In-Depth: $10 million effort to assess San Diego's aging dams

Lower Otay Dam
Posted at 5:14 PM, Jun 04, 2021
and last updated 2021-06-05 01:05:01-04

SAN DIEGO (KGTV) -- The City of San Diego plans to spend $10 million to carefully assess the structural needs of its aging dams, which are among the oldest in California.

San Diego has nine dams that play an important role in the city’s water supply. By 2022, four will have stood for a century or more. Only three of the nine dams are rated in “satisfactory” condition by the state.

The comprehensive assessment will span five years, giving city officials an itemized forecast of future repair needs and costs.

“It will save us money up front to do basic maintenance of our infrastructure, even though the price tag may seem high, to prevent costly emergencies from happening down the road,” said Councilmember Marni von Wilpert, the chair of San Diego’s Committee on Active Transportation and Infrastructure.

Councilmember von Wilpert said California has already seen one such costly emergency in recent years. In February 2017, more than 180,000 people had to be evacuated in Northern California after heavy rainfall damaged the Oroville Dam’s spillways, prompting fears of an imminent collapse.

“We really need to take that as a lesson to make sure we maintain the integrity of our dams here in San Diego,” she said.
Immediately after Oroville, San Diego did a focused assessment of its four dams with similar spillways that cost $5 million. The new $10 million risk assessment will provide the first in-depth look at all nine dams, said Public Utilities Executive Assistant Director Juan Guerreiro.

San Diego’s dams form the “backbone of our water infrastructure,” said Guerreiro.

The city’s nine reservoirs supply about 10 percent of San Diego’s water supply. Every time it rains, the reservoirs collect rainwater, allowing the city to import less water from elsewhere.

“We're able to collect essentially free water,” Guerreiro said.

That rainwater helps lower the monthly water bills for San Diegans, Guerreiro said, but the city is currently unable to use its reservoirs to their full potential.

Because some of the dams need repairs, the city is forced to release rainwater after large storms to keep the reservoirs at a safe level and limit the pressure on the aging dams. However, these “controlled releases” mean the city has to let a certain amount of water savings go to waste.

“It's heartbreaking because here you've invested all this money on dams and now you're letting water go even though you have storage capacity,” Guerreiro said.

The new risk assessment will help shape the city’s long-term spending on its dams. Over the next two decades, repairing, upgrading or even replacing certain dams could cost more than $1 billion, Guerreiro said, although the city won’t have an accurate forecast until the assessment is complete.

San Vicente, Miramar and Sutherland have the state’s highest rating of satisfactory.

The state rates Morena, Barrett and Lake Murray as fair.

The three dams in the worst shape, rated poor, are Lower Otay near Chula Vista, El Capitan near Alpine and Hodges in Rancho Bernardo.

None of the dams are in the state’s worst category of unsatisfactory and city officials say there are no imminent safety risks, but they’re spending now to make sure they never have a dam reach that point.

“We really do need to plan for the future growth of our city and really dig into what our infrastructure needs are,” said von Wilpert. “Making sure that we keep a reliable water supply and maintaining our dam infrastructure is part of making sure that we keep our quality of life here in San Diego.”