Monument record TQ 77 NE 37 - Explosive stores, St. Mary's Marshes, St. Mary Hoo

On marshes, South of river wall. Seven rectangular storage buildings. (represented by multiple polygons) (1) Photographs (2-7). Site identified during 2002 survey. Monument consists of seven concrete built structures. Each structure is at least partially surrounded by a bund and a door lintel only surviving in one structure. All structures seem to be contemporary with no evidence of earlier structures (8).

This feature is recorded in the English Heritage Historic Area Assessment for the St Mary Hoo Parish. The report states: "Little other industrial activity was occurring in the parish until the Thames Storage (Explosives) Company negotiated the lease of some land on St Mary's Marshes in 1891-92 for a gunpowder repacking station at St Mary's Marshes. The explosives were transported by river and the benefits of an isolated location were demonstrated when one of the seven magazines was destroyed in an explosion on the 29th July 1905. The site seems to have ceased operation soon after…Non agricultural sites on the marshes include the remains of the short-lived Thames Storage (Explosives) Company site built in 1890s and 1900s. This was located east of St Mary's Bay and served by its own landing stage. Seven roofless mass-concrete magazines sill stand, possibly including the replacement of the magazine destroyed by an explosion in 1905". (9)

This feature was the subject of English Heritage Research Report 52-2013, when it was studied as part of the wider Hoo Peninsula Historic Landscape Project (10). From the report: "Magazines were constructed on the marshes around 1892 by the Thames Storage (Explosives) Company for the packing, repacking and storage of explosives, as a commercial venture on land leased from the Dean and Chapter of Rochester Cathedral… Documentary evidence suggests that the Thames Storage (Explosives) Company went into liquidation in 1907 but the magazines possibly had a second life as a 'Government magazine', eventually going out of use in 1913, when the lease on the land also expired. Seven magazines survive in a ruinous state, some with protective earth bunds, and appear to be an unusual use of mass concrete in an explosives storage context".

A late 19th century explosives store can be seen on aerial photographs taken in 1947. This remote site is situated within two fields near the coast on St. Mary's Marshes and is centred on TQ 7989 7895. It consists of seven concrete built structures, each within an earthwork embankment. Based on map evidence, construction of this site commenced after 1895 and the first five buildings and associated embankments were in place 1897. The three most northerly buildings are at the southern end of a field in the marshes backing onto a drainage channel. They are at TQ 7981 7902, TQ 7989 78903 and TQ 7996 7903. In the field to the south are two more buildings and embankments of the same design at TQ 7989 7895 and TQ 7997 7895. These two buildings have a cut feature adjacent to them which are likely to represent the extraction pits for soil for the embankments. No corresponding extraction sites are present for the northern three buildings, although the drainage ditch has been widened at a point south of the central store. The three northern structures were connected to each other by a path which then headed north to the sea wall. A landing stage is also depicted for the first time on the 1897 map; this was at TQ 8015 7916 and is likely to have been associated with this site. In contrast, no obvious path connects to the southern buildings. By 1908 two further buildings and embankments had been built in the southern field south of and in a line with the other two. These also had a corresponding extraction pit. They are at TQ 7990 7887 and TQ 7997 7888. Between these and a little to the south, is another extraction pit, with a small spoil heap on its southern side (at TQ 7994 7883). It is not clear if this represents abandoned work on an eighth site.
By 1908 the landing stage is no longer depicted on the Ordnance Survey map but the path that was previously confined to the northern field extended southwards past the southern group. This may indicate that access was no longer via the river. Alternatively the removed landing stage and the presence of an extraction pit with no associated building may indicate that this site was very short lived and had been abandoned by 1908. Much of this site still survives, although the buildings are in a ruinous condition and two of the extraction pits have been levelled. This site was mapped from aerial photographs as part of the English Heritage: Hoo Peninsula Landscape Project.(11-15)

Magazines were constructed on St Mary's Marshes, at least in the first instance, as a commercial venture in order to aid distribution of explosives, particularly given the restrictions on shipping large quantities of explosives further up the Thames towards London. The initial five magazines were constructed in 1892 by the Thames Storage (Explosives) Company with two further magazines added between 1895 and 1900. The Thames Storage (Explosives) Company went into liquidation in 1907 but references in the Kelly’s Directory volumes suggest the site was reincarnated as a ‘Government magazine’ which closed around 1913. Evidence for post-1907 use of the St Mary’s Marshes site is supported by the existence of an unidentified explosives factory in Kent which was storing explosives in the same period, 1907-1913. Documentary evidence suggests that the seven concrete explosives magazines which survive on the marshes may have replaced magazines originally built in brick. (16)

<1> Victor Smith and Ron Crowdy, Thames Gateway Assesment: Gazetteer of Defence Sites (Index). SKE6445.

<2> 1946, Photograph (Photograph (Print)). SWX9477.

<3> 1946, Photograph (Photograph (Print)). SWX9629.

<4> 1947, Photograph (Photograph (Print)). SWX9822.

<5> 1947, Photograph (Photograph (Print)). SWX9852.

<6> 2000, Photograph (Photograph (Print)). SWX10252.

<7> 2000, Photograph (Photograph (Print)). SWX10265.

<8> Wessex Archaeology, 2002, North Kent Coast Rapid Coastal Zone Assessment Survey Phase II: Field Assessment (Pilot) (Bibliographic reference). SWX11840.

<9> historic england, 2014, Hoo Peninsula Outline Historic Area Assessment: St Mary Hoo Parish. Research Report 2014-52 (Bibliographic reference). SKE31593.

<10> English Heritage, 2013, St Mary's Marshes, Hoo St Mary, Medway, Kent: An assessment of the late 19th century explosives magazines (Monograph). SKE29387.

<11> Royal Air Force, 1947, RAF CPE/UK/1923 3007 16-JAN-1947 (Photograph). SKE58578.

<12> 1895, Kent 1:2500 1895 (Map). SKE58884.

<13> Ordnance Survey, 1897, Kent 1:2500 1897 (Map). SKE58577.

<14> Ordnance Survey, 1908, Ordnance Survey Kent 1:2500 1908 (Map). SKE55927.

<15> 2010, NMR 26598/19 6-APR-2010 (Photograph). SKE58885.

<16> English Heritage, 2013, St Mary's Marshes, Hoo St Mary, Medway, Kent: An assessment of the late 19th century explosives magazines (Monograph). SKE29387.