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02 Dec 2008, Time:01:18

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Reconstruction of Tannery Bridge, Downton

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Tannery Bridge in the parish of Downton carries the B3080 over the course of the Hampshire River Avon, formerly used as a Mill Race. The bridge is positioned on a historical river crossing point dating back to the 11^th century, although little is known about previous structures.

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The current bridge has 11 spans and is unusual because it has a trapezoidal area of land between spans 4 and 5 which gives access to The Waterside Mill and The Corn Mill.

The bridge deck was constructed in reinforced concrete circa 1944. The piers are of brickwork with rubble infill, 9 feet clear span and are not perpendicular to the highway, but skewed 45° on the eastern side and 12° on the western side. The foundations are of an unknown form.

A footbridge was added to the structure in 1996, on the upstream side, which replaced a very corroded cantilevered footway.

The capacity of Tannery Bridge was assessed in 1991 and although some defects were recorded it was found to be adequate. However the bridge continued to be inspected as part of the regular inspection regime undertaken by the County Council on all the highway structures in the county. A recent inspection confirmed continuing deterioration and a range of defects affecting every span, the main ones being:-

Concrete spalling from the underside of the deck exposing corroded steel reinforcement.
Vertical cracking in the brick piers.
Longitudinal cracking in the highway.
The edge beam being in poor condition and not adequately connected to the deck.

The bridge exhibits a range of defects consistent with a structure reaching the end of its serviceable life!

The structure will be demolished and reconstructed, in stages, between March and October 2007. A temporary vehicle bridge will be erected above the existing structure which will then be demolished underneath. A 7.5 tonne weight restriction will be implemented throughout the works with exemptions for the emergency services, buses and refuse collections. A diversion route will be signed for vehicles exceeding 7.5 tonnes. A temporary footbridge will be installed to allow pedestrians through the site.

The River Avon is a Site of Special Scientific Interest and a Special Area of Conservation. To protect the wildlife and the environment various measures will be put into place including fencing to discourage birds from nesting on the river banks, monitoring to ensure that bats are not roosting and that any potential sites are sealed, and surveillance of an otter and her pup using a highway drainage pipe as a holt.