H M Prison Dartmoor: Reservoir, with retaining wall, conduit head and nearby tank

Reservoir, constructed circa 1806-9. Restored in 2013.

MATERIALS: granite ashlar.

DESCRIPTION: the reservoir is a long, slightly irregular elliptical feature, sited to the west of the prison, on a north-south alignment. The reservoir is lined with granite ashlar, in blocks of unequal size. To the east of the reservoir is a circular unroofed conduit head with a central doorway facing the prison. This structure is of regularly-sized and coursed granite ashlar, with a tall plinth and a bull-nosed stringcourse beneath the plinth.

SUBSIDIARY FEATURES: a retaining wall supports the raised ground in which the reservoir and conduit head are set; this is of granite rubble with a capping of rock-faced granite with drafted margins, and with piers having pyramidal caps - the dressed granite of the capping and piers probably indicates a later-C19 phase of work.

Above the reservoir, a short distance to the north-west, is a circular tank lined with coursed granite, with dressed granite to the rim. This feature, is fed by a spring, appears on the 1884 Ordnance Survey, pre-dating the later covered reservoir to which it is now adjacent.