Project profile: Bonnington Overbridge

The Scottish Category B listed cast-iron bridge is getting some attention as part of our major work programme.

Location: Lanark, South Lanarkshire

Contractor: Balfour Beatty

Open to the public? Yes

Completion: Autumn 2024

History

The overbridge, which formed part of the Douglas and Muirkirk extension line, fully opened in 1874. The route closed to all traffic in 1964. It has strong historical interest as part of the former Lanark to Muirkirk Railway. The bridge remains in a moderate unaltered condition, contributing substantial evidential value to the bridge’s enduring structure. Additionally, it continues to serve its initial purpose as a functional road bridge, thereby holding communal value.

The earliest part of this railway was constructed by the Lanark Railway Line; however, the Caledonian Railway took control of it in 1885.

About the structure

This category B listed bridge is a good unaltered example of a cast-iron arch railway bridge. Constructed in the 1870s this skewered cast-iron bridge contains solid cast-iron plate parapets and massive stone abutments, wingwalls and parapets. The bridge carries the main access roadway from the Hyndford Road (A73) into the Bonnington Estate.

What is the project?

We’re investing a significant amount to repoint and repair the parapets, jack arches and abutment masonry. This project involves removing light vegetation, straightening the warped west parapet, installing trief kerbs and re-surfacing the areas in between. Additionally, we'll enhance and clean all visible metallic elements of the girders and parapets. The process includes painting prepared girders, tie bars and parapets. We also plan to rake out and re-mortar all open joints within the jack arches, as well as replace any missing bricks and re-bed any loose bricks.

What stage is it at?

Works began in January 2024 and are currently in progress.