Posted by: Deirdre Des Jardins | March 18, 2017

Risk study: $21.8 billion in property in Oroville inundation path

Risk Management Solutions, a leading catastrophic risk modeling company headquartered in Silicon Valley, did a “what if?” modeling of a breach of the Oroville Dam. Risk Management Solutions estimated there is $21.8 billion in damageable property in the Oroville Dam inundation path. See RMS, What If The Oroville Dam Had Collapsed Completely? March 3, 2017.

Dam inundation is not covered by standard insurance policies. Only NFIP flood insurance covers flooding. But only buildings in 100 year flood plains are required to have flood insurance – and not even those buildings if they are behind FEMA certified levees. Risk Management Solutions compared the FEMA 100 year flood zones with the Oroville Dam inundation path, and found that areas with no flood insurance would include most cities: Biggs, Gridley, Live Oak, Oroville, South Oroville, Thermalito, and Yuba City.

There are similar issues with the San Luis Dam inundation path – and also billions of dollars of property at risk, with no insurance that would cover flooding from dam failure. Both Oroville Dam and San Luis Dam are known to have seismic issues – San Luis Dam has a Bureau of Reclamation initiated formal Corrective Action Study, and Oroville Dam has a mandate by the FERC five year Independent Consultant dam safety review to do a seismic re-evaluation. (See the Matt Weiser, Oroville Dam earthquake investigation may be needed, Sacramento Bee, November 29 2013.)

Failure of Oroville and San Luis Dams is not only an enormous economic risk for the Sacramento and San Joaquin Valleys, it is also an enormous risk for the California budget. Under the 1999 Paterno decision, the state of California could be liable for inverse condemnation if courts later found that the Department of Water Resource’s operations or maintenance of these large dams exposed people and property to unreasonable risk. The Paterno decision states:

“The condemnation clause of the California Constitution provides in part that ‘Private property may be taken or damaged for public use only [citation omitted] when just compensation, ascertained by a jury unless waived, has first been paid to, or into court for, the owner.’ (Cal. Const., art. I, § 19.) Where the government damages property without first paying for the right to do so, the owner may sue for inverse condemnation. [citations omitted.]”

“….the only way to determine whether a damaged private landowner has thereby been forced to contribute a compensable “disproportionate” share of the public undertaking is to determine whether the system, as designed, constructed, operated, and maintained, exposed him to an ‘unreasonable’ risk of harm, either individually or in relation to other landowners.’ ” [citations omitted.]”

It seems clear that it is in the best interests of both the public and the state of California that the seismic and structural issues with these 1960s era dams be carefully considered and adequately remediated, both in the interim and with long term solutions.

1 FEMA 100 year flood plains                                                                                       Source: RMS

2 Oroville inundation area                                                                                                  Source: RMS

Posted by: Deirdre Des Jardins | March 14, 2017

DWR’s unpublished studies of the Oroville emergency spillway

As explained below, laws governing the formal dam safety reviews by the Federal Energy Regulatory Commission required an assessment of the adequacy of Oroville Dam’s emergency spillway.   The safety reviews relied on two unpublished studies by the Department of Water Resources’ Division of Engineering.

As part of formal reviews in 2004 and 2009, DWR’s Division of Engineering performed studies of the impacts of erosion below the Oroville emergency spillway weir. The first study appears to have been only distributed internally.  A published agenda shows the second study was presented for 15 minutes to the Federal Energy Regulatory Commission’s dam safety review team, and was marked, “CEII,” or Critical Energy Infrastructure Information, as part of FERC’s standard practice. Although stakeholders could request the second study through FERC’s FOIA process, they would have had to (1) know about the second study, and (2) sign a nondisclosure agreement to get it.

The distribution of DWR’s 2004 and 2009 Oroville emergency spillway studies is reminiscent of the notice of demolishment of Arthur Dent’s house in Hitchhiker’s Guide to the Galaxy:

But the plans were on display…”

“On display? I eventually had to go down to the cellar to find them.”

“That’s the display department.”

“With a flashlight.”

“Ah, well, the lights had probably gone.”

“So had the stairs.”

“But look, you found the notice, didn’t you?”

“Yes,” said Arthur, “yes I did. It was on display in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying ‘Beware of the Leopard.”

