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Map historic bridges before it’s too late

April 11, 2014

When old bridges collapse, more than just history can be lost – people can be harmed if they are in the vicinity. Thankfully, no one was in the area when part of the historic Eichelberger Crossing Bridge fell into the North Bosque River in McLennan County, Texas, at the end of March. Even though the bridge had been abandoned for years and had experienced numerous fires over the years, it was still being used by local residents, according to local Texas news source WacoTrib.com. Its structural integrity could have been secured by mapping out the bridge's existing architecture with 3D laser scanning. Having an accurate view of the bridge's structure could have identified if parts of the bridge were decaying, and possibly providing insight into the integrity of the bridge's support beam or if flying debris caused the collapse.

According to the news source, the county must now look to see how it can remove the fallen portion of the bridge from the water, an operation that could cost the county a pretty penny.

Bridge collapse causes issues for local residents, county officials
The bridge had been standing since 1925 and had been closed to vehicles since 1981. While a new bridge was built as its replacement in 1987, the news source reported the old 275-foot bridge was a favorite spot for local fisherman in the springtime during the upstream run of white bass during mating season. With the weather heating up, fisherman are looking to spend more time on the bridge. However, the news source reported the bridge will remain closed to residents until the remaining part of the bridge is deemed safe.

Ray Meadows, former Precinct 4 county commissioner, told the news source he wasn't surprised the Eichelberger Crossing Bridge ended up collapsing, but that it showcases just how important it is to examine old bridges in the state for structural integrity.

"That old metal had got to be rotten by now, but there are a lot of deficient bridges all over this state," Meadows said. "They were built in the '20s and '30s for Model A's or lightweight tractors. But sometimes it takes something like this – or worse, a death – to get people to start looking at how dangerous some of these bridges have become." 

A part of history
County records indicate the bridge was built by the Austin Bridge Company 89 years ago, and Steve Hendrick, an engineer for the county, told WacoTrib.com it was kept intact as part of an agreement between the federal government and the county for the receipt of a federal grant to construct the new bridge. According to the Texas Department of Transportation, Austin Bridge Company, which was known as Austin Brothers Bridge Company until the '30s, was the biggest bridge fabricator in Texas during the early part of the century. It was popular for creating bridges quickly at affordable costs, the transportation department noted. The Eichelberger Crossing Bridge was part of a movement in Texas during the '20s to improve the quality of the state's infrastructure.

3D laser scanning of historic sites can preserve them in 2D and 3D models for the ages. Historic site documentation can accurately identify any weak areas in existing structures, giving insight to site owners and managers about its working condition. From building information models (BIMs) to Historic American Buildings Survey (HABS) and Historic American Engineering Record (HAER) drawings, using 3D laser scanning to create as-is and as-built models of historic sites can help to inform site managers about the existing conditions of historic sites.