Ventilation Shaft

The 1932 Valve House is a rectangular walled enclosure that includes the 1856 Valve House, the 1932 Valve House, and a circa 1890 'birdcage' ventilation shaft leading to a junction chamber. Security covers for openings and vents were added in 2007.

The 1856 Valve House is a single-bay, flat-roofed structure designed in an Italianate style. It features deep eaves supported by a battered podium, which is set into sloping ground. The building is constructed from coursed, bull-faced sandstone with ashlar dressings, and includes a base course, prominent long and short quoins, and window margins. The front has a bipartite window, while there is a door at the rear (replaced in 2007) and single windows on the sides. The fixed iron windows have an ornamental glazing pattern. Inside, there is a 19th-century cast-iron operating mechanism.

The 1932 Valve House is also a single-bay, flat-roofed structure but features a crenellated design. Like the earlier valve house, it is made of coursed, bull-faced sandstone with ashlar dressings and includes a base course and narrow ashlar window margins. It has a metal door from 2007 with a lintel dated 1932 on the north side, and windows on the other elevations. There are stone steps at the rear of the podium, and the fixed iron windows have diamond pane glazing. The structure also has stone steps, a retaining wall, and railings leading to the subterranean 1890 chamber. Inside, there is a cast-iron operating mechanism for the upper and lower chambers.

The ventilation shaft, built in 1890, is a circular enclosure made of snecked, bull-faced sandstone, featuring an access gate and a domed wrought-iron 'birdcage' top with a projecting cope.

Surrounding the site is a battered random rubble boundary wall topped with a rounded cope, which includes two iron gates to the south and stone steps leading to the pedestrian gate.