File; State of California The Resources Agency DEPARTMENT OF WATER RESOURCES DIVISION OF SAFETY OF DAMS INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS Name of Dam Oroville Dam No. 1-48 County Butte Type of Dam ERTH Type of Spillway gated concrete weir chute and undated weir Water is 94.3 feet below spillway crest and 116.3 feet below dam crest. {above,below} (abovebelowl Weather conditions sunny and mild Contacts made Maury Miller. Kevin Wright. Pat Whitlock. and Bill DickensJ OFD Leon Holden. FERC Paul Dunlop. Don Walker. Kevan Samsam. and John Rizzardo Reason for inspection Periodic evaluation Important Observations, Recommendations or Actions Taken At the Bidwell Bar Canyon Saddle West Dam, the toe drain remains covered by berry vines and tree growth. The vines are to be removed for at least 10 feet beyond the toe, the tree's lower limbs pruned to allow physical access under the tree, and the toe drain exposed. Parrish Camp Saddle Dam should be inspected during the next inspection to verify its assumed good condition. The Palermo Outlet Works 12?inch fixed cone dispersion valve should be full travel cycled annually and DSOD should observe the next cycling. Conclusions From known information and from my visual inspection, the dam, reservoir, and appurtenances arejudged satisfactory for continued use. Observations and Comments Main Embankment Dam: The visible portion of the upstream slope, the crest, and the slope are in satisfactory condition with no indication of instability. Vegetation control is satisfactory. The uneven upstream rock slope protection is satisfactory with no significant breakdown of the rock. The 815 bench is exposed about 7 feet above the reservoir surface. The crest pavement has cracks that are not related to embankment stability. The slope is covered with dry yellow brown grass and yellow and green star thistle. The 000 is doing trail maintenance on the trails across the slope. The electrical panel controlling power for lighting in the right foundation gallery had been destroyed by fire and is being replaced. Temporary lights are strung to provide light until the repairs are complete. We entered left foundation gallery and descended to the core block. As we descended the gallery became wetter but never significant; in only 3 or 4 places were the flow rates sufficient to drip free from the ceiling orjet free from the wall. The conditions and seepage in the left foundation gallery and the Instrumental Terminal gallery are normal for this dam. Calcite deposits are present at the lower elevations and either on the floors or steps or along the joints that flow. All gallery seepage is clear. Many wet surfaces are rust colored from the seepage. Terminal now only monitors the dripping from the piezometer tubing bundle. This clear seepage is collected in a pan where the discharge is measured. Typed by *Use Field Sheet Standard Inspected by DR Borger Date I Numbers and Items Date of Inspection 6/2/2009 cc for Owner/Book (See Reverse Side) Date of Report Photos taken? no rill) 57-3140,,- DWR1261 (sub) (ms/95) Pagel Sheet of _3 Sheets 0 205? If I INSPECTION OF .M AND RESERVOIR IN .FIED STATUS Name of Dam Oroville Dam No. 1-48 Date of inspection 6/2/2009 Bidwell Bar Canyon Saddle Main Dam: The visible portion of the slope, the crest, and the rock covered upstream slope are in satisfactory condition with no indication of instability. I observed no rodent activity. The toe is submerged by Miners Ranch Dam, No 63-9. As Lake Oroville is presently lower in elevation than Miners Ranch reservoir, seepage emerges from the upstream toe, ~1 gpm. Bidwell Bar Canyon Saddle West Dam: The visible portion of the upstream slope, the crest, and the slope are in satisfactory condition with no indication of instability. I observed no rodent activity. The toe drain remains covered by berry vines and tree growth. These vines should be removed for at least 10 feet beyond the toe, the tree's lower limbs pruned to allow physical access under the tree, and the toe drain should be exposed. Parrish Camp Saddle Dam: I did not inspect this embankment. The reservoir is still well below the upstream toe. This embankment is usually inspected when the reservoir is against it, but has not been inspected since 2004 because of low reservoir conditions. It should be inspected during the next inspection to verify its assumed good condition. Spillway: The flood control outlet structure is located just beyond the right end of the main embankment. All eight radial gates are closed. The approach and exit channel of the spillway are clear and unobstructed. The structure, radial gates and mechanical equipment appear in satisfactory condition. The reservoir is below the elevation of the approach apron and channel. The seals and seal inflation system for Gate 4 have been rehabilitated but not tested with water against the gate. The rehabilitation of Gate 5 and then Gate 3 is planned for August. The wire ropes, lifting hitches, tendon anchors, trunnions, and trunnion beams appear in satisfactory condition. The spillway chute and walls appeared stable. However, the first joint past the trunnion deck in the left wall is offset by what appears to be 1-2 inches. The offset condition appears long-standing. The existing diagonal crack at the left abutment has calcite at the end of the crack which may be obscuring the monitoring paint. The crack will continue to be monitored by The emergency spillway is located to the right of the flood control outlet structure. The approach, control section, and exit channel of the emergency spillway are clear and unobstructed. The parking lot appears to be above the east end of the weir crest but may not be a significant impairment. The 1982 spillway analysis is for a PMP storm producing 971,372 (269 csm) peak inflow and 839,434 peak discharge from the 3,607 square mile drainage area. This storm event includes the failure of Butt Valley Dam, No. 93. The residual freeboard is 3.3 feet. The current TCW for this dam is 36, which appears to be appropriate. In 2003, the hydrology of the basin was updated for the owner (by DWR Flood Management) using the HMR 59 in which Butt Valley Dam does not overtop and fail. The peak inflow is reduced to 725,000 cfs. The owner is performing a study routing that new inflow through the flood control structure. DSOD will review the new storm routing after the study is complete. Outlet: The outlet consists of two 72-inch conduits through the plug in Diversion Tunnel Flow on each conduit is controlled by a 72?inch spherical guard valve immediately of the tunnel plug followed by a 54-inch fixed cone dispersion valve. Additional capacity is also available through the two 22-foot diameter penstocks to the power plant and through the 72?inch intake for the Palermo Outlet Works. This latter flow is controlled by a 12?inch fixed cone dispersion valve. DWR1261 (sub) (2i23i95) Pagei Sheet of _3 Sheets INSPECTION OF .M AND RESERVOIR IN CER..FIED STATUS Name of Dam Oroville Dam No. 1-48 Date of inspection 6/2/2009 visually inspected the sloping intake structure from a distance as they were installing shutters in the intake during the inspection. What I observed is satisfactory. The outlet is closed. The valves were full travel exercised in July 2008 and used during the winter of 2008?2009 to provide reservoir releases when the reservoir was lower than minimum generation pool I- elevation. All components of the outlet remain in satisfactory condition. I did not inspect the Palermo Outlet Works. The 12-inch fixed cone dispersion valve has not been full travel cycled during a DSOD inspection. It should be full travel cycled annually and DSOD should observe the next cycling. Seepage: The total left foundation gallery seepage is ~5 gpm. At the access gallery to Instrument Terminal the seepage passes two weirs before dropping into the sump. One weir measures flow from the left foundation gallery and the other from the right foundation gallery and the Instrument Terminal gallery. All observed seepage flows with the galleries appeared to be normal. Orifice flow from the toe weir is gauged at 14.7 gpm. Instrumentation: The active instrumentation network is described in the 6 May 2008 DSOD inspection report. There has been no change to the instrumentation network since then and no instrumentation data or any evaluation of the data has been provided to DSOD since then. Based on my field inspection and my discussion with staff present during the inspection, and a review of the last several reports, as well as the Performance Report No. 11 (dated August 2004), the dam appears to be performing normally. DWR1261 (sub) (2(23l'95) Page1 Sheet of _3 Sheets