Monument record MDO18741 - Wadham House Roman Conduit

Evidence for a Roman conduit was discovered during excavations behind Wadham House, High West Street, Dorchester in 1968. This enormous conduit of probable late 1st century date was built alongside a N-S street of similar date at the east end of the trench. It had been cut to a depth of c. 4m. into the solid chalk and was 1.15m wide at the bottom with a lining of roughly dressed limestone blocks surviving on each side to a height of c. 0.5m. The bottom was lined with roof tiles laid in pairs on a base of red and white mottled clay laid on the natural chalk. Two Purbeck limestone slabs in the base may originally have been cap stones. The conduit was probably originally lined with masonry for its full depth. No dating evidence was recovered and the suggested late 1st century date for the conduit is dependant on the fact that it appears to be the continuation of a conduit seen to the north of trench in 1938, in which a worn coin of Vespasian was found. The conduit was robbed, and fills of chalk and ash accumulated in it, during the second half of the second century. Silt formed over this, and a later re-metalling of the road surface was laid on top of the silt.

Found during the excavation of a 27.5m x 3m trench during December and January 1968-9, dug in advance of the redevelopment of the back garden of Wadham House, 50 High West Street, Dorchester. The Excavation has been published as part of the ‘Dorchester Excavations Volume 1’ (Dorset Natural History and Archaeological Society Monograph 2) (1).

This enormous conduit of probable late 1st century date was built alongside a N-S street of similar date at the east end of the trench. It had been cut to a depth of c. 4m. into the solid chalk and was 1.15m wide at the bottom with a lining of roughly dressed limestone blocks surviving on each side to a height of c. 0.5m. The bottom was lined with roof tiles laid in pairs on a base of red and white mottled clay laid on the natural chalk. Two Purbeck limestone slabs in the base may originally have been cap stones. The conduit was probably originally lined with masonry for its full depth. The outward sloping profile of the cut has been weathered and may have originally been vertical.

No dating evidence was recovered and the suggested late 1st century date for the conduit is dependant on the fact that it appears to be the continuation of a conduit seen to the north of trench in 1938, in which a worn coin of Vespasian was found. At some stage in the mid 2nd century the upper masonry of the conduit was removed, leaving an open ragged robber trench. Following this a mixed fill of black brown ash and sandy buff soil was tipped into the trench to a depth of 0.65m. above this was a further layer of tipped weathered chalk up to 0.5m thick. A considerable thickness of ash and burnt material then accumulated containing late 2nd century pottery. A layer of grey green silty soil accumulated above this, also containing late 2nd century material. This may have taken a considerable time, after which the edge of the street was extended over the conduit fill.

<1> Draper, J, and Chaplin, C, 1982, Dorchester Excavations Volume 1: Excavations at Wadham House 1968; Dorchester Prison 1970, 1975 and 1978; and Glyde Path Road 1966, 3-26 (Monograph). SDO9690.

<2> National Record of the Historic Environment, 1410290 (Digital archive). SDO14739.

Record last edited

Aug 22 2024 7:31PM