Park's Prologue

Welcome!

This homepage is made to presents a well-reaearched information regarding dam safety in California. The web site is to be informative for citizens, policy-makers and professionals, or students looking to gain a quick orientation the the dam safety issue. Also, this site explains the major problems and the range of solutions being considered with resources. But this web site is not intended to advocate particular solutions or institutions.

Hopefully, I hope this web site could help everyone reading this article have better understanding and get knowledge about dam safety issue in California.

Also, I appreciate professor Jay Lund, Ross Boulanger, and Bruce Kutter, who inspire me to do this extensive work and make it happen. I am happy with them in Davis.


DongSoon Park
Graduate Student, Ph.D course, UC Davis PTL!

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8. Sources and References

In order to understand a dam safety issue, we need to look at firstly general dam safety guideline that is currently applied, and also we should past overall cause of dam failure and remediation histories. For this, there are some valuable sources and references to read as follows.

Must-See Online Resources on Dam Safety

National Dam Safety Program / Federal Emergency Management Agency (FEMA)
http://www.fema.gov/plan/prevent/damfailure/ndsp.shtm
FEMA has been working to protect Americans from dam failure through the National Dam Safety Program (NDSP). The NDSP provides information about dam safety research and training.

Dam safety, FEMA
http://www.fema.gov/plan/prevent/damfailure/index.shtm
This web-site gives a great source of dam failure information, the National Dam Safety Program (NDSP), dam safety guideline, and technical manuals and guides, etc.

Guidelines for Dam Safety, FEMA
http://www.fema.gov/plan/prevent/damfailure/publications.shtm#0
Another essential dam safety guideline in nationwide is FEMA federal guidelines for federal agency dam owners and regulators. The guidelines may also be used by non-federal dam owners, regulators, and operators. It includes:

Major Events in Dam Safety in the U.S.
http://npdp.stanford.edu/chronology.html
Chronological summary of major events in dam safety issue is provided.

Division of Safety of Dams (DSOD) / Department of Water Resources (DWR)
http://damsafety.water.ca.gov/
In California, the best dam safety relating organization is Division of Safety of Dams in Department of Water Resources. The California Water Code entrusts this regulatory power to the Department of Water Resources which delegates the program to the Division of Safety of Dams. Information regarding the supervision of dams is addressed here to better serve the public, dam owners and applicants.

Association of State Dam Safety Officials (ASDSO)
http://www.damsafety.org/
ASDSO is a non-profit organization of state and federal dam safety regulators, dam owners/operators, dam designers, manufacturers/suppliers, academia, contractors and others interested in dam safety. This site address the dam safety issue and state dam safety programs.

http://www.damsafety.org/map/state.aspx?s=5
Useful fact sheet for the California dam safety program is given.

US Bureau of Reclamation (USBR), Dam Safety
http://www.usbr.gov/ssle/dam_safety/
This site provides the Reclamation's Safety Evaluation of Existing Dams (SEED) program and overall good information on dam safety issue.

USBR, dam database
http://www.usbr.gov/dataweb/dams/

Engineer Manuals, United States Army Corps of Engineers
http://www.usace.army.mil/publications/eng-manuals/
A good source of engineering manuals on dams and levees, also other geo-structures.

United States Society on Dams
http://www.ussdams.org/index.html
Publication and information about dam engineering, construction, planning, operation, performance, rehabilitation, decommissioning, maintenance, security and safety

Summary of USSD White Paper on Dam Safety Risk Assessment
http://www.ussdams.org/reports.html
This site introduces USSD publication White Paper on Dam Safety Risk Assessment.

National Inventory of Dams
http://crunch.tec.army.mil/nidpublic/webpages/nid.cfm
With the National Dam Inspection Act (P.L. 92-367) of 1972, inventory dams located in the United States are provided in this site.

Dam, Hydropower and Reservoir Statistics
http://www.ussdams.org/uscold_s.html
The USSD Committee on Register of Dams gives summarized table about United States dams, hydropower projects and reservoirs.

Educational Site on Dam and Water Resource
http://crunch.tec.army.mil/nidpublic/webpages/USSD_Water_Dams/index.html
This web-site describes well regarding Why Dams & Water Resources, and Water Availability, etc.


Useful Readings regarding General Dam Safety Issue

FEMA dam safety guidelines
· Emergency Action Planning for Dam Owners (FEMA 64)
· Earthquake Analyses and Design of Dams (FEMA 65)
· Federal Guidelines for Dam Safety (FEMA 93)
· Selecting and Accommodating Inflow Design Floods for Dams (FEMA 94)
· Glossary of Terms (FEMA 148)
· Hazard Potential Classification System for Dams (FEMA 333)

Bharat Singh, R. S. Varshney, Engineering for Embankment Dams, A.A.Balkema, 1995

Donald H. Babbitt, Improving Seismic Safety of Dams in California, Department of Water Resources, Division of Safety of Dams

Dean W. Smith, Surveillance Measurements within California’s Dam Safety Program, Division of Safety of Dams, Department of Water Resources, State of California

Emil R. Calzascia and James A. Fitzpatrick, Hydrogogic Analysis within California’s Dam Safety Program, Division of Safety of Dams, Department of Water Resources, State of California

James L. Sherard, Earth and Earth-Rock Dams; Engineering Problems of Design and Construction, John Wiley and Sons, 1967

Richard J. Baines, Dam Inspections, California Division of Safety of Dams, Department of Water Resources, 1999.01


References for Dam Safety due to Earthquake

Gilles Bureau, Richard L. Volpe, Wolfgang H. Roth, Takekazu Udaka, Seismic Analysis of Concrete Face Rockfill Dams, Concrete Face Rockfill Dams - Design, Construction, and Performance, ASCE, 1985

ICOLD Committee on Materials for Fill Dams, Concrete Face Rockfill Dams, Concepts for Design and Construction, Nov. 2004

Luis Arrau, Ismael Ibarra, Guillermo Noguera, Performance of Cogoti Dam Under Seismic Loading, Concrete Face Rockfill Dams - Design, Construction, and Performance, ASCE, 1985

M. Yener Ozkan, A Review of Considerations on Seismic Safety of Embankments and Earth and Rockfill Dams, Soil Dynamics and Earthquake Engineering 17 (1998) 439~458, Elsevier

Nasim Uddin, A Dynamic Analysis Procedure for Concrete-faced Rockfill Dams Subjected to Strong Seismic Excitation, Computers and Structures 72 (1999) 409~421

Martin Wieland, Earthquake Safety of Concrete Dams and Seismic Design Criteria for Major Dam Projects, www.energy.poyry.com/linked/en/hydropower/pu_en_earthquake_s_concrete.pdf

W.F.Marcuson, P.F.Hadala, R.H.Ledbetter, Seismic rehabilitation of Earth Dams, Journal of Greotechnical Engineering, Vol. 122, No. 1, 1996, ASCE

Manish Shrikhande, Susanta Basu, A Critique of the ICOLD Method for Selecting Earthquake Ground Motions to Design Large Dams, Engineering Geology 80, pp 37–42, 2005, Elsevier

Martin Wieland, Seismic Aspects of Dam Design, www.melbournewater.com.au/.../waterway_diverters/forms_and_guidelines/Dam_Safety_Emergency_Plan.pdf


Case History References used in this Webpage

The scope of this case history about dam failure and remediation is limited to the dams in California except Teton Dam case history, which is dramatically a big failure. More worldwide information can be referred some recommended sources in this website.

Lower San Fernando

Bardet, J. P., and C. A. Davis, Performance of San Fernando Dams During 1994 Northridge Earthquake, Journal of the Geotechnical Engineering Division, Vol. 122, No. 7, 1996, pp. 554–564.

