Current through Register Vol. 35, No. 6, March 26, 2024
Unless defined below or in a specific section of these
regulations, all other words used herein shall be given their customary and
accepted meaning.
A. Terms starting
with the letter 'A' are defined as follows:
(1) Abutment: That part of the valley side
against which the dam is constructed. The left and right abutments of dams are
defined with the observer viewing the dam looking in the downstream
direction.
(2) Aesthetic fill:
Cosmetic fill added to the downstream slope of a dam that is not required to
address the safe design. Aesthetic fill shall not be considered when
determining the properties of the dam for the purposes of evaluating the
jurisdictional status and shall not be used to support the safe
design.
(3) Alteration,
modification, repair, rehabilitation or enlargement of an existing dam: To
change from the state engineer accepted construction drawings and
specifications or current condition.
(4) Appurtenant structure: Auxiliary features
of a dam such as outlets, spillways, access structures, tunnels and related
housing at a dam.
(5) ASTM:
Standards promulgated by ASTM international for testing the properties of
materials. Methods cited in these regulations include laboratory compaction
characteristics of soils.
B. Terms starting with the letter 'B' are
defined as follows: Breach: An opening through a dam or spillway that is
capable of draining a portion of the reservoir or the entire reservoir. A
controlled breach is a constructed opening. An uncontrolled breach is an
unintentional discharge from the reservoir.
C. Terms starting with the letter 'C' are
defined as follows:
(1) Consequences of
failure: Potential loss of life or property damage downstream of a dam caused
by waters released at the dam or by waters released by partial or complete
failure of dam; includes effects of landslides upstream of the dam on property
located around the reservoir.
(2)
Crest width: The thickness or width of a dam at the crest level (excluding
corbels or parapets). In general, the term thickness is used for gravity and
arch dams and width is used for other dams.
D. Terms starting with the letter 'D' are
defined as follows:
(1) Dam: A man-made
barrier constructed across a watercourse or off-channel for the purpose of
storage, control or diversion of water.
(a)
Jurisdictional dam: A dam 25 feet or greater in height, which impounds more
than 15 acre-feet of water or a dam that impounds 50 acre-feet or more of water
and is 6 feet or greater in height. For purposes of these regulations,
reference to a dam means a jurisdictional dam unless otherwise noted. See
figure of jurisdictional dam size.
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(b) Non-jurisdictional dam: Any dam not
meeting the height and storage requirements of a jurisdictional dam. The state
engineer does not regulate the design, construction and operation of a
non-jurisdictional dam unless the dam is unsafe and there is a threat to life
or property, as determined by the state engineer. Waters impounded by a
non-jurisdictional dam may not be exempt from water right permit requirements;
therefore a separate state engineer water right permit for the water impounded
in the reservoir created by a non-jurisdictional dam may be required.
Non-jurisdictional dams shall meet the requirements of 19.26.2.15 NMAC unless
otherwise exempt. The structures listed below are considered non-jurisdictional
dams:
(i) Levee or diversion dike: A
structure where water flows parallel to the length of the levee or diversion
dike as determined by the state engineer.
(ii) Roadway embankment: A structure across a
watercourse designed for the sole purpose of supporting a roadbed or other
means of conveyance for transportation as determined by the state engineer;
where the area upstream has not been enlarged to increase flood storage; and
where the embankment is provided with an uncontrolled conduit of sufficient
capacity to satisfy requirements of the appropriate state or local
transportation authority. If no transportation authority has jurisdiction over
the structure, the current drainage design criteria of the New Mexico
department of transportation shall apply.
(2) Dam crest: The uppermost surface of a
dam, usually a road or walkway excluding any parapet wall, railing,
etc.
(3) Dam failure: The breakdown
of a dam, characterized by the uncontrolled release of impounded
water.
(4) Dam height: The vertical
distance from the lowest point on the downstream toe to the lowest point on the
dam crest.
(5) Dam incident: An
event at a dam that interrupts normal procedures and performance, affects the
safety of the dam or results in a potential loss of life or damage to
property.
E. Terms
starting with the letter 'E' are defined as follows:
(1) Earthquake: A sudden motion or trembling
of the earth caused by the abrupt release ofaccumulated stress along a fault.
(a) Operating basis earthquake: The
earthquake that can reasonably be expected to occur within the service life of
the dam or appurtenant structures.
(b) Maximum credible earthquake: The greatest
earthquake that can reasonably be expected to be generated by a specific source
on the basis of seismological and geological evidence.
(2) Evacuation map: A map prepared in
collaboration with local emergency managers defining the area to be evacuated
from a dam failure.
F.
Terms starting with the letter 'F' are defined as follows:
(1) Fetch: The straight-line distance between
the dam and farthest reservoir shore subject to wind forces. The fetch is one
of the factors used to calculate wave heights in a reservoir.
(2) Freeboard: The vertical distance between
the spillway crest and the lowest point of the dam crest not including
camber.
(3) Functional exercise: A
meeting in a conference room environment involving the dam owner and state and
local emergency personnel with responsibilities in the emergency action plan.
The exercise takes place in a stress-induced environment with time constraints
and involves simulation of a dam failure and other specific events. The
exercise is designed to evaluate both the internal capabilities and responses
of the dam owner and the workability of the information in the emergency action
plan used by emergency management officials.
