Jeffersonville, April 27, 2004 - Rehabilitation work began on the Canyon Covered Bridge off Route 108 in Jeffersonville on Monday, April 26. The contractors are Blow and Cote Construction of Morrisville, Vt.
The 97-foot Canyon Bridge [WGN 45-08-01], also known as the Gristmill Bridge, the Scott Bridge, and as the Alden Bryan Bridge, crosses the Brewster River just above the Brewster River canyon. The bridge is constructed with a Burr Truss. The date it was built is unrecorded, however a good guess would be circa 1870. The name of the builder is unknown.
The contractors are planning to move the bridge off of the river and onto Canyon Road to better facilitate work on the bridge's lower chords. Inspection has discovered rotational cracks on the inside center members of the chords of both trusses, said Nathan Cote, foreman on the project.
The siding, roof system and bridge deck, or roadway, will be removed and the two trusses will be lifted by crane to lay flat to allow the chords to be disassembled for replacement of the failing members. In addition to the cracked chord members, it was found that in the past, rotted chord ends had been sawed off and patched, These areas will be redone, Cote said.
The plan calls for retention of all serviceable original fabric as was done on Montgomery's Comstock Bridge last season. Everyone was pleased with the work done there, Cote recalled.
Canyon Bridge rehab progress, second day. The upstream siding has been removed and the stripping of the roof sheathing begun.
Removal of the old metal roof reveals even older wooden shingles.
View from east portal. The running planks are being removed in preparation to taking up the bridge deck and floor timbers. All serviceable timbers will be retained.
View of the east abutment. Broken stone and voids were found by the inspection team. It was recommended that a stone mason repair and "re-chink" it in the old way, without the use of mortar.
Jeffersonville, May 19, 2004 - Canyon, or Gristmill Bridge rehabilitation project was opened for bids on January 9, 2004. The low bid, by Blow and Cote Construction of Morrisville, Vt., was $466,057.05 The only other bidder, Contractor's Crane Service, also of Morrisville, bid $623,318.00. The Engineer's estimate was $354,101.50.
The engineering and inspections were done by McFarland-Johnson, Inc. of Binghamton, N.Y. for the Vermont Agency of Transportation. The project is funded through the Vermont Agency of Transportation with 80% federal, 10% state, and 10% from the Town of Cambridge.
When the work is completed the bridge will have an ASHTO live load rating of H-5, or 10,000 pounds.
The contract calls for the contractor to avoid unnecessary disassembly of the truss and roof system. Only the joints that affect repairs to the trusses shall be disassembled. The contractor is also required to stockpile all reusable timbers and boards for reuse, and dispose of deficient timbers and boards. The existing deck planks and timbers, and distribution beams shall remain the property of the Town of Cambridge.
The bridge floor system will be replaced "in kind", there is no plan for the use of Glu-lam. New structural timber will be eastern spruce, the siding timber, hemlock, and the bolster beams and bedding timbers will be southern yellow pine.
View from upstream, siding and roofing removed.
A classic floor system construction. The transverse sub-floor timbers you see are resting on joists which are in turn laid on the 8 x 8 floor beams. These support the flooring, some of which can be seen on the left. The flooring was protected by oak running planks now removed. Hanging beneath all this are distribution beams, probably added in the 1970's. All but four of the original floor beams will be reused.
These roof system components, "historic fabric," will be re-installed as work on the bridge is completed.
The Blow & Cote team Nathan Cote, Roland Blais, and David Morrell lever up the floor boards. These and the rest of the floor system will be "replaced in kind." Ninety percent of the floor beams will be re-used.
The floor system is removed except for the sill beams at each end. All that remains of the roof system are the three tie-beam assemblies which will be removed when the cable bracing on the trusses is completed.
View from the southeast corner (upstream side.)
The upstream truss is rigged for lifting. In the foreground, a landing pad is being prepared.
The upstream truss is released and supported only by the crane.
