Seawater desalination operator Poseidon is poised to take over the Agua Hedionda Lagoon maintenance dredging that has been done by local power companies since 1954.
Permits are being obtained for the work to begin in November or early December with expectations to finish by mid-April, said Poseidon Senior Vice President Peter MacLaggan at a meeting earlier this month of the Carlsbad Beach Preservation Commission.
Sand from the dredging will be spread north of the lagoon inlet for the first time in about five years, MacLaggan said. The last two times the lagoon was dredged, the sand only went south of the inlet to avoid the prevailing southward ocean currents that can carry sand from the north beach back into the lagoon.
However, recent sand surveys show the north beach area has been depleted of sand, and so it will be included in the distribution this year. A total of about 300,000 cubic yards of sediment will be removed from the outer lagoon, which is the basin between Carlsbad Boulevard and the railroad tracks.
Sand from the lagoon will be piped in a slurry under the Carlsbad Boulevard bridge and spread on the beach below the seawall from Pine Avenue south to the cliffs below the power plant, MacLaggan said.
Commission members asked about safety precautions for the project, noting that a woman sleeping on the beach was killed recently when she was run over by a piece of heavy machinery during the conclusion of a harbor dredging project in Oceanside.
Chairman Fred Briggs said he was allowed to walk "very close" to a working tractor on the beach the last time the Carlsbad lagoon was dredged, which was a concern.
"That sand can be very, very soft," Briggs said. "On several occasions, I've sunk in as far as my knees."
Monitors will be employed to watch the moving machinery, and access to the work area will be limited in Carlsbad, MacLaggan said.
"We share your concerns and will address them to the best of our ability," he said.
In addition to public safety, monitors will watch for signs of any sea turtles or grunion, the fish that spawn on the sand, during the dredging. Surveys will be done to monitor the effects on eel grass, a native plant, and to watch for any signs of taxifolia caulerpa, an invasive algae found in the lagoon in 2000 and eliminated only after a six-year, $7 million effort.
Poseidon operates the Carlsbad Desalination Plant, which uses the seawater intakes that formerly supplied seawater to the Encina power plant. San Diego Gas & Electric Co. built the power plant in the 1950s and the company and later Cabrillo Power, a subsidiary of NRG Energy, dredged the lagoon 30 times in 60 years, to keep it open for the power plant's once-through seawater cooling system.
The old power plant was replaced in 2018 by a new air-cooled plant that does not need the seawater system, and so Poseidon took over the lagoon maintenance.
Agua Hedionda is the only lagoon in San Diego County that hosts commercial and recreational activities including boating, kayaking, stand-up paddleboarding, the Hubb-SeaWorld Fish Hatchery, the Carlsbad Aquafarm, and the YMCA Aquatic Park.
This story originally appeared in San Diego Union-Tribune.
