A federal judge’s ruling keeps alive a lawsuit accusing Chicago’s Department of Water Management of creating “a hostile and abusive work environment” that uses violence, intimidation and retaliation to deny African-American employees promotions, transfers and overtime.

In a ruling issued late Thursday, U.S. District Judge Joan B. Gottschall denied the Emanuel administration’s request to dismiss the explosive lawsuit with potential to cost Chicago taxpayers millions of dollars in damages.

“Plaintiffs here alleged that the city’s mayor has acknowledged that a ‘deeply ingrained culture of racism existed in the Water Department.’ That is no threadbare allegation,” Gotschall wrote in her ruling.

“It permits a favorable inference for plaintiffs that, if the mayor knows this, final policymakers may as well.”

The judge noted that each of the six named plaintiffs –– four current and two former Water Management employees, all African Americans — has alleged “specific experiences consistent with the mayor’s description” of the department at the center of the Hired Truck and city hiring scandals.

She further noted their second amended complaint includes “well-pleaded allegations” that the named plaintiffs were “subject to racial epithets and regularly encountered hangmen’s nooses and other badges of racism in Water Department facilities.”

“Though the city would have the court disregard them, it is reasonable to infer that the general descriptions of systematic denials of overtime, promotions and desirable schedules result from the plaintiffs’ observations in many years at the Water Department,” the ruling states.

“Seen cumulatively and with inferences favorable to plaintiffs, these allegations weave together into a cognizable government policy. Add to all of this the allegations that, with favorable inferences, the city received numerous grievances of these matters and a plausible inference can be drawn that city policymakers knew of the widespread practice in the Water Department and acquiesced in them until 2017.”

Law Department spokesman Bill McCaffrey refused to comment, citing pending litigation.

Plaintiffs’ attorney Victor Henderson said the next logical step is to convince the judge to certify the lawsuit as a class action.

Henderson called Thursday’s ruling “significant and monumental.”

“It means these African-American plaintiffs who have told a common and consistent story get to continue to have their day in court,” Henderson said.

“If the city had had its way, the complaint and the concerns of these African-American workers would have been disregarded and dismissed.”

Although class-action certification is a high legal hurdle –– and for good reason –– Henderson boldly predicted that he would clear that hurdle “based on the consistency and commonality” of the claims made by “black workers over the years, combined with what the mayor has acknowledged.”

Last year, a housecleaning triggered by racist, sexist and homophobic emails swept out Water Management Barrett Murphy and his high deputies William Bresnahan and Paul Hansen. Several other high-level supervisors followed them out the door.

Veteran City Hall insider Randy Conner, who is African-American, replaced Murphy and was given carte blanche to clean house.

Sources said it was during the course of an eight-month-long investigation into allegations that Hansen was using his city email account to sell guns that Inspector General Joe Ferguson stumbled upon the hate-filled emails that triggered the housecleaning.

In a follow-up report, Ferguson said a high-ranking deputy – whom sources identified as Hansen – called African-Americans “wild animals” and sent an email with the subject line “Chicago Safari Tickets” to multiple high-ranking Water Management colleagues.

“If you didn’t book a Chicago Safari adventure with us this 4th of July weekend, this is what you missed,” the email states, listing the number of people shot in Englewood, Garfield Park, Austin, Lawndale, South Shore, Woodlawn and other neighborhood plagued by gang violence.

“We guarantee that you will see at least one kill and five crime scenes per three-day tour. You’ll also see lots and lots of animals in their natural habitat.”

Yet another email with the subject line “Watermelon Protection” included the image of a Ku Klux Klan robe on a stick in the middle of a watermelon patch.

Earlier this year, nearly two dozen current and former Water Management employees complained that the same hate-filled culture persists, even after a white commissioner was replaced with an African American.

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