Preliminary Root Causes Analysis of Failures of the Oroville Dam Gated Spillway R. G. Bea Center for Catastrophic Risk Management University of California Berkeley April 17, 2017 This Preliminary Root Cause Analysis of the failures of the Oroville Dam gated spillways is based on current publically available photographic and written documentation included and cited at the end of this document. Design Defects and Flaws The origins of the gated spillway failures are deeply rooted in pervasive design defects and flaws developed by the California Department of Water Resources (DWR). These design defects and flaws included the following: 1. Spillway base slabs of insufficient thickness for the design hydraulic conditions: 4 to 6 inches thick at minimum points; 2. Spillway base slabs not joined with 'continuous' steel reinforcement to prevent lateral and vertical separations; 3. Spillway base slabs designed without effective water stop barriers embedded in both sides of joints to prevent water intrusion under the base slabs; 4. Spillway base slabs not designed with two layers of continuous steel reinforcement (top and bottom) to provide sufficient flexural strength required for operating conditions; and 5. Spillway base slabs designed with ineffective ‘ground’ anchors to prevent significant lateral and vertical movements. Construction Defects and Flaws The design defects and flaws were propagated by DWR during construction of the spillway. These construction defects and flaws included the following: 1. Failure to excavate the native soils and incompetent rock overlying the competent rock foundation assumed as a basic condition during the spillway design phase, and fill the voids with concrete, and 2. Failure to prevent spreading gravel used as part of the under-slab drainage systems and ‘native’ soils to form extensive 'blankets' of permeable materials in which water could collect and erode. Maintenance Defects and Flaws The design and construction defects and flaws were propagated by DWR during maintenance of the spillway. These maintenance defects and flaws included the following:   1   1. Repeated ineffective repairs made to cracks and joint displacements to prevent water stagnation and cavitation pressure intrusion under the base slabs with subsequent erosion of the spillway subgrade; and 2. Allowing large trees to grow adjacent to the spillway walls whose roots could intrude below the base slabs and into the subgrade drainage pipes resulting in reduced flow and plugging of the drainage pipes. February 2017 spillway releases By the time of the February 2017 spillway releases, the gated spillway had become heavily undermined and the subgrade eroded by previous flood releases. The first spillway release completed the undermining of the spillway slabs, allowing water cavitation and stagnation pressures to lift the ‘weak’ slabs and break them into pieces (U.S. Department of the Interior Bureau of Land Management and U.S. Army Corps of Engineers, 2015; United States Department of the Interior Bureau of Reclamation, 2007). After the almost catastrophic water release over the un-surfaced Auxiliary Spillway, the subsequent water releases down the gated spillway propagated the initial spillway breach until spillway releases ceased. Root Causes Analysis Currently available information indicates the Root Causes of the gated spillway failures are founded primarily in 'Extrinsic' uncertainties (human and organizational task performance and knowledge development and utilization) developed and propagated by DWR during the gated spillway design, construction, and maintenance activities (Bea, 2016). A key question that can not be answered at this time is: “why did DWR and the responsible State and Federal regulatory agencies (California Water Commission, Federal Energy Regulatory Commission) allow these Root Causes to develop and persist during the almost 50 year life of the gated spillway?” One answer that has been offered is that the spillway was designed and constructed according to the ‘Standards of the time.” While that answer may or may not be factual or true, current evidence indicates the original spillway design and construction does not meet current guidelines and standards. Another answer that has been offered is that the spillway operated for almost 50 years and was subjected to water discharges that exceeded those developed during 2017 without failure. Recent inspections indicated that the spillway was in ‘satisfactory condition.’ The conclusion prior to the February 2017 discharges was the gated spillway consequently was ‘suitable for service.’ The experience prior to the DWR attempt on February 11 to use the Emergency Spillway indicated that conclusion was not valid. The gated spillway failed during discharges that were much less than the design conditions. The author’s previous experiences with investigations of failures of public infrastructure systems (e.g. New Orleans hurricane flood protection system during Hurricanes Katrina and Rita) leads   2   to a conclusion that it is likely that the wrong standards and guidelines are being used to requalify many critical infrastructure systems for continued service. The majority of these standards and guidelines were originally intended for design, not re-qualification or reassessment of existing aged infrastructure systems that have experienced ‘aging,’ ‘technological obsolesce,’ and increased risk (likelihoods and consequences of major failures) effects. Inappropriate standards and guidelines are being used to re-qualify these infrastructure systems for continued service. The currently available information indicates this is one of the primary Root Causes of the failures of the Orville Dam gated spillway. References Bea, R. G. (2016): “What Is Safe?”, MOJ Civil Engineering, Med Crave, September (http://medcraveonline.com/MOJCE/MOJCE-01-00002.php). Department of Water Resources (1974): California State Water Project, Volume III, Storage Facilities, Bulletin Number 200, (https://archive.org/details/zh9californiastatew2003calirich). Department of Water Resources (1965): Oroville Dam Spillway Chute Plan, Profile and Typical Sections, February. Department of Water Resources (1965): Oroville Dam Spillway Terminal Structure, Concrete and Details, February. Department of Water Resources, Division of Safety of Dams (2008): Inspection of Dam and Reservoir in Certified Status, January. Department of Water Resources, Division of Safety of Dams (2008): Inspection of Dam and Reservoir in Certified Status, May. Department of Water Resources, Division of Safety of Dams (2009): Inspection of Dam and Reservoir in Certified Status, June. Department of Water Resources, Division of Safety of Dams (2010): Inspection of Dam and Reservoir in Certified Status, June. Department of Water Resources, Division of Safety of Dams (2011): Inspection of Dam and Reservoir in Certified Status, February. Department of Water Resources, Division of Safety of Dams (2011): Inspection of Dam and Reservoir in Certified Status, October. Department of Water Resources, Division of Safety of Dams (2013): Inspection of Dam and Reservoir in Certified Status, February. Department of Water Resources, Division of Safety of Dams (2013): Inspection of Dam and Reservoir in Certified Status, September.   3   Department of Water Resources, Division of Safety of Dams (2014): Inspection of Dam and Reservoir in Certified Status, April. Department of Water Resources, Division of Safety of Dams (2014): Inspection of Dam and Reservoir in Certified Status, September. Department of Water Resources, Division of Safety of Dams (2015): Inspection of Dam and Reservoir in Certified Status, March. Department of Water Resources, Division of Safety of Dams (2015): Inspection of Dam and Reservoir in Certified Status, August. Department of Water Resources, Division of Safety of Dams (2016): Inspection of Dam and Reservoir in Certified Status, September. U.S. Department of the Interior Bureau of Reclamation (1965): Hydraulic Model Studies of the Flood Control Outlet and Spillway for Oroville Dam, California Department of Water Resources, State of California, Report No. Hyd-510, (https://www.usbr.gov/tsc/techreferences/hydraulics_lab/pubs/HYD/HYD-510.pdf). U.S. Department of the Interior Bureau of Reclamation (2014): Appurtenant Structures for Dams (Spillways and Outlet Works Design Standards), Design Standards No. 14, August. U.S. Department of the Interior Bureau of Reclamation (2007): Uplift and Crack Flow Resulting from High Velocity Discharges Over Open Offset Joints, Report DSO-07-07, December. U.S. Department of the Interior Bureau of Reclamation and U.S. Army Corps of Engineers (2015): Best Practices in Dam and Levee Safety Risk Analysis, VI-1 Stagnation Pressure Failure of Spillway Chutes, VI-3 Cavitation Damaged Induced Failure of Spillways, July.   4   Spillway Discharges FS 135,000 130,000 125,000 120,000 - 115,000 - 110,000 105,000 100,000 95,000 - 90,000 - 85,000 90,000 - 75,000 70,000 65,000 60,000 . 55,000 - 50,000 45,000 - 40,000 - 35.000 30,000 25,000 20,000 15,000 - 10,000 - 5,000 - 0 . -5,000 -10,000 OROVILLE DAM 0R0 Date nom 01/01/1984 ""0th 03/01/2017 07:18 Dulauon: 12113 days Max of period (01/02/1997 00 00, 129256 0) Min of period 00/30/1988 00 00, -7270 0) 1293,56 0 0 0 ouomo 00 01/01/95 00 01/01/00 oo oo ream/our. OUTFLOW - CFS 01/01/10 00 01/01/15 00 Lake Oroville Storage Levels 3,750,000? 