County of San Diego Department of Parks and Recreation-led Emergency and Routine Maintenance Activities at the Pilot 1 and Smuggler’s Gulch 1 Channels

County of San Diego Department of Parks and Recreation-led Emergency and Routine Maintenance Activities at the Pilot 1 and Smuggler’s Gulch 1 Channels

Project Number: PRJ-1111938. Subsequent Action Notice of Determination for the approval of a Substantial Conformance Review (SCR) for County of San Diego Department of Parks and Recreation-led emergency and routine maintenance activities at the Pilot 1 and Smuggler’s Gulch 1 channels. Description of Previous Action: On June 9, 2020, the City of San Diego City Council certified the Final Environmental Impact Report (EIR) for the Municipal Waterways Maintenance Plan (MWMP). The Final EIR provided a project-level and program-level analysis for maintenance and repair activities at existing stormwater facilities in order to reduce and manage flood risk. The project-level analysis included potential maintenance and repair activities at the Pilot 1 channel and the Smuggler’s Gulch 1 channel (north of Monument Road) in accordance with the Facility Maintenance Plan of each facility. On October 24, 2023, the County of San Diego Board of Supervisors adopted an addendum to the MWMP EIR for the Tijuana River Valley Dredging Project, which analyzed County of San Diego Department of Parks and Recreation (County DPR)-led channel maintenance activities within the Smuggler’s Gulch channel (north and south of Monument Road) and the Pilot 1 channel. Description of Subsequent Action: City of San Diego Development Services Department approval of a Substantial Conformance Review (SCR) for County DPR-led maintenance activities at the Pilot 1 and Smuggler’s Gulch 1 channels. The project includes: 1) an after-the-fact SCR for emergency maintenance activities at the Pilot 1 and Smuggler’s Gulch 1 channels; and 2) future County DPR performed routine maintenance activities at these two facilities. The project components are discussed below. Emergency Maintenance Activities Emergency maintenance activities consisted of the removal of accumulated sediment, vegetation, and debris in order to restore the original design dimensions of the Pilot 1 and Smuggler’s Gulch channels. The emergency work consisted of dredging sediment from the Smuggler’s Gulch channel, north of Monument Road, to the Disney Crossing and from the Disney Crossing north towards the Pilot channel. Approximately 1,743 linear feet of the Smuggler’s Gulch channel, north of Monument Road, and approximately 2,101 linear feet of the Pilot channel were dredged. In order to clear the channels to restore them to pre-emergency conditions, heavy machinery such as excavators, metal-tracked dozers, front-end loader, backhoe, trencher, skid steer/bobcat, sweeper/scrubber, and pumps were brought in through existing access roads to the sites. The dredging activities included using tractors to dig and load sediment into dump trucks that removed the sediment and vegetation from the site. The emergency work was conducted within the boundaries of the previously approved and permitted maintenance work areas, including staging areas, access roads and turnarounds, and no mitigation areas were impacted by the emergency maintenance activities. All emergency work activities occurred during the day. The sediment and equipment used during the emergency dredging effort were stored at Staging Areas B and D. The emergency work occurred between March and November 2024. The emergency maintenance work crew consisted of a qualified biologist from HELIX Environmental Planning, Inc. (HELIX), and Whillock Contracting, Inc. The qualified biologist provided nesting bird surveys, biological construction monitoring, and compliance monitoring support for the duration of the emergency maintenance activities. Biological surveys and construction monitoring were conducted from February to October 2024. Additionally, the qualified biologist flagged the limits of work adjacent to sensitive biological resources including vegetation and trees and monitored all vegetation removal and trimming to ensure no sensitive species were impacted. The qualified biologist also checked that Best Management Practices (BMPs) were installed during work (e.g., drip pans, sandbag berms, etc.), and noise berms and other noise minimization measures were functioning and documented. The location of stockpiling within Staging Areas B and D occurred away from jurisdictional areas in order to avoid runoff or erosional impacts. Future Maintenance Activities The project involves one-time routine channel maintenance of the entirety of the Pilot 1 channel and Smuggler’s Gulch channel (north and south of Monument Road) utilizing grant funds awarded through the U.S. Environmental Protection Agency (EPA). The proposed maintenance activities will occur outside of the bird breeding season, during the daytime, and within the boundaries of the previously approved maintenance areas utilizing previous