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VAOT Historic Bridge Committee

Historic Covered Bridge Committee Notes of Field Assessment on May 6, 2001 for:

CAMBRIDGE GRIST MILL (CANYON) BRIDGE

Met with representatives from the Town of Cambridge, a representative of the Vermont Covered Bridge Society and Tim Grant of McFarland-Johnson, Inc., consultant for VTrans. Committee members in attendance were: Bob McCullough, Sue Scribner, Nancy Boone, Eric Gilbertson and Scott Gurley (for Scott Newman). Also in attendance was Gary Rogers, Structures Project Manager.

The Town's concerns focused on the need to safely transport cars and light trucks; they indicated they would be willing to post the bridge for 6,000 lbs. Mr. Grant provided a "List of Damaged Items" with recommended actions as well as plan views of the structure. In general, it was recommended that members either be repaired or replaced in kind. He also provided a "tour" of the bridge, pointing out many of the damaged items. In addition to the list provided, Mr. Grant recommended that the deck be replaced and the approaches paved. Mr. Grant's structural analysis led him to conclude that the bridge is only capable of carrying 5,000 lbs., controlled by the bottom chord. The Town requested the anticipated time frame for rehabilitation; Mr. Rogers indicated that current plans are for the project to be bid for the 2003-construction season. The Town expressed concern that some interim repairs might be needed. It was agreed that Mr. Grant would prepare a listing of the items that he feels are necessary to be repaired in the interim; he will forward this to Mr. Rogers who will forward it to the Town.

Overall, the committee was impressed with the current condition of the structure. Its recommended preservation treatment is Category A - Special Use on Roads and recommended treatments fell within Treatments 1 and 2 of the draft Preservation Plan. Several committee members expressed skepticism with the results of the structural analysis; the bridge has been carrying higher loads and shows very little evidence of distress. There was agreement that the "List of Damaged Items" and recommended actions appear reasonable with the exception that several members did not feel that the east abutment requires addition of mortar, rather it was recommended that a stone mason re-chink the abutment. Mr. Rogers requested that Mr. Grant reevaluate the lower inside (downstream) bottom chord at its mid-span (5' vertical). Some committee members also indicated that they did not feel it would be necessary to pave the approaches as it was felt that a substantial distance would need to be paved to be effective and prevent debris from being tracked onto the structure. Finally, it is recommended that steel-backed timber guardrail be used on the approaches.

McFARLAND-JOHNSON, INC. Concord Center JOB: CAMBRIDGE 15491.05 SHEET NO.:
10 Ferry Street, Unit 11 Suite 210 BY: TLGrant DATE: 06/04/2001
Concord, New Hampshire 03301 CHECKED DATE

LIST OF DAMAGED ITEMS

ITEM PROBLEM RECOMMENDED ACTION
missing fl beam bearing blocks missing replace
arch end at abut #1, upstream not bearing fix
4th stringer, 6' past midspan rotten replace
vertical scarf bolt loose tighten
3rd stringer @ 13th fl beam rotten replace
7th vertical from Abut 2 powder post
U-bolt at Abut #2, upstream loose tighten
5th diag. from Abut, upstream damaged replace
knee braces wrong replace
roof "tie" beam near center rotten replace
last diag. l Abut 2, downstream rotten replace
ROOF rusted replace with enameled standing seam metal
EAST ABUTMENT voids & broken patch, fill, rebuild
APPROACH ROADWAY rutted pave 25'
APPROACH RAIL broken install new beam guard rail

Remove Hanging Beams
Apply CRESTLINE fire resistant paint to interior framing

[This article was originally posted February 13, 20012]

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