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Salt Ponds in San Francisco Bay
The Cargill salt ponds are located in San Francisco Bay near the cities of Newark, Redwood City and Napa. The Napa operation was closed approximately ten years ago, and the
ponds are slowly reverting to a natural state. Anyone who has looked out the window of an airliner approaching San Francisco International Airport on a clear day has seen this multi-colored pallette in
the South Bay. This is where Leslie brand table salt is produced.
I first noticed these ponds when I was learning to fly in the mid 1960s. The geometric patterns provided good reference points for practicing certain required aerial
maneuvers. Several years later, when I was studying photography at San Francisco State College, I began photographing the ponds. I was fascinated by the combination of the abstract and the real -- it was
Diebencorn with a drawbridge, Thiebaud with a transmission tower or Pollock with a powerline.
Over the years, I spent many hours turning circles over the area and have a large portfolio of salt pond images. The area is constantly changing -- with the seasons; with
the weather and with the age of the ponds. Each time I visit the area, I discover something new.
The colors which fascinated me are created by algae, minerals, micro-organisms and brine shrimp. Water is drawn out of the ponds through natural evaporation, and during the
five years it takes for the bay water to mature into salt brine, it is pumped from one evaporation pond to another.
In the final stages, when the brine is fully saturated, the remaining water is pumped from the pond and a bed of salt 5 to 8 inches thick is ready for harvest.
The palette of colors that makes the salt ponds so beautiful is created by a complex ecosystem. The colors range from pale green through deep coral pink to bright red. The
color indicates the salinity of the ponds.
Micro-organisms change their hues as the salinity of the pond increases. In low to mid-salinity ponds, green algae is predominant, giving the water a deep greenish cast. As
the salinity continues to build up, an algae called Dunaliella shifts the color to a lighter shade of green.
In middle to high salinity ponds, the Dunaliella produces a red pigment. Millions of tiny brine shrimp lend an orange cast to the water in mid-salinity ponds. Salt loving
bacteria such as Stichococcus also contribute red tints to high salinity brine.
These ponds and the marshes that surround them are important habitat for more than 70 species of birds, including several endangered species. There is a proposal to return
this area to a more natural state as mitigation for the filling of part of San Francisco bay for two new runways at San Francisco International Airport.
For more information, visit: http://www.cargillsalt.com/sfbay/index.html
Robert Campbell
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