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

4.2.2 "Appurtenant Structure" means components other than the material structure of the
dam itself such as the outlet works and controls, spillways and controls, access structures,
bridges, and other systems directly related to the safe operation of a dam.

4.2.3 "Breach Order" is an order issued by the State Engineer, or his designee, for
removal of all or part of a dam to permanently reduce the maximum storage level, minimize
the risk of failure and/or the potential of damage downstream due to the failure of the dam.

4.2.4 "Capacity" is the volume of water a reservoir is capable of impounding at the high-
water line, expressed in acre-feet. Dead storage below the natural surface of the ground or
low level outlet is generally excluded.

4.2.5 "Hazard Classification of a Dam" is the placement of a dam into one offour
categories based on the hazard potential derived from an evaluation of the probable
incremental adverse consequences due to failure or improper operation of the dam.
Conditions for evaluation are absent flooding, and the reservoir is assumed to be full to the
high water line. The hazard potential classification does not reflect the current condition of
the dam with regard to safety, structural integrity, or flood routing capacity.

4.2.5.1 "High Hazard" dam is a dam for which loss of human life is expected to
result from failure of the dam. Designated recreational sites located downstream
within the bounds of possible inundation should also be evaluated for potential loss
of human life.

4.2.5.2 "Significant Hazard" dam is a dam for which significant damage is
expected to occur, but no loss of human life is expected from failure of the dam.
Significant damage is defined as damage to structures where people generally live,
work, or recreate, or public or private facilities. Significant damage is determined to
be damage sufficient to render structures or facilities uninhabitable or inoperable.

4.2.5.3 "Low Hazard" dam is a dam for which loss of human life is not expected,
and significant damage to structures and public facilities as defined for a
"Significant Hazard" dam is not expected to result from failure of the dam.

4.2.5.4 "No Public Hazard (NPH)" dam is a dam for which no loss of human life
is expected, and which damage only to the dam owner's property wiII result from
failure of the dam.

4.2.6 "Dam" means a man-made barrier, together with appurtenant structures, constructed
above the natural surface of the ground for the purpose of impounding water. Plood control
and storm runoff detention dams are included.

4.2.6.1 "Jurisdictional Size Dam" is a dam creating a reservoir with a capacity of
more than 100 acre- feet, or creates a reservoir with a surface area in excess of 20
acres at the high-water line, or exceeds 10 feet in height measured vertically from
the elevation ofthe lowest point of the natural surface ofthe ground where that point

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