Architecture Notes
Event ID 844174
Category Descriptive Accounts
Type Architecture Notes
Permalink http://canmore.org.uk/event/844174
Bridge crosses the parishes of Boleskine and Abertarff, Inverness and Kilmonivaig, Lochaber [Incorrect: within parish of Boleskine and Abertraff].
Formally re-opened to pedestrian traffic in September 1997 following refurbishment by the company, Halcrow. The refurbishment took two years, at a capital cost of £280,000, the quoted value of associated 'services' being £40,000. The company described the project in the following 'Technical Description'.
'The Bridge of Oich was designed and built by James Dredge of Bath in 1854 and spans some 46m across the River Oich. The bridge is a suspension bridge in concept using a wrought-iron chain which reduces in cross sectional area from the main support positions to the centre of the bridge by omitting one bar from the chain at each suspension rod position. This bridge concept patented by Dredge in 1836 represents a very significant development. His design resulted in a dramatic reduction in the amount of iron used in the suspension system and shortened significantly the erection time of a bridge deck.
Bridge of Oich is understood to have been open to 'traffic' until construction of the concrete-arch bridge some 80m upstream in 1932. In recent years this Dredge bridge had deteriorated and, at the point of acquisition by the Secretary of State, was one of only seven bridges still standing out of some 30 bridges built by Dredge and recorded by the Institution of Civil Engineers.
Inspection of the bridge included testing of wrought iron, identification of timber species, excavation of ground anchors with archaeologist in attendance, identification of existing paint system, inspection of abutment core by the removal of a masonry block and identification of original mortar composition. Structural assessment indicated that strengthening was necessary and that live load would require to be restricted to 1.0kN/m squared if structural form was to be retained.
Strengthening proposals were developed which are very discrete and conserve the original components and the overall appearance of the bridge.
The contract involved the resolution of safe access over a river subject to flood. It was also necessary to safely remove the existing lead-based paint systems without polluting the environment or endangering the health of operatives. Risks were identified in the Health & Safety plan, prepared by Halcrow H&S Ltd, in accordance with the CDM Regulations.
Consideration was given to future maintenance and relevant considerations are included in the Health & Safety File for future reference.'
Source: Halcrow Project Data Sheet entitled 'Bridge of Oich Refurbishment', issued by the company at the official re-opening of the bridge in September 1997.
