MILLET SWALE - AZ00059-3492
Dam Name: MILLET SWALE
State: AZ
Downstream Hazard Potential: H
Incident Type: Failure
Incident Date: 07/24/2021
Incident Driver: Malfunction of Equipment/Gate
Incident Mechanism 1: High Reservoir Level
Incident Mechanism 2Piping
Incident Mechanism 3Animal Activity
Incident IDAZ00059-3492
Incident DescriptionHeavy, localized monsoon activity resulted in rapid inflow to the reservoir. Continuous leak erosion/piping possbly along a defect in the embankment such as a crack or animal burrow. No corrective actions were taken at the dam when the leak was first detected. The gate was not completely open and is believed to have malfunctioned. A leak was observed from the lower portion of the downstream slope which eventually developed into a full breach, approximately 50-60 feet wide.
Named Hydrologic Event
EAP Enacted (Y/N) due to IncidentNo
Fatalities (Number)0
Number of People EvacuatedUnknown
Number of Habitable Structures EvacuatedUnknown
Number of Habitable Structures FloodedUnknown
Other Infrastructure ImpactsUnknown
Economic Damages (in $)Unknown
ResponseDam owner did not notify the State agency of the leak at the downstream face. State employee from the area heard about the incident and the State contacted the owner who confirmed the leak from the dam. State agency was notified in the evening of July 25, 2021 of full breach of the dam.
Volume released at failure (ac-ft)990
Additional Remarks or UpdatesSite visit on July 26, 2021 with representatives from state agency, the owner, and Navajo County Flood Control. A plan of action was developed where it was agreed the next steps would be to stabilize the breach with riprap and install ALERT gages both at the breach and upstream.
Owner TypeP
Dam TypeRE
Primary Purpose(s)CI
EAPN
Dam Height35 ft
Max Storage (ac-ft)2800.00
Surface Area (acres)125.00
Year Completed1958
NID NumberAZ00059
River NameMILLET SWALE
Latitude34.4306
Longitude-110.041
Year Modified
Regulatory Agency(ies)ADWR
Incident Time7:00 PM
Incident DurationHours
Incident Report ProducedNo
Information SourcesADWR
