I-93 Widening
Weigh Station Area Contracts G & H

Windham, New Hampshire

Client: New Hampshire Department of Transportation


  • Drainage Design & Pollutant Treatment
  • Highway Design
  • Project Sequencing
  • Right-of-Way Coordination
  • Stormwater Management
  • Traffic Control/Management

Project Summary

As part of the I-93 corridor reconstruction program Hoyle, Tanner was asked to provide the design of the 4-lane mainline traffic transitions to existing 2-lane conditions along both northbound and southbound alignments as part of the mainline reconstruction work. Understanding the numerous mainline design controls we prepared safe transition designs along challenging geometries while maintaining 2 lanes of traffic in each direction at all times, accommodated the weigh station traffic, collected and conveyed both “clean” and “dirty” stormwater within the site during highway reconstruction.

Hoyle Tanner designed nine stormwater Best Management Practices (BMP’s) that included: five extended detention wet ponds, one infiltration basin, one roadside treatment swale and two extended detention excavations. These stormwater BMPs not only provided pre- versus post peak flow detention, they were also designed and sized to provide stormwater treatment for total suspended solids (TSS), phosphates, and nitrogen removal.

The stormwater system was integrated into the roadway reconstruction to collect “dirty” water while passing “clean” water through. Total closed system “dirty” water collection need was calculated based on selected BMPs efficiency and iterative pollutant loading analysis until water quality was feasibly met.

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