Monument record MHG34946 - ALLT A'CHAISE BURN BRIDGE

A mid-late C18 single arch bridge spanning the Allt a' Chaise Burn near Achlain on a stretch of the military road between Fort Augustus and Fort William.

This bridge over the Allt a' Chaise Burn is of military construction and in reasonably good condition. It is 4.2m wide with a span of 4.8m. Visited by OS April 1979.

The bridge was visited by M Logie of Historic Scotland in 1997 during a project involving a rapid assessment of the state of the military roads and associated features within the boundaries of the Highland Council area. This bridge was noted as being a single span stone culvert/bridge, 4.8m wide and in a reasonably good state of perservation. <1>

The bridge was included in the scheduling of this particular stretch of military road by Historic Scotland in 2007.

The bridge was included in a survey in 2009 by Forestry Commission Scotland of C18 military roads under their ownership within their Highlands estate and within the districts of Inverness, Ross and Skye, Lochaber and the North Highland Forest in order to enable it to develop sustainable management strategies. <2>

AOC Archaeology Group was commissioned by Forestry Commission Scotland in 2011 to undertake a Structural Costed Conservation Plan for the Achlain Bridges, Fort Augustus, in line with their aspirations to conserve the bridges as a heritage asset through repair and maintenance as necessary. The three bridges date to the mid-C18 and form part of the military road constructed between Fort Augustus and Bernera by Major Caulfeild, the successor to General Wade, in response to the Jacobite uprisings. The plan incorporated an assessment of the significance of the bridges, an assessment of its current condition and conservation requirements and the identification of the long-term needs to maintain them. Archaeological recording of the bridge (designated bridge 009) included a detailed measured survey, a 3D Laser scan, a general and detailed photographic record and a detailed written record. Bridge 009 to the west is the largest of the bridges and is set on the steepest burn with abutments to the east and west, with a deep face to the north and a much smaller face to the south, which is more difficult to access. Being the largest bridge, it also appears to be the one in the best condition. It is constructed of sandstone with stone slate pinnings and with ladder pinnings to the walls and forms a relatively large segmental arch over a low abutment wall with an additional wall to the east of the north face which is angled to the northeast and takes in the angle over the road. <3>

Ross and Cromarty Archaeological Services were commissioned by Forestry Commission Scotland to undertake a programme of recording and excavation in advance of conservation of three military bridges located by Achlain in Invermoriston during the second half of 2012. One small trench was excavated on Bridge 009 to identify a possible structural weakness of the bridge at the request of the conservation architect prior to conservation. The excavation allowed for recording of the bridge prior to any changes made by conservation work to the structures. <1>