Santa Cruz, Calif. (CN) — Residents of the Central Coast packed a California Coastal Commission meeting Wednesday to urge the state’s powerful regulator to shut down a sand mine that’s eroding the coast of Monterey Bay.

The monthly meeting of the California Coastal Commission, held in Santa Cruz on Wednesday, attracted dozens of residents who say the sand mine is accelerating erosion of the coast of Monterey Bay.

Cemex, a Mexican company, uses the sand in concrete. The sand mine is in Marina, a city of 21,000 on the southern end of Monterey Bay, just north of Monterey.

Anxiety about rising sea levels and increased erosion of California beaches due to climate change has brought the Cemex sand plant under scrutiny.

Residents complained in 2010 that Cemex was using bulldozers to push sand into a pit on the property, in violation of the Coastal Act, which prohibits use of heavy machinery without a permit.

The Coastal Commission began investigating in 2014 and in March this year sent Cemex a notice of intent to issue a cease and desist order — the opening salvo of a legal process that could end in the closure of the plant.

At the very least, the commission will ask Cemex to stop operating bulldozers and develop a plan to protect the dune habitat on the southern bay, according to the letter.

Though the sand mine opponents supported the commission at the Wednesday meeting, many were dismayed that though the notice of intent was issued in March, the commission has not sent the cease and desist order.

“Cemex has asked for multiple extensions and they have been granted,” said Ximena Waissbluth, chairwoman of the Monterey Chapter of the Surfrider Foundation. “Five months later, we are being directly affected by the diminishing coastline. I hope the last extension has been granted.”

Lisa Haage, chief of enforcement for the commission, said it was the enforcement division’s top priority and her department plans to meet with Cemex representatives as early as next week.

Commissioners declined to discuss the issue at length, saying they anticipate a meeting where they will have to decide the matter and do not want to prejudice themselves in advance.

A study conducted by Ed Thorton, a retired professor, shows the Cemex plant removes about 200,000 cubic yards of sand from the site each year. This results in an annual erosion rate of about 4.7 feet at Marina State Beach, according to the study.

That compares to 129,000 cubic yards removed in the 1970s, at which time the erosion rate was a foot per year.

“Southern Monterey Bay has the highest erosion rate in all of California,” Thorton said at the meeting. “This is an illegal exploitation of a natural resource that belongs to the public.”

A study conducted in 2012 by Alyssum Pohl and Lisa Johnston concluded that the Monterey Bay area may be suffering economic harm of $6 million a year, due to necessary construction of sea walls and loss of recreational value as beaches disappear due to the accelerated erosion.

The Coastal Commission has long acknowledged that the Cemex has operated the plant without appropriate permits, as it began operations before the 1976 Coastal Act. The commission said in its notice of intent letter that the cease and desist process is intended to bring the industrial operation into compliance with the law.

Whether that involves mitigation measures such as reducing the amount of sand taken from the site, prohibition of heavy equipment or outright closure of the plant remains to be seen.