I-91 Bridge Replacements – Bridges 8N&S and 9N&S

Brattleboro, Vermont

Client: Vermont Agency of Transportation


  • Construction Management
  • Construction Observation
  • Design/Build Services
  • Quality Assurance/Control Services
  • Quality Control/Inspection Testing
  • sUAS Imagery and Video Inspection
  • Terrain Analysis

Project Summary

As part of a design-build team with PCL Civil Constructors and FIGG Engineering Group, Hoyle, Tanner provided Quality Assurance Management (QAM) services for this $59.5 million project for the Vermont Agency of Transportation. The project included the replacement of I-91 Bridges 9N&S with a 3 span post-tensioned, segmental concrete bridge with a 510′ center span over the West River. Pier footings for this structure are supported on sixteen 5′-6″ diameter drilled shafts. Bridges 8N&S were constructed utilizing a NEXT Beam superstructure on concrete abutments with steel H-Piles. Hoyle, Tanner was responsible for Construction Quality Assurance (QA) services including inspection and testing, development of the Quality Assurance Plan, monitoring of Construction Quality Control, and preparation of QA documentation for the project.

Using a Small Unmanned Aerial System (sUAS), a test was run to determine how to safely and efficiently perform future inspection services for this bridge. Because this structure is 104’ wide, 1,000’ long, and approximately 30’ deep at each pier, a traditional Snooper inspection will likely be costly and time consuming. Hoyle, Tanner also completed a surrounding terrain survey to check for possible construction debris. It was noted that typical wind currents did create a challenging updraft directly under the bridge; however, it was found that the sUAS inspection can be completed, and provide comprehensive video and still digital picture capture of the structure potentially helping bridge inspection teams to focus their assessment at specific identified locations.

The project began construction in September 2013 and was completed in November 2017. Hoyle, Tanner brought long-span bridge construction inspection experience, project collaboration skills, and a high attention to detail and organization that were necessary for this important role on the design-build team.


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