Event/Activity EPM211 - Archaeological Watching Brief Phase 1B, The Jetties, HMNB, Portsmouth

An archaeological watching brief was carried out by Gifford and Partners on groundworks during refurbishment of the Western Jetties at HM Naval Base Portsmouth in 2000. This was the second phase of works observed by Gifford, and are known as Phase 1B (earlier work known as Phase 1A, see EPM212). As the site lay within Conservation Area No. 22 and indirectly affected Scheduled Ancient Monument 397 (No 1 Basin, 1 to 6 Docks and the associated masonry sea walls) there was the potential of encountering archaeological remains. The groundworks were centred on excavations to enlarge a sub-station on the north side of the Railway Jetty, and comprised the excavation of a large trench and test pits. A transformer compound and porch belonging to the sub-station were demolished ahead of the watching brief taking place. Three test pits were then excavated to the west of the sub-station building, two of which were c3m deep (where the water table was encountered), the third c4m deep. The ground in the first two test pits was found to be heavily disturbed by modern services and concrete foundations. The third consisted only of made ground. A further three test pits were dug in the same area in order to collect soil samples. The first contained no stratigraphy, the second modern brick foundations and services, and the third revealed a layer of granite cobbles covering a 1m thick layer of gravely soil. A roughly square trench excavated for the sub-station enlargement measured 31m x 27m. In this area the site was found to have been divided in two by a large double culvert constructed from two large bore pipes set in concrete. The culvert ran east-west and had been designed to increase the discharge of water from an underground reservoir behind Dock No. 6. This feature had destroyed any earlier archaeology from within a 7m wide strip of the site. In the south-west of the site a large bollard was removed and retained for re-use elsewhere. Several weeks after the main groundworks for the sub-station had been completed, two service trenches running north-south and east-west were excavated to the north of the site. A capstan base was found during this work.