A key activity to the implementation of the Historic Bridge Program is the statewide survey of historic bridges. The survey will examine the bridge population built in or before 1963 and will include bridges made of timber, metal, and concrete. The survey will create a database of bridges in Indiana on public roads that are either listed in the National Register of Historic Places (NRHP) or are eligible for listing in the NRHP.

There are two distinct bridge populations within the study time period. The bridges built in or before 1942 (pre-World War II) is one distinct population and the other distinct population includes bridges built between 1943 and 1963. Generally, most interest and concern is with historic bridges built in the pre-World War II time period. Also of note, a significant amount of research, primarily by Dr. James Cooper, has been completed on the population of bridges built in the pre-World War II era. Bridges in the 1943 to 1963 era have not yet generated as much interest statewide. While it is important to determine what bridges in the 1943-1963 time frame are eligible for the NRHP, that population is not perceived to be as endangered as the pre-1942 population. Therefore, the survey effort will first focus on determining bridge eligibility for the pre-World War II bridges. Later, the bridges built between 1943 and 1963 will be analyzed for NRHP eligibility. The following chart shows the total number of bridges in Indiana, owned by either the State or by local governments, divided into three eras related to the survey process. The chart also shows how many bridges are owned by the State of Indiana and how many are owned by local public agencies within each era.

The survey process is being separated into three activities:

Screening Phase

The Indiana Local Technical Assistance Program (LTAP) is completing the screening phase of the survey. The purpose of the screening phase is to narrow down the list of extant bridges built in or before 1942 (about 3,535 bridges) to a more manageable number (approximately 1,600 bridges) with potential historical significance. To determine which bridges are most likely to have historic significance, LTAP is reviewing the National Bridge Inventory database, publications by Dr. James Cooper, reviewing Indiana bridges listed in the NRHP, and asking County Commissioners, County Historians, and Indiana Department of Transportation District Directors which bridges they believe have historic significance. The bridges with potential historical significance will be put into a database and analyzed for their eligibility for the NRHP in Phase I Eligibility Determinations.

Phase I Eligibility

For the Phase I Eligibility determinations, the Indiana Department of Transportation has agreed to obtain the services of a consultant with the professional qualifications to make NRHP eligibility recommendations. Once the consultant is selected, the consultant will be responsible for involving the public in the bridge survey process and eligibility process. The consultant will analyze the database created in the screening phase and recommend to the Federal Highway Administration and the State Historic Preservation Officer a list of bridges that should be considered eligible for the NRHP and a list of bridges that should not be considered eligible for the NRHP.

The public involvement process for Phase I Eligibility will be crucial to ensure all bridges with potential historic significance are analyzed for NRHP eligibility. There are approximately 3,535 bridges that were built in or before 1942. Of those bridges, the database created in the screening phase will likely contain approximately 1,600 bridges. That means approximately 1,935 bridges will not be carried forward to be analyzed for NRHP eligibility. It is possible some of the bridges not included in the database are indeed eligible for the NRHP. As part of the public involvement process, we will be asking the public to let us know if they feel that a bridge omitted from the database should be analyzed for NRHP eligibility. The figure below represents the population of bridges built in or before 1942 and shows the four potential "bins" that any bridge within the population might lie as a result of the screening phase and Phase I Eligibility determinations.

Phase II Eligibility

The Phase II Eligibility determinations will begin after the Phase I Eligibility determinations have been completed. The Indiana Department of Transportation's consultant will be responsible for involving the public in the bridge survey process and eligibility process for bridges built between 1943 and 1963, inclusive. The consultant will analyze this population of bridges and recommend to the Federal Highway Administration and the State Historic Preservation Officer a list of bridges that should be considered eligible for the NRHP and a list of bridges that should not be considered eligible for the NRHP.