2003:526 - DUBLIN: Assay Office, Dublin Castle, Dublin

The Assay Office lies within the Dublin Castle complex, outside the moat of the Anglo-Norman castle on its south-western side. It is close to the Ship Street Gate and adjacent to the ‘Clock Tower’ building (the Chester Beatty Library) on its western side. The location is close to the supposed location of the Dubh linn, the ‘black pool’ of Dublin. The Assay Office building was constructed in 1872 as a canteen for non-commissioned officers and privates from the Ship Street Barracks.

The proposed development involves the reduction of the present basement floor level and the construction of a new basement, both outside and to the west of the building and beneath the northern portion of the existing building that currently does not have a basement. Monitoring of four engineering trial holes took place in September 2003. Test-pits 1–3 were opened inside the basement to the rear (southern side) of the building. These pits all revealed roughly the same profile. A 0.3m+ deposit of organic silt, probably of medieval origin, underlies a 0.35m deposit of crushed red-brick rubble in a similar silt matrix. The crushed rubble may be derived from 18th-century buildings cleared to make way for the first phase of barracks development in the 19th century or may be specific to the 1872 redevelopment of the site. Sterile grey boulder clay appears to have been reached in all three pits at a depth of c. 0.65–0.7m below basement floor level (4.69–4.64m OD).

A single deep pit was opened externally on the building’s northern side. The remains of filled-in, demolished basements were revealed, underneath which the organic silt of possible medieval origin was again present at 4.2–4.5m OD approximately.

An excavation will be conducted as part of the site preparation works.