V.A.O.T. Historic Bridge Committee
Historic Covered Bridge Committee Notes of July 1, 2002 for:|
COMSTOCK COVERED BRIDGE (NO. 41), MONTGOMERY BHO
Committee members in attendance: J. B. McCarthy, Eric Gilbertson, Nancy Boone, Scott
Newman and Sue Scribner. 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
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
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.