Two Dams, Essential To The Salinas Valley, Are In Serious Need Of Repair

Feb 13, 2020

Many communities in Monterey County receive their water supply from two dams. And those dams are in serious need of repair. Later this spring, its likely voters in the county will be asked to decide whether these costly repairs will go forward.

In 2017, a part of the Oroville dam north of Sacramento failed, prompting the evacuation of almost 200,000 people living downstream. 

That incident changed the regulations for dams across California, including the local San Antonio and Nacimiento dams. While they’re located in San Luis Obispo County, they supply water to communities in Monterey County like the Salinas Valley and coastal areas from Marina to Moss Landing.

The Nacimiento dam is located in San Luis Obispo county, but supplies water to the Salinas Valley and coastal areas from Marina to Moss Landing.
Credit Monterey County Water Resource Agency.

The facilities need to be upgraded to a much higher degree than what we've done in the past,” said Brent Buche, the director of the Monterey County Water Resource Agency.

“So in the past, we're able to do repairs. Now it's actually physical, replacing valves, replacing operating units,” he said.

Buche says both dams have always been rated satisfactory. But with these new regulations, more work needs to be done, which requires more funding.

And because these dams were built in the 1950s and 60s, some serious upgrades are also needed -- particularly to the San Antonio spillway, which controls the flow of water leaving the dam.

So the spillway at San Antonio is failing. The floor of it has deteriorated. The chemical constituents in the groundwater [have] actually caused the concrete to fail,” said Buche.

The view from below the San Antonio spillway.
Credit Monterey County Water Resource Agency.

California’s Division of Safety and Dams says the San Antonio spillway needs to be fixed by the end of 2024. 

The replacement of this spillway is by far the most expensive of the 33 projects being proposed.

The total cost for repairs to both dams is $160 million, $60 million for the San Antonio spillway alone.

The Monterey County Water Resource Agency says they can complete all these projects within the next eight years. 

Buche says the high cost will be worth it.

The area in white, ajacent to the Salinas River, marks which property owners will likely to be asked to fund $160 million worth of repairs to the San Antonio and Nacimiento dams.
Credit Monterey County Water Resource Agency.

The releases from Nacimiento and San Antonio Reservoir recharge the groundwater aquifers. Everyone uses groundwater. There is no surface water supply for agriculture and or the residents. And so the repairs that we're making to the dams directly benefit the individuals that live in the Salinas Valley,” said Buche.

Brent Buche, director of the Monterey County Water Resource Agency, speaks at a informational workshop for community members.
Credit Michelle Loxton.

The projects have to be approved by property owners through voting, and if approved, owners will be charged additional taxes based on how they use their land.

For example if you use your property for irrigating crops, you’ll pay more than a simple homeowner or someone who only has animals grazing on their land. 

Also, the more land you have, the more your vote is worth -- it’s a weighted vote.

So ultimately, when we put this out to vote, the largest vote would be the irrigated land, which is obviously linked to agriculture,”Buche said.

Houseboats on the San Antonio dam.
Credit Monterey County Water Resource Agency.

If homeowners don’t agree to fund these projects, the water resource agency will have to reduce water storage levels. Buche says without the repairs, they will be limited in the amount of water they can safely retain. 

If this vote doesn't pass, most likely we’ll have to severely lower the water surface elevation in San Antonio. The amount of water stored in the dam would be severely affected,” said Buche.

Property owners and community members attend a workshop that focused on how the 33 projects to fix the dams will be financed.
Credit Michelle Loxton

Currently, the water resource agency is collecting feedback from the community on how these projects should be financed. It could either be a pay-as-you-go system; bond payments over 30 years; or a combination of the two.

The Monterey County Board of Supervisors will ultimately make the decision on whether or not to go ahead with these projects. Then, if approved, it will go to the voters in the form of a special ballot that will arrive in the mail later this spring.