CALIFORNIA NATURAL RESOURCES AGENCY DEPARTMENT OF WATER RESOURCES DIVISION OF SAFETY OF DAMS INSPECTION OF AND RESERVOIR IN CERTIFIED STATUS STATE OF CALIFORNIA 659? 7 Name of Darn Oroville Dam No. 1-48 County Butte Type ofDam earthfill Type of Spillway Gated concrete weir and ungated conc. weir Water is i 22. 2 feet spillway crest and 143.2 feet below dam crest. W3 778.8 it Weather Conditions Sunny and warm Primary contacts Paul Dunlap, Ryan Cooper, Vanesa Morones 0&lVl Joe Eades, Scott Contacts Made Turnquist OF Reason for Inspection Semi?annual inspection Important Observations, Recommendations or Actions Taken a A plan for long-term phreatic surface monitoring within the shell remains outstanding. O&lVl is working with DSOD on a course of action. a Adequate and reliable reservoir drawdown capacity is important for dam safety. continues to study this issue in coordination with DSOD. The long standing seepage area at mid-slope on the left side of the dam has dried up due to the prolonged drought. 8 Wave erosion along the upper slope appears to be disturbing the rock and causing it to move down slope in some areas. Visual monitoring should continue. a The crest road paving project remains on hold. a The original low level outlet valves and new bafer ring have been tested satisfactorily to 4000 combined flow. No significant issues were noted during a follow up inspection. 8 Manufacturing defects have delayed installation of replacement discharge valves. 0 Two new drill holes were recently completed at Oroville-Dam; one to measure V330 on the upper left abutment, and one to measure V530 just from the emergency spillway weir, as shown on photographs 26 and 27. Conclusions Based upon my inspection and information review, the dam, reservoir, and appurtenant facilities are. safe for interim operation pending completion of outstanding DSOD and FERC recommendations, implementation of a phreatic surface monitoring program, and the installation and testing of new low level outlet valves. Observations and Comments Dam The crest road asphalt repairs have been delayed due to higher priority work. However, the roadway is satisfactory for use in the interim. The shoulder repairs remain in satisfactory condition, as well. The embankment, groins and abutments were viewed from the dam crest, the House access bench, and the gallery access parking areas. See photographs 1 through 4. No evidence of embankment instability or other signs of excessive stress were observed. Vegetation and rodent control remain satisfactory. The rock along the upstream slope remains sound, except in a few areas where breakdown is occurring. No action is needed at this time. The surficial rock displacement along portions of the upstream slope appears to be related to wave wash. These areas should be monitored for excessive movement. The long standing damp area at mid?level on the left side ofthe dam has dried out due to the extended drought, photograph 3. WPennington, Eric Holland, inspected by Austin Roundtree Photos taken? Yes N0 Date of Inspection 8122/1 6 cc for Owner/Book Date of Report 9/27/16 DWR 1261 (Rev. 10mg) Sheet 1 of 20 Name of Dam Oroville INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Dam No. 1-48 8/22/16 Date of Inspection Observations and Comments Saddle dams Spillway own 1261 (rev. 10/09) The inspection team walked the right and left foundation galleries, the bypass tunnel, the S-block access, and the Emergency Exit Tunnel. We exited by way of the power house. No new concrete cracks, or any other unusual conditions were observed within the galleries. Mineral buildup at existing cracks and joints continues. An extreme example of buildup is at joint 12?13 in the bypass gallery, photograph 5. Conditions at the abandoned S-Block instrument terminal were normal. Conditions in the emergency exit tunnel appeared to be unchanged, except for ongoing repairs to the drainage collection system. Parish Camp Saddle Dam: The reservoir level was well below the embankment. The graveled crest was clear and in good condition. The slopes appeared to be stable, and the rock remains in good condition, photographs 6 and 7. The rock placed along the groins to control erosion is working well. Rodent and vegetation control were good. Bidwell Canyon Saddle Dam: The reservoir level was well below the embankment. The graveled crest was clear and in good condition. The slopes of both embankments appeared to be stable, and the rock remains in good condition, photographs 8 through 11. The horse trails along the slope of the west embankment have been