NHER 62667 (Monument record) - Late Saxon to medieval saltern

December 2014-January 2015. Watching Brief.
Monitoring of removal of concrete rafts, walls and floors associated with a 1960s farm, ahead of the proposed redevelopment of the site (Areas A-D).
This work revealed no direct evidence for the probable saltern mound visible as earthworks on aerial photographs (NHER 27889). It was however noted that the concrete rafts were positioned on a generally raised area of land that may represent the remains of this feature.
A possible mound made up of late 18th- to early 19th-century bricks was exposed beneath one of the rafts and a rubble spread containing brick of a slightly earlier, 17th- to 18th-century date was observed beneath another. These deposits are likely to represent demolition material brought in from elsewhere for use as hardcore during the construction of the farm.
Other monitored works included the excavation of four trenches to confirm the presence of existing services. These revealed no archaeologically significant features or deposits.
No finds were retained.
Information from report uploaded to OASIS, HER copy awaited.
P. Watkins (HES), 17 April 2018.

May-July 2015. Trial Trenching and Excavation.
This phase of work saw the investigation of the probable saltern mound in the westernmost part of the site (NHER 27899). An initial trial trenching evaluation was used to define the extent of the features and deposits associated with the mound, which was then the subject of a strip map and sample excavation. Two additional phases of excavation then took place in the areas where the proposed development would have its deepest impact. This work confirmed that this was indeed a saltern mound and associated with evidence for several phases of salt making. The presence of burnt Thetford-type ware pottery sherds suggested that salt making had commenced during the Late Saxon, which was confirmed by a subsequent programme of radiocarbon dating. The composition of the medieval pottery assemblage suggests that activity had probably ceased at the site by the 13th century.
The natural deposits encountered beneath the saltern were suggestive of a mudflat, saltmarsh environment, with evidence that these deposits were being cut and reworked by intertidal creeks. Organic material was visible in several of these deposits and samples produced plant macrofossils that were indicative of a coastal saltmarsh environment. This interpretation was supported by the analysis of samples taken for pollen and diatoms. Organic remains from one of these deposits produced an Early Bronze Age radiocarbon date of 1876-1691 cal BC at 95% probability (3462 +/-35 BP, SUERC-65061) - a period when the Wash basin experienced a number of marine inundations. This material may though be residual as the pollen within the uppermost silts suggests that they were most likely lain down during the Iron Age. Interestingly, the pollen recovered from the basal deposit of the mound itself shows little evidence for saltmarsh or marine influence, suggesting that this material may actually represent a dump of freshwater silt lain down to raise the ground level prior to the commencement of salt production.
The various features and deposits associated with the saltern mound have been interpreted as representing two broad phases of activity. The first, Late Saxon phase of activity was associated with a number of filtration units, a clay-lined water tank and the remains of several open hearths. These features occurred at successive levels within the lower part of the saltern mound, separated by layers of what was almost certainly waste silt from the filtration process and thin spreads of burnt hearth waste. The filtration units that survived in their original, complete form each comprised a shallow sub-rectangular and flat-based filtration pit connected by a narrow channel to a much deeper, circular water tank. The clay-lined tank was probably used to store and concentrate the brine produced by the filtration process and was the only feature of this type identified during the excavations. The two main groups of features associated with this first phase of were separated by a thin layer interpreted as a leached and weathered buried soil, suggesting a period of disuse. Charcoal from one of the filtration units associated with the first group of features produced a Middle to Late Saxon radiocarbon date of 688-887 cal AD at 95% probability (1225 +/-35 BP, SUERC-65063). Later dating evidence was recovered from deposits associated with the disuse of the second group of features, with a small amount of early medieval pottery recovered and a charred cereal grain recovered from the backfill of a filtration unit producing a Late Saxon/early medieval radiocarbon date of 897-1119 cal AD at 95% probability (1033 +/-35 BP, SUERC-65057). The waste silts overlying the features associated with this first phase of activity produced a number of Thetford-type ware pottery sherds as well as an assemblage of fired clay that included elements of both hearth lining and superstructure.
Features associated with the subsequent, medieval phase of activity included a group of enclosed brine-boiling heaths. These were encountered in the upper part of the saltern mound deposit sequence that predominantly comprised burnt hearth waste containing large amounts of fired clay and slag. The medieval pottery recovered from these deposits includes some sherds that show signs of overfiring/burning and salt residues - suggesting they are from vessels that had been used in the salt production process. The presence of some earlier pottery suggest that there had been at least a degree of reworking of earlier deposits, as did a Middle to Late Saxon radiocarbon date of 727-968 cal AD at 95% probability (1177 +/-35 BP, SUERC-65062) obtained for charred material within one of these tips of burnt material. Although the hearths themselves were all truncated there were nevertheless a number of surviving elements, including hearth bases, superstructures and flues.
The fired clay assemblage recovered during this work comprises over 400 pieces, most of which are fairly amorphous fragments. Unlike the briquetage associated with salt production during earlier periods, no pan fragments were identified, suggesting that metal pans had almost certainly been used. This would appear to be confirmed by chemical analysis of salt slag from the site, which detected the presence of lead and other heavy metals that can only really be explained by the use of lead boiling pans. A proportion of the slag recovered from the upper, medieval deposits was also found to be ferrous, iron smithing debris and it is likely that some of the fragments of vitrified hearth lining and fuel ash recovered were also associated with this activity. An interesting feature of the smithing slag is that some appears to have formed in a smithing hearth base of an unusual shape, possibly suggesting the reuse of a salt-making hearth.
Despite extensive sampling of the excavated deposits very few plant macrofossils were recovered. There is a notable lack of charcoal, suggesting that peat may have been burnt as a fuel, the remains of which have decayed to leave only carbon-rich, black-stained soils.
There was very little evidence for subsequent activity on the site with the only later features of note being two pits of probable late post-medieval date.
See full excavation report (S2) and assessment report (S3) for further details.
An archive associated with this work has been deposited with Norwich Castle Museum (NWHCM : 2016.201).
P. Watkins (HES), 18 April 2018. Amended 18 June 2020.