This is apparently standard for information used in FERC’s dam safety reviews.

The Federal Energy Regulatory Commission (FERC) Dam Safety Review Process

FERC is governed by the Federal Power Act. Part 12D requires a formal review of the safety of dams every five years by a panel of independent consultants.   One of the most important aspects of the Part 12D reviews is the Potential Failure Mode Analysis, or PFMA. The FERC Dam Safety Program webpage describes a PFMA as follows:

A PFMA is an informal identification and examination of “potential” failure modes for an existing dam by a team of persons. It is based on a review of all existing data and information, first hand input from field and operational personnel, site inspection, completed engineering analyses, identification of potential failure modes, failure causes and failure development and an understanding of the consequences of failure.

Section 12.35 of the FPA, Part 12D mandates that FERC’s PFMA include a review of spillways:

(b) Evaluation of spillway adequacy. The adequacy of any spillway must be evaluated by considering hazard potential which would result from failure of the project works during flood flows.

(1) If structural failure would present a hazard to human life or cause significant property damage, the independent consultant must evaluate the ability of project works to withstand the loading or overtopping which may occur from a flood up to the probable maximum flood or the capacity of spillways to prevent the reservoir from rising to an elevation that would endanger the project works.

Oroville’s engineering design includes using the emergency spillway for the probable maximum flood. So analyzing the performance of Oroville’s emergency spillway was required under Part 12D, section 12.35.

Seventh Independent Consultant’s Safety Review in 2004

FERC’s e-library records show that in 2004, FERC oversaw the Seventh Independent Consultant’s review of the safety of Oroville and Thermalito dams. FERC records show the report of the Seventh Independent Consultant recommended that an erosion study of the hillside below Oroville emergency spillway be done, because a consultant thought that sediment could cause failure of the downstream dam. Based on this recommendation, FERC’s Division of Dam Safety & Inspections requested that DWR do an erosion study of the hillside. The Department of Water Resources formally responded in 2006:

Our Division of Engineering’s Project Geology Section has reviewed the erodibility of the emergency spillway’s downstream area. There is only one to four feet of erodible top soil in the downstream area and erosion would not compromise the stability of the emergency spillway. The amount of material eroded is dependent on the volume and duration of a spill, but material transport in the Feather River is expected. Therefore, we will re-evaluate the Thermalito Diversion Dam stability analysis to account for additional lateral earth pressures on the concrete structure due to material deposited upstream of the dam prior to the Project No. 2100 Eighth Part 12D Independent Consultant Board of Safety Review in 2008…

Original Spillway plans show no boreholes on hillside below spillway

It is unclear what geotechnical data DWR’s Division of Engineering was using to analyze the erodibility of the hillside below the emergency spillway. The original plans, published in 1974 in DWR’s Bulletin 200, Volume III, p.94, show no boreholes on the hillside below the emergency spillway weir – only under the concrete weir. It is unclear if DWR did further geotechnical investigation.

A pdf with full size graphics from Bulletin 200 is posted here: Design and General Plan of Oroville Spillway.

Eighth Independent Consultant’s Safety Review in 2009

In 2009, for FERC’s Eighth Part 12D Independent Consultants’ review, DWR chose two engineers from GEI consulting, Bill Rettberg, then Vice President of GEI, and Steven Verigin, Chief Geotechnical Engineer. A GEI document on the Oroville/Thermalito safety review states that Rettberg and Verigin worked “very closely” with DWR on “clarifying and reclassifying” some of the Potential Failure Modes (PFMs) of the dams.

The team worked very closely with DWR throughout the process, working on a shortened schedule to comply with the FERC deadline. The PFMA audit session was an intense one-day activity, that the Board and the DWR/FERC/and DSOD believed was valuable to revisiting the original PFMs and clarifying and reclassifying some of the PFMs.

The agenda for the “intense one-day” PMFA audit session shows that Tim Wehling of DWR’s Division of Engineering spent 15 minutes presenting a study of the emergency spillway to the review team.

