Event/Activity EPM265 - Archaeological Monitoring of Geotechnical Works at the Portsmouth Historic Dockyard

Pre-Construct Archaeology carried out an archaeological watching brief during geotechnical investigation works at Dry Dock No. 3 in Portsmouth Historic Dockyard between the 18th August and the 17th September 2008. The purpose of the geotechnical investigation was to obtain information about the construction of the Dry Dock and the ground conditions surrounding it to inform the foundation design of the new Mary Rose Museum. The Dry Dock forms part of a Scheduled Monument which includes Basin No. 1, Dry Dock Nos 1 to 6 and the associated masonry sea walls. The docks are also a Grade I Listed Building. Monitoring by an archaeologist was carried out on the excavation of two machine excavated observation pits, and five shallow hand excavated trial pits. The observation pits were located against the northern wall of the dock. Pit 1 measured 2.40m east-west by 2.30m north-south and was excavated to 2.75m below ground level, a slot was then hand excavated to 4.25m below ground level in the south-west corner of the pit. Pit two measured 4m east-west by 1.80m north-south, machine excavated to 3m below ground level and a slot hand excavated to 5m below ground level in the south-west corner. Five shallow hand excavated pits measuring approximately 0.30m by 0.30m to a depth of 1.20m below ground level (unless prevented by obstructions) were located to the north and south of the Dry Dock. A core was taken through the Dry Dock floor, the location of which had to be changed due to timber being encountered on the first attempt which the drill could not cut through. Four boreholes were drilled to a depth of approximately 20cm below ground level and were located at the corner of the Dry Dock. The boreholes were not archaeologically monitored but a note was kept of any evidence for archaeological features or structures associated with the construction of the dock within the core and the depth at which these were encountered. Elements of the construction of the dock were revealed during the work including the construction cut, backfilling material, and the outer edge of the dock wall. The thickness of the dock floor and associated structural elements surrounding the dock were also recorded. Museum Accession No: 2008/323.