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Surfrider's Beach Water Radiation Testing at San Onofre

Surfrider conducted its second collaboration with the Woods Hole Oceanographic Institution’s Our Radioactive Ocean program to test beach water near the San Onofre Nuclear Generating Station for radioactive isotopes. The testing was designed to get a better understanding of potential radiation exposure from irradiated water while surfing in the area. Results again came back higher than the ambient ocean level of California coastal waters impacted by Fukushima, yet well below drinking water limits. This study was made possible thanks to donations from the Nicholas Endowment Foundation. 

At a 2018 San Onofre Nuclear Generating Station (SONGS) Community Engagement Panel meeting, Surfrider learned about batch liquid radioactive effluent releases legally allowed to be dumped offshore of San Onofre State Park, a popular and cherished beach, surfing destination, campground, and cultural site. Surfrider immediately took action to learn more about the releases, advocate for stronger public transparency and outreach, and conduct independent, third-party testing of water radiation levels to better understand exposure. 

Radioactive Effluent Releases

Batch radioactive liquid effluent releases have occurred at SONGS since 1968, despite the plant closing in 2013, when the nuclear power plant was shut down. Southern California Edison representatives stated via email that from 2000 to 2011, the plant averaged 171 radioactive liquid effluent releases each year. While the effluent is highly treated before being released, the treatment and filtration are not completely effective, meaning not all radioactive isotopes are removed before effluent is discharged into the marine environment. Alarmingly, this is a common practice across the nation’s coastal nuclear power plants, which are regulated by the federal Nuclear Regulatory Commission (NRC). 

During San Onofre’s decommissioning, the frequency and size of releases have been greatly reduced, yet still take place as a way to “dispose” of radioactive liquid collected from contaminated places like certain facility HVAC systems. Releases also include wastewater from two spent fuel cooling pools actively getting drained in preparation for their upcoming dismantlement as part of the ongoing decommissioning and deconstruction of the nuclear plant.

The History: Advocating for Public Transparency

In addition to the concern about these intentional radioactive releases into the ocean, Surfrider was extremely disappointed in the severe lack of public transparency and notification. Nuclear plant operators are required to conduct thorough testing of their radioactive effluent and report releases and concentration levels to the NRC, yet do so only after the fact in an annual report. The reports do not provide detail on individual releases, and instead just provide the summation of released radioactive isotopes and effluent volume cumulatively over the course of the year. This means the public had no opportunity to be aware of when these releases were occurring, and what radiation dose they might be exposed to while recreating in the vicinity of the outfall site, which is only 1.1 miles offshore of a very popular surf break.

This was unacceptable. Surfrider started conducting outreach to Southern California Edison, the plant’s majority owner and operator, and state regulators including the California State Lands Commission, to get public notification included as a committed condition in upcoming permits. After multiple conversations, Southern California Edison voluntarily agreed to provide 48-hour advance public notifications of future batch releases to allow beach goers and the community to be better informed about potential radiation exposures. Their advance public notification commitment was codified in their State Lands Commission decommissioning permit. It’s our understanding that this was the first time a nuclear plant in the United States committed to and provided routine advanced notification of liquid radioactive batch releases. Surfrider California monitored their notification website and helped disseminate notifications on social and website channels.

Beach Water Radiation Testing

Now that the coastal community had the ability to be aware of upcoming radioactive effluent releases and additional (albeit reportedly low) exposure during coastal recreation in the area, Woods Hole Oceanographic Institution’s (WHOI) Our Radioactive Ocean program shared an opportunity to conduct independent testing of beach water radiation levels. The Our Radioactive Ocean (ORO) program was developed by Dr. Ken Buesseler, an internationally-recognized expert on radionuclides in the marine environment, founder of the Center for Marine and Environmental Radioactivity (or CMER) at Woods Hole, and the lead for tracking marine radiation levels from Japan’s 2011 Fukushima radioactive contaminant release

At ORO, Dr. Buesseler established a volunteer monitoring program where coastal community members can order sample kits and follow very clear and simple sampling methods to collect a sample of their local beach water to ship back to ORO’s lab. Researchers at ORO then process and test the samples for the presence and concentration of Cesium-137 and Cesium-134, radioactive byproducts of nuclear fission (a process used by nuclear generation facilities). These radioactive forms of cesium are not naturally occurring, but occur at low levels everywhere due to human sources, including atmospheric testing of nuclear weapons in the 1950’s and 60’s, and the nuclear power industry. Learn more from The Agency for Toxic Substances and Disease Registry.

