R655. Natural Resources, Water Rights.
R655-11. Requirements for the Design, Construction
and Abandonment of Dams.
R655-11-7C. Outlet Details.
A. All outlets shall
have a trash rack to prevent clogging.
B. All outlets connected
directly to a downstream pipeline shall have an emergency bypass valve.
C. All outlets shall
have a suitable energy dissipator at the discharge end to prevent erosion of
the downstream channel.
D. All outlets will be
placed on a concrete cradle or encased in concrete unless specifically exempted
by the State Engineer in writing.
E. All outlets, with the
exception of ungated outlets, shall have an operating gate or a guard gate on
the upstream end.
F. All outlets shall
have seepage control measures to reduce the potential for piping along the
conduit. Common methods may include
locating the outlet conduit in bedrock and installing a conduit filter drain to
intercept seepage.
G. Outlets encased in
concrete should have battered sides to facilitate compaction against the
encasement.
H. Every attempt should
be made to locate the outlet on bedrock or consolidated materials. In the event this is not possible,
consideration should be given to articulating the outlet to allow for
settlement.
I. Outlet gates and valves
can be either mechanically or hydraulically operated. In either case the hydraulic lines or mechanical stems must be
adequately protected from debris, wave action, settlement, and ice damage. Buried stems should be encased in an
oil-filled pipe supported on pedestals.
No catwalks or similar access structures will be allowed on reservoirs
where freezing occurs or significant floating debris is present. All outlets which are operated with
electrical equipment must have back-up generating capability or a manual bypass
system capable of being operated in a reasonable amount of time.
J. All outlets shall be
properly vented to avoid cavitation, surging, and reservoir vortexes. On low head dams adequate ventilation may
naturally occur through the conduit if a free water surface is maintained. In most cases a vent pipe and air manifold
around the perimeter of the conduit immediately downstream of the gate will be
required. The air supply lines should
be conservatively sized for the anticipated flows and protected in the same
manner as the outlet control lines or stems.
K. All operators and
supporting equipment for outlet controls should be properly protected and
secured. Particular attention needs to
be given to protection from vandals and unauthorized operation. All outlet controls should be clearly marked
as to which way the gates and valves operate so that overloading of a closed
gate or valve should not occur.
L. Outlet controls
should be accessible when the spillways are in use.
KEY: dams, earthquakes, floods, reservoirs
November 29, 2001
Notice of
Continuation July 12, 2001
73-5a