1515-1530    Study Results; Oroville Emergency Spillway  Wehling (DOE)

The Eighth Part 12D Independent Consultants’ report is not publicly available. It is also classified “CE II” – i.e., Critical Energy Infrastructure Information.  However, subsequent FERC correspondence shows no mention of erosion of the emergency spillway as a Potential Failure Mode (PFM) for Oroville Dam or Thermalito Diversion Dam.

DWR’s Division of Safety of Dams also formally reviews the safety of Oroville and Thermalito dams at least every five years. However, in practice, DSOD’s  five year review of DWR’s dams relies on the FERC five year review. Subsequent documentation of potential failure modes of Oroville by DSOD does not show erosion of the emergency spillway as a Potential Failure Mode.

Oroville’s spillway failure appears, in hindsight, to have relied on inadequate analysis of the emergency spillway as a Potential Failure Mode.  This raises real questions about DWR’s 2004 and 2009 engineering analyses.   It is currently unclear if these analyses will ever be publicly released by DWR.

This post was updated on March 16, 2017 to correct the definition of CEII classification and provide a link.

 

Posted by: Deirdre Des Jardins | March 12, 2017

Full San Luis Dam endangers over 200,000 people

San Luis Dam, also known as B.F. Sisk Dam, is 382 feet tall and 18,600 feet long, and impounds up to 2 million acre-feet of water. It is the largest offstream dam in the United States.  Pursuant to the 1960 San Luis Act, San Luis Dam was constructed by the Bureau of Reclamation, and is still owned by the Bureau. The Bureau of Reclamation and the California Department of Water Resources entered into a Joint Use Agreement for San Luis in December 1961, which provides that the State of California operates and maintains the San Luis facilities. Because the dam is owned by the Bureau of Reclamation, it is not subject to oversight by DWR’s Division of Safety of Dams, or the Federal Energy Regulatory Commission’s Division of Dam Safety and Inspections.

031217_2104_FullSanLuis1.jpg

1 San Luis Dam and Reservoir                                                                         Source: Bureau of Reclamation

San Luis Dam is in a very seismically active area, and parts of the Ortigalita fault run through the reservoir. In the 2000’s, it was recognized that the Ortigalita fault could generate an earthquake of magnitude 7.1. The dam is also only 28 miles from the San Andreas Fault, and 23 miles from the Calaveras-Hayward Fault.

San Luis seismic sources

2 Faults near San Luis Dam Source: California Department of Conservation, 2012

It has been known since a large slide in 1981 that the earthen dam has serious structural and seismic deficiencies. The dam is currently the subject of a formal Bureau of Reclamation Corrective Action Study, begun in 2007. San Luis Dam is known to need an operating restriction of at least 50 feet to be within Reclamation’s Dam Safety Public Protection Guidelines. However, because the dam is operated by the California Department of Water Resources, there appears to have been no formal consideration of an interim operating restriction to protect lives and property.

1981 Embankment Slide

In September 1981, a 1,100 foot section of the upstream San Luis Dam embankment near the crest of the dam — 400,000 cubic yards — slid 177 feet. It was a deep seated failure which extended through the fill and into the native soil under the dam.

3 September 1981, San Luis Dam Embankment slide                                                           Source: J. Michael Duncan

1999 engineering analysis by the nationally recognized civil engineer  J. Michael Duncan showed that the factor of safety for the dam had been reduced from 4.0 to 1.21 – too low to be safe in an earthquake. The table below is from Duncan’s analysis.

4 Safety factors after repair                Source: Duncan, The use of back analysis to reduce slope failure risk (1999)

Known Seismic Hazards

Beginning in 1982, geologist Larry Anderson at the Bureau of Reclamation conducted a series of seismic studies which showed that the Ortigalita fault has higher rates of activity than had been previously recognized. The independently reviewed studies also showed that a large earthquake could lead to crest settlement and overtopping of the dam, which would result in large uncontrolled releases and likely dam failure. The Mid-Pacific Regional Office of the Bureau initiated a formal Corrective Action Study in 2007. In the letter to CVP contractors, the Mid-Pacific Regional Office stated:

Through the Dam Safety Program, Reclamation has identified several conditions at B.F. Sisk Dam that require action to reduce risks.

