The following words and terms in this section are in addition
to the definitions in §3.2 of this title (relating to Definitions).
The words and terms in this section, when used in this chapter, have
the following meanings.
(1) Abandon--The owner no longer maintaining a dam
for a period of ten years, or refusing to maintain the dam.
(2) Accepted engineering practices--The application
of design and analysis methods that are commonly used by professional
engineers in their field of expertise and are well documented in published
design manuals, codes of practice, text books, and engineering journals.
(3) Alteration--Any change to a dam or appurtenant
structures that affects the integrity, safety, and operation of the
dam, including, but not limited to:
(A) changing the height of a dam;
(B) increasing the normal pool or principal spillway
elevation, or changing the hydraulic capability of the principal spillway;
or
(C) changing the original elevation, physical dimensions,
or hydraulic capability of an emergency spillway.
(4) Appurtenant structures--The outlet works and controls,
spillways and controls, gates, valves, siphons, access structures,
bridges, berms, drains, hydroelectric facilities, instrumentation,
and other structures related to the operation of a dam.
(5) Breach--An excavation or opening, either controlled
or a result of a failure of the dam, through a dam or spillway that
is capable of completely draining the reservoir down to the approximate
original topography so the dam will no longer impound water, or partially
draining the reservoir to lower impounding capacity.
(6) Breach analysis--The analysis of potential dam
failure scenarios, including overtopping and piping (magnitude, duration,
and location), using accepted engineering practices, to evaluate downstream
hazard potential or to develop inundation maps.
(7) Breach inundation area--An area that would be flooded
as a result of a dam failure.
(8) Closure of dam--The commencement of placing material
within the closure section of the dam.
(9) Closure section--The section of the dam left open
during construction of a proposed dam in order to pass floodwaters
through the dam without endangering the dam.
(10) Commence construction--An actual, visible activity
beyond planning or land acquisition that initiates the beginning of
the construction of a dam in the manner specified in the approved
construction plans and specifications for that dam. The action must
be performed in good faith with the intent to continue with the construction
through completion.
(11) Conceptual design--A design that presents a location
and proposed plan of the dam and appurtenant structures and elevations
of all pertinent features of the dam.
(12) Construction--Building a proposed dam and appurtenant
structures capable of storing water.
(13) Construction change order--A document recommended
by the owner's professional engineer and signed by the owner's contractor
and the owner that authorizes a significant addition, deletion, or
revision of the approved construction plans and specifications that
has a material impact on the safety and integrity of the dam.
(14) Dam--Any barrier or barriers, with any appurtenant
structures, constructed for the purpose of either permanently or temporarily
impounding water.
(15) Dam failure--breach and uncontrolled release of
the reservoir.
(16) Deficient dam--A dam that fails to meet the requirements
of this chapter and poses a significant threat to human life or property.
(17) Deliberate impoundment--The intentional impoundment
of water in the reservoir, including:
(A) closing the lowest planned outlet or spillway;
(B) blocking the diversion works that are used during
construction to divert water around the construction area; and
(C) beginning the closure of the dam.
(18) Design flood--The flood used in the design and
evaluation of a dam and appurtenant structures, particularly for determining
the size of spillways, outlet works, and the effective crest of the
dam.
(19) Detention dam--A dam that has an impoundment that
is normally dry and has an ungated outlet structure that is designed
to completely drain the water impounded during a flood within five
days.
(20) Drawdown--The change in surface elevation of a
reservoir due to a withdrawal of water from the reservoir.
(21) Effective crest of the dam--The elevation of the
lowest point on the crest (top) of the dam, excluding spillways.
(22) Emergency action plan--A written document prepared
by the owner or the owner's professional engineer describing a detailed
plan to prevent or lessen the effects of a failure of the dam or appurtenant
structures.
(23) Emergency repairs--Any repairs, considered to
be temporary in nature, necessary to preserve the integrity of the
dam and prevent a possible failure of the dam.
(24) Emergency spillway--An auxiliary spillway designed
to pass a large, but infrequent, volume of flood flow, with a crest
elevation higher than the principal spillway or normal operating level.
(25) Engineering inspection--Inspection performed by
a professional engineer, or under the supervision of a professional
engineer, to evaluate the condition, safety, and integrity of the
dam and appurtenant structures to determine if the dam and appurtenant
structures meet applicable rules and accepted engineering practices,
including a field inspection and review of records for design, construction,
and performance.
(26) Enlargement--Any change in, or addition to, an
existing dam or reservoir that raises, or may raise, the normal storage
capacity of the reservoir impounded by the dam.
(27) Existing dam--Any dam under construction or completed
as of the effective date of these rules.
(28) Fetch--The straight-line distance across a reservoir
subject to wind forces.
(29) Hazard classification--A measure of the potential
for loss of life, property damage, or economic impact in the area
downstream of the dam in the event of a failure or malfunction of
the dam or appurtenant structures. The hazard classification does
not represent the physical condition of the dam.
(30) Height of dam--The difference in elevation between
the natural bed of the watercourse or the lowest point on the downstream
toe of the dam, whichever is lower, and the effective crest of the
dam.
(31) Inundation map--A map delineating the area that
would be flooded by a particular flood event, or a dam failure.
(32) Loss of life--Human fatalities that would result
from a failure of the dam, without considering the mitigation of loss
of life that could occur with evacuation or other emergency actions.
(33) Main highways--Roads classified as an arterial
system by the Texas Department of Transportation, including interstate
highways, United States highways, and state highways, listed as either
interstate or principal or minor arterial.
(34) Maintenance--Those tasks that are generally recurring
and are necessary to keep the dam and appurtenant structures in a
sound condition, free from defect or damage that could hinder the
dam's functions as designed, including adjacent areas that also could
affect the function and operation of the dam.
(35) Maintenance inspection--Visual inspection of the
dam and appurtenant structures by the owner or owner's representative
to detect apparent signs of deterioration, other deficiencies, or
any other areas of concern.
(36) Maximum storage capacity--The volume, in acre-feet,
of the impoundment created by the dam at the effective crest of the
dam. For purposes of calculating maximum storage capacity for the
Inventory of Dams as described in §299.7 of this title (relating
to Inventory of Dams), only water that can be stored above natural
ground level (not in excavations in the reservoir) or that could be
released by a failure of the dam is considered in assessing the storage
volume. The maximum storage capacity may decrease over time due to
sedimentation or increase if the reservoir is dredged.
(37) Minimum freeboard--The difference in elevation
between the effective crest of the dam and the maximum water surface
elevation resulting from routing the design flood appropriate for
the dam.
(38) Minor highways--Roads not classified as a main
or secondary highway as defined in this subsection, including county
roads and Farm-to-Market roads not used to provide service to schools.
(39) Modification--Any structural alteration of a dam,
the spillways, the outlet works, or other appurtenant structures that
could influence or affect the integrity, safety, and operation of
the dam.
Cont'd... |
