Monument MPM2035 - Dock wall and construction cut, Dry Dock No. 3, Portsmouth Historic Dockyard

A feature interpreted as the construction cut for Dry Dock No. 3 and part of the limestone dock wall were revealed in an observation pit during archaeological monitoring in 2008. The decayed remains of a railway sleeper thought to have belonged to the dockside rail/crane system were also recorded. Dry Dock No. 3 was constructed between 1799 and 1803 and extended in 1859.

Features relating to the construction of Dry Dock No 3 revealed in an observation pit during archaeological monitoring of geotechnical works in 2008. The pit was located on the northern dock wall of Dry Dock No. 3 in Portsmouth Historic Dockyard.

A feature interpreted as the construction cut for the dry dock was observed as a large cut running north-west to south-east across the pit. The cut ran the length of the pit from east-west and a maximum of 1.30m north-south. It had a maximum depth of 3.40m and was observed at 2.99mOD at it's highest level. This feature had cut a series of dumped deposits interpreted as made ground. A modern feature 1.30m north-south by 0.80m deep had truncated the cut and was visible in the west facing section.

The cut had been filled by a sequence of deposits, the lowest of which was a 1.60m deep layer of moderately firm silty clay containing occasional fragments of building material and charcoal flecks at 1.29mOD. Above this was a 0.05m thick layer of moderately firm silty sandy clay overlain by a thin lens of organic material above which was a 0.40m thick moderately loose deposit of mixed gravels and silty clay. The final deposit was a 1.80m deep layer of firm sandy silty clay [11] the top of which was recorded at 3.44mOD below ground level. This deposit was also observed in an observation pit to the west during the same investigation where it was thought to represent backfill to the construction cut (see MPM2034).

The remains of a railway sleeper thought to belong to the dockside rail/crane system were observed within deposit [11]. The timber was almost completely decayed and measured 900mm north-south by 300mm east-west on a north-south alignment. Two iron spikes had been driven vertically through it.

A 0.10m thick cinder deposit [10] overlay the backfill [11] and the railway sleeper at 3.59mOD. The same deposit was recorded in an observation pit to the west (see MPM2034). Above this was a 0.15m deposit of made ground 3.74mOD below ground level.

The dock wall constructed from limestone blocks was located 0.55m back from the concrete wall of the Mary Rose ship hall (demolished since the investigation). The vertical face of the wall was followed to a depth of 2.64mOD below ground level where excavation stopped.

Sayer, Kathelen, 2009, Archaeological Monitoring of Geotechnical Works at the Portsmouth Historic Dockyard, Portsmouth, Hampshire (Unpublished document). SPM612.