deeper and wider, and the altered ditches were damaging the road. The Town of Hillsborough also observed that the conditions of the ditches were contributing pollutants from untreated stormwater runoff to the downstream Eno River, impacting water quality.
Under the leadership of the nonprofit Piedmont Conservation Council, the partners investigated how nature-based solutions could address water quality and flooding concerns while providing neighborhood beautification. They also assessed how green stormwater infrastructure could reduce nutrient pollution, which would help address water quality concerns in downstream Falls Lake.
Quick Facts
- Piedmont Conservation Council, the Town of Hillsborough and Habitat for Humanity of Orange County partnered with the community to use nature-based solutions to reduce recurrent street flooding and water quality issues.
- Hillsborough hosted two separate public workshops to inform the project design. Partners conducted workshops and provided informational materials in English, Spanish and Karen (a language spoken in Myanmar) to accommodate the large number of native speakers in the area.
- The Town repaired drainage ditches, installed water catchment structures and added rainwater filtering features like bioswales and treatment swales along Odie Street. The bioswales filter pollutants before water can enter the stormwater system and reach the Eno River.
- Soil properties and native vegetation are an important consideration for bioswales. Project partners chose soil and vegetation that enables the bioswales to encourage water infiltration, reduce stormwater velocity and remove pollutants during precipitation events.
Bioswales and Treatment Swales
Bioswales are shallow ditches designed to convey stormwater runoff, filter pollutants and improve water quality. Within a bioswale design, soils with high infiltration rates support natural pollutant removal processes. Planting the bioswales with vegetation enhances pollutant removal. Read An Introduction to Bioswales to learn more about their purpose, design and maintenance.
Like bioswales, a treatment swale is an engineered landscape that conveys stormwater runoff. Engineers use many types of swales to collect and clean stormwater. A treatment swale, as it is referred to in the Odie Street project, is essentially a grass swale with small concrete check dams. This type of green infrastructure can be easier to construct if a stormwater ditch already exists and simply needs to be retrofitted. Treatment swales help filter out pollutants and convey stormwater but are generally considered less effective than bioswales.
Spotlight on Equity
Odie Street is part of the Fairview community, a historically underserved area within Hillsborough. To ensure former and new residents of the Fairview community would have the opportunity to inform the project design, Piedmont Conservation Council, Habitat for Humanity and the Fairview Community Watch Group partnered with the Town in the spring of 2022 to hold two public workshops. They hosted one workshop in English and one workshop for local Karen people. Community members helped with translations. Residents provided feedback that affected planning and design decisions.
| Key Info | |
|---|---|
| Location | Hillsborough, N.C. |
| Estimated Costs | $400,000 |
| Published | March 1, 2024 |
| Project Contact |
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| Heather Fisher Stormwater Program Coordinator Town of Hillsborough heather.fisher@hillsboroughnc.gov (919) 296-9622 |
| Related Resources |
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- As they acquired the old homes on Odie Street for redevelopment, Habitat for Humanity used a phased approach that considered the housing needs of existing residents. When the organization noticed flooding concerns along the main road, staff consulted with the Town of Hillsborough Stormwater and Environmental Services Division.
- The Town of Hillsborough and Habitat for Humanity discussed potential solutions to ease flooding during and following redevelopment. They developed a conceptual plan for integrating nature-based solutions with the redevelopment.
- The Town of Hillsborough and Habitat for Humanity partnered with Piedmont Conservation Council to obtain funding for the project.
- Habitat for Humanity began the house reconstruction along Odie Street in 2019. While house construction continued, the Town regraded the ditches in 2021 and paved the road in 2022.
- During the public workshops, the Town showed homebuyers how they would play a role in managing the bioswales within the public street right of way. Piedmont Conservation Council hired a consultant to incorporate input from homebuyers into the bioswale design.
- Piedmont Conservation Council hired a contractor to construct the bioswales and treatment swales in December 2022. The contractor identified additional constraints, including utilities conflicts, which led to several bioswale location changes.
