Meet the CAT-773

Our work at the Calaveras Dam Replacement Project wouldn’t be possible without the help of heavy equipment. Heavy equipment helps our team complete big tasks like moving 12 million cubic yards of rock and earth. Because of the size and scope of our project, we have the privilege of working with some big and cool heavy equipment on our job site.

On any given day we could have approximately 20 pieces of heavy equipment operating. Today I would like to introduce you to the CAT-773

Here is a picture of some of our equipment.

With a full load it can carry 100 tons of dirt or 200,000 pounds of material. This machine can climb steep roads and is very comfortable for the operator. It has a 12-cylinder engine that can reach 42 miles an hour.

John Rocca, Field Operations Manager in front of a CAT-773.

It’s a real life Tonka truck. We have a total of 10 CAT-773’s on site hauling material and getting the job done.

 This equipment belongs to our Joint Venture (Dragados, Sukut and Flatiron), our partners on this project.

See you around the Valley!

What's the Big Deal about an Approach Channel?

We are building a new earth and rock fill Calaveras Dam right next to the existing 93 year-old dam (directly downstream of the existing dam as they say in the dam industry.)  As many of our previous blog posts have been tracking, we have been busy building the new dam, foot by foot, from the bottom up like a layer cake. A very large layer cake.

Our Calaveras cake is high enough now to allow us to begin to excavate out the approach channel to the new dam this week.

"What is an approach channel?" you ask. An approach channel is a breaching of an existing dam in order for its adjacent reservoir to come in contact with it. We will remove a portion of the existing dam (500,000 cubic yards of it to be exact) to allow reservoir water to eventually fill in the space between the old dam and the new dam. The old dam will look like a peninsula in the reservoir when the project is done. 

"Why not remove the old dam in its entirety?" We don't have to. Complete removal would be expensive, environmentally difficult, and not necessary to operate the reservoir. 

The start of excavation of the approach channel means that we have reached a high enough elevation with the new dam to safely begin carving out a huge chunk of the existing dam. It's a coming of age for the new dam, if you will. A significant milestone. 

Here is what the approach channel looked like at the beginning of last week.



And, here is what it looks like this week.




The channel will be lined with large rocks called rip rap to protect it from erosion so the channel will be ready when we start to refill the reservoir this fall.

Approach channels may not seem exciting at first glance, but we at the SFPUC are thrilled!

See you around the valley!

Sometimes Construction Methods Don't Change

Image courtesy of https://auto.howstuffworks.com/horsepower.htm

(place image here)

The photo below was taken in 1918-- when the first Calaveras Dam was being constructed.  These workers are excavating in the dam's foundation.  They're using using 4-mule carriages(4-horsepower) to do the job. Each power train (4-mule carriages) transport approximately 4 cubic yards per load at a speed of 1 to 2 mph. 

Fast forward a hundred years.  The photo below was taken at the new Calaveras Dam as workers were excavating the new core.  The workers in this photo are doing the same job with a Caterpillar Motor Scraper with a 450 horse power engine capable of carrying 30 cubic yards at a speed of 25 to 30 mph.

Although times have changed, sometimes the methods don't.  

See you around the valley!

Blankets and Curtains for Calaveras Dam?

Here at the Calaveras Dam Replacement Project we are building what is called an earth and rock-fill dam. The replacement Calaveras Dam, like all so-called embankment dams, is made of mostly compacted earth (see a cross section of the future dam below). An important aspect of this type of dam is the management of water. All earthen dams leak, the important thing is to control where the water flows to protect the integrity of your dam.  In the case of the Calaveras Dam Replacement project, we accomplish this with blankets and curtains. 

No fooling! Here’s how it works.  For years, the crews onsite have been constructing an entire dam that extends more than 100 feet below the base of the future dam.  We call this a grout curtain. Grout for those of you not in the construction industry is a special mix of cement that can be injected or literally blown onto a surface to seal it.  

Grout Curtains

As you can see in the photo from 2015, crews drilled countless small diameter holes into the bedrock a hundred feet down below the future dam and injected the holes with pressurized grout. The grout effectively seals up cracks and fractures within the rock underneath the new dam.  We did this for years. Why is this grout curtain so important? It prevents water from seeping underneath the new dam and undermining it.  In essence we drilled an entire new dam underneath the future dam. 

Drainage Blanket

If you thought grout curtains alone were enough to protect the future Calaveras Dam, guess again! We need blankets, too. More specifically a drainage blanket. The drainage blanket prevents water from exiting to, and damaging, the down-stream face of the dam (the face of the dam away from the reservoir).  At the end of the drainage blanket we are constructing a ‘mini dam’ made out of the same clay material as the core to capture any water in the drainage blanket. You can see the drainage blanket being constructed here.  This ‘mini dam’ is also known as the seepage barrier.  This seepage water is then collected in an inspection well to monitor the condition of the dam.

The Calaveras Dam Replacement Project, along with its blankets and curtains, is more than 80% complete.

See you around the Valley!

Photo Friday at the Calaveras Dam Replacement Project

Did you ever look at a photo of yourself or a family member from a long time ago and compare it to a recent picture? For today’s Photo Friday, we decided to do just that for the Calaveras Dam and its replacement.

Calaveras Dam in 2011. The project groundbreaking was in 2011. 

Calaveras Dam in April 2017. The project is more than 80% complete. We have moved more than 8 million cubic yards of rock and soil to date. We have fully excavated and grouted the left and right abutments. And in the center of the picture, the core of the new Calaveras Dam begins to take shape.  The huge concrete spillway (as wide as a freeway) is visible at the lower right. Wow.

Construction on this project started in 2011 and is expected to be complete in April 2019.

To learn more about this project and see a time lapse video of all of this excavation, visit us here.  

See you around the Valley!