Fisher Covered Railroad Bridge - Chub Bridge, Wolcott Vermont

Date added: May 19, 2024

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The Fisher Covered Railroad Bridge is unique in Vermont, being the only covered wood railroad bridge in the state which still carries an active railroad, (Two other covered railroad bridges, at Swanton and East Shoreham, remain in the state but the railroad lines which they carried have been abandoned and their tracks removed.) Nationally, the covered railroad bridge has nearly disappeared; according to Richard Sanders Allen (1974), there are only twelve examples of the bridge type left in the United States. The Fisher Bridge, therefore, is nationally significant for being among the last survivors of the thousands of covered railroad bridges that were built during the railroad expansionist era of the latter 19^th century.

The Fisher Bridge is the latest of the three remaining covered railroad bridges in Vermont to have been built. The Boston and Maine Railroad, which controlled the St. Johnsbury and Lake Champlain Railroad at the time, constructed the bridge in 1908; the architect or design engineer is unknown. The lower cost of wood construction compared with that of wood-iron (Howe truss) or iron undoubtedly accounted for its extraordinarily late use on the lightly trafficked line.

The design of the Fisher Bridge incorporates a feature unique among the covered railroad bridges in Vermont, a louvered monitor that extends nearly the full length of the roof along its ridge. The monitor (which does not appear on the original engineering drawings of the bridge) served to allow locomotive smoke to escape from the bridge. Superfluous since the introduction of diesel locomotives on the railroad, the monitor remains to give the bridge its distinctive architectural character.

In 1968, when the management of the St. Johnsbury and Lamoille County Railroad rebuilt several bridges along the line to accommodate heavier train loads, the Fisher Bridge was threatened with demolition. The Vermont Board of Historic Sites (now the Vermont Division of Historic Sites), together with other parties, intervened to arrange for the preservation of the distinctive super-structure of the bridge. To provide the required load-bearing capacity, the timber deck structure of the bridge was removed and a steel deck truss structure was built to carry the track, independent of the timber trusses.

Bridge Description

The Fisher Covered Railroad Bridge consisted originally of a single span supported by two flanking timber Town double lattice trusses. In 1968 the timber deck structure was removed and replaced with a two-span steel deck truss structure independent of the wood superstructure. The southerly span is supported by two plate girders and the northerly span by four steel I-beams.

The yellow pine trusses, each of which has an extra set of diagonal lattice members for additional strength, now support only the superstructure of the bridge. Lateral iron rods connect the top chords of the trusses through the apexes formed by the upper lateral braces. Ship's knees provide reinforcement between the principal top beams and vertical posts near each corner of the bridge.

The superstructure of the Fisher Bridge is 103.5 feet long overall. The two steel spans are 42 and 51 feet long, respectively north and south. The superstructure is 20.5 feet wide, and has an interior opening of 15 feet for the track.

The entire bridge rests on abutments built of stone blocks mortared together and capped with concrete. The lower half of the north abutment has been faced with concrete. The steel spans rest on a central pier built of timber pilings sheathed with dimension stock. Concrete back-walls retain the track bed at each end of the bridge.

On the exterior, the heavy planks pegged and bolted together diagonally to form the trusses (and side walls) of the bridge are sheathed with unpainted matched spruce boards hung vertically. Similar siding protects the ends of the trusses immediately inside the portals. The siding flares outward toward the bottom of the bridge to cover the bottom chords. The siding stops short of the eaves to leave strip openings along the tops of the walls.

The gable ends are sheathed with unpainted matched clapboards hung horizontally. The portal openings have diagonal upper corners to match the interior struts. The siding flares diagonally outward beyond the line of the side walls to meet the eaves.

A shallow-pitch gable roof covers the bridge. A wood monitor with louvered sides, which served as a smoke ventilator, extends nearly the full length of the ridge. The roof and monitor are covered with asphalt roofing paper.