Historic Bridge Management: A Comprehensive Approach
by Amy Squitieri and Mary Ebeling
New York boasts an extensive transportation network, including roads, railroads, and canals that tie together dispersed urban centers. Bridges are an integral part of this system, carrying roads and railroads over waterways, valleys, other roads, and parkways. In addition to being functional, bridges are recognized for their beauty and iconic stature—the soaring structure of a vertical lift bridge or the textured surface of a fieldstone arch. This article discusses New York State's efforts to identify, evaluate, and preserve significant historic bridges on public roads.(Figure 1)
Figure 1. The Roosevelt Island Bridge over the East River in New York City is an example of a vertical lift bridge. (Courtesy of Mead & Hunt, Inc.)
New York's recently-completed historic bridge inventory and management plan project is a comprehensive and ambitious approach to the preservation of the State's nearly 600 bridges listed in or eligible for the National Register of Historic Places. The inventory provides a methodology for evaluating a large population of historic resources. The management plan recommends best practices for bridge owners, whether State or a local government, that are consistent with both transportation and preservation needs. Developed by the New York State Department of Transportation (hereafter, Department of Transportation) in cooperation with a broad range of interest groups, the plan reflects a high level of coordination among preservation organizations and local bridge owners. Preservation consultants from Mead & Hunt, Inc., of Madison, Wisconsin, assisted by AKRF, Inc. of New York City, completed the historic bridge inventory and facilitated the cooperative effort that resulted in the management plan.
This article describes key elements in developing New York's historic bridge management plan. It discusses how early and intensive consultation with a working group of bridge owners and preservationists helped to shape the direction and success of both the inventory and management plan. It details how New York's management plan drew on lessons learned from other States during two decades of attempts to maintain historic bridges in transportation use. Finally, the article will argue that a flexible approach to historic bridge management—one that balances potentially competing interests of functionality and historic preservation—can strengthen the chances of a historic bridge's survival.
The New York historic bridge inventory and management plan project is rooted in more than two decades of Federal Highway Administration policy. The Surface Transportation Assistance Act of 1978 for the first time permitted States to use funds from the Federal Highway Administration's Bridge Replacement and Rehabilitation Program to conduct inventories of historic bridges. In 1980, the Administration adopted a policy that encouraged States to conduct such inventories.(1) Soon thereafter, New York and many other States undertook inventories to identify bridges eligible for listing in the National Register. As these first inventories became outdated or were found to be incomplete, State transportation agencies, including New York's, began to reassess and build upon their early efforts.
Also shaping this second look were the principles of Context Sensitive Design initiated by the Federal Highway Administration and the approach outlined in the Department of Transportation's 1998 Environmental Initiative. The Context Sensitive Design principles encourage planners and designers to preserve a community's historic resources, including bridges, in transportation projects. The Environmental Initiative acknowledges the agency's commitment to protect, conserve, or enhance the natural and man-made environment. Following these directives, the Department of Transportation committed itself to a transportation planning process that considers the importance of the State's environmental and historic resources.
The historic bridge management plan is the culmination of this effort. The plan was developed following completion of three major preliminary steps. First, a historic context for pre-1961 bridges was developed to provide background to support the evaluation of New York's historic bridges. Second, the Department of Transportation, the Federal Highway Administration, and the State Historic Preservation Office selected bridges for field examination. Third, the results of the field inventory were evaluated to determine National Register eligibility.
The historic context study served as the foundation for the historic bridge inventory and management plan. The study identified categories of bridges with potential historic and engineering interest and provided a basis for National Register eligibility determinations. The study's methodology focused on evaluating bridges by type, with particular emphasis on standardized designs.
Historical Background on New York State's Bridges
Bridge building went hand-in-hand with early European settlement of New York, facilitating the development of new communities. Until the beginning of the 19th century, towns struggled to support bridge-building activities. However, in 1801 the State passed a law giving county boards of supervisors the power to assist towns in undertaking projects.(2) This law marked the beginning of State involvement in bridge building.
