Sustainable Ocean Intake and Pumping Facility for the Carlsbad Desalination Plant

The Carlsbad Desalination Plant (CDP), a 50 MGD seawater desalination plant, was originally co-located with NRG’s Encina Power Station (EPS) and the feedwater was withdrawn from the EPS thermal effluent discharge tunnel. The EPS terminated operations in late 2018, which required the construction of a new feedwater intake and brine dilution discharge system to transition the CDP to long-term, stand-alone operation. The new feedwater intake system requires the CDP to become subject to the provisions of the California Ocean Plan Amendment (OPA). The primary OPA requirements protect fish by requiring intake approach and through screen velocities to be less than 0.5 foot per second (fps). To meet these constraints, more than 20 different concepts were developed. The selected design concept meets the OPA requirements in two construction phases due to the anticipated schedule delays from additional regulatory/permitting requirements for the marine construction components. Construction of the first phase of the selected concept, was completed in June 2020. The first phase allows continued pumping under existing permit conditions until sufficient design and permitting can be completed for facilities that meet OPA requirements. The second phase will be completed once the longer lead permits are obtained for construction within the Aqua Hedionda Lagoon (Lagoon). First phase construction utilized existing infrastructure and sustainable design to lower capital and annual costs to meet several difficult and conflicting project requirements. This document summarizes the challenges and unique design solutions that were implemented to comply with the Regional Water Quality Control Board’s (RWQCB) current interpretation of the OPA at the CDP intake structure.

This presentation is available to AMTA Members only.