With the impending shutdown of the Cemex mine in Marina, USGS takes stock of the local sand supply.

With the Cemex sand mine on the beach in Marina slated to shut down by the end of 2020, the U.S. Geological Survey saw an opportunity for science: Gather data on how much sand was in southern Monterey Bay, both on the beach and under the water, and study how that changes over time.

Southern Monterey Bay has for years experienced one of the highest coastal erosion rates in the state, and scientists have long argued sand mining was to blame. Retired Naval Postgraduate School coastal engineer Ed Thornton, who championed the fight against the Cemex mine for decades, estimates that mine alone contributes to an average of 4 feet of coastal erosion annually from Marina to Monterey.

To better understand how the coastline might respond in the absence of sand mining, the USGS, from Sept. 12-14, conducted surveys along the coast with all-terrain vehicles and small watercraft to collect data on the contours and quantity of sand in the local coastal system.

“We decided it would be nice to have a baseline and look at the conditions of the beaches and near-shore, and when the [Cemex] plant is decommissioned, see how the coast responds,” says Patrick Barnard, a research geologist based in the USGS office in Santa Cruz.

Barnard says the long-term plan is to continue collecting the data once a year, but that more frequent assessments will be taken in the months before and after the mine shuts down.

The hope is to better understand how the mine closure will affect the local sand supply, which can inform long-term coastal infrastructure planning.

“Ultimately, our science is designed to support the public need,” Barnard says.