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Agua Hedionda Lagoon dredging plan presented to restore inlet, replenish beaches and support desalination plant
Summary
Channelside Water Resources and Anchor QEA presented a maintenance dredging and beach nourishment plan for Agua Hedionda Lagoon: a proposed neat-line dredge to -22 mean lower low water (about 400,000 cubic yards, plus contingency), a fall-to-spring tentative schedule, and extensive permit and monitoring requirements to protect habitat and public safety.
Representatives from Anchor QEA and Channelside Water Resources briefed the Beach Preservation Commission on June 4 about a planned maintenance dredging and beach-nourishment operation for Agua Hedionda Lagoon that would support the Claude "Bud" Lewis Carlsbad Desalination Plant and restore beach sand.
"This provides approximately 10% of San Diego County's water supplies and nearly 50,000,000 gallons of drinking water each day," said Dominic Massaro of Anchor QEA, describing why maintaining an open inlet is critical to the lagoon and the desalination intake.
Presenters said the dredge design calls for excavation to approximately -22 mean lower low water with a two-foot overdredge. The neat-line bathymetry survey from February produced a dredge estimate in the neighborhood of 400,000 cubic yards; staff included an additional contingency (roughly 50,000 cubic yards) to account for sand deposition between survey and construction. Similar maintenance dredging and beach nourishment operations have been performed in the lagoon periodically since 1959, with past dredge volumes ranging from about 159,000 to 429,000 cubic yards.
The tentative construction window described by presenters starts this fall with initial beach placement and continues into the winter and spring months, with beach work generally avoiding the April 15 to Sept. 15 high-use and bird-nesting season. Presenters stressed that start dates and volumes are permit-dependent and that a set of amendments and right-of-entry applications were being submitted this week.
Permit compliance and monitoring were emphasized. The sand deposition plan required by the city's special-use permit has been drafted and the project team reported sand-sample analyses are complete; a sand analysis report (SAR) and additional results will go to the dredge material management team on June 26. Presenters listed monitoring requirements that will accompany permits: pre- and post-construction eelgrass and habitat surveys, grunion-run monitoring, biological monitors for endangered species, Coastal Commission surf-monitoring protocols, and safety/perimeter plans for recreational access during construction.
Commissioners asked how dredge volumes are determined and whether dredging continues until a specific bottom elevation is reached; presenters said volumes are driven by the target dredge elevation and by observed deposition patterns and that operators dredge to the design depth. Commissioners also asked who is responsible for on-site monitoring and safety; staff and presenters said the operator is required to maintain continuous construction-zone monitoring under the State Parks right-of-entry permit while State Parks, city staff and resource agencies may perform periodic checks.
Commissioners urged more public outreach so residents understand where sand is coming from and when beaches will be replenished. Staff said they will work with communications and engagement to provide materials at upcoming cleanup events and on the city website and will report back with further updates.
Next steps: the project team will present the sand analysis report to the dredge-material team on June 26; permit approval is required before construction can begin and the operator's dredging operations plan will be reviewed as part of the contract and right-of-entry conditions.