3,500,000 4 Total Reservoir Capacity: 3,537,57 AF 3,250,000 1 3,000,000 1 2,750,0001r'" 2,810,363.55 AF 2,500,000 2,250,0004 2,000,000- 1,750,000 .- - 1,500,000 - Lake OrovilleResewoir Level (AF) 1,250,000 - 1,000,000 - 750,000 - 500,000 - 250,000 . Oct Water Year (October 1 - September 30) Historical Average ?Total Reservoir Capacity 1976-1977 (dry) 1982-1983 (wet) ?2016-2017(current) 1977?1978 Lake Oroville Spillway Incident: Timeline of Major Events February 4-25 Oroville Spillway public Info Line: (530) 538-7826 0 February 7: As water releases from the ?ood control spillway ramp up to 54,500 cubic feet per second (cfs), in anticipation of in?ows expected from rainfall, DWR employees notice an unusual ?ow pattern. Spillway ?ows stop for investigation. Engineers ?nd large area of concrete erosion. 9 February 8: DWR begins ongoing consultation with FERC and other dam safety agencies. DWR runs test ?ows down the damaged spillway, monitoring further erosion, and prepares for possible use of emergency spillway.21./7 emergency interagency operations centers activate to study and implement response to ?ood control spillway and related structures, with careful study of weather forecasts. 9 February 11: In?ow to Lake Oroville brings lake level above 901 feet. This engages the emergency spillway for the ?rst time in the history ofthe facility. 0 February 12: Anticipated erosion begins to progress faster than expected at the base of the emergency spillway. The Butte County Sheriff?s Of?ce issues mandatory evacuation orders for the Oroville area. To ease pressure on the emergency spillway, the ?ood control spillway out?ow is increased to 100,000 cfs. After several hours, in?ows decrease and over?ow stops at the emergency spillway. Erosion to the emergency spillway hillside is assessed. 6 February 13: DWR crews begin working around the clock to repair the emergency spillway. Evacuation orders remain in effect. 9 February 14: As the lake level continues to drop, the mandatory evacuation order is modi?ed to an evacuation warning. Crews continue working around the clock to repair the emergency spillway. An elevation of 850' is targeted for lake level. 0 February 16: Flood control spillway ?ows are reduced below 100,000 to facilitate the clearing of debris from below the spillway. Lake levels continue to drop. Construction to armor the emergency spillway continues. 0 February 18: Lake level down to 854 feet. Flood control spillway ?ows are reduced to 55,000 cfs. Barge construction begins in order to remove debris from the diversion pool beneath the spillway. 9 February 20: Lake Oroville elevation reaches 848.95 feet at 11 am. Repairs and preparations continue around the clock. Cooperating Agencies: California Department of Water Resources, Butte County Sheriff, CAL FIRE, Oroville Police Department, Butte County OES, Oroville Fire Department, Butte County Public Works, Oroville Hospital, Caltrans, California Highway Patrol, California State Parks, California Conservation Corps, California National Guard, California Department of Fish and Wildlife, Red Cross, Bureau of Indian Affairs, CAL OES, USACE, FERC, FEMA For more imagery, see DWR Pixel Library February Cubic feet per second (cfs) 0 . In?ows to Lake Oroville reach 180,000 Between 1 190,435 cfs, significantly February 6-10, 4 6 higher than forecasted 12.8 inches of rain 160 000 . fall in the Feather Mandatory Flood_ Control River Basin evacuation Spillway order is outflows raised issued to 100,000 to 140 0 ,0 ease pressure 0 on Emergency Spillway 0 120,0 0 100,0 )0 Flood Control Spillway 80 000 inspection 0 OUTFLOWS Wm .. 0 Lake level, in feet 9 02/12/2017: 03:00 am 902.59' 900 880 860 850' elevation - 840 watercagov cdec.water.ca.gov/ February Source: DEC January  27,  2017             Large  trees  growing   adjacent  to  spillway   wall  –  roots  able  to   penetrate  drains     1   February  7,  2017  –  Stage  #1           Plume  of  ‘dirty’   water  –  eroded   sediments  from   under  spillway     2           Exposed  rock  and   erodible  sediments   under  spillway       3                     Wall  drains   emptying  water   collected  from   under  spillway   Wall  drains  on   upper  part  of   spillway  indicate  A   Lot  Of  Water   coming  from  under   the  spillway     4   Drains  on  ‘herring   bone’  pattern  under   chute  base  slabs   collect  and   discharge  water  to   side  wall  drains         5                                         No  ‘continuous’  steel   across  joint  to  prevent   slab  separation   One  layer  of  2-­‐way   steel  reinforcement  at   top  of  slab                   Chute  slab  cracked   over  top  of  Vitrified   Clay  Pipe  (VCP)     6   Standard Bell 8C Spigot Oroville Design dimension scale converted values for 4 inch pipe in drawings. . 