Potter Road over Conway Lake Bridge Replacement

Eaton, New Hampshire

Client: Town of Eaton, New Hampshire


  • Construction Administration
  • Construction Observation
  • Cultural Resources Coordination
  • Engineering Study
  • Final Design
  • Permitting
  • Preliminary Design

Project Summary

Hoyle, Tanner completed the design of the roadway alignment improvements and the replacement of an existing single lane steel stringer bridge with a corrugated steel deck on stone abutments. The bridge was replaced with a low-maintenance 40′ span prestressed deck beam structure supported by cast-in-place concrete abutments.  Challenges included making profile and alignment improvements while maintaining hydraulic capacity and limiting the proposed span length. There were several other challenges included in the project, one being the extremely poor soils encountered in the foundation locations.  The solution to providing foundations to support the new bridge while limiting anticipated settlement and consolidation of the soft soils was to create a permanent four-sided cofferdam with sheeting left in place, and placement of a concrete tremie seal.  Foundations were then constructed on the tremie seals.

A unique timber bridge and guardrail system was designed and installed to contribute to the rural nature of the area.  Innovative drains were incorporated into the brush curbs to facilitate drainage off of the bridge deck due the extreme flat profile grade over the bridge.  Construction was accomplished utilizing a full detour of traffic during the summer months as access on the gravel road was limited in the spring and fall months.

The project was successfully completed on budget and on schedule with funding through the NHDOT State Aid Bridge program.

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