Town of Gilmanton

Crystal Lake Road Bridge

Gilmanton, NH

Project Summary

The Town of Gilmanton retained Hoyle Tanner to prepare an Engineering Study, complete environmental permitting, prepare final contract documents, and administer construction for the replacement of Crystal Lake Road Bridge over Nelson Brook. The purpose and need for the project was to remedy the deteriorated condition of the bridge and substandard railings to improve roadside safety and extend the service life of the bridge in a cost-effective manner, while minimizing environmental impacts and delays to the traveling public and other users. Other goals were to maintain or increase the existing navigational clearance for recreational boats, meet NHDOT geometric and load carrying capacity requirements, and minimize impacts to abutting properties and utilities. Through several meetings with town officials and local residents, it was concluded that complete closure of the bridge during construction was feasible for this project. Construction time was minimized to a maximum of 75-day closure through the use of accelerated bridge construction techniques. The project included the replacement of the existing 10’ concrete slab bridge with a 38’ design span prestressed concrete deck beam superstructure supported on precast concrete caps and micropiles.  

This project was funded through the NHDOT Municipally-Managed State Bridge Aid Program. 


  • Preliminary Design
  • Public Outreach
  • Final Design
  • Bid Process Administration
  • Construction Administration
  • Construction Observation 

Final completion was May 2022

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