"Our operator is not a chemist," he said.
After the incident, Deerfield and Highland Park staff met to hash out what went wrong. Subsequently, Highland Park offered to improve its communication by emailing and faxing results to several Deerfield employees and by more clearly offering affirmative test results.
But the switch is about more than just the miscommunication, Rosenthal said. They were pleased to find faster testing at the Lake Bluff lab, officially known as the Central Lake County Joint Action Water Agency lab, which uses a testing product called Colilert.
With Colilert, the results will be known within about 18 hours. In contrast, the method used by Highland Park takes 24-72 hours depending on the results.
"It would benefit our residents that they would know 12 to 24 hours sooner and not be drinking tainted water for 48 hours," Rosenthal said. "That's a plus."
Colilert may be faster, but the membrane filtration method used by Highland Park provides more quantifiable information about the contamination that proves useful, Jensen said.
Both tests are approved by the state Environmental Protection Agency, the state authority on water contamination, and one is not preferred over the other, said Andrew Mason, spokesman for the state EPA.
"As long as a certified lab can give a water system the information it needs to be in compliance with state regulations, communities can make choices about what lab and what tests and so on based on their local needs," Mason said in an email.
Meanwhile, Highland Park will continue to provide drinking water for Deerfield, in addition to other shared services between the two communities. But the testing relationship is over.
"It seems extreme, but they need to do what's best for them," Knapp said. "I'll sit down with (Kent Street) and we'll talk it out at some point."