The California Water Commission hears an update on dam safety
With so many dams in California and the current dismal budget climate, perhaps you might have been concerned about the status of the state’s dam safety program? Or maybe you hadn’t thought of it, but with over 1250 dams in California, it’s no doubt an important issue.
Today’s Maven’s Minutes covers the presentation that David Gutierrez, DWR’s Chief of the Division of the Safety of Dams, gave to the California Water Commission on the status and update of the state’s dam safety program at the September 19th Commission meeting. He talked about the strength of California’s program, the functions and roles of the Division, and some of the current projects underway, including one unique project to actually move a river.
- First, they drive a lot of our technical knowledge about dams and as we learn more, we apply that knowledge to other dams.
- Secondly, dam failures drive political action and legislation. After several dam failures in the early 1900s, legislation was enacted to address dam safety, but it was weak and ineffective. After the 1929 St. Francis Dam disaster, the legislature created a state agency to oversee the safety of dams.
The state of California’s Dam Safety Program:
- Originally funded by the state’s general fund, it wasn’t until 1993 that fees began to be collected from the owners, but still, the majority of funding for the program came from the general fund. After the 2003 budget crunch, fees were increased substantially and today, the program is entirely funded by revenues collected from dam owners and from application fees.
- As a result, Mr. Gutierrez reported that California’s dam safety program is well funded and coordinated, and for good reason: “When you look at California compared to the rest of the nation, we have the biggest dams in the country and some of the biggest in the world, as well as high populations, so the risk here in California is off the scale compared to many other states. Therefore, the dam safety program in California is, by far, the strongest in the nation and one of the strongest in the world, and we work hard to keep it that way.”
The Division of the Safety of Dams has four main activities:
- Evaluating old dams: The most difficult issue facing the Division is dealing with aging dams. The majority of dams in California are between 50 to 100 years old. Besides dealing with problems due to their age, many of these dams were built to a different engineering standard, if any standard at all. Using a variety of technological tools, engineers try to determine how these dams built in the early 1900s were constructed, what materials were used, and what they were built on top of. Engineers then try and simulate what would happen in the case of a major earthquake or flood.
- Reviewing new dam construction: Every year, about a dozen new dams are built, most of them small. Also, there have been a number of projects across the state to increase the height of some existing dams. Prior to construction, the Division conducts an independent review of the design, the plans, and the specifications of the dam to ensure the dam is going to be safe.
- Dam construction supervision: Once a dam is approved for construction, the division continues to be involved by inspecting and following the construction process.
- Dam inspections: All of the 1250 dams under the jurisdiction of the Division are inspected at least once per year and monitored for changes. Visual inspections as well as instruments tell us how the dam is behaving.
Earthquakes and dams: Dam safety remains an evolving science. In 1971, the Lower San Fernando Dam in Southern California held water that was 40 to 50 feet below the crest of the dam. After the San Fernando earthquake, the dam slumped into the reservoir, leaving only 3 or 4 feet to the crest of the dam. With 80,000 people downstream, it would have been by far the worst disaster in the U.S. But since then, our knowledge about earthquakes has increased significantly: we know about liquefaction, we know where the faults are, we know how they rupture, and we know how they will affect dams. Since that earthquake, California began a program to evaluate all dams in California. A new paradigm is constantly evolving in terms of our understanding of how earthquakes affect dams, so we must continually go back and check dams.
Emergency response: After an earthquake, within a minute, Mr. Gutierrez is notified on his cellphone as to which dams were affected and how, and inspectors are sent out quickly to evaluate the dams and evacuate people if necessary.
Current projects underway:
- Calaveras Dam in the East Bay: Mr.Gutierrez detailed the construction history of this dam which was eventually determined to be unsafe in the event of an earthquake. With 150,000 people downstream of the dam, the owner was required to rebuild this structure. Construction is currently underway on a new dam just downstream of the existing Calaveras Dam. (For a fact sheet on this project, click here.)
- Big Tujunga Dam: A large concrete dam built in 1930, this dam was evaluated and deemed to cause problems in the event of an earthquake, so a concrete buttress was placed on the face of dam, and it is now considered safe. (To read a news article about this project, click here.)
