York Historic Environment Record

Borehole 1 ground level at the time of recording was at approximately 9.30m OD with the top of the water table encountered at approximately 6.00m BGL (3.30m OD). The top of the natural geology was identified at 7.80m BGL (approximately 1.5m OD). Borehole 2 ground level at the time of recording was at approximately 9.04m OD with the top of the water table at approximately 8.00m BGL (1.04m OD). Natural was below 9.00m BGL (0.04m OD). Borehole 3 ground level at the time of recording was at approximately 9.25m OD. The top of the water table was encountered at approximately 8.00m BGL (1.25m OD). Natural geology was observed from 8.85m to 9.95m BGL (0.40m– -0.70m OD). Borehole 4 ground level at the time of recording was at approximately 9.04m OD. Natural geology was present at 6.50m to 6.9m BGL (3.04m–2.14m OD). The boreholes identified a sequence of deposits, with the eariest consisting of pre-medieval deposits, ranging in thickness from 0.70m to 1.8m, forming a layer between approximately 0.55m–3.74m OD although dating was not certain due to lack of dateble artefacts. Deposits attributed to the medieval period, following the damming of the River Foss and the creation of the King’s Fishpool, were predominantly organic, waterlogged, laminated silts and clays. These deposits appear to have accumulated slowly under wet conditions. This was a substantial build-up of material ranging in thickness from 1.70m to 3.75 (being in excess of 3m thick in all but one borehole), and encompassing a depth range from 2.04m to 7.05m OD across the site. The post-medieval period differed significantly from earlier waterlogged material, being drier with more domestic and building debris forming a horizon 1.3m–1.7m at depths between 6.70m OD and 7.24m OD. This may represent deliberate attempts to consolidate and build-up the ground level to reclaim formerly boggy, waterlogged land. The top 1.80m to 2.55m of deposition comprised rubble and soils, likely relating to 18th and 19th century gardens and houses in the area. The uppermost layers related to the formation of the 20th century motor garage and current ground surface. The results of this limited period of groundwater monitoring indicate that deposits below 1.70m BGL (7.55m AOD) have remained within the water table throughout the monitoring period. The evidence provided by the biological markers suggests that the preservation potential is poor due to the fluctuating ground water conditions.