• The dam is located in a seismically active area, very close to the Ortigalita Fault

• Studies and deformation analyses conducted during 2005 indicate that, during a major earthquake, crest settlement greater than freeboard, or cracking associated with embankment deformation, could occur and lead to dam failure

• Failure of the dam could inundate hundreds of square miles including the town of Santa Nella, about 7 miles of Interstate 5, and numerous farms and houses along the San Joaquin River including some areas of Stockton

• An independent consultant review board agreed with Reclamation that the calculated crest settlement is possible for the estimated peak ground accelerations associated with the Ortigalita Fault

Under the current schedule, the Mid-Pacific Regional Office’s Corrective Action Study is not expected to be completed until May of this year. Construction on the proposed corrective action is not expected to begin until at least 2020, and funding has not yet been identified. The Mid-Pacific Regional Office published a draft appraisal for the San Luis Dam Corrective Action in 2013. The study indicated that a reservoir restriction of at least 50 feet is required to bring the seismic risk to within current Reclamation Public Protection Guidelines:

Since B.F. Sisk is an off-stream storage facility, a reservoir restriction is feasibly obtained by not filling (pumping into) the reservoir. This measure would consist only of a change in operations, so it is considered non-structural.

Based on current seismic deformation estimates (Reclamation 2013b) it appears that a permanent restriction of at least 50 feet would be required to reduce the risk to within current Reclamation Public Protection Guidelines. (emphasis added, p. 27)

However, Mid-Pacific Regional Office documents show no consideration of interim operating restriction on the dam, although such a restriction would normally have been considered under the Bureau’s 2011 Interim Dam Safety Public Protection Guidelines. The diagram of first priority risk reduction actions, from p. 30 of the 2011 Public Protection Guidelines, is shown below. The first priority actions clearly include taking interim steps for risk reduction.

Dam safety risk management actions             Source: Reclamation Public Protection Guidelines

Because of California’s torrential rains this winter, San Luis reservoir filled. Failure to formally consider and implement an operating restriction has resulted in catastrophic risks, both to lives and to California’s water supply. If an earthquake were to occur, the earthen dam could slump and be overtopped. Failure of the dam would create an enormous path destruction, almost 10 miles wide and over 80 miles long, from Los Banos to Antioch in the western Delta. The inundation would immediately hit Santa Nella (population 1,400) and Los Banos (population 37,000). It would flow through western Merced and Stanislaus counties, impacting West Modesto (population 5,600.) In San Joaquin County, the inundation would impact the western part of Manteca (population 72,000), the western part of Stockton (population 298,000.) In Contra Costa County, the inundation would impact Discovery Bay (population 14,000), and Brentwood (population 55,000.) In 2003, the San Joaquin County Office of Emergency Services estimated that 165,000 people were in the inundation path.


6San Luis Dam Inundation Map                                                                               Source: City of Ripon

The dam inundation path also includes Clifton Court Forebay and the State Water Project and Central Valley Project Banks and Jones pumping plants. Potential impacts on Clifton Court Forebay and the SWP and CVP facilities is unknown. However, failure of San Luis dam would have catastrophic impacts on State Water Project and Central Valley Project water supplies.

7 State Water Project Banks Pumping Plant                                          Source: The California Spigot

Although an operating restriction on San Luis reservoir would have a significant impact on State Water Project and Central Valley Project water supplies, most of the largest SWP and CVP contractors do have other storage available that does not have catastrophic risks to lives, property, and infrastructure. Metropolitan Water District has Diamond Valley Reservoir, with a capacity of 800,000 acre feet, as well as groundwater storage in the Semitropic groundwater bank.  Santa Clara Valley Water District also has groundwater storage in Semitropic. Kern County Water Agency has groundwater storage available in the Kern Water Bank and other groundwater banks.


Posted by: Deirdre Des Jardins | March 1, 2017

Brown administration cancels state Senate hearings on Oroville, WaterFix

The Brown administration has requested the cancellation of two hearings by the state Senate since the Oroville spillway crisis began.  The Senate Natural Resources and Water Committee scheduled a  joint hearing with the  Joint Legislative Committee on Emergency Management on “The Incident at Oroville Dam: What Happened and What Happens Next”  on February 28, 2017.   It was cancelled at the request of the administration.    The Natural Resources and Water Committee had previously cancelled a February 14, 2017 informational hearing on the California WaterFix at the request of the administration.

