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!