methods and equipment and will not exceed the previously permitted/mitigated footprints of the Pilot 1 and Smuggler’s Gulch channels. Dredging and Sediment Removal Activities Future routine maintenance activities include routine dredging and sediment removal activities within the approximately 5,400-linear foot Pilot 1 channel and the approximately 4,300-linear foot Smuggler’s Gulch channel (north and south of Monument Road) for a total of approximately 9,700 linear feet. The scope of work includes the removal of sediment, vegetation, trash, and debris to increase the flood conveyance capacity within these channels. Maintenance methods will include evacuation, the use of mechanized equipment inside and outside the channels, temporary access/loading, temporary staging, stockpiling, diversions, and hand removal of vegetation. The locations of the maintenance areas and associated maintenance activities are shown on Figure 1 and described below: x Pilot 1 channel: Dredging would occur within an existing 23-foot-wide corridor (approximately 5 feet deep with a 15-foot-wide channel bottom) for a total length of approximately 5,400 feet. Activities in the channel would include a combination of mechanized dry excavation and bucket fill and dredging. Grading to re-construct the channel bank with compacted soil material may also occur as needed. An existing gabion mattress is located within the Pilot channel at its confluence with the Smuggler’s Gulch channel and may be repaired/maintained as part of the project. x Smuggler’s Gulch channel (north of Monument Road): Dredging would be limited to a footprint approximately 20 feet wide and up to approximately 2,900 feet long and would consist of dry excavation to maintain the channel. Other improvements would include cleaning the existing culverts located under Monument Road and at the Disney Crossing. x Smuggler’s Gulch channel (south of Monument Road): Dredging would be limited to a footprint approximately 20 feet wide and up to approximately 1,400 feet long and would consist of dry excavation. Construction Access and Turnaround Areas Construction access would utilize existing paved roads, staging areas, excavation areas, and turnarounds, and three existing off-road routes (Figure 1). One off-road access route runs east from Hollister Road, on the south side of the Hollister Street Bridge, providing access to the southern bank of the Pilot 1 channel, east of Hollister Street. Another route runs parallel to the Smuggler’s Gulch channel. The third leads south from an unnamed road that runs in an east-west direction between Hollister Street and Saturn Boulevard. Each of these routes are pre-existing, hard-packed dirt roads and are also used as equestrian trails. The access route along the Smuggler’s Gulch channel includes an existing 15-foot-wide access ramp from the east bank that extends approximately 75 feet into the channel, north of the Disney Crossing. Three equipment turnaround areas would be utilized within the Pilot 1 channel, approximately 30 feet by 24 feet. Material and Equipment Staging Two existing material and equipment staging areas (Staging Area B and Staging Area D) are proposed in disturbed upland areas for storage of earth-moving equipment during construction, as well as temporary handling of dredged soil materials (Figure 1). Fresh fill and dredge spoils would be stored and transferred to and from staging areas prior to landfill placement. Manual and mechanical separation would also occur to sort sediment, vegetation, debris, trash, and tires. Measures including solarization of all cut biomass removed from the channel areas followed by mulching and subsequent off-site material disposal would also be implemented to prevent the spread of shot hole borer. Staging Area B is located east of the Smuggler’s Gulch channel and Staging Area D is located further east of the project site adjacent to the South Bay International Wastewater Treatment Plant. The locations of each staging area are further described below: x Staging Area B is east of and adjacent to the Smuggler’s Gulch channel in disturbed lands previously used for staging. There is a permanent earthen berm between this area and the Smuggler’s Gulch channel protecting it from flooding. Permanent gated access is provided from Monument Road. No excavation or grading would be necessary in this area. x Staging Area D is located adjacent to the South Bay International Wastewater Treatment Plant on previously disturbed slopes and pads along Monument Road and would be used in conjunction with Staging Area B for staging equipment and spoil materials. No excavation or grading would be necessary in this area. Routine maintenance activities will occur within the boundaries of the past approved maintenance areas and will not exceed the previously permitted/mitigated footprints of the Pilot 1 and Smuggler’s Gulch channels. Sensitive plant communities and established mitigation areas will be avoided.

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