In 2013 to 2015, the U.S. EPA Remedial Project Team completed supplemental Remedial Investigation (RI) sampling activities to close data gaps associated with the extent of downstream contamination in OU3. The St. Louis High School athletic fields were sampled in 2014 and 2015 as part of the supplemental RI activities in OU3. Sampling activities in OU3 under the baseline and supplemental RI sampling programs have consisted of surface water sampling, in-stream sediment sampling, biota sampling (including benthos, fish, small mammals and other biota), and floodplain soil sampling (including the St. Louis school athletic fields).
The results of the sampling event indicate that thirty-eight (38) of 180 sample results exceed the spatially averaged soil PRG of 5 mg/kg established at the Site for the protection of birds. None of the sample results exceed the recreational-based, human health clean up standard of 463 mg/kg established by EPA for total DDT. In addition, the sample results do not exceed the non-residential generic cleanup standards of 400 ppm for 4,4-DDD, 180 ppm for 4,4-DDE, or 280 ppm for 4,4-DDT in Michigan’s part 201 direct-contact cleanup criteria for non-residential areas. The results ranged from 0.02 ppm (VCS-OU3-SO-180) to 82 ppm (VCS-OU3-SO-182). The highest concentration (82 ppm) is located near the bank of the Pine River within grid A-1 in close proximity to the athletic fields long jump track. Concentrations of the banned pesticide DDT in floodplain soils in the athletic field areas may present unacceptable, short-term risk to ecological receptors based on previous risk assessment work for OU1 of the Site which identified 5 ppm DDT in soil as an ecological risk-based cleanup level for DDT in soil based on dietary exposure of American robin (Turdus migratorius). Based on the sample results and the human health standard that applies to the recreational use of the Site, EPA does not believe the DDT-contaminated soil presents an unacceptable risk to human health.
