A group of oval or kidney shaped mounds lie astride the railway on Seasalter Level, near Whitstable, and are dated by pottery to the 13th century and assumed to be salt works by Thompson and Miss S. A. Butcher, who excavated one mound and examined four others in 1955 and 1956. Pottery in Maidstone Museum. (1) To the almonry of Christ Church, Canterbury, was appropriated a rent of 'white salt' from Sesalter.(2) [Group centred TR 0680 6394] 15 mounds, 'D' - 'J', 'L' - 'S' are as described above. Four, 'A', 'B', 'C' and 'K', have been removed by bulldozer, though the site of 'B' can be recognised. Surveyed at 1:2500.[For many similar mounds on the Isle of Sheppey - see TQ 97 SW 6.] (3) [TR 0725 6357] Medieval salt workings [NAT] (4) [TR 077 637 and TR 068 637] A group of medieval salt mounds on marsh north of Monkshill Farm, scheduled. (See Illustration Card for extent of scheduled area.) (5,6). Pottery and documentary references date the origin of the site to at least the 11th century, and use up till 1325 when the area was embanked to exclude the sea from Seasalter Level. (7). Additional references from NAR entry and field reports (8,9). For site in context with others in inter-tidal zone, see (10). Saltworking is mentioned at Seasalter in two 8th century charters (11). Photographs relevant to site and finds (12-31).

From the National Heritage List for England:
Details
The monument includes the largest of a group of six salterns situated on the north Kent coast. This group forms part of an original group of 11, five of which have subsequently been destroyed. The salterns lie on the interface between the low-lying coastal marshland on the soutern side of the Swale estuary, periodically inundated by the sea in medieval times, and the gently undulating, wood-fuel bearing, London clay hills further inland. The saltern has a large, north-south aligned, unevenly-shaped midden, an artificial heap of marsh clay waste discarded after brine extraction, measuring 204m by up to 90m, which has been partially disturbed some time in the past by the construction of a field drain. The midden survives as a hummocky area rising to a height of up to 6m above the surrounding ground. During the 1950's five adjacent, associated salterns were destroyed by bulldozing, and archaeological investigations carried out at the time indicated that the middens will partially overlie, and be surrounded by, industrial structures surviving in buried form. These may include wicker or clay-lined pits, evaporation kilns, lead boiling pans and the foundations of temporary wooden buildings. Pottery sherds and other artefacts, including a leather boot, discovered during the excavation suggest that the monument was in use from at least the end of the 11th century until 1325, when Seasalter Level and the surrounding marshes were embanked by the construction of sea walls designed to keep out the encroaching sea and make them more suitable for pasture. Historical records at Canterbury cathedral indicate that salt produced on Seasalter Level was being paid as rent to the cathedral almonry between 1198-1227.

Reasons for Designation
Salt has been produced from sea water or, in inland areas, from brine springs since before Roman times, and the technology used in the medieval period displays a marked continuity with earlier production methods. Brine, from which the water was evaporated to produce the salt, was collected in one of two ways, either by its filtration from coastal sand, soil or pebbles impregnated with salt water during high tides and periodic inundation, or by its collection in pools or pits filled at high tide or by inland springs, sometimes by way of a system of channels, dams and sluices. Medieval salterns include a range of features connected with the collection and evaporation processes, of which the most visually distinctive are the oval or kidney-shaped middens of waste material which may cover areas of 2ha or more. Other features usually survive in buried form beneath and around the middens, illustrating the fact that salterns were often in use for periods of at least a century, during which time they were occupied seasonally, their component structures being rebuilt at the beginning of each summer or as required. Evaporation was often aided by an evaporation kiln fuelled by peat or wood products, of which several different types are known, and the remains of temporary wooden buildings, wooden or wicker troughs and clay-lined pits have also been found during excavation. Salt was an expensive commodity during the medieval period, particularly in demand for food preservation and curing. Salterns are known from documentary sources and place name evidence to have been widely distributed around the English coast and the inland brine springs of Cheshire from at least the end of the 11th century. The industry had declined by the beginning of the 16th century and competition with the superior and cheaper rock salt, mined from the beginning of the 17th century, led to its demise during the early post- medieval period.

