Spring Harbor is a man-made harbor, located on the west side of the City of Madison along the shores of Lake Mendota. This harbor features an existing municipal public boat launch and fishing pier at City of Madison’s Spring Harbor Park.  Over the years, increased sedimentation and public and private access points have minimized opportunities for recreational boating and fishing.

One of the impacts to the recreational use of this boat launch is that Spring Harbor also serves as a major outfall for a 19.5’ x 6’ storm sewer box culvert that drains 2,400 acre urban area of the Spring Harbor watershed. The outfall is located just east of the boat launch and directly discharges to Spring Harbor (see Figure 1). 
 

The watershed served by this outfall was primarily developed prior to modern stormwater management practices such as retention and detention basins and as a result, the urban runoff discharging to the harbor carriers a reasonably large amount of sediment into the harbor at the boat launch. This is compounded by Madison’s primary use of sand versus salt for winter icing operations which contribute to the accumulated sediment deposited at this outfall into the harbor.  As a result, this harbor has a higher rate of siltation than would be otherwise experienced requiring routine dredging to maintain navigability of the existing channel for recreational boating and improved fishing habitat. As the channel and harbor silt in, users of the public boat launch and harbor residents with boat docks have trouble launching boats and navigating through Spring Harbor to access Lake Mendota and the fishing conditions decrease with continued siltation.  

A hydrographic survey was conducted in May 2020 showing the average depth of the harbor was 2.5 feet. The City is  planning on dredging the entire length of Spring Harbor a minimum width of 25 feet wide on either side of the channel centerline (50ft width total), and creating a minimum channel depth of 8 feet to improve recreational boating opportunities. 

The benefit of this dredge project is to extend the usefulness of the channel another 10 years or longer. The previous channel dredge did not fully excavate the materials to the lake proper and only provided for increased navigability near the launch itself, however the proposed project is intended to excavate a channel to a depth that would allow a wider range of boat types from the launch and from the private piers to access the channel and lake without concerns of running into the accumulated sediment. The dredging will undoubtedly allow for increased recreational use of the harbor, better water quality and aquatic habitat and also more access for Lake Mendota in general for fishing and recreation. If additional funding is available the project may allow for a wider width in the dredging.

Spring 2021-Summer 2021
Design Development: project planning, public outreach and involvement, permitting

Summer 2021- Fall 2021
Final Design: additional public outreach, finalizing project plans, special provisions, details, requesting approval from involved City Departments, Common Council and Board of Public Works. Advertising the project publicly to solicit competitive bids. Award the project.

Fall 2021-Winter 2021
Construction: the contractor will dredge the harbor according to plans and specifications and haul the material to the designated de-watering site in water tight trucks.

Winter 2021 - Spring 2022
De-watering and Disposal of Materials: the contractor will survey the de-watered dredge material for quantity and haul the material to the Dane County Landfill.