backfilled. Rodent control was good. Vegetation control along the slope ofthe south embankment is improving, and was sufficient to evaluate the slope. The approach channel was fully exposed and clear, and the security barrier was beached. The concrete approach walls remain stable appearing and in good condition. The Flood Control Outlet (FCO) strUcture appeared to be in satisfactory condition. The spillway bridge appeared to be stable and in satisfactory condition, as well, photographs 12 and13. No new spalling was observed along the bridge bents, photograph 14, for example. The long standing diagonal crack on the left pier for gate 8 appears to have extended to the concrete chamfer below the old telltale paint mark, as evidenced by the length of the recently applied red telltale paint, photograph 14. An extension beyond the chamfer would warrant an investigation into the cause. The FCC discharge chute was inspected from the top of the outlet structure, the trunnion deck, and the road across the river channel. Conditions appeared to be normal. The chute walls were well aligned and appeared to be stable, photographs 15 and 16. The long standing construction joint offsets at the upstream and of both chute walls remain stable, photograph 17. The energy dissipation blocks at the flip bucket appeared to be in satisfactory condition, as viewed from across the river. None of the drains along the chute were flowing. Conditions along the emergency spillway weir were unchanged from recent inspections. The structure was stable appearing, and the concrete remains sound, photograph 18. The gate hoist equipment appeared to be well maintained, photograph 19. The radial gates were inspected from the hoist deck and the trunnion deck. The visible components of the radial gates and trunnion systems appeared to be in satisfactory condition, photograph 20, for example. The usual detritus and bird droppings were observed along the gate members. Regular removal of debris is performed to keep these areas free of corrosion. Sheet 2 of 20 Name of Dam Oroville INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Dam No. 1-48 8/22/16 Date of Inspection Observations and Comments Outlet Seepage DWR 1261 (rev. 10:09) The radial gate anchor tendons are about 50-years old and may be reaching the end oftheir useful life. Tendon testing was recently completed using dispersive wave techniques. Follow up I research and results are expected in the next 12 months. While on the upper deck of the Flood Control Outlet, Paul Dunlap pointed out a crack at the top of the center pier, photographs 21 and 22. This feature is adjacent to the transverse construction joint that separates the two halves of the Flood Control Outlet. The speculation is that the crack resulted from the 1975 Oroville Earthquake. Possible related concrete damage was found on the hoist deck floor, where the construction joint crosses a walk through opening at the back of the center pier, photograph 23. Broken concrete adjacent to the construction joint is also visible from the trunnion deck when looking up at the landing for the hoist deck above, photograph 24. Another indication of movement is discernable as a slight vertical bow on the top of the hoist deck hand rail above the construction joint. None of the observed concrete damage poses a dam safety concern, and may not be linked to a single event. This information is being provided for the record. A number of Category 2 recommendations were made as a follow up to recent radial gate inspection by the HDR. Inc. Resolution ofthe recommendations with DSOD review is ongoing. A seismic analysis by the Division of Engineering indicates that some of the gate members are overstressed under certain loading conditions. DSOD is reviewing the analysis and discussing the issue with The new low level outlet baffle ring has been installed and tested using the original valves. The combined release was 4000 cfs. Testing delays were caused by electro-mechanical issues. Manufacturing defects have delayed installation of replacement valves. The schedule to install the new valves is uncertain. Adequate and reliable reservoir drawdown capacity is important for dam safety. continues to study this issue in coordination with DSOD. Oroville Dam: Flow at the toe weir was normal for the summer months, about 10 gpm. The seepage flow in the galleries remains within historical trends for this time of year. Measurement weirs located along the galleries can be used to the check the flow over a specific reach. Seepage within the emergency exit tunnel appeared