Emergency Routine Maintenance at Damon 1 and Garnet 2 Channels

Emergency Routine Maintenance at Damon 1 and Garnet 2 Channels

Project Number: PRJ-1126940 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 of stormwater facilities in order to reduce and manage flood risk. City of San Diego Development Services Department approval of a Substantial Conformance Review (SCR) for City of San Diego maintenance activities at the Garnet 2 and Damon 1 channels. The project includes an after-the-fact SCR for emergency maintenance activities at the Garnet 2 and Damon 1 channels The project components are discussed below. Emergency Maintenance Activities: This project includes completed emergency maintenance and repair activities within the Garnet 2 and Damon 1 facilities which were authorized under Emergency ESL Approval No. PMT-3304128. The Garnet 2 and Damon 1 facilities were not originally identified and analyzed at the project-level in the MWMP EIR, and as such no Facility Maintenance Plan (FMP) was prepared for the facilities. Damon 1 is fully concrete-lined, and Garnet 2 is fully concrete-lined where it connects to Damon 1 before transitioning into a fully earthen channel. Emergency maintenance was limited to the fully concrete-lined portion of the Garnet 2 facility. A site evaluation of the Garnet 2 and Damon 1 facility segments was conducted by City engineers on January 24, 2024 to assess the levels of sediment, vegetation, and debris within the channels as a ~result of an intense storm and associated severe flooding that occurred on January 22, 2024. Due to impending conditions and precipitation forecast to provide upwards of 0.58 inches of rain beginning the morning of February 1, 2024, emergency actions were deemed necessary to ensure areas blocking downstream flows within the channels were cleared of deposited debris to alleviate the threat to life and property. Additionally, a secondary storm event, which occurred from February 1st through 9th and brought up to 1.04 Inches of precipitation. Due to the sudden nature of the emergency conditions, work was initiated as soon as possible at Garnet 2 and Damon 1 on March 29, 2024. This project involved the removal of material (i.e., vegetation, sediment, and debris) from the Garnet 2 and Damon 1 channels to alleviate the emergency conditions caused by the heavy rainfall at the end of January 2024. The channels are concrete-bottomed with concrete-lined banks throughout the emergency maintenance area. City of San Diego and contractor crews removed sediment, vegetation, and debris utilizing excavators, bulldozers, bobcats, front-end loaders, and dump trucks staged both within the channels and above the banks of the facilities. All material was hauled to an approved disposal location (Miramar Landfill). The emergency project removed approximately 10,923 cubic yards (CY) (16,385 tons) of accumulated sediment, vegetation, and debris from approximately 379 linear feet (LF) of the concrete-lined segment of Garnet 2 and 685 LF of the concrete-lined segment of Damon 1. The emergency work at Garnet 2 and Damon 1 was completed on May 19, 2024 and represented the minimum impacts necessary to alleviate the threat to life and property due to the unexpected flood risk.

San Diego

San Diego

Citywide, Southern California

San Diego