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Radiation is normal at Cesar Chavez Park, but it’s a different story underground, tests show

New precautions are being urged for workers in contact with underground liquids at the popular landfill-turned-park, but Berkeley residents need not fear a stroll on the surface. 

Berkelyside, by Iris KwokJan. 2, 2025

Radiation testing of Cesar Chavez Park ordered by regional water regulators has found that bird watchers, morning walkers and dogs digging in the dirt have no cause for worry. 

“All radiological activity detected at the ground surface and shallow subsurface is equal to or lower than typical background radiation levels expected in the ambient environment,” according to a report released Monday outlining the results of gamma-ray drone tests conducted this fall by UC Berkeley nuclear engineering experts. 

But underneath the landfill-turned-park, it’s a somewhat different story.

Tests of groundwater and leachate — liquids between 6 to 34 feet underground formed when rainwater filters through landfill — revealed higher-than-usual levels of radium-226, a radioactive metal, according to the report, which found four types of radionuclides in the city’s monitoring wells. 

Groundwater and leachate wells are secured with locks, lids and caps. While the wells are not publicly accessible, there could be a danger for workers. 

“Contractors and maintenance personnel who come into contact with subsurface liquids at the site should now take additional precautions to prevent unnecessary exposure to radiation,” reads the report. Chronic exposure to high levels of radium can increase the risk of bone, liver or breast cancer, according to the Environmental Protection Agency website.

The liquid samples were collected by SCS Engineers, which authored the city-commissioned report, and sent to labs in Pittsburg, California and St. Louis, Missouri for analysis. 

The highest levels of radium-226 were discovered in a leachate monitoring well on the northwestern quadrant of the park, according to the report. The sample taken from that well measured 226 picocuries per liter (a unit of measurement for radioactivity in air) — far exceeding the EPA’s limit of 5 picocuries per liter for drinking water. The highest level of radium-226 found in a groundwater monitoring well was 88.8 picocuries per liter. 

…………………………………………………………………………………………………………………………….. In January 2024, the water board ordered the city to test for the presence of radioactive material in the park after archival documents emerged showing that the now-defunct Stauffer Chemical Company may have dumped 11,100 pounds of potentially toxic industrial waste there in the 1960s and ’70s when it was still a municipal dump. The city closed the landfill in the 1980s, covered it with soil and thick clay, and in the early 1990s reopened it as Cesar Chavez Park. In a July letter to the water board, the city reiterated that it was not previously aware of the potential presence of radioactive material at the site.

…………………………..Berkeley is planning follow-up tests of the radionuclides detected in liquids deep underground at Cesar Chavez Park, but is awaiting further guidance from the water board, city spokesperson Seung Lee wrote in an email. In the coming days, the city plans to share public updates about the test results on its capital projects webpage. 

The water board did not immediately respond to Berkeleyside’s questions about a timeline for the follow-up testing. ………. https://www.berkeleyside.org/2025/01/02/radiation-cesar-chavez-park-underground-landfill

January 6, 2025 - Posted by Christina Macpherson | environment, USA