Dam Safety and the Importance of the Division of Safety of Dams with Andy Mangney

The California Department of Water Resources, Division of Safety of Dams (DSOD) oversees the California Dam Safety Program that regulates approximately 1,250 dams in California. At the forefront of DSOD’s oversight is public safety. DSOD inspects dams on an annual basis to ensure they are safe and are performing as intended. DSOD also conducts independent reviews of applications for dam construction, removal, alteration or repair, has inspection oversight over dam construction projects, and periodically reviews the stability of dams and their critical related structures in light of improved design approaches and requirements. DSOD works closely with dam owners to identify and correct issues on an ongoing basis.

In recognition of National Dam Safety Awareness Day, Andy Mangney who serves as the Field Engineering Branch Chief overseeing DSOD’s dam inspection and monitoring program, took some time to answer questions about what DSOD is doing to protect Californians.

What is your background and experience?

I received a Bachelor of Science degree in Civil Engineering from Cal Poly, San Luis Obispo in 1993 and a Master of Science Degree in Civil Engineering from Sacramento State University in 2002.

I started working for DWR in late-1993 as a Junior Civil Engineer on the construction of the Coastal Branch of the California Aqueduct. This was a dream job for me out of college; I loved working outside and inspecting construction and troubleshooting issues on civil structures as they were being built. This job was pivotal in my chosen career path to work more in civil engineering jobs geared toward field work rather than the office. I started working for DSOD in 1997 where I have progressed through various positions in the Field Engineering Branch, making my way up to the Field Engineering Branch Chief. 

How are dams built and how do they work?

Dams are constructed of soil/rock or concrete and every structure is unique. Some major factors that are considered in the determination of the type of dam are cost, location, availability of materials to build the dam, and site geology. A dam serves as an impermeable water barrier, and it must be robust enough to withstand the pressure of water against it and extreme pressures that can occur from earthquakes and floods.

Besides the dam structure, critical structures are also required, such as outlets that move water out of the reservoir and spillways that bypass flood flows to prevent dam overtopping.

Who owns the dams in California?

Dams are owned by the State of California, water agencies and districts, counties, cities, homeowner’s associations, private companies, or private citizens. Roughly half of the dams under DSOD’s jurisdiction are privately owned. Dams are also owned by the federal government, but these dams are not under DSOD jurisdiction.

 

What are common causes leading to dam failures and incidents?

In California, we are fortunate that dam failures and incidents are extremely rare, in part due the robustness of California’s Dam Safety Program, which is the largest state dam safety program in the United States. Failures or incidents can be caused by deterioration due to age, poor construction techniques and materials, unfavorable geologic conditions, and lack of maintenance.  Dam overtopping, or water flowing uncontrolled over the top of the dam, can also occur due to factors including poor reservoir operations, extreme weather, or an inadequate or no spillway.  Earthquakes pose the largest risk to dams in California because the State is situated in a high seismic area that has more frequent and larger earthquakes compared to the rest of the country.

What are the issues facing dam safety in California?

Aging infrastructure and lack of money to fund necessary studies and retrofits of dams. About 75 percent of the approximate 1,250 regulated dams are more than 50 years old and some dams have outlived their design life or do not meet current dam safety standards. Today in California, few new dams are being constructed, and much of the emphasis is spent on retrofitting and rebuilding existing dams so they meet current dam safety standards.   

How does DSOD conduct dam inspections?

Every dam is unique and has different features that we inspect. DSOD has rigorous inspection processes for each dam. DSOD typically walks the entire facility, including the top of the dam, the downstream slopes, the area below the dam, and any critical related structures looking for changes in the dam’s condition or performance -- such as signs of new instability or leakage. We also inspect the outlet works to ensure that the reservoir can be drained in a dam emergency and the spillway remains clear and unimpeded to pass flood flows. Upon returning to the office, the DSOD engineer writes a comprehensive inspection report documenting their findings, recommendations, and conclusions on the safety of the dam, which is provided to the dam owner. 

What happens when DSOD finds an issue? What kind of action is required by a dam owner?

If the DSOD engineer identifies a dam safety concern, corrective action is required of the dam owner at the owner’s expense. Minor maintenance issues such as vegetation removal generally need to be completed in about six months, but a significant issue such as a stability issue or a problem with the outlet works may require immediate attention.

DSOD may require interim risk reduction measures such as lowering the reservoir level or temporary repairs, if necessary. For the more complex issues beyond routine maintenance, the dam owner is required to employ an engineer to work with DSOD to address the issue. In rare cases where a safety issue is not addressed in a timely manner, reservoir restrictions are imposed and/or enforcement is pursued.

What are the most recent advancements in dam safety?

The greatest advancements are probably in the understanding of how dams perform under normal and extreme loading conditions such as earthquakes and floods.

Some of these advancements are from modern computer tools that allow for much more sophisticated engineering evaluations. Others are due to advancements and research in the field of engineering, and from real world case histories from dam incidents and failures. This research helps us better understand the engineering properties of materials used to build the dam and its critical structures, but also helps us understand the materials below these structures.