As Valley Water makes progress at Anderson Dam, the project increases in size and cost

The seismic retrofit of Anderson Dam is Valley Water’s top priority. It will help us protect our regional water supply, ensure public safety, and provide environmental benefits.

Since conducting a groundbreaking ceremony in the summer of 2021, great strides have been made in phase one of the project. As of January 2022, almost 9% of the Anderson Dam Tunnel Project work has been completed.

A new tunnel will allow Valley Water to better maintain water levels in Santa Clara County’s largest reservoir. Excavation work and improvements to make the ground around the tunnel more stable are currently underway. Work in recent months has also established project site offices, staging areas, security fencing, lighting, temporary utilities, and the installation of devices that monitor the ground around the tunnel itself.

While the Anderson Dam Tunnel Project remains on pace for a mid-2024 completion, at a January 2022 board meeting Valley Water’s Board of Directors was informed of a change in cost to the overall project. It was recently determined that the Anderson Dam Seismic Retrofit Project will increase to an estimated $1.2 billion to complete. This is an additional $584 million over the next 11 years and takes into account phases one and two of the project.

There were a handful of factors that caused the price increase, including:

• A Federal order splitting the project into two phases.
• Additional State and Federal regulatory requirements which add previously unforeseen work.
• Increased project duration due to environmental permitting requirements.
• Supply chain and workforce shortages caused by the COVID-19 pandemic.

Originally, the project’s objective was to seismically retrofit the 70-year-old dam. During the design phase, investigations revealed a more extensive retrofit was necessary to prevent the dam from slumping in the event of a large earthquake. Consequently, it was necessary to construct an entirely new tunnel outlet, and completely remove and replace the entire dam.

While the length of time and cost to replace Anderson Dam has gone up, our critical work there will protect local communities from harm and Santa Clara County’s water supply for generations to come.