Friday, December 29, 2017

Happy New Year Photo Friday: A Year's Work

The start of any new year is a good time for reflection. For us here at the Calaveras Dam Replacement Project, we are reflecting on how much progress we have made in 2017. Below are two pictures of our project, one at the beginning of the year and one taken a couple weeks ago.

Calaveras Dam at the beginning of 2017:

We were months into building the dam itself, and the foundation, and outlet pipeline are still above ground.

Calaveras Dam in late 2017:

As you can see from the picture above, we made tremendous progress on construction of the replacement dam itself. The team is more than half way up with the building of the replacement dam, whose final grade you can see rising up more than 110 feet. The foundation and outlet pipe are completely buried now under the new dam.

To date, our project is 89% complete. Our New Year's goal is to have the entire project completed by mid-2019.

From all of us, we wish you and yours a Happy New Year!

See you around the valley!

Wednesday, December 27, 2017

Photo Tuesday at Sunol Valley Yard

Photo Tuesday at the Sunol CorporationYard

Today's post is about the SFPUC's Sunol Corporation Yard, which is located near the Sunol Water Temple.  In the last year, we have been constructing badly-needed upgrades to the Corporation Yard that is home to our Water Supply and Treatment East Bay operations and our Natural Resources personnel. 

Here are some photos of our progress.

Shop #5 will house plumbing and electrical supplies

Iron workers at the job site

The Sunol Yard Long-Term Improvements are expected to be completed by the end of 2018.  During construction, the Sunol Water Temple will be closed to the general public.

We hope you are having a wonderful Holiday Season.

See you around the Valley!

Friday, December 15, 2017

Piezometers and Inclinometers - Part 2

Piezometers and Inclinometers

This week’s blog is Part 2 of our instrumentation series. Piezometers and inclinometers are two types of internal instruments used to measure a dam’s movements. Both of these instruments will be installed in the new Calaveras dam.


A piezometer is an instrument that monitors the ground water through the dam’s core and into the downstream drainage blanket and downstream rock/soil shell. A piezometer helps to ensure that the ground water surface does not erode the toe of the dam (the bottom downstream part of the dam). It also helps track the water level in the underline bedrock foundation.

How Piezometers Work

An open stand-pipe piezometer is an open pipe (see picture above) that permits water to enter. The water level is measured and compared to other piezometers surrounding the dam’s face. These types of piezometers are called open-stand piezometers. We also have automated piezometers called Vibrating Wire Piezometers (VWP’s). VWP’s are data collection devices. We will have a total of 17 VWP’s and 14 open-stand pipe piezometers at Calaveras Dam.

Image curteosy of


An inclinometer is an instrument that measures the movement of a slope with respect to gravity. Slopes on dams are built to be stable but still need to be monitored for possible movements. Inclinometers verify the stability of dams, dam abutments (sides) and upstream slopes during and after a reservoir filling.

How Inclinometers Work

Inclinometers measure the orientation angle of an object with respect to the force of gravity. This is done by means of an accelerometer, which monitors the effect of gravity on a tiny mass suspended in an elastic support structure. When the device tilts, this mass will move slightly, causing a change of electrical charge between the mass and the supporting structure. The tilt angle is calculated from the measured electrical charge. You will always find inclinometers in pairs or sometimes in 3’s. Two inclinometers placed at Calaveras Dam.

Image curtesy of

Piezometers and inclinometers will play an important role in Calaveras. Once they are placed, they will need to be monitored and observed on a frequent basis.

See you around the valley!

Friday, December 8, 2017

Calaveras Road Closure Extended to September 30, 2018

The closure of Calaveras Road to thru traffic between Milpitas and Sunol has been extended to September 30, 2018. The road has been closed on weekends and holidays because of a land slide that undermined the road within the closure section. 

We anticipate the road to reopen on weekends sometime in 2018. Please check our website at for current information regarding the closure and for upcoming information regarding the reopening of the road during the weekends.