With this option in hand, Surfrider has now conducted two “before-, during-, after-release” studies of ocean radiation levels offshore of San Onofre to test if effluent releases resulted in a measurable increase in radioactive isotopes (specifically Cesium-137 and 134) in the surf zone. Samples were pulled in the surf zone near the southern end of San Onofre State Beach to reflect likely exposure during surfing and coastal recreation. Samples were also taken at the surface near the ocean outfall 1.1 miles offshore. The “before” samples capture baseline measures to compare with the “during” and “after” measurements.

Image 1. Offshore outfall sample collection. Samples collected by Surfrider staffer Andrea Powell and UCI Assistant Professor Dr. Finkeldei (pictured), and Dan Stetson (volunteer boat captain).

The first study was conducted in 2021 and 2022, with results available here. The second study was just recently completed in 2023, with baseline or “pre-release” samples collected on June 7, “during release” samples collected on June 8 (during a stated release of 140,450 gallons of irradiated water from SONGS spent nuclear fuel cooling pools), and “after release” samples collected on June 11. Surfrider also collected duplicate samples to share with Dr. Sarah Finkeldei’s lab at the University of California at Irvine (UCI) for additional radiation testing.

2023 WHOI ORO Study Results

All six results had “below detection” levels of Cesium-134, meaning the concentration of that isotope was so low that it was immeasurable, even with the highly sensitive equipment used by Woods Hole. The Cesium-137 levels at all tested locations were higher than what’s considered to be the “ambient ocean concentration level” of 2 Bq/m3, but showed no changes throughout the study. The surf zone water samples remained constant at 2.5 Bq/m3. Offshore samples showed a small decrease “during the release” then back to the initial levels, but the difference was within the margin error of the testing equipment (+/- 0.1), so again is considered to have no measurable difference between before-during-after samples (2.7 Bq/m3 before and after, 2.6 Bq/m3 during). 

Table 1. Results of beach water radiation sampling. Cesium-137 concentration results from each sampling event are provided alongside the “ambient ocean concentration level” and EPA’s drinking water limits for comparison.

Takeaways, Limitations and Suggested Next Steps

This study did not identify any measurable difference in Cesium-137 or Cesium-134 concentrations in the surf zone from a single radioactive effluent release; however, this study was only looking at surface water concentration levels after ocean mixing had occurred. Results should not be used to infer radiation levels in beach sand, offshore sediment or seawater closer to the discharge pipe and diffusers. Surfrider strongly encourages additional independent testing of other coastal environments near the nuclear plant, including testing of beach sand, offshore sediment and water located closer to the discharge pipe for a more comprehensive understanding of potential exposure during coastal recreation. 

Cesium-137 and 134 were the only radioactive isotopes analyzed during this study because those are the isotopes this specific WHOI ORO testing equipment is able to determine and quantify. It is possible that other radioactive isotopes are present in the beach water. Reduced radiation levels observed since 2021 and 2022 samples could be the result of further decay of previously released Fukushima Cesium-137, decay of previously released San Onofre Cesium-137, or broadly further decay of other sources such as legacy military testing. Surfrider looks forward to learning more about results of UCI’s testing efforts of samples provided; and will continue to track upcoming releases on our Radiation Release Tracker.

To learn more about WHOI’s ORO volunteer testing program and how you can collect samples to do a similar study, visit To make your voice heard about the importance of getting nuclear waste off the California coast, take action here!