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Between 1944 and 1964, multiple liquid radioactive waste streams were released into the South Fork of Acid Canyon from Los Alamos National Laboratory. From 1944 to 1951, “untreated radioactive effluent from former Technical Area (TA) 1 was discharged into the head of the South Fork of Acid Canyon” and from 1951 to 1964 a “radioactive liquid waste treatment plant at former TA-45” discharged its effluent into the canyon. Today, this area is located within 1,000 feet of a residential neighborhood and less than a mile from a local high-school.1 We chose to examine the remediation of Acid Canyon because; (1) it is a site that is already accessible to the general public, (2) it has already had remediation efforts undertaken based, in part, on analyses conducted by DOE for site-specific exposure scenarios, and (3) it illustrates some of the general concerns that will arise at Los Alamos and other sites which have actinide contamination (uranium, plutonium, neptunium, americium, etc.) as the main driver of risk.
In the South Fork of Acid Canyon the following radionuclides were identified by DOE as being of potential concern:
Tritium (H-3), Strontium-90, Cesium-137, Uranium-234, Uranium-235, Uranium-238, Plutonium-238, Plutonium-239, and Americium-241.2
Given the lack of edible plants in the canyon and that fact that no hunting or fishing is allowed, the authors of the Interim Report on Sediment Contamination in the South Fork of Acid Canyon (hereafter the Interim Report) considered only the external gamma, soil ingestion, and soil inhalation pathways in conducting their analysis. In light of the proximity of residential areas to the canyon, it was assumed that the canyon could be used by children as an extension of their backyards and that adults could use the hiking/jogging trails in the canyons which cross and pass near contaminated areas.3 Except for tritium, which is not a major contaminant of concern in Acid Canyon, the extended backyard scenario is the most restrictive scenario evaluated by DOE, and therefore will be the focus of our current review. This is because the present case study is focused on a review of Los Alamos’s calculations of the consequences of its remediation strategy.