Lake Drive Storm Drain and Manchester Avenue Culvert Outfall Project

Lake Drive Storm Drain and Manchester Avenue Culvert Outfall Project

The City of Encinitas (City) proposes the Lake Drive Storm Drain and Manchester Avenue Culvert Outfall Project (project), which includes the processing of a design review permit, conditional use permit (major), and coastal development permit. The 25.32-acre Lake Drive site is located within an undeveloped canyon bounded by existing residential development to the north and east, I-5 to the west, and undeveloped open space to the south and west. The 0.14-acre Manchester Avenue site is located within City right-of-way adjacent to the San Elijo Lagoon Ecological Reserve, with residential uses to the north. The project sites are located within areas designated for residential, open space, and ecological reserve uses, and portions occur within the Multiple Habitat Conservation Program (MHCP) Focus Planning Area. The project involves the removal and replacement of a failing storm drain system extending from Lake Drive through an undeveloped canyon west to Interstate 5 (I-5), and maintenance improvements at the Manchester Avenue outfall that conveys stormwater to the San Elijo Lagoon. The existing 48-inch corrugated metal pipe (CMP) would be replaced with approximately 1,730 linear feet of new 48-inch reinforced concrete pipe (RCP) and associated appurtenances within the same general alignment to maintain existing drainage patterns and minimize disturbance. Project components at the Lake Drive site include installation of a new underground storm drain, construction of a permanent detention basin to reduce stormwater flow velocities, and a 25-footwide decomposed granite maintenance access road. The temporary high-line bypass piping currently installed under an emergency coastal development permit would be removed as part of this project. Following construction, the City will implement long-term operations and maintenance activities to ensure continued functionality of the drainage system and reduce flood risk to surrounding residences. At the Manchester Avenue site, the project includes periodic removal of accumulated sediment from the existing culvert outfall and J-Channel to restore conveyance capacity and protect downstream habitat within the San Elijo Lagoon Ecological Reserve. The Manchester Avenue site includes the existing storm drain outfall and adjacent J-Channel that convey stormwater from the upstream Lake Drive drainage system into the San Elijo Lagoon Ecological Reserve. Sediment removed during maintenance will be transported to an approved landfill or placed at a permitted beach location in coordination with the City’s Sand Compatibility and Opportunistic Use Program (SCOUP).

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