Fact Check: Spiking San Diego’s Water Supply With Recycled Water

Statement: “As one example, the San Diego Bay Council points to the city of San Diego’s water reuse project that could supply up to 40 percent of San Diego’s water needs,” the San Diego Bay Council wrote in a March 26 press release.

Determination: Mostly True

Analysis: The San Diego County Water Authority board recently approved the agency’s long-range water infrastructure road map, a plan environmental groups say is too dependent on pricey outside sources.

The San Diego Bay Council, a coalition of these groups, argues the county water wonks should put a greater emphasis on conservation and recycling wastewater, which can be transformed into drinking water.

The group claimed in a March 26 press release that San Diego’s recycled water project alone could fulfill as much as 40 percent of the city’s water needs.

I decided to fact check this statement because the city now imports nearly 80 percent of its water from the distant Colorado River and Sacramento-San Joaquin Delta, a dynamic that’s gotten more attention in the midst of the state’s worst-ever droughts. Getting more than a third of its water from an inside source would be significant. And it would be even more noteworthy if the city could draw that much from recycled water.

The city wants to recycle 101 million gallons of sewage daily by 2035.

Those efforts are also partly motivated by the Environmental Protection Agency, which has repeatedly given the city waivers to cope with its outdated Point Loma Wastewater Treatment Plant. That is the city’s major sewage treatment plant and it pumps millions of gallons of waste into the ocean that doesn’t meet stringent federal pollution guidelines, though the city’s permit exempts it from some Clean Water Act standards.

Investing in the process to turn this waste into safe drinking water would shave a significant amount off the city’s bill to revamp the Point Loma facility and shield it from at least some of the growing expense associated with imported water.

Here’s a look at the city’s estimate of the rising cost of imported water versus sinking cash into the water recycling process:

As you can see, either approach will cost the city but public utilities officials estimate they’ll save at least $250 million over 20 years with the recycling process.

But would all this investment deliver up to 40 percent of the city’s water supply?

Ann Sasaki, an assistant director in the city’s public utilities department, said the city estimates it’ll need to provide 267 million gallons of water daily by 2035 to meet residents’ needs.

In about 10 years, Sasaki said the city hopes to expand its North City reclamation plant in Mira Mesa so it can process 15 million gallons of recycled sewage each day.

Sasaki said this figure and other city estimates factor in losses associated with sewage and water treatment processes. It’s a multi-step operation. Wastewater will go through the city’s typical procedures and then through advanced-water treatment. From there, the water will sit in the city’s San Vicente reservoir for a period of time. It will eventually be treated again before it makes its way through San Diegans’ taps.

The next step will be to bolster the city’s South Bay plant in the Tijuana River Valley, which the city envisions eventually handling 15 million gallons of sewage daily.

These two plants would produce another 18 million gallons of recycled water that city plans to use for industrial or irrigation uses too.

The city also wants to build a new plant on Harbor Drive that would treat another 53 million gallons of water per day, Sasaki said.

This adds up to 101 million gallons of processed recycled water each day.

That total fulfills about 38 percent of the city’s projected 2035 water needs, just shy of the 40 percent the San Diego Bay Council claimed in its press release.

But there are a couple crucial nuances worth pointing out.

The Bay Council used another formula to come to this total. They added up the total capacity of the city’s three drinking water treatment plants to come up with an estimated water supply need. They also assumed about 10 percent of the water would be lost in the treatment process, meaning 320 million gallons of sewage would need to be processed each day to fulfill the roughly 40 percent the group claimed the recycling project could bring in.

Also, it will be more than two decades before San Diegans can assess the success of city efforts to transform wastewater into safe drinking water and the city’s public utilities department is still hashing out its plans. They’re set to deliver more detailed ones to the City Council this fall – which brings us to another potential variable. The city’s elected leaders could decide they’d prefer another approach and push for changes that affect the amount of recycled sewage the city plans to convert into drinking water.

These unknowns make the San Diego Bay Council’s statement mostly true.

If you disagree with our determination or analysis, please express your thoughts in the comments section of this blog post. Explain your reasoning.