NHER 66860 (Monument record) - Late Saxon/early medieval salterns and post-medieval drainage features

December 2016. Desk-based Assessment.
Assessment of proposed development site.
This study concluded that archaeologically-significant remains are likely to be present, primarily due to the proximity of low earthworks thought to represent medieval or earlier saltern mounds. These are likely to comprise the accumulated debris from nearby salt production and are visible on aerial photographs (see NHERs 27907 and 27909).
Sources examined as part of this study include an enclosure map of 1820, which shows the site to lie within an area labelled as 'Old Enclosed Land'. It appears that the various drains and field boundaries that now bound and bisect the site were all in existence by this time. The more sinuous examples potentially had much earlier origins.
During a visit undertaken as part of this work five east-to-west aligned linear earthworks were observed in the western central part of the site. These correspond with features that are visible on a 1946 aerial photograph and can also be seen in visualised lidar date of the site. A slight rise in ground level at the northern end of the site is likely to correspond with a probable saltern mound that is visible as an earthwork on aerial photographs (one of those recorded as NHER 27907).
See report (S1) for further details.
P. Watkins (HES), 16 April 2023.

February 2018. Earthwork Survey and Trial Trenching.
Evaluation of proposed development site.
An initial topographic survey recorded a number of discrete rises in elevation likely to represent the remains of medieval or earlier saltern mounds lying partially or wholly within the site. Those that correspond with previously recorded earthworks visible on aerial photographs include one in the north-west corner of the site (Saltern 1; one of two recorded as NHER 27907) and two at its eastern edge (Salterns 5 and 6; both recorded under NHER 27909). Previously unrecognised features included a mound that falls entirely within the northern half of the site (Saltern 7) and two that fall partially within the southernmost part of the site (Salterns 1 and 4). These last two had been subject to archaeological excavation prior to the development of the site to the south (see NHER 62661). This survey also revealed a number of east-to-west and north-to-south aligned drainage ditches in the lower lying portions of the site, which included those noted in 2016 (see above).
The subsequent trial trenching saw the excavation of fourteen trenches (Trenches 21-34). All six of the possible saltern mounds identified by the preceding topographic survey were found to be associated with probable salt-production deposits. Hand auguring demonstrated that these deposits were between 0.9m and 2.15m thick, with the greatest depths of material being associated with the three saltern mounds in the southern half of the site. The saltern mound deposits consisted primarily of mid yellow brown silty sands likely to represent the waste from a production process where salt was generated by boiling down a brine solution created by washing and filtering salt-impregnated silts and sands scraped up from the nearby marshes or foreshore. Two of the mounds (Salterns 1 and 6) also contained concentrations of burnt material and fragments of what was probably lining from broken-up brine-boiling hearths. A thick tip of hearth waste was also associated with Saltern 4 at the southern end of the site. Clay-lined water tanks likely to have been used as part of the silt filtration process were exposed in three of the trenches (Salterns 4, 5 and 7). None of these features and deposits produced any dating evidence but they were all presumed to relate to medieval or earlier industrial activity. One find of note was a lump of lead that potentially represents waste generated during the repair of lead salt pans. Samples taken from the filtration waste deposits were found to contain foraminifera, ostracods, occasional mollusc shells and small quantities of charcoal.
A number of the excavated trenches also coincided with the former drainage ditches identified by the earthwork survey. These were presumed to represent features of later medieval to post-medieval date that had been dug after the area was reclaimed from the saltmarsh and began to be used as pasture. This was confirmed by the finds recovered from the ditches, which included a small assemblage of medieval/post-medieval and post-medieval pottery sherds, pieces of medieval and post-medieval brick and tile and fragments of post-medieval clay tobacco pipe. One of these ditches also contained several fragments of animal bone.
The only earlier finds recovered are a single prehistoric flint flake and a possible Roman tile fragment.
The saltern mound in the south-west corner of the site was shown to have suffered a degree of recent truncation, being overlain by a layer of modern material containing concrete, plastic, metal and textile.
Information from report uploaded to OASIS. HER copy awaited.
P. Watkins (HES), 16 April 2023.