During the 19th century, stone arch construction was common for short crossings. Longer crossings were typically traversed with wooden bridges. Covered bridges utilizing the Burr arch-truss or the Town lattice truss were dominant prior to the introduction of metal bridges in the 1870s.(Figure 2) A preference for metal bridges grew in the 1880s, although stone and wood continued to be used when materials and craftsmen were available.
Figure 2. The Blenheim Covered Bridge in Schoharie County is a single-span covered bridge constructed in 1854 and is designated as a National Historic Landmark. (Courtesy of Mead & Hunt, Inc.)
In response to the increased rate of bridge construction in the first decade of the 20th century, New York passed the Highway Law of 1908, establishing the New York State Department of Highways and directing it to supervise State-funded bridge projects. Centralization of the State's bridge program led to greater standardization in bridge design.(3)
In 1910, New York provided instructions to county and town superintendents on bridges, including suggestions on types and materials. The Department of Highways noted that stone arch bridges were still constructed at a reasonable cost where suitable material was available. Steel had replaced cast and wrought iron and was used for both truss and girder bridge designs. Eventually, concrete gained in acceptance.(4)
Although truss or steel girder bridge designs were prescribed for sites where soft soils could cause the abutments to move, the State continued to develop concrete bridge types. In 1909, the State issued standard plans for a range of truss types and the following year, issued typical designs for reinforced concrete I-beam and T-beam bridges.(5) Town and county officials quickly took advantage of the then 47 standard plans. They proved exceedingly popular and by 1912, 84 standard bridge designs were available.(6)
The establishment of the New York State Department of Public Works in 1923 expanded the use and dissemination of standard bridge designs. The new department developed standard designs for truss, slab, I-beam, T-beam, and plate girder bridge types.(7)
Despite the Great Depression, the Department of Public Works sponsored a record number of bridge projects in 1931, but the number of projects declined in the following years. With limited funding, the department sought to replace or strengthen load-restricted bridges located on major highways with high traffic volumes.(8) Although truss, concrete arch, rigid frame, and timber trestle bridges continued to be constructed, more economical beams, slabs, and girder bridges became the structures of choice during this frugal period.(9)
While the Depression slowed the pace of bridge building, the onset of World War II virtually halted construction as the State and the Nation faced critical shortages in labor and materials. However, the Department of Public Works continued to develop plans for new bridges. During the postwar period, the majority of bridges were rigid frames, slabs, and I-beams. The number of rigid frames slated for construction reflects the increasing emphasis on grade separation associated with parkway construction, and the need to separate underpasses and overpasses. Bridge-building activities up to the 1960s focused on completing bridges over the State's parkways; beginning work on the New York State Thruway; upgrading and maintaining the existing highway system; and experimenting with different types of materials such as aluminum, and longer span lengths utilizing new technologies like post-tensioning.
Inventorying the Statewide Bridge Population
The initial challenge of the historic bridge inventory was the sheer number of bridges—nearly 11,000 statewide—that appeared to meet the threshold 50-year-old requirement for National Register eligibility. The Department of Transportation decided to evaluate the eligibility of all bridge types built before 1961 so that the resulting inventory would be comprehensive and would not need to be updated for 10 years. This decision distinguishes New York from many other States that have limited their inventories to one type or one period at a time. For example, the 1990 inventory by the Ohio Department of Transportation—its second in a series—focused on bridges built during the 1940s. In 2001, Ohio published The Concrete Arch Supplement to the Ohio Historic Bridge Inventory, Evaluation and Preservation Plan, which addressed a single type.(10) To meet the practical challenge of evaluating the population of almost 11,000 pre-1961 bridges in New York, the consultant, Mead & Hunt, developed an inventory methodology to select a manageable number of bridges that warranted field review.
Four steps were used in the selection process. First, a contextual study defined areas in New York's bridge-building history and pinpointed the years that standardized plans were adopted. Second, the Department of Transportation's existing Bridge Inventory and Inspection System database was used to cull out structures other than bridges and bridges that are not owned or managed by the Department. Third, repair histories were used to identify bridges that had substantial alterations and, therefore, were not eligible for the National Register. Fourth, bridges were divided into groups based on their potential for National Register eligibility.
