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

occurs along the longitudinal centerline of the dam up to the crest of the emergency
spillway of the dam. For reservoirs created by excavation, or where the invert ofthe
outlet conduit is placed below the surface of the natural ground at its lowest point
beneath the dam, the jurisdictional height shall be measured from the invert ofthe
outlet at the longitudinal centerline of the embankment. Jurisdictional height is
defined in Rule 4.2.18. The State Engineer shall have final authority over
determination of the jurisdictional height of the dam.

4.2.6.2 "Non-jurisdictional Size Dam" is a dam creating a reservoir with a
capacity of 100 acre-feet or less and a surface area of 20 acres or less and with a
height measured as defined in Rule 4.2.6.1 and 4.2.18 of! 0 feet or less. Non-
jurisdictional size dams are regulated and subject to the authority of the State
Engineer consistent with sections 37-87-102 and 37-87-105 C.R.S.

4.2.6.3 "Minor Dam" is a jurisdictional size dam that does not exceed 20 feet in
jurisdictional height and/or 100 acre feet in capacity (see Figure I).

4.2.6.4 "Small Dam" is a dam with a jurisdictional height greater than 20 feet but
less than or equal to 50 feet and/or a reservoir capacity greater than 100 acre-feet,
but less than 4,000 acre-feet (see Figure I).

4.2.6.5 "Large Dam" is a dam greater than 50 feet in jurisdictional height, and/or
greater than 4,000 acre-feet in capacity (see Figure I).

4.2.6.6 "Diversion Dam" is a dam constructed for the purpose of diverting water
from a natural watercourse into a canal, tunnel, ditch, or pipeline that typically
impounds an insignificant volume of water, and for which the impacts of failure are
not a significant public safety hazard.

4.2.6.7 "Flood Control Dam" is a special purpose dam that is normally dry and has
an ungated outlet structure for the controlled release of water impounded during and
subsequent to a flood event. The jurisdictional size and classification of the dam are
determined using the height and capacity ofthe reservoir to the emergency spillway
elevation, or using the elevation of the maximum routed water surface elevation if
no emergency spillway is provided.

4.2.7 "Dam Failure Inundation Map" is a map depicting the area downstream from a dam
that would reasonably be expected to be flooded in the event of a failure of the dam.

4.2.8 "Day" as used in these Rules means a calendar day. For computation of time periods
as used in these Rules, Colorado Rules of Civil Procedure 6(a) shall apply.

4.2.9 "Emergency Action Plan (EAP)" is a written document prepared by the dam owner,
describing a detailed plan of actions for response to emergency or unusual events, including
alerting and warning emergency officials in the event of a potential or imminent dam failure
or other emergency related to the safety of the dam and public.

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