The Impound Station is a key infrastructure facility serving to pump water from the River Thames for two reasons:
- To maintain the water level within the docks between its upper and lower limits. Water is lost within the docks through seepage, evaporation and lock movements.
- To allow water level adjustments to be made to enable inspection of the dock walls and the false quays
The station was built in 1912 and originally housed 3 steam driven pumps. Four electrically powered pumps replaced these in 1954. The pumps were changed again in 2003 for the electrically powered pumps we see today.
The station pumps water from the River Thames at Gallions Reach, where a screening, intake structure and cover flap are situated. This is owned by the Environment Agency as part of the flood prevention scheme. This is connected via a 4m x 5.5m intake culvert to the huge wet well below the station. The building sits above this well and houses the 4 pump sets, electrical intake switchgear, a motor control centre, low voltage switchboard and a control room. Outside the building, located on the east side, there are three transformers in a fenced compound and to the west are the four pump discharge pipes with gantry access incorporated over the top.
The four pumps each weigh 17 tonnes, and each have a flow capacity of 7150 litres a second through 70-inch pipes. To put this into perspective, with all four pumps running they would fill an Olympic swimming pool in 1.5 minutes. The pumps draw water from the inlet culvert and discharge, via individual pipes, directly into the adjacent dock.
In July 1999 London Development Agency (LDA) took over ownership and responsibility for the station from English Partnerships (EP) who had acquired it from the London Docklands Development Corporation (LDDC) in April 1998. The station, its operation and maintenance is leased to the Royal Docks Management Authority (RoDMA).
Although the use of the docks has changed significantly over the years, this capability has met all the changing requirements.
Also, within the Impound Station there is a Morris overhead gantry crane which runs the required length of the station to encompass all four pumps.
The crane is powered by 415 volts, 3 phase, 50 Hertz and is certified to a Safe Working Load of 10t with a 6-metre hoist.
There is a uniqueness with this crane in that it is not operated, as modern cranes are, from an electrical pendant. The original manually operated draw cords operate the various switches on the gantry motor and gearbox, which raise/lower and change speeds of the hoist. The crane is also traversed along its gantry by a manually operated pull chain. It has been stated by Konecranes, who conduct the servicing, that this is one of only three of this type still operational in the UK. The crane was manufactured and fitted in 1960.