One of the largest wildfires to scorch California in 2021 burned over 26,000 acres and prompted evacuations for at least 8,000 residents. The Lava Fire sparked from a lightning strike and burned for just over two months around the wooded slopes of Mt. Shasta. The extensive fire heavily damaged multiple structures, including Union Pacific Railroad’s Dry Canyon Bridge and nine miles of track near Weed, Calif.
The Dry Canyon bridge, which stands 150 feet tall and spans approximately 1,140 feet across a remote scenic valley, was closed on June 28, 2021 due to the damage.
While still combatting the fire in late June, Union Pacific Railroad Company (UPRR) engaged Modjeski and Masters (M&M) to assess damage and recommend repairs to the steel-girded bridge. M&M reviewed the outward physical damage to the girders on each span along with the cross-frame and lateral members. The team then reviewed the fitness and structural integrity of the fire-exposed steel by looking at the steel type and grade, and looking for heavy pitting, heavy dark grayscale, and any remnants of the original lead-based paint. These were signs that the metal had reached the limit of the transformation temperature.
After the assessment, the team determined heat straightening could be the primary repair option to salvage many of the deck plate girder spans. Utilizing Dan A. Dalton, Inc., a total of 10 70- and 80-foot spans were removed and heat straightened in addition to replacing all damaged bracing members and connections plates. There were nine 40-foot-girders that were replaced with stock spans owned by UPRR. Additionally, the team evaluated and resolved unseated tower anchor bolt nuts; salvaged 80-foot girder sole plates and replaced anchor bolts; fabricated new 40-foot girder sole plates with a modified bolt pattern; replace damaged tower 10-11 longitudinal diagonal bracing in kind, and installed a new timber ballast deck. The construction team included ZA Construction and Arc Rite Welding and Fabrication LLC.
The rehabilitation work was completed quickly and restored train traffic ahead of schedule.
The project team witnessed the first train over the bridge during a soft opening on July 31, 2021. Freight traffic resumed Aug. 1, 2021, one month earlier than expected.
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