A short video taken at shaft number three.
A continuous drainage culvert between the tracks takes water to the tunnel's lowest point under Sudbrook Pumping Station, where it is pumped to the surface.Should ignited petroleum run into the culvert in the event of derailment of a tank wagon, special arrangements are in place to prevent passenger trains entering while hazardous liquid loads are being worked through.[4]
At Sudbrook Pumping Station, an iron ladder descends in the shaft of the water pumping main and ventilation air is pumped in. The GWR ventilation arrangement was to extract air at Sudbrook, but the exhaust from steam trains caused premature corrosion of the fan mechanism. When the Cornish pumping engines were replaced in the 1960s, the draughting was reversed so that atmospheric air is pumped into the tunnel exhausting at the tunnel mouths.[citation needed]
About 50 million litres of water per day of fresh water are pumped from the tunnel and released into the River Severn.