Arsenic soil concentrations at many environmental investigation sites in Florida and other states have been reported above the current U.S. Environmental Protection Agency (EPA) soil screening level (0.4 mg/kg) and above the recently modified (2005) Florida default residential exposure Soil Cleanup Target Level (SCTL) of 2.1 mg/kg. At a site in west central Florida, arsenic soil concentrations were compiled site-wide during early routine sampling. In a state-specific 2001 study of background concentrations of arsenic in Florida soils, 27 out of the 51 counties that were evaluated contained arsenic soil concentrations above the EPA soil screening level. Ten out of the 51 counties that were evaluated had arsenic concentrations in soil regularly above the then-applicable residential exposure SCTL of 0.8 mg/kg. That study also identified elevated arsenic concentrations above FDEP’s residential exposure SCTL in a geographic “belt” from Leon and Madison counties in NW Florida to Lee and Charlotte counties in SW Florida. This belt includes Hillsborough County, in which the Site is located. Based on a very extensive site database for surface and subsurface soil, it was concluded that the observed arsenic concentrations at the Site represent a naturally occurring condition (2.4 mg/kg mean and 2.8 mg/kg 95% UCL drawn from over 2,000 site soil samples). The close agreement between the mean and the 95% UCL concentrations indicates a low degree of statistical variability across the Site, and is supportive of the conclusion that the observed distribution represents naturally occurring background. Further, while the 2.8 mg/kg UCL exceeds the Florida default residential cleanup target of 2.1 mg/kg, it does not represent a significantly increased human health risk (1.3x10-6 excess lifetime cancer risk). While there was no regulatory involvement, preparation of the initial background survey, a site risk evaluation, and evaluations of local background arsenic concentrations allowed the Site owner and prospective developer to determine that the 340 acre site was suitable for residential improvement.
Teaf, Christopher M.; Covert, Douglas J.; Coleman, R. Marie; Petrovich, Michael; Murali, R.S.; and Yarina, Vince
"Risk And Background Evaluation For Arsenic In Soil At A Planned Residential Development,"
Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy:
Vol. 12, Article 8.
Available at: http://scholarworks.umass.edu/soilsproceedings/vol12/iss1/8