- San Vicente Dam: San Diego County Water Authority is raising the height of the dam 100 feet for emergency storage in the event of an earthquake. A new method of construction called roller compacted concrete is being used. It is a much more efficient and faster way than older methods. (For more on this project from the San Diego County Water Authority, click here. To read more about the roller compacted concrete technique from Parsons, the firm building the project, click here.)
- San Clemente Dam: A very unique situation which has taken 20 to 30 years to resolve. This small arch concrete dam was built in 1922 has become filled with sediment and also has earthquake safety concerns. The Division ordered the owner to find a way to deal with this structure. The easiest, fastest, and cheapest way to resolve this situation would have been to buttress the dam, but other agencies were concerned because there aren’t capabilities for fish passage. So as a result, a different alternative had to be found. The solution is to move the river – by a fortunate twist of topography, the river can be moved over one canyon, the dam removed and sediment stabilized. The fish will have a new passageway and the dam safety issue will be eliminated. A very unique situation that we can do this. (For more on the San Clemente Dam Project, click here.)
National Dam Safety:
- There are over 90,000 dams across the country. While the Army Corps and Reclamation are responsible for the large dams, most of these dams are small and are regulated by the states.
- In 1889, the worst dam failure in the U.S. cost 2200 lives and occurred in Johnstown, Pennsylvania.
- In the 1970s, several dam failures causing loss of life spurred federal legislation on dam safety. In response, President Carter developed the National Dam Safety Act and the National Dam Safety Program, and sent federal inspectors to inspect dams. In 1985, the Association of State Dam Safety Officials was established, and together these two programs make the nations’ dam safety program cohesive.
- At the time the national program was established, only half the states had a dam safety program. Today, 49 out of 50 have dam safety programs. These programs vary from state to state and for various reasons. Population in some of the states is very low, so the hazards and risks are different. Some programs have only $100,000 in funding and one inspector; by comparison, California’s program is $11 million and employs 60 inspectors.
National dam safety challenges:
- Technical knowledge: It is always evolving but it is never enough. Our learning continues on understanding how dams behave.
- Resources: Water is important and more valuable in the west, so there are more resources for dam rehabilitation available. However, funding to fix unsafe dams across the nation is a issue. There are many dams that have been identified as having a problem but there are no funds to fix them. Additionally, some state’s dam safety programs are significantly underfunded. Federal legislation to provide funds hasn’t gone anywhere in today’s difficult budget climate.
Mr. Gutierrez was questioned further on the San Clemente Dam removal project and the moving of the Carmel River: Mr. Gutierrez explained that the topography of this area makes this situation very unique. The river comes down to the dam, there’s a small knoll that we can take advantage of to move the river over for a few thousand feet and then return it to the channel. It’s not a simple process; the river wasn’t there before, so how is it going to behave in that new channel? Consultants have been working on those questions, and I think we have a good handle on them. We haven’t started construction yet. “I think it’s a unique project, a one of a kind. I can’t think of any time where we’ve actually removed a dam of this height with the complexities that we’re dealing with from an environmental standpoint as well as an engineering standpoint.” (For more on the San Clemente Dam Project, click here.)
How common is sedimentation in California dams? Sedimentation is more of an issue in the western part of California, Mr. Gutierrez said. The rock there is beat up by the tectonics of the area; the rocks are sheered and much more erodible than in the Sierra. The two dams with the biggest problems are San Clemente Dam and Matilija Dam in Southern California. Sedimentation is a difficult and expensive issue to deal with, but it’s not a major issue: “It’s hard to put a percentage on the number of dams with this problem, but it’s a low number, a couple of percent that have a significant problem like this.”
Question about the size of the dam and when it falls under the Division’s jurisdiction: It depends upon the height of the dam and the volume of the reservoir behind it. If the dam is higher than 25 feet and if there is more than 50 acre-feet is in the reservoir, it will be under the Division’s jurisdiction. There are a few other rules: if the reservoir is less than 15 acre-feet, it doesn’t matter how high it is, and if the dam is less than 6 feet tall, it doesn’t matter how much water is behind it.
FOR MORE INFORMATION:
- Click here to view the power point for this presentation.
- Click here for the webcast. The presentation on dam safety is agenda item #6.
- Click here to visit DWR’s Division of Dam Safety webpage.