Floating Yellow Curtains

If you've seen one of our aerial photos of the Calaveras Dam Replacement Project, you might have noticed what look like yellow lines in the reservoir. Those are turbidity curtains. What's that?

We're glad you asked.  A turbidity curtain, also known as a silt curtain, is a floating barrier that collects suspended solids that are present in the water and allows them to settle in a contained area.

Calaveras Reservoir, and our turbidity curtains, are visible below.



Turbidity curtains are usually placed near areas were we have disturbed soil in or near the reservoir. The turbidity curtains act as a floating filter to protect the water around the outlet tower where we take water out of the reservoir. Although we filter this water at the nearby Sunol Valley Water Treatment Plant before we serve it to our customers, these curtains add an additional layer of protection to our water supply from any particulates or sediment from the Calaveras Dam Replacement Project.

The top of the curtain is made from a float from which a skirt hangs down. There are generally two types of turbidity curtains: hanging and standing silt curtains. At the Calaveras Dam Replacement Project we use hanging silt curtains.





Image curiosity of : https://www.landmsupplyco.com/

A close up of our turbidity curtains.

Turbidity curtains are an important part of the Calaveras Dam Replacement Project to continue to protect our our water sources during construction.

See you around the Valley!

Photo Friday - Morning Light

Happy Photo Friday

It's been a while since we posted any photos from Pat, one of our Watershed Keepers who helps look after our Alameda Watershed lands.

Recently Pat found himself at San Antonio Reservoir at sunrise and shared the moment with all of us. 

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

Alameda Whipsnake Sightings Near You

Here in the Sunol Valley we have a special species of snake that lives among us. It’s no other than the Alameda whipsnake or sometimes called the Alameda Striped Racer, (Masticophis lateralis euryxanthus), a subspecies of the California whipsnake (Masticophis lateralis). It has made the coastal scrub, chaparral, and grassland habitats in the hills east of the San Francisco Bay its habitat.

Known for its ability to move fast, the Alameda whipsnake has the following distinct features: broad head, large eyes and a long slender body with a distinct yellow-orange “racing stripe” down each side. Adults can grow to six feet long. They are diurnal which means that they are active mainly during the day. Surprisingly good climbers, these snakes seem to prefer to hunt for lizards, snakes, and frogs. They are not venomous and pose no threat to humans.

All of the workers on SFPUC-related construction projects in the Valley have been trained to be on the look out for these special snakes. If they see one, they stop what they're doing, and contact a trained biologist to rescue them to a safer location.



Here is an up and close picture of one rescued by our field biologist, Aaron.

November is the time of year when they look for a dry, safe burrow to hibernate during the winter. The springtime is when courtship and mating takes place, usually from late-March through mid-June.



Alameda whipsnakes are considered to be both a federally and state threatened species.









See you around the Valley!

Spraying it Green

Most of us don’t give hydroseeding much thought. As it turns out, we at the Calaveras Dam Replacement Project do.

Hydroseeding is, in essence, spreading seeds over an area after the ground has been disturbed by things like the construction of a large dam.  It is an important part of restoration and erosion control.  What is cool is the way we plant these seeds.  What we call hydroseeding was invented in the 1950's and involves mixing mulch, seed, and water together to form a slurry and then literally spraying it on the ground. This mixture increases the likelihood of germination of the plants and it holds firm to sloped areas.

One of the best times to hydroseed is the fall, which is why our teams are spending a lot of time hydroseeding now.  Our hydroseed is a mix of native annual and perennial grasses and forbs that grow quickly and easily from seed. The restoration goals for the project include establishing native plant communities. The vegetation provides habitat for threatened species and helps improve water quality.

Here is a beautiful picture of the recent hydroseeding of Borrow Area B (BAB). The green color is not green grass but a natural dye used so the contractor can track locations where they applied the hydroseed. The color will eventually disappear until the vegetation begins to grow. 






And, here is a picture of the newly hyroseeded dam. You can see the hydroseeder (truck) spraying the hydroseed onto the dam's face.  The thick lines are straw wattles used to prevent erosion on the slope.

