pahavit (pahavit) wrote,

Ravenswood Open Space Preserve

Ravenswood Open Space Preserve

They said Sunday was going to bring rain, so on Saturday D. and I slipped out of the house and went up to Ravenswood Open Space Preserve and its newly-restored salt marsh habitat, and I took some pics.

The section of the preserve we are visiting is right next to the Dumbarton Bridge, which is undergoing seismic retrofitting.


Giant potato-shaped birds, taller than humans!  AAAAAAAAAAAAAAAGH!  Run for your lives! But not before contacting the Resident Engineer first.

Dumbarton Bridge and old fishing pier, the latter of which used to be the original vehicle bridge across the Bay.

Someone fishing from the pier catches a small leopard shark as we walk beneath.

They throw the shark back into the water moments later.

A look toward the Bay from directly under the pier.

It's a popular place for paintballers, apparently.

Dumbarton Rail Bridge. Built in 1910, it has been unused since 1982.  It is a swing-type bridge, welded in the open position so ship traffic can pass at will.

A view to the south.

At the edge of the marsh, a milk snail nestles by a feathery sprig of fennel (both are non-native species but widely naturalized throughout the area).

As we round the other side of the bridge, we pass by more seismic retrofitting construction stuff.

A construction crane hook looks a bit like a beached whale at the side of the road.

Cargill still owns a tiny salt pond next to the highway; the rest of their ponds have been acquired by several local environmental, wildlife and water control agencies and converted into salt marsh, the largest tidal wetland restoration project on the West Coast.

Another look at the Dumbarton Bridge, dwarfing the fishing pier next to it.

An old sign in the salt marsh.

A view of the newly-created salt marsh at high tide, with nesting islands for migratory waterfowl and remnants of salt pond pilings still visible in the water.

All edumacational displays on the trail are bilingual.  Conceivably, one could learn Spanish from taking nature walks.

Por favor, clase, repita después de mí: Bienvendos a Estanque SF2, está aquí. ¡Muy bien, clase! Repita: ¿Por qué no hay plantas que crecen aquí?  Vi un ganso de Canadá.  ¡Muy bien!

A snowy egret by the side of the trail.

The trail, with a bench and some edumacational displays.

They are determined that we be edumacated, gosh darn it.

This is the inlet control structure, where Bay water enters the new salt marsh  ponds through five 48-inch diameter pipes.  Water flow through each pipe is controlled by a slide gate on the intake side of the vault and is prevented by a flap gate on the outlet side.

"Confined space" is a relative term.

The fence around the inlet control structure creates angular reflections.

The Bay side of the trail is lined with new plantings, encased in protective mesh for now.  Beyond the Dumbarton Rail Bridge is Mt. Umunhum on the horizon.

I don't think they have to worry about trespassers anymore, no matter what language they speak.

Your Ad Here.

Clase, ¿cómo se dice "long-billed curlew" en español?

Old salt pond pilings in the new marsh.

A horned grebe visits the marsh.

A levee leading into the nesting areas of the marsh is seriously off-limits to human visitors.

An egret stands among the cordgrass, looking for some lunch.

The outlet control structure for the new marsh.  The ebbing tide is designed to  flow out at a different place than the rising tide enters.

The force of the changing tide can be seen by this whirlpool at one of the pipes.

At times like this I almost wish I knew something about fluid dynamics, because it's kinda cool.

Canada geese on the trail ahead of us.

♪♫♪ You put your left foot in, you put your left foot out . . .  ♪♫♪

Looking almost like monochromatic stained glass, drying mud cracks and changes color at the edge of the Bay.

Ilyanassa obsoleta, the invasive, non-native Eastern mud snail.

Their siphons, looking like little snouts poking out of their shells, are prominent in these pics.  They draw in oxygen through the siphon while submerged and sense smells or tastes through its chemoreceptors.

Ilyanassa obsoleta is the most abundant snail on San Francisco Bay mudflats.  It feeds on diatoms and algal detritus on the surface of the mud and on tiny worms that live in the mud, and scavenges on dead fish, crabs and other animal remains.

It is eaten by ducks and the larger shorebirds, but not in large enough numbers to reduce its population.

Where it has been introduced in San Francisco Bay, it has forced out the native hornsnail Cerithidea californica and disrupted ecosystems.

Tidal flats that once housed diverse species of snails, worms and crustaceans are now monocultures of literally billions of Ilyanassa.  These pics show a mere few in one tiny area of mudflats.

An odd thing to find in the pickleweed at the edge of the Bay, a little plastic airplane.

The  Bay crossing of the Hetch Hetchy Aqueduct.  Officially, they are known as Bay Division Pipelines 1 and 2.  Pipeline 1 is a 60-inch diameter riveted steel pipe constructed in 1925. Pipeline 2 is a 66-inch diameter welded steel pipe constructed in 1936. These pipelines deliver water from Hetch Hetchy Reservoir in the Sierra to the San Francisco Bay Area. 

The aqueduct has been operating since 1934, delivering 239 million gallons of water daily to multiple San Francisco Bay Area cities.  A new 6-foot diameter pipeline is being built, and the leaky ones will likely be decommissioned when the new one is put into service.

Looking underneath the aqueduct, several other leaks can be seen splashing down into the Bay.

Here too, an eternal rain falls.

The pipeline.  It's showing its age.

Looking west along the pipe.

The pipeline is covered with lichen.  They grow in such fantastical shapes.

A section of the pipeline has ivy growing on it.  This is puzzling in the middle of a salt marsh, where non-salt-tolerant vegetation can't survive.

The reason for the ivy's survival becomes evident in a few more yards: another leak, splashing fresh water down into the ground.

I'd really like to know how many gallons of potable water are lost every day due to these leaks.

Gumplant, common in salt marshes.  The gummy resin on the flowers was used medicinally by the native Ohlone Indians.

More pipe ivy.

It's a really big pipe.

Looking back up the pipeline.  The superstructure is where it begins crossing the Bay.

Tracks in the mud.

Good thing it doesn't say "No Shooting."

Looking west along the pipes to the pump station building in the distance.

Gah, the lichen here makes it look like the pipe has a skin condition.  The corrosion doesn't help either.

Looking along the pipeline as it heads out over the Bay.

On the way back we see a northern harrier patrolling the marsh.

Whatever it is, it's sitting in the middle of the marsh within the high tide zone, it's padlocked, and it's been shot at. 

We see the Canada geese again, grazing in a field full of little flags and many sprinklers up on tall poles.

Passing by the outlet control structure again as the tide ebbs, revealing the pipes.

A snowy egret in the marsh, looking for a snack.

Tags: bird, canada goose, dumbarton bridge, eastern mud snail, fence, field trip, floof, ilyanassa, leopard shark, lichen, marsh, milk snail, mystery object, northern harrier, pickleweed, pipe, ravenswood, rust, salt pond, sign, snail, snowy egret

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