Dam Safety Frequently Asked Questions

Definition of a Jurisdictional Dam

"Jurisdictional dam" is defined by statutes and rules as an artificial barrier for the impounding or diversion of water either 25 feet or more in height or having a storage capacity of more than 50 acre-feet.  Appurtenant works are included in jurisdiction.

Jurisdictional Dam graphic.

A jurisdictional dam is NOT:

  • Any barrier for the purpose of storing liquid-borne material (e.g. mine tailings dams)
  • Any barrier that is a “release-contained barrier”
  • Any barrier that is federally owned and operated
  • Sole use transportation structures

"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.

"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.

"Release-contained barrier" means any artificial barrier and appurtenant works that comply with both of the following:
a) Has storage capacity that in the event of failure would be contained within property that the release-contained barrier owner owns, controls, operates, maintains or manages.
b) The property on which the release would be contained is not open to the public.

Dam Hazard and Size Classifications

The Department bases the hazard potential classification on an evaluation of the probable present and future incremental adverse consequences that would result from the release of water or stored contents due to failure or improper operation of the dam or appurtenances, regardless of the condition of the dam. The evaluation includes land-use zoning and development projected for the affected area over the 10-year period following the classification of the dam.  We consider all of the following factors in hazard potential classification: probable loss of human life, economic and lifeline losses, and intangible losses identified and evaluated by a public resource management or protection agency.

Hazard Potential Classifications
Class Loss of Life Economic or Intangible Losses
Very Low Not Likely Limited to Owner or 100-year Floodplain
Low Not Likely


Significant Not Likely Low to High
High Likely Low to High

One of the major issues facing dam owners and the Dam Safety Section is known as "hazard creep."  This term refers to a dam originally constructed and operated as low or significant hazard that is now reclassified as high hazard due to new downstream development.  Such dams often do not meet design and maintenance requirements for high hazard dams and must be improved or removed at the owner’s expense. If the reclassified dam is considered Unsafe, the owner potentially becomes eligible for grants or loans from the Dam Repair Fund.

Dams are classified by size as small, intermediate, or large.  The size is determined by the following table.  An owner or engineer determines the size by storage capacity or height, whichever results in the larger size.

Arizona Size Classifications
Size Capacity (acre-feet) Dam Height (feet)
small 50 - 1,000 25 - 40
Intermediate 1,001 - 50,000 41 - 100
Large 50,001+ 100+
Dam Owner Responsibilities

Our rules (A.A.C. R12-15-1205) describe the general responsibilities of each dam owner.  An owner is responsible for safe design, operation, and maintenance of a dam. The owner is responsible to operate, maintain, and regularly inspect a dam so that it does not constitute a danger to human life or property.  Owners of high or significant hazard dams are required to provide timely warning to the Department and all other people listed in the emergency action plan of problems at the dam.  The owner is required to develop and maintain effective Emergency Action Plans and coordinate those plans with local officials.

Dam owners are responsible to notify the Dam Safety program and local authorities in adjacent and downstream communities of a condition that may threaten the safety of the dam.
We also require dam owners to install, maintain, and monitor instrumentation to evaluate the performance of the dam.  Conditions that may require monitoring include land subsidence, earth fissures, embankment cracking, phreatic surface, seepage, and embankment movements.
The dam owner is responsible to perform timely maintenance and ordinary repair of the dam.
If a change of ownership of a dam occurs, the new owner is required to notify the Department within 15 days after the date of the transaction and provide the mailing address and telephone number where the new owner can be contacted.  Within 90 days after the date of the transaction, the new owner is required to provide the name and telephone number of the individual or individuals who are responsible for operating and maintaining the dam.

Emergency Action Planning and Response

Each owner of a high and significant hazard potential dam is required to prepare, maintain, and exercise a written emergency action plan (EAP) for immediate defensive action to prevent failure of the dam and to minimize any threat to downstream development.

The EAP defines the dam owner’s requirements to observe his dam for emergency conditions, the responsibilities for notifying a pre-determined list of emergency responders, and a description of the downstream areas potentially affected.

The EAP is required to contain the following items:
• Notification Chart
• Reservoir & Dam Description
• Delineation of Unsafe Conditions, Procedures, & Triggering Events
• Delineation of Responsibilities
• Discussion of Emergency Supplies/Equipment
• Flood Inundation Map

The Department is serious in its commitment to ensure that all significant and high hazard dams in the state of Arizona have effective EAPs for protection of the public against loss of life and property.  Lack of an adequate EAP is considered to be a Safety Deficiency.

