Site Event/Activity record ECH6727 - Chester Northgate Redevelopment: Report on Archaeological Monitoring of Boreholes

The hand-excavation of the start holes for seven geotechnical boreholes (BHs 203, 205, 208, 209, 210, 211, 212) was undertaken during January 2018 as part of the Chester Northgate redevelopment scheme. The borehole logs, compiled by BettsGeo, were also consulted, and some of the borehole cores were available for inspection on site. This work follows on from compilation of an initial desk-based assessment in 2016 (ECH 6205), supplemented by two additional desk-based assessments for areas of 'off site' groundworks at New Crane Street (ECH6296) and a new drain linking the site to the River Dee (ECH6297), also evaluations undertaken in 2015 (ECH 6203), 2016 (ECH 6220), and 2017 (ECH6726). All seven of the boreholes were placed outside the development boundary proper, since their purpose was to investigate ground conditions in areas where the ‘off site’ groundworks were proposed in respect of the scheme, relating principally to the construction of a major new drain extending south from the development site to the River Dee, and of an electricity substation on New Crane Street, to the west of the site. Two of the boreholes (BHs 203, 205) were situated immediately west of the site, west of St Martin’s Way/Nicholas Street, three (BHs 208, 209, 210) were to the south, in the vicinity of Chester Castle and the river, and two were placed in a surface car park on the north side of New Crane Street. From an archaeological standpoint, the monitoring revealed relatively little of interest, mainly due to the very limited exposure available within the start holes, and the fact that they were excavated to a relatively shallow depth (c 1m). However, the lack of observable remains cannot be taken to indicate the absence of archaeological deposits at these locales, since it is highly probable that significant remains are present at a greater depth in at least some of the areas investigated, especially in the vicinity of BH 203 and BH 205, which were well inside the medieval city walls, within the core area of the ancient settlement, in the area known as Linenhall. Indeed, the log for BH 205 recorded ‘made ground’, c 1.5m thick, below modern surfaces and make-up levels, some of which may represent intact archaeological strata, though this material could not be characterised or dated from the borehole records. Nothing of interest was noted in BH 208, but examination of the cores recovered from BH 209 and BH 210, which were located closer to the river, just inside the medieval city wall, demonstrated the existence of very deep accumulations of alluvial silt, c 2-3m below the modern surface, suggesting that the area may have been on the foreshore of the River Dee prior to the construction of the medieval defences. Above the silts was c 1-2m of ‘made ground’, which, in BH 209, seemingly included significant inputs of ash and industrial waste, perhaps derived from post-medieval refuse disposal. At New Crane Street, where the car park lies to the west of the medieval city walls, earlier phases of archaeological evaluation trenching demonstrated the presence of thick deposits of alluvial silt, suggesting that this area may also have been on the foreshore of the Dee well into the post-medieval period, and may have been used for the dumping of domestic refuse during this period. Similar material, several metres thick and containing occasional fragments of post-medieval pottery, brick, glass and clinker, was also recorded in the borehole logs for BH 211 and BH 212. (1)