Once complete, the Calaveras Dam Replacement Project will increase the reliability of the water supply for East Bay residents and businesses.

We sincerely apologize for any inconvenience this may cause you and greatly appreciate your patience and support as we upgrade the regional water system.

If you have any further questions, feel free to call our toll-free 24 hour answer line at (866)-973-1476. Email us at: or

See you around the valley!

Tuesday, November 21, 2017

Happy Thanksgiving!

Wild turkeys at the entrance of Calaveras Road

Happy Thanksgiving! For this special edition of our blog, I asked a few of my colleagues what they’re thankful for as it relates to their work at Calaveras Dam.

Here’s what they said:

I’m thankful for kind and caring coworkers. I’m thankful for good relationships between the contractor and the City. The whole team makes coming to work easy. –JT Munchin-Mates, Environmental Compliance Manger

I am thankful for the opportunity to with an awesome team. –Ritu G. Giri, Senior Engineer-Piping & Pipeline

I’m thankful for the different people I get to collaborate with. We all have different stories and it’s great that we can share and be a team. –Minh Nguyen, QA Inspector

I’m thankful for the memorable quotes that keep our meetings interesting and lighthearted. (1) ‘Where’s the topsoil?’ ‘We moved it.’ (2) ‘This is 5I? What have you done to it?’ (3) ‘It’s pooching out.’ (4) ‘This road is seldom used and moss has grown over it.’ (5) ‘There’s rock in the creek. I’ve seen it.’ (6) ‘C’mon man! You’re losing the focus.’” –Tedman Lee, Civil Engineer

I am thankful to work with intelligent, energetic, and supportive people that are dedicated to the work that they do. It’s also an added bonus to work in an environment where my colleagues make me smile and laugh. –Olivia Nunez, Communications Liaison

I am thankful for the many friends I’ve made during my time here and how we take care of each other and help each other out in our times of need. ☺—Wendie Busbie, Office Manager

As an engineering geologist, I am thankful for the opportunity to work on a major infrastructure project in such an interesting geologic setting, from the beginning of the design phase site investigations through construction. –Phil Respess, Senior Project Engineering Geologist

I am thankful that the Construction Management Team and the Joint Venture are communicative. Whether in the field or back at the office, maintaining an open line of communication is critical for both safety and efficiency and when an issues arises, the solution becomes a productive dialogue rather than a reproachful lecture. –Bill Stagnaro, Environmental Inspector

I am thankful for a great job and a supportive boss. – Jason Lau, FCA Assistant

I am thankful for the opportunity to be involved with the CDRP project. It is a special and challenging project that is highly educational and memorable. I am also thankful to be working with the project team. The staff from both the JV and CM Team are very competent, professional, and a pleasure to work with. –James Sakai, Project Engineer

This year, I am very grateful to be able to work with all of you in the Sunol Valley.  All your commitment, dedication, talent and hardwork have helped to make very good progress on all the Sunol Projects.  I am so thankful for all your contributions.  Wish you all have a Happy Thanksgiving with families and friends!–Susan Hou, East Bay Regional Project Manager

See you around the valley!

Tuesday, November 7, 2017

External Instrumentation at Calaveras Dam

Typical survey monument

The old and replacement Calaveras Dams are located approximately 1,500 feet from the Calaveras Fault.  This means that we need to make sure that there are devices in place to monitor the movements of both the current and future dams and the area around them. 

The future Calaveras Dam will have a total of seven types of instruments inside it and around it.  Today I will focus only on two types of external instruments that will be placed at Calaveras Dam to help us monitor and protect it -- survey monument and accelerographs.

 I will explain the purpose of each and the role each device plays at Calaveras Dam. 

