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Summary

Description

Probably James Williamson and Partners (engineers for North of Scotland Hydro Electric Board technical panel), 1961. Long mass gravity dam with large central buttress incorporating fish pass, with access roadway oversailing fixed spillway on tapered concrete piers. Mass concrete construction to dam with some reinforced concrete to central buttress and control towers. Battered downstream face with large angled buttress to centre flanked by tall square-plan control towers springing from downstream face. Dispersal valves and fish pass entrance to base of buttress with small single storey turbine hall housing compensation set. Additional small control tower to centre of buttress at roadway level.

Statement of Special Interest

Orrin Dam is a large scale mass gravity dam, dominating the upper reaches of Glen Orrin and providing storage capacity and flow regulation for Orrin Power Station which forms part of the Conon Valley hydro electric scheme, one of the major post-war hydro electric developments by the North of Scotland Hydro Electric Board (NoSHEB). The dam is an important architectural landmark, closing off the upper reaches of Glen Orrin with a large curtain wall of concrete. It is integrated into the bedrock giving the appearance of the dam having thrust up through the surrounding earth. The dam has a particularly innovative fish pass contained by the central buttress and designed to accommodate the frequent large changes in water level. The buttress contains four parallel chambers which can all be entered from the fish-pass intake located at the base of the buttress. Each chamber discharges into the dam at a different height on the upstream face so that whatever the water level fish are able to bypass the dam using the appropriate chamber.

Conon Valley was one of a large number of schemes developed in Scotland by the North of Scotland Hydro Electric Board (NoSHEB), formed after 1943 as a nationalised body to oversee the development of Scotland's resources for water power. The scheme played a key role in the realisation of the social agenda of NoSHEB by providing power to a remote community. Power generated on schemes in the southern Highlands, such as Tummel (see separate listings) was exported via the grid to the central belt, the profit from which subsidised the provision of power to remote north highland communities and stimulated economic regeneration. Under the leadership of eminent chairman Sir Tom Johnston the board undertook developments throughout highland Scotland and his aspirations saw the development of schemes in locations such as Loch Dubh near Ullapool and Storr Lochs on Skye. Johnstone's social aspirations and wider wishes to reinvigorate the economy of the Highlands ensured that schemes in remote areas formed a key part of the NoSHEB development plan.

All of the developments carried out by NoSHEB were subject to parliamentary approval and objections on the grounds of scenic amenity were common. In order to meet these objections the board appointed a panel of architectural advisers which included Reginald Fairlie (1883-1952), James Shearer (1881-1962) and Harold Ogle Tarbolton (1869-1947), appointed in 1943. Initially the role of the panel was to adjudicate on competition entries for designs, but by 1947 it had become one of designers. The panel had little control over the functional form of the buildings, as they left this to engineers, but they did influence the appearance and the style of the designs. The rigid views on the roles of engineers and architects during the design process resulted in the development of a style which can be characterised as vernacular modernism. This style is characteristic of many NoSHEB buildings and is a direct product of the strict role which engineers and architects played in the design process and of the increasing desire to harmonise buildings with the landscape.

The design of Orrin Dam is typical of Williamson and Partners approach, with an innovative solution designed specifically to suit the requirements of a particular site. Their design of the fish pass allowed for the large fluctuations in water level which characterised the hydrology of the site. The accommodation of the fish pass in the central buttress allows for the design of the dam to remain free from multiple pipes which would have broken the clean lines of the design. Williamson was a prominent engineer who specialised in the design of dams following his work on the Galloway Hydro Electric scheme (see separate listings) in the 1930s. He acted as one of the chief engineering advisors to NoSHEB and was the lead engineer for a number of schemes. Following his death in 1953 Williamson and Partners continued in the role as engineering advisors to NoSHEB building on the expertise developed during their long association with the development of hydro power.

(Listed 2011 as part of Hydroelectric Power Thematic Survey)

References

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