The Illinois EPA issued a report last month, saying the water in Spring Lake in Macomb had elevated levels of the herbicide atrazine.
The report called a Total Maximum Daily Limit, or TMDL, called the lake impaired. Though the most recent data in the TMDL was from 2009.
Now the IEPA has said high levels of atrazine were detected in the lake as recently as last year.
The IEPA’s Jennifer Clark said even though specific samples exceeded the daily limit, they might not have met the statistical requirements to trigger the type of TMDL it issued in July.
She said the data has been collected but has not been processed, which is why it was not in the database she used for last month’s report.
"It takes a lot time to process it and go through, people have to check the data and make sure everything is right and then they have to enter it into the database," Clarke said.
She said though that she did verify that on at least one occasion atrazine levels exceeded the daily limit last year.
"I just went and looked in the file itself and saw there was hit in 2012," Clarke said.
She said that to call the lake impaired for 2012, 10 percent of the yearly readings would have had to exceed the daily limit, the quarterly average would have to exceed the daily limit, or a single reading would have had to been at least four times the daily limit.
Clark said 2012 data does not necessarily indicate Spring Lake is impaired. She said that determination cannot be made because the data has not been reviewed.
All of the these readings are for the “raw water" in Spring Lake.
The water that Macomb residents drink has been treated with activated carbon, and the readings for that water have not exceeded recommended levels.