Columbia Covered Bridge

DESCRIPTION:

The Columbia Covered Bridge crosses the Connecticut River between Columbia, New Hampshire and Lemington, Vermont. The low water line on the west (Vermont) side of the river marks the boundary between the states. Most of the bridge, therefore, stands in New Hampshire; only the west end is in Vermont. Owing to its interstate location and ownership, the Columbia Bridge is being nominated concurrently by New Hampshire and Vermont.

Present Physical Appearance

The Columbia Bridge consists of a single span supported by two flanking wood-iron Howe trusses . The principal iron components of the trusses are the paired tension rods which connect the top and bottom chords between adjoining panels of criss-crossed wood compression members. The trusses lack the Howe patent iron angle blocks to accept the ends of the compression members; wood angle blocks serve in their place. Iron tension rods also connect horizontally the top chords and the bottom chords to increase the lateral rigidity of the structure.

The structure rests on abutments built originally for the previous bridge on the site, consisting of irregular stone blocks laid dry. The abutments were faced with concrete during the construction of the present bridge. The current legal load limit posted on the bridge is six tons .

The Columbia Bridge has an overall length of 146 feet and width of 30.5 feet. The roadway is 15.5 feet wide and has an overhead clearance of 13 feet. The floor consists of planks laid flat and parallel to the trusses, overlaid with planks laid flat and diagonal to the trusses for the driving surface.

On the exterior, the trusses (and side walls) of the bridge are sheathed with unpainted matched boards hung vertically. Similar siding protects the ends of the trusses immediately inside the portals. On the north wall, the siding rises only about six feet from the floor, leaving the truss exposed above that height.

The gable ends are also sheathed with unpainted matched boards hung vertically. The boards extend diagonally beyond the line of the side walls to meet the eaves. The portal openings are rectangular except for diagonal upper corners, which are ornamental features.

A steep-pitch gable roof covered the entire bridge, with overhangs both at the eaves and the gables. The roof is sheathed with corrugated metal sheeting.

STATEMENT OF SIGNIFICANCE

Transportation

The Columbia Covered Bridge was built across the Connecticut River between Columbia, New Hampshire and Lemington, Vermont to replace an earlier bridge which was destroyed by fire in 1911. Charles Babbitt completed the Columbia Bridge, which is the third bridge on the site, in 1912.(1) The towns of Columbia and Lemington shared the cost of the interstate bridge, and continue to share the cost of its maintenance. The Columbia Bridge is the only crossing of the Connecticut River between those towns.

Engineering

The Columbia Bridge and another covered bridge (the Mount Orne Bridge) across the Connecticut River about 37 miles to the south at Lancaster, New Hampshire are the only highway bridges remaining in the state of New Hampshire which are supported by Howe trusses. (One other highway bridge of the same type remains in Vermont at Stowe.) The Columbia and Mount Orne bridges, which were completed in successive years (1911-12), are also the last covered bridges built on public highways during the historic period of covered bridge construction in New Hampshire and Vermont, which began about 1820.

The Howe truss, which was introduced about 1840 with its combination of wood and iron structural members, represents the transition from wood to iron bridges. The lower initial cost of the Howe structure compared with that of wholly iron or steel construction undoubtedly accounts for its extraordinarily late use at the two lightly traveled crossings served by the Columbia and Mount Orne bridges.

NOTES:
(1) Thedia Cox Kenyon, New Hampshire's Covered Bridges (Sanbornville, NH: Wake-Brook House, 1966), 93.

MAJOR BIBLIOGRAPHICAL REFERENCES

(1) Allen, Richard Sanders. Covered Bridges of the Northeast. Brattleboro, Vt.: The Stephen Greene Press, 1974.

(2) Congdon, Herbert Wheaton. The Covered Bridge. Middlebury, Vt.: Vermont Books, 1970.

(3) Kenyon, Thedia Cox. New Hampshire's Covered Bridges. Sanbornville, NH: Wake-Brook House, 1966.

FORM PREPARED BY: Hugh H. Henry, Historic Sites Researcher, Vermont Division of Historic Sites, Pavilion Building, Montpelier, VT 05602. Date: 7/3/74.

DATE ENTERED: December 12, 1976.
(Source 127)