2017:491 - 29-43 Castle Street, Belfast, Antrim

Ahead of the proposal to extend the Bank Buildings westwards through the existing buildings at 29-43 Castle Street, Belfast, monitoring of ground reduction was conducted across the site followed by the excavation of 5 test pits to the upper levels of naturally occurring subsoil. It was originally proposed to excavate a series of test trenches across the footprint of the development site, however this proved difficult to achieve. Following the demolition of Commonwealth House to existing street level, substantial, re-enforced concrete foundations extended across the site. The frequency of the beams was such that the proposed trenches would have consisted of a series of small test pits. In addition to this the culverted channel of the Farset River crossed the northern portion of the site from west to east preventing any access to this area.
The proposed development will be constructed using driven piles. To facilitate this, it was necessary to reduce down the levels within the site, removing much of the modern overburden material. The ground level was reduced using a back-acting machine to an average depth of 1.6m below the existing street level. This exposed a brown silty layer of late 19th – 20th-century fill containing deposits of modern redbrick, concrete blocks and mortar across much of the site. This layer varied in depth from 0.1-1.6m. This typically overlay a brown clay approximately up to 0.6m thick and again containing modern building debris. Where exposed, this directly overlay naturally occurring subsoil which consisted of a wet black or blue sand/ sleech.
To fully ascertain the depth of subsoil, 5 test pits were excavated within the site. The test pits were located randomly with their position being dictated by the underlying site conditions.
No archaeological deposits were identified during the course of the monitoring.

7-9 Castlereagh Street, Belfast BT5 54NE