In September 2009, the U.S. Environmental Protection Agency (EPA) was notified of a potential concern for radioactive isotopes at the Winnebago Tribe. The Winnebago Tribe of Nebraska decommissioned and disassembled their drinking-water treatment facility. The EPA was notified after the tanks were sent to a scrap metal yard, but were denied based on low levels of radiation detected. The tanks were transported to the Winnebago Street Department to be stored until a decision was made on what to do with the tanks. The largest of the five tanks had its contents dumped onto the ground and was sent away for scrapping without any issues. The contents of the tank which consisted of green filter media was scraped together with dirt and erected into a pile approximately 10 feet high. The remaining four tanks are sitting at the Winnebago Street Department and are about 1/3 full of the green filter media. The tanks are about 8 foot tall and 6 feet in diameter. The EPA conducted sampling at the site on September 30th, 2009. EPA conducted sampling of the inside scaling of the tanks, the filter material in the tanks, and the area around the tanks staging area where material had been dumped from the tanks. The results of the testing of the green filter media showed elevated levels of Thorium 228 from 354 to 430 pico-Curie per gram (pCi/g). These levels were well above background and were between 0.32% and 0.39% weight percentage, which is above 0.05% and considered to be source material. It is suspected that the green filter media is the only place where there is a concern for radiation exposure due to the concentration of radioactive isotopes.
The current plan for activities is to begin removal of the material from the site beginning the week of September 20th, 2010.
