Historic building, ground penetrating radar and laser scan survey of structure unexpectedly discovered during groundworks. Structure turned out to be an underground reservoir related to a Grade 1 Listed Building - Starcross Pumping House which was part of the South Devon Railway (SDR) constructed in the mid-1880s by Isambard Kingdom Brunel. The Starcross Pumping House stands on the east side of The Strand, Starcross, near Exeter. The car park with the underground reservoir lies south of the Pumping House, centred on OS NGR 297753 081742. Due to the confined access to the reservoir, consisting of a single circular opening, the survey used a combination of Ground Penetrating Radar (GPR), terrestrial laser scanning and photography to produce a descriptive record of the reservoir. The reservoir, as recorded, consists of a large rectangular feature consisting of two stone-built arched chambers covering an area of 318 square metres. These are separated by a central stone dividing wall with a series of ten open arches. No definitive evidence was found for a pumping system, but associated features including possible iron ladder fittings may relate to this and circular holes, most now covered for probable venting were also recorded. Substantially built with strong thick stone walls, the reservoir at the time of recording was still holding a significant volume of water.