Sediment, shrubs, herbaceous vegetation, and debris will be removed from portions of the Little Panoche Creek channel on the right (R) side of the California Aqueduct (Aqueduct) at MP 95.56. Heavy equipment will be used in the creek channel to remove vegetation and sediment blocking corrugated culverts, inlet gates, and an underchute that transfers creek flow from the west side of the Aqueduct to the east side. The corrugated culverts are located about 540 feet upstream of the Aqueduct road and the underchute is located about 500 feet downstream of the corrugated culverts. Additionally, sediment removal will occur in portions of the channel, between these culverts, where sediment mounds have accumulated and restrict water flow. A settling pond is located immediately south of an existing 35-foot-wide berm bordering the south bank of the creek channel. The settling pond and berm were constructed to limit creek flows through the underchute. When creek flows are high enough, the berm is designed to break, allowing a portion of the creek flows to fill the settling pond instead of potentially exceeding the capacity of the underchute and causing uncontrolled release of creek flows into the Aqueduct.
Inlet gates on the settling pond are located at MP 95.57R about 80 feet south of the underchute. In the event the settling pond nears capacity, these gates are used to control the discharge of creek water from the settling pond into the Aqueduct. Heavy equipment will be used to remove sediment and vegetation from the settling pond side of the drain inlet gates.
The overall project involves excavating approximately 300 cubic yards of sediment from the culverts, underchute, and creek channel and approximately 100 cubic yards from the drain inlet gates. Some of the excavated sediment will be used to repair an approximately 40-foot section of the 35-foot-wide berm located between the south side of the creek channel and the settling pond; the berm breached during the 2022-2023 winter flows. Any sediment not needed to repair the berm will be placed in a dump truck and will be taken to an existing spoil pile at the San Luis Field Division yard.
Sediment and vegetation removal will not occur at the left side of MP 95.56 (Figure 1). Instead, large vegetative debris, that was carried by creek flows during 2022-2023 winter and spring storms, and illegally dumped appliances and other debris that block the underchute and creek channel on the left side of the Aqueduct will be removed from the creek channel and disposed of at appropriate offsite locations.
These areas must be cleared before the 2023-2024 storm season to prevent uncontrolled creek flows from overtopping and potentially breaching the Aqueduct. The State Water Project will benefit.