The Senate Natural Resources Committee website states that the hearings will be rescheduled.

Posted by: Deirdre Des Jardins | February 27, 2017

Urban Delta – 264,000 people at risk from flooding in Stockton area

The largest cities in San Joaquin County are on the eastern edge of the Sacramento-San Joaquin Delta, and include Stockton (population 292,000), Lathrop (population 18,000), and Manteca (population 72,000.) The Stockton metropolitan area is protected by a system of levees that was built between the gold rush and the 1920s.  Parts of the system were improved by the Army Corps of Engineers after the Flood Control Act of 1944.   After Hurricane Katrina, the San Joaquin Area Flood Control Agency worked with the Army Corps of Engineers to create a plan for upgrading the levees to 200 year levels of protection.  The Corps released the Draft Lower San Joaquin Interim Feasibility Study and Environmental Impact Statement / Environmental Impact Report in February 2015. The final feasibility study for the $803.7 million plan has yet to be completed.

In the interim feasibility study, the Army Corps of Engineers noted that 264,000 people live in floodplains in the Stockton metropolitan area, with $21 billion in damageable property and 23 critical structures:

The existing levee system within the study area protects over 71,000 acres of mixed-use land with a current population estimated at 264,000 residents and an estimated $21 billion in damageable property. In addition to the residents and property, the levee system protects approximately 23 structures considered to be critical infrastructure (hospitals, police and fire stations, etc.) as well as the Interstate 5 and State Highway 99 corridors.

and concluded that “[t]here is significant risk to public health, safety, and property in the project area associated with flooding” (p. 90, emphasis added.)

1Lower San Joaquin plan area levees         Source: Army Corps of Engineers feasibility study, p. 89

Seepage endangers levees

The Army Corps also explained in the feasibility study that the lower San Joaquin levees have problems with seepage, and are at risk of breaching at river stages below flood:

The potential for seepage problems to occur along the existing levees in the project area is created by discontinuous layers of coarse‐grained pervious soils (i.e., sands and gravels)… During high‐water events, water from the river can enter the pervious soil layers and then move laterally through these layers under/through the levee. Excessive seepage can erode soil within the levee and lead to a rapid collapse and subsequent breach… The risk of levee failure is not due to design deficiency or to lack of O&M of the existing levees, but to a better understanding of the mechanics of under‐seepage in the Central Valley. The project levees within the study area do not meet current USACE levee design criteria and are at risk of breach failure at stages considerably less than levee crest elevations. This is evidenced by historical levee boils and heavy seepage at river stages less than design flows.  (p. 90, emphasis added)

Because of these problems, the Army Corps estimated that the “risk and uncertainty” of levee failure was 2% a year for many levees on the lower San Joaquin.  The map below shows the levees that are at risk of failing, and the depth of flooding in a 500 year flood.   While it is extremely unlikely that all the levees would fail simultaneously, the ACE estimated that they are all at risk of failing during high flows and need remediation.

2 500 year flood depths                   Source: Army Corps of Engineers EIS/EIR, p. 86

High water perils

During the high-water periods in January and February of 2017, locals have been patrolling the Stockton metropolitan area and Delta levees, looking for signs of levee seepage or boils. Flooding southwest of Manteca was narrowly averted when a firefighter from the Lathrop-Manteca Fire District spotted a sinkhole as it was occurring.   While these efforts to protect the levees have been heroic, the stressed levees could easily fail in a flood.   Below is a picture of flooding of Stockton in 1955, from the Army Corps, giving an idea of the amount of flooding that would be experienced with major levee breaches.

3 Stockton flooding, 1955                                         Source: Army Corps of Engineers

State funding problems

The federal Water Infrastructure Improvements for the Nation Act (WIIN), passed on December 11, 2016, mandated that the Secretary of the Army expedite and give priority funding for the final Lower San Joaquin feasibility study, and authorized proceeding to planning, engineering, and design once the final feasibility study is completed.

