The construction of the six fuel tanks inside Kinrive Hill was a major feat of engineering.
The tanks are enormous and held almost 32 million gallons of fuel. There were five main tanks and one smaller reserve one. The larger tanks were 9m wide by 237m long and 13.5m high; you could fit 16 double decker-buses end to end into one of these tanks.
The government contracted engineering firm William Arrol to build the depot, who in turn sub-contracted the work out, probably to the construction firm Yemen, Bald, and Hutchison.
It was not an easy task to hollow out the hill. Nor could it have been much of a secret. The hill was selected for its hard rock, and was deep enough to protect the tanks from bombing. They quarried over half a million tonnes of rock and dumped it on the hillside. This was visible from the air and the Germans probably knew about the construction.
Locals still remember the quarrying of the hill. As well as a local workforce, gangs of labourers from Ireland were hired.
Malcolm MacLeod recalls his father cycling the five miles and back from Adross to work a fourteen hour shift drilling the tunnels and tanks.
The tanks had no doors, only four circular pipes, through which men had to pass to reach the tanks. The staff lay flat on a gurney, a wheeled board, and slid down the pipes.Today the tanks are clean but it must have been a rather dirty and smelly job.