Here is a closer picture of one of our workers spraying the hydroseed onto a steep slope.

Now we just need a nice winter's rain to help the hydroseed grow. 

See you around the Valley!

Calaveras Road Closure Extended until December 31, 2018

The Closure of Calaveras Road to through traffic between Milpitas and Sunol has been extended from Friday, November 2, 2018 to Monday, December 31, 2018.

The road will reopen to all traffic, weekdays, weekends, and holidays starting Tuesday, January 1, 2019.

Why:

SFPUC has completed the repairs to last winter’s landslide and we are now working to obtain the necessary approvals to open Calaveras road to the public.

Background:
We have been working since 2011 to replace the 93 year-old Calaveras Dam to increase the reliability of the Hetch Hetchy Regional Water System, which serves 2.7 million people in four Bay Area counties.

The closure of Calaveras Road began in July 2016 to protect public safety on the extremely narrow portions of Calaveras Road while large trucks utilized the road for construction.  

Road Closure Details:
Where: Calaveras Road just south of Geary Road (entrance to Sunol Regional Wilderness) to Oakridge Road near the Alameda /Santa Clara County line.

When: 

July, 2016 through December 31, 2018. The Road will be open on weekdays, weekends, and holidays starting Tuesday, January 1, 2019.

For more information, visit sfwater.org/calaverasroad

Thank you for your continued patience. We apologize for the inconvenience.

Love Your Local Stilling Basin

We have written a great deal about the spillway at the Calaveras Dam Replacement Project. Completed in 2016, this spillway is the width of a six lane freeway, and the height of a three-story building. The spillway's job is to protect Calaveras Dam by allowing water from Calaveras Reservoir to flow safely around, and away from, the dam in extreme high water events.

We have neglected to highlight an important component of a spillway - the stilling basin. Today, we'd like to generate a little love for stilling basins.  

A stilling basin is a structure that dissipates the energy of the water rushing down the spillway. Without a stilling basin, water coming out of the spillway could scour out the foundation of the dam, the base of the spillway, and nearby creek beds. In short, the stilling basin is a sort of bodyguard for the dam.

Stilling basins come in a variety of types, but generally fall into two categories: a straight drop for lower elevations, or an inclined chute. The stilling basin at the new Calaveras Dam is an example of the latter category. To be specific, it is a United States Bureau of Reclamation (USBR) Type II stilling basin.  Our stilling basin is approximately 200 feet long, 45 feet high and 80 feet wide.    

Water flowing down the new spillway of the new Calaveras Dam will drop 200 feet in elevation before it reaches the stilling basin at the bottom.The stilling basin creates a hydraulic jump to slow down the high velocity water before it slowly, and safely, discharges into Calaveras Creek.

A view of the new stilling basin at the Calaveras Dam Replacement Project

So, let's hear it for the humble stilling basin!

See you around the Valley! 

Loma Prieta Earthquake Anniversary Week - The New Irvington Tunnel

Happy Friday

This week marks the anniversary of the 1989 Loma Prieta Earthquake. 

We've been blogging about the San Francisco Public Utilities Commission's efforts to seismically upgrade our water system for many years now. The $4.8 billion Water System Improvement Program is more than 96% complete as of this writing. The water system that supplies water to 2.7 million customers in four Bay Area counties is much more earthquake ready today than it was 5 years ago. 

In honor of the Loma Prieta Anniversary week, we wanted to remember a post from October of 2013 when a crucial seismic project for the Water System Improvement Program achieved a huge milestone. Final hole through. 

Miners worked long hours in the New Irvington Tunnel .

The New Irvington Tunnel Project ,which went into service in February 2015, is a new 3.5 mile long seismically designed tunnel. We mined the tunnel from different directions, and the moment the two teams met underground to complete the digging is called Final Hole Through.

See the October 2013 Story here.

One of the three road headers that excavated the New Irvington Tunnel.

Have a great weekend, everyone.

See you around the Valley!