New Hampshire Department of Transportation

NH Route 26 Reconstruction

Colebrook, NH

Project Summary

NHDOT engaged Hoyle Tanner for assistance advancing the P2496 project through the final design process for bidding and construction. The existing roadway had substandard geometry and shoulder width, poor pavement and drainage conditions, substandard roadside barriers, and steep side-slopes that all necessitated corrective action. The design solution addressed all the deficiencies and substandard conditions by proposing roadway widening, realignment and intersection improvements, reconstruction of the pavement, new open and closed drainage systems and culverts. Additionally, Hoyle Tanner coordinated improvements with the replacement of three bridges along the corridor included within the project limits. In total 3-miles of NH Route 26 were improved in the Towns of Colebrook and Dixville that included the intersection with Diamond Pond Road to realign the approach and add turning lanes. The new road structure design incorporated the lack of readily available rock materials suitable for road construction with project-specific materials specifications, thicknesses and longevity considerations. Many project specific design details were required for permitting and to provide the sustainable solution addressing the high-water table, frost susceptibility, stability, erosion control, and traffic management needs attributed to the challenging soil characteristics. The design provided miles of open and closed drainage, underdrain, culverts, outfall protection to maintain water quality standards adjacent to the Mohawk River more safely accessed and readily enjoyed for recreational purposes


  • Roadway Design 
  • Intersection Design 
  • Right-of-Way Coordination 
  • Traffic Control/Management 
  • Utilities Relocation Coordination 
  • NEPA & Permitting Support 
  • Culvert Design 
  • Drainage Systems Design 
  • Cost Estimation 

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