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City officials have completed another round of water testing after the discovery of traces of contaminants in southwest Evanston’s water supply earlier this year and a subsequent federal lawsuit against Nicor and ComEd.

Trace remnants of coal tar – a dark, viscous liquid that is a byproduct of coal carbonization – were earlier discovered on water pipes in James Park. Water samples subsequently revealed trace amounts of chemical components of coal tar in the water supply in the area around the park.

Small amounts of contaminants were discovered in five of 15 locations in the latest round of testing: Dobson Plaza Nursing Home, Dawes School, a hydrant on the 1900 block of Dobson Street, and private residences on the 200 block of Brown Avenue and the 300 block of Darrow Avenue.

City Corporation Counsel Grant Farrar stressed that in all five cases the amounts were minute, about 99.9% below the amounts that would require reporting the matter to the Illinois Environmental Protection Agency. “That’s not an imminent threat to water safety or quality,” he added.

But City officials want to know if the contamination originates from abandoned gas lines buried under James Park. Those lines, now under the stewardship of Nicor and ComEd, originated from the Skokie Manufactured Gas Plant site in Skokie, which was active from the late-19th to mid-20th centuries.

Evanston filed suit against Nicor and ComEd in federal court at the end of May to compel the utilities to produce comprehensive details about the gas lines’ locations. The utilities filed a motion to dismiss the claim and the City is preparing a response, which Mr. Farrar said he expected to be completed by September. City officials, at a June community meeting about the issue, said that state and federal authorities have been little help in the matter, since the amounts of chemicals present are so small.

Mr. Farrar said to expect additional rounds of testing, but the logistics for that had not yet been completed.

“We have a better handle on what we know and don’t know,” he added. “We will continue to prudently monitor and do testing as needed. … It’s definitely on the table as we go forward.”

The City of Evanston’s website details the testing locations and results at