Arizona Administrative Code
Title 12 - NATURAL RESOURCES
Chapter 15 - DEPARTMENT OF WATER RESOURCES
Article 12 - DAM SAFETY PROCEDURES
Section R12-15-1202 - Definitions
In addition to the definitions provided in A.R.S. § 45-1201, the following definitions are applicable to this Article:
1. "Alteration or repair of an existing dam or appurtenant structure" means to make different from the originally approved construction drawings and specifications or current condition without changing the height or storage capacity of the dam or reservoir, except for ordinary repairs and general maintenance as prescribed in R12-15-1217.
2. "Appurtenant structure" means any structure that is contiguous and essential to the safe operation of the dam including embankments, saddle dikes, outlet works and controls, diversion ditches, spillway and controls, access structures, bridges, and related housing at a dam.
3. "Classification of dams" means the placement of dams into categories based upon an evaluation of the size and hazard potential, regardless of the condition of the dam.
4. "Concrete dam" means any dam constructed of concrete, including arch, gravity, arch-gravity, slab and buttress, and multiple arch dams. A dam that only has a concrete facing is not a concrete dam.
5. "Construction" means any activity performed by the owner or someone employed by the owner that is related to the construction, reconstruction, repair, enlargement, removal, or alteration of any dam, unless the context indicates otherwise. Construction is performed after approval of an application and before issuance of a license.
6. "Dam failure inundation map" means a map depicting the maximum area downstream from a dam that would be flooded in the event of the worst condition failure of the dam.
7. "Department" means the Arizona Department of Water Resources.
8. "Director" means the Director of the Arizona Department of Water Resources or the Director's designee.
9. "Embankment dam" means a dam that is constructed of earth or rock material.
10. "Emergency spillway" means a spillway designed to safely pass the inflow design flood routed through the reservoir. If the flow is controlled by gates, it is a controlled spillway. If the flow is not controlled by gates, it is an uncontrolled spillway.
11. "Engineer" means a Professional Engineer registered and licensed in accordance with A.R.S. Title 32, Chapter 1, with proficiency in engineering and knowledge of dam technology.
12. "Enlargement to an existing dam or appurtenant structure" means any alteration, modification, or repair that increases the vertical height of a dam or the storage capacity of the reservoir.
13. "Flashboards" mean timber, concrete, or steel sections placed on the crest of a spillway to raise the retention water level that may be quickly removed at time of flood either by a tripping device or by designed failure of the flashboards or their supports.
14. "Flood control dam" means a dam that uses all of its reservoir storage capacity for temporary impoundment of flood waters and collection of sediment or debris.
15. "Hazard potential" means the probable incremental adverse consequences that result from the release of water or stored contents due to failure or improper operation of a dam or appurtenances.
16. "Hazard potential classification" means a system that categorizes dams according to the degree of probable incremental adverse consequences of failure or improper operation of a dam or appurtenances. The hazard potential classification does not reflect the current condition of the dam with regard to safety, structural integrity, or flood routing capacity.
17. "Height" means the vertical distance from the lowest elevation of the outside limit of the barrier at its intersection with the natural ground surface to the spillway crest elevation. For the purpose of determining jurisdictional status, the lowest elevation of the outside limit of the barrier may be the outlet pipe invert elevation if the outlet is constructed below natural ground.
18. "Impound" means to cause water or a liquid to be confined within a reservoir and held with no discharge.
19. "Incremental adverse consequences" means under the same loading conditions, the additional adverse consequences such as economic, intangible, lifeline, or human losses, that would occur due to the failure or improper operation of the dam over those that would have occurred without failure or improper operation of the dam.
20. "Inflow design flood" or "IDF" means the reservoir flood inflow magnitude selected on the basis of size and hazard potential classification for emergency spillway design requirements of a dam.
21. "Intangible losses" means incremental adverse consequences to property that are not economic in nature, including property related to social, cultural, unique, or resource-based values, including the loss of irreplaceable and unique historic and cultural features; long-lasting pollution of land or water; or long-lasting or permanent changes to the ecology, including fish and endangered species habitat identified and evaluated by a public natural resource management or protection agency.