Survey Monuments

Survey monuments are placed both around the exterior of a dam and later will be placed on the surface of the dam.  They are monitored periodically to determine if they have moved from previous measurements, which would indicate any significant movement of the ground surface has occurred. Survey monuments also track the change in elevation of the ground surface, allowing us to determine the settlement of the new dam embankment. Some of the survey monuments placed at Calaveras Dam have survey prisms permitting the monitoring to be done remotely using a digital theodolite (aka total station).   We will have a total of 65 survey monuments at Calaveras Dam.  

 Survey Monument with Optical prism


Accelerographs are used to detect strong acceleration of the ground due to seismic forces. Accelerographs record the acceleration of the ground with respect to time. An Accelerograph is different than a seismograph. The difference is that an accelerograph doesn’t start working until something moves it.  A seismograph is recording continuously.  An accelerograph is a recorder that uses an accelerometer. Accelerometers are much less sensitive than seismometers, but have a much greater range. There will be 4 accelerographs installed around the new Calaveras Dam. 

These features are just some of the ways in which we are ensuring that the new Calaveras Dam serves our current and future generations of customers.

See you around the Valley!

Monday, October 30, 2017

Creepy Tarantulas and Tarantula Hawks

This week’s blog is about one of Sunol’s creepy crawlers—the tarantula. It lurks in the dark and doesn’t come out until October. It’s furry and looks menacing, but is it?

In Sunol there are two types of tarantulas: the blond and the brown tarantula. Pictured below is a brown tarantula or Aphonopelma smithi. This fellow was spotted by our field engineer, Ryan Dougherty.

If you’ve noticed an increase in spotting them, you’re not alone. In fact, it’s mating season for these giant arachnids. Male tarantulas will spend a lot of time weaving webs just above ground, outside the female’s burrow. If you don’t have a keen and trained eye, it is very difficult to tell the difference between a male and female tarantula. A typical tarantula reaches maturity at around 10 years. Most males die within a year after mating and females can live up to 25 years.

If provoked, the tarantula may inflict a painful bite, about like a bee sting. However, tarantulas tend to have a gentle nature, and rarely uses it’s fangs except to catch prey. If proved, it may raise its front legs and its abdomen to look aggressive. It may also release stinging hairs from its abdomen. These hairs irritate the skin of an attacker by digging themselves in with hundreds of tiny hooks.

They eat a variety of insects and other invertebrates, and their diet sometimes includes lizards, snakes and small rodents. They bite their prey, injecting it with digestive juices. Then they mash it with their strong jaws, and drink the liquid.

The tarantula’s feeding habits are gruesome but it's predator, the tarantula hawk, takes the word “gruesome” to another level. The tarantula hawk is a huge spider wasp. When the female tarantula hawk is ready to lay her eggs, she leaves the flowers behind and goes on the hunt for a tarantula. Once she finds one, she paralyzes it with a sting. Even though the tarantula is several times her own weight, she drags it to a hole, lays her eggs on it, and buries it. The eggs soon hatch into wasp larvae which slowly devour the paralyzed tarantula alive, from the inside out. Below is a picture of a tarantula hawk. Don’t let their beauty deceive you.

Image courtesy of San Antonio Express-News

If you are hiking in or around Sunol be on the lookout for these furry arachnids. Though they have fangs and carry poison, tarantulas are not considered a serious threat to humans. Please try not to step or run over one.

Happy Halloween!

Thursday, October 5, 2017

New Fish Screens at Fish Passage

Last week several members of our Fish Passage project took a trip to Sacramento to examine the project’s fish screens designed by Intake Screen Inc. (ISI). Next week, our team will be installing four of these fish screens at Fish Passage Facilities located in Alameda Creek.

Pictured below is one of the four new fish screens.

Here is Yen Ng, one of our project engineer’s; looking through what is called an internal cylinder brush. The internal cylinder brush is a key component of the fish screen.

Below is a diagram of a fish screen and its significant components.

Image courtesy of

The goal of the Fish Passage Project is to provide for safe passage of fish around the Alameda Creek Diversion Dam to support the restoration of Steelhead trout to the Alameda Creek Watershed. The project is part of the San Francisco Public Utilities Commission’s $4.8 billion Water System Improvement Project (WSIP) to repair, and seismically upgrade portion of the Hetch Hetchy Regional Water System.