Applying this methodology, the Department of Transportation, in cooperation with the Federal Highway Administration and the State Historic Preservation Office, determined which bridges needed to be examined in the field. The rest would be evaluated based on information already available in existing files and databases.(Figure 3)
Figure 3. This open spandrel concrete deck arch carrying Route 30 over Mine Kill in Schoharie County was included in the field review and was determined to be eligible for the National Register. (Courtesy of Mead & Hunt, Inc.)
As the first step, Mead & Hunt, assisted by AKRF Inc., prepared the historic context study of New York State's pre-1961 bridges. The study established a framework for understanding the historical and engineering significance of the bridges within their statewide context. This research and the review of department records helped establish the evolution of standard designs. In addition, questionnaires were distributed to preservation organizations, local historians and historical societies, and county highway superintendents seeking information about bridges deemed significant by communities across the State.
The second step in the inventory methodology used the Department of Transportation's Building Inventory and Inspection database to eliminate bridges outside the scope of the project. Assistance from the database manager at the Department of Transportation proved critical to this process. Bridges in four categories were excluded: those not managed by the Department of Transportation; those previously evaluated for inclusion in the State or National Registers; structures (culverts, ramps, and tunnels) other than bridges; and those with a superstructure replaced after 1960.(11) This process eliminated important historic structures, such as the Brooklyn Bridge, that are maintained by other agencies.
In the third step, bridges were eliminated from further consideration if they had major alterations, such as new or replaced main members or substantial widening. Photographs and construction records in bridge inspection files were used to determine the scale of alterations. These three steps reduced the bridge population for which additional information was needed to approximately 5,100 bridges.
Following these exclusions, bridges were sorted into subgroups based on defining features including bridge types (arch, beam/girder, movable, suspension, and truss); variations within types; construction materials; and construction dates, including whether pre- or post-standardization. Uncommon bridge types, identified as such in the research for the contextual study, like trusses (other than the Warren, Pratt, and Parker types), and suspension and movable bridges, were put in a single subgroup because of their rarity.
Other bridge types—including arches, beams/girders, and common trusses—were organized into more specific subgroups to help identify significant examples. For example, arches were classified by material into steel and masonry subgroups. Concrete arches were then further divided by deck arches and through arches. Deck arches were then divided into open spandrel and closed spandrel subgroups. Beam and girder subgroups included I-beam, rolled beam, rigid frame, jack arch, box girder, through girder, continuous beam, slab, and T-beam. Common trusses were divided into Warren, Pratt, and Parker types. Common trusses and beams and girders were also divided into pre- and post-standardized construction.
The subgroup divisions also recognized special features of bridges. These bridges may have been constructed by a well-known builder or designer, possess important historical associations, or display distinctive aesthetic treatment. A jack arch bridge constructed by the Works Progress Administration that includes a decorative stone veneer would be an example.
After the bridges were divided into subgroups, structures were chosen for the field survey based on the number of bridges in the subgroup, the significance of the subgroup, the presence of any special features, and whether the bridge had been altered. The entire population of the uncommon bridge types was surveyed. A sample of beam/girder bridges that retained integrity—not even minor alterations—and that possessed significant traits, such as a known historical association, were selected for field study. The selected beam/girder bridges were cross-checked against the entire population of this type and found to be representative of the subtypes, materials, geographic location, and ages of bridges found in the larger group.(Figure 4)
Figure 4. This uncommon multiple-span lenticular truss bridge carrys Dutchtown Road over the Susquehanna River in Broome County and is listed in the National Register. (Courtesy of Mead & Hunt, Inc.)
Implementation of the inventory methodology resulted in the selection of 1,900 bridges (out of approximately 5,100) for field survey. Surveyors used an individual survey form for each bridge that included preprinted information obtained from the existing bridge database. Surveyors confirmed or corrected existing data, recorded new information, and photographed each bridge.
Ultimately, nearly 600 historic bridges meeting National Register criteria were identified. Eligibility decisions reflected a consensus among the major parties concerning all pre-1961 bridges that are managed by the Department of Transportation on public roads in the State. The Historic Bridge Database compiled these eligibility determinations with information specific to the individual bridges.(12) With this information, the Department of Transportation proceeded to develop a management plan for this population of National Register-listed and eligible bridges.