Davis, C. A., and J. P. Bardet, Performance of Two Reservoirs During the 1994 Northridge earthquake, Journal of the Geotechnical Engineering Division, Vol. 122, No. 8, 1996, pp. 613–622.

Seed, Lee, Idriss, & Makdisi (1975). The slides in the San Fernando Dams during the Earthquake of February 9, 1971, J.Geotech. Engrg. Div., ASCE, 101(GT7), 651-688.

Seed, Seed, Harder, Jong (1989), Re-Evaluation of the Lower San Fernando Dam, Contract report GL-89-1 for the US Army Corp of Engineers, Washington, DC.

LA Dam

http://quake.usgs.gov/prepare/factsheets/LADamStory/

Austrian Dam

Chris Kramer, Michael D. Lee, Preparedness for Dam Failures in the San Francisco Bay Area, Natural Hazards Review, Vol. 5, No. 1, 2004, ASCE

City of San Jose, Emergency Operations Plan, 2006

I.M. Idriss, Ralph J. Archuleta, Evaluation of Earthquake Ground Motions draft 06.5, 2007, www.ferc.gov/industries/hydropower/safety/guidelines/eng-guide/chap13-draft.pdf -

John Vrymoed, Wallace Lam, Earthquake Performance of Austrian Dam, California during the Loma Prieta Earthquake, Division of Safety of Dams, Department of Water Resources, http://damsafety.water.ca.gov/seismic_austrian.cfm

L.F. Harder, Jr., J.D. Bray, R.L. Volpe, R.L. Volpe, K.V. Rodda, Performance of Earth Dams during the Loma Prieta Earthquake, The Loma Prieta, California, Earthquake of October 17, 1989-Earth Structures and Engineering Characterization of Ground Motion, U.S. Geological Survey Professional Paper 1552-D, 1998

San Luis Dam

Boulanger, R. (2008). San Luis Dam Slide. Retrieved 2 4, 2008, from Ross W. Boulanger Faculty Page Photo Album:
http://cee.engr.ucdavis.edu/faculty/boulanger/geo_photo_album/Embankment%20dams/San%20Luis%20dam%20slide/San%20Luis%20dam%20-%20main.html

Duncan, J. M., & Stark, T. D. (1989). The Causes of the 1981 Slide in San Luis Dam. Raleigh, North Carolina: Department of Civil Engineering, College of Engineering, Virginia Polytechnic Institute.

Reclamation, U. S. (1994). Central Valley Project The San Luis Unit West San Joaquin Division. Retrieved 24, 2008, from Reclamation Managing the Water in the West: http://www.usbr.gov/dataweb/html/casanluish.html#Post%20Construction%20History

Baldwin Hills Reservoir

CDWR (1964). Investigation of Failure Baldwin Hills Reservoir. Department of Water Resources, The Resources Agency, State of California, April.
Jansen, R. B. (1988). Advanced dam engineering for design, construction, and rehabilitation. Van Nostrand Reinhold, NY.

St. Francis Dam

Jansen, R. B. (1988). Advanced dam engineering for design, construction, and rehabilitation.
Van Nostrand Reinhold, NY.

Teton Dam

Teton Dam Failure Review Group, Failure of Teton Dam – Final Report, by U.S. Department of the Interior, January 1980.

Coyote Dam

Abrahamson, Norman A., M. EERI, and Robert Darragh, The Morgan Hill Earthquake of
April 24, 1984 – The 1.29g Acceleration at Coyote Lake Dam: Due to Directivity, a Double
Event, or Both?, Earthquake Spectra, Vol. 1, No. 3, May 1985, pp. 445-455.

Boore, David M., Vladimir M. Graizer, John C. Tinsley, and Anthony F. Shakal, A Study of Possible Ground-Motion Amplification at the Coyote Lake Dam, California,

Bulletin of the Seismologial Society of America, Vol. 94, No. 4, August 2004, pp. 1327-1342.

Sherard, J. L., L. S. Cluff, and C. R. Allen, Potential active faults in dam foundations, Geotechnique, Vol. 24, No. 3, 1974, pp 367-428.

Sherard, James L., Sc.D., Richard J. Woodward, M.S., Stanley F. Gizienski, M.S., and William A. Clevenger, B.S., Earth and Earth-Rock Dams, Engineering Problems of Design and Construction, John Wiley and Sons, Inc., 1963

Tepel, Robert E., M. EERI, The Morgan Hill Earthquake of April 24, 1984 – Effects on Facilities of the Santa Clara Vallet Water District, Earthquake Spectra, Vol. 1, No. 3, May 1985, pp. 633-656.

Hell Hole Dam

http://cee.engr.ucdavis.edu/faculty/boulanger/geo_photo_album/GeoPhoto.html

Calaveras Dam

Ross Boulanger and Ronn S. Rose, Hand-out and Presentation material, ECI288 Dam Engineering Class, 2008

7. Conclusion

What matters most in dam safety is not an issue of conflicts or interests of each party, but an issue of preventing crucial disaster when dam fails. Therefore, dam safety should be always considered in the first priority. But when we face with making sure a dam safety, sometimes conflicts occur regarding which method or solution is the best way in terms of both safety and economic aspects. Thus, the best decision-making should be made within angles of reasonable cost and rational decision with appropriate amount of conservatism and reasonable confidence.

6. Current Efforts Underway

National Dam Safety Program has been enforced for every kind of ownership of dams in California. Dam safety issue is still actively activating for all stakeholders and interests. The table below provided by ASDSO (2005) shows how the National Dam Safety Program has improved dam safety in California.

In order to long-term dam safety assurance, various efforts are being taken. Especially, in California, seismic hazard is never eliminated. A DSOD report (Babbitt) in 1993 has revealed that at least 94 dams have been improved for seismic stability. And that effort is currently going on. The main leading organization is DSOD and USACE.

To make sure safer dam design, construction, and operation, current efforts should be sustainable, coherent, and technically improved.

Here in this section, current efforts underway of US Army Corps of Engineers are briefly introduced using some progressive cases. Material and photos are courtesy of USACE.

6.1 Dam Safety Assurance Program

Recently, seismic reevaluations are widely reviewed not only for embankment or concrete Dam, but also for appurtenant structures. Also, hydrologic capacity and spillway adequacy issues are very core of most of dam engineers worldwide. In addition to these, other dam safety relating program such as seepage is going on now.

Corps began the screening portfolio risk assessment in 2005. “Risk” is (probability of failure) x (consequence of failure). USBR has been doing this for > 10 years. Approximately 10% was screened in 2005, 2006, 2007 (30% of total inventory of 604 dams). Each of them was classified in “Dam Safety Action Classes (DSAC)”. The purpose is to fund the higher risk projects in terms of “fix the worst first”.

Current and future Investigations

6.2 Isabella Dam Case

The Main Dam is 185 ft high, zoned earth fill (nearly homogeneous) dam with foundation primarily composed of granitic bedrock except downstream area of recent thin alluvium. It has 6.5 feet freeboard over spillway design flood and 28.0 feet freeboard over gross (full) pool.

The Auxiliary Dam is 100 ft high and has homogeneous silty sand (very dense), 120 ft of alluvial soil foundation.

Courtesy of Ron Rose, USACE

Recent research illustrates some major deficiencies of Isabella dam as below.