22. "Jurisdictional dam" means a barrier that meets the definition of a dam prescribed in A.R.S. § 45-1201 that is not exempted by R12-15-1203 over which the Department of Water Resources exercises jurisdiction.
23. "Levee" means an embankment of earth, concrete, or other material used to prevent a watercourse from spreading laterally or overflowing its banks. A levee is not used to impound water.
24. "License" means license of final approval issued by the Director upon completion or enlargement of a dam under A.R.S. § 45-1209.
25. "Lifeline losses" mean disruption of essential services such as water, power, gas, telephone, or emergency medical services.
26. "Liquid-borne material" means mine tailings or other milled ore products transported in a slurry to a storage impoundment.
27. "Maximum credible earthquake" means the most severe earthquake that is believed to be possible at a point on the basis of geologic and seismological evidence.
28. "Maximum water surface" means the maximum elevation of the reservoir water level attained during routing of the inflow design flood.
29. "Natural ground surface" means the undisturbed ground surface before excavation or filling, or the undisturbed bed of the stream or river.
30. "Outlet works" means a closed conduit under or through a dam or through an abutment for the controlled discharge of the contents normally impounded by a dam and reservoir. The outlet works include the inlet and outlet structures appurtenant to the conduit. Outlet works may be controlled or uncontrolled.
31. "Probable" means likely to occur, reasonably expected, and realistic.
32. "Probable maximum flood" or "PMF" means the flood runoff expected from the most severe combination of critical meteorologic and hydrologic conditions that are reasonably possible in the region, including rain and snow where applicable. 1/2 PMF is that flood represented by the flood hydrograph with ordinates equal to 1/2 the corresponding ordinates of the PMF hydrograph.
33. "Probable maximum precipitation" means the greatest depth of precipitation for a given duration that is theoretically physically possible over a particular size storm area at a particular geographical location at a particular time of year.
34. "Reservoir" means any basin that contains or is capable of containing water or other liquids impounded by a dam.
35. "Residual freeboard" means the vertical distance between the highest water surface elevation during the inflow design flood and the lowest point at the top of the dam.
36. "Restricted storage" means a condition placed on a license by the Director to reduce the storage level of a reservoir because of a safety deficiency.
37. "Saddle dike or saddle dam" means any dam constructed in a topographically low area on the perimeter of a reservoir, required to contain the reservoir at the highest water surface elevation.
38. "Safe" means that a dam has sufficient structural integrity and flood routing capacity to make failure of the dam unlikely.
39. "Safe storage level" means the maximum reservoir water surface elevation at which the Director determines it is safe to impound water or other liquids in the reservoir.
40. "Safety deficiency" means a condition at a dam that impairs or adversely affects the safe operation of the dam.
41. "Safety inspection" means an investigation by an engineer or a person under the direction of an engineer to assess the safety of a dam and determine the safe storage level for a reservoir, which includes review of design reports, construction documents, and previous safety inspection reports of the dam, spillways, outlet facilities, seepage control and measurement systems, and permanent monument or monitoring installations.
42. "Spillway crest" means the highest elevation of the floor of the spillway along a centerline profile through the spillway.
43. "Storage capacity" means the maximum volume of water, sediment, or debris that can be impounded in the reservoir with no discharge of water, including the situation where an uncontrolled outlet becomes plugged. The storage capacity is reached when the water level is at the crest of the emergency spillway, or at the top of permanently mounted emergency spillway gates in the closed position. Storage capacity excludes dead storage below the natural ground surface.
44. "Surcharge storage" means the additional water storage volume between the emergency spillway crest or closed gates, and the top of the dam.
45. "Total freeboard" means the vertical distance between the emergency spillway crest and the top of the dam.
46. "Unsafe" means that safety deficiencies in a dam or spillway could result in failure of the dam with subsequent loss of human life or significant property damage.
