Spring Harbor Outfall Repair
October 2021 Update:
The repairs to the Spring Harbor outfall, including replacement of the failed retaining wall and the discharge pipe from the spring, are scheduled to begin in mid-November 2021. The contracting process is in progress, but upon completion, a link to the project plans and specifications will be provided on this webpage.
The City of Madison's Spring Harbor Watershed Study is nearing completion. That project's third Public Information Meeting was held June 30, 2021, virtually. View the presentation recording and supporting documents on the Spring Harbor Watershed Study page. Spring Harbor Outfall Repair and Dredge FAQ.
The August 20, 2018 rain event caused the concrete storm sewer outfall structure at Spring Harbor to fail. The heavy rain and high volume of stormwater runoff caused scour beneath the existing retaining wall. The scour was significant enough to undercut and destabilize a portion of the wall, which lead to its rotation and ultimate failure. As an emergency repair, the City placed temporary sheet piling and riprap to secure the embankment. This project will construct a permanent repair for the failed wall and replace a failed storm sewer pipe beneath Lake Mendota Drive. Each item is discussed below.
The proposed project will repair the failed section of retaining wall by replacing it with a concrete-faced sheet piling wall. The concrete facing will allow the new wall to blend with the existing section of box culvert, while creating a wall that is not susceptible to being undermined by scour. However, instead of extending the concrete wall 3-4 feet above the adjacent ground surface, the new section of wall will be topped with a tubular steel railing, which will provide fall protection, but will create less of a visual barrier. A series of limestone steps, designed to sit above the normal high water elevation, will be installed at the northern terminus of the new wall section. These steps, which are in keeping with past amenities installed at Spring Harbor, will provide protection to the harbor from overland flow coming from Lake Mendota Dr.
Lastly, this project will replace and upsize the former pipe that connected the spring area, south of Lake Mendota Drive, to Lake Mendota and Spring Harbor. This pipe failed during the Aug 2018 event.
The City of Madison has contracted with Speedway Sand and Gravel to perform the outfall repair work described above. Construction is scheduled to begin in mid-November 2021, and primary construction should conclude by December 31, 2021. Some final restoration of Lake Mendota Dr may be performed in Spring 2022.
The City of Madison hosted several public information meetings and meetings with residents to discuss this and other projects. View the latest public presentation of this project, provided to the Madison Board of Parks Commissioners in March 2021. Residents with questions about this or other Spring Harbor projects are encouraged to reach out to City project manager Lauren Striegl at email@example.com.