Hydrologic deficiency
- Spillway capable of “safely” passing 33% of PMF
- PMF = 542,000 cfs, historic max = 120,000 cfs

Seismic deficiency
- Began reevaluation in 2003
- Study began in earnest in 2005
- Has accelerated greatly due to screening level
- risk assessment: Previously unrecognized seismic sources, Poor foundation (aux dam), Conduit/Tower PFM, Kern Canyon Fault, Newly found faults

Seepage
Auxiliary Dam
- Thick, permeable foundation, Homogeneous dam, but No effective seepage control
- History of seepage, Conduit in alluvium
- Seepage collars, vertical cut, no filter material
- Newly aware that the seepage was potentially a much more serious problem, immediately began an in-house seepage study

Isabella – current and future tasks
- Fault characterization; LiDAR, Trenching, Update seismic hazard analysis
- Dam & Foundation characterizations; Drilling, In-situ density testing, Deformation modeling
- Risk Analysis

Auxiliary dam
- Major remediation for seepage and seismic

Main dam
- Major remediation for seismic (also seepage)
- Remove recent alluvium and Needs to incorporate modern seepage control features

Hydrologic deficiency
– Major remediation needs to safely pass (with freeboard) 100% of PMF “do no harm”
– don’t increase frequency of downstream flooding

6.3 Martis Creek Dam

Its purpose is flood Control and future water supply. This dam was constructed in 1972.
- Elevation, top of dam 5858.0 ft.
- Gross Pool (spillway elev.) 5838.0 ft.
- Freeboard above spillway design flood pool 5.1 ft.
- Maximum height 113 ft.
- Storage capacity: Gross pool 20,400 ac. ft., Spillway design flood pool 34,600 ac. ft.

(Courtesy of Ron Rose, USACE)

Identified potential deficiencies

Hydrologic: Seepage, Overtopping potential
- Liquefaction of dam foundation (upstream and downstream) when earthquake occurs.
- Long history of test fills and associated seepage problems (1973, 1974, 1978, 1980, 1986, 1995
- 1995 test fill was pool of record: approx. 5833 (gross – 5 feet). Terminated due to excessive seepage, some boils, and seepage from spillway area.
- Spillway is capable of safely passing 49% of the PMF. PMF overtops dam by 1.1 feet

Seismic
- Liquefaction/deformation hazard of foundation materials
- Seismic sources are capable of creating large ground motions at Martis Creek Dam

Remediation concepts
- Hydrologic is easy – widen spillway
- Seepage: Cutoff wall, Lower spillway invert, etc…are being considered
- Seismic: likely very difficult and costly, various methods are being conceived


6.4 Hidden Dam

(Courtesy of Ron Rose, USACE)

One of problems in this dam is seepage issue. Seepage areas and quantities have generally been on the increase with every inspection and also noticed by project staff. Now, urgent seepage study and spillway adequacy study is going on.

(Courtesy of Ron Rose, USACE)

6.5 Black Butte Black Butte Dam

(Courtesy of Ron Rose, USACE)

Hydrologic
- Spillway can only “safely” pass 78% of PMF
- Full PMF overtops entire dam by 1.0 feet

Seismic
- Seismic sources are capable of creating large ground motions at Black Butte Dam (~1g)
- Foundation judged to be liquefiable, and possibly portions of the embankment screened in 2005

More detail study is going on now.


6.6 New Hogan Dam

(Courtesy of Ron Rose, USACE)

One of problem in this dam is major earthquake source exists nearby. And fundamental study is being developed now.


6.7 Farmington Dam

(Courtesy of Ron Rose, USACE)

Farmington dam has a problem of excessive underseepage. This dam body has a pervious layer bounded by impervious embankment and relatively impervious substratum. It has a record of flood in 1998 and poor performance of embankment and foundation. At that time, damage to the upstream face due to wave action occurred, and downstream underseepage and boils made people practice flood fighting.

(Courtesy of Ron Rose, USACE)

Currently, more detail investigation is being done.

5.3 Dam Remediation and Rehabilitation

Through regular or emergency inspection and instrumentation, unstable dams locally or fully are needed to be taken with appropriate measures considering safety and costs. From my opinion, the best method can be determined to ensure reasonable amount of conservative for safety aspect, plus reasonably available economic costs for that. In other words, safety should of course, be the first priority. Also, price to pay is another angle to select alternatives. For example, for the earthquake problems, we need to consider the probability in terms of “how rare?”, and also, “rational costs” of doing certain method.

Therefore, in order to find the best alternative, well-organized structured decision-making process below is necessary like Gregory and Keeney (1994) method or rational planning (Lund, 2008).

- Problem definition
- Objectives
- Alternatives
- Consequences and evaluation
- Tradeoffs
- Uncertainty and Risk Tolerance
- Making decisions

Prior to suggestion of practical dam remediation methods, remediation case history review is helpful to understand major considering alternatives.


Seepage and Piping

Excessive seepage or piping can cause sudden devastating failure of dams. From my experience, a good exemplary symptom of this is increase of leakage flow or turbidity, or sometimes sinkhole on the crest. A very good remediation measures are described by “White paper for the ASDSO Seepage Workshop, Oct., 2000, Talbot, Poulos, and Hirschfeld” and personally it is preferred to use this methods.

Remedial measures for preventing piping are aimed at controlling seepage so that the seepage does not cause internal erosion of soil from the embankment, foundation, or abutments of a dam. Remedial measures for preventing piping may not reduce the rate of seepage and, in fact, often increase the rate of seepage.
Remedial measures for reducing water loss are aimed at reducing the quantity of seepage through the embankment, foundation, and abutments. Although such measures may reduce the pressures and the rate of water flow through a dam, its foundation, or abutments, it is nevertheless vital to install proper drainage systems on the downstream side of the dam as the primary line of defense against piping.

The addition of downstream drainage is usually the best solution for controlling seepage in embankment dams. Control of seepage can be accomplished by:
- adding a drainage zone by removing a portion of the downstream slope and constructing a new filter-drain covered by a reconstructed downstream slope;
- adding a drainage zone by constructing a filter-drain on the existing downstream slope and covering the drain with a new downstream shell zone;
- adding an embankment chimney drain to the dam by trenching into the dam and backfilling the trench with appropriate filter material;
- installing a toe drain extending into the foundation at the toe of the dam;
- installing a downstream, weighted, blanket drain;
- installing downstream relief wells;
- cleaning existing clogged drains; and
- cleaning existing relief wells.

The solution that is best-suited to a particular dam will depend on a variety of factors. Some of the more important factors to be considered are a) the embankment zoning and foundation stratigraphy, b) the seepage patterns and quantities, c) seepage pressures, d) the ability to lower the reservoir for construction, e) the availability of construction materials, and f) property constraints and construction access.

Also, methods available to reduce the amount of seepage include:
- an upstream blanket constructed with low permeability materials (e.g., soil, asphalt, soil cement, roller compacted concrete, concrete, or a geomembrane);
- a “cutoff” or facing on the upstream slope of the dam constructed with low permeability material (e.g., soil, soil and bentonite mixtures, soil cement, roller compacted concrete, concrete, asphalt, metal, masonry, or a geomembrane); and
- an internal “cutoff” within the dam and foundation constructed of low permeability material (e.g., concrete, soil-bentonite mixtures, soil-cement mixtures, sheet piling, or grout) – sometimes called diaphragm walls and constructed with such methods as slurry trench excavations, deep soil mixing, or jet grouting.


Main Resource: James R. Talbot, Steve J. Poulos, and Ronald C. Hirschfeld, White paper for the ASDSO Seepage Workshop, Oct., 2000, Denver


Seismic mitigation

According to Marcuson et al. (1996, JGGE), among 52 dams having problems, 22 dams had operational fixes (pool level restrictions), and 30 dams had engineering fixes. Also,

Of 38 researched dams:
• 11 cases: remove and replace
• 8 cases: upstream and/or downstream
• 6 cases: Increase freeboard (raise crest; lower pool)
• 5 cases: Remove dam from service, or replace with new dam
• 8 cases: Soil improvement
• Stone columns: Hinkley dam in NY; John Hart dam in B.C.; Mormon Island dam in CA.
• Dynamic compaction: Jackson Lake dam; Mormon Island dam in CA; Steinaker in Utah.
• Drains: Gravel piles at Kingsley in Nebraska.
• Compaction grouting: Pinopolis West dam in SC Piles MS
• Piles: Sardis dam in MS.