Construction is expected to be completed in fall 2018.

See you around the valley!

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!

Friday, August 18, 2017

Photo Friday in Sunol Valley

This week we wanted to share a snapshot of construction underway at the Fish Passage Facilities in the Alameda Creek Watershed located adjacent to the East Bay Regional Park District's Sunol Regional Wilderness.

The photo below shows the construction of the intake structure were the fish screens are being constructed.  This particular intake structure will have a total of 4 fish screens (high tech contraptions that will prevent fish from being drawn into the intake structure).

The goal of the project is to provide for safe passage of fish around the Alameda Creek Diversion Dam to support the restoration of Steelhead trout to the Alameda Creek Watershed. 

This project is part of the San Francisco Public Utilities Commission's $4.8 billion Water System Improvement Program to repair, replace, and seismically upgrade portion of the Hetch Hetchy Regional Water System.

Construction is expected to be complete in fall 2018.

Happy Friday! 

Thursday, August 10, 2017

National Water Quality Month

August is National Water Quality Month! Your drinking water comes from a watershed. And if you are a customer of the San Francisco Public Utilities Commission (SFPUC) or one of our 27 wholesale customers in four Bay Area counties, your drinking water comes from three watersheds: the Tuolumne River Watershed near Yosemite National Park, the Alameda Creek Watershed in the East Bay, and the Crystal Springs Watershed on the Peninsula.

By protecting and preserving the lands that produce our drinking water, we not only support rare and endangered wildlife, we also provide the highest possible quality water to our customers.

In honor of National Water Quality month, we’d like to take this opportunity to remind ourselves how we all can help protect our local watersheds to protect the quality of our water.

The SFPUC owns 35,000 acres of watershed lands in the Alameda Creek Watershed. They are home to critters, like the Western Pond Turtle.

As part of National Water Quality month awareness, there are small things that you can do in your everyday life to help keep and protect water quality. Here are some helpful tips:
  • Use a commercial car wash — cleaning your car at home flushes dangerous chemicals down the storm drain and directly into our lakes and streams
  • Pick up after your dog
  • Dispose of used motor oil properly - one quart of motor oil can contaminate more than 250,000 gallons of water
  • Help pick up litter on the streets that could end up going down the storm drain use detergents that are phosphate-free 
  • Join in a beach, stream, or wetlands cleanup project. Look for local projects in your area.
By doing these simple things you will be contributing to protecting your watershed for future generations.

Thank you and Happy National Water Quality Month!

Thursday, July 13, 2017

Northern Rough-winged Swallow Chicks Relocated at Alameda Recapture Creek Project

During the month of June, part of our construction management team at the Alameda Creek Diversion Dam (ACDD) project relocated 5 adorable Northern Rough-winged swallow chicks.  The relocation of the chicks was done by lead biologist, Chris Pattison, with the assistance of another lead biologist, Matthew Bettelheim. Chris Pattison was the only biologist handling the baby chicks. The entire process was performed under a U.S. Fish and Wildlife (USFWS) relocation permit.

Lead biologist, Chris Pattison preparing to relocate the chicks

Rough-winged Swallow Chicks at ACDD Project

They were immediately transported to the Lindsay Wildlife Hospital for a full veterinarian examination.  All of the baby chicks passed their examinations and were then transferred to the Native Songbird Care and Conservation in Sebastopol, California.  Native Songbird Care and Conservation specializes in insectivorous birdsThe chicks were reared until they were ready for release.

Northern Rough-Winged at ACDD project

A plain brown bird, Northern Rough-winged swallows are common across the United States in the summer. They are solitary and are usually seen singly or in a small group.  The bird gets its name “rough-winged” because their outer wings have small hooks or points.

See you around the valley!

