HS2 Phase 2a: Archaeological monitoring of Ground Investigation Deposit Model Report - Work Package 04 Contract 2

The works comprised ground investigation at 384 separate locations using several different techniques. Of these techniques only the following are suitable for archaeological and/or geoarchaeological monitoring or bore hole log review: " Cable Rotary (CR); " Cable Percussion (CP); " Trial pits (TP); and " Rotary coring (RC). A total of 19 GI locations were identified as lying within areas where information collected from cores and a review of borehole logs and day books would contribute to geoarchaeological Specific Research Outcomes set out within the GWSI: HERDS and key findings identified within the GDBA. Of these, 11 are located on deposits which are of high geoarchaeological potential including the River Terrace and Alluvial Deposits associated with the River Trent. A further 8 were identified to be of potential interest to the geoarchaeological deposit modelling as they are located on superficial deposits of Till. Over the course of the monitoring exercise six of the locations were descoped (ML213-RC110, ML215-RC104, ML220-RC162, ML221-CR103, ML223-RC102, and ML225-CR107). No trial pits were included within the geoarchaeological monitoring. 11.1.1 Geoarchaeological monitoring of GI boreholes as part of the route wide investigation has resulted in the identification, mapping and modelling of below ground geology. The results successfully enhance understanding of archaeological and palaeoenvironmental understanding of the landscape. 11.2 North Area 11.2.1 The northern area (GCZ26, 27, 28) was generally lacking in superficial geology with bedrock directly overlain by topsoil, with the exception of two historic BGS locations in the far southeast (GCZ26) in which Pleistocene glaciofluvial sands and gravels, and glacial till were identified in an area of lower topography. Monitored GI interventions from this investigation confirmed the sparsity of such deposits in this area. There are no further or updated recommendations for these GCZs based on the GI data. 11.3 Central Area 11.3.1 The central area (GCZ: 24, 25) yielded the most superficial geology, which consisted of glacial till and glaciofluvial sands and gravels of Pleistocene age, as well as Holocene alluvium. The geoarchaeological data expanded the known location of surviving glacial till and alluvium within GCZ24 and confirmed presence of alluvium among the higher elevations of GCZ25. 11.3.2 Specifically, till identified within the valley (GCZ24) with a thickness of 0.7m expands the known area of surviving till previously recorded eastward. Two locations identifying Holocene (organic) alluvium to the east of the valley (GCZ24), with one located adjacent to the M6 motorway and the other bordering Stone, expand on the known extent of alluvium associated with the Filly Brook which runs roughly southwest to northeast through the lower valley. The third location of alluvium identified is located atop the northern valley slope, and is also associated with the Filly Brook, though its northern extent closer to its source. Alluvium is already mapped by the BGS in these locations though not identified in the utilised BGS borehole data which fall within this mapped area, with the recent interventions confirming their presence. 11.3.3 The lateral extent, character, and age of the Pleistocene Till and glaciofluvial sands and gravels and organic alluvium, should be investigated further through a programme of purposive geoarchaeological boreholes in the areas of proposed impact. This would enable the archaeological and paleoenvironmental potential of the three distinct units to be better understood and effective mitigation to be devised. 11.4 South Area 11.4.1 The additional datapoints provide by the monitored GI works placed within the southern area (GCZ: 21, 22, 23) continued to record areas devoid of Pleistocene and Holocene superficial geology.