Of course, right methods depend on various factors in that particular dam site and conditions.

In California, major dam safety threatening factor is much oriented toward seismic mitigation because there are so many active faults and always have some potential hazard.

In view of many researches, my opinion is firstly, we should select some possible methods for liquefaction mitigation through smart decision making process, and then, the most recommended method should be considered based on the reasonable safety standard and costs.

There are some key considerations when we think about ground improvement for a dam safety.
- Design ground motions
- Will “liquefaction” be triggered?
- Consequences of liquefaction?
- Ground deformations (e.g., flow, lateral spreading, settlement)
- Effect on the dam (Safe? Functional? Repairable?)
- Cost of damage (direct repair costs & loss-of-use costs)
- What level of performance is required?
- Life Safety?
- Functionality?
- Time for repairs?

When we firstly search for multiple alternatives for seismic remediation or mitigation, the following charts is helpful at the very beginning of stage.

Earthquake induced Liquefaction Mitigation (Jim Mitchell 2008)

Detail description of each method is introduced in the webpage. Some typical ground improvement methods to reduce consequences of liquefaction in dams are as follows:

• Vibro-methods:
- Vibro-rod methods -- vertical vibration of a penetrating probe
- Vibroflotation -- a horizontally vibrating probe
- Vibro-replacement: the probe cavity is filled with imported material
(e.g., crushed stone, gravel, sand, or even concrete)
• Deep dynamic compaction (DDC)
• Deep soil mixing (DSM)
• Grouting
• Compaction grouting
• Jet grouting
• Permeation grouting
• Drains (area coverage, perimeter curtains)
• Blasting
• Biological treatment – waste products of bacteria may stabilize soil

In addition to this, other types of alternatives to ground improvement should be considered simultaneously.

- Relocate to a better site?
- Modify the dam to withstand effects of liquefaction?
e.g., Tie footings together with grade beams?
- Manage the risk.
Repair damage versus prevent it (cost of lost functionality)?
Different performance levels for different parts of the system?


Overtopping

For the overtopping due to heavy rainfall and lack of free board, the best method is to increase reservoir capacity or spillway capacity. From my personal experience, if a dam has no spillway or has a weir with no flood control function, recent extraordinary weather pattern can cause increase of PMP or PMF. Thus, spillway discharge rate should be increased for the assumption of emergency.

In addition to that, downstream river should be fixed for modified design flood of the stream. Sometimes we can find that dam flood capacity is enough, but a downstream flow capacity when spill of water is remarkable insufficient. Subsidiary spillway installation in type of tunnel or open cut, morning glory can be considerable to prevent overtopping. Or raising a dam height and get more freeboard is another good method to think about.

However, it causes a lot of costs to construct both cases. Therefore, reasonable feasibility study should be proceeded.


Slope Stability

Slope failure problem in dam body is correlated to the happening of earthquake or static instability of dam body. Especially, for the cases of the following time stage is very crucial for slope stability and proper analysis should be taken.
- End of construction (short-term)
- Steady state seepage (long-term)
- First filling (many case histories)
- Earthquake
- Sudden draw-down

Analysis can be available using limit equilibrium analysis, FEM, FDM programs. For the detail factor of safety of each item, USACE slope manual is preferred to use.

For the slope stabilization, various kinds of alternatives are recommended in terms of conditions of dam. Dam owners and engineers should decide the optimum method considering proper level of safety and economic costs.
- upstream and downstream berm or upstream blanket
- upstream slope protection, riprap, etc.
- upstream impermeable barrier (membrane)
- grouting into dam body
- put some horizontal ramp
- make decent slope angle

5.2 Dam Surveillance

For about 8 years experience of dam engineering, regular dam instrumentation and check up as well as visible inspection are great resources of dam health. This activity is like regular check of our body during our lifetime. And through this pre-check tells us where we are, what we need, and what we lack of, to stay in health. So this is very basic, core process to keep dam safety.

In California, surveillance measurements of dams are the responsibility of the owner and are subject to supervision by the Department of Water Resources, as specified in the State Water Code. The review of owner transmittals of surveillance data plays a significant part in the State's dam safety program, serving to supplement the primary State surveillance activity, periodic inspections. Very good guide is shown in the “Surveillance of Existing Dams by Dean Smith, 1989”.

Essentially, California dam owners are responsible for:
- Instrumenting each dam at their own expense to the minimum required for safety, as determined by the State.
- Collection of the surveillance measurements.
- Timely evaluation of their measurements.
- Transmitting to the State, at regular intervals, a copy of their surveillance measurements with an evaluation.

On the other hand, the State is responsible for:
- Regulating dams and reservoirs to safeguard life and property including supervision of surveillance measurements.
- Determining the minimum amount of instrumentation needed for each dam to safeguard life and property.
- Verifying that each dam and reservoir is operated and maintained in a safe manner, including periodic review of the dam owners' surveillance programs.

5.1 Dam Inspections

From my own experience, sometimes engineers or owners overlook importance of very basic, but crucial check for dam safety. Dam inspections are the best solution to prevent too-late unstable condition of dam. Practically, DWR gives an instruction for dam inspections (Richard Baines, DSOD / DWR, 1999).

Regular inspection is simple, but gives us a plenty of symptoms of current dams. The inspecting engineer's eyes are the best instrument for reviewing the current status of a dam and reservoir and his brain is the best computer for analyzing the results. We should remember to look at everything on and around the dam and question anything that is out of the ordinary or changed. Also, it is very important to take lots of notes and photographs and adequately document the findings.

The dam should be judged to be: 1, satisfactory for continued operation; 2, satisfactory for continued operation with some qualifying statement, like being subject to the review of some aspect (i.e., seismic stability); 3, satisfactory as operated at a restricted level; or 4, unsatisfactory. For legal protection to limit liability for what is concluded, it is important not to state that the dam "is" satisfactory but is "judged" safe or satisfactory and to state the basis for the conclusion.

The laws governing dam safety are equal in treatment of all dams, including requiring corrective action. It is the engineer's responsibility to use judgment in assessing the severity of a deficiency, and what time schedule for rectifying the situation is reasonable, taking into account the damage potential. The damage potential is based on the size of the dam and reservoir, the estimated population that would have to be evacuated and the estimated monetary loss to property from a failure. However, should the integrity of the dam be threatened, immediate response is ordered.

5. Promising Solutions

4.3 Human and Economic Consequences

There are many aspects of economic and human effects when dam failure occurs. The general impact of dam failure is so huge as we can easily see the facts of historical records.

According to the some reports recently, dam failure consequences were very tragic as follows. Dams continue to age and deteriorate. They demand greater attention and investment to assure their safety.


Table. Human and Economic Consequences of Dam Failure (Wayne Graham, June 26, 2001)

4.2.6 Teton Dam

It was located on Teton River in S.E. Idaho. River diversion started in June 1973. Dam was topped out in November 1975. Maximum embankment height was 305 feet above valley floor and 405 feet above lowest excavated point in the foundation. Crest length was 3,100 feet. Crest elevation was 5,332 feet.

Failure was due to piping of Zone 1 material. Inner Zone 1 is composed of low-plasticity silt from windblown deposits, and outer Zone 2 was filled with sands & gravels from flood plain. Foundation was mostly rhyolite welded ash-flow tuff, with prominent and abundant joints, some basalt on left side, and Tuff underlain by sedimentary formations.

The actual mechanism causing piping is uncertain due to the complete erosion of the failed section.

Possible mechanisms leading to piping include:
- Seepage along the fill-to-rock interface, or along the top of the grout curtain, in the right key trench.
- Seepage along a low-density, high permeability lens within or adjacent to the right key trench.

