Drift Reservoir, a 1,200 yards long and 65 acres reservoir in Cornwall, was completed for the West Cornwall Water Board in 1961 after having been amended during excavations due to the discovery of rotting granite.
Drift Reservoir is a reservoir in Cornwall, England, UK, just north of the village of Drift and west of Penzance. The reservoir is 1,200 yards (1,100 m) long and covers 65 acres (26 ha). It was completed for the West Cornwall Water Board in 1961. The original design had to be amended during excavations when rotting granite was found. 
