Lion Link Cable Route, Geotechnical Investigations; Section A- Knodishall, Sternfield and Saxmundham

The Section A phase of fieldwork involved the monitoring of twelve of the seventeen originally proposed trial pits, two of the three originally proposed boreholes and two Window Samples. " 12 x 1m x 3m trial pits " 2x boreholes " 2 x window samples Prior to the most recent revisions, the proposed interventions comprising Section A located within the parishes of Knodishall, Sternfield and Saxmundham were as follows: " Sternfield (SNF 031): no boreholes; six trial pits, TPA01 - TPA05 and TPA17 " Knodishall (KND 047): one borehole, BHA02; eight trial pits, TPA06 - TPA08, TPA10, TPA13 - TPA16. " Saxmundham (SXM 086): one boreholes, BHA01; two trial pits, TPA11 and TPA12 The trial pits and boreholes were located to test the geological substrate, install ground water pipes and to test soak away properties of the underlying geology. The locations were set out by the geotechnical contractor (Geotechnics Ltd), as per the WSI and SCCAS agreed plan. In the field, where trial pits or boreholes was found to encroach on dense archaeological features or remains, they were moved and excavated in a new location as close as possible to the original position; these movements were agreed following discussion between Geotechnics Ltd and SCCAS. The archaeological monitoring involved the continuous presence of a competent archaeologist during the geotechnical works with an emphasis on the trial pits. The less archaeologically damaging borehole investigations, which were undertaken broadly at the same time, were generally subjected to less intensive scrutiny on site. The contractors borehole and trial pit logs were subsequently provided to the CA Geoarchaeology Manager for the purpose of using the data, in conjunction with that recorded by CA on site from the trial pits, to construct a geological deposit model across the site. Initially, the trial pits were subject to the removal of 0.3 - 0.5m of topsoil over a c.3m x c.3m square. Where this did not reveal the archaeological horizon, a small 1m x 3m trench was excavated within original square to the top of the archaeological horizon. Once fully recorded the trial pits were then excavated to their full depth of 3.0m. The archaeologically sensitive boreholes were hand or machine excavated to remove the superficial overburden layers (topsoil and subsoil) to either the natural substrate or archaeological horizon. After recording, these were backfilled with the boreholes inserted to various depths, normally exceeding 10m. Upcast spoil was examined visually for the presence of artefactual evidence and was also subject to metal-detector survey. Where no archaeological features were found to be present, the geotechnical contractors were able to proceed with the full depth excavation of the trial pit into the naturally occurring superficial geology. During September to October 2025, Cotswold Archaeology (CA) carried out a programme of archaeological monitoring of geotechnical trial pits on land designated for part of the Lion Link cable route running from Knodishall to Wangford with Henham with a branch to potential landfall sites at Reydon and Walberswick. This report outlines the results from Section A of the scheme only, located in the parishes of Knodishall, Sternfield and Saxmundham. During this tranche of works, a total of twelve trial pits were excavated and recorded to depths of 3.0m along with four boreholes which, in conjunction with the trial pits, were subject to geoarchaeological deposit modelling from the information gleaned by the geotechnical team. No Archaeological features were encountered during the fieldwork, however the overburden deposits, comprising topsoil and subsoil, were recorded along with details of the geological substrate. Geoarchaeological assessment and modelling revealed a complex sequence of deposits shaped by glacial, fluvial, and marine processes.