New York State's Management Plan
The Department of Transportation's goal for this project was to develop and adopt management practices for an identified historic bridge population. Throughout the project, the participation of a representative from the Department of Transportation's Structures Division, and of regional structural engineers and bridge maintenance engineers, contributed to a focus on workable recommendations that would keep bridges in use. These engineers worked closely with the consultant and the Department of Transportation's Environmental Analysis Bureau, which spearheaded the project. The final historic bridge management plan satisfied participants by recommending practices that are consistent with the needs of both transportation and preservation.
Through use of the plan, the Department of Transportation encourages the preservation of locally-owned historic bridges in the State by disseminating and sharing maintenance recommendations. They include pressure washing; improving drainage and water flow on the deck; maintaining bearings; repairing cracks in the superstructure with similar materials; tightening truss members; spot-painting metal components; and repairing and/or replacing decking, joints, and railings with compatible materials.
Learning from Other States
New York's management plan draws on lessons learned from other State's often unsuccessful attempts to preserve historic bridges in transportation use. Consultant AKRF, Inc. conducted in-depth interviews with transportation and historic preservation staff in nine States actively pursuing historic bridge preservation programs.(13) The consultant also collected and reviewed management plans and preservation agreements that had been prepared by these and other States.(14)
It was clear that States have benefited from an inclusive approach to evaluating their stock of bridges. However, due to the expense of a comprehensive, statewide historic bridge inventory, many States opt to tackle the project in phases, looking at one type or period at a time as funds become available. Scheduled, periodic updates of the inventory were also found to be useful as they allow for the recognition of newly eligible bridges and the reconsideration of previous determinations, if necessary.
Other practices contribute to the effectiveness of management plans. Early consideration of management options has proven useful as owners identify the condition of their historic bridge(s) and evaluate preservation options prior to scheduling a rehabilitation or replacement project. Annual review of the management plan with participating agencies was also recommended to encourage continued commitment among agency representatives and accommodate staff changes. Another helpful management tool is a well-maintained tracking database to facilitate rapid retrieval of information on individual historic bridges and aid in maintaining up-to-date information on each bridge covered by the management plan. Alternate or flexible engineering standards allow a bridge's historic integrity to be maintained while current safety and traffic needs are met.
Other policies and programs that support bridge preservation include intergovernmental agreements, bridge adoption programs, and flexible design standards. Programmatic agreements have been used by many States to comply with Section 106 of the National Historic Preservation Act and provide an operational framework for implementation of a State's historic bridge management practices. Transportation agencies have also used agreements with bridge owners to obtain local responsibility for historic bridges that do not fall under the State's jurisdiction. Although finding new owners for historic bridges has often been difficult, targeted reuse campaigns have succeeded that match bridges with organizations or government units that have a real need.
Incentives to encourage bridge preservation have been offered in the form of both funding and education programs. Programs such as the Transportation Equity Act for the 21st Century (TEA-21) have been used to fund bridge maintenance and rehabilitation and can help overcome the difficulty of financing a historic bridge preservation project. Educational programs have been used to inform agency personnel, bridge owners, historical organizations, and interested members of the public about management practices and preservation opportunities. Some States have sponsored workshops on bridge rehabilitation.
Innovative techniques include the application of new bridge rehabilitation methods and the promotion of awards and easement programs. Virginia has used two pioneering rehabilitation methods: galvanization instead of repainting for steel bridges and reinforcement of masonry arches with grout anchors. Ohio annually recognizes county engineers who demonstrate a commitment to historic bridge preservation through successful or innovative rehabilitation projects. In Vermont, towns may sign a participation agreement conveying an easement to the State, giving up certain development rights for a bridge and agreeing to conduct basic maintenance. In return, the State funds the rehabilitation of the bridge and pays for future, more significant maintenance on the bridge.
Other States related challenges in preserving historic bridges. Bridge storage and relocation efforts have often been unsuccessful, perhaps due to ineffective marketing techniques or the lack of need for a bridge with limited function. Insufficient funding remains a pervasive problem for historic bridge preservation projects. In addition, the absence of methods to track the costs of bridge rehabilitation hinders a realistic comparison of management options. Transportation agency representatives interviewed stated that owners may prefer a new bridge to meet their transportation needs and speculated that this was due to concerns over cost, maintenance, and potential load restrictions. Inadequate public education or participation in planning processes fails to build an understanding of historic bridges and support for preservation options.
