Construction and land development projects can result in increased stormwater runoff and soil erosion, which contribute to more frequent and increased flooding, erosion, sediment transport and deposition, loss of structures from high runoff rates, and pollution of streams, lakes, and reservoirs. As stormwater flows over a construction site, it can also pick up pollutants that contribute to water quality problems.
Because the Illinois Department of Transportation (IDOT) emphasizes proper stormwater management and best management practices for erosion control and sediment transport, it initiated a project in 2011, “Installation and Performance Testing of Ditch Checks and Inlet Protection Structures” (R27-102).
The Illinois Center for Transportation (ICT) project was led by Prasanta Kalita, professor in the Department of Agricultural and Biological Engineering at Illinois. Co-investigators were Rabin Bhattarai, assistant professor in the Department of Agricultural and Biological Engineering at Illinois; Marcelo Garcia, professor in the Department of Civil and Environmental Engineering at Illinois; and Heidi Howard, research agronomist, and Niels Svendsen, agricultural engineer, with the U.S. Army Corps of Engineers Construction Engineering Research Laboratory (CERL).
The research team was assisted by several students from the University of Illinois at Urbana-Champaign: Anwar Azeem, Vaskar Dahal, Carlos Bulnes Garcia, Sudip Gautam, Ranjeet Jha, and Joseph Monical.
Joseph Vespa, Engineer of Technical and Product Studies for IDOT, served as chair of the Technical Review Panel that oversaw the project. He says, “This research project was undertaken to evaluate a variety of temporary ditch check, curb inlet protection, flared inlet protection, and ditch inlet protection products in a controlled environment. Previous attempts to evaluate these products on construction sites provided inconclusive findings because of varying installation practices and precipitation levels.”
A ditch check is a small, temporary or permanent dam constructed across a drainage ditch, swale, or channel to control runoff in order to reduce erosion and allow sediment and other pollutants to settle out. An inlet protection device is installed to prevent sediment from entering a storm sewer.
The project was conducted at the Erosion Control Research and Training Center (ECRTC) near the South Farms of the University of Illinois at Urbana-Champaign. The facility was established in 2010 with a $450,000 grant from IDOT and administered by ICT in partnership with CERL.
According to Bhattarai, having access to the ECRTC allowed the tests to be conducted under the same experimental conditions so that their performance could be compared. “We were also able to evaluate the products for Illinois soil and weather conditions, and due to the site’s proximity, the project’s TRP members were able to stop by and observe the tests,” he says.
One of the major challenges faced during the project was the weather—the experiments could not be conducted when the field was too wet. Another challenge was IDOT’s need to expand the project scope to include evaluation of curb and flared inlet protection products, which meant that inlets had to be constructed for that purpose.
Kalita says one important result of the project was that product performance varied considerably depending on the installation method. “We noted that a few of the products we tested were used for multiple purposes—ditch check, inlet protection—but the recommended installation methods were the same. We were able to demonstrate that it’s not just the product but how it is installed in the field that impacts the performance of the product.”
Vespa says that IDOT will benefit from the project findings and recommendations by being able to provide better erosion and sediment control in ditches and inlets. He adds that IDOT’s Storm Water Committee will review the results from the field trials to determine how best to implement the results and findings—and in turn may recommend changes to specifications and the design manual.
The project culminated in publication of four white papers:
- Evaluation of Curb and Gutter Inlet Protection Products for Sediment Retention
- Evaluation of Ditch Checks for Sediment Retention
- Evaluation of Ditch Inlet Protection Products for Sediment Retention
- Evaluation of Flared-End Inlet Protection Products for Sediment Retention