 The penstocks are a pair of tunnels, 260 metres (850 ft) long and inclined at 56°from the horizontal with a 5.3 metres (17 ft) diameter, which then bifurcate into four steel lined 190 metres (620 ft) long, 2.5 metres (8 ft 2 in) diameter shafts. The penstocks underwent a major inspection and refurbishment in 2003.