G. Terms starting with the letter 'G' are
defined as follows: Geotextile: Any fabric or textile(natural or synthetic)
used as an engineering material in conjunction with soil, foundations or rock.
Geotextiles provide the following uses: drainage, filtration, separation of
materials, reinforcement, moisture barriers and erosion protection.
H. Terms starting with the letter 'H' are
defined as follows: High water line: The highest water level elevation in the
reservoir as determined from routing the spillway design flood or inflow design
flood.
I. Terms starting with the
letter 'I' are defined as follows:
(1)
Incremental impacts: Under a given flood, earthquake or other conditions, the
difference in impacts that would occur due to failure or misoperation of the
dam and appurtenant structures compared to those that would have occurred
without failure or misoperation of the dam and appurtenant
structures.
(2) Inundation map: A
map delineating the area that would be flooded by a particular flood
event.
J. Terms starting
with the letter 'J' [Reserved]
K.
Terms starting with the letter 'K' [Reserved]
L. Terms starting with the letter 'L' are
defined as follows:
(1) Length of dam: The
length measured along the dam axis at the dam crest. This also includes the
spillway, powerplant, navigation lock, fish pass, etc., where these form part
of the length of the dam. If detached from the dam these structures shall not
be included.
(2) Loss of life: The
likely number of human fatalities that would result from a dam failure flood
event. No allowances for evacuation or other emergency actions by the
population shall be considered.
M. Terms starting with the letter 'M'
[Reserved]
N. Terms starting with
the letter 'N' are defined as follows:
(1)
Naturally dry watercourse: A watercourse or portion thereof, which under normal
conditions is dry, which flows only in direct response to precipitation and
whose channel is at all times above the groundwater table.
(2) Normal operating level: The water level
elevation corresponding to the maximum storage level that excludes any flood
control or surcharge storage.
(3)
North American vertical datum 1988 (NAVD 88): The current vertical control
datum in use in North America established from nine space geodetic stations.
This basis of establishing elevation provides a precise surface, whereas the
national geodetic vertical datum 1929 (NGVD 29) is elevation established from
mean sea level.
O. Terms
starting with the letter 'O' are defined as follows:
(1) One-hundred year flood: A flood that has
1 chance in 100 of being equaled or exceeded during any year.
(2) Owner: The individual, association or
corporation, public or private, the state or the United States, owning the land
upon which a dam is constructed; having a contractual right to construct,
operate or maintain a dam; or the beneficiary of an easement to construct,
operate or maintain a dam.
P. Terms starting with the letter 'P' are
defined as follows:
(1) Probable: Likely to
occur, reasonably expected, realistic.
(2) Probable maximum precipitation:
Theoretically, the greatest depth of precipitation for a given duration that is
physically possible over a given size storm area at a particular location
during a certain time of year.
Q. Terms starting with the letter 'Q'
[Reserved]
R. Terms starting with
the letter 'R' are defined as follows: Residual freeboard: The vertical
distance between the high water line and the lowest point on the dam
crest.
S. Terms starting with the
letter 'S' are defined as follows:
(1)
Spillway: A structure over or through which excess flow is discharged from a
reservoir. If the rate of flow is controlled by mechanical means such as gates,
it is considered a controlled spillway. If the geometry of the spillway is the
only control, it is considered an uncontrolled spillway. For purposes of these
regulations, an uncontrolled outlet conduit that is used to drain the reservoir
is not considered a spillway.
(2)
Spillway crest: The lowest level at which water can flow over or through the
spillway.
(3) Spillway design
flood: The required flood that a spillway must pass without failure of the
dam.
(4) Storage: For purposes of
determining whether a dam is jurisdictional, the storage is the volume of water
impounded by the dam above the lowest elevation of the downstream toe to the
elevation of the spillway crest. For dams with no spillway, storage is measured
to the dam crest. Definitions of specific types of storage in reservoirs are:
(a) Dead storage is the storage volume of a
reservoir that lies below the invert of the lowest outlet and therefore, cannot
readily be withdrawn from the reservoir.
(b) Flood surcharge storage is the storage
volume between the maximum operating level and the maximum water level during
the spillway design flood.
(c) Live
storage is the storage volume of a reservoir that is available for use and lies
above the invert of the lowest outlet.
(d) Reservoir storage capacity is the sum of
the dead and live storage of the reservoir.
(e) Maximum storage is the sum of the
reservoir storage capacity and flood surcharge storage.
(5) Sunny day failure: Dam failure with the
reservoir at the normal operating level.
T. Terms starting with the letter 'T' are
defined as follows:
(1) Tabletop exercise: A
meeting in a conference room environment involving the dam owner and state and
local emergency personnel with responsibilities in the emergency action plan.
The format is a discussion of an emergency event, response procedures to
resolve concerns regarding coordination and responsibilities.
(2) Toe: The contact line between the outer
shell of the dam and the natural ground surface.
U. Terms starting with the letter 'U'
[Reserved]
V. Terms starting with
the letter 'V' [Reserved]
W. Terms
starting with the letter 'W' are defined as follows: Wave runup: Vertical
height above the water level to which water from a specific wave will run up
the face of a structure or embankment.
X. Terms starting with the letter 'X'
[Reserved]
Y. Terms starting with
the letter 'Y' [Reserved]
Z. Terms
starting with the letter 'Z' [Reserved]
