Monument record MHG55805 - C20 bridge - Allt Lagain Bhain, Dundreggan, Glenmoriston

A bridge probably dating to the early C20 over the Allt Lagain Bhain near Dundreggan, Glenmoriston, was subject to condition assessment in 2012 by CFA Archaeology prior to proposed demolition.

The site comprised two bridges: a road bridge currently in use on the A887 and an older, disused bridge which lies immediately to its north (see MHG55804). The main Allt Lagain Bhain Bridge has a history of frequent accident damage to the parapet, and has been propped since 2001. The older bridge is in overall poor condition. Proposed culvert works will involve the demolition of both bridges.

The New Bridge is a simple truss bridge, currently in use as a road bridge on the A887. It is aligned east to west and comprises a deck with north and south parapets, east and west abutments, a retaining wall, a paved overflow race and recent reinforcements.

The deck measures 11.5m long by 6.5m wide and is surfaced with tarmac. It is bounded on its north and south sides by parapets which measure 11.5m long and are 0.9m high above the road surface. On both elevations the parapets are 1.1m to 1.3m high. They are built of roughhewn local schist and have been extensively repaired. They are capped with curved coping stones and are bonded and pointed with cement. Both parapets have been extended at each end. The main central parapets are 6.5m long and have been extended for 2.5m at each end. The extensions are indistinguishable in build style and material, and are butted against the cheek-ends of the central parapets. The south-facing elevation of the north parapet has an Ordnance Survey benchmark on a flush bracket (No. G4534). The G-series flush brackets appeared at the beginning of the Second Geodetic Levelling of Scotland in 1936; however, this particular flush bracket is associated with the Third Geodetic Levelling on the Glen Cluanie to Glen Moriston levelling line G358, dating to 1956-68. Both abutments are built into their respective stream banks and act as retaining walls. They measure c. 8.25m long by 0.8m thick and 1.4m high and are built from random coursed schist and basalt blocks with regular string courses. They abut the side of the old bridge at the north side. <1>

A Level 3 building survey was carried out by CFA archaeology in January 2013 prior to the demolishment of the bridge in order to install a box culvert. <2>