Valley Water reached a milestone in the summer of 2024 when construction crews completed the final stretch of a 1,736-foot-long tunnel next to Anderson Dam.
Construction crews used a specialized Micro-tunnel Boring Machine to tunnel the final 347 feet, driving 30 feet below the water’s surface. Once the machine drove through the last piece of hillside, crews needed to remove it. In September, a team of divers and other construction workers attached a large crane to the machine sections and lifted them from the reservoir.
While the tunneling is complete, work still needs to be done before construction on the dam begins. Valley Water is preparing the downstream creek channel to safely convey the higher flows of water from the new outlet tunnel. We are also doing more work inside the tunnel, including installing a lining to provide additional structural support.
Once completed, the new, larger tunnel will increase Valley Water’s ability to release water from the reservoir during an emergency.
Valley Water is also making significant progress on a massive structure between the tunnel entrance and Coyote Creek. This diversion outlet structure, which has walls 30 feet tall, will be connected to the tunnel with large-diameter steel pipes. It is designed to reduce the speed of water leaving the reservoir before it enters Coyote Creek.
We anticipate completing the tunnel project by mid-2025. Once we finish building the tunnel, we can start on the project’s next phase, which involves strengthening the dam to withstand a large earthquake. We’re aiming to begin construction on the dam retrofit in 2026. Our agency is now finalizing the project’s design, permitting process, and environmental review.
Our work to retrofit Anderson Dam is a significant undertaking. We must work closely with state and federal regulators, the community, and our contractors to successfully deliver these projects.
Valley Water’s top priority is rebuilding Anderson Dam. Once completed, Anderson Reservoir will be able to store nearly 90,000 acre-feet of water, enough to supply almost 1 million people for a year. This project will help ensure public safety, protect our regional water supply and provide environmental benefits for future generations.
so, when completed several years from now, the Anderson Dam will store the same volume of water as it originally did about 50 years ago…and of course the population served is the same. Surprised that the water district doesn’t provide updates on project cost and over budget amounts with its monthly news. Tax payers and rate payers have a right to know.
Thanks for the input. We provided an update earlier this year regarding the cost at Anderson. https://valleywaternews.org/2024/02/14/amid-cost-increases-valley-water-continues-to-progress-with-anderson-dam-and-other-priority-projects/
A retrofit was needed regardless. Dams only last about 50-100 years when they aren’t built on top of a fault (this one is). Another way to think about it is that, “New seismic data in 2018 prompted the district, which owns the reservoir, to revise and expand its plans for the Anderson Seismic Retrofit, boosting the cost and timetable for the project. The new data from the seismic study require a complete reconstruction of the nearly 70-year-old earthen dam, according to the district.”
-The Morgan Hill Times, October 10, 2019
That was a good newsy about what you guys are up to with water management at the Anderson dam & pond.
Thanks for news. Bill
I suggest you include more descriptive information about “Anderson dam” and “Anderson Reservoir” for those of us who have not grown up in this area to know what you are referring to. I had to search for those terms to find out the article is referring to a reservoir in the hills east of Morgan Hill at the south end of San Jose. Including that short phrase would have made the article more understandable and provided more clarity.
This is a perfect example of bureaucrats that waste our money. Anderson Dam was declared unsafe after the 1989 Loma Prieta earthquake for water levels over half-capacity. So Valley Water quickly schmoozed the PUC to authorize higher customer water rates to pay for the fix. Yet NOTHING has been done to date on seismically retrofitting the dam, and the money was spent on a less-than-1/3-mile tunnel, which is still only 80% complete. They are HOPING to start the fix of the dam in 2026 — 37 years AFTER it was declared unsafe. (They will miss that date!). Yet they have the audacity to say “Valley Water’s top priority is rebuilding Anderson Dam.” There is good reason this company is called “The Golden Spigot…”
This is a perfect example of bureaucrats that waste our money. Anderson Dam was declared unsafe after the 1989 Loma Prieta earthquake. The dam was declared to be unsafe for water levels over half-capacity. So they quickly schmoozed the PUC to authorize higher customer water rates to pay for the fix. Yet NOTHING has been done to date on seismically retrofitting the dam, and the money was spent on a less-than-1/3-mile tunnel, which is still only 80% complete. They are HOPING to start the fix of the dam in 2026 — 37 years AFTER it was declared unsafe. (They will miss that date!). Yet they say “Valley Water’s top priority is rebuilding Anderson Dam.” There is good reason this company is called “The Golden Spigot…”