Lower East Ravine Stabilization

Location:  Cottage Grove, Minnesota
Client:  South Washington Watershed District

Background

Portions of the Lower East Ravine, south of Highway 61 in Cottage Grove, MN, was severely eroding. Because of upstream development, erosion left unattended would only become worse. The South Washington Watershed District (SWWD) retained HEI to develop alternative concepts and design to combat erosion in the ravine and restore the channel.

The Project

This project began with two separate feasibility studies, completed in 2013 and 2014. The first study focused on 7,000 feet of the ravine in Cottage Grove Ravine Regional Park. HEI completed a topographic and environmental survey and a shear stress analysis for the entire reach using a combination of XP-SWMM and HEC-RAS. From this analysis, a range of stabilization options were identified. HEI prepared artistic renderings of alternatives to help stakeholders visualize the options.

The second feasibility study focused on the lower part of East Ravine, located entirely on 3M property. A shear stress analysis was also used on this reach in addition to a geomorphic assessment.  

Working with 3M, stabilization options were identified that prevented erosion and also met their needs on-site.

HEI completed concept designs and presented the SWWD with a variety of sustainable solutions for restoration.

HEI completed final design, final plan package, bidding, and construction management and observation services. HEI helped the SWWD navigate the permitting process, and the project was constructed in 2016.

Client Benefits

  • HEI involved stakeholders throughout the project and coordinated with 3M, the primary landowner, to develop a successful solution.
  • Concept designs and renderings were created to help the District and community visualize the restoration enhancements.
  • Provided substantial on-site construction observation to ensure project success.
  • Provided final design and plan package.