BOARD01548

• Board Meeting Date: 1/25/2005
• Description: Proposed Revisions to the Rules and Regulations for Dam Safety and Dam Construction
• Board Meetings - Doc Type: Memo

4.2.19 "Normal Water Line" means the elevation of the water at the crest of the principle
or service spillway.

4.2.20 "One-hundred-year Flood" means a potential flood having a magnitude (peak
discharge) whieh is expected to be equaled or exceeded on the average once during any
one-hundred-year period (recurrence interval) and has a one percent chance of being
equaled or exceeded during any year (0.01 exceedance probability). The terms "one-
hundred-year flood" and "one percent chance flood" are synonymous.

4.2.21 "Outlet" means a conduit (usually regulated by gates or valves) used for controlled
or regulated releases of impounded water from the reservoir.

4.2.22 "Owner" means any person, private or non-profit company, special district, federal,
state, or local government agency, or any other entity in direct routine control of a dam and
reservoir, and/or directly involved in the physical operation and maintenance of a dam, or
proposes to construct a dam. Changes in ownership shall be immediately filed with the
State Engineer.

4.2.23 "Probable Maximum Precipitation (PMP)" means the theoretically greatest depth
of precipitation for a given duration that is physically possible over a drainage basin at any
specific time of year. The PMP values are normally determined from the appropriate
Hydrometeorological Report (HMR) (HMR 49 for west of the continental divide, HMR 52
for the eastern plains and HMR 55A for the Front Range). The I DO-year, 50-year, and 25-
year events are normally determined from the National Weather Service NOAA Atlas #2
"Precipitation-Frequency Atlas ofthe Western United States" Volume III-Colorado, U.S.
Department of Commerce, NOAA, National Weather Service, Silver Springs, Maryland,
1973, (later amendments, editions or subsequent publications not included).

4.2.24 "Plans" means all the necessary drawings, cross-sections, tables, notes, maps and
other information necessary to accompany the project specifications for design review and
approval and construction observation and approval.

4.2.25 "Reservoir" means a body of water impounded by a dam.

4.2.26 "Restriction Order" means an order issued by the State Engineer to limit the
maximum water surface elevation of a reservoir as an interim measure to immediately
reduce the risk of failure until investigations of a problem can be performed or structural
modifications can be made to repair the problem or breach the dam.

4.2.27 "Routing Capacity" means the capability of a reservoir and spillway system to
attenuate flood inflows, and is calculated as the sum of the spillway discharge(s) and
surcharge storage for a specific time increment, expressed in acre- feet.

4.2.28 "Safety Inspection" means an evaluation by an engineer to be used by the State
Engineer in determining the reservoir's safe storage level. The safety inspection includes,

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