This structure was completely below ground with raised entrances that would have been level with the surface at the time of construction. Subsequent development raised ground-level, totally obscuring any trace of the structure. Once fully exposed, it was observed that the shelter was roughly aligned north to south. The north entrance was 55cm above the roof of the chamber and measured 6.55m long by 1m wide. The entrance was sealed by a cap of corrugated iron covered in concrete, which sat on a recessed lip within the entrance walls, 5cm deep on each side. This appeared to be part of the original construction and is an indication that the shelters had some form of door or hatch. The south entrance was 45cm above the roof of the chamber and measured 6.45m long by 1m wide. The concrete-covered corrugated iron cap sat on an identical-sized lip to that of the north entrance. Both entrances
descended eleven steps to identical corridors that terminated in a recess (87cm deep). The width of this corridor was 70cm, indicating that the walls were 15cm thick. Directly above the recess was a centrally-positioned circular hole (10cm in diameter) in the roof. This is interpreted as either an air vent or an exhaust vent for waste gases. The floor was poured concrete with five 60cm by 46cm concrete slabs set into it. A white painted number (46) was observed on a facing panel of each entrance.
The central chamber measured externally 7.4m by 1.85m by 2.45m high with an internal measurement of 1.54m at its widest point. The chamber was of unpainted concrete and had a bench extending along the external wall on either side. These benches were 46cm high by 35cm deep and were formed of the same concrete as the entire structure. Evidence of shuttering is clear and the construction technique is nearly identical to that of the shelters on Area J1. Here the facets above the benches were identical until the highest central panel, where a 20cm-wide by 4cm-deep recess was inserted. However, this did not significantly alter the ovoid shape of the chamber when viewed in section. Sixteen 60cm by 46cm rectangular slabs extended down the centre of the chamber. Three more exhaust vents were located at equal intervals within the roof.
Both the recess and the internal doorways had the remains of iron hinges and the internal door had the remains of an iron latch, indicating that doors were at one time present. Iron hook latches were affixed to the external wall of the entrance approximately 1m off the floor. <1>