Stabilization and harmonious blending of highway interchange slopes

May 14, 2020

The Interstate 90 Bridge over the Mississippi River between La Crosse, WI and La Crescent, MN is a heavily used commuter route. It is part of the longest Interstate Highway (I-90) from coast-to-coast, providing important commercial and defense infrastructure for the entire nation.  

Bridge Design Project Objectives

The goal of a three-year, $187.5 million project was to provide a new, structurally sound I-90 river crossing bridge that achieved current structural and geometric standards on this important regional river crossing, and provided a safer, higher-capacity reconstructed interchange. 

A design requirement was that the reconstructed bridge and interchange fit naturally into the beautiful surroundings created by the bluff and river environment.

Key factors in the river bridge design plan:

  • 100-year design life
  • Length:  2,593 feet |Width: 45-66 feet
  • Two 12-foot lanes in each direction
  • 12-foot outside shoulders, 6-foot inside shoulders

Slope Protection Design Solution

Presto’s GEOWEB® 3D system was chosen to address both structural and aesthetic design requirements for 11 different slope application areas. The 3D system confines and stabilizes topsoil and aggregate on steep slopes. Confined infill is stable on steep slopes ≥ 1H:1V and is minimally affected by surface runoff.

Slope Stabilization Areas:

  • Vegetated Slopes: 106,000 sf of 6 in deep GEOWEB sections filled with topsoil and an erosion control blanket cover. Slopes varied between 2.5H:1V and 3.5H:1V, up to 48 feet vertically, around the bridge abutments.
  • Non-Vegetated Slopes: 47,000 sf of tan 4 in deep GEOWEB sections chosen to match the local aggregate were placed over a non-woven geotextile and filled with aggregate. Slopes varied between 2H:1V and 1.5H:1V, up to 45 feet vertically, under bridges. Vegetation was not an option in these locations due to the lack of exposure to sunlight and moisture.

In both applications, ATRA® Anchors secured the GEOWEB sections on the slopes. Presto Geosystems’ engineering team provided calculations and anchoring recommendations for all areas. This three-year long construction project was completed in the fall of 2016.

Project information provided by Mark Anderson, P.E., MnDOT District 6-Winona, MN.

Editor's Note: Scranton Gillette Communications and the SGC Infrastructure Group are not liable for the accuracy, efficacy and validity of the claims made in this piece. The views expressed in this content do not reflect the position of the Roads & Bridges' Editorial Team.

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