Summary.
Four trial-pits were excavated by the Colchester Archaeological Trust immediately to the south of Colchester Castle in Upper Castle Park, High street, Colchester, Essex, to help inform on the feasibility of a proposed scheme to install new lighting around the castle.
Foundations belonging to the castle forebuilding were identified below the modern turf/topsoil in two of the trial-pits (TP2 and TP3). In TP2, the foundation was c 200mm below modern ground level (bmgl). This would allow for low voltage power cables to be buried in the modern topsoil above the forebuilding remains in this location. In TP3, the foundation below the doorway of the forebuilding was 140mm bmgl. However, 0.6m to the east, the top of the same foundation was level with the current ground surface. The
proposed LED light in this location would need to be moved (ideally to the east within a backfilled archaeological trench excavated in 1977) and it would not be possible to bury the power cables beneath the existing topsoil.
Trial-pit 1 was located inside the forebuilding and was excavated through dark, sandysilt soils containing 19th/20th-century finds, down to the maximum depth of 0.4m bmgl. It is likely that TP1 was located within a backfilled 20th-century archaeological investigation, possibly the 'shaft' sunk against the south face of the keep in 1932 to establish the nature of the castle foundations (Drury1982, 315).
In Trial-pit 4 to the east of the castle forebuilding, a 20th-century topsoil overlaid a layer of redeposited natural sand mixed with septaria and Roman brick and tile fragments. This deposit may correspond with the fill of a vertical-sided shaft or trench identified during archaeological investigation to the east in 1977, which was interpreted as part of J. T. Round's explorations in the 19th century (Drury 1982, 324).
A level survey was undertaken along the route of the proposed cable trench in front of the south side of the castle and the results compared to the levels at which significant archaeological deposits were encountered during previous excavations(Drury 1982).Deposits interpreted as belonging to the surface of the Roman temple precinct
survive at a depth of 0.9m bmgl and deposits associated with the construction of the castle keep survive 0.4m bmgl. However, caution should be noted as further to the west during the recent installation of a new water pipe (2019) significant deposits were encountered at depths of only c 150-200mm bmgl (CAT Report 1382, forthcoming).