February-March 2019. Excavation.
This final phase of archaeological mitigation prior to the development of the site saw further investigation of three of the saltern mounds identified by the preceding work. These included one that extended beyond the southern limits of the site (Saltern 4) and two that continued beyond its eastern boundary (Salterns 5 and 6), both of which had originally been identified as earthworks on aerial photographs (recorded as NHER 27909).
The most significant evidence was recovered at Saltern 5, where a burnt layer within the lower sequence of filtration waste deposits was found to contain debris that was clearly derived from brine boiling, including salt-slag cakes that had formed in the bases of circular, pit-like, clay-lined hearths and briquetage in the form of fired clay support bricks (probably for lead pans). Two undated sub-circular clay-lined features were associated with this earlier group of deposits. The upper part of the mound revealed an in-situ brine-boiling hearth and associated rake-out pit as well as additional clay-lined features likely to represent the surviving elements of filtration units used in the production of concentrated brine. The hearth was a square structure with a clay lining and a central rectangular column that divided the chamber into two equal-sized areas. This structure and the sub-rectangular pit within which it lay were both orientated towards the prevailing south-westerly wind direction. Archaeomagnetic dating suggests that this hearth had last been fired between 870 and 1050 AD (95% confidence). This is broadly consistent with a radiocarbon date of 1023-1154 cal AD at 95.4% confidence (SUERC-87802; 952 ± 26 BP) obtained for charcoal from one of the tips of ashy waste within the adjacent pit. A similar Late Saxon/early medieval date of 1030-1155 cal AD at 95.4% confidence (SUERC-87801 939 ± 26 BP) was also obtained for charcoal recovered from a dump of hearth waste within the later sequence of filtration waste deposits. These dates are also consistent with the limited artefactual evidence, with three sherds of Late Saxon pottery of probable late 10th- to 11th-century date recovered from one of these later deposits. This final sequence of filtration waste deposits were cut by a number of additional clay-lined features and a single unlined pit. The salt marsh deposits beneath this saltern were found to be overlain by a thin horizon of dark brown silty clay and sand, which micromorphological analysis suggested had formed as a result of slow water action with repeated episodes of surface drying out. This layer potentially represented nascent soil formation prior to the establishment of the saltern.
The lower portion of the saltern mound at the southern edge of the site (Saltern 4) consisted of layers of filtration waste that appeared to lie directly on the salt marsh deposits. These were overlain by a series of tips of burnt material that contained fragments of fired clay likely to represent broken up hearth lining. Charcoal from one of these deposits produced a Late Saxon radiocarbon date of 901-1025 cal AD at 95.4% confidence (SUERC-87797; 1052 ± 26 BP). Two clay-lined features were associated with the early stages of the mound, which were overlain by further filtration waste deposits, one of which produced a fragment of Late Saxon pottery of probable late 10th- to 11th-century date. Additional clay-lined features likely to represent two further filtration units were cut into this upper sequence of deposits.
The investigation of the north-easternmost salter mound (Saltern 6) revealed a sequence of filtration waste deposits and one possible dump of hearth waste overlying the natural saltmarsh deposits. The only finds of notes were several probable fragments of vitrified lining from an iron smithing heath.
Bulk samples taken from features and deposits associated with the salterns produced a similar range of charred plant macrofossils to those taken during the preceding work. There was again evidence to suggest that peat was being used as a fuel, in addition to oak wood/charcoal and possibly coal. Although a number of sub-samples were taken for pollen none produced sufficient grains for interpretation. Several samples taken from filtration units associated with Saltern 5 were also examined for ostracods and foraminifera. The remains present serve to confirm that the silts used were collected from the lower saltmarsh/upper tidal mudflats zone of the tidal creeks that lay closest to the salterns.
Later remains were limited to elements of two heavily truncated curvilinear gullies exposed in the south-east corner of the site that had probably been drainage channels associated with post-medieval hayricks.
Information from assessment report uploaded to OASIS. HER copy and final reports awaited.
P. Watkins (HES), 16 April 2023.