Mallard Lake Channel Restoration and Stabilization

Planning Project

Mallard Lake Channel Restoration and Stabilization

Summary of work

From 2018 to 2019, the Forest Preserve District of DuPage County worked on a river restoration and stabilization project along a 0.5-mile long stretch of the West Branch DuPage River at Mallard Lake Forest Preserve in Hanover Park. The primary purpose of the project was to stabilize banks of the river near the Mallard Lake North Landfill. Where practical, the project also naturalized and enhanced the function of the river.

The project site has a unique history due to the landfill. Aerial photographs (Figure 1) reveal that the river's natural alignment passes through the center of what is today the landfill. As early as 1938, the river appears to have been straightened upstream of the landfill site for agricultural purposes, but is generally in its historic alignment. At some point between 1962 and 1966, the river was diverted around the landfill site to allow gravel mining operations and the eventual filling of the mine with trash for use as a landfill. The project reach is characterized by steep banks and very little to no floodplain due to the steep cuts and fills made around the engineered channel. This is in stark contrast to the reach immediately downstream of the landfill, where the river remains in its natural alignment and provides a broad, gently sloping floodplain.
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Figure 1: Illustration of historic progression of the West Branch DuPage River.

The purpose of the project was to stabilize the river banks adjacent to the landfill through two primary means: realigning the channel to provide physical separation between the channel and the landfill, and, where relocation was impractical, lining the banks with a graded aggregate filter.

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Figure 2: Proposed Plan

 

Status

Major construction has been completed. The site will now undergo 5 years of vegetative maintenance and monitoring to ensure the establishment of a vibrant native wetland habitat. 

 

Funding

The $2,500,000 project is fully funded utilizing landfill reserve funds.

 

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Photos of the stream after it's been stabilized.

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