STATE OF CALIFORNIA CALIFORNIA NATURAL RESOURCES AGENCY DEPARTMENT OF WATER RESOURCES DIVISION OF SAFETY OF DAMS . INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Darn Dam No. 1-48 County Butte Type of Dam Earth fill Type of Spillway Gated concrete weir and ungated concrete weir Water is 202 feet below spillway crest and 223 feet below dam crest Elev. 699' Weather Conditions Sunny and warm Paul Dunlap Bill Dickens (OFD), Joe Eades (OFD), Robert Trang (DOE), Vinh Tran (FERC), Paulo Virreira (FERC), some days attended: David Sarkisian Nick George Contacts Made Barbara Holbrook (OFD), Eric See (OFD), John Rizzardo Reason for Inspection Semi?annual inspection Important Observations. Recommendations or Actions Taken In response to the Part report, the owner is currently consulting, private firms that specialize in non? destructive testing (dispersive wave) to test the anchor tendons of the Flood Control Outlet (FCO) gates. The owner is anticipated to submit the findings by November 1, 2017. This approach is acceptable. As requested in the previous inspection report, a long term plan should be developed to monitor the phreatic surface within the dam. The owner is currently developing a plan to assure sufficient drawdown capacity for this dam. This effort is currently coordinated with DSOD. Monitor the mid-slope seepage on the left side of the dam. Vegetation in this area needs to be periodically controlled to allow a thorough visual inspection. Visually survey the irregular rock movement on the upstream slope of the dam. It appeared that wave erosion caused some rock movement in the past. Stranded logs and debris on the upstream slope of the main dam and saddle dams need to be periodically removed. Vegetation and debris at the foundation drain outfalls of the emergency spillway structure need to be removed. The owner plans to overlay the crest pavement. The work has been delayed due to other high priority work. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for interim operation, pending completion of outstanding DSOD and FERC recommendations. Observations and Comments Da_m The upstream slope of the dam appeared to be satisfactory, with no signs of slope instability (Photo 1). The 815? bench was traversed and it appeared to be uniform (Photo 2). The riprap on the upstream slope face was intact. No visible signs of irregular rock movement were observed. The owner needs to continue the visual survey for any irregular rock movement on the upstream slope face of the dam. Stranded logs and debris on the upstream slope needs to be periodically removed. The paved crest appeared to be uniform (Photo 3). The cracks that were observed during the previous inspections have not significantly widened. The owner plans to overlay the crest pavement within the next two to three years. The work has been delayed due to other high priority Inspected by Yogi Pirathapan W'Jhyiufltl I Photos taken? Yes No Date of Inspection 822/201 5 cc for Owner/Book Date of Report 8/6/20?r1 5 I in ?i I DWR 1261 (Rev. 10/09) Name of Darn Oroville No. 1-43 Date of Inspection 7/20, 21 &22/201 5 Observations and Comments work. The right groin, and the slope benches at 750?, 575?, and 400' were traversed. The slope appeared to be satisfactory, with no indication of slope stability issues or surficial slope failures. Vegetation control on the sl0pe is satisfactory. The historical damp area at mid-level along the left slope was dry. Less vegetation growth was observed compared to the past. The on-going drought and the low reservoir water level may be contributing factors. No significant rodent activity was observed. The left foundation gallery, the river valve chamber access, the outlet control equipment chamber, the right foundation gallery (Photo 5), the core block tunnel, the bypass tunnel, the S?block access, and the emergency exit tunnel were walked. The condition of the galleries, tunnels, and valve chamber has not changed since the last inspection and no new visible concrete deficiencies were observed. Mineral buildup continues in the drain outfalls, concrete joints, existing cracks and gallery gutters (Photo 6). Mineral deposits need to be cleaned in drain outfalls and concrete joints where it obstructs free water flow. Saddle Bidwell Canyon Saddle Dam: The upstream and slopes of the main dam and the west Dams dam appeared to be satisfactory, with no signs of slope instability (Photo 7). No water was impounded by either dam. The gravel?covered crest appeared to be uniform. The rock riprap on the embankments was intact and in good condition. Vegetation control was excellent on both dams and no significant rodent activity was observed at the dams. Parish Camp Saddle Dam: The dam embankment appeared to be satisfactory. The water level was well below the embankment. Stranded logs on the upstream slope need to be periodically removed (Photo 8). The rock riprap on both faces of the embankment was in excellent condition. The unpaved crest appeared to be uniform. Vegetation control was good, and no significant rodent activity was observed. The rock placed in the erosion gullies along both groins appeared to provide effective erosion protection. The flood sensor system beyond the toe of the dam was well maintained. Sgillway The Flood Control Outlet (FCO) approach was clear and unobstructed (Photo 9). The safety buoy line was intact and the anchors appeared to be satisfactory. The FCO structure appeared to be satisfactory with no visible concrete or structural deficiencies. The condition of the training walls has not changed since the last inspection. The discharge channel was not walked this time; however, a visual inspection from some distance indicated no visible signs of concrete deficiencies. The undesirable trees behind the chute wall have been removed, as requested during the last inspec?on. The spillway bridge, service deck (upper), trunnion deck (lower), and trunnion deck walls appeared to be stable and no new concrete cracks or spalling were observed. The telltale paint applied on both abutments of the spillway bridge did not show any signs of new concrete cracks or spalling (Photo 10); however, the owner should continue to monitor for any concrete deficiencies. The FCC outlet gates were inspected through the bays in the service deck and trunnion deck. The visible portion of the radial gates and trunnion system appeared to be satisfactory (Photo 11). No visible structural deficiency or unusual condition was observed on the radial gates. The water supply line for the radial gate seal inflation system appeared to be well maintained. The hoist DWR1261(rev.10109) Sheet 2 of 11 Name of Dam Oroville Loin No. 1-48 Date of Inspection 7/20, 21&22/2015 Observations and Comments Outlet Seepage equipment also appeared to be well maintained. In response to the Part report, the owner is currently consulting private firms that specialize in non-destructive testing (dispersive wave) to test the anchor tendons of the Flood Control Outlet (FCO) gates. This is a Category Probable Failure Mode (PFM). The owner is anticipated to submit the findings of the anchor testing by November 1, 2017. This approach is acceptable. The emergency spillway structure also appeared to be satisfactory (Photo 12); no visible concrete deficiencies were observed. The overflow weir and approach were clear and unobstructed. The concrete apron, which is located along the right portion of the structure, appeared to be in good condition. The foundation drain outfalls need to be cleared of vegetation and debris. Isolated brush and other woody vegetation in the channel need to be periodically removed. The owner is currently working to rehabilitate the River Valve Outlet System (RVOS). During the rehabilitation, the existing two outlet valves (HBV) will be replaced with new valves and a new baffle ring will also be installed. The outlet chamber and controls were well maintained and the condition of the outlet valves could not be assessed from the chamber (Photo 13). The owner is currently developing a plan to assure adequate reservoir drawdown capacity for dam safety purposes. This plan is currently coordinated with DSOD. Oroville Dam: No signs of seepage were observed along the toe, groins or through the visible portion of the slopes, except for the historical seepage at mid-level along the left slope. Seepage in this area was relatively low due to the on-going drought and low water head in the reservoir. The owner needs to establish a means to monitor the extent of the seepage in this area to develop year to year seepage trend. The owner also needs to continue controlling vegetation periodically to allow a thorough visual inspection. A flow rate of 109pm was estimated through the toe weir. Flows through the gallery gutters and weirs were normal. Gallery weirs can be