The Hanch Tunnel is a man-made tunnel that was constructed in the Triassic sandstone to the north and west of Lichfield in the 1850s.
When first constructed, the tunnel was connected to Minster and Stowe Pools, which served as storage reservoirs for use during times of water shortage. These connections are now blocked and there is believed to be no remaining connection between the tunnel and the pools.
The tunnel was also used to transport groundwater from Hanch Reservoir (now abandoned), and then from Seedy Mill boreholes, to Sandfields, where the water was abstracted and treated before being used to supply Lichfield.
Some time around 1996 I was able to go down the Hanch Tunnel, there is an entrance near to Becon Park. It was quite an interesting circular shaft about 20ft (7m) deep with a spiral staircase cut into the wall. You could look up the tunnel in both directions; I think it is about 5 km long.
There are a few pictures here by kind courtesy of an ex-employee of the water company.