Thursday, July 6, 2017

Preventing Fires in and around our Watersheds

Calaveras Reservoir 

Happy belated Fourth of July!

We are in the middle of fire season and it’s good to keep in mind how we can prevent fires in and around our watersheds.  Our watersheds, the San Antonio and Calaveras reservoirs are a critical part of our infrastructure because they provide clean drinking water to millions of people in the Bay Area.  They’re also home to wildlife, fish and livestock. According to the Environmental Protection Agency, more than $450 billion in food, fiber, manufactured goods and tourism depend on clean, healthy watersheds. Today’s blog is a continuation of our summer fire safety series, focusing on preventing fire in and around our watersheds.

Image courtesy of

Fire Triangle

There are 3 key elements that need to be present in order to ignite a wildfire.  Those three elements are humidity, fuel (grasses, sticks, branches etc…) and wind.  Typically, if the humidity in the air is lower than 30%, coupled with fuel and wind, you’re bound to create a fire.  Out of all of the three elements, wind is the most dangerous because it provides oxygen to a fire. Wind not only controls the direction, spread, and size of fire, but also greatly affects the flammability of plants by reducing fuel moisture.

San Antonio Reservoir

Preventing Fires in and around Watersheds

Here are some helpful tips on how to prevent fires in and around our watersheds:
  • Be careful and stay in well established graded/mowed roads
  • If you have an ATV’s- remember just because you have an ATV doesn’t mean you’re safe 
    • Use ATV’s only if weather permits
  • Pay attention to the condition of the fuel around you, especially on hot, windy days
  • Be aware of your vehicle’s exhaust, whether you’re on an ATV, car or any other type of mechanical equipment
    • If you have to pull over to the side of the road, be careful not to park over dry fuel (grasses)
  • Fireworks- careful not to set them off in or around dry fuel (grasses)
  • Shooting Guns- sparks from guns or any other type of firearm can ignite a fire given the right conditions
  • Mowing –is the biggest causes of fires, try not to mow past 10 a.m.
  • No smoking near the watersheds
 If you see a fire near or around a watershed please call 911 immediately!

Additional fire resources:
·       CAL FIRE at:
National Fire Protection Agency,

Friday, June 30, 2017

Building Dams in Earthquake Regions, Part II

As Californians, we live with the possibility of earthquakes.  Here at the Calaveras Dam Replacement Project we are in the middle of constructing a new dam that will be strengthened to resist seismic forces and withstand a 7.25 magnitude earthquake.  Dam technology has evolved since we built the original dam in 1925. 

If you missed our first blog about the technology used in construction of the original dam, see it here. The methods used in constructing the new Replacement Calaveras Dam are very different. Here’s why.

New Construction Methods

We are using state of the art dam technology and engineering to enhance the safety of this large civil structure.

A Sound Foundation

Our director Dan Wade says that building an earth and rock fill dam is a lot like painting a house. You need to strip all the old paint off the walls to get to good wood. You need to prime the surface so it will hold the new paint. The very last thing you do is paint.  We have been doing the preparation for the building of our dam for 6 years. We have moved more than 7 million cubic yards of soil to reach competent rock as a solid foundation of the new dam. 

A cross section of the replacement dam showing the different zones. Green is upstream (the reservoir side), light yellow is downstream, the clay core is in the center, and the narrow yellow strips are the drains and filters.

Controlling Water Seepage

We have drilled the grout curtains (see our previous blog about curtains and blankets) extending more than 100 feet below the dam’s foundation to control water seepage. We have done even more work to treat the foundation of the core of the dam, which is made of impervious clay. Remember the drain blanket? That also is constructed on the downstream face (the dry side away from the reservoir) to control water. The new dam will have various filter zones and drain zones on both sides of the dam to control the movement of water so it does not compromise the structural integrity of the dam.

Resisting Seismic Forces

A wide core will help the new dam be robust. In addition, the materials placed in this dam will be compacted using heavy machinery.

