Wyoming Administrative Code › Agency 037 - Engineer, State › Sub-Agency 0006 - Surface Water › Chapter 5 - RESERVOIRS › Section 5-1 - Reservoirs or Darns

Current through July 13, 2024
a. A permit from
				the State Engineer is required before commencing construction of any dam or
				reservoir involving the storage or impoundment of water in Wyoming. Maps or
				plans must be submitted with the application for a permit to construct such a
				dam. See Section
				1(c) of Chapter VI 11, page
				55, for special conditions applicable to maps for applications for certain
				stock reservoirs, fishing preserve reservoirs, and floodwater detention
				reservoirs; additional details are provided in Chapter VI of this
				Manual.
b. Special requirements for
				plans of dams include:
(1) A profile of the
				damsite along center line, and a maximum cross-section of the proposed
				dam.
(2) The outlet works and
				spillway in detail. The spillway cross-section must be shown. A computation of
				capacity and all necessary data used must be included.
(3) The scale used on any part of the map or
				plans should be sufficiently large to reflect all important details. Reservoir
				contour maps snail normally be drawn to a scale of 1" = 400' or larger. When
				the maximum length or width of the reservoir basin is more than 2 miles, the
				scale of the reservoir contour map may be reduced to not less than 1" = 1000'
				providing that all necessary detail is clearly shown. Profiles shall be drawn
				to a longitudinal scale of 1" 200' or larger. Cross-section plans shall be on a
				scale of not less than 1" 20'. Detailed plans including plans of outlet works
				and other structures, shall be on a scale of not less than 1" = 4'. Important
				dimensions must be shown on all plans of structures.
(4) For earth dams, the slope must not be
				less than 3 to 1 for the front or water side and 2 to 1 for the back side
				unless conditions justify steeper slopes. In this case, engineering data must
				be submitted in support of steeper slopes than these maximums. Special
				conditions may require flatter slopes. The width on top shall be at least 1/5
				of the height plus 4 feet, and in no case less than 3 feet for dams 10 feet or
				more in height. A minimum freeboard (from the top of the dam to the bottom of
				the spillway) of 5 feet is ordinarily required on all earth dams. This minimum
				may be reduced, but only when specifically requested and prior approval is
				granted by the State Engineer. Justification for reducing the freeboard
				requirement below 5 feet must be submitted along with the application and
				should include information on the conditions, size and characteristics of the
				drainage area above the reservoir, the location of buildings, roads and other
				structures downstream from the dam, the effect of wave action on the face of
				the dam at maximum water level, and any other information concerning the
				conditions at the -Jam site.
(5)
				For reservoirs with a dam height greater than 20 feet or reservoirs with a
				storage capacity greater than 50 acre-feet or reservoirs located in an area
				where extensive property damage or loss of life Eight result from over-topping
				or failure of the dam, the spillway shall have sufficient capacity to pass the
				flood flow for a projected 100 year storm. The design of the spillway shall he
				such that a minimum of 11/2 feet of freeboard, between the top of the dam and
				the maximum water level in the spillway, is maintained, If the design indicates
				erosive velocities in the spillway channel, a protective lining shall be added
				or redesign of the Spillway shall be marie. The State Engineer may require
				additional freeboard and/or spillway capacity if, in his judgment, it is
				necessary.
(6) The State Engineer
				may require detailed construction plans and specifications for structures,
				along with computations governing the design thereof.
(7) A capacity table showing the capacity of
				the proposed reservoir must be shown on the reservoir filing map. See sample
				map on page 65.