to be normal. Repairs to the collection system in the exit tunnel are in progress, as requested. The traditional wet area at mid-slope on the left end the drought conditions. Bidwell Canyon Saddle Dam: The usual reverse foundation seepage from Miners Ranch Reservoir appeared to be normal. Parish Camp Saddle Dam: None. Sheet 3 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Oroville Dam No. 1-48 Date of Inspection 8/22/16 Observations and Comments Instr. The latest monitoring data on file is the December 2015 which covers the period from 10/1/14 through 9/30/15. Oroville Dam embankment: The three active piezometers, P-37(upstream transition), 38(core), and P-9(core) are read at House T. The usefulness of the data for monitoring the health ofthe dam is limited. The plotted AB Joint pressure readings in the core block have not been changing much in recent years, although they varied by 5 to 10 psi in years past. Field staff made an attempt to clean the pipes, with little success. The need for reading these instruments should be evaluated, and if needed, they should be restored. The crack meters and extensometers in the core block are reading within historical limits. An incomplete FERC Part recommendation states that .a plan for long-term monitoring of the phreatic surface within the dam embankment needs to be developed and implemented." 0&lVl is working with DSOD to develop a course of action. Survey monuments are located on the upstream and slopes and along the crest of the dam. Crest settlement remains minimal. The maximum movement being about 9?inches at station 53+00 since 1969. Settlement and displacement along the upstream and slopes remains normal and appears to be stabilizing. A typical, clearly marked crest survey monument is shown in photograph 25. The monuments along the benches are equally Well marked. Bidwell Canyon Saddle Dam: Settlements and deflections remain small and normal. Parish Camp Saddle Dam: Settlements and deflections remain small and normal. The monitoring program for Oroville Dam and the saddle dams is satisfactory on an interim basis, pending development of a system to monitor the phreatic surface at Oroville Dam. Other Two exploratory drill holes were recently completed; one is located on the upper left abutment, photograph 26, and the other is located just of the emergency spillway weir, photograph 27. These holes were completed to obtain V330 data for seismic stability analysis. The holes have been completed with piezometers. DWR1261{rev.10109) Sheet 4 of 20 I INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Oroville Dam No. 1?48 Date of Inspection 8/22/16 1. This View shows the upstream slope of Oroville Dam, as seen from the sloping intake structure. Conditions appeared to be satisfactory. - (rev. 10x09) Sheet 5 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS NameofDam Oroville Dam No. 1-48 8/22/16 Date of inspection . . h-?I 2 I libThis View shows the left groin and the Elevation 815 bench. The minor amount of vegetation will be removed during routine maintenance. Conditions appeared to be normal. DWR1261(rev.10l09) Sheet 6 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Oroville Dam No. 148 Date of Inspection ,~r.The stable appearing Slope remains unchanged from recent inspections. The left gallery access is at left. The traditional seepage area along the left side of the dam was dried out due to the extended period of drought, double arrow. DWR1261 (rev. 10mg) Sheet 7 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Oroville Dam No. 1-48 Date of Inspection 8/22/16 . . .F 1-2} .. {?rm 4. This View from the right groin shows atypical survey monument path and conditions along the right groin. The nature of the dirty cobble fill in the outer shell is evident. Sheet 8 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Dam No. Name of Dam Oroville 1-48 8/22/16 Date of Inspection 5. An extreme example of the mineral buildup and seepage?at joint 12-13 in the bypass gallery. Conditions appeared to be similar to recent inspections. 6. The upstream slope of Parish Camp Saddle Dam remains in good condition, as seen in this View looking DWR1251(rev.10f09) Sheet 9 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS NameofDam Oroville Dam No. 1?48 8/22/16 Date of Inspection . . [Ci-liming meuem 7. The well protected slope of Parish Camp Saddle Dam is shown. Conditions along the crest road were good. ?It, . . 