Lynnsport 4 & 5: Middle to Late Saxon Salterns on Land Adjacent to Greenpark Avenue, King's Lynn, Norfolk

Between the 3rd April and 4th of May 2017, Oxford Archaeology East (OA East) conducted an archaeological excavation on land adjacent to Greenpark Avenue, King's Lynn, Norfolk (Lynnsport 4 & 5; TF 62897 20966). The site lies within an area of many salt producing sites (salterns) mapped by the NMP in the vicinity of King's Lynn.
This report includes the results of the initial phase of evaluation carried out between the 27th February and 3rd March 2017, comprising nine trenches. The trenches revealed archaeological remains at three locations on the site associated with salt-making during the Middle to Late Saxon period (Salterns 1-3). The remains of Saltern 1 in the western part of the site included a heavily truncated brine-boiling hearth. Nearby was found the heavily truncated remains of a clay-lined pit which probably represented a silt filtration unit associated with brine production. A layer of burnt deposit representing hearth waste tips, containing fragments of baked clay and slag was also revealed. The remains of Saltern 2 in the eastern part of the site included a large pit that appeared to contain a series of fuel waste tips from a brine-boiling hearth. Furthermore, a trench to the north of Greenpark Avenue uncovered part of the circuits of two circular gullies representing drainage channels for hayricks (Riley circles) of the early modern period.
The underlying geology, including the layer of buried peat, was mapped during previous ground investigation works as part of the development of the site. During the evaluation phase of the investigation OA East placed boreholes through the underlying natural tidal flat deposits and through the salterns (Salterns 1 & 2) revealed by the evaluation to the north of Greenpark Avenue. The results of these investigations were used to build a deposit model for the site for the subsequent excavation phase of works.
The excavation targeted Salterns 1 and 2, to the north of Greenpark Avenue, and the two hayricks. These works investigated the saltern mound deposits in the area to be impacted at depth by the proposed housing development. The topographical survey of the site, carried out during this phase of works, also revealed that further saltern remains (Saltern 4) probably lay in the northern part of the site and extended beyond its northern boundary. Further archaeological features were uncovered within each excavated mound, including silt filtration units for brine production. A series of shallow circular clay-lined pits were also revealed. These were interpreted as possible storage tanks for the concentrated brine produced by the filtration units. Nearby lay two large areas of burnt deposits. These comprised hearth waste material that was deposited in shallow rake-out pits or alternatively middens within depressions on the saltern mound. One of these hearth rake-out pits was probably associated with the heavily truncated hearth excavated adjacent to it during the evaluation phase. These features and deposits excavated in both salterns yielded Middle Saxon radiocarbon dates with some Thetford-type ware pottery sherds also recovered. Together these indicate a Middle to Late Saxon date for the salt-making activity on this site.