To minimize the time and expense required by dam owners, the Department has developed a fill-in-the-blank EAP Form. The Dam Safety team can assist a dam owner with completing this form.  However, the services of an independent professional engineer may be required to satisfactorily develop an inundation map for final EAP completion.

The dam owner is required to review and update the emergency action plan annually or more frequently to incorporate changes such as new personnel, changing roles of emergency agencies, emergency response resources, conditions of the dam, and information learned from mock exercises.

Inspection and Oversight of Existing Dams

The Dam Safety program is responsible for the safety of nearly 240 non-federal dams in Arizona. The Department's team performs safety inspections of high hazard dams every year, every three years for significant hazard dams, and every five years for low and very low hazard dams.  The dam owner is charged an inspection fee as prescribed in A.A.C. R12-15-105. 

During inspections, “safety deficiencies” may be identified at operating dams and will require owners to implement corrective actions.  A “safety deficiency” refers to a condition at a dam that impairs or adversely affects the safe operation of the dam.  Such conditions may include embankment cracks, erosion, breaching, unusual/uncontrolled seepage, slope instability and/or inadequate spillway capacity.

The Dam Safety program reviews all engineering assessments and monitoring reports submitted for the dams. Approximately, 120 dams per year are due for inspection by the Dam Safety team. Following each inspection, a written report is returned to the owner identifying Safety Deficiencies and making recommendations for needed maintenance work.  The Dam Safety program tracks identified Safety
Deficiencies and works to assist dam owners in their resolution.

Some examples of Safety Deficiencies include:

Transverse Embankment Cracking


Erosion bank


Slope Instability/Outlet Damage


Unsafe Dam Rehabilitation

The Dam Safety program evaluates the safety of operating dams and maintains a priority list of “Unsafe” Dams.  “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. 

Unsafe Classifications
Category 1: Unsafe Dams with Elevated Risk of Failure
Category 2: Unsafe Dams Requiring Rehabilitation or Removal
Category 3: Unsafe Dams with Uncertain Stability during Extreme Events (Requiring Study)
Category 4: Unsafe Dams Pending Evaluation of Flood-Passing Capacity (Requiring Study)


In 1988, the Arizona Legislature established a Dam Repair Fund designed to provide the Department the money necessary to initiate emergency actions associated with an imminent dam failure.  Money expended by the Department on an emergency action is to be reimbursed by lien money recovered from the owner of the dam.  The Director of the Department may also loan and/or grant money from the Fund to owners for repairs or removal to dams classified as being in an unsafe, non-emergency condition due to severe safety deficiencies. The Fund could also be used for engineering and scientific studies related to unsafe dams. Fees for applications and dam inspections are deposited into the Fund.  In 1988, the Legislature provided $2.5 million to the Fund for the repair of two unsafe dams.  In 2005, the Arizona Game and Fish Commission transferred $950,000 to the Fund towards emergency repairs of a dam.

Dam Repair Case Studies

Reconstructing River Reservoir No. 3 - From Emergency Action to Breach to Safe Operation in 21 Months 


Construction Monitoring

The Dam Safety program performs monitoring of construction to verify that approved drawings, specifications, and quality assurance procedures are adhered to.  Conditions of Approval of the Applications usually require Department inspection and formal approvals of dam foundations and other critical construction features.  We also require construction to start within one year of our approval, and notify us at least 48 hours in advance to schedule an inspection.

Construction Monitoring
Construction Monitoring at a lake
Construction Monitoring spillway
Unregistered (Violation) Dam

Per A.R.S. § 45- 1216, it is unlawful for an owner, director, officer, agent, employee, contractor or his agents to construct, reconstruct, repair, enlarge, alter or remove a dam without an approval from the Department.  It is also unlawful for the agents or employees of the director to permit such work to be done without immediately notifying the director.  A person who violates this statute is guilty of a Class 2 misdemeanor, and each day such violation continues constitutes a separate offense.

If the Director of the Department of Water Resources has reason to believe that a person is in violation, the Director may give the person written notice that the person may appear and show cause at an administrative hearing not less than 30 days from the date of service of the notice why the person should not be ordered to cease and desist from the violation.  The notice shall inform the person of the date, time and place of the hearing and the consequences of the failure to appear.

Occasionally, the existence of a previously unregistered dam is brought to the attention of the Dam Safety program.  In these cases, the Dam Safety team performs a site visit to establish jurisdictional status and hazard classification.  Owners of low hazard unregistered dams are usually issued permission to operate the dam.  Owners of high and significant hazard unregistered dams are required to demonstrate the safety of the dam prior to receiving permission to operate.  The Dam Safety program has assisted several owners in removal of small, unwanted high and significant hazard dams using grants and loans from the Dam Repair Fund.