Rockingham Bridge Replacement

Rockingham Bridge Replacement

GeoDesign is the geotechnical consultant for design and construction of the I-91 Bridge 24 N/S over Green Mountain Railroad and Williams River in Rockingham, Vermont. The project includes replacement of two bridges along I-91 located immediately north of Exit 6 at the intersection of Vermont Route 103 and I-91 in Rockingham, VT. The bridges carry I-91 northbound (Bridge 24N) and southbound (Bridge 24S) over the Williams River and the Green Mountain Railroad.

The proposed replacement bridges are four-span and approximately 850 feet long. The proposed bridge elevation decreases by approximately 40 feet from the south to the north. The clearances over the Williams River and GMR track are between 100 and 150 feet. The proposed replacement bridges are wider than the existing bridges and, therefore, corresponding widening of the bridge approaches is anticipated.

VTrans has designated the bridge as a critical bridge. A critical bridge must remain open to all traffic after the design earthquake and must be usable by emergency vehicles and for security/defense purposes immediately after a large earthquake.

Key geotechnical aspects of the project include:

  • Pile design for abutment and pier substructures including pile group analysis using GROUP software by Ensoft;
  • Coordinating geophysical seismic refraction and GPR measurements to obtain geological data in river channel for scour analysis;
  • Evaluating static and seismic slope stability of embankments; and,
  • Performing a geotechnical seismic hazard evaluation including a site-specific ground motion study to develop a design response spectrum and liquefaction evaluation.

Project Details

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