Division of Environmental Analysis (DEA) LINKS
Last Updated: Wednesday, December 14, 2016 3:08 PM
Historic Bridges and Tunnels
California's Historic Bridges and Tunnels
California has a wealth of iconic landmarks that let residents and visitors alike know they are in the Golden State. Many of these landmarks are the state's historic bridges and tunnels that range from the spectacular Bay Area and elegant Los Angeles River bridges,to the simple and aesthetic bridges of the Central and North Coast, and the rustic bridges in rural areas throughout the state.
The Caltrans Division of Environmental Analysis and cultural resources specialists in the 12 district offices work closely with Caltrans engineers and maintenance staff, as well as local governments and historic preservation groups, to preserve and protect the historic bridges and tunnels of the Golden State.
This webpage is a cooperative effort among the Division of Environmental Analysis, the Caltrans Transportation Library and History Center, and the Division of Engineering Services to provide information to Caltrans staff, other governmental entities, consultants, engineers, cultural resources specialists, and anyone who is interested in these resources. It serves as a portal to information about these resources, including historic contexts for historic bridge types, information on individual historic bridges, and technical guidance.
- Historic Bridge Inventory
- Transportation Library and History Center Bridge and Tunnel Information
- Historic Bridge Contexts and Surveys
- Standard Environmental Reference (SER), Volume 2 - Cultural Resources
- Caltrans Contacts
- Technical Guidance
- Federal Highway Administration - Environmental Review Toolkit and Bridge Preservation
- Other Information on Caltrans Bridges
If you have questions or comments about historic bridges or the historic bridge inventory, please contact in the Caltrans Division of Environmental Analysis at (916) 653-0802, or the Cultural Studies Office of Caltrans Division of Environmental Analysis.
Historic Bridge Inventory
The original statewide historic bridge inventory was completed in 1986. It was most recently updated in 2010 for bridges built between 1960 and 1964, and the National Register of Historic Places (National Register) status of some of the bridges has changed. The update evaluated most of the state highway and local roadway bridges constructed prior to 1965. Bridges constructed in 1965 and later are expected to be addressed under the Advisory Council on Historic Preservation's Program Comment for Streamlining Section 106 Review for Actions Affecting Post-1945 Concrete and Steel Bridges issued November 16, 2012.
Each bridge received a National Register status designation and are placed in one of the five numeric categories as follows:
- Listed in the National Register.
- Eligible for National Register listing.
- May be eligible for National Register listing.
- Unevaluated. Generally, Category 4 bridges constructed before 1965 are associated with properties that have not yet been evaluated, such as railroads, canals, or potentially eligible historic roads.)
- Ineligible for National Register listing. Historic Bridge Inventory main page.
In 1984-1986, Caltrans conducted a statewide inventory of highway bridges with some potential for historic significance. Many old bridges need to be rehabilitated or replaced every year, and virtually all of these projects were federally-funded and subject to federal historic preservation laws. In the 1970s, the Federal Highway Administration (FHWA) recognized that it was inefficient to continue to evaluate each historic bridge on a case-by-case basis. It encouraged the various state highway agencies to survey bridges on a comprehensive basis.
Caltrans' master inventory of bridges included 23,000 structures. By eliminating those that were built within the past forty years, and those that were not highway bridges per se, but culverts, tunnels, railroad bridges etc., the number of bridges needing to be surveyed was substantially reduced. One thousand bridges were identified as having some potential for historic significance; these made up the survey population. A four-step survey process consisted of conducting background research on bridge building in California, gathering data on each bridge in the survey, developing a quantitative evaluation system, and evaluating each bridge according to the system.
The quantitative evaluative system was derived in large part from previous surveys in other states but adapted to meet California circumstances. Developing the system involved identifying attributes that might define significance, then assigning a weighted value to each attribute. Age, for example, is commonly taken as an indicator of significance; rarity is another. A very large bridge is usually valued over a small bridge because it is a more dramatic achievement in engineering science. Bridges are also valued when they are beautiful, designed by a famous engineer, representative of innovative technologies, important to local transportation history or other local historical trends, or when they possess unusual ornamental or structural features.
