Bridging the Preservation Gap: Documenting Our Historic Infrastructure, Part II
In part one of this series, we discussed the critical need for preservation of our historical bridges and the records that document them. Today, we look at who keeps these records and how the documentation is changing.

In a world where many of our bridges are fifty, a hundred, even 150 years old the line between current documentation and historical documentation blurs.  Scott Cline, City Archivist for the Seattle Municipal Archives, underscores the importance of this fact, noting, “The design and construction records for roads, tunnels, bridges, etc. are powerful tools in the inspection and maintenance of those facilities. They document materials and methods that should inform maintenance and repair work to keep these structures safe, secure, and reliable.”  This is particularly significant, Cline says, because, “Infrastructure failure can be disastrous and deadly.”

The National Bridge Inspection Standards (NBIS) review process sets requirements for state Departments of Transportation regarding inspection of highway bridges and mandates regular submission of survey results; however, it fails to mention original design documents. Thus, although state agencies including Transportation Departments (especially their Bridge Preservation and Cultural Affairs Offices) and Historic Preservation Offices often hold the most valuable records, original documents regarding the design, construction, and maintenance of bridges may be spread across various government agencies and private collections from public libraries to the National Archives.

In the case of the collapse of the I-35W bridge, investigators from the National Transportation Safety Board (NTSB) relied on the original engineering drawings and other documents from the firm that designed the bridge in the early 1960s in addition to records of the Minnesota Department of Transportation (MnDOT), including contracts, agreements, and decades of inspection reports. The research uncovered a flaw in the original design that the NTSB report concluded was the primary cause of the collapse.

“Historical documentation is essential in historic bridge preservation for directing and/or justifying installation of features identical to or reflective of original fabric,” notes Craig Holstine, Historian with the Washington State Department of Transportation’s Cultural Affairs Office. “Without accurate documentation, bridge preservation is left to the imaginations of engineers and historians.” 

The Historic American Engineering Record (HAER), established in 1969 by the National Park Service, the American Society of Civil Engineers, and the Library of Congress to document historic engineering and industrial sites and structures, also plays an invaluable role. HAER reports draw on primary and secondary sources as well as direct observation to document historic structures. This documentation not only preserves accurate information about a historic bridge or other property that faces demolition, but also facilitates repair or reconstruction. Additionally, it provides a trusted source used by engineers, architects, scholars, researchers, preservationists, and others. 

Technology continues to add new challenges and opportunities for archivists. Many of our earliest bridges have no engineering drawings. However, today the latest laser scanning devices and data processing techniques are being applied to some of these historical bridges in order to assemble complete digital representations of them and to create scaled, three-dimensional replicas. The images, scan data, and precise measurements become essential parts of the archival record. 

Scott Cline points to the central role of archivists in this regard:  “One of the vital functions of government is to maintain safe, secure, and reliable infrastructure—roads, bridges, sidewalks, and in the case of public utilities dams, pipelines, transformers, etc. Easy access to the complex body of records that document infrastructure is required for the maintenance of those facilities. These records are active as long as the structure exists and it is important for archivists to work with public works officials to ensure those records are properly preserved.”