Infractions of specifications were documented in:
- Preparation of rock surface on sidewalls of the key trench was inadequate.
- Grouting of the grout curtain, especially at shallow depths, was inadequate. Upper ends of some grout holes were not grouted.
- Inspection procedures for the Zone 1 fill were not adhered to early in construction. A "wet seam" of lower-density and higher permeability was identified in the lower portion of Zone 1.

Failure of Teton Dam, Early afternoon, June 5, 1976, Final Report by U.S. Dept. of the Interior, 1980

Sources:
- Ross Boulanger, Teton Dam failure, In-class handout, 2008
- Failure of Teton Dam – Final Report, by U.S. Department of the Interior, Teton Dam Failure Review Group, January 1980.
- Failure of Teton Dam – A Report of Findings, by U.S. Department of the Interior, Teton Dam Failure Review Group, April 1977.

4.2.4 Calaveras Dam

Calaveras Dam was completed on March 3, 1926 and failed on March 23. Calaveras Dam is located approximately 10 miles northeast of the city of San Jose. This dam had a height of about 200 ft above the streambed of Calaveras Canyon and a crest length of approximately 1200 ft, and contains approximately 2,646,000 cubic m of embankment. Construction of the dam as a hydraulic fill was started in 1913, and the structure was not completed until 1925. The reservoir has a storage capacity of about 100,000 acre-feet at apillway crest elevation 752.5, and a drainage area of about 135 sq miles.

This dam failure was happened right after the construction completion. Original Investigators concluded that the main reasons of failure were that very fine material was sluiced too much and core layer was incapable of drainage.

Calaveras Dam failure, courtesy of Ronn Rose, USACE

Sources:

- California Department of Water Resources, Division of Safety of Dams.
- Olivia Chen Consultants (2002). Report on Seismic Stability of Calaveras Dam. Prepared for San Francisco Public Utilities Commission.
- Jack Wulff, Advanced dam engineering for design, construction, and rehabilitation, 1988, Edited by Jansen, Van Nostrand Reinhold, NY.

4.2.3 St. Francis Dam

St. Francis Dam was completed May 1926 and reservoir was filled. This dam was 205-ft high, 700-ft long. Dam was failed 11:57 p.m., March 12, 1928. Official death toll was 495.

St. Francis Dam was the key facility of the Los Angeles Bureau of Water Works and Supply system. The arched concrete gravity structure was located approximately 45 miles north of LA. The reservoir, which had a capacity of 38,000 acre-feet was nearly full at the time of the failure.

No witness of the actual failure survived the dam’s final minutes. At 11:47 pm, only 10min. preceding the disaster, the operator at the powerplant upstream from the reservoir called the lower plant, and nothing unusual was reported. At 11:58 pm, a break occurred in the power line of the Southern California Edison Company in the canyon downstream. The dam failure undoubtedly happened almost instantly. In about 70 min., practically the entire reservoir storage had been discharged. The flood wave attained an estimated maximum depth of 125ft in the first mile downstream from the dam. Peak outflow probable was greater than 500,000 cfs.

St. Francis dam after failure, Courtesy by DSOD

Blocks of the dam were washed thousands of feet from the site. A wide slide was active on the left abutment for at least two weeks following the disaster. At the time of its failure, St. Francis Dam was less than two years old. The 205-ft-high dam was arched on a radius of 500 ft to the upstream face at the top. The dam had no inspection gallery, and the foundation was not pressure-grouted. Uplift relief under the dam was provided only at the river channel.

Lessons Learned

- Site exploration must include a search for old or potential slides and an evaluation of their possible effects on the dam.
- Consideration must be given to foundation capability under a full range of foreseeable conditions, including shearing and weakening due to wetting.
- The need for foundation grouting has to be carefully assessed.
- Inspection galleries may be of high value in concrete dams.
- The engineering and the surveillance of an important dam should be assigned to an interdisciplinary team so that all potentially adverse conditions can be fully evaluated.


Sources:

Robert Jansen, The St. Francis Dam Failure, Advanced dam engineering for design, construction, and rehabilitation, 1988, Van Nostrand Reinhold, NY.
CA DSOD files (Courtesy of S. Verigin).

4.2.2 Baldwin Hills Dam

On December 14, 1963, an unpredicted flow of water occurred at Baldwin Hills Dam in LA, California. The water came from drains under the reservoir lining. Muddy leakage was discovered downstream from jthe north side of the reservoir. At 2:20 pm, lowering of the reservoir water level revealed a 3-ft-wide break in the reservoir’s inner lining. Water broke violently through the downstream face of the dam. By 5:00 pm, the reservoir had emptied, revealing a crack in the lining extending across the reservoir bottom in line with the breach in the dam.

Failure progress
• At 11:15 am, caretaker observed excessive flow in the drainage inspection chamber beneath the reservoir.
• At 1:30 pm, the LAPD was requested to start evacuation.
• At 2:20 pm, sigalert broadcast on radio and television.
• At 3:38 pm, the dam was breached.

This dam was constructed on April 18, 1951. Located at the head of a northward-draining ravine, the reservoir was formed by the dam on the north side and compacted earth dikes on the other sides. Designed as a homogeneous earthfill, the dam was 232ft (71m) high and 650ft (198m) long.

The embankments were constructed of materials excavated from the reservoir bowl. Two separate underdrain systems were provided, one to drain the foundation under the earth embankments and the other to collect seepage passing through the earth lining and convey it through a central observation and measurement chamber to an outfall pipe.

As a result, five people died & scores of homes destroyed. Total damage estimated at $15,000,000. Early warning and prompt action had averted a much greater tragedy.

2:20 pm 3:25pm
3:30 pm 3:38 pm

3:40 pm

Photo: Baldwin Hills Dam, progress of failure per time, Courtesy: Los Angeles Times

Lessons Learned (Leps and Jansen)

- Foundations in erodible rocks must be thoroughly explored to disclose any preexisting cavities or other defects.
- The total prevention of leakage into a reservoir foundation over the lifetime of the facility may be unattainable under usual circumstances.
- The possibility of differential fault movement unrelated to tectonic activity must be considered.
- Drains should be amply sized and provided with access, where possible, to facilitate maintenance.
- Surveillance of a reservoir must be extended to its environs and to the consequences of adjacent developments and physical changes.

Resource:
- Investigation of Failure – Baldwin Hills Reservoir, California Department of Water Resources, 1964
- Ross Boulanger, Baldwin Hills Reservoir Failure 1963, In-class handout, 2008
- Thomas Leps and Robert Jansen, The Baldwin Hills Reservoir Failure, Advanced Dam Engineering for Desing, Construction, and Rehabilitation, edited by Robert Jansen, 1988, Van Nostrand Reinhold, NY.

4.2.1 San Luis Dam

The San Luis Dam (now called the B.F. Sisk Dam) was completed in August 1967. It was built on the Los Banos Creek and is used primarily for agricultural storage for the South Valley farmers. In 1981, on September 4, workers noticed rocks sliding down the upstream face of the dam. The slide occurred in deep seated failure and the failure surface extended through the engineered zones and into the native slopewash material. Investigation of the slide led to the conclusion that the wrong strength parameters for the slopewash material were used for stability analyses.

The slopewash material is deposited primarily by rain dragging small clay particles downslope from the surrounding hills. The construction specifications for excavation to the foundation were that the soil had to be stronger than the fill to be placed over it. In California’s Central Valley, the temperatures easily reach over 100 degrees for days at a time, causing significant evaporation losses in surface soils. In its desiccated state, the slopewash material exhibited strength characteristics that would seem desirable for a dam foundation. However, after extensive post failure laboratory testing on the slopewash material was performed, it was determined that the residual strength, and not the previously used “fully softened” strength should be used in stability analyses.

