(Washington, DC) — The US Environmental Protection Agency (EPA) released sampling results in response to a joint request from District of Columbia Mayor Adrian M. Fenty and Rock Creek Park Superintendent Adrienne Coleman of the National Park Service. The lab results confirm preliminary results of soil sampling conducted on May 15 at Fort Reno and surrounding sites.
Forty-seven samples for arsenic were taken using a handheld XRF (X-Ray Fluorescence) monitoring instrument, and 13 soil samples were collected that were sent for detailed lab analysis. Preliminary lab results from these soil samples have been scientifically verified by the EPA. The XRF sampling ranged from a low of 0 to a high of 12.3 parts per million of arsenic, although XRF sampling is subject to a wider margin of error. More detailed lab-analyzed soil samples range from a low of 1.4 to a high of 10.1 parts per million. In comparison, an EPA screening level for residential properties for arsenic is 43 parts per million. The Agency for Toxic Substances and Disease Registry states that levels below 20 parts per million of arsenic in soil do not present a threat to human health.
The Fort Reno closure was prompted by soil-sample analysis conducted by the US Geological Survey (USGS) at six sites at Fort Reno in April of this year as a follow-up on research connected to an aerial photograph used to identify areas of potential arsenic contamination. Based on this monitoring, also done with XRF technology, USGS reported arsenic concentrations in the soil that ranged from 100 to 1100 parts per million. These high numbers caused the Park Service to close the park and triggered a further investigation into arsenic in the Park and two local schools and nearby areas. The USGS is conducting another analysis of the same samples, using a different lab and a different method.The results are expected by the end of the week.P>
The District of Columbia, National Park Service, EPA and USGS are continuing to take every precaution to ensure public safety and are developing an additional sampling strategy to investigate and resolve the discrepancy between the monitoring and sampling results, including taking additional soil samples at the specific locations of the previous USGS sampling sites. Fort Reno will remain closed by the National Park Service until the discrepancy has been further investigated and the potential risk to the public fully evaluated.