Prior to the creation of William Jessop’s Floating Harbour in 1809, the River Avon flowed through where Underfall Yard now stands.
The construction of Cumberland Basin and the New Cut meant that an island was formed between where the river was diverted, to Bathurst Basin at Redcliffe. This island became known as Spike Island.
Jessop’s plan included an ‘Overfall’ Dam to allow excess water in the Floating Harbour to flow over into the New Cut, but by the 1830s the harbour was becoming badly silted up.
Although Jessop had included sluices with his Overfall Dam, the main method of clearing the silt out was to drain the harbour and remove it by hand, which was less than ideal to say the least.
Isambard Kingdom Brunel was brought in to make improvements to both Cumberland Basin and the Overfall Dam, and for the Overfall Dam he recommended developing Jessop’s sluices further and using dredger boats to remove the silt.
He devised an Underfall system where three shallow sluices could be used in a way that would control the harbour water level according to the tide and weather conditions, and a fourth ‘deep scouring’ sluice which could be opened at low tide when a powerful undertow (undercurrent) would suck the silt into the New Cut to be carried away by the next tide.
This Underfall system is still in use today, although a more modern system of dredging is used.
At the time of the Floating Harbour’s construction, maintenance of the docks was carried out in different workshops around the city, but in the 1880s it was decided to merge them all into a single maintenance facility at Underfall Yard and most of the buildings that survive were built between 1880 and 1890 under the supervision of Docks Engineer, John Ward Girdlestone.
One of these buildings was the Hydraulic Power House that replaced Thomas Howard’s original Pump House (now a pub) that operated next to the Junction Swing Bridge.
The Power House at Underfall was originally steam powered (which is why it has a chimney), but in 1907 a hydraulic system was introduced which pumped water from the harbour and used high pressure pumps and accumulators to power the lock gates, sluices, swing bridges and cranes throughout the harbour.
In 1975 the City Docks closed to commercial shipping and the buildings and Patent Slip at Underfall Yard fell into disrepair.
In 1994 the Underfall Yard Trust was established whose aim was to restore and preserve the buildings and surroundings in keeping with modern day requirements.
In 2016 the Hydraulic Power House became a visitor centre, and pumping demonstrations take place three times a week, although since 2010 it operates using an oil hydraulic system.
There’s also a large photographic interactive map which seems to take up most of the Power House, but is an excellent source of information regarding the layout of the Floating Harbour and its relevant components.
Even though the set-up is all very rustic and, in its infancy, I like it as it is, and the bacon rolls from the Pickle Cafe are “Gert Lush”.
There is even a Human Accumulator to give you an idea how the system works, but the real ones can be seen outside – or at least one of them can. The original is inside the red brick tower but was difficult to service, so an external one was added in 1954. If you’re around on a day that the pumps are being demonstrated then you’ll be able to see this accumulator in action.
The other buildings around the yard that once employed engineers, shipwrights, blacksmiths, divers, electricians, plumbers and others are now used by today’s maritime business and not normally open to the public, but you’re still free to wander around, and the Patent Slip is on full view to the public where boat maintenance is still carried out, much as it would have done 130 years ago.