Friday, May 26, 2017

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!

Friday, May 19, 2017

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!

Friday, May 12, 2017

Photo Friday for the Birds

While this author spent time in the Sunol Valley this week, she spied an amazing bird. 

Sitting atop the construction fencing that keeps small (crawling) critters out of the construction site, was a bird with flaming yellow plumage accented with black.

This striking fellow (and yes it is a male, the females are much more subdued in color) is a Bullock's orioleThe Alameda Watershed is home from spring through summer to Bullock’s orioles, like this first-year male. They'll winter in Mexico or Central America before migrating north again next spring.

They dine on insects, fruit, and raid the occasional humming bird feeder for the nectar. 

See you around the Valley!

Thursday, May 4, 2017

Honoring Construction Safety Week in the Sunol Valley

With so much heavy construction work underway in the Sunol Valley, it is easy to forget that the men and women in the construction industry perform dangerous work often in difficult conditions to upgrade the Hetch Hetchy Regional Water System.

It is a good thing that the construction teams working on the two projects in full swing in the Sunol Valley keep safety in mind every single day.  However, this week was a little different. The teams at the Calaveras Dam Replacement Project and the Fish Passage Facilities within the Alameda Creek Watershed underwent additional trainings and reminders this week.


The first week of May is National Construction Safety Week.  Global construction industry leaders, including our contractors, joined together to form industry safety forums and an initiative called ‘Safety Week.’ The mission of Safety week is to raise awareness within the construction industry ensuring “We are Stronger and Safer Together.”

How strong?

Here in the Sunol Valley, the number of recordable workplace incidents is well below the industry average. At our Fish Passage Project, workers have clocked in over 70,000 work hours since April 2016 with zero recordable incidents.  At the Calaveras Dam Project, the largest project in the Water System Improvement Program has worked over 220,000 work hours since July 2016 with zero recordable incidents. 

Working in heat and rain, on large earth-moving equipment or in tight spaces next to a creek, our crews are showing that every week is safety week.

We are proud of our teams out in Sunol Valley! Stay safe out there.

Crews overseeing operations at the future Fish Passage Facilities

Center of photo shows construction crews at Calaveras Dam placing
Clay Core materials in the replacement dam at elevation 567 ft