5.3693" 0.6846" 10-43" i Eli; 4.0" D1 5.3693" D2 0.6846" T1 m- mu as 4' 214' lb 5.3125" 6.5" 7.625? 1.5? .6875? 6- 6' 2. lb 7.87" 9.05? 10.43? My 7.87? 0.67? 6" D1 I 7.87" D2 10.43" Spillway DESIGN Changed to 6" ID. Drain Pipe: New dimensions should be very close to this table Bl, 7.87" D2, 10.43" D4) A Main SpillwWe Slab (top) 5.85" It 15"Slab 1 4'57") Thickness 69.5% reduction in thickness 61% reduction in thickness ene She-cf /a feral sale-cf gravel :f'z'I/w I                                                                           No  steel  reinforcement   across  slab  joints  to   prevent  separation   No  steel  reinforcement   across  slab  joints  to   prevent  separation   No  steel  reinforcement   across  slab  joints  to   prevent  separation     Chute  base  slabs   designed  to  be   constructed  on  ‘rock’     8             Chute  slab  cracks   associated  with   drains  under  slab   (drain  exits  circled)     9                 Water  flow  pattern   indicates  slabs   displaced  vertically     10         Vertical  ‘clean-­‐out’  pipe  starts   connection  of  next  group  of  drains   under  base  slabs   Connection  of  drains  under   base  slabs  to  connector   outside  of  spillway  walls  and   subsequent  connection  to  wall   drains     11       Sidewall  drain                                       Voids  between  slabs  and   rock  to  be  “Backfilled   with  Concrete”     Chute  base  slabs   designed  to  be   constructed  on  ‘rock’   12     February  9,  2017  –  Stage  #2             Two  streams  of   ‘dirty’  water   indicating  more   exposed  erodible   sediments  under   chute  slabs   Dirty  water  exiting   from  lower  sidewall   drains       13         Wall  drain  flowing  ‘dirty’  water   from  under  spillway  with   suspended  sediments     14             Both  sides  of     spillway  chute   walls  breached  and   eroding  sediment   outside  of  spillway     15           Breach  expanded  along  upper  portion  of  spillway   exposing  erodible  sediments  under  chute  base  slabs     16             ‘Incompetent’  weathered  rock   ‘Competent’  non-­‐weathered  rock     17   ?Incompetent? weathered rock 18 Stage  3  –  February  16,  2017           Water  flowing  from   broken  longitudinal   drain  pipe  outside   spillway  training   wall     19   20                 Soils  eroded  from   under  slabs   Eroded  concrete  surface   exposing  reinforcing  steel  -­‐     indicates  water  scouring   ‘cavitation’  effects   Slab  cracks     21   22       One  layer  of  2-­‐way  steel   reinforcement  at  top  of  chute  slabs     23               l   ee  ba t s y    of wa  top -­‐ t  2  of nt  a r e e y  la rcem e On info re   lab s   se s   24                                             Steel   reinforcement   ‘anchor’   connecting   spillway  base   slab  to  ‘rock’  –   pulled  away   from  slab       Anchor  bars  placed  on   10  ft  x  10  ft  grid     25   Stage  #4  –  Temporary  Repairs  to  spillway  chute               26             Leakage  water   draining  into   transverse  joints     27   29           Flanged  steel  pipe  under   chute  base  slab  ?   30   . tDraln Pipe (missing from slab fracture failure) West Drain Pipe outline created by Pipe Polyethelene Plastic emplacement - a Waterflow seams and ?Voids deeper Under Drain Plpe Gravel retained fro penetrating concreg voids deeper under Drain Pipe (possible source oi Water indU?oed we?tlier?lng of rock - Ieadin?g?to large pogkets. of weakened base rock) - . A 2' '59} 8? - Drain Hip-gas to drain this ay :Ll under the slab - ?Uncontrolled water in "Gravel layer" (no drainage). Erosion Stagnation Pressure risk 32 Erosio of foundation base of wall from broken drain at 5th fence post behind spillway wall. "pulling away" gap in wall:- spillway slab. Rotation indicators of section of main spillway (gaps, br'oken drain erosion on wall foundation, and spillway backcutting). . .53 33 Two piece aligned stripe Target - designed to visually measure further movement (doWnslope pull-way/r tation) u" Wall pulled $an downslope grey material scattoldings ows repairotpull way &extenti1f movemen gap of main spillway, slab - coincident With wide? unmy" mavement Goring/drilling to access/ repair sub Slab regions(s). Angled Ilne marked?. . on surfaced: 34 Spillway Repair - Drilled emplaced rock bolts" to secure concrete slabs green drain WW 35               No  longitudinal   reinforcement  steel   connecting  spillway  slabs   