Special conditions in California were also considered, such as a high incidence of historic concrete bridges. Separate systems were developed for the major concrete bridge types (arches and girders), in addition to a system for metal truss bridges.
The final step in the inventory and evaluation process was to apply the evaluation system to the survey population. To ensure consistency, Caltrans developed guidelines for applying the criteria, which were as specific as possible, particularly with respect to the more subjective categories. When the guidelines were applied to all the bridges in the survey population, a computer database program generated lists of bridges ranked numerically.
The distribution of bridges on this list was predictably bell-shaped, with a small number of excellent bridges scoring very high, a number of bridges scoring very low, and a lump of bridges in the middle. Very low-scoring bridges were eliminated from further consideration, while very high-scoring bridges were placed into the National Register-eligible category. The middle group was reviewed by a team of evaluators, including representatives from Caltrans, FHWA, and the California Office of Historic Preservation. The review relied on the point system as well as other considerations that may not have been reflected in the numerical evaluation system.
Transportation Library and History Center Historic Bridge and Tunnel InformationThe Transportation Library and History Center maintains a searchable Historic Bridges database that contains data and photographs for historic bridges and tunnels listed or determined eligible for listing in the National Register. Data include structure number, location, summary description, structure type, distinctive features, and other data to assist with understanding significance. Additional information is available in the historic bridge files of the Transportation Library and History Center.
Transportation Library and History Center
1120 N Street, Room 1430
Sacramento, CA 95814
Hours: 9:00-4:00, Monday - Friday
Historic Bridge Contexts and Surveys
As a result of the original 1980s survey and the subsequent updates, numerous historic contexts were developed and can be accessed from the links below.
- Caltrans Statewide Historic Bridge Inventory: 2015 Update (Caltrans 2015) (72,762 KB, caution large file)
- Caltrans Statewide Historic Bridge Inventory: 2010 Update (Mead & Hunt, Inc. 2010)
- Caltrans Statewide Historic Bridge Inventory Update, Tunnels (Myra L. Frank & Associates, Inc. 2006)
- Caltrans Statewide Historic Bridge Inventory Update, Bridges that were not individually surveyed and evaluated (Caltrans 2005)
- Appendix A - Download the PDF file (1,417 kb)
- Appendix B - Download the PDF file (1,425 kb)
- Appendix C - Download the PDF file (3,539 kb)
- Caltrans Statewide Historic Bridge Inventory Update: Timber Truss, Concrete Truss, and Suspension Bridges (JRP Historical Consulting 2004)
- Caltrans Statewide Historic Bridge Inventory Update: Metal Truss, Movable, and Steel Arch Bridges (JRP Historical Consulting 2004)
- Caltrans Statewide Historic Bridge Inventory Update: Concrete Box Girder Bridges (Myra L. Frank & Associates, Inc. 2004)
- Caltrans Statewide Historic Bridge Inventory Update: Concrete Arch Bridges (JRP Historical Consulting 2004)
- Caltrans Statewide Historic Bridge Inventory Update, Survey and Evaluation of Common Bridge Types (Caltrans 2004)
- City of Los Angeles Monumental Bridges 1900-1950, Historic Context and Evaluation Guidelines (JRP Historical Consulting 2004)
- Appendix A - Multiple Property Listing Guidelines
- Appendix B - Maps and Photographs of Bridges that Appear Eligible as City of Los Angeles Monumental Bridges
- Appendix C - Photographs of Bridges that Do Not Appear Eligible as City of Los Angeles Monumental Bridges
- Survey and Evaluation of Masonry Arch Bridges (Caltrans 2003)
- Historic Context Statement, Roadway Bridges of California: 1936-1959 (JRP Historical Consulting Services 2003)
- Historic Truss Bridges in California Thematic Determination of Eligibility (Caltrans 1985)
- Historic Bridges in California: Concrete Arch, Concrete Girder, Concrete Slab, Canticrete, Stone, Masonry, Suspension, Steel Girder and Steel Arch Thematic Determination of Eligibility (Caltrans, 1986)
- Historic Highway Bridges of California (Caltrans 1990). Copies of this publication are limited. Contact the for a copy.