Fortunately, no one was hurt, and no water was lost the slide occurred. The engineering lesson to be learned from this event is that the engineer should have a good understanding of the behavior of the soil zones influenced by the dam under fully inundated conditions as well as the cyclic response of the soil mass due to drawdown.

Deep seated failure of San Luis Dam, Photo by Duncan

Slopewash: The action of water from rain or melted snow carrying (washing) soil down a slope.

Resource:
- Karl Schwartz, The 1981 Slide at the San Luis (Sisk) Dam, Dam Case History report, 2.06, 2008
- Boulanger, Ross, San Luis Dam Slide, http://cee.ucdavis.edu/faculty/boulanger/geo_photo_album/
- Duncan, J.M., & Stark, T.D. (1989), The Causes of the 1981 Slide in San Luis Dam, Raleigh, North Carolina: Dept. of Civil Engineering, Virginia Polytechnic Institute.

4.1.5 Sheffield Dam

The Sheffield Dam was 7.6m high dam constructed in 1917. The body of the dam was composed of silty sand and sandy silt, the upstream slope was faced with a 1.2m thick clay blanket protected by a 12.5cm concrete facing and extended 3m into the foundation to serve as a cut-off. Compaction was done by routing construction equipment over the fill. The foundation consists of a layer of terrace alluvium 1.2 to 3m thick overlying sandstone bedrock.

The earthquake main shock occurred at 6:42 am on 29 June, 1925. The magnitude of the earthquake was assessed at 6.3 with the epicenter located about 12kn N.W. of the dam site and maximum ground acceleration of 0.15g of the site. Though there were no eye witnesses to the failure, subsequent inspection reports indicated that sliding occurred near the base of the embankment, causing a section about 90m in length to move bodily downstream as much as 30m, breaking up as it did so. There can be little doubt that a movement of this extent was related to liquefaction induced by shaking.

The Sheffield Dam after the 1925 earthquake (Earthquake Engineering Research Center)

Resource: Bharat Singh and R.S. Varshney, Engineering for Embankment Dams, 1995, A.A.Balkema

4.1.4 Coyote Dam

Coyote Dam experienced almost no damage during the 1984 Morgan Hill Earthquake. Its construction finished in 1936. This dam is an earthfill embankment dam with foundation of dam consisted of bedrock. At time, one of few dams constructed on known fault.

Morgan Hill earthquake (Tepel, 1985)

The Morgan Hill Earthquake occurred on April 24, 1984. The earthquake occurred on the Calaveras Fault with a magnitude of 6.2. Coyote dam is located 15 miles from the epicenter and the dam is near the southern portion of the subsurface rupture zone.

The dam preformed well, given very large accelerations. No repairs needed. The SCVWD emergency response program dispatched senior inspectors immediately after the earthquake to observe the status of the dam at that time.

Cross-section of Coyote Dam

Sources:

Sherard, James L., Sc.D., Richard J. Woodward, M.S., Stanley F. Gizienski, M.S., and William A. Clevenger, B.S., Earth and Earth-Rock Dams, Engineering Problems of Design and Construction, John Wiley and Sons, Inc., 1963.

Tepel, Robert E., M. EERI, “The Morgan Hill Earthquake of April 24, 1984 – Effects on Facilities of the Santa Clara Vallet Water District,” Earthquake Spectra, Vol. 1, No. 3, May 1985, pp. 633-656.

Brina Mortensen, Coyote Dam Performance during the Morgan Hill Earthquake in 1984, Case History Report, 2.15, 2008

California Geologic Survey, Probabilistic Seismic Hazards Assessment,

http://redirect.conservation.ca.gov/cgs/rghm/pshamap/pshamap.asp

4.1.3 LA Dam

LA dam is 47m high and is founded on Saugus Formation bedrock. The dam is zoned with shell material on the upstream and downstream slopes, contains a chimney drain made of coarse materials at the center section, and has a clay zone upstream of the chimney drain. The interior slopes and perimeter road-ways of the reservoir are lined with asphalt concrete pavement. The Los Angeles Reservoir was constructed in 1977 to store treated water of the Los Angeles Aqueduct, and to replace the Lower and Upper San Fernando Dams, which were extensively damaged by the 1971 san Fernando earthquake.

During the 1994 Northridge earthquake, the dam was shaken by strong near-source ground motions, with ground motion amplitudes among the highest ever recorded. Nearby stations recorded maximum peak acceleration of 0.9 and 1 g, whereas accelerations on the right abutment and on the dam crest reached 0.43g and 0.56g, respectively.

The settlements and transverse displacements of the LA dam were obtained from the monument survey results, 1994. After the earthquake, the 7 cm thick asphalt lining that covers all upstream slopes of the LA dam displaced a lot of cracks. But these cracks were surficial, and did not extend within the embankment body.

Three slump areas were observed just west of the outlet tower. Each slump was associated with the downstream bulging of a subsided area. Small amount of fine sand were noticeable in the largest cracks surrounding these slumps.

There was no significant failure after the earthquake.

The 1994 Northridge earthquake cracked the surface pavement on the upstream slope of the Los Angeles Dam. Overall, the dam, designed to withstand severe shaking, suffered very little damage. (Courtesy of Los Angeles Department of Water and Power.)

Topographic Map of LA Dam with Cracks and Transverse movements induced by Northridge earthquake (Davis and Bardet, 1996)

Sources:

Davis, C. A., and J. P. Bardet. Performance of Two Reservoirs During the 1994 Northridge earthquake. Journal of the Geotechnical Engineering Division, Vol. 122, No. 8, 1996, pp. 613–622.

Bardet, J. P., and C. A. Davis. Performance of San Fernando Dams During 1994 Northridge Earthquake. Journal of the Geotechnical Engineering Division, Vol. 122, No. 7, 1996, pp. 554–564.

Ronnie Kamai, LA dam performance during 1994 Northridge Earthquake, Case History report, 2008

http://quake.usgs.gov/prepare/factsheets/LADamStory/

4.1.2 Austrian Dam

Basic Dam Information

Austrian Dam is a 180-foot high embankment dam which was severely damaged during the October 17, 1989 Loma Prieta Earthquake. It is located within California’s Santa Cruz mountains and situated at the convergence of the Sargent Fault located 700 feet northeast of the dam, and the San Andreas Fault 1700 feet southeast of the dam. Built in 1951, the dam has 15 feet of freeboard and impounds a 6200 acre-foot reservoir. The dam’s foundation is a thin-bedded clay shale while the abutments are comprised of a sandstone and clay shale. Both the up and downstream slopes are 2.5:1 near the crest and transition to 3.5:1 near the toes.

The dam is rolled earthfill(GC-GM) and is nearly homogeneous. An attempt was made during construction to place the more impervious materials in the upstream zone. The average percent passing the #200 sieve for up and downstream zones are 25 and 18 %, respectively. Based on isotropically consolidated undrained triaxial tests, average effective strength values of 44 deg friction and zero cohesion and total strength values of 21 deg. Friction and 290 lbs/ft2 cohesion were determined.

Extensional cracks up to 12 centimeters (4.7 inches) wide in the concrete spillway to Austrian Dam, north abutment (from U.S. Geological Survey Open-File Report 90-547)

Earthquake Damage

The epicenter of the main shock was sited 7 miles south of Austrian dam. Recorded pga is 0.64g at the Corralitos station, 5 miles east of the epicenter. The earthquake induced cracking is shown in the next page. The cracking and movement are categorized as follows:
(1) down slope movement of the right abutment causing severe damage to the spillway in the form of tension cracks along its entire length
(2) significant cracking and displacement at the embankment and spillway wall contact at the right abutment
(3) down slope movement of the left abutment near the sloping intake tower in the form of shallow surface sliding
(4) 60-foot (18.3m) wide zones of parallel cracks on both the up and downstream slopes parallel to and below the crest
(5) upthrusting at the downstream toe
(6) through going transverse cracking of the crest near the left abutment to a depth of 32 ft (9.7m)

There was significant evidence of compression and upthrusting at the downstream toe. A bridge located near the toe was moved off its foundation and displaced downstream 18 inches (0.46m).

