Rare dual-lane covered bridge in Vermont

Pulp Mill Covered Bridge, Middlebury Vermont

Date added: September 01, 2022

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The Pulp Mill Covered Bridge is the last dual-lane or "double-barreled" covered wood bridge to carry a public highway in Vermont, and one of two such bridges to survive in the state. In 1957 there were only six other double-barreled covered bridges remaining in the United States. The Pulp Mill Bridge is also the longest Burr truss bridge surviving in Vermont.

According to Herbert Wheaton Congdon, the Pulp Mill Bridge was probably built about 1820. This date ranks the Pulp Mill Bridge as the oldest covered bridge in Vermont, at least among those whose dates have been documented. Despite its age, the bridge continues to carry much local traffic on a paved road between Middlebury and Weybridge. Those towns also share ownership of the bridge, for it crosses the town boundary along the channel of Otter Creek.

The covered bridges of Vermont are among its most cherished and symbolic historic resources. About one hundred bridges still stand in the state, the greatest concentration by area of covered bridges in the country. Many of these bridges are integral parts of unique architectural environments whose physical setting and cultural context have been little altered until recently. Now, however, pervasive highway expansion, intensive commercial development, and physical neglect are changing drastically the historic environment and threatening the covered bridges.

The Pulp Mill Covered Bridge consisted originally of a dual-lane single span supported by two timber Burr arch trusses flanking a multiple kingpost truss between the roadways. The bridge has been considerably reinforced since its construction. Two piers have been built under the bridge, transforming it into a three-span structure (although the trusses have not been altered significantly).

In 1859 or 1860, four laminated (ten-layer) plank arches, each of which extends the entire original span and is anchored in the abutments, were added to augment the two original single-timber arches, The two outer laminated arches, which are directly above the original arches against the inner sides of the outer trusses, rise to the eaves of the bridge; the two inner laminated arches rise nearly to the ridge beam on either side of the center truss. The arches do not have framing beneath them, in contrast to applications of the Burr truss in some other bridges.

The abutments of the bridge are built of stone slabs, which subsequently have been faced with concrete. The piers are built of irregular stone and also have been partly faced with concrete. The piers are surmounted by timber cribbings that support the bottom chords of the trusses.

The overall length of the bridge is 199 feet. The trusses extend 181 feet; the remaining length occurs in the post-and-beam entries, which extend 8.5 feet at the east end and 9.5 feet at the west end of the bridge. The outside width of the bridge is 26 feet. The twin roadways are each 10 feet wide between the inner and outer arches. The wood floor consists of planks laid flat and perpendicular to the trusses, with strips of planks overlaid to the truss length of the bridge; the entries are paved.

On the exterior, the heavy timbers pegged together to form the trusses (and side walls) of the bridge are sheathed with unpainted flush boards hung vertically. The siding stops short of the eaves to leave strip openings along the tops of the walls. The gable ends are also sheathed with unpainted flush boards hung vertically. The shallow-pitch gable roof is now covered with standing seam metal sheeting.