The Tongass National Forest is the largest National Forest in the U.S., spanning almost all of Southeast Alaska from the southern top of Prince of Wales Island to the Malaspina Glacier 500 miles north.

DJ&A was tasked with investigating and evaluating the conditions of and performing load ratings for 390 existing remote road bridges within the Forest to meet Federal Highway Administration and National Bridge Inspection Standards (NBIS). In conjunction with these field measurement visits, DJ&A conducted 104 routine bridge inspections in compliance with NBIS.

In the first phase of the project, DJ&A worked directly with Forest Service personnel on database management to compile and organize existing electronic and hard-copy files, and locate any available information for the 390 bridges. Plans were found for fewer than 100 of the 390 bridges. DJ&A then located 10 different bridge suppliers spread over 5 states and worked with them to collect and assemble bridge plans, designs, and specifications. In addition, DJ&A collected field measurements from 35 rural bridges on publicly owned land to assemble load rating data. DJ&A ultimately found sufficient data to load rate 376 of the 390 bridges. All structural calculations utilized BRASS, MathCAD worksheets and USFS, TBAR software to provide load ratings for these bridges. Twenty-two of the load rated bridges required immediate load restriction.

The final phase of the project involved creating complete, permanent bridge files for all 390 bridges and making long term bridge planning and asset management recommendations to the Forest Service bridge engineer.

Key Services

  • Evaluated and interpreted existing bridge information
  • Performed field measurements, bridge inspections for 104 remote bridges, and load ratings calculations for 376 bridges
  • Compiled long term bridge planning and asset management recommendations for the Forest Service

Value Added

DJ&A is experienced in working in remote, harsh conditions. This project required travel to locations throughout the Tongass National Forest where access required travel by amphibious aircraft, boat, and truck and the company of Forest-certified sharpshooter for protection from heavy populations of Alaskan Brown Bear (Grizzly).