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!

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 sfwater.org/sunolvalley.

See you around the Valley! 

National Dam Safety Awareness Day

As construction continues at the Calaveras Dam Replacement Project, we take a moment to recognize May 31^st as National Dam Safety Awareness Day. Each year on May 31st, the nation remembers teh devastation that occurred on May 31, 1889 in Johnston, Pennyslvania when the South Fork Dam failed. This tragic event resulted in thousands of deaths and left many homeless. The Johnston disaster was the worst dam failure in the history of the U.S.

National Dam Safety Awareness Day reminds us of the importance of dam safety and preventing future failures. Dams provide many befefits such as water supply and storage, hydropower, recreation, flood prevention and improve wildflife habitats.

 

This also reminds us how critical and important our work is here in Sunol Valley to rebuild the Calaveras Dam. We are currently 66% complete and anticipate final completion of the dam in end of 2018.

The Calaveras Replacement Dam when complete will provide us:

·         The largest drinking water reservoir in the local Bay Area storing 31 billion gallons (96,850 acre ft) of water, providing more than half of the storage capacity for 2.6 million customers

·         A new seismically upgraded dam with a structural height of 220 feet, a crest length of 1210 feet and width of 80 feet at the crest and 1180 feet at the base

·         A new 1550 ft spillway and a new intake/outlet shaft tower which will convey water to and from the reservoir through a pipeline downstream and to our Bay Area customers

 

Aerial Photo of the Calaveras Dam Replacement Project
taken on May 21, 2015

 

 

The New Irvington Tunnel is officially in service!

Our teams are excited to announce that the New Irvington Tunnel is officially in service carrying drinking water to our 2.6 million Bay Area customers.

This is a major milestone since the completion of the New Irvington Tunnel Project completes the last three tunnels in the Water System Improvement Program (WSIP), creating a critical water lifeline able to withstand earthquakes on the Hayward, Calaveras, and San Andreas faults.

Located between the Sunol Valley and Fremont, the new seismically-designed tunnel is the last of three tunnels making up this “water lifeline” around the Bay.  The project is part of the agency’s $4.8 billion Water System Improvement Program.

The tunnel was constructed by the joint venture of Southland Tutor Perini who began tunneling in March 2011. It was constructed using conventional mining techniques from four separate headings using road headers and controlled detonation to break up the hard rock.

Tunnel Facts:

• Tunnel Length: 18,660 feet or 3.5 miles
• Location: Parallel to the existing tunnel between Sunol Valley and the City of Fremont 
• Depth: Between 30 feet and 700 feet underground
• Finished internal diameter: 8.5 feet
• More than 7.8 million pounds injected into the tunnel
• The New Irvington Tunnel will carry approximately 120 million gallons of water a day on average during normal operating conditions when both tunnels are in service.
• The maximum amount of water the tunnel can transport per day: approximately 300 million gallons 
• This project provided approximately 42% of total labor hours to SFPUC service territory residents, and nearly half (48%) of total apprentice hours to SFPUC service territory apprentices ensuring our local workers and local residents were able to participate in this unique, once-in-a-lifetime construction opportunity.

What Happens Next?

Now that the tunnel is in service, the construction team will begin restoration of the above ground facilities. The SFPUC will take the existing tunnel out of service for inspection in early March 2015. The entire New Irvington Tunnel Project will be complete in Fall 2015.

1933: Historic photo of  worker at Irvington Portal spherical manifold

Today: New Irvington Tunnel worker at new dishhead at Irvington Portal

Sunol Valley: Getting Prepared – Seismic Upgrade Work Continues

Much has already been done as mentioned in our last post, but more important work lies ahead in Sunol Valley.  Our teams continue critical work to seismically upgrade our infrastructure. As we remember the Loma Prieta earthquake this week, here are some highlights on our ongoing projects:

New Irvington Tunnel Project
The new tunnel will provide a seismically upgraded connection between water supplies from the Sierra Nevada Mountains and the Alameda Watershed to Bay Area customers. It will extend 3.5 miles and have an internal diameter of approximately 8.5 feet. Final completion is expected in mid-2015.

Calaveras Dam Replacement Project
Work continues to build a replacement dam that will be seismically safe and restore the Calaveras reservoir to its historic capacity. The reservoir provides half of the Hetch Hetchy Regional Water System’s local Bay Area water storage. To date, over 5 million cubic yards of materials have been excavated and major work is being done on the new spillway. Final completion is expected end of 2018. 

San Antonio Backup Pipeline Project

The San Antonio Backup Pipeline (SABPL) project will include several new facilities and improvements in the Sunol Valley to help provide for the reliable movement of Hetch Hetchy water for planned and emergency discharges under future conditions. Completion is expected in March 2015.

We are extremely proud of our hard working teams in Sunol Valley, helping all of us become better prepared for the next earthquake. For more info, please contact us at our 24 hour answer line 866-973-1476.

Sunol Valley: Getting Prepared

This week we acknowledge the 25^th Anniversary of the Loma Prieta Earthquake. On October 17, 1989 at 5:04 p.m, the magnitude 6.9 Loma Prieta earthquake, also known as the “World Series Quake,” lasted 15 seconds causing an estimated $6-10 billion in property loss in the Bay Area. The anniversary is a reminder to all of us to make efforts to be prepared for the next major earthquake.

Here’s a quick snapshot of what’s been done in the Sunol Valley to better prepare us:

San Antonio Pump Station – Completed

The San Antonio Pump Station is one of the key facilities in the Sunol Valley which pumps Hetch Hetchy water through a transmission pipeline to the San Antonio Reservoir to the Sunol Valley Water Treatment Plant. It serves as a critical seismic upgrade project which provides a reliable water supply to our Bay Area customers after a major earthquake.

Sunol Valley Water Treatment Plant – Completed
If the Hetch Hetchy water supplies become unavailable for any reason, this plant enables us to supply the minimum demand of water to our customers, especially those in the East Bay and South Bay. The plant can now provide 160 million gallons of water per day for up to two months in case of an emergency. Previously, that level of service would run out after only a matter of days.

Alameda Siphon No. 4 – Completed
This project will ensure the water system performs properly, and water can be delivered to customers after an earthquake. The Alameda Siphon No. 4 Project extends approximately 3,000 feet from the Alameda East Portal across both the Calaveras Fault and Alameda Creek to the Alameda West Portal. It consists of a seismically-designed thicker-walled pipe in the fault rupture zone, and a tunnel crossing under Alameda Creek.