Based on the analysis of other States' efforts, three factors were considered to be key to long-term success and were incorporated into the New York management plan. First, including many parties in developing the plan encourages cooperation from a wide range of bridge owners and historic preservationists. Second, a comprehensive approach extends the plan to all listed and eligible bridges in the State and provides flexibility for bridge owners. Third, the plan reflects a balance between function and preservation to maximize the chances for saving historic bridges.
Outreach and Inclusivity
In accordance with its environmental policy, the Department of Transportation recognized that successful implementation of the plan depended on strong local support, reflecting the needs, interests, and values of local communities and organizations that own historic bridges. Developing the plan with a high level of participation by county and local representatives was viewed as an important first step to gaining its broad acceptance.
Early outreach efforts involved local governments across the State in developing the management plan. As part of this outreach, the Department of Transportation and its consultant made presentations about the historic bridge inventory and management plan project at conferences attended by local bridge engineers and county highway superintendents and at the New York State Office of Parks, Recreation, and Historic Preservation.
The Department of Transportation recognized the need for continuing consultation throughout the development of the management plan. A working group of representatives from the Department's main office and regional offices, the Federal Highway Administration, the State Historic Preservation Office, county governments, statewide preservation organizations, and the County Highway Superintendents Association participated in a series of meetings that shaped the final management plan. Participants offered strategies for problem solving from the local government perspective and reviewed and commented on an outline and drafts of the management plan.
Comprehensive Approach and Maximizing Preservation Potential
The Department of Transportation consciously avoided a "one size fits all" management approach. By focusing on bridge types rather than individual bridges, the historic bridge management plan is applicable to the State's nearly 600 National Register-listed and eligible bridges and allows engineers and preservationists flexibility in crafting individualized plans for their bridges.
By providing a range of options for preserving the State's historic bridges, the Department of Transportation addressed the challenge of maintaining functionality and historic integrity. This flexibility should increase the chances for the preservation of the State's historic bridges. Safety concerns and changing transportation needs will present a recurring challenge for preservationists and engineers planning the rehabilitation of a historic bridge. It is often difficult to retain a historic truss bridge, for example, if the current traffic volume requires widening of the bridge. In this situation, bridge engineers may find themselves in an intractable position. The cost of the widening may be prohibitive compared to building a new structure. Widening the bridge could damage the qualities that made the bridge eligible for the National Register.
The funding solutions provided in the management plan also point to creative options that may ease the fiscal problems often encountered when preserving a historic bridge. These options may include the use of grants available through the State's Environmental Protection Fund, which provides funding for preservation projects, or the Preserve New York grant program administered by the Preservation League of New York State, which supports planning studies by nonprofit groups and local governments. These funding sources are in addition to the more commonly known funds, such as the enhancement funds available through TEA-21.
Following the recommendations in the management plan, bridge owners can analyze their historic bridges and set priorities for maintenance and rehabilitation. To help local governments establish priorities for historic bridge maintenance and rehabilitation, they are encouraged to complete a condition assessment and then prioritize bridges needing maintenance or rehabilitation using their own criteria. If they identify a projected budget shortfall, counties, cities, and towns have been advised to work with Department of Transportation to arrange funding for bridge maintenance and rehabilitation.
New York's experience with its historic bridge inventory and management plan project offers guidance for others involved in the inventory and analysis of large numbers of historic resources. The creation of a database of New York's historic bridges greatly simplified implementation of the inventory methology. The ability to track the status of National Register-listed and eligible bridges is one of the most important long-term benefits of the database.
To monitor the effectiveness of its management plan, the Historic Bridge Database will be updated annually to reflect bridges that have been removed or replaced, or changes in eligibility status. Based on these updates, new paper copies of lists of eligible, listed, and noneligible bridges will be generated and distributed to the regions. The regions may then inform local governments of any changes in the status of locally-owned eligible or listed bridges. In future years, the Department of Transportation will be able to access information on whether historic bridges are being retained for continued use and by whom.
