In November 2010, a well water sample from a home near Tolono (labeled as well TOL-1 for this study) was sent to the Illinois State Water Survey’s (ISWS) Public Service Laboratory (PSL) in Champaign. The total arsenic (As) concentration was determined to be 344 micrograms per liter (μg/L), more than 30 times the maximum contaminant level (MCL) of 10 μg/L allowed for public water supplies. This was the highest As concentration ever measured by the PSL. Several neighbors of this well owner subsequently sent in well samples to the PSL, and some of them had As concentrations above the MCL, although considerably lower than TOL-1.
|Name||ISWS Miscellaneous Publication MP 196|