The front gate of the Jardine water filtration plant — one of Chicago’s main potential terrorism targets — was malfunctioning for months this year, raising security concerns among some law enforcement officials.

The Chicago Sun-Times also has discovered a disturbing example of an unauthorized civilian who managed to get past the main vehicle checkpoint for the city’s filtration plant near Navy Pier.

On June 13, security officers at Jardine stopped an Evanston man with a history of trespassing, police said. The man admitted he sneaked onto the restricted property in his car. He tailed an authorized truck through the checkpoint, parked, and walked up to a building where he was detained, police said.

The 45-year-old man wasn’t arrested. The security gate apparently was working at the time, police said.

One law enforcement source said he’s heard of multiple examples of unauthorized civilians entering the Jardine facility this year.

Sources said the malfunctioning gate and the June trespassing incident are both alarming. That’s because the facility is a potential target for terrorists who might want to contaminate the region’s drinking water. Also, lethal chemicals stored at the facility could create a deadly hazard if released into the atmosphere.

But Gary Litherland, a spokesman for the city’s Department of Water Management, insisted “the security of Jardine has not been compromised in any way at any time.” 

“As anyone can see by walking or driving near the entrance of the plant, the gate is not the only security measure in place at that location. Security guards are also stationed at the entrance around the clock. Beyond that we will not discuss the details of our security plan,” Litherland said.

Asked how long the gate wasn’t working, Litherland responded: “The issues with the gate have been intermittent for the last few months.”

The gate, installed in 2003, was suffering from “normal wear and tear,” he said, adding that the vendor paid for the repairs.

Citing security issues, Litherland didn’t respond to questions about the exact problem with the gate. He also didn’t explain why the gate took months to fix.

Concerns about the vulnerability of Chicago’s water system date back to the terrorist attacks of Sept. 11, 2001. At the time, City Hall temporarily evicted private contractors from Water Management facilities. The ban continued for weeks, long enough for criminal background checks on more than 2,200 people with access to secure areas.

The Department of Water Management also replaced a former fork-lift driver with a retired Chicago Police deputy as in-house security chief, hired a private security company to assist Chicago Police officers stationed at Jardine and hired a private consultant to plug security leaks.

One secret report concluded that an attack on a chlorine truck entering the Jardine facility could create a catastrophe downtown.

In 2007, a private security company’s unarmed guards were removed from the Jardine and South filtration plants and replaced with city employees serving as watchmen. The changing of the guard came after surveillance cameras captured dozens of instances in which the company’s guards were sleeping on the job or absent from their posts.

The latest questions about security at Jardine come as Mayor Rahm Emanuel called Tuesday on mayors in the region to convene a summit to protect the Great Lakes in the wake of a recent water crisis in Toledo where residents were instructed not to drink tap water.