Portal:London transport/Selected articles/66
The Blackwall Rock was a reef in the River Thames near Blackwall in East London at short distance upstream from Blackwall Stairs and between the entrances of the West and East India Docks. The rock provided a useful shelter for moored vessels, but also proved a hazardous obstruction to river navigation as it was sometimes less than 3 feet (1 m) below the surface at low tide.
The entrance to the West India Docks, just to the south-west of the rock, was substantially obstructed by the reef upon the docks' opening in 1802. In 1803, Robert Edington surveyed the rock estimated its dimensions as 600 by 150 feet (183 m × 46 m). An 1846 report by the Tidal Harbours Commission described it as an outcrop of plum-pudding stone.
Early attempts to break the rock with explosives were largely unsuccessful. William Jessop was engaged by Trinity House to undertake the rock's removal which he did using a chisel, operated from a barge much as with pile driving. This method successfully reduced the height of the rock by 15 feet (4.6 m), after which a cylindrical coffer dam was employed to allow workers' access to remove rubble.