Site Records

SiteName: Ridge Quarry


Sub Brit site visit September 1999

[Source: Nick McCamley (text) Nick Catford (photographs)]

Ridge Quarry, a small underground Bath-stone quarry at The Ridge near Corsham in Wiltshire was taken over in 1915 for TNT and cordite storage. It was abandoned shortly after the war but subsequently was to figure as a key progenitor of the vast schemes undertaken at Corsham in preparation for the Second World War.

A number of underground sites were examined during 1929 and 1930 with a view to converting them for underground munitions storage. All the sites considered were all found to be gravely deficient regarding either size, safety, means of access, or proximity to nearest services.

By 23 May, 1930 a short list of five possible sites had been drawn up: Chislehurst Caves, slate mines in the vicinity of Blaenau Ffestiniog, Scout Quarry in Rossendale, Meadowbank salt mine in Cheshire, and Ridge Quarry near Corsham. After careful consideration Ridge Quarry was chosen specifically for further investigation as it offered 12 acres of storage space half of which had been cleared and converted by the Ministry of Munitions for explosive storage during the 1914-18 war. A quarry tramway connected the mine with the GWR main line at Corsham station where there was siding accommodation for twenty one trucks in a loading platform specially adapted for ammunition wagons. Two foot gauge track existed in a good part of the workings serving raised stacking platforms, and a steam winding engine capable of lifting six tons was still in place at the top of the main entrance shaft.

Photo:No 1 slope shaft with the only section of narrow gauge track still in place
Photo by Nick Catford

In November 1934 War Office officials returned to Ridge Quarry and nearby Tunnel Quarry for a more thorough inspection. The initial impression was favourable. During subsequent discussions it was agreed that the quarries at Corsham could accommodate filled shell and bulk explosives, the location being well situated to supply the new filling factory under construction near Hereford. Tunnel Quarry offered over forty-five acres of storage space, as opposed to a mere six acres at Ridge, and had the major advantage of being connected directly to the GWR main line by a branch entering a side tunnel at the eastern portal of Box tunnel. Outline Treasury approval was granted for the purchase of both Ridge and Tunnel for 35,000. Later Eastlays and Monkton Farleigh quarries were also purchased.

Conversion of Ridge Quarry posed few problems as virtually all the clearing work had been done by the Ministry of munitions during the first World War. The gross area of the usable part amounted to nine and a half acres of which 3 and a half acres consisted of support pillars, leaving six acres for storage.

Once sufficient manpower had been mobilized, construction began simultaneously at Ridge, Eastlays and Tunnel Quarry in July, 1936. Efforts were made to maintain an air of secrecy about the works there, and by way of subterfuge it was let slip that the Ministry of Food was building an emergency food dump. The need for underground storage had become so great that it was made clear that Ridge Quarry must be ready to receive stocks of explosives by the end of December 1936 and the quarry was brought into commission in a very unfinished state to store ammunition and explosives for the RAF and Ministry of Supply.

The mine had altered little since being vacated by the Ministry of Munitions in 1922, but it still proved necessary to remove a total of 96,000 tons of stone debris to provide sufficient storage space. All the raised stacking areas constructed in the Great War were removed and the floors rolled and levelled. The already comprehensive two foot gauge railway system was extended to serve all the storage bays, and the existing steam winch at the head of the access shaft was overhauled. Because the 1:3 gradient put a considerable load on the winding plant a standby electric hauling engine was installed in case of a breakdown of the primary set.

Plan of Ridge Quarry

At the bottom of the main slope shaft the rails served a primary reception and marshalling area. Nearby an old vertical ventilation shaft was adapted for winding by the installation of a pair of counterbalanced electric lifts running in wooden guides. This was a primitive affair with a poor loading capacity, capable of handling only one third of the throughput of the slope shaft.

Underground, the mine is crossed by a major slip-fault, with the result that one half of the workings is about 20 feet lower than the other. Two sloping haulageways were driven to connect the upper and lower sections; to enable wagons to be drawn up these inclines two steam winches were installed, adapted to operate on compressed air supplied by compressors housed on the surface. Generally, however, loaded trucks were manoeuvred manually throughout the level areas of the quarry.

Some months after stacking had begun a construction programme was initiated, designed to produce a layout of storage areas more regular than the random pattern of existing pillars. It was planned to reinforce the stone pillars by corseting them with concrete, making them rectangular in section with straight haulageways between. Concreting began early in 1938 on fifteen pillars and a length of perimeter wall in the south east corner of the quarry, but this operation was permanently suspended a few months later. The cost of the work and the quantity of materials consumed were much greater than anticipated and were out of proportion with the benefits obtained. The unfinished concrete reinforcing can still be seen in varying degrees of completion in the quarry today and illustrates the constructional techniques used in the larger and more sophisticated of the Corsham depots.

Photo:New incline to lower level
Photo by Nick Catford

A second slope shaft, the steeply graded West Ridge incline, was reopened on 12 February 1942, to improve access to the lower level of the mine and provide space for a further 1,500 tons of bombs. The underground access tunnel linking this shaft to the new storage bays passed through an area of treacherous roof formation that required substantial support to ensure safety.

Unlike the three other quarries that comprised the Corsham CAD, Ridge was never reclassified as permanent storage, and no further development was done underground after 1942. Surface buildings at Ridge were minimal. In line with War Office practice the first buildings to be erected were twenty seven wooden huts to house military police personnel, built in two groups on open land between the quarry shafts and the lane to Corsham. The vertical lift shaft with its associated winding gear and compressor house was immediately between the two groups of police huts. The No.2 loading bay was the most substantial and is the only major building still surviving.

Although War Office property, Ridge quarry was allocated to the RAF in November 1936 for the storage of bombs and bulk explosives. It was designated a sub unit of the Altrincham small-arms depot.

Photo:Winch house at the top of No. 1 incline to the lower level
Photo by Nick Catford

Stacking and loading of bombs was carried out by a team of thirty civilian gangers, employed by the RAOC but under direct control of the RAF. The total capacity of Ridge Quarry was 13,000 tons, of which the RAF at first required about 5,000 tons to store 500 lb and 250 lb General Purpose (GP) bombs. By the outbreak of war RAF stocks at Ridge had expanded to 11,569 tons, including 4,000 tons of bulk TNT. At that time the RAOC retained a small area to store 2,000 tons of bulk explosive for Army use.

During the early months of the war Ridge Quarry was used as a temporary holding point for bulk explosives and as a long term store for obsolete GP bombs returned from various active airfields via the Pulham depot.

Further information and pictures about this site continues here

[Source: Nick McCamley (text) Nick Catford (photographs)]

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