Beaver House and 39-42A, Hythe Bridge Street, Archaeological Evaluation and Watching Brief Report

Between the 10th and 20th July 2023, Oxford Archaeology undertook an evaluation and watching brief on ground investigation boreholes at Beaver House, Oxford. The works were intended to include the excavation of a single evaluation trench, designed to investigate the possible location of the Rewley Abbey moat, previously mapped in the vicinity. Due to the presence of numerous services and restricted space it was not possible to excavate the evaluation trench. Instead, five purposive boreholes were drilled into the car park to evaluate the underlying deposits. This project was intended to comprise two phases of work. The first of these was a watching brief during geotechnical ground investigation works comprising both shallow test pits and deep boreholes (BHs 01-03). A geoarchaeologist was in attendance to monitor these works and record observations made during excavation of the test pits and the leader pits for borehole drilling. They also monitored the borehole drilling to examine and record the sediment sequence revealed. The locations of the boreholes and test pits are indicated on Figure 2. Only Test Pit 2 was monitored on site, as it became apparent from the boreholes that the sequences in the basement of Beaver House were of minimal interest, comprising a concrete slab over heavily contaminated and truncated terrace gravel. Test pits 3a and 3b were not carried out. The second phase of the investigation was intended to comprise a 10 x 2m trench to be excavated across the projected line of the Rewley Abbey moat (Fig. 2). The trench was to be excavated to a sufficient depth to determine the presence or absence of the moat, but not exceeding a maximum depth of 2m. In the event, the excavation of the trench was not possible due to the presence of numerous live services and underground obstructions. Following discussions between Landgage Heritage and David Radford it was agreed that a series of additional boreholes (OABHs 04-06) would be drilled for archaeological purpose, with the aim of locating the moat. Due to the number of buried services, these boreholes were restricted to the northern part of the external car park. The boreholes were drilled using a dynamic sampling rig (windowless sampler) capable of recovering a continuous sequence of sleeved cores in 1m lengths. OABH05 and OABH06 refused at shallow depths due to the presence of a concrete obstruction. OABH04, OABH07 and OABH08 were successfully drilled to the surface of the Pleistocene (Northmoor) terrace gravel. The cores were opened, logged and photographed on site by the attending geoarchaeologist, after which they were returned to OA premises for storage should any further work be required in addition to this report. Should no further work be required the cores will be discarded. Overall, the results of the investigation suggest the sub-surface sedimentary sequences in the areas investigated have limited archaeological and palaeoenvironmental potential. No medieval or earlier occupation deposits were identified, and the artefactual material recovered from the boreholes largely dates to the 19th and 20th centuries and comes from the made ground deposits. It is probable that the original ground surface beneath the basement slab of Beaver House has been truncated by previous construction activities, which would have removed any earlier evidence of occupation. The channel and alluvial deposits recorded beneath the open car park in the east may be related to edge sequences associated with the Wareham Stream. There was no evidence in the borehole cores of medieval or earlier occupation associated with these deposits, although the diameter of each borehole was small with a 100mm footprint. The likelihood for reworking of organic material within these sequences by channel processes reduces the potential for detailed palaeoenvironmental work for landscape reconstruction.