Monday, December 10, 2012

Calaveras Dam Replacement Project - Winter Update

Project Update
In mid- June of 2012, during excavation of the large hill known as “Observation Hill” on the left side of the valley (if you are looking downstream, standing with your back to the reservoir), the Contractor encountered unexpected geologic conditions that could contribute to the instability of the left abutment and spillway area as designed.  These features were not visible at the ground surface, and were not apparent during the extensive pre-construction geotechnical investigations. Therefore, the excavation cut slope in “Observation Hill” has been re-designed to “lay back” the slope to a flatter slope in order to produce a final slope that will be stable during construction and over the entire life of the new dam.


What this Means
1)    Additional Materials to Move - Approximately 3 million cubic yards of additional material that was not originally anticipated now needs to be excavated and moved to disposal sites around the reservoir. We are working with the environmental regulatory agencies to secure disposal sites for these materials within the designated construction areas. No additional materials will be hauled off site on public roads.

2)    Extended Construction Schedule - Because of the additional time needed to excavate these additional materials, we anticipate a 25 month delay in the project, which would put the completion of construction activities at the end of 2017.

3)    Impact to Project Cost, not to WSIP Overall Cost – Based on preliminary projections, the cost of the project will increase by approximately $133 million. These additional costs are offset by savings recorded on other projects and favorable bond financing so the overall Water System Improvement Program (WSIP) is still forecasted to be completed within the currently approved budget of $4.6 billion.

4)    Calaveras Road Shutdown Delayed - The second scheduled closure of Calaveras Road will be postponed until 2014, at the earliest. The duration of the closure remains 18 months, Monday through Friday only, but the specific dates will be determined when the contractor completes re-sequencing of the construction schedule.  We will notify you in advance of the closure period.  Join our road closure notification mailing list by emailing: mle@sfwater.org or calling our 24 hour answer hotline at (866) 973-1476.
Environmental Review
We are currently working with the regulatory agencies to amend the permits for these changes. The San Francisco Planning Department will distribute an Addendum to the Final Environmental Impact Report in mid-December 2012. To obtain a copy of the Addendum, please visit www.sf-planning.org, or contact: Chris Kern, San Francisco Planning Department at (415) 5759037 or email at chris.kern@sfgov.org.
Project Background
The San Francisco Public Utilities Commission, owner and operator of the Hetch Hetchy Regional Water System, is building a new dam to replace the existing Calaveras Dam in the Sunol Valley. Calaveras Reservoir, impounded by the Calaveras Dam, is our system’s largest drinking water reservoir in the local Bay Area. When full it provides more than half of our Bay Area storage capacity for 2.6 million customers. The existing earth fill dam is 87 years old and is located within 1,500 feet of the Calaveras earthquake fault. In 2001 we lowered water levels in the reservoir to less than 40 percent of normal operating capacity in response to seismic concerns.   The Calaveras Dam Replacement Project is the largest project of the $4.6 billion Water System Improvement Program (WSIP) to repair, replace, and seismically upgrade key components of the Hetch Hetchy Regional Water System.
Work Completed to date
Construction began in August 2011 to build a new earth and rock fill dam adjacent to the existing dam. Since then, the Contractor has moved nearly two million cubic yards of earth and rock materials to make room for the new dam. Crews have prepared disposal sites, constructed a soldier pile tie-back wall to stabilize a landslide in the right abutment (the right side of the valley as you face downstream from the dam, away from the reservoir), and began injecting cement grout deep into the joints in the rock of the dam’s foundation. The team has excavated to the new dam’s foundation and has started to build the new dam. In addition, we have begun construction of connecting outlets from the reservoir, and successfully completed the first 2-month closure of Calaveras Road in spring 2012.  However, there is still a great deal of work that lies ahead, with the project only 26% percent complete as of November 2012.

For more project info, contact us at our 24 hour answer line at (866) 973-1476 or email mle@sfwater.org 

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