Sloping down to the Crocodile Pool at a low gradient (1:685), The
Tailrace Tunnel was designed to operate normally under
freeflow conditions, but can also be submerged in times of severe
flooding. The tunnel outfall is set roughly 7m below river level.
Favourable rock conditions enabled the use of shotcrete for the
roof, but the wall and invert were finished off with concrete. the
outfall structure, at the tunnel portal, provides for the stoplog
gates, the piers, an access bridge and the associated stoplog
storage sheds. Access in the sidewall provides for the installation
of pumps for draining the tailrace behind the stoplogs.
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