SECTION 299.2. Definitions

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.

(40) Normal storage capacity--The volume, in acre-feet, of the impoundment created by the dam at the lowest uncontrolled spillway crest elevation, or at the maximum elevation of the reservoir at the normal (non-flooding) operating level.

(41) NAD83 conus datum--The North American Datum of 1983 is a reference system used to obtain the spherical coordinates of a point on the earth's surface. The standard North American Datum of 1983, or any future updates, must be used for all latitude and longitude measurements.

(42) NAVD88 datum--The North American Vertical Datum of 1988 is a reference system used to obtain vertical measurements on the earth's surface. The North American Vertical Datum of 1988 must be used for all vertical measurements recorded with a global positioning system receiver.

(43) Outlet--A conduit or pipe controlled by a gate or valve, or a siphon, that is used to release impounded water from the reservoir.

(44) Owner--Any person who can be one or more of the following:

(A) holds legal possession or ownership of an interest in a dam;

(B) is the fee simple owner of the surface estate of the tract of land on which the dam is located if actual ownership of the dam is uncertain, unknown, or in dispute unless the person can demonstrate by appropriate documentation, including a deed reservation, invoice, bill of sale, or by other legally acceptable means that the dam is owned by another person or persons;

(C) is a sponsoring local organization that has an agreement with the Natural Resources Conservation Service for a dam constructed under the authorization of the Flood Control Act of 1944 (as amended), Public Law 78-534, the Watershed Protection and Flood Prevention Act, 1954 (as amended), Public Law 83-566, the pilot watershed program under the Flood Prevention of the Department of Agriculture Appropriation Act of 1954, Public Law 156-67, or Subtitle H of Title XV of the Agriculture and Flood Act of 1981, the Resource Conservation and Development Program; or

(D) has a lease, easement, or right-of-way to construct, operate, or maintain a dam.

(45) Piping--The progressive removal of soil particles from a dam by percolating water, leading to development of channels or flow paths.

(46) Principal spillway--Also commonly referred to as the service spillway, the primary or initial spillway engaged during a rainfall runoff event that is designed to pass normal flows.

(47) Probable maximum flood (PMF)--The flood magnitude that may be expected from the most critical combination of meteorologic and hydrologic conditions that are reasonably possible for a given watershed.

(48) Probable maximum precipitation (PMP)--The theoretically greatest depth of precipitation for a given duration that is physically possible over a given size storm area at a particular geographical location at a certain time of the year.

(49) Professional engineer--An individual licensed by the Texas Board of Professional Engineers to engage in the practice of engineering in the state of Texas, with experience in the investigation, design, construction, repair, and maintenance of dams.

(50) Proposed dam--Any dam not yet under construction.

(51) Pumped storage dam--A rectangular or circular embankment used to store water pumped from another source.

(52) Reconstruction--Removal and replacement of an existing dam or appurtenant structures.

(53) Rehabilitation--The completion of all work necessary to extend the service life of a dam and meet the safety and performance standards of this chapter.

(54) Removal--The complete elimination of a dam, the appurtenant structures, and the reservoir to its natural channel by removing enough of the dam to the extent that no water can be either permanently impounded, nor temporarily detained, by the dam (no significant differential between the upstream and downstream water surface elevations) during normal conditions, as well as during the design flood of the dam.

(55) Repairs--Any work done on a dam that may affect the integrity, safety, and operation of the dam, including, but not limited to:

(A) excavation into the embankment fill or foundation of a dam; or

(B) removal or replacement of major structural components of a dam or appurtenant structures.

(56) Reservoir--A body of water impounded by a dam.

(57) Safe manner--Operating and maintaining a dam in sound condition, free from defect or damage that could hinder the dam's functions as designed.

(58) Seal--To affix a professional engineer's seal to each sheet of construction plans or to an engineering report or required document.

(59) Secondary highways--Roads classified as a major or minor collector road by the Texas Department of Transportation, including Farm-to-Market roads used to provide service to schools.

(60) Secure location--A building that is locked and accessible to the owner and owner's representative.

(61) Spillway--An appurtenant structure that conducts outflow from a reservoir.

(62) Sponsoring local organization--any political subdivision of the state, or other entity, with the authority to carry out, maintain, or operate work of improvement installed with the assistance of the federal government.

(63) Stability analysis--The analytical procedure for determining the most critical factor of safety for a slope.

(64) Substantially complete--A dam under construction that is complete except for minor correction of items identified in the final construction inspection and that can be operated in a safe manner to the dam's full functional capability.

Source Note: The provisions of this §299.2 adopted to be effective January 1, 2009, 33 TexReg 10465; amended to be effective September 29, 2022, 47 TexReg 6211