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V.A.O.T. Historic Bridge Committee Proceedings

Historic Covered Bridge Committee Notes of July 1, 2002 for:

COMSTOCK COVERED BRIDGE (NO. 41), MONTGOMERY BHO 1448(26)

Committee members in attendance:

Joe Nelson, representing the Vermont Covered Bridge Society, was also in attendance.

The purpose of this meeting was to discuss the engineering study results for the Comstock Covered Bridge prepared by HTA Consulting Engineers.

This bridge has been discussed in the past as the ideal candidate for rehabilitation with a limited load posting requirement as there is another bridge within sight, resulting in only a one-half mile detour for heavier vehicles. The Committee had discussed this with representatives of the town in May 2000 at an earlier site visit. The town has recently stated, however, that they feel a load capacity of 20 ton is needed. It is anticipated that meeting this requirement will require significant replacement and changes to the bridge. Therefore, the Committee requests that this topic be further discussed with the town. The engineering study report was therefore discussed with the assumption that a higher load capacity than discussed in the report will not be necessary.

UPDATE BY WARREN TRIPP: The town has agreed to a 6 ton load posting which is great news.

Hydraulics: The Committee agrees that raising the bridge approaches five feet to elevate it above the 100 year flood level does not appear to be very viable. HTA Consulting Engineers recommended raising the bridge two feet, which would not require significant changes to the substructure nor the need to acquire right of way. While this would not raise the bridge to the 100-year flood level, it would afford some additional clearance. There was evidence of flooding at the May 2000 site visit to the surrounding area, but it appeared that there were ample areas in which to divert the flooding waters. Therefore, it was felt that further investigation by Hydraulics would be beneficial to determine if there would be any gains realized by raising the approaches two feet as recommended by HTA Consulting Engineers. In addition, the estimated cost of $70,000 was questioned as appearing to be quite high. Warren Tripp reports that the town is not in favor of this and if it were to be included in the project, it would be difficult to meet the project schedule required by the National Historic Covered Bridge Preservation Program.

Roof Framing: It was questioned whether the addition of lag screws at each rafter bearing is necessary. Warren Tripp reports that he feels that they should be used to add needed additional strength. It is expected that some rafters and purlins will need to be replaced as well as the roof with a new standing seam metal roof. No objections were raised by the Committee.

NOTE: The Town of Montgomery has requested green standing seam metal roofs for two others bridges that will see their roofs replaced this summer.

Lateral Bracing: The Committee was in favor of the recommendations presented in this section of the report which would include some replacement of the upper lateral bracing with sawn lumber to match the original dimensions and construction, new lower lateral bracing and addition of a through bolt and ogee washer at the intersection of the lateral bracing.

Trusses: the Committee questioned whether it is proposed that some lattice members be replaced only because they contain checks or if they were other reasons. No objections were raised towards replacing them if it is determined to be truly necessary. As well, there were no objections to replacing portions of the top chords as presented, only the comment that perhaps the areas shown to be spliced directly in line with each other on the south truss upper chords be replaced all the way to the end.

Floor Beams and Decking: The Committee supports removing the distribution beams referred to as longitudinal stringers. Installation of a new plank deck was received favorably. The Committee questioned whether there needs to be a change in the floor beam size and spacing. It was suggested that the structure be examined more closely in order to hopefully glean how the original floor system was constructed.

Abutments, Bridge Approaches, Fire Detection/ Protection, Lighting: No specific comments relative to any of these sections with the exception that some felt some sort of fire retardant system such as the use of a fire retardant paint should be required.

The Committee was in general agreement with the remainder of the items discussed in the estimate section with one exception. Nancy Boone requested that siding be salvaged for re-use if at all possible although it was acknowledged that this is often difficult as it is often damaged when it is being removed.

Warren Tripp will share the content of these minutes with HTA Consulting Engineers and progress will continue on development of the project plans.

Respectfully submitted,
Susan Scribner

[This article was originally posted July 3, 2002]