Areas with elevated radioactivity, referred to as "hotspots" have been identified by surveys similar to the activities shown in the photo (above).
Since the discovery in 2005, several environmental investigations have taken place to identify the cause of the higher than normal radioactive levels in the park.
Below is a chronology of these site activities.
August 2005: Routine Survey
|Radioactive readings were detected in the park (model airplane flying field) during routine surveys of the metropolitan area related to homeland security activities.
||August 2007: Preliminary Assessment (PA)
||NPS conducted a Preliminary Assessment (PA), a study that reviews available documents and interviews knowledgeable individuals about the site to evaluate contamination in the landfill area. Findings were that: primary contaminant appears to be radium (Ra-226) and radioactive decay products; contamination detected at five locations; risk of exposure may be reduced by fencing off suspect areas; and radium- contaminated soil from the five areas shall be removed and disposed of properly.
|March 2007: Radiological Survey
|| In surveying an area where a brush fire occurred, the NPS detected an additional area with elevated radioactive readings. Appropriate federal, state, and city agencies responded. A limited gamma radiological survey was conducted and identified five hotspots. Radiation levels were up to 500 times normal background levels so a more detailed radiological assessment was recommended.
||January 2009: Interim Response Action
|| In January, NPS conducted an interim response action to address the known hotspots of radioactive contamination located near the baseball fields and the model airplane flying field. Prior to this action, an initial survey identified additional "hotspot" locations. During soil removal, two radium bearing devices were recovered. It was this recovery and the additional "hotspots" identified that led the NPS to close the former landfill area to park visitors as a precaution until a comprehensive investigation could be completed.
|May 2007: Public Health Statement
|| The Agency for Toxic Substances and Disease Registry reviewed existing data in order to develop a public health statement for park visitors regarding the levels of contamination at the park. The agency recommended that more information be collected to evaluate the presence and types of radiological and chemical contaminants, as well as identify any potential risks associated with the site.