Dredging & Mining

The Bay’s Floor

The Bay’s health isn’t just about water quality—the sand and mud that make up the Bay’s floor provide habitat for native wildlife, erosion control for our shoreline, channels for ships, and so much more.

But the Bay’s bottom faces threats that are invisible to most of us.

Sand Mining

Fresh sand washes down to the Bay from the upper reaches of the Sacramento-San Joaquin Delta. U.S. Geological Survey scientists have demonstrated that this sand would naturally flow to replenish Bay shoreline wetlands and go out the Golden Gate to replenish eroding shorelines like the one at San Francisco’s Ocean Beach. That is, if it weren’t being scooped up from the Bay floor by sand mining companies. The companies take this Bay sand, a finite resource, and sell it for a profit to make construction materials like cement and concrete. 

Sand miner with Golden Gate Bridge in background
A sand miner in the Bay making its way to the Golden Gate Bridge (Photo: Roger Cunningham)

Despite the evidence of potential harm to local beaches, the State Lands Commission approved a 50% increase in the amount of sand that could be removed from the Bay. Baykeeper challenged the State Lands Commission’s decision in court, and in 2016 the agency was ordered to reevaluate its approval.

In response, the agency conducted a perfunctory analysis and rubber-stamped new permits for the same harmful levels of sand mining. So Baykeeper filed a second lawsuit challenging the agency’s action. The San Francisco Bay Conservation and Development Commission (BCDC) agreed with us and required reductions.

The court rejected the state’s claim that private companies taking sand from the Bay benefits the public. Unfortunately, the court left it up to the agency to interpret the science and make a final decision about whether the current level of sand mining is harming public beaches.

There’s a lot at stake. Ocean Beach serves as a buffer between the Pacific Ocean and essential infrastructure like the Great Highway and San Francisco sewer lines. It’s also a very popular recreational spot for locals and tourists. And it provides vital habitat for native wildlife, like the threatened Snowy Plover.

As of 2024, the State Lands Commission has initiated an environmental review process for the next round of ten-year sand mining leases. Baykeeper will be watching this process closely to ensure our public trust resources are protected.

Companies take Bay sand, a finite resource, and sell it for a profit to make construction materials like cement and concrete.


Suction Dredging & Wildlife

San Francisco Bay is a dynamic and shallow water body that rapidly fills shipping lanes, marinas and harbors with sand, silt, and mud. Each year, the U.S. Army Corps of Engineers removes three to four million cubic yards of sand and mud—or enough to fill the Transamerica Building ten times—from the Bay floor.

The Army Corps does approximately 70% of this dredging to keep shipping channels and harbors deep enough to accommodate large ocean-going ships traveling to and from ports and shipping terminals around the Bay and farther up the Delta.

There are two main ways to dredge mud: hydraulic hopper suction dredging and clamshell dredging. Hydraulic suction dredging is incredibly harmful and should be immediately phased out—but, unfortunately, suction dredging is the Amy Corps’ dredging method of choice.

Snowy plover chicks on the beach
Snowy plovers are particularly vulnerable to disruptions to their sandy habitat (Photo: B. Casler/USFWS)

Hydraulic dredging kills large numbers of two Bay fish species that are on the brink of extinction, delta smelt, and longfin smelt. According to the Army Corps’ own analysis, their dredging killed up to 29% of the delta smelt population and 8% of the longfin smelt population. Baykeeper is pushing the agency to use another dredging method, where clamshell buckets scoop up mud and sand the way a backhoe would dig a pit, which is safer for fish. We’ve also requested a thorough assessment of the impacts of dredging on white sturgeon through the Endangered Species Act.

The Army Corps has initiated an environmental review process of their dredging practices, which Baykeeper is following closely.

Beneficial Reuse

Unfortunately, most of the material dredged from the Bay doesn’t go to good use. It’s dumped deep in the ocean—an outdated and wasteful disposal method.  Baykeeper has long advocated for permit improvements that require that clean sand and mud dredged up from the Bay be used to restore wetlands and protect shorelines from sea level rise.

Fossil Fuel Expansion   

In 2019, the US Army Corps of Engineers unveiled a plan to dredge a deeper shipping channel through San Francisco Bay to Stockton.

The project would primarily have benefitted oil refineries, since deeper channels allow refineries to load even larger oil tankers. The result would be even more oil on the Bay, a higher risk of spills locally. The plan could also have been the first step for the Port of Stockton to expand toxic coal exports through the Bay.

Baykeeper has long advocated for permit improvements that require that clean sand and mud dredged up from the Bay be used to restore wetlands and protect shorelines from sea level rise.

So we joined forces with a coalition of environmental and community organizations to challenge the proposal opposing the plan. And our efforts paid off! In 2020, the Army Corps announced that it was withdrawing its plans.

What Baykeeper is Doing

  • We’re currently participating on a technical advisory committee for sand mining and watchdogging the next permit cycle to make sure it’s more protective of the Bay. 
  • Through our appointment and participation on the San Francisco Bay Harbor Safety Committee, we keep an eye on future dredging proposals to be sure they’re not going to harm the Bay.
  • We’re standing members of the Long-Term Management Strategy for Sediment in the Bay to advocate for beneficial reuse of the Bay’s dredged sediment.
Clamshell dredger dredging in the Bay with harbor seals in foreground
Clamshell dredgers, like the one pictured here in Alameda, are much better for the Bay than the hydraulic suction dredgers that the Army Corps often uses
(Photo: Richard Bangert)