However, there is no similar mandate at the state level for priority funding for completion of the Lower San Joaquin plan.  Proposition 1E accounting shows that line items for Lower San Joaquin planning totaled only $3.8 million in bond funds.    This was slightly more than 1/10th of 1% of the total of $2.895 billion authorized in Prop 1E for improving state plan of flood control facilities, increasing levels of flood protection in urban areas, and reducing risk of failure of Delta levees.   Almost all of the $2.895 billion in Prop 1E flood control funds has been obligated, and there is only $24.6 million in remaining unallocated funds.

Part of the funding issue was that the levees in North Stockton, which are most at risk of failing, were not part of the State Plan of Flood Control when Prop 1E was passed.   Although Prop 1E allowed the non-SPFC levees to be upgraded and added to the State Plan of Flood Control, the 2012 Central Valley Flood Protection Plan committed only to evaluating whether there was a “state interest” in upgrading the levees.   The following is from p. 51 of the 2012 Central Valley Flood Protection Plan:

Stockton Metropolitan Area – Improvements for this area include the following:

»» Improve SPFC levees along the San Joaquin River and tributary channels.

»» Evaluate the potential benefits of and State interest in local floodgates and control structures, as they relate to facilities of the SPFC in and around Stockton, and contribute to achieving an urban level of flood protection.

The Draft 2017 Central Valley Flood Protection Plan now includes upgrading both SPFC and “appurtenant” non-SPFC levees in the Stockton  area in the “urban portfolio” of projects. However, funding for the $803 million project will need to come from other bonds. Governor Brown has proposed to allocate $65 million in Proposition 1 funds for flood control in urban areas in the Delta, but that is the entire amount allocated in Prop 1 for urban flood control, and is likely also needed for emergency repairs.

This post was updated on March 1 at 5:00 pm.

Posted by: Deirdre Des Jardins | February 17, 2017

Repair of Oroville dam’s main spillway in 2009 – 7,000 square feet

Damaged Dam Safety

Part of DWR’s 7,000 square foot spillway repair    October 7, 2009

Kevin Dossey, the Senior Civil Engineer for the Department of Water Resources, Oroville Field Division, indicated in a press conference on Friday, February 10, that Oroville’s main spillway has never had a major repair.

But a May 2009 letter from DWR Deputy Director Raphael Torres to the Federal Energy Regulatory Commission (FERC) shows that DWR needed to repair 7,000 square feet of the main spillway, including large cracks on the spillway surface. Torres stated:

In April 2008, personnel from DWR’s Division of Operations and Maintenance inspected Oroville Dam’s spillway invert and walls for concrete deficiencies. While the overall condition of the spillway is good, the detailed visual and sounding inspection found areas of concrete spalling and delamination. DWR’s Division of Engineering is preparing a construction contract for maintenance repairs that will cover approximately 7,000 square feet of the spillway. The scope of the maintenance repair may include cutting, removing and replacing damaged concrete, sand blasting exposed steel rebar, injecting non-shrink grout into voids, repairing or replacing joint seals as necessary, and placing epoxy adhesive to repair large cracks on the spillway surface. To meet the California Environmental Quality Act requirements a Notice of Exemption will be filed. We anticipate work will begin in August, and should be complete by November 1, 2009. (underlining added.)

According to the U.S. Bureau of Reclamation’s Guide to Concrete Repair, epoxy resins are brittle and don’t withstand movement:

It is often very difficult to attain successful repair of cracks … It is better to leave most types of concrete cracking unrepaired than to perform inadequate or improper repairs (figures 71 and 72). The selection of methods for repairing cracked concrete depends on the cause of the cracking. If improper methods are used, cracks will usually reoccur in the repair material or adjacent concrete, and it may make the initial damage worse.

For some cracks, epoxy or polyurethane resin injection (section 38) can be used…. Epoxy resin injection can sometimes be used to seal low volume water leakage, while structurally rebonding cracked concrete members. Epoxy resins cure to form hard, brittle materials that will not withstand movement of the injected cracks.

It is currently unknown if more recent repairs to the main spillway also used epoxy resins for repair of cracks.   If the crack repairs failed during high flows, it could have caused the large hole in the spillway.   According to a U.S. Bureau of Reclamation document on Dam Safety, “Cavitation Induced Damage of Spillways,” opening of cracks or joints in concrete spillways can exacerbate cavitation, potentially causing spillway failure.

