This project consisted of scraping and removing four feet of sediment that accumulated in the pond basin. The pond is fed by surface water runoff from Dale Ave and Dahlen St. At the end of Dale Ave (an unimproved street), a rain garden was constructed to pre-treat the runoff prior to discharge to the pond. Dahlen Street was improved with curb and gutter, and runoff is now piped through a drop structure to the pond where it is pre-treated in a settling area prior to discharge to the pond.
Kettle Pond is an 8-acre conservation park owned by the City of Madison. It was acquired in 1971 to preserve the glacial kettle, which is the central feature of the park. A remnant oak savannah surrounds the pond. The pond has a perched water table fed by surface water runoff. The majority of the surface water runoff comes from two nearby streets, Dale Ave and Dahlen St.
In the decades prior to construction, there had been a noticeable decline in water depth and duration/area of open water. Prior to 1990, there was an open water area that ranged between 1/2 and 1 acre. Since then it had declined to about 1/20 of an acre. A 1997 UW Landscape Architect class did an extensive study of the area, including soil borings that uncovered 3 to 4 feet of post-European sediment deposited over a 1-4 ft layer of peat. A clay layer below created the perched water table system, and a check of nearby well drilling records confirmed this conclusion.
Parks staff undertook an experiment to kill roughly 2/3 of the large tree adjacent to the pond using girdling with herbicide treatment. Trees were left to stand dead, providing wildlife habitat. The hope was that by reducing water uptake from nearby trees, the pond water level would rise. This did not happen despite some very wet conditions in 2000 and 2004.
This most recent restoration effort involved scraping and removing 3-4 feet of sediment from the pond basin and planting a diverse group of native emergent and submergent species. Large logs were also salvaged from the site and placed in the pond for wildlife habitat.
A rain garden was constructed at the Dale Ave end to facilitate infiltration of surface water runoff. At Dahlen Street runoff was piped through a drop structure and into a pretreatment wetland to capture sediment before it reaches the pond basin.