Friday, September 22, 2017

Photo Friday at the Arroyo Hondo

Happy Photo Friday!

Today's post comes courtesy of watershed keeper Pat Jones.

Recently cloudy skies helped produce some stunning photos. This one shows Calaveras Reservoir and a major tributary into it - the Arroyo Hondo.

Have a great weekend, and we'll see you around the Valley!

Friday, September 15, 2017

Meet Sunol Valley's Natural Garbage Collectors

This week we wanted to highlight some special local inhabitants - turkey vultures.  If you drive anywhere in the Sunol Valley, you will almost always spot a committee of vultures waiting to see what their next meal will be. 

Turkey vultures, like this one spotted near Calaveras Reservoir, like to roost in bare trees to keep an eye (and nose) out for their next meal.

Turkey vultures, also known as turkey buzzards, are the most widespread species of vulture in the New World. They are so named because of their resemblance to the male wild turkey. Their range spreads from Canada all the way to the southernmost tip of South America. We call them nature’s garbage collectors because they feed almost exclusively on carrion and perform a crucial natural function of picking clean disease carrying carcasses.

Vultures are probably one of the most misunderstood birds in the animal kingdom. Here are some fun facts about these creatures:

  • Turkey vultures have one of the best senses of smell in the animal kingdom.
  • It's a misconception that they actually prefer their food rotten.  However, vultures do have a cool adaptation; their stomach acid is almost comparable to battery acid.
  • Nothing goes to waste with a vulture. They even make good use of semi-digested and digested food.

Photo courtesy of WikiCommons

Although few people would call them cute, they do perform a crucial role in natural areas like the Sunol Valley. 

See you around the valley!

Friday, September 8, 2017

The Building Blocks of the Replacement Calaveras Dam

If you are new to the world of dam construction, you might wonder what types of materials are used in building one.  Today’s blog will focus on what types of materials we are using to construct the new Calaveras Dam. Calaveras Dam is an earth embankment dam.  Earth embankment dams tend to be constructed of all types of geologic materials.

Calaveras Dam, July 2017
The picture above was taken recently; from it you can visually see the different materials. Let’s start with the middle and the most important material used in our dam, the core. 

The Core of Calaveras Dam

Zone 1 & 1A—aka…the Core
The core is made up of clay.  Clay is very dense and less permeable than most materials.  Our new dam will have a large core, which will help ensure that the dam withstands a 7.2 magnitude earthquake.  The clay used in our dam has been ‘borrowed’ from the south end of Calaveras Reservoir.

The core is taking shape.

Zone 1A- Core’s foundation
At the bottom of the core, you will find Zone 1A material. This clay is plastic, pliable clay, or another words, clay that has a Play-dohtm like consistency.   Zone 1A material is placed on the foundation’s bedrock and acts as a seal against water flow beneath the dam.

The core is the most important element of the dam and therefore must be protected.  We protect our core by using filters in both the upstream (reservoir side) and the downstream (dry side) of the dam to control the seepage of water and remove it safely from the Dam.

Zone 2 and 2A- Sand
Upstream zones are made of sand  (Zone 2A) and large gravel (Zone 5A)The downstream filters or chimneys are made of sand (Zone 2) and pea gravel (Zone 3).

Zone 5-Rock Fill
Further protection for both the core and filters is provided by rockfill shells. The upstream shell consists of hard durable rock because it will be submerged in the reservoir, Zone 5 material.  This material consists of metamorphic rock known as blue schist.

The downstream shell (Zone 4) consists of onsite material from a geologic formation known as Temblor Sandstone.  While this is a sedimentary rock, it tends to degrade into a gravelly, sandy soil and is best suited for drier conditions than the upstream shell.

Zone 6- Rip Rap
Wave action in the reservoir due to wind can erode most earthen materials.  Large durable rocks are placed on the slopes of the dam at the waterline to prevent this erosion. This is Zone 6 also known as rip rap.

Image courtesy of

See you around the valley!

Friday, September 1, 2017

What is a desmostylus and what is it doing in the Sunol Valley?

Photo courtesy of

A Desmostylus was a hippo-like creature that lived about 20 million years ago. It happens to be the only order of marine mammal to have gone extinct. Some individuals lived along the shoreline of an ancient ocean that used to be located where the Sunol Valley is today.

If you stumbled upon this would you know it was a rib cage?  What it looked like prior to Excavation

During excavation of the Calaveras Dam Replacement Project, the project paleontologists found not only a few teeth belonging to these strange creatures, but recently found an entire rib cage. Removing the fossilized rib cage of an animal that likely weighed between 200 and 400 pounds in life is no small task.

First the bone had to be cleaned and separated as much as possible from the surrounding rock on the hillside.

Above is the picture after our fossil was cleaned and ready to be removed.

In order to physically remove it from the hillside, crews used a lift to grab the entire rib cage. Now that the rib cage has been safely removed from the construction site, it awaits further stabilization treatment by project paleontologists. 

See you around the Valley!