Hibernia Mine Railroad Bridge

Information and Findings From New Jersey's Historic Bridge Inventory (Previous Bridge Location)

Summary

The skewed Pratt thru truss bridge is fabricated with the patented Phoenix columns for the top chord, inclined end posts, verticals, and struts. Despite its deteriorated condition, the bridge, on ashlar abutments that date to 1869, has not lost its integrity. It is the only extant Phoenix column span in the county, which is known to have had many. The Mill Lane bridge is thus the sole survivor of the earliest type of metal truss bridge built in Somerset County. It is technologically notable.

Setting/Context

The one-lane bridge is located on an abandoned road over the abandoned right-of-way of the former South Branch of the Central Railroad of New Jersey. The surrounding area is wooded, and the old road and bridge serve as a pedestrian way. The active Conrail freight line on the Lehigh Valley line is immediately southeast of the bridge. A stringer bridge carries the abandoned road over that line. The thru truss bridge is only seasonally visible from Mill Lane.

Physical Description

The 10-degree skew, 5-panel, pin-connected, half hip Pratt thru truss bridge is composed of wrought iron Phoenix sections for the compression members. The top chord, inclined end posts, portal struts, and verticals are the patented built-up Phoenix columns. Phoenix columns are made up of four rolled wrought segmental sections with flanges that are then riveted together. The individual built-up column sections are then joined by patented cast iron connecting pieces and feet or bearings also produced by the Phoenix Iron Company. The diagonals and full-length floor beam hangers are rectangular rods with loop forged eyes. The floor beams are rolled I section and are not original to the bridge, although they are attached by means of the traditional floor beam suspenders at the lower panel point pin. Despite its deteriorating condition, the single-lane bridge appears to be capable of supporting load, although the high ashlar abutment is failing. The large modern rolled I-section welded to the bottom flange of the floor beams was the first step in an uncompleted attempt to jack up the bridge.

Historical and Technological Significance

The 1879 bridge built by Clarke, Reeves and Co. for the Hibernia Mine Railroad is historically and technologically significant as an early and documented example of rail-carrying bridge built with the patented Phoenix section (criterion C). The Phoenix section, patented in 1862 by Samuel Reeves, President of the Phoenix Iron Company, was one of the most significant developments in the advancement of metal truss bridges in the 1870s. Originally applied to buildings, the company recognized the value of its use in bridges about 1868. The section was also used in early elevated street railway lines in New York City and vicinity. In 1872 Clarke, Reeves and Company was formed to handle the bridge building side of the business, and Clarke, Reeves and Company concentrated primarily on railroad rather than highway bridges. The railroads were by far the largest user of metal truss spans and viaducts through the 1870s and early 1880s. Because railroad bridges with Phoenix sections represent first-generation railroad bridge technology, and thus an era when rolling stock and loads were not what they would become in the 1890s and 1900s, few railroad Phoenix-column bridges survive. They were replaced by stiffer, stronger bridges. The history of this span is recorded in the Clarke, Reeves and Company order books preserved at the Hagley Museum and Library. With the exception of the removal of the original floor system, with its stringers and rail chairs related to its original railroad use, the span is complete, and it illustrates that overall there was no difference between some Phoenix-section railroad and the highway bridges. The skewed through truss bridge was moved to this location by 1894, and it was installed as a grade crossing elimination by the Central Railroad of New Jersey on its South Branch. Railroad records indicate that "this bridge was transferred from the Hibernia (Mine) Railroad," a short line chartered in 1863 and operated by the CNJ. What is meant by "transferred" is not known, but it is assumed to mean moved. The span is the oldest metal truss bridge in the county and one of the oldest thru truss spans in the entire state. It is the second oldest of the eleven surviving bridges with Phoenix columns in the state and the only one built as a railroad bridge. It is the only one that was built by Clarke, Reeves and Company, the successor of the Phoenix Bridge Company (organized in 1884).

Boundary Description and Justification

The bridge is evaluated to be individually significant. While the setting is not devoid of history, it the technological and historical importance of the bridge that sets it apart. The boundary is limited to the superstructure. The substructure is too deteriorated to possess the integrity of original design needed to be evaluated as significant. The railroad right-of-way that the span crosses has been abandoned. It is overgrown.

Sources

Conrail. Bridge File 241-2. Waddell, J.A.L. Bridge Engineering. New York: John Wiley and Sons, Inc., 1925. Hagley Museum and Library. Phoenix Bridge Co. Records: Clarke Reeves and Co. 1874-1884, Order Books (boxes 363-367).

Bridge Considered Historic By Survey: Yes