EPA first discovered thorium contamination at Lindsay Light's Illinois Street location in 1993. Further investigations found soil contamination at several locations in the Streeterville neighborhood of Chicago  and directly across the Chicago River at the New Eastside neighborhood. To protect workers who might come into contact with radiation and thorium contamination in subsurface soil, EPA and the city of Chicago require anyone planning to work in subsurface soil in these areas to monitor the soil. The resulting reports are posted here.