Sixteen months after the housecleaning triggered by racist, sexist and homophobic emails at the Department of Water Management, a similar scandal is brewing in another city department dominated by white males.

The Department of Aviation has been rocked by allegations of racism at the heating and cooling plant at O’Hare International Airport.

The incident reportedly stems from a culture clash between the plant’s predominantly white city workforce and the majority-black contingent assigned to do pipefitting work there by a city contractor.

Sources said a trade magazine that featured a cover photo of an African-American woman was recently posted on the break room refrigerator with the N-word written in pen across the woman’s forehead. A photo of the defaced magazine was provided to the Sun-Times.

Swastikas have also been reported at the heating and cooling plant.

Sources said outraged black employees promptly reported the incident to the Department of Human Resources and filed a complaint alleging a hostile work environment.

Newly-appointed Aviation Commissioner Jamie Rhee was described as equally outraged.

She referred the incident to Inspector General Joe Ferguson but didn’t wait for the outcome of that investigation.

Rhee has ordered retraining for the entire aviation department workforce and is reportedly considering other measures implemented by the Department of Water Management.

A spokesperson for the inspector general’s office confirmed that the incident was referred by the commissioner and that its investigators are “taking appropriate action on the information provided.”

Rhee is wildly popular with aldermen, who clashed repeatedly with her predecessor, Ginger Evans.

During her confirmation hearing in July, black and Hispanic aldermen joined representatives from Black Contractors United, the Hispanic-American Construction Industry Association and the Federation of Women Contractors in talking about how inclusive Rhee has been as the city’s chief procurement officer and how fair they expect her to be with the gravy train of jobs and contracts tied to the $8.7 billion O’Hare expansion project.

For Rhee, the racist incident is an early test of her commitment to fairness. Which is why she acted decisively to bring the hammer down.

“Discrimination or intolerance in any form will not be tolerated by the Chicago Department of Aviation,” aviation department spokesperson Lauren Huffman wrote in an emailed statement.

“We take these allegations very seriously, and immediately referred them to the proper authorities at the Office of the Inspector General. We understand that an investigation has been opened.”

Sources said the Department of Aviation has been bracing for the political fallout from the incident and instructing employees how to handle media inquiries.

Rhee could not be reached for comment on the ugly incident.

The outbreak of racism at the Department of Aviation is not surprising, given the department’s racial make-up. But it is nevertheless astounding in the wake of the racist, sexist and homophobic emails that Ferguson uncovered while investigating allegations that Paul Hansen, the son of a former alderman, had used his Water Management email account to sell guns.

The outrage was so swift and furious, it forced Mayor Rahm Emanuel to accept the resignation of Water Management Commissioner Barrett Murphy, even though the now-former commissioner and his wife are close friends with Emanuel and his wife, Amy Rule.

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

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.

Four current and two former Water Management employees – all African-Americans – have filed a federal lawsuit accusing the department at the center of the Hired Truck and city hiring scandals of “a hostile and abusive work environment” based on race that includes violence, intimidation and retaliation that “weave a tapestry of hostility that dominates every aspect” of their job.

That includes less-desirable shifts and work assignments and being denied promotions, transfers, overtime and training opportunities. Black women were routinely referred to as “bitches and whores,” the suit contends.

In January, 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.

The ugly testimony turned up the heat on Emanuel to settle the lawsuit.

The mayor responded by arguing that it would take a lot longer than six months to change a hate-infested Water Management culture “decades” in the making.