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or near the FCO Spillway chute and the Emergency Spillway: (1) a landslide investigation was performed in 2004 near the FCO Spillway chute on the lower left slope near the Feather River [7]; and (2) a new boring with downhole shear wave velocity measurements was completed in 2016 downstream of the larger monoliths of the Emergency Spillway [8]. Another such boring was completed on the left abutment of the embankment dam at the same time. In 2004, slope instability was observed about 30 m (100 ft) to the south of the FCO Spillway dentates. While there was no concern about the stability of the FCO Spillway chute, there was concern that a large block of soil and rock might slide into the Feather River channel, blocking the passage of water flowing from the Hyatt Power Plant. This questionable slope was located in an area where the 1960s dam contractor had wasted soil and rock materials at the completion of dam and spillway construction. Historical aerial photos and topographic maps were examined, and it was determined that the slope instability was localized to within the old waste/spoil areas, which were estimated to be relatively thin (less than about 5 m [16 ft]. Based on the work completed in 2004, DWR geologists concluded that it was highly unlikely a large rock or soil mass would fail and block the river channel. No remediation of the unstable materials was completed in this area. One rock-core boring was drilled downstream of the Emergency Spillway in September 2016 as recommended by the 2014 Director’s Safety Review Board for the Ninth Five Year Part 12D Safety Inspection Report for Oroville Dam [9]. The purpose of this boring was two-fold: (1) to obtain site-specific shear wave velocity (Vs30) data for the rock foundation; and (2) to install a piezometer to evaluate potential uplift pressures beneath the Emergency Spillway’s concrete monolith structures. Unfortunately, during the Oroville Emergency Response in February 2017, this newly-installed open standpipe piezometer had to be destroyed, as the area was covered with grouted-riprap armoring for added protection prior to and following the initial spill at the Emergency Spillway. 3. DEVELOPMENT OF THE OROVILLE EMERGENCY RECOVERY EXPLORATION PLAN The damaged FCO Spillway chute was operated intermittently between February 2017 and May 19, 2017 to release water from Lake Oroville. While one team of engineers, geologists, and construction specialists focused on ongoing operations, monitoring, and repairs through the remainder of the 2017 flood season as part of the Oroville Emergency Response phase, a second team of engineers, geologists, and construction specialists began to work on the design for the repairs that would begin in Spring 2017 under Oroville Emergency Recovery. The design work for the Oroville Emergency Recovery phase began in early-March 2017, less than a month after the initial incident. Regardless of the final condition of the structures after the operation of the FCO Spillway chute finally ceased in May 2017, 108