Standard Environmental Reference (SER), Volume 2 - Cultural ResourcesVolume 2 of the SER provides guidance for the consideration of cultural resources, including historic bridges and tunnels, as a critical part of all phases of project development, construction, permitting, right of way, and maintenance activities. Caltrans must comply with federal and state environmental laws and regulations designed to protect cultural resources significant in American archaeology, architecture, history, culture, and engineering.
The following sources describe project development, construction, permitting, right of way, and maintenance activities that may need to be considered for compliance with federal and state environmental laws and regulations for historic bridges and tunnels:
- Highway Design Manual
- Bridge Memo to Designers
- Maintenance Manual
- Construction Manual
- Technical Manuals
- Project Development Procedures Manual
- Local Assistance Procedures Manual
Each of the twelve Caltrans District Offices has a Local Assistance Engineer who serves as the designated source of information and assistance on local agency projects that involve historic bridges; see Local Assistance Contact Information.
For Caltrans bridge technical specialists and bridge design engineers,see Offices of Structure Design.
Technical GuidanceBridge activities that do not need environmental review; that typically have no potential to affect historic properties; or that are completed in a manner consistent with the Secretary of the Interior Standards for the Treatment of Historic Properties in accordance with Caltrans 2014 First Amended Section 106 Programmatic Agreement Stipulation X.B.1 and upon review by Caltrans Professionally Qualified Staff (PQS) Principal Architectural Historian, will result in a no adverse effect on historic bridges or tunnels. The Caltrans Standard Environmental Reference Environmental Handbook, Volume 2, contains guidance for the situations described above in Chapters 4 and 7, Exhibit 7.3: Historic Bridges and Tunnels Screened Undertakings and Activities, and Exhibit 7.4: Historic Bridges and Tunnels No Adverse Effects with Standard Conditions.
- List of Common Bridge Design Terms and Definitions The Center for Environmental Excellence Historic Bridges Community of Practice forum provides an online glossary of common bridge design terms and definitions.
- Secretary of the Interior's Standards for the Treatment of Historic Properties These standards are federal regulations that provide an explanation of the four treatment approaches: preservation, rehabilitation, restoration, and reconstruction.
- Differences between cultural resources specialists and engineers in the technical vocabulary when referring to design treatments for historic bridges. Preservation professionals and bridge engineers use a different technical vocabulary when referring to design treatments for historic bridges, which results in differences in perspectives. Understanding the differences in technical vocabulary is vital to effective communication and collaboration on historic bridge projects. This document highlights the different perspectives on bridge activities based on the definitions of preservation, rehabilitation, restoration, and reconstruction in the Standards and the perspective of bridge engineers.
- A Management Plan for Historic Bridges in Virginia The Virginia Transportation Research Council adapted the Secretary of the Interior's Standards for the Treatment of Historic Properties for application to historic bridges. These standards have been interpreted and applied overwhelmingly to one type of historic resource (i.e., buildings). A Management Plan for Historic Bridges in Virginia addresses the unique requirements of historic bridges and identifies specific instances of the application of the Secretary of the Interior's Standards for the Treatment of Historic Properties to historic bridges.
- National Park Service Preservation Brief 15: Preservation of Historic Concrete This document provides guidance on appropriate cleaning methods for concrete on historic structures, including bridges and tunnels.
- National Park Service Preservation Brief 1: Assessing Cleaning and Water-Repellent Treatments for Historic Masonry Buildings This document provides guidance on cleaning historic masonry structures.
Federal Highway Administration - Environmental Review Toolkit and Bridge Preservation
The Federal Highway Administration (FHWA) assists in the preservation of historic bridges and encourages states to incorporate the concepts of context sensitive design in the rehabilitation and reuse of historic bridges. The FHWA website Historic Bridges Technical Assistance includes programs for historic bridge preservation:
- National Historic Covered Bridge Preservation Program
- Transportation Enhancements Program
- Highway Bridge Replacement and Rehabilitation Program
A more detailed description of the FHWA Bridges Technical Assistance is available in this document.
Other Information on Caltrans Bridges
- California Toll Bridge Directory
- The Toll Bridge Program - provides histories and facts about Caltrans toll bridges.
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