Curbing sediment
Rain pouring down over the road can create more than just dangerous driving conditions. Fine particulate that accumulates on roadways is washed into storm drains that connect to local waterways. These vehicle-borne particles—often called first flush toxins—contain bits of copper, zinc, cadmium, as well as grease and metals. These particles can accumulate and cause catch basin backups that result in flooding, but they can also make their way into the food web and our drinking water.
Halina Steiner, assistant professor of landscape architecture at the Knowlton School, has been researching how concrete curbs, aprons and gutters may be designed to capture the sediment that collects on the road so it can be extracted before entering the storm basin.
“In the initial stage of our design we looked at various alterations to walkway surfaces,” Steiner said. “We focused on tactile pavement as a point of departure and how we could put cuts in the curb and apron to collect the sediment.”
The project team also includes Ryan Winston, an assistant professor in the Department of Civil, Environmental and Geodetic Engineering; Alec Grimm, a graduate student in the Department of Food, Agricultural and Biological Engineering; and Avee Oabel, an undergraduate landscape architecture student.
Twenty different curb and apron designs were tested on 4-by-8-foot sheets of milled foam that were sealed with paint. Designs experimented with the density and configurations of cuts into the apron including parallel, perpendicular, diagonal and cross-hatch depressions.
“Among cuts into the face of the curb, which included triangular, rectangular and circular shapes, we found the square performed best when paired with various patterns on the apron,” said Steiner.
The iterative design process also tested the effectiveness of combining different apron and curb patterns, pairing different spacing configurations with apron designs that were offset or fed directly into the curb.
Each full-scale curb mock-up was tested by simulating a one-inch storm rain event. Native soil and sand were suspended with a mixer, then pumped across the model. Water sensors located at the inlet and outlet of the curb mock-up checked the volume and turbidity of the water. Water samples were collected every two minutes from a collection tub and later analyzed by Winston to determine the volume of collected sediment.
These proof-of-concept tests indicated that the team’s design could hold onto 80% of stormwater sediment, which they envision being collected by street sweepers fitted with vacuum attachments.
“We’ve proven conceptually that the designs work. Now we need more scientific data,” Steiner said.
Now with a provisional patent for the project, Steiner and her team are looking to field-test a prototype on campus. This will allow the researchers to see how the designs perform aesthetically, as well as how they work in weather conditions like snow, and interactions with snowplows and cars.
“The Curbing Sediment project extends my interest in how non-site specific solutions can be applied at a larger scale,” said Steiner. “Through my work, I hope to increase the awareness and understanding of hydrology, and to make people more water literate in general.”
contributed by the Knowlton School of Architecture