- Habitat for Humanity volunteers installed sod and planted the bioswales with natives species in early 2023.
- The Town of Hillsborough plans to organize volunteer workdays each spring to support homeowner maintenance and evaluate how the bioswales are doing. The first maintenance event is scheduled for spring 2024, including new mulch and plant replacements as needed.
- The Town of Hillsborough calculated the total costs for the Odie Street green infrastructure project at $397,799. These costs include design and construction of the bioswales, treatment swales, rain barrels and rain gardens, as well as the cost of workshops, educational events and ongoing site monitoring.
- The Piedmont Conservation Council, a resource conservation and development nonprofit, provided a $23,383 grant to fund infrastructure development along Odie Street. An Environmental Enhancement Grant from the NC Department of Justice provided $145,820 for design, implementation and education. North Carolina State University received a $173,614 grant from the NC Land and Water Fund to test and monitor the water quality from the bioswales.
- The Town, Habitat for Humanity and Fairview Community Watch Group provided $54,982 in total match for the grants.
Town of Hillsborough, Habitat for Humanity, Fairview Community Watch Group, North Carolina State University, Piedmont Conservation Council
- Habitat for Humanity completed construction of 22 new homes along Odie Street.
- The Town of Hillsborough paved the roadway along Odie Street to update transportation infrastructure.
- The Town repaired drainage ditches, installed water catching structures like weir walls, and added rainwater filtering features like bioswales and treatment swales along Odie Street. This infrastructure will help prevent future flooding and stormwater issues.
- The Town also added features like rain gardens and rain barrels and removed invasive vegetation, planting native species in its place (Climate Connection, 2022).
- The Town has noticed community excitement around the new bioswales. Stormwater Program Coordinator Heather Fisher said, “People are excited about the project. It’s something that helps the environment, keeps the water clean and [is something] people can walk down the street and enjoy.”
- The project partners hope to use Odie Street as a showcase for how communities can use bioswales.
- The Odie Street project won the Stormwater Project of the Year: Green Infrastructure Award from the American Public Works Association of North Carolina. The Association cited the multiple partnerships and community outreach and engagement as major components in its decision (Town of Hillsborough North Carolina, 2023). The Odie Street project also received the 2024 Honors Award for Engineering Excellence in the Water and Environment category from the American Council of Engineering Companies of North Carolina (American Council of Engineering Companies, 2023).
Hillsborough Stormwater Program Coordinator Heather Fisher advises project managers from other communities to communicate the responsibilities of managing bioswales to homeowners upfront. These structures require regular maintenance. “Communicate regularly with homeowners about maintenance responsibilities and provide yearly support including training, free mulch and re-plantings.”
Fisher also recommends planning multiple roadside construction options in advance, noting that conflicts may arise with placing bioswales in some areas due to factors like utility lines. “Plan for at least two options for roadside retrofits like bioswales and treatment swales,” she says, “so that if one option is not feasible for a particular location, the other option might work.”
In addition, Fisher recommends hiring a third-party locating service to ensure that all underground utilities are identified and to include sod and mulch installation in the construction bid. “I would recommend having the contractors install the sod and mulch instead of using volunteers. We took on a little too much on our own and that complicated the process.”
Another one of Fisher’s recommendations is to install sod or mulch atop bioswale soil as soon as possible. Mulching helps prevent disturbance until the bioswale can be planted. Also, since the soils in a bioswale need time to settle after installation, she recommends having a plan and resources in place to check and add additional soil as needed during the waiting period between bioswale installation and planting.
Climate Connection. (2022). Orange County Welcomes UNC Eco-Studio Intern: Max Feldman. Retrieved from https://www.orangecountync.gov/CivicSend/ViewMessage/Message/185689
Town of Hillsborough North Carolina. (2023, September 22). Hillsborough Receives Stormwater Award. Retrieved from https://www.hillsboroughnc.gov/news/news/2023/9/22/1622/hillsborough-receives-stormwater-award.html