Great County Adit facts for kids
The Great County Adit was a huge system of underground tunnels. It helped drain water from over 100 tin and copper mines in the Gwennap area of Cornwall, in the United Kingdom. Building started in 1748. This amazing tunnel system eventually stretched for more than 40 miles (64 km) (about 64 kilometers). It drained water from mines at an average depth of 80–100 metres (260–330 ft) (about 260-330 feet).
Contents
Building a Giant Drain
The idea for the Great County Adit came from John Williams. He was born in 1714 and managed the Poldice mine in Scorrier. Work on the adit began in 1748. It took many years to build. The adit finally reached Poldice mine in the late 1760s.
Expanding the Network
By 1778, the adit had grown even longer. It passed Wheal Busy and reached Wheal Peevor. Another part, called the Consols Adit, was dug west in the 1770s and 1780s. This part helped drain the Consolidated Mines and United Mines. By 1792, a branch from Poldice mine had also reached Wheal Unity.
How the Adit Worked
The main entrance, or portal, of the adit is in the Carnon Valley. This is near the small village of Twelveheads. In 1839, when it was probably at its busiest, the adit released a huge amount of water. It discharged over 14.5 million gallons (about 66 million litres) of water every single day into the Carnon River.
At that time, the Great County Adit used more steam engines to pump water into it than all of continental Europe and America combined! This shows how important and advanced this system was for mining.
The River's Journey
The Carnon River flows into Restronguet Creek. This creek is a tidal arm of the Carrick Roads, which is upstream from Falmouth. In the winter of 1876, there were major floods. These floods washed large amounts of waste rock and mud into the upper part of Restronguet Creek. This permanently damaged the river, making it hard for boats to reach the upper docks at Devoran.
The Adit Today
Even though all the mines that the Great County Adit served have now closed, the adit is still working. It is not maintained anymore, but it continues to drain water from many of the old underground mine tunnels. For example, in the summer of 1980, it was still draining 500,000 gallons of water every day.