Plan view locating cracks induced by the earthquake (from Wahler Associates, 1990)

Ariel view of Austrian Dam (Courtesy of David Gutierrez)

Lessons

Importance of soil-structure interaction and transverse cracking
The significant dam safety lesson that this case history taught is that soil-structure interaction and transverse cracking are highly probable modes of failure. It was fortuitous that the reservoir level was as low as it was at the time of the earthquake. The displacements experienced by Austrian Dam demonstrated the potential for an uncontrolled release by either, cracking at the spillway wall/embankment contact, and/or the transverse cracking. The latter was found to extent more than twice the available freeboard.

Mode of failure in homogeneous dam
Deep seated shearing where the embankment behaves as distinct blocks are governed by inertia forces and the undrained strength characteristics of the materials. Care must be taken to choose earthdam material.

Drainage function
Gravel strip drains were placed beneath the downstream pervious zone. But the gravel drains are not completely effective in relieving downstream seepage pressures.

Compaction of fill material is very important.

What could be done better

- Placing a zoned fill with chimney and blanket drains in the crest fill at both embankment ends
- Creating an impervious blanket at the upstream face
- Grouting the cracking or fissures in the spillway and grouting voids beneath the spillway slabs
- Grouting of the rock at the abutment contact with the fill


Resources:

Chris Kramer, Michael D. Lee, Preparedness for Dam Failures in the San Francisco Bay Area, Natural Hazards Review, Vol. 5, No. 1, 2004, ASCE

City of San Jose, Emergency Operations Plan, 2006

I.M. Idriss, Ralph J. Archuleta, Evaluation of Earthquake Ground Motions draft 06.5, 2007, www.ferc.gov/industries/hydropower/safety/guidelines/eng-guide/chap13-draft.pdf -

John Vrymoed, Wallace Lam, Earthquake Performance of Austrian Dam, California during the Loma Prieta Earthquake, Division of Safety of Dams, Department of Water Resources, http://damsafety.water.ca.gov/seismic_austrian.cfm

L.F. Harder, Jr., J.D. Bray, R.L. Volpe, R.L. Volpe, K.V. Rodda, Performance of Earth Dams during the Loma Prieta Earthquake, The Loma Prieta, California, Earthquake of October 17, 1989-Earth Structures and Engineering Characterization of Ground Motion, U.S. Geological Survey Professional Paper 1552-D, 1998

4.1.1 Lower San Fernando Dam

Lower San Fernando Dam is a hydraulic fill earth dam in San Fernando, California. It was constructed 1912-1917, followed by several raises to max height of 140 ft by 1930.
This case history was a milestone to renew all seismic design and evaluation process. Had the reservoir level been a little higher, or the earthquake lasted a few seconds longer, a major disaster would have occurred.

Embankment construction was:
• Founded on recent alluvium consisting of stiff clay with sand and gravel lenses.
• Hydraulic fill between upstream and downstream starter dikes.
• Rolled earth fill on top of hydraulic fill and in downstream berm.

What happened by earthquake is:
• 1971 M=6.6 San Fernando earthquake (Feb 9th, 6:00 a.m.) produced about 0.55 g peak acceleration at the dam crest.
• Dam had 35 ft of freeboard before the earthquake, and only 3 to 5 ft afterward.
• During the earthquake a major slide occurred on the upstream face, taking with it the crest and the upper 9.2m of soil on the downstream slop.
• About 80,000 persons living in the downstream valley had to be hastily evacuated.

Before and after earthquake, Lower San Fernando dam, DSOD

Lower San Fernando Dam after 1971 earthquake, DSOD

Sources:

- Seed, Lee, Idriss, & Makdisi (1975). "The slides in the San Fernando Dams during the Earthquake of February 9, 1971." J.Geotech. Engrg. Div., ASCE, 101(GT7), 651-688.
- Seed, Seed, Harder, Jong (1989). Re-Evaluation of the Lower San Fernando Dam. Contract report GL-89-1 for the US Army Corp of Engineers, Washington, DC.
- Bharat Singh and R.S. Varshney, Engineering for Embankment Dams, 1995, A.A.Balkema

4. Case Histories

The following chapter deals with a variety of case histories on dam failure (fully or partial) or earthquake resistance, mainly in California. Teton dam case appended briefly considering its disastrous damage pattern.

4.1 Earthquake induced Cases

In California, major dam safety issue is directly related with earthquake problems. The following table show valuable insight regarding earthquake induced deformation recorded in worldwide.


Earthquake induced deformation of rockfill dams (Swaisgood, 1995)

3.7 FEMA Flood Safety

The purpose of these Guidelines is to provide thorough and consistent procedures for selecting and accommodating Inflow Design Floods (IDFs). The IDF is the flood flow above which the incremental increase in water surface elevation downstream due to failure of a dam or other water retaining structure is no longer considered to present an unacceptable additional downstream threat.

These Guidelines are not intended to provide a complete manual of all procedures used for estimating inflow design floods; the selection of procedures is dependent upon available hydrologic data and individual watershed characteristics. All studies should be performed by an engineer experienced in hydrology and hydraulics, directed and reviewed by engineers experienced in dam safety, and should contain a summary of the design.

The following topics are discussed in these Guidelines: 
ü Selecting the IDF - The selection of the appropriate IDF for a dam is related to the hazard potential classification and is the result of the incremental hazard evaluation. 
ü Accommodating the IDF - Site-specific considerations are necessary to establish hydrologic flood routing criteria for each dam and reservoir. The criteria for routing the IDF or any other flood should be consistent with the reservoir regulation procedure that is to be followed in actual operation.

Sources: FEMA 94, Inflow-design-floods

3.6 FEMA Seismic Safety

These guidelines provide a basic framework for the earthquake design and evaluation of dams. The general philosophy and principles for each part of the framework are described in sufficient detail to achieve a reasonable degree of uniformity in application among the Federal agencies involved in the planning, design, construction, operation, maintenance, and regulation of dams.
The guidelines deal only with the general concepts and leave the decisions on specific criteria and procedures for accomplishing this work up to each agency. Because these guidelines generally reflect current practices, it will be necessary to make periodic revisions, additions, and deletions to incorporate state-of-the-practice earthquake engineering.

This document contains general guidelines for specifying design earthquake loadings (for design or safety evaluation) and performing seismic analyses for the design of new dams (for evaluating the safety of existing dams or modifying existing dams). The guidelines are presented in four parts:

- Selection of design or safety evaluation earthquakes
- Characterization of ground motions
- Seismic analyses of the dams and foundations
- Evaluation of structural adequacy for earthquake loading

Sources: FEMA 65 Federal Guidelines for Dam Safety - Earthquake Analyses and Design of Dams

3.5 FEMA Emergency Action Plan

There are many types of emergency events that could affect dams. Whenever people live in areas that could be flooded as a result of failure of or operation at a dam, there is a potential for loss of life and damage to property. The general purpose of these guidelines is to encourage thorough and consistent emergency action planning to help save lives and reduce property damage in areas that would be affected by dam failure or operation.

An Emergency Action Plan (EAP) is a formal document that identifies potential emergency conditions at a dam and specifies preplanned actions to be followed to minimize property damage and loss of life. The EAP specifies actions the dam owner should take to moderate or alleviate the problems at the dam. It contains procedures and information to assist the dam owner in issuing early warning and notification messages to responsible downstream emergency management authorities of the emergency situation. It also contains inundation maps to show the emergency management authorities of the critical areas for action in case of an emergency.


