The Eleventh Street Bridge is a unique configuration of a double-intersection Warren through truss, with a pair of trusses on either side of the roadway, and lateral bracing between each pair, but none over the roadway. The bridge was engineered by the Eastern Bridge & Structural Co. of Worcester, Massachusetts, a significant twentieth-century bridge manufacturing firm. The bridge was paid for and erected by the Turners Falls Company for the town of Montague, during a very significant period (1912-1915) of the hydro-electric development of Western Massachusetts.
Documentary evidence for the Eleventh Street Bridge seems to indicate that it was originally designed to be very similar to the bridge at Sixth Street. The original plans for the bridge, drawn up by the Eastern Bridge & Structural Company in May of 1914, show a double-intersection Warren through truss, with a 21-foot wide roadway, upper lateral bracing, and no sidewalks. A second set of plans for the same bridge, dated May, 1915, shows a pair of double-intersected Warren trusses on either side of a roadway 27 feet wide, with a 6-foot wide sidewalk running between each pair of trusses. Rather than the standard upper lateral bracing over the center barrel, the second set of plans shows lateral bracing only over the sidewalk barrels. The two inner trusses are referred to, on several of the sheets, as "old trusses," with a job number that refers back to the previous set of plans. Why did this change in plans occur? Even after a considerable amount of research, there does not appear to be a conclusive answer, but apparently, some discrepancy arose between the Turner Falls Company, which was paying for the bridge, and the residents of the town, who were the beneficiaries of the whatever infrastructure changes the company were [sic] required to make.
On October 23, 1914, at a town meeting, the town voted:
"that the bridge to be built across the new canal at Eleventh Street in the Village of Turners Falls shall have a roadway of not less than thirty (30) feet in the clear, it shall have two sidewalks one on each side, each walk shall be six (6) feet in the clear, with suitable guard on the outside of such walks to prevent children from falling from bridge into the the canal and that the town of Montague demand that the bridge be built by the Turners Falls Company as mentioned above..."
A few months later, on March 25, 1915, that vote was rescinded, and another vote was passed, authorizing the Turners Falls Company "to construct a steel bridge across the new canal at Eleventh Street in Turners Falls which shall have a roadway twenty-seven (27) feet in width and one (1) sidewalk six (6) feet wide on each side of the said roadway."
Clearly, there was some discrepancy between what the Turners Falls Company had made plans for, and what the town felt it needed. While this suggests that general basis for the changes in plans for the Eleventh Street Bridge, there are apparently no written record as to the specifics of those changes. The original plans called for a narrow bridge (21 feet wide), with no sidewalks; the later plans showed a much wider bridge (27 feet), with a 6-foot sidewalk on either side. While this change could have been made quite easily on the drawing board, a considerable amount of time had passed since the initial plans were drawn up, and the reference on the drawings to 'old trusses' indicates that they had already been fabricated, and perhaps even shipped to the site by that time. Increasing the size of the bridge and adding sidewalks meant that the already-fabricated trusses would have had greater dead and live loads to carry, probably more than they could bear. Instead of designing and fabricating a new bridge and scrapping the old, which could have been quite costly, the engineers apparently decided to increase the load-carrying capacity of the old trusses by adding two identical trusses to the design. Once that was done, and the width of the bridge was increased, new lateral bracing was necessary. By spanning the shorter distance between the outer and inner trusses, rather than the entire distance between the two outer trusses, the strut sizes could be considerably reduced. As finally constructed, the Eleventh Street Bridge represented a unique engineering solution to a project influenced by both public and private interests.
Documentation of the Eleventh Street Bridge is part of the Massachusetts Historic Bridge Recording Project, conducted during the summer of 1990 under the co-sponsorship of HABS/HAER and the Massachusetts Department of Public Works, in cooperation with the Massachusetts Historical Commission.
Lola Bennet, HAER Historian, August 1990