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An extensive sampling plan and sampling activities were implemented to evaluate the potential pathways by which plutonium reached the Big Trees Park in Livermore, California. The pathways evaluated included air dispersion, release of plutonium into the former and current Arroyo Seco, sewage sludge distribution, and atmospheric fallout deposition from LLNL activities.

Based on this analysis, ATSDR believes the most credible pathway by which plutonium radioisotopes reached Big Trees Park was the application of plutonium contaminated sewage sludge as a soil amendment. This is based on a comparison of the concentrations of both plutonium and heavy metals collected from within tree wells to the concentrations present outside the tree wells. Although there is an elevated concentration of plutonium in the park, the levels are below the levels of health concern set by EPA (Region IX preliminary remediation goals; less than a risk of 1 in a million) and below the recommended levels which NCRP has set for requiring additional activities. No other pathway appears to be a viable pathway for the presence of plutonium in the park.


No additional sampling is recommended at this time. Without the log book indicating who received the sludge, no way exists to determine appropriate sampling locations. The California Department of Health Services has agreed to continue investigating the issue of sewage sludge distribution from the Livermore Water Reclamation Plant. Unless additional information is obtained indicating specific locations where sludge was used, further sampling efforts would be inconclusive.

Paul A. Charp, PhD
Senior Health Physicist


  1. California Department of Health Services, Environmental Health Investigations Branch (1999). Lawrence Livermore National Laboratory Plutonium Contamination in Big Trees Park, Livermore, Alameda County, California. CERCLIS NO. CA2890012584.

  3. University of California (1998). Livermore Big Trees Park 1998 Soil Sampling Plan. Lawrence Livermore National Laboratory, Livermore, California. October 1998. UCRL -ID-130551.

  5. U.S. Environmental Protection Agency (1998). Split sampling plan, Livermore Big Trees Park, Lawrence Livermore National Laboratory. EPA Region IX. August 1998. Document Control Number 4900-06-023-AAAB.

  7. U.S. Environmental Protection Agency (1994). Confirmatory Sampling of Plutonium in Soil from the Southeast Quadrant of the Lawrence Livermore National Laboratory. National Air and Radiation Environmental Laboratory, Montgomery, Alabama.

  9. MacQueen, D. (1995). Livermore Big Trees Park January 1995 Soil Survey Results. University of California, Lawrence Livermore National Laboratory. UCRL-ID-121045.

  11. Memorandum from Joe Eidelberg, Quality Assurance Office, EPA Region IX, to data reviewers. December 18, 1998.

  13. Gallegos, G. (1995). Surveillance monitoring of soils for radioactivity: Lawrence Livermore National Laboratory 1976 to 1992. Health Physics 69:487-493.

  15. Hardy, E.P. (1975). "Regional uniformity of cumulative radionuclide fallout" in Fallout Program Quarterly Summary Report. New York: Health and Safety Laboratory, Atomic Energy Commission. HASL-288:I2-I10.

  17. Hulse, S.E., Ibrahim, S.A., Whicker, F.W., and Chapman, P.L. (1999). Comparison of 241Am, 239,240Pu and 137Cs concentrations in soil around Rocky Flats. Health Physics 76:275-287.

  19. National Council on Radiation Protection and Measurements (1999). Recommended screening limits for contaminated surface soil and review of factors relevant to site-specific studies. NCRP Report 129. Bethesda, MD. 353 pp.

  21. Kennedy, J.B. and Neville, A.M. (1986). Basic statistical methods for engineers and scientists. 3rd edition. Harper and Row Publishers, Inc. New York: 613 pp.

  23. Letter from B.R. Tamplin, California Department of Health Services, Sanitation and Radiation Laboratory Section, to Carl L. Lindeken, Lawrence Livermore Laboratory, Environmental Evaluation Group, Hazards Control Division dated October 31, 1980.

  25. Efurd, D.W., G.G. Miller, D.J. Rokop, F.R. Roensch, and 19 additional authors (1997). Evaluation of the anthropogenic radionuclide concentrations in sediments and fauna collected in the Beaufort Sea and Northern Alaska. Los Alamos National Laboratory. LA-13302-MS, UC-000 and UC-702.

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