1938-1943. Extensive network of 6 rectangular underground fuel storage reservoir tanks with operational and maintenance access tunnels, valve chambers carved out of the hillside bedrock and predominantly lined in shuttered concrete. At the head of the operational piping tunnel is a small square-plan fan room, and at the end are 6 underground fuel tanks. The tunnel is approximately 350 metres long by 3 metres wide. The tunnel has two pipes laid underneath the concrete floor and accessed by metal inspection covers, connecting each underground reservoir to the tank farm in Invergordon. The reservoir tanks, each with valve chamber to control the flow of oil, are of variable dimensions due to the geology of Inchindown however generally they are 9 metres wide by 237 metres long and 13.5 metres high, with a capacity of approximately 5.6 million gallons of fuel.
Statement of Special Interest
The underground fuel reservoir complex set in the hill at Inchindown farm near Invergordon was constructed for the Royal Navy between 1938 and 1943 as part of a national programme to protect the Royal Navy fuel depots from aerial attack. It is a monumental and complex engineering achievement and a rare example of an intact underground fuel storage facility constructed to high specifications and engineering standards. It contains rare surviving and largely unaltered machinery, and forms part of a wider group with other military buildings associated with the First and Second World War in the area.
Built to service the Home Fleet and other Allied naval fleet vessels, underground fuel storage reservoirs played an integral role in the UK's Second World War defence strategy. This example at Inchindown is one of two surviving in Scotland and it remains largely in its original form and condition. The ability to store large amounts of fuel required pioneering engineering skills.
In the early 20th century the Royal Navy used coal to power their fleet. By the beginning of the First World War the Navy were beginning to adopt the use of furnace fuel oil (a heavy and thick crude oil) and this necessitated new facilities to be constructed to store the fuel at all major Admiralty naval bases in the UK. The fuel required purpose built tanks in large depots, onshore equipment, pump houses and power sources. By the Second World War, the Admiralty recognised the threat of possible enemy aerial attack to these fuel depots, therefore they commissioned the construction of several underground oil storage reservoirs across the UK to store oil securely in order to be prepared in the event of an aerial attack.
Reservoirs were constructed in the UK to designs by the Civil Engineer in Chief's Department, varying in size depending on the naval base they were serving. In Scotland three reservoirs were constructed and they were located near the major naval bases of Rosyth, Inchindown near Invergordon and Lyness in Orkney with some variation in design to account for geology of the sites chosen.
The immense scale of the engineering project for the construction of the reservoir, rare in itself, is a monument to British military engineering. Along with the construction of the afore mentioned reservoirs in Scotland, it was the largest construction in the north of Scotland since the Caledonian Canal; and the largest underground excavation in the UK before the construction of the Ben Cruachan hydro-electric scheme, completed in 1965 (see separate listing). It was constructed to the highest engineering standards, requiring an extraordinary degree of skilled labourers and the use of building resources, all of which were scarce in wartime. The excavated rock formed a spoil heap to the south west of the complex.
Invergordon, along the Cromarty Firth, was adopted as a naval anchorage in 1913 when Winston Churchill, then the First Lord of the Admiralty, successfully campaigned for fixed defences there. The Royal Navy base was soon established and with the arrival of furnace fuel oil the Navy constructed two large tank farms Seabanks and Cromlet before, during and after the First World War, to contain the fuel for the base. The Admiralty used Invergordon as one of 3 main naval bases in Scotland during the Second World War and the latter half of the 20th century.
The reservoirs remained in use until the fuel depot was decommissioned in the 1990s.