Upon lifting the truss the sill timber at the west end of the bridge jammed in a notch cut into the arch timbers. A similar notch can bee seen at the east end. The sill timbers were later additions.
Up and away!
The upstream truss is guided to the landing pad.
East chord end with bolster beam.
West chord end. Note rot and powder post beetle damage.
The downstream truss is lifted away.
The downstream truss is positioned at the landing pad. Note the wet rot at the west end bolster beam.
The last knee brace is brought down.
The downstream truss is laid up atop the upstream truss. With the release of dead load, a brace fell out of the truss. Note the splice.
The inside center members of both lower chords will be replaced. The downstream truss member is cross- grained and shows a crack. The corresponding member in the upstream truss shows a long longitudinal crack.
Jeffersonville, June 17, 2004 - Work on the trusses continues while forms are under construction at the east abutment.
Blow and Cote carpenters are carefully removing damaged and stressed members from the trusses and duplicating them in new timber for reinstallation.
According to Jeff Cota, VAOT Resident Engineer at the site, all of the bridge truss members that are to be replaced have been identified, although additional work may be found necessary as the trusses are disassembled.
The following members in the north truss are to be replaced with untreated spruce: both end posts; the diagonals in the end panels at each end; the inside arch member at the east end; the inside top and bottom lower chord-end sections at both ends of the truss; and the inside bottom middle lower chord-section.
The member replacements in the south truss, also with untreated spruce are to be: the end post and diagonal in the east end-panel; the inside and outside arch members at the east end; the inside and outside, top and bottom chord end-sections at the east end; the fourth vertical post from the east end; the center section of the upper chord.
Three roof (tie) beams will be replaced, and the spacing between the floor beams will be changed with six new floor beams. The bolster beams will be replaced. Three vertical posts will be repaired with epoxy 3/8th inch bolts to repair checking. The inside bottom section of the lower chord in the north truss, previously slated for replacement, will be retained.
Meantime work continues on repairs to the north abutment. The stonework will be "rechinked," filling gaps between the stones with smaller stone. Forms are being constructed at the downstream wing-wall.
Blow & Cote carpenters David Morrell and Roland Blais fabricate a new lower chord member, transferring measurements from the original piece.
Work continues on repairs to the north abutment. The stonework will be "rechinked." Forms are being constructed at the downstream wing- wall.
Jeffersonville, July 14, 2004 - The repairs completed, the downstream truss was moved by crane back into position over the Brewster River.
Repairs can now begin on the upstream truss.
Nathan Cote, Blow & Cote foreman, walks the truss checking the lift-rigging.
All is clear; the lift begins.
The truss stands upright, truss members are checked for alignment
Roland Blaise reseats diagonal braces and kick-braces misaligned during lift.
David Morrell and Roland Blaise help guide the suspended truss through the work area.
The truss rises high over the Brewster River. Note the "in kind" replacement members. Most of the original fabric remains in the truss.
The truss is back in position on the abutments, standing on new bed timbers. It will be held in place with steel cables awaiting the second truss.
Roland Blaise releases the mid-span guying cables.
Jeffersonville, July 29, 2004 - With the repairs completed on the south, or downstream truss, and the truss returned to the abutments, work began on the upstream truss.
The plans call for the replacement of both end posts; the diagonals in the end panels at each end; the inside arch member at the east end; the inside top and bottom lower chord-end sections at both ends of the truss; and the inside bottom middle lower chord-section.
Unplanned was the replacement of the kingpost in the third panel from the east end, found to be rotted.
David Morrell and Roland Blais fit the new upper chord section into the truss.
Roland Blais fashions the new kingpost using circular saw, chainsaw and flat chisel
The original kingpost at right was found to be laced with powder-post beetle holes and dry rot.
Roland Blaise displays a piece of the east end chord member destroyed by carpenter ants.
Jeffersonville, August 3, 2004 - Preparations began about 7:30 in the morning. By eleven o'clock, the second truss had been replaced over the Brewster River.
