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

Small - General Storm East
6,000 - 12,000 ft MSL .8PMP .50 (.8 PMP)
Above 12,000 ft MSL .7PMP .50 (.7 PMP)
General Storm West
5,000 - 8,000 ft MSL .8PMP .50 (.8 PMP)
Above 8,000 ft MSL .7PMP .50 (.7 PMP)
Local Storm
10,000 - 11,500 ft MSL .8PMP .50 (.8 PMP)
11,501 - 13,000 ft MSL .7PMP .50 (.7 PMP)
Above 13,000 ft MSL .6PMP .50 (.6 PMP)
Minor - General Storm East
6,000 - 12,000 ft MSL .50 (.8 PMP)
Above 12,000 ft MSL .50 (.7 PMP)
General Storm West
5,000 - 8,000 ft MSL .50 (.8 PMP)
Above 8,000 ft MSL .50 (.7 PMP)
Local Storm
10,000 - 1I,500 ft MSL .50 (.8 PMP)
11,501 - 13,000 ft MSL .50 (.7 PMP)
Above 13,000 ft MSL .50 (.6 PMP)

5.5.8 The IDF shall be determined considering basin size, the altitude of the basin, various
soil permeabilities, the various vegetative covers, and other factors related to the routing of
the storm event. Historical precipitation data of the National Weather Service may be used
for determining the IDF provided applicable stochastic procedures are used as outlined in
the National Weather Service NOAA Atlas #2 "Precipitation-Frequency Atlas ofthe
Western United States" Volume lII-Colorado, U.S. Department of Commerce, NOAA,
National Weather Service, Silver Springs, Maryland, 1973, or other methods approved by
the State Engineer.

5.5.9 The National Weather Service, NOAA, Atlas #2 "Precipitation-Frequency Atlas of the
Western United States" Volume III-Colorado, U.S. Department of Commerce, NOAA,
National Weather Service, Silver Springs, Maryland, 1973, maybe used for determining the
precipitation for a lOa-year and more frequent rainstorm events for the purpose of
calculating the magnitude of the resulting flooding.

5.5.10 The most current Probable Maximum Precipitation estimates developed by the
Office of Hydrology, National Weather Service, NOAA Hydrometeorological Report Series
may be used for determining the precipitation for a probable maximum precipitation event
for the purpose of calculating the magnitude of the resulting flooding. Currently,
Hydrometeorological Reports 52 and 55A are applicable for drainage basin located to the
east of the Continental Divide and Hydrometeorological Report 49 for drainage basin west
of the Continental Divide.

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