The sea defences and drainage point (the main drainage point from the Wentlooge levels) at this location have undergone significant remodelling in the 20th century. The 1st edition OS map dating from 1883 Ordnance shows water from the Wentlooge levels channelled into reens (drainage ditches behind the defences) which converge on the traditional channel of Gout Fawr Pill, ending in a sluice in the embankment. The sea defences define the edge of the pill on 3-sides creating a prototype harbour (see NPRN 519310) measuring some 420m from end to end. The main sluice (sluice 1) was located at Gout Fawr, in northwestern corner adjacent to a disused limekiln (NPRN 519311). A second sluice (sluice 2) is shown exiting into Gout Fawr Pill from the southeast at the New Quay Gout. A plaque on the modern southeast embankment commemorating the opening of Peterstone Gout in 1960 suggests a date for the remodelling which enclosed the old area of the harbour/dock, creating a reservoir. The new embankment has a sluice towards its northeastern end, at Peterstone Gout. The site was visited by Gwent-Glamorgan Archaeological Trust staff in 2005 during their Waterfronts in Southeast Wales project. They identified a third sluice. Sluice 3 is located in the southwest embankment of the water retainment reservoir, but is not depicted on any Ordnance Survey map so its date is unknown.

Sources include:
Gwent-Glamorgan Archaeological Trust, 2012, Historic Environment Record
Ordnance Survey, 1883, 1st edition 25" Landmark
Ordnance Survey, 2012, Mastermap

Maritime Officer, RCAHMW, January 2011.