Sediment Removal Phase
The sediment removal phase constitutes the construction phase of the Proposed Project. Approximately 2.9 million cy of sediment is the current excess amount of sediment in the reservoir; however, additional sediment accumulation is anticipated during the upcoming storm seasons due to the denuded surfaces of the watershed created by the 2009 Station Fire. Proposed Project excavation activities will take place within the project’s excavation limit boundaries. The proposed excavation will remove approximately 2.9 million cy of current excess sediment in the reservoir in addition to any additional sediment received from storm flows during the Proposed Project sediment removal phase.
Excavation/Reservoir Configuration
At the time the NOP was released, an area of 178 acres was considered for the Proposed Project; this was refined to an area of 120.42 acres for the EIR. Specific excavation limits and reservoir configuration for the Proposed Project are shown in Figure 2.5-1: Proposed Project, Configuration A Excavaton Area and Configuration A Management Area, Option 1. As shown in Figure 2.5-1, the basin will be excavated to a 985-foot elevation at the face of the dam, sloping up to a 1,070-foot elevation at approximately 4,977 feet north of the dam. In addition to the sediment excavated as part of the Proposed Project, sediment stockpiled at Johnson Field as part of the IMP will also be removed. Proposed Project excavation will not involve the Oak Grove area of Hahamongna Watershed Park, the area of the reservoir above the northern end of excavation limits, or the City of Pasadena’s spreading grounds on the east side of the basin.
Removal Method Project Site and Easement Removal Goal