Tunnels | Canal & River TrustThe construction of tunnels was one of the most difficult tasks facing canal engineers.The construction of tunnels was one of the most difficult tasks faced by early canal engineers. Tunnels were traditionally built by plotting out the route across the hilltop and then sinking down several shafts. Miners would then begin digging in both https://canalrivertrust.org.uk/directory/7/harecastle-tunnel