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Harecastle Tunnel is on the Trent & Mersey Canal at Kidsgrove. There are actually two separate, parallel, tunnels named Brindley (2,880 yards or 2,633 metres) and the later Telford (2,926 yards or 2,675 metres) after the engineers that constructed them.
The Brindley tunnel was constructed by James Brindley between 1770 and 1777, it was closed after a partial collapse in 1914.
The Telford Tunnel is only wide enough to carry traffic in one direction at a time and boats are sent through in groups, alternating northbound and southbound. An air extraction fan-house has been built around the south portal to aid ventilation in the tunnel.
It takes 45 minutes to travel through the tunnel.
The rusty colour of the water is caused by water entering the canal from the Brindley tunnel which contains iron oxide, there are proposals to install filtering (possibly using reed beds) at the northern portal.