R655. Natural Resources, Water Rights.
R655-11. Requirements for the Design, Construction
and Abandonment of Dams.
R655-11-6E. Internal Drainage.
A. All underdrains and
collection pipes shall be constructed using non-corrodible materials capable of
withstanding the anticipated loads.
B. Underdrains and
collection pipes should be designed to conduct flows several times larger than
anticipated. All pipes within the dam
which are not easily accessible shall have a minimum diameter of six inches.
C. All internal drain
pipes should be enveloped with free draining material, meeting filter
requirements with adjacent zones.
D. Where multiple pipes
are used to conduct drainage from internal portions of the dam, they should be
carried to the downstream toe or gallery separately without intervening
connections or manifold systems. If the
drain pipes are connected at their termination points, manholes should be
provided to facilitate observation and measurement of the separate drain lines.
E. All underdrains and
collection pipes should have provisions for measuring discharges in manholes or
at their discharge points. If the
anticipated discharge is in excess of 10 gallons per minute (gpm), a weir or
other suitable measuring device should be provided. If the anticipated flows are less than 10 gpm, provisions should
be made so the water can be discharged freely into a vessel 1.5 feet high and
one foot in diameter.
F. All exposed
underdrain and collection pipes shall have an appropriate rodent screen
attached.
G. All underdrains and
collection pipes should be cleaned out prior to the first filling of the
reservoir.
H. All seepage
collection systems must include a collection pipe to discharge flows.
I. All internal drains must
have a minimum cover of 3 feet of impermeable material to eliminate the
collection of surface waters.
KEY: dams, earthquakes, floods, reservoirs
November 29, 2001
Notice of
Continuation July 12, 2001
73-5a