Paul Rogers and Matthias Gafney also reported in the Mercury News that cavitation was a possible failure mode in  Oroville Dam: What Made the Spillway Collapse?    The article quoted  Paul Tullis, a professor emeritus of civil engineering at Utah State University, as saying,  “It’s like a big grinder. It causes concrete to be torn apart.”

nwswarningThe California Department of Water Resources (DWR) has issued an evacuation order downstream of Oroville dam. According to an alert by KRCTV.com,

A hazardous situation has developed with the Oroville Dam auxiliary spillway. Officials say that operation of the auxiliary spillway has lead to severe erosion that could lead to a fa

Failure of the auxiliary spillway structure will result in an uncontrolled release of flood waters from Lake Oroville.

In response to this developing situation, DWR is increasing water releases to 100,000 cubic feet per second. Immediate evacuation from the low levels of Oroville and areas downstream has been ordered.

The Department of Water Resources is now anticipating failure of the auxiliary spillway within the hour.

This is a tragic development, even more so because the possibility of failure of the Oroville auxiliary spillway due to severe erosion was raised repeatedly by environmental groups and local agencies during relicensing of Oroville Dam by the Federal Energy Regulatory Commission.

California Water Research examined a 2005 legal filing in the FERC relicensing by Friends of the River and Sierra Club California which clearly described the risks of the unarmored spillway:

A single operational use or multiple operational uses (with failure to repair any preceding or cumulative damage) of the ungated spillway could result in a loss of crest control of Oroville Dam. A loss of crest control could not only cause additional damage to project lands and facilities but also cause damages and threaten lives in the protected floodplain downstream. An unarmored spillway is not in conformance with current FERC engineering regulations. (emphasis added.)

In response, the Department of Water Resources reportedly denied there was a risk of loss of crest control if the auxiliary spillway was used, but did not provide any geotechnical information for the environmental groups to examine.  The Department of Water Resources also argued that a feasibility study of armoring the auxiliary spillway with concrete should be financed as a flood control project by the US Army Corps of Engineers.  DWR never requested a feasibility study by the Corps for armoring the spillway. The armoring project was also likely ineligible for funding as an Army Corps of Engineers flood control project because DWR has the obligation of controlling releases from the dam.




Posted by: Deirdre Des Jardins | February 10, 2017

Oroville’s auxiliary spillway – crisis engineering

As of Saturday, February 11 2017, the crisis with the damaged main spillway at Oroville is continuing to unfold. The reservoir  began to spill over the 1,703 foot auxiliary spillway lip this morning, and as of 2:00 pm, the California Data Exchange Center elevation sensor shows 0.9 feet of flow over the spillway lip.

Engineers for the Department of Water Resources made a heroic, last-ditch effort to armor the auxiliary spillway.   According to a post by Capitol Public Radio:

Cement trucks have been pouring concrete at the mouth of the emergency spillway since Thursday. It had previously been a simple dirt channel.

The problem is that even rapid hardening cement takes at least two days to cure.   So if the emergency spillway has to be used on Saturday, the concrete and rock band-aid could just wash down into the Feather River.   This is desperation.

Emergency work at base of Oroville auxiliary spillway

The Department of Water Resources has long been informed of this worst-case flood scenario. The issues of the unarmored auxiliary spillway were discussed regularly with the Department of Water Resources during relicensing of Oroville by the Federal Energy Regulatory Commission (FERC), but after several years it became apparent that no action was going to be taken.   Environmental and local groups, including Sutter County, intervened in the FERC relicensing, in part to force DWR to do a study of the adequacy and integrity of the auxiliary spillway and remedy any deficiencies.

The 2007 Environmental Impact Statement for the Oroville FERC relicensing (FERC Project 2100) states:

Sutter County also requests that the Commission issue several relicensing orders, including …(2) direct the licensee to investigate the adequacy and structural integrity of Oroville dam’s ungated auxiliary spillway that may currently pose a risk to the project facilities and downstream levees in Sutter County and take all necessary actions to correct identified deficiencies; and (3) direct the licensee to investigate the levees on the Feather River, in the context of its hydroelectric, water supply and flood control operations and to repair, replace, and maintain those levees to provide appropriate levels of flood protection in light of license operations. (C-21)

The Federal Energy Regulatory Commission declined to even require a study of the adequacy of the unarmored auxiliary spillway, although it is part of the dam’s maximum rated discharge of 250,000 cfs in a maximum flood event.