Although it has been partially disturbed by the construction of a field drain, the medieval saltern 800m north east of Monkshill Farm survives well as a visually impressive monument, and the excavation of associated salterns has indicated that it will contain well-preserved archaeological remains and environmental evidence. Its close association with five equally well-preserved salterns, the subject of separate schedulings, provides evidence for the importance of the salt industry in this area of north Kent during the medieval period. (33)

<1> Arch Cant 70 1956 44-67 plans illusts (M W Thompson) (OS Card Reference). SKE35478.

<2> Treasurers Accounts 1198-1227 Chapter Library Canterbury Cathedral (OS Card Reference). SKE50679.

<3> English Hist Review No 219 July 1940 Central Financial Syustem of Christ Church Canterbury 1186-1512 (OS Card Reference). SKE41645.

<4> F1 ASP 19-AUG-63 (OS Card Reference). SKE42178.

<5> OS 1:10000 1973 (OS Card Reference). SKE48158.

<6> DOE (IAM) AMs England 2 1978 114 (OS Card Reference). SKE40699.

<7> DOE (IAM) Record map (OS Card Reference). SKE40765.

<8> English Heritage Schedule Entry Revised 07-JUN-1995 (OS Card Reference). SKE41643.

<9> Field report for monument TR 06 SE 6 - August, 1963 (Bibliographic reference). SKE5268.

<10> Department of Archaeology, University of Reading, 1994, Inter-tidal archaeology in Kent, p32-3 (Unpublished document). SWX9353.

<11> Tatton-Brown, T., 1984, The Towns of Kent, p32 (Article in monograph). SWX7259.

<12> HURDLE IN S1 Types: SALT MOUND (Photograph). SKE549.

<13> UNSPECIFIED VIEW OF SITE- GLASS NEGATIVE Types: MOUND,INDUSTRIAL SITE,POTTERY,SALTWORKS (Photograph). SKE441.

<14> UNSPECIFIED VIEW OF SITE- GLASS NEGATIVE Types: MOUND,INDUSTRIAL SITE,POTTERY,SALTWORKS (Photograph). SKE442.

<15> UNSPECIFIED VIEW OF SITE- GLASS NEGATIVE Types: MOUND,INDUSTRIAL SITE,POTTERY,SALTWORKS (Photograph). SKE443.

<16> UNSPECIFIED VIEW OF SITE- GLASS NEGATIVE Types: MOUND,INDUSTRIAL SITE,POTTERY,SALTWORKS (Photograph). SKE444.

<17> TIMBER STRUCTURE OVER PIT 2 IN TRENCH S6 Types: SALT MOUND (Photograph). SKE551.

<18> TIMBER STRUCTURE OVER PIT 2 IN TRENCH S6 Types: SALT MOUND (Photograph). SKE550.

<19> UNSPECIFIED VIEW OF SITE-GLASS NEGATIVE-NO PRINT AVAILABLE Types: MOUND,INDUSTRIAL SITE,POTTERY,SALT (Photograph). SKE440.

<20> HURDLE IN S1 Types: SALT MOUND (Photograph). SKE548.

<21> TIMBER STRUCTURE OVER PIT 2 IN TRENCH S6 Types: SALT MOUND (Photograph). SKE552.

<22> TIMBER STRUCTURE OVER PIT 2 IN TRENCH S6 Types: SALT MOUND (Photograph). SKE553.

<23> Thompson M. W., 1956, A Group of Mounds on Seasalter Level, near Whitstable, and the Medieval Imbanking in this area (Article in serial). SWX7459.

<24> 1946, Photograph (Photograph (Print)). SWX9663.

<25> 1998, Photograph (Photograph (Print)). SWX11476.

<26> 1998, Photograph (Photograph (Print)). SWX11477.

<27> 1978, Photograph (Photograph (Print)). SWX11478.

<28> 1994, Photograph (Photograph (Print)). SWX11479.

<29> 1994, Photograph (Photograph (Print)). SWX11480.

<30> 1994, Photograph (Photograph (Print)). SWX11481.

<31> 1998, Photograph (Photograph (Print)). SWX11513.

<32> 1978, Photograph (Photograph (Print)). SWX11454.

<33> English Heritage, Register of Scheduled Monuments (Scheduling record). SKE16191.