Sources: FEMA 64 Federal Guidelines for Dam Safety - Emergency Action Planning for Dam Owners

3.4 Federal Guideline

Federal Guidelines for Dam Safety (FEMA 93) apply to management practices for dam safety of all Federal agencies responsible for the planning, design, construction, operation, or regulation of dams. The basic principles of the guidelines apply to all dams. However, reasonable judgments need to be made in their application commensurate with each dam’s size, complexity, and hazard.

These guidelines represent the culmination of efforts, initiated by President Carter in April 1977, to review procedures and criteria used by Federal Agencies involved in the design, construction, operation, and regulation of dams and to prepare guidelines for management procedures to ensure dam safety.

The overall purpose of these guidelines is to enhance national dam safety. The immediate objective is to encourage high safety standards in the practices and procedures Federal agencies use or require of those they regulate for dam site investigation, design, construction, operation and maintenance, and emergency preparedness. As these guidelines are directly applied to make Federal dams as safe as practical, it is hoped that they will also influence state dam safety agencies and public and private dam owners to be more safety conscious where programs are now weak.

Sources: FEMA 93. Federal Guidelines for Dam Safety, 2004

3.3 California Dam Safety Program

California Dam Safety Program is bounded to the upper class Federal Dam Safety Program, which is FEMA Guidelines. The California Division of Safety of Dams conducts independent analysis during its safety review of existing and proposed dams. The extent of these analyses varies from project to project and depends upon a dam’s criticality and/or site conditions.

The techniques and basis for the Division’s independent analysis are derived from in-house analyses and studies of performance of dams and their appurtenant structures under observed and/or measured loads. Additionally, data associated with these loads as well as strength characteristics of materials are examined.

In California, dams and reservoirs are defined in the California Water Code Sections 6002, 6003, and 6004. Certain exemptions are included in Sections 6004 and 6025. This document contains Parts 1 and 2 of Division 3, Dams and Reservoirs, of the California Water Code (Statutes), Chapter 1 of Division 2, Title 23 Waters, of the California Code of Regulations (Regulations adopted by the Department of Water Resources), and an outline of Current Practices of the Department in Supervision of Dams and Reservoirs.

The complete Statutes and Regulations Pertaining to Supervision of Dams and Reservoirs can be freely downloaded at the DSOD site, http://www.damsafety.water.ca.gov/statutes_regulations.cfm.

Also, complete Listing of Dams within the Jurisdiction of the State of California in Alphabetically order by name of the Dam is shown the website below.

California Jurisdictional Dams
http://www.damsafety.water.ca.gov/damlisting.cfm


Resource: http://www.damsafety.water.ca.gov/

3.2 National Dam Safety Program

According to the Dam Safety and Security Act of 2002, the National Dam Safety Program exists to reduce the risks to life and property from dam failure in the United States through the establishment and maintenance of an effective national dam safety program to bring together the expertise and resources of the Federal and non-Federal communities in achieving national dam safety hazard reduction.

The National Dam Safety Program Act was signed into law on Oct. 12, 1996 as part of the Water Resources development Act of 1996. It was amended by the Dam Safety and Security Act of 2002 to last through 2006 (PL 107 – 310). It is administered through the Department of Homeland Security, Federal Emergency Management Agency.

In summary the program was established to improve safety and security around dams by
Providing assistance grants to state dam safety agencies to assist them in improving their regulatory programs
Funding research to enhance technical expertise as dams are built and rehabilitated
Establishing training programs for dam safety inspectors
And creating a National Inventory of Dams

Additionally, the act calls for FEMA to provide education to the public, to dam owners and others about the need for strong dam safety programs, nationally and locally, and to coordinate partnerships among all players within the dam safety community to enhance dam safety.

FEMA has been working to protect Americans from dam failure through the National Dam Safety Program (NDSP). The NDSP provides information about dam safety research and training.

FEMA dam safety guidelines
· Emergency Action Planning for Dam Owners (FEMA 64)
· Earthquake Analyses and Design of Dams (FEMA 65)
· Federal Guidelines for Dam Safety (FEMA 93)
· Selecting and Accommodating Inflow Design Floods for Dams (FEMA 94)
· Glossary of Terms (FEMA 148)
· Hazard Potential Classification System for Dams (FEMA 333)


Resource:
National Dam Safety Program PL 104-303, Amended by the Dam Safety and Security Act of 2002
ASDSO, “What is the National Dam Safety and Security Program and Why Should It Continue?”

3.1 History

3.1 History



In California, there are a lot of water resources and always exposed to a variety of hazards. The most concern in California on dam safety is huge fault and earthquake potential. Dam safety issue due to earthquake or other sources has been on the horizon since recent China earthquake. Therefore, national dam safety program and act should be firmly established always. The following table summarized the history of dam safety related events.



Major Events in Dam Safety in the U.S. (Originally by National Performance of Dams Program; http://npdp.stanford.edu, added after FEMA Guidelines)



Dates
Events

1600
Spanish colonists made diversions in New Mexico on the Rio Grande and other streams.

1634
One of the first American water power projects at Lower Falls, Neponset River, Massachusetts, was completed.

1824
U.S. Army Corps of Engineers began water project development on the Ohio and Mississippi Rivers.

1868
Compaction in earthfill construction first recommended.

1874
Failure of the Mill River Dam in Massachusetts due to uncontrolled seepage.

1889
Failure of South Fork Dam in the Allegheny Mountains in Pennsylvania due to overtopping.

1913
W. E. Fuller proposes a flood frequency formula for flood estimation.

January 27, 1916
Failure of Lower Otay Dam in San Diego, California due to flood overtopping.

June 29, 1925
Failure of Sheffield Dam in Santa Barbara, California due to seismic forces.

March 12, 1928
Failure of St. Francis Dam in Los Angeles County, California focuses public scrutiny on safety of dams in the U.S.

1933
The Procter test revolutionized the design and construction of earthfills.

1965
The Federal Power Commission issued Order No. 315 defining the responsibilities of power licensees to ensure safe construction and operation of dams.

August 8, 1972
Public attention to the hazards created by water reservoirs after the February 26, 1972 failure of a mine tailings embankment at Buffalo Creek, West Virginia led to the enactment of the National Dam Inspection Act (Public Law 92-367).

May, 1975
The Army Corps of Engineers issued a report, "National Program of Inspection of Dams" including an inventory of U.S. dams and inspection guidelines.

June 5, 1976
Failure of Teton Dam in Idaho due to internal erosion. This failure led to widespread review by federal agencies regarding dam inspection, evaluation, and modification.

April, 1977
President Carter issued a memorandum directing the review of federal dam safety activities

November 6, 1977
Failure of the Kelly Barnes Lake Dam in Toccoa, Georgia. There were 39 fatalities due to the resulting flood.

1979
Federal Guidelines for Dam Safety was published.

1982
U.S. Committee on Large Dams (USCOLD) passed a resolution urging state governments to give high priority to enacting dam safety legislation and to allocating resources to dam supervision.

1984
Morgan Hill earthquake near San Jose, California brought new attention to dam safety.

1985
National Research Council issued the report "Safety of Dams: Flood and Earthquake Criteria."

1985
The Association of State Dam Safety Officials (ASDSO) became active. The Interagency Committee on Dam Safety (ICODS) formed.

1994
National Performance of Dams Program (NPDP) officially started.

October 12, 1996
The Water Resources Development Act of 1996 (Public Law 104-303) was signed into law by President Clinton. A National Dam Safety Program was established (Section 215 of Public Law 104-303).

1998
Newly convened dam safety guidelines were completed

2002
The Act into the National Dam Safety and Security Act of 2002 was amened

2004
FEMA subcommittee updated guidelines