Tunnel Quarry also known as Seven Shaft Quarry, Yockney and Hartham Park Stone Co. Corsham Down Quarry and Pockeridge Quarry. It had slope shafts, travelling and surface cranes. It was opened prior to 1845 by Randell, Saunders and Co. and the original entrance is on the northern side of the eastern end of Box Tunnel. Due to the location, the stone was loaded directly onto the rail trucks so there was no need for tramroads to the railway from here although tramways were used inside the quarry, a railway siding was extended to Corsham station in 1877. Tunnel Quarry was exhausted by 1900 having joined with several surrounding quarries and totalling 1,630,000 sq ft. it was leased by the Bath and Portland Stone Firms to the Agaric Mushroom Co. for the cultivation of mushrooms underground. At the peak they produced 20 tons of mushrooms per week In 1928 they moved their operation to Godwin’s Quarry in Westwood due to a fungal infection in the mushroom beds. After the quarry had been abandonned a die press and counterfeit half crown coins was found in the old mushroom area, three people were arrested, found guilty and imprisonned for counterfeiting in 1937.
Tunnel Quarry was identified as an ideal location for the main depot of the Central Ammunition Depot due to it’s size and railway connection next to Box Tunnel, It was purchased by the War Office in 1934 with other depots spread across the wider area at Monkton Farleigh, and Eastlays near Gastard. Work started in 1936 to remove two million tons of stone debris and convert the abandonned quarries into the largest ammunition depot in the world. The three depots had a total capacity to store 350,000 tons of ammunition, Tunnel Quarry had a net storage area of 40 acres. The only useable entrance into the quarry in 1936 was the tunnel entrance next to the main railway line hence the name of this quarry at this time. The Royal Engineers later constructed their own entrances from the surface to be used in the event of the main line railway being bombed or put out of action. This was the MSLP – main surface loading platform where four slope shafts terminated in one building, the others being sunk at the appropriate angle and incline to terminate in separate 5 acre ‘districts’ underground completed in the summer of 1942. A half mile long double platform railway terminus was built running east-west parallel with Box Tunnel designed to handle 2000 tons of ammunition per day with two vertical lifts connecting with the MSLP above, the project took 6 years to complete and cost a total over £4.4m – forty times the original estimate.
The RAOC vacated the site in 1962 and the Royal Engineers who looked after the infrastucture left in 1966. The majority of the site including the underground railway station and power station have been left to decay since.
Tunnel Quarry is now classed as a Scheduled Monument by Historic England
Tunnel Quarry Media