to  prevent  separation   36             No  longitudinal   reinforcement  steel   connecting  spillway  slabs     37         No  transverse   reinforcement  steel   connecting  spillway  slabs   to  prevent  separation     38                           Holes   left  by  ‘extracted’  load  transfer   ‘dowels’  –  see  design  drawing  altered   during  construction   No  transverse   reinforcement  steel   connecting  spillway  slabs   to  prevent  separation     39               Sidewall  drain  connected  to   blue  pipe  discharging  water     40   Pre-­‐Failure  Images     1967  –  Spillway  being  constructed  –  walls  being  cast  –  chute  subgrade  placed             Location  of  future   spillway  breach   Water  percolation   across  spillway     subgrade     1         Location  of  future   spillway  breach   Water  percolation   across  spillway     subgrade     2   >=msmn Br Hom? November  9,  2007         Sidewall   drain  not   flowing   water       Large  trees   growing  next   to  chute  wall   –  roots  able   to  penetrate   and  plug   drains  under   slabs   4   October  7,  2009  –  Repairs  being  made  to  spillway  base  slabs             6             Joints  leaking  water  from   under  spillway  slabs     7   July  9  -­‐  10,  2010                   Cracks  in  spillway   apron  slabs   8     Cracks  in  spillway   chute  slabs   Large  trees  growing   adjacent  to  spillway   wall  –  roots  able  to   penetrate  and  plug   drains                   9   ,71?111'31111] 11111111 1 1 11M SIZIIS i Cracks in spillway discharge slabs 'l Goo'g??l?e?E? ?'rtlh 1} 1998 I 11'1'1313131'11' El?! 327 ft 1.41.1133?. 40411     2012           Wall  drain  not   flowing  -­‐   plugged   Slab  edges   displaced   vertically   (circled)   Large  trees  growing   adjacent  to  spillway   wall  –  roots  able  to   penetrate  and  plug   drains     11     2013         Repairs  underway  to     chute  contraction   joint  at  future  site  of     breach.       12           Repairs  underway  on   chute  contraction   joint  at  future  site  of     breach.       Water  seeping   through  joints  from   under  chute  slabs.   Large  trees  growing   adjacent  to  spillway   wall  –  roots  able  to   penetrate  drains     13     September  5,  2014           Note  slab   edges  and   joints   ‘repaired’   during  2013     14   Patched slab ?herring bone? cracks 15 16 April 14, 2015 4/14/2015 17 ~Wkl?n. u. kc?. . 1.;upp Faoiudu?a i. ?51-?43r. of 5 P?s c? 19 March 2016 m'ox 2 .- g: "mol atJanuary  27,  2017       Wall  drains  not   flowing  -­‐  plugged   Large  trees  growing   adjacent  to  spillway   wall  –  roots  able  to   penetrate  drains     21   22 . 7 't . ho. hu- ko-Who-hu-?m- .1.- 23 Previous  inspection  report  photographs     5/6/08  Inspection  Report   12/14/09  Inspection  Report         24   21. The lower ?ood control outlet chute is shown. Not the markings for the upcoming chute repairs. 6/25/10 Inspection Report 12. The concrete along the spillway chute has been repaired. The repaired herringbone crack pattern is said to re?ect the underlying drain system. Oroville Dam, No. 1-48 25 2/8/11  Inspection  Report     2/16/11  Inspection  Report         26   2/5/13  Inspection  Report                                                   9/8/14  inspection  report       27   2/3/15 inspection report 9. This view looking upstream along the FCO discharge chute shows one tree (arrow) that needs to be removed following a significant effort to remove brush along the outside of the wall. . 12. The FCC channel appeared to be in satisfactory condition. The walls were well aligned and the patches along the chute ?oor remain intact. 13. This view is looking upstream along the FCO channel from the dentates. Dark, vertical stains along the walls indicate the location of the drain outfalls. 28 9. This view looking upstream along the FCO discharge chute shows one tree (arrow) that needs to be removed following a significant effort to remove brush along the outside of the wall. 29           2014  Bureau  of  Reclamation  spillway  design  cross  sections         Water  Stop  Barrier   (WSB)  embedded  in   both  faces  of  joints   Slab  connected  to  foundation   with  concrete  ‘keys’  spanning   construction  joints.     30         Water  Stop  Barrier   (WSB)  embedded  in   both  faces  of  joints         Continuous  steel   reinforcement  across   construction  joints   Slab  connected  to  foundation   with  concrete  ‘keys’  spanning   construction  joints.   Water  Stop  Barrier   (WSB)  embedded  in   both  faces  of  joints   Continuous  steel  reinforcement   across  construction  joints     31