The Hannibal Board of Public Works says they're continuing to work on the amount of disinfecting byproduct in the water system.
The board wants to assure the public that the water is still safe to drink.
The BPW tests the water on a quarterly basis and sends the samples to the state. From there, it takes several weeks for the sample to be tested.
The board says part of the problem is the lack of rain and issues with the river level that could have caused part of what's going on.
Now the city is working to correct the problem.
"We are working towards clearing up the problem. We've hired an engineering firm about a year ago, and they're going to recommend probably some upgrades to our water treatment plant as well as out distribution system to solve the problem," Hannibal BPW Director of Operations Heath Hall said.
Hall says the violation levels were just over the limit and he says people would have to drink over a liter of water everyday for more then 70 years to be affected by the byproduct.