Here's the dam being constructed as it looks now. The different zones are clearly visible.

The complete removal of unstable rock and soil to form a solid foundation, careful design and placement of filters and drains within the dam to control water, extensive grouting and sealing of the foundation of the dam, a robust core and heavy compaction of all materials enable the replacement Calaveras Dam to withstand seismic forces and serve our customers for generations to come.

Monitor our progress at building the dam here at

See you around the Valley! 

Friday, June 23, 2017

Building Dams in Earthquake Regions Part I

The First Two Calaveras Dams

As Californians, we live with the possibility of earthquakes.  Here at the Calaveras Dam Replacement Project, we are constructing a new earth and rock-fill dam that will be strengthened to resist the seismic forces and withstand a 7.25 magnitude earthquake. 

Dam technology has evolved since we completed the original dam in 1925. In a two-part series, we’re going to take a look at how our predecessors built the previous Calaveras Dam, which has served us well for 90 years, and what new technologies and construction methods we are using for the new dam to be ready for the next big quake.

The original Calaveras Dam (construction spanned 1913 to 1918) was constructed using the so-called hydraulic fill method.  Basically, to create the impermeable 'puddle core', fine soils were washed off the surrounding slopes with high pressure water cannons, and this slurry was collected between two 'training' dikes on both sides of the dam’s core.

During gold mining in the Sierra foothills, this method was used to build much smaller dams to impound water for hydraulic mining. But scaling this method up to this size had some serious problems. 

The first Calaveras Dam, nearly complete in 1918. It was the largest earthen dam in the world at the time.

The process did not allow excess water in the puddle core to dissipate, and this extra weight exceeded the ability of the upstream shell to retain it, and it failed as it neared completion.

The second (current) dam was completed in 1925 and was built on the remains of the first dam. For the current dam, soil was compacted in the core, primarily by running heavily-loaded wagons over it (pulled by mules). In this photo you can see the mule trains compacting the core.

The second Calaveras Dam, shown in 1926.

However, one problem that wasn't addressed during the construction of the current dam was the fact that alluvial soils (creek sediments including silt, sand, and gravel) were not removed before the first dam was constructed. Such saturated, loose sediments, which are removed during the construction of a modern dam, have the potential to 'liquefy' as they are shaken during an earthquake. 

It was for this reason that we at the SFPUC elected to build a completely new dam next to the existing dam.  And this time, things were different. 

Stay tuned to learn more!

Friday, June 16, 2017

Bald Eagle Photo Friday at San Antonio Reservoir

Happy Photo Friday!

This week’s pick comes courtesy of Kevin and Pat from our Natural Resources and Lands Management staff.

We have spent a lot of time writing about the nesting pairs of bald eagles who reside at Calaveras Reservoir and the pair near our restoration sites near San Antonio Reservoir in the SFPUC-owned Alameda Creek Watershed. But we’d like to introduce you to a more recent arrival to the San Antonio Reservoir area.   

This pair has made its home closer to our Turner Dam at San Antonio Reservoir.  Since it is the time of year when our pairs are on their nests taking care of chicks, our staff spotted two eaglets in their nest.

Once bald eagles find a nesting location they like, they tend to stay in the area. Which is why these bald eagles and our Natural Resources and Lands Management staff have gotten to know one another.  Our staff monitors the well being of these birds on a weekly basis. They all have been trained on bald eagle monitoring and behavior. Knowing these particular birds and bald eagle behavior enables our Natural Resources staff to know quickly if the birds seem ‘off’ because they have been disturbed by something.  

These little ones will fledge (develop the ability to fly) anywhere from 8 to 14 weeks of age. For now, they’re being fed a consistent diet of fish found in the reservoirs and creeks within the Alameda Watershed.

Healthy watersheds provide high quality water and also provide a safe haven for many amazing plants and animals. We consider it an honor and a privilege to look after these watershed lands, and all who live there, too.

Have a wonderful weekend, everyone!