York Historic Environment Record

Groundwater monitoring October 2018-May 2019 following borehole survey. The results of this limited period of groundwater monitoring at a single location together with geochemical assays of sediment samples indicate that deposits below 1.70m BGL (7.55m AOD) have remained within the water table throughout the monitoring period. There is minimal fluctuation, around 10cm variation on average, and whilst the majority of the development site is hard paved, there is direct correlation with rainfall events, implying that the sub-surface deposits are effectively recharged via surface and groundwater flow. The evidence provided by the biological markers suggests that the preservation potential is poor due to the fluctuating conditions – however there has been no evidence of substantial reductions in the height of the water table during this period, but the ingress of oxygenated rainwater may well be a contributing factor. However, it should be noted that the decay may have occurred prior to deposition and incorporation into waterlogged anoxic deposits.