Marion Dunn Pond drains a 260-acre, primarily residential watershed. This pond has been the site of numerous studies to determine pollutant removal rates from detention basins — it is the pond on which the source loading and management model (SLAMM) was calibrated. Because of its effectiveness as a settling basin, the pond has filled up with sediment, thus, reducing its effectiveness at protecting Lake Wingra and the downstream watershed. In addition, Secret Pond and its influent channel have experienced high rates of sediment loss and bank failure, leading to sediment transport into Lake Wingra.

The goal of this project was to restore Marion Dunn Pond’s pollutant removal efficiency and reduce influent channel velocities. Improvements included creation of a forebay to concentrate sediments for easy removal, addition of an energy dissipater upstream of the Secret Pond influent channel, design of two new outlet structures to spread out the discharge before it enters Lake Wingra, and, in association with UW-Madison Arboretum staff, development of a planting plan. We also performed construction observation of these improvements.

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