The San Elijo Land Outfall Replacement Project was successfully completed in June 2018 and utilized an innovative, and minimally disruptive, approach to successfully replace existing aging infrastructure.
The land outfall pipeline, managed by the San Elijo Joint Powers Authority (SEJPA), conveys up to 25 million gallons per day of treated wastewater from the cities of Encinitas, Solana Beach, Del Mar, and Escondido beneath the San Elijo Lagoon for ocean disposal approximately 1.5 miles from shore. The original pipeline was estimated to have reached the end of its useful life due to age and surrounding soil type. Since the San Elijo Lagoon has been designated as a marine reserve by the State of California due to its biological significance, failure of this pipeline would likely have had environmental and financial impacts. After an in-depth evaluation, horizontal directional drilling (HDD) of a new high-density polyethylene (HDPE) pipe 2,600 feet in length was selected as the preferred design/construction method as it offers four substantial benefits: 1) the least impact to the public and the environment; 2) a cost-effective solution; 3) a feasible permitting process; and 4) greatest compatibility with planned lagoon restoration work and railroad double tracking project. By drilling up to 70 feet underground and without the need for open cut trenching, the project protects the lagoon by avoiding disturbance to the lagoon area and its wildlife; requiring only a small staging area on the beach, leaving public beach access and the bike path open and useable for the duration of the project. While complex and with many jurisdictional agencies involved, the permitting process was facilitated by utilizing a trenchless construction method. Lastly, the selected pipe material, high density polyethylene (HDPE), and HDD installation method minimized conflicts with planned dredging and railroad construction within the lagoon and offers a robust service life of up to 100 years. The San Elijo Land Outfall Replacement Project is considered a great success in meeting the SEJPA’s strategic objectives of protecting the San Elijo Lagoon, continuing to provide reliable wastewater/recycled water service for the communities it serves with minimal environmental impacts, and promoting effective collaboration with area jurisdictional agencies.