South Bay salt ponds restored to tidal waters
By Lauren McSherry, Town Crier Staff Writer
 Briggs Nisbet, Save the Bay restoration campaigns manager, looks out at the salt ponds beyond Moffett Field’s superfund cleanup site. |
Just about anyone who has taken a flight out of an airport in the Bay Area and glanced out a plane window has seen them. Thousands of feet beneath a plane, the salt ponds look like patches of bright red in a mosaic of levees, highways, industrial parks and residential neighborhoods that make up much of Silicon Valley - all in close proximity to the blue waters of the San Francisco Bay.
The salt ponds, which ring the entire South Bay, from the San Mateo Bridge on down, get their unique coloring from the evaporation process of salt making. Red ponds have the highest salinity levels compared to dark blue or aquamarine salt ponds.
Recently, a coalition of government agencies and environmental groups embarked on a project to restore the ponds, once owned and operated by the agricultural giant Cargill, which still operates about 10,000 acres of salt ponds in the Bay.
The project, estimated to take 30 years and up to $1 billion, is the largest restoration project in the West and ranks third largest in the nation, behind the restoration projects of the Florida Everglades and the Mississippi River.
In Mountain View, the salt ponds that Stevens Creek empties into along Shoreline Park have been undergoing restoration, and 250 acres of ponds that belong to the U.S. Navy near Moffett Field and another 55 acres owned by the Midpeninsula Regional Open Space District could also be slated for restoration in the near future. The Moffett Field ponds, called Site 25, were used to collect storm water, not to produce salt, although they are next to salt ponds and provide habitat for birds.
Teeming wetlands
Each year millions of birds come through the Bay Area, a major stop on the Pacific Flyway. Other animals call the South Bay home year round, such as hawks, great blue herons, snowy egrets and even the endangered salt marsh harvest mouse. Steelhead and Chinook salmon also live in the Bay.
Around the mouth of Stevens Creek at Shoreline Preserve, tidal marshland has returned to some former salt ponds. At one time the area was a wilderness of water and grasses; with tidal wetlands stretching as far as the eye could see. Before it was channelized in the early 1900s, Stevens Creek would have meandered through willow groves near Rengstorff Avenue before sweeping through tidal grasslands into the Bay.
Today, Shoreline’s pathways, built on top of levees, skirt the salt ponds, some of which have been restored. Gates allow tides to flow through the levees, which form the ponds. Some gates have been opened, thus flushing the ponds and bringing salt levels back to normal. With the return of the natural tidal cycle have also come the grasses and shrubs endemic to the area.
Since many birds that have lost habitat in the Central Valley now rely on the algae, microbes and brine shrimp that thrive in the salt ponds, some of the ponds will remain as they are as part of the project.
Challenges ahead
The return of Bay waters to the ponds has raised concern among some environmentalists and scientists. Constructed in the 1850s and ’60s, the salt ponds were saved from being contaminated by mercury, which leached down from the Sierra Mountains during the Gold Rush.
“We don’t really know what’s going to happen,” said Briggs Nisbet, restoration campaigns manager for Save the Bay, one of the organizations spearheading the project. “We know that when the Bay water returns to the salt ponds it will probably carry mercury with it.”
It will take more than 100 years for all the mercury to flow out of the Bay into the Pacific Ocean through the Golden Gate, she added.
Cleaning up Moffett
For nearly six years Save the Bay has been campaigning to clean up the Moffett ponds, which are part of the Stevens Creek estuary.
Looking out at Site 25 from one of Shoreline’s paths, Nisbet commented that the South Bay restoration is unlike any other projects of this scope.
“What’s different about this is that it’s not out there. It’s in an urban area right here,” she said.
It is estimated that the Site 25 restoration could cost $2 million to $10 million and take about a year to remove contaminated sediments, which would need to be trucked offsite. Thus far, the Navy has spent approximately $90 million on Moffett Field cleanup.
