Dam Safety Program

Dam Safety Program

Irvine Ranch Water District Dams Are Safe

The California Department of Water Resources Division of Safety of Dams inspects the Irvine Ranch Water District dams at Sand Canyon, Rattlesnake, and Syphon Reservoirs once every year. The dams at Santiago Creek Reservoir (Irvine Lake) and San Joaquin Reservoir are inspected twice a year. DSOD has concluded that all IRWD dams are safe for continued use.

 
California Division of Safety of Dams Inspection Program:

In California, dams are regulated by the DSOD based on several factors including the height of the dam and the storage capacity of the reservoir. Approximately 1,250 dams in California fall under state jurisdiction. DSOD has several programs that ensure dam safety. The Division inspects each dam at least once per year to ensure the dam is safe, performing as intended, and is not developing problems. DSOD also reviews the stability of dams and their major appurtenances in light of improved design approaches and requirements, as well as new findings regarding earthquake hazards and hydrologic estimates in California. Dam safety in California is governed by laws, regulations and current practices that are available on the DSOD website.

 
Irvine Ranch Water District Dam Inspection Program:

IRWD has dams at five reservoirs on the DSOD list:  Rattlesnake, San Joaquin, Sand Canyon, Santiago Creek, and Syphon Reservoirs.

In addition to state mandated inspections mentioned above, IRWD retains geotechnical consultants that specialize in dams to perform an extra semi-annual inspection of San Joaquin, Rattlesnake, Sand Canyon and Syphon Reservoirs and quarterly inspections of Santiago Creek (Irvine Lake). IRWD staff visually inspects all five dams daily and has caretakers that live onsite at the San Joaquin, Rattlesnake, Sand Canyon, and Santiago Creek (Irvine Lake) Reservoirs who also observe the dams daily. Measurements of drain flows, monitoring wells, and piezometers are taken monthly. Piezometers are used to measure ground water and other fluid pressure levels. Dam crest survey markers which give us the ability to measure horizontal or vertical movement of the dam are measured by a licensed surveyor annually. The results are evaluated to determine if there are any adverse trends.

 

Dam

DSOD Rating*

Reservoir capacity

(Acre-feet)

Restricted capacity (Acre-feet)

Restricted capacity (%)

Reason for restriction

DSOD Hazard Potential Classification**

Rattlesnake

Satisfactory

1,442

1,107

78

Seismic stability concern***

High

San Joaquin

Satisfactory

2,952

None

N/A

N/A

Extremely High

Sand Canyon

Satisfactory

788

None

N/A

N/A

Extremely High

Santiago Creek

Satisfactory

25,252

None

N/A

N/A

Extremely High

Syphon

Satisfactory

578

None

N/A

N/A

High

 *In accordance with annual data collected by the US Army Corp of Engineers for the National Inventory of Dams, the California Division of Safety of Dams (DSOD) rates the condition of all jurisdictional dams as satisfactory, fair, poor, unsatisfactory, or not rated. Dams without identified deficiencies are considered satisfactory, whereas dams with unresolved deficiencies will be considered in fair, poor, or unsatisfactory condition depending on the severity of the deficiencies

**The California Division of Safety of Dams (DSOD) hazard potential classifications are based on Federal guidelines published by the Federal Emergency Management Agency (FEMA). FEMA recommends a three-step rating system that defines low, significant and high hazard potential classifications, which are determined from potential loss of life, economic loss, and environmental damage resulting from a hypothetical dam failure. DSOD further subdivides FEMA’s High classification to an Extremely High classification in order to identify dams upstream of highly populated areas or extensive development dams with short evacuation waiting times. Whenever the population is at risk within the inundation area is 1,000 persons or more, the dam is generally assigned an Extremely High classification.

***With a restricted capacity Rattlesnake Dam condition is rated Satisfactory, the highest condition rating assigned by the California Division of Safety of Dams

 

Click here for information on Santiago Creek Dam

Questions? Please contact us at info@irwd.com.

 

IRWD Recycled Water Reservoirs with Dams

SandCanyon1 5x4.jpg

Rattlesnake1 5x4.jpg

Sand Canyon Reservoir

 Rattlesnake Reservoir

Syphon2 5x4 .jpg

IrvineLake1  5x4.jpg

 Syphon Reservoir

 Santiago Creek Reservoir (Irvine Lake)

San Joaquin1 5x4.jpg

 

San Joaquin Reservoir

 

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