8. The crest road and slope of the west embankment at Bidwell Canyon Saddle Darn remain in good condition. Sheet 10 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Oroville Dam No. 1-48 8/22/16 Date of Inspection 10. View looking towards the left abutment along the south embankment of Bidwell Canyon Saddle Dam. DWR1261(rev.10f09) Sheet 11 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS . Name of Dam Oroville Dam No. 1-48 Date of Inspection 8/22/16 12. View looking right along the Flood Control Outlet Structure. DWR 1251 (rev. 10109) Sheet 12 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam? Oroville Dam No. 1-48 Date of Inspection 8/22/16 '14. This View is looking upstream within the Flood Control Outlet Structure. Gate 8 is at left. Spalling at the left bridge bent remains dormant, as evidenced by the unbroken paint at the far right. The same is true of the opposite abutment. The marked crack, arrow, has extended downward to the lift line over a long period of time. It will likely stop at this location. If not, the conditions should be evaluated. Sheet 13 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS NameofDam Oroville - Dam No. 1-48 Date of Inspection 8/22/16 ?15. View looking along the left chute wall of the Flood Control Outlet. The wall was stable appearing and well aligned. Vegetation has been removed from behind the wall. 5? 16. View looking along the right chute wall of the Flood Control Outlet. The wall was stable appearing and well aligned. Long standing, stable, joint offsets occur at the upstream end of both walls, at the construction joint between the chute wall and the outlet structure, photograph ?17, for example. DWR1261 (rev. 10/09) Sheet 1?4 Of A INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS NameofDam Oroville Dam No. 1-48 8/22/16 Date of Inspection U5 "am.ul mung 1mm". oh? . 17. A stable, inward joint offset remains unchanged at the first construction joint past the Flood Control Outlet on both sides of the discharge chute. The initiation of this long standing feature is unknown. ?18. The emergency spillway weir remains stable appearing and in good condition. The fig tree at the arrow will be removed. Sheet 15 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Oroville . Darn No. 1-48 Date of Inspection 8/ 22/ 1 6 19. This View of the Flood Control Outlet hoist deck is looking north, The equipment appeared to be in satisfactory condition. A 12?inch travel test of the radial gates will be performed during the first week of October 2016. 20. Gate 7, left, and Gate 8, right, at the Flood Control Outlet. The dark areas on the radial arms are bird droppings and other detritus that are removed from time to time. The exposed anchor tendons are protected by plastic covers. The ends of the tendons are greased and covered by a plastic cap. Sheet 16 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name ofDam Oroville Dam No. 1-48 8/22/16 Date of Inspection 21. This View is looking upstream at the center pier of the Flood Control Outlet. The top deck is visible. A crack was recently noted at the location shown, and is also shown in photograph 22. DWR1261(rev.10f09) Sheet 17 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Oroville Dam No. 1-48 Date of Inspection 8/22/16 22. Close up of the crack in photograph 21, as seen looking down from the top deck of the Flood Control outlet. .23. This picture shows the transverse construction joint separating the two halves of the Flood Control Outlet where it crosses the walk through opening at the upstream side of the center pier. Buckled concrete is visible within the oval. DWR 1261 (rev. 10/09) Sheet 18 of 20 INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Darn Oroville Dam No. 1-48 Date of inspection 8122/16 24. This View shows the Flood Control Outlet center pier looking upstream at the landing for the hoist deck. The solid arrow shows the construction joint. The dashed arrow is pointing at spalled concrete that may be associated with the concrete damage in photographs 21, 22 and 23. hfpzu-Fr - . 3:52: .2: -3: as ?e 25. Typical survey monument along the crest of Oroville Darn. Monuments along the slopes are equally well marked and maintained. a I DWR 1261 (rev. 10109) Sheet A of A INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Or oville Darn No. 1-48 8/22/16 Date of Inspection 26. This View is looking down slope along the left groin of the dam. V530 measurements were taken at a new drill hole indicated by the arrow. 27. This View is looking generally from the Flood Control Outlet deck. V530 measurements were taken at a new drill hole indicated by the arrow. A portion of the emergency spillway weir is at the lower right. Sheet 20 of 20