San Clemente reviews plan to core offshore sand deposits as city seeks local sources for beach nourishment

San Clemente city officials received a technical update April 15 on an offshore sand‑source investigation intended to identify borrow sites for future beach nourishment.

Coastal Frontiers principal Greg Herron told the City Council the project will start with a screening‑level VibraCore program to collect two to three 4‑inch diameter cores per candidate site, evaluate them in the field, then expand sampling at the most promising sites. “Wewant to be between water depths of about 35 and 60 feet,” Herron said, and to find deposits at least 10 feet thick that match local beach grain size. He described a seven‑day coring plan, targeting August–September to avoid weather downtime.

The update summarized 11–13 candidate borrow sites between Surfside Sunset and the Santa Margarita River. Herron said the Army Corps of Engineers' prior geophysical surveys and coring indicate a low probability of finding suitable sand immediately offshore of San Clemente, but the reward would be large if a nearby deposit is found because it would reduce project cost and complexity. “We think there's a low probability of finding sand offshore at these locations because of those studies,” he said, but added the city had directed consultants to "turn over every stone as close to the city as possible." Herron said Surfside Sunset has a relatively high probability of good sand based on prior dredging history.

Staff said two permits must be in place before coring: a California State Lands Commission geologic sampling permit (currently planned for the commission's June agenda) and agency review of the sampling and analysis plan by the Southern California Dredged Material Management team. If permits are granted, the consultant will perform VibraCore sampling in August–September and produce a testing and compatibility report and final report by year end. If cores show a promising site, Herron said the team would sit on that site to collect about 10 cores for characterization; if not, it would move to the next candidate or to sites farther north in Orange County.

Council members questioned why the new work might find material the Army Corps did not and whether funds would cover farther sites. Herron and staff responded that earlier Corps work was relied on for site selection and that the cityis balancing the low probability of nearby sand against the large cost savings if sand is found close in. Staff said OCTA has signaled willingness to expand the field program if it pays for additional days; the city is seeking outside funding for any expansion.

The city will proceed with permit applications and the sampling and analysis plan; the consultant said it could give an initial indication of whether a promising site was found within days of completing the field work.