For my birthday present, we toured Cargill Salt's San Francisco Bay Area salt works. It was terrific! K took the afternoon off work, and we drove to Redwood City after lunch. We thought traffic might be bad, but it wasn't, so we had lots of time to waste before the tour started. We ended up spending a lazy two hours drinking coffee, eating dessert, and browsing a gazillion pamphlets which I have collected over the past few months on all things touristy in the SF Bay Area and Northern California. Wow, is there a lot to do around here. But I digress. . . this is about Salt! I love salt! We seem to crave salt a lot, although we try to consume in moderation. In fact, M just discovered a Vietnamese dessert that is both salty and sweet all at once (very interesting sensation). . . but I digress again. So, we were really geeked about the salt ponds tour, since we have been wanting to visit salt marshes and mines ever since watching the History Channel's Modern Marvels: Salt Mines segment.
Once called Leslie Salt Company, it is now owned by Cargill Incorporated. We started the tour with an introduction to mega machines.
The salt harvester. It's a giant rototiller! Basically, it cuts up the salt using an auger, channeling it up into these chutes (below)
Trucks used to follow the harvester, collecting salt dumped from the chute.
A large piece of gypsum.Cargill's website has an education virtual tour which takes you through their process of collecting salt - The Outdoor Solar Plant. Water is collected from the bay and fed into ponds of varying concentrations.
An evaporation pond. As the brine becomes more concentrated (called "pickle"), it is drained into another pond closer to the harvesting site (so the salt actually comes to the harvester, rather than the harvested being driven out to the ponds). This is done using. . . Gravity! Ponds are inclined so that they drain to the next pond in the sequence (there is as much as a 1% grade). A slough gate, as seen above, is used to flood the salt pond.
Pickle is fed into these crystalizer ponds, where sun and wind will help dry up the ponds, leaving behind salt crystals. When NaCl forms, it "drops" out of the solution and builds from the bottom up. The ponds are only 1.5 feet deep. When salt has accumulated to a foot, it's harvested. This pond here will be ready for harvesting in a year's time.
This bed was recently harvested. That is mud on top of salt beds. Salt water is brought in again to "melt" what is left. Bittern is left, and is being exported to British Columbia where it's sprayed on construction sites for dust control. The process lasts about a month before they have to spray again. That's a great use of "left-overs".
A levy between two salt ponds.
The colors which we see are caused by microorganisms, and indicates the salinity of the ponds. Check out these amazing photographs of various Cargill salt ponds in the bay area.
We saw different types of salt formation.
A salt trail formed by water brought in to "melt" the salt. (Oh my gosh, don't ask me why it's not called "dissolving" the salt, but that's the term the engineer used!)
Pink salt
Another type of salt crystal
Columns of salt under the mud crust. These columns "drop" and form a bed of salt for harvesting.
Everyone has left but us! We were just a tad greedy and wanted to collect all kinds of samples to keep. On the way back to the bus, we took more pictures.
The company used to collect the salt using 30" narrow gauge railway.
Crystallizer ponds 
Another crystallizer pond - this will be ready for harvesting in 3 or 4 years' time.
Slough gate.
What looks like dots are columns of salt dropping.
We have not identified these hardy plants that live in the salt ponds, but I think the pickle weed (Batis maritima) is one of them.Cargill is in the process of closing down the Redwood City plant as it is no longer profitable. Land use studies are in progress, and it will be interesting to see what will be developed on these salt ponds in the future.
KQED's Quest: From Salt Ponds to Wetlands
You can also take a virtual tour of Cargill Salt's SF Bay Area salt works.
Unfortunately, it doesn't seem like salt pond tours for the public are currently offered, but we have since gone on other tours to learn about salt marsh restoration. The culture and history of the salt industry in Northern California is fascinating.
Good Eats episode:
Eat This Rock! (Specials)
The Ballad of Salty and Sweet
No comments:
Post a Comment