As done with the first truss, an I-beam with slings was prepared to lift the truss by the bottom chords. While the truss is being raised to an upright position, its structure can flex. Because the diagonal braces are held in place by the dead-load of the structure when standing, if the loading is released the braces can move in their seats. To correct this, the truss is raised to an upright position, set on blocks and held there while the braces are driven back into place.
The truss is returned to the abutments and braced to its mate with temporary tie-beams. Next, the floor and roof systems will be put back, followed by new roofing and siding.
Preparing the truss for lifting.
The two "end" floor beams are located where the Burr arch meets the chord, so the arch planks here are ported to receive them; the ports on the second truss need to be threaded onto these two floor beams.
Going up. Notice the flex in the truss.
The truss is set upright on blocks and braced to stand.
Roland Blais drifts the braces into their seats with a mallet called a beadle (pronounced "biddle").
The truss is airborne. Note the new members. Most of the original fabric of the truss is preserved.
The upstream truss is back where the builders had put it some hundred years ago. The first temporary tie beam is in place.
Jeffersonville, August 23, 2004 - The multi-layered bridge roadway is being reassembled using the original design. The 8" x 8" floorbeams removed when the bridge was disassembled have been returned and re-spaced, with six new beams. The existing 6" x 6" stringers were placed on the floorbeams and new 3" x 10" transverse sub-floor planks spaced on these. New 3" x 8" longitudinal deck planks protected by new 3" x 8" oak running planks complete the new floor. The distribution beams (or "hanging beams") installed under the bridge in the 1970s will not be replaced.
The floorbeams have been laid and spaced.
The deck stringers are being laid out atop the floorbeams.
The transverse sub-floor planks have been placed and spaced. The longitudinal deck planks are being lag bolted to the sub-floor.
One of the three roof beams (tie beams) that needed to be renewed. The roof system will be reinstalled next.
Jeffersonville, September 07, 2004 - The last of the tie-beams, x-braces, and ridge pole sections are made ready while the rafters are being installed at the other end of the bridge. The roofers will nailed on over the rafters, hopefully by the end of the week, said foreman Nathan Cote.
Assembling tie-beams and fabricating ridge pole section.
A mortice begun in error on a tie beam by an old-time bridge builder, then plugged. Discovered by Roland Blais.
A pair of cross-beams fabricated from floor beams
The roofing system is nearing completion. The roofers are expected to be installed by Friday, Sept. 10.
Jeffersonville, September 13, 2004 - The Roof system structure is complete and installation of the roofers has begun. It is expected that the installation of steel roof sheathing will begin by Wednesday of this week.
The roof system is complete from tie-beams to rafters.
Installing the roofers.
View of the roof system from the bridge deck.
View of the new roofers from the west end.
Jeffersonville, September 28, 2004 - The Roofing is complete and installation of the siding has begun. It is expected that the installation of steel roof sheathing will begin by Wednesday of this week The new oak running planks are nearly ready for traffic.
A busy place. While the oak running planks are being lag-bolted to the deck, the work party at the far end of the bridge are constructing massive guard rails on the approach road.
A view of the new roof.
The original siding is re-installed on the downstream side. Note the new approach road guard rail.
The re-installed siding viewed from the west end.
Jeffersonville, October 5, 2004 - The last nail driven and the last bolt tightened, the Canyon Bridge stands ready for the Vermont Agency of Transportation inspection team. When the t's are crossed and the i's dotted, the bridge will be officially reopened to traffic.
Canyon Bridge 45-08-01. View from NW.
Canyon Bridge 45-08-01. View from SW.
Canyon Bridge 45-08-01. View from NE.
Canyon Bridge 45-08-01. View from SE.
October 13, 2004 - The barriers were removed last week, opening the renewed bridge to traffic. The final inspection will be conducted during the first week of November. It is expected that no problems will be found.
View from SE.
View from NE.
View of upstream truss from east end.
Interior view from east end.