Outfall Replacement under San Elijo Lagoon Marine Reserve

摘要

San Elijo Joint Powers Authority (SEJPA) is a wastewater/recycled water agency that manages the San Elijo Ocean Outfall System. The outfall system conveys up to 25.5 million gallons per day of treated wastewater from the cities of Encinitas, Escondido, Del Mar, and Solana Beach to the Pacific Ocean for disposal through a 1.5-mile ocean outfall. In 2015, a condition assessment study identified the ocean outfall system as critical infrastructure that would have immediate environmental and financial impacts if it were to fail. Furthermore, due to age and soil conditions, the lagoon section of the outfall system had the highest potential for failure and was reasonably considered at the end of its useful life.SEJPA selected Kennedy/Jenks Consultants to evaluate replacing or rehabilitating the lagoon section of the outfall. The predesign report evaluated open cut and trenchless installation, as well as rehabilitation methods. Horizontal directional drill (HDD) was selected as the preferred method due to reduced environmental impacts and the allowance to install the pipeline at greater depths to avoid conflicts with planned lagoon restoration work. The HDD length was approximately 2,600 linear feet with a bend radius of 1,000-feet, including horizontal and vertical curves. Due to environmental regulations, limited work was allowed within the lagoon and no geotechnical investigation permitted within its boundaries. Extensive project permitting and coordination was required with California Coastal Commission, California Fish and Wildlife, Army Core of Engineers, State Parks, Regional Water Board, and many others. The project was successfully completed in spring 2018.