Post updated on February 11, 2017.

Posted by: Deirdre Des Jardins | February 9, 2017

YCWA concerns about Oroville’s auxiliary spillway

Oroville dam is the tallest dam in the United States, but it has an auxiliary spillway that consists only of a 1,730 foot long spillway lip, that spills directly onto bare hillside.  Yuba County Water Agency (YCWA) raised concerns in 2002 about the damages that could occur from using the auxiliary spillway:

The discharge area below the emergency spillway is not armored and extensive erosion would take place if the emergency spillway were used.  The spillway road and possibly high voltage transmission towers would be impacted. (p. II-1)  Because the area downstream from the emergency spillway crest is an unlined hillside, significant erosion of the hillside would occur. (p. II-5) “The hillside between the emergency spillway and the Feather River would be subject to severe erosion when water flows over the spillway. Depending on the rate of flow, the erodable area . . . could range from 50 to 70 acres. The amount of soil, rock, and debris that would fall into the Feather River could be very large, depending on the depth of erosion. There could be damages to downstream structures, including the Thermalito Diversion Dam and Powerplant, Fish Barrier Dam, and highway bridges. If there is river channel blockage below the spillway, there could be impacts on operation of Hyatt Powerplant. (p. IV-3)

Yuba County Water Agency, Technical Memorandum on Lake Oroville Surcharge, August 2002

These concerns were raised with the California Department of Water Resources almost 15 years ago, during relicensing of Oroville dam by the Federal Energy Regulatory Commission (FERC.)

oroville-spillway

Flow down auxiliary spillway Feb 11, 2017

One of the major impacts of climate change will be on water resources. Many scientists believe that the recent, unprecedented droughts in California and other western states could be the beginning of a permanent transition to a drier climate in the region.

In California, many climate change models project significant drying in the Sacramento and San Joaquin River basins in coming decades. A 2012 study by Randy Hanson and Lorraine and Alan Flint et. al. at the USGS California Water Science Center has one of the clearest illustrations of how much drier these basins could get by the end of the century. The map below shows the projected change in discharge (outflow) from the watersheds.  The map on the far right is color coded by the reduction in discharge between 2010-2020 and the end of the century.   The orange areas show a reduction of 45% or more.

Hanson2012watershed

 

The study used NOAA’s Global Fluid Dynamics Lab climate model, which is a higher sensitivity climate model, projecting more warming for a given level of C02 in the atmosphere.   The higher sensitivity climate models are consistent with recent increases in global temperature, and generally project more drying.    The study also used the A2 (medium-high) greenhouse gas emissions scenario, which assumes that C02 in the atmosphere continues to increase.

Under the A2 scenario, the GFDL model runs projected that median flows in the entire Sacramento River watershed could decrease by 17% by 2020, and by 34% by 2100. The box and whisker plot below shows the range of projections for the change in median flows for each 20 year period, when compared with 1963-2000.    While there is a fair amount of spread in the projections, the overall trend is strongly down.    This is shown by the dashed line, which gives the mean change over all model projections for each 20 year period.  The change is not uniform, probably because the GFDL climate model captures cycles in sea surface temperatures, including the  Pacific Decadal oscillation.

Hanson2012SacRunoff

 

       Hanson2012SacRunofflabel

 

Not all global climate change models predict as much drying in the Sacramento River basin as the GFDL model used in Hanson’s study, but the ones that do are consistent not only with recent increases in global temperature, but also with the severe droughts in California, Texas, and New Mexico.   A 2009 study by Jessica Oster and Isabel Montanez et. al. at UC Davis may also corroborate the climate change models that project significant drying.   Oster analyzed the composition of layers in stalagmites in Moaning Cavern in the central Sierra Nevada.   The changes in isotopes showed that the last time the climate warmed significantly, at the end of the last ice age, it got much drier.

California is entering a new era of water management, with much greater risk and uncertainty due to climate change. Making conservation a way of life is essential to managing that risk.  For this reason, Governor Brown’s mandate to increase long term conservation targets above the 20×2020 levels is critically important for California’s cities.

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