Royal Navy Propellant Factory , Caerwent The Royal Navy Propellant Factory , Caerwent , Monmouthshire , UK , ( later RAF Caerwent ) was dedicated to the manufacture of explosives or the storage of ammunition from 1939 to 1993 . It is a large military site and is situated north of the A48 road four miles ( 6 km ) west of Chepstow and east of Newport . Since 1993 it has been used for a variety of military and civil purposes , including field exercises , car rallying , storage and breakdown of railway vehicles , nature preservation , and playing Airsoft . The site has its own standard gauge railway system ( linked to the national network ) , many private roads and a wide range of buildings , from small earth - banked stores to large four storey lightly built brick buildings . It is about two miles ( 3 km ) east - west , and north - south . The perimeter road inside the security fence is , on its own , over seven miles ( 11 km ) long . 1939 to 1965 . The site was created as a Royal Navy propellants factory in 1939 . Note : The Royal Navy Propellant Factory , Caerwent , like the Royal Navy Cordite Factory , Holton Heath , were never part of the Ministry of Supply / Royal Ordnance Factory management chain ; they were controlled by the Admiralty . However , they were functionally very similar to Explosive ROF s . In the summer of 1936 the site requirements for a new factory were drawn up . The main priorities were : Like all explosive factories of this type , a capacious supply of water was required for use in the manufacturing processes . To manufacture 150 tons of cordite per week the factory would need 3 million imperial gallons ( 14 , 000 m³ ) of drinking quality water per day . In the final quarter of 19th century , the Great Western Railway ( GWR ) had undertaken the engineering feat of constructing the Severn Tunnel under the River Severn . One of the major difficulties encountered underground was the ' Great Spring ' , which necessitated the pumping of over 9 million gallons ( 41 , 000 m³ ) of water per day , at Sudbrook , from the western end of the tunnel , conveniently located only three miles ( 5 km ) away from the proposed site at Caerwent . Even during the great drought of 1934 the lowest daily return was 9 . 1 million imperial gallons ( 41 , 000 m³ ) . The GWR used about 1 . 5 million imperial gallons ( 6 , 800 m³ ) per day themselves , so there was always a guaranteed daily surplus of 7 . 5 million imperial gallons ( 34 , 000 m³ ) . The total area acquired was of land , a total of were enclosed within the factory fence . It was connected to the Great Western railway at Caldicot Junction , near Sudbrook by way of a private branch line , sometimes known as the MoD Caerwent sidings ; and a number of transfer sidings were laid out inside the factory fence . The site consumed the village of Dinham which was located at the northern edge of the RNPF Caerwent . By the end of 1940 the Main Office block was complete , and in December of that year the Unit 1 Sulphuric Acid Factory went into production with acid mixing for the Nitrocellulose and Nitroglycerine manufacturing . Five months later , the Pressure Oxidation Plant for the manufacture of Nitric acid came on stream . In August 1941 the Nitrocellulose and Nitroglycerine plants were operational and were soon working 24 hours a day on a three - shift pattern . At the same time , Unit 2 of the factory was almost completed , so RNPF Caerwent was now virtually operational . A total of £4 . 7 million was spent on buildings and roads , and £2 . 5 million on plant and equipment . Early in the 1960s a Parliamentary working party recommended that propellants for the three branches of the armed services should be concentrated at the Royal Ordnance Factory at Bishopton . The decision to close RNPF Caerwent was announced on 25 March 1965 . Production continued during the following two - year rundown phase . RAF Caerwent - weapons storage 1967 - 1993 . RAF Caerwent was transferred to US administration after Charles de Gaulle expelled the US military from France in 1967 . Caerwent thus became part of the US Army European ' theatre reserve stocks ' under the command of the United States Army ' s " 47th Area Support Group Reserve Storage Activity " , and became known as USADA Caerwent ( United States Arms Depot Activity - Caerwent ) with an Royal Air Force Liaison Party also present . The US Army spent over £4 million constructing 300 magazines and converting some of the former RNPF structures to conform to the required specification . The material stored included small arms ammunition , artillery shells ( up to 8 " ) , anti - tank mine s , grenades , flares , and the multiple launch rocket system . The first shipments of shells , rockets , mines , flares and small arms ammo arrived early in 1968 with shipments arriving in lorry convoys as well as rail . The majority of lorry convoys took place at night not to cause local road disruption , along with the freight trains , as they had to fit with BR timetables . Maintenance facilities were added in 1971 . In the early 1970s the site ' s capacity was expanded substantially , which allowed the closure of three other munitions bases in the West Midlands ( Bramshall , Ditton Priors and RAF Fauld ) in 1973 . One of the reasons Caerwent was retained was its proximity to Barry Docks where many of the armaments entered the United Kingdom . At this time there was also an increase of US army staff , with many of them stationed at Caerwent for a short period of time after serving in Germany and prior to returning home stateside . There were also parties , film shows in the on - site cinema and barbecues were held for the families of local people to show them appreciation for working with the US army . At its height Caerwent was among the larger ammunition supply depots in Western Europe , storing over 80 , 000 tonnes of conventional munitions , a substantial fraction of the US Army ' s European stocks . In 1990 Caerwent shipped 12 , 000 tons of ammunition to the Middle East and played a critical part in Operation Desert Shield and Desert Storm . Following the change in the political climate in Europe and subsequent scaling down of operations , the US Army announced it was to close down their storage operations at the establishment in June 1992 . Over 60 , 000 tonnes of munitions were moved out over a period of less than ten months . The last batch was removed by train on 19 July 1993 . The formal closure ceremony took place on 20 August 1993 . Present day . The base is now maintained by a small army staff as a ' Training Area ' for troops from Beachley Barracks and further afield . A ' representative sample ' of the bomb storage and processing structures of this vast site can now be seen on the latest Ordnance Survey map showing roughly 200 structures . Previous editions showed the site as completely blank , but serviced by a railway line . Caerwent is now a major training area covering over , capable of sustaining up to 1 , 000 troops . There are not only over 400 buildings and bunker s on the site , but also an operating railway and a comprehensive road system , for logistics exercises and driver training . The site has been used for military training and public order training by various police forces . Local farmers are allowed to graze their livestock on the convenient areas of pasture that separate the former factory buildings . Parts of the site have also been let for civilian usage , including driver training and car rallying run by Forresters Car Club and South Wales Automobile Club . Part of the site is also used by an airsoft club , under the name Dragon Valley The relay races of the 2007 JK Orienteering Festival were held on the site . Since the privatisation of British Rail , RNPF Caerwent like a number of other MOD sites with internal railway sidings , has been used as a secure storage area for holding surplus locomotives and rolling stock that might be returned to use . A small number of electric locomotives , particularly in the British Rail Class 86 and British Rail Class 87 , have been scrapped at RNPF Caerwent ; also , British Rail Mark 2 carriages . Scenes from two episodes of science fiction television series " Torchwood " were also filmed on the base , as were scenes in the 2006 film " Big Nothing " , starring David Schwimmer and Simon Pegg . Scenes from the Hollywood blockbuster " " were filmed on site in October 2010 . In 1995 the site was also used for a programme in the Scrapheap Challenge series utilising the railway scrap yard facilities to create electric , . diesel and steam powered railway locomotices