The Department of Transportation anticipates that its plan will streamline the management of historic bridges and result in the best possible chance of their survival, consistent with transportation needs. Continued outreach to local units of governments will help to strengthen its prospects. Engineers, government officials, and the public can benefit from additional education on why historic bridges should be preserved, how to approach preservation projects, and how rehabilitation projects can succeed.
The management plan discusses options for outreach, including producing a booklet on bridge maintenance and rehabilitation issues to distribute to engineers. Another possibility is a publication on New York State's historic bridges that would be distributed to historical societies and libraries. As part of the outreach effort, the Department of Transportation has placed the documents produced for the Historic Bridge Inventory and Management Plan project on its Website, http://www.dot.state.ny.us/eab/hbridge.html. The Department of Transportation is well-positioned to track the plan's impact over time through the database developed as part of this project. The project demonstrates how a public agency can address a large group of historic resources and serves as a model for the preservation of significant bridges.
About the Authors
Amy Squitieri is an architectural historian and manages historic preservation services for Mead & Hunt, Inc., a national engineering and architecture firm. Ms. Squitieri served as the project manager for the New York bridge project from 1999 to 2002. Mary Ebeling is an architectural historian formerly with Mead & Hunt, Inc.
1. William P. Chamberlin, Historic Bridges-Criteria for Decision Making (Washington, DC: Transportation Research Board, 1983), 12.
2. Charles H. Betts, Highway Manual of the State of New York (Albany, NY: New York State Statutory Revision Commission, 1904), 260.
3. New York State Archives and Records Administration, Guide to Records in the New York State Archives (New York: New York State Archives and Records Administration, 1993), 308.
4. New York State Department of Highways, Directions Prescribed by the Commission for the Guidance of County and Town Superintendents Regarding the Erection and Repair of Bridges (Albany, NY: J.B. Lyon Co., 1910), 22.
5. "Historic Bridge and Road Survey for Cattaraugus County," correspondence file, Mead & Hunt, Inc., 1999; "Building-Structure Inventory Form for the Lyndon Road Bridge," collection of the New York State Historic Preservation Office; New York State, Directions Prescribed, 24-26, Plates 8-11.
6. New York State, Report of the State Commission of Highways for 1910 (Albany, NY: J.B. Lyon Co., 1911), 471; New York State, Report of the State Commission of Highways for 1912, 418.
7. New York State Department of Public Works, Annual Report of the Superintendent for 1925, 15; New York State Department of Public Works, Annual Report of the Superintendent for 1926, 8.
8. New York State Department of Public Works, Annual Report of the Superintendent for 1932, 106.
9. Ibid., 105.
10. Ohio Department of Transportation in cooperation with the Federal Highway Administration, The Second Ohio Historic Bridge Inventory, Evaluation and Preservation Plan (Columbus: Ohio Department of Transportation, 1990); Ohio Department of Transportation in cooperation with the Federal Highway Administration, The Concrete Arch Supplement to the Ohio Historic Bridge Inventory, Evaluation and Preservation Plan (Columbus: Ohio Department of Transportation, 1994).
11. Previously evaluated bridges included those already determined eligible or ineligible and those listed in the State Register and/or National Register.
12. A discussion of eligible bridges by type is included in the consultant's report, Mead & Hunt, Inc. and AKRF, Inc., "Evaluation of National Register Eligibility" (Albany: New York State Department of Transportation, Environmental Analysis Bureau, January 2002).
13. The surveyed States were Connecticut, Georgia, Montana, New Jersey, Ohio, Pennsylvania, Texas, Vermont, and Virginia. Renewable Technologies, Inc., completed a comparative analysis of all States' historic bridge activities in 2001. See Rossillon Mitzi, "A Comparative Inventory of Statewide Historic Bridge Mangement Planning Efforts (Draft)" (North Dakota Department of Transportation, Bismarck, ND, March 29, 2001). The results influenced the selection of States that were contacted for this project.
14. These experiences were summarized in an interim report. Mead & Hunt, Inc. and AKRF, Inc., "Survey of Selected States with Historic Bridge Management Plans" (Albany: New York State Department of Transportation, Environmental Analysis Bureau, June 2001).