used to identify seepage over a Specific reach of a gallery. Seepage flow started at elevation 744? when entering into the right foundation gallery. Seepage flow in the emergency exit tunnel was also normal. Seepage flows in the foundation galleries were relatively low as they reflected the reservoir water head. Bidwell Canyon Dam: Historical seepage through the dam foundation was present (Photo 14). A flow rate of 0.5gpm was estimated. The flow was clear and free of sediments. Otherwise, no signs of seepage were observed along the toe, groins or through the embankment. Parish Camp Saddle Dam: No signs of seepage were observed at the dam as the reservoir level was well below the embankment. The Dam Safety Surveillance and Monitoring Report provided to DSOD was dated December 2014, which extends the data from 10/1/2013 to 9/30/2014. Instrumentation data was discussed in the last inspection report dated 3/6/2015. No unusu I settlement or deflection was reported either on the main dam or the saddle dami-Jhe three ac- ve piezometers, which are located at House T, indicated normal readings. During the inspection, no abnormal readings were Sheet 3 of 11 Name of Darn Oroville Wm No. 1-48 Date of Inspection 7/20, 21 &22/201 5 Observations and Comments observed on the crack meters or extensometers. As requested in the last inspection report, a plan for long-term monitoring of the phreatic surface within the dam embankment needs to be developed and implemented. The plugged pipes in the AB joints were cleaned by the owner about a year ago; however, this effort did not yield any improvement in the readings. The owner plans to address this issue in the next Based on my field inspection, my discussion with field staff, and my review of available data, Oroville Dam, the appurtenant structures, and the saddle dams, appeared to be functioning normallyLia-2?; 1.43121 Fax! t" ?1 Iii-Windy Photo 1- The rock riprap covered upstream slope appeared to be satisfactmy. This picture is looking towards the northwest from the sloping intake structure. DWR 1261 (rev. 10l09) Sheet 4 0f ?l'l Name of Dam No. 1-48 Date of Inspection 7/201 21&22/2015 Photo 2 The 815? bench appeared to be uniform stable. . - Photo 3 The paved crest was uniform. The owner plans to overlay the crest in the next two to three years. DWR 1261 (rev. 10109) Sheet 5 of I ?l?l Name of Dam Oroville Lam No. 1-48 Date of Inspection 7/20, 21&22/2015 Photo 4 The slope bench at 715? appeared to be uniform and stable. No surficial distress or signs of slope instability was noted. Photo 5 The right foundation gallery was satisfactory. No unusal condition was observed. DWR1261 (rev. 10109) . Sheet of i Name of Darn Oroville 'me No. 1-48 Date of Inspection 7/20, 218:22/2015 Photo 6 Mineral deposit continues in the foundation galleries, which needs to be periodically cleaned to allow free ?ow of seepage waterPhoto 7 The Bidwell Canyon Saddle dam appeared to be satisfactory. The manhole in the foreground is for a sewer line that traverses the dam for the most part at an angle to the dam axis. DWR1261(rev.10l09) Sheet 7 of 11 Name of Dam Oroville cam No. 1-48 Date of Inspection 7/20, 21&22/2015 air-'1. -. I I ?h ha. Photo 8 Stranded logs on the upstream slope of the Parish Camp Saddle dam need to be periodically removedPhoto 9 The FCO approach was clear and unobstructed. Vegetation control was excellent. The buoy line was intact and well maintained. DWR1261 (rev. 10:09) Sheet i of Name of Dam Oroville ?wm No_ 1-48 Date of Inspection 7/20, 21 &22/201 5 Photo 10 No new cracks or spalling were observed along the spillway bridge beatsPhoto 11 The radial gates and gate seal system appeared to be satisfactory. The owner has recently completed replacing the gate seal in?ation system for all the radial gates. DWR 1261 (rev. 10:09) Sheet 9 of 11 Name of Dam Oroville cam No. 1-48 Date of Inspection 7/20, Photo 12 The emergency spillway weir, concrete apron, and discharge channel appeared to be satisfactory. Undesirable vegetation in the discharge channel needs to be periodically removed. Sheet 10 of 11 Name of Darn Oroville No. 1?48 Date of Inspection 7/20, 218:22/2015 1n," . ..- .v Illa; Photo 14 Historcial seepage through the upstream toe area at Bidwell Canyon Saddle Dam was present. The amount and the extent of the seepage have not changed from the historical trend. .r a . \l-rlAu I '54? a; . .I :1er ,1 1 is - Sheet 11 of 11