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First bioretention installed in Topeka |
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Treats runoff from parking lot |
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Used as pilot to determine best vegetation |
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The Hillcrest Bioretention Cell was the first bioretention cell installed in Topeka. A bioretention cell is a shallow basin planted with native grasses, trees, and shrubs. Bioretention cells collect stormwater and hold it for a short period of time, allowing some of the water to be naturally absorbed by the soil and plants. The pollutants in the water are removed through various plant and soil processes and the remaining runoff travels to the city's stormwater system flowing to the Kansas River.
The Hillcrest cell was constructed by removing pavement from the center of a parking lot at the Hillcrest Community Center. Once the pavement was removed a slotted drainpipe was placed on washed gravel. The clean gravel and drainpipe where then wrapped with filter fabric and the entire cell was filled with a mixture that included soil and sand that would allow the rainwater to soak into the ground. The cell was then planted with sod, trees, and shrubs. The entire bioretention area was surrounded with a curb that was slotted on one side to allow for rain runoff to flow into the bioretention area. An Eagle Scout constructed a bridge across the bioretention cell to protect it from foot traffic.
The Hillcrest Bioretention Cell has been used to determine what plants work the best in a bioretention cell. Several of the original trees and shrubs have been replaced by switch grass down the middle of the cell. Switch grass greatly increases the water absorption and according to research by Kansas State University it also filters out pollutants commonly found in urban stormwater.
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