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July 11, 2002 - Work on the Middlebury/Weybridge Pulp Mill Bridge Continues. With a start date of June 10, the span is scheduled to reopen August 9.
       The old "double-barrel" bridge stands in a tight little urban neighborhood. Its importance to the neighborhood and the larger community becomes evident when the bridge is closed--the towns usual traffic patterns are disrupted as bridge users crowd alternate routes.
       The Pulp Mill is the only two-lane covered bridge in Vermont that carries regular daily traffic. Vermont s other two-laner originally served Cambridge. It now stands next to Route 7 in Shelburne and is used as an entry for staff at the Shelburne Museum. This tally does not count Windsor's two-laner over the Connecticut River, because 99% of it is in New Hampshire.

Work continues on the middle truss of the west span, rebuilding the chord, staggering joints, adding shear blocks, shouldering, and check braces. Photo by Joe Nelson, June28, 2002	As work progresses on the middle truss of the "double-barrel bridge," the roadway is taken up to gain access to the middle chord. Access is incidentally gained to the outside truss chords also in need of work. However, funds and the contract cover only the middle truss. Photo by Joe Nelson, July 11, 2002

       The 184-foot Pulp Mill Bridge once crossed the Otter Creek with a single span. According to the Vermont Agency of Transportation covered bridge inspection report, the two concrete piers topped with timber cribs we see today were built in 1979. When the bridge was subdivided into three spans, the direction of half the braces had to be reversed. The stone abutments were capped and faced with concrete and the laminated arches rebuilt. Additional work was done in 1991 by Jan Lewandoski.
       According to Mr. Lewandoski, when the Pulp Mill bridge was constructed, the builders overlooked several key details. The posts, which receive heavy braces, don't shoulder within the chords. That is, the notched posts aren't fitted into lower chord members notched to receive them, latching them in place. Instead, the bottoms of the posts are reduced in thickness to fit between the chord members and held there with a single bolt. The tremendous load of the nearly two-hundred- foot-long span transmitted through the braces set at the bottoms of the posts would break the posts, sliding them between the chord members. The bridge started failing right away, and carpenters have been fixing it ever since.

The large metal plate on the upstream chord is a splice installed by the State in the 1980s. This view also details one of the laminated arches at the west abutment. Photo by Joe Nelson, July 11, 2002	The new and the old -- The kingpost on the right, part of the original construction, was lap-cut to fit between the lower chord-members secured only by one bolt. The original chords were not lapped to provide shoulders to lock the kingposts in place. Photo by Joe Nelson, July 11, 2002

       Early efforts were made to strengthen the truss with Burr-style segmented timber arches--when the arches were added is uncertain. In the 1860s these were augmented with laminated arches of three-inch planks, using the original arch as a form.
       Today, there are two large arches between the lanes that rise nearly to the ridge pole. A smaller arch rises to the eaves on each side. The center arches, consisting of a lamination of ten three-by six-inch planks, are bolted to both sides of a central multiple-kingpost truss. The outer arches are a lamination of nine three-by six-inch planks each bolted to the inside of a multiple-king post truss. There is no longer any evidence of the original segmented timber arches.

A close-up of the kingposts, new vs. the original. The original lap-cut left very little material where the post passes between the chord-members. Photo by Joe Nelson, July 11, 2002	A view of the center chord system. The truss chord members here are being reworked to provide needed shouldering for the kingposts. The knob-ends of two kingposts can be seen here. Photo by Joe Nelson, July 11, 2002

       There is access to the creek at the southeast side of the bridge approach. From there, at low water, the entire length of the bridge with piers and abutments can be viewed from the dam. Note that the ends of the arches are bedded in the abutments below the main stringers. Most of the other Vermont bridges built in the "Burr manner" terminate the ends of the arches at the bottom chords above the abutments.
       Besides being on the National Register of Historic Places, the Middlebury town plan identifies the bridge as a Scenic Roads Resource, giving it additional preservation status. The Town of Weybridge was awarded a grant to fund the pedestrian bridge beside the covered bridge.
The Pulp Mill Bridge was named for a wood-pulp mill that operated nearby. It is located on Weybridge Road on the Weybridge-Middlebury town line and is maintained by both towns.

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Joe Nelson, P.O Box 267, Jericho, VT 05465-0267, jcnelson@together.net

No part of this web site may be reproduced without the written permission of Joseph C. Nelson
This file posted July 15, 2002, revised September 18, 2002