AURORA | Contract negotiations between the city and the police and firefighter unions have reached an impasse.

The two unions, which are negotiating separately, had until late last month to reach an agreement with the city, but neither one did.

Kin Shuman, director of the city’s human resources department, said the two sides can continue to negotiate until early next month, but both unions and the city are now preparing for arbitration, where several previous contract negotiations have wound up.

The police and firefighters are both working under contracts that expire at the end of the year.

Aurora city council discussed the contract negotiations during a closed-door session June 4.

The presidents of both unions — Aurora Police Association President Officer Mark Finnin and Randy Rester, president of the Firefighters Protective Association — declined to comment on the ongoing negotiations.

But in a post on the union’s website last month, Rester said negotiations were at an impasse and headed to arbitration.

“We tried many times with our proposals, but the city never came back with anything that we believed the membership would vote for,” he wrote.

In a presentation posted on the union website, Rester said the union wanted 1-percent raises in January and July 2013, and again in January and July 2014. The city countered with a $500 bonus for each firefighter, and a 1-percent raise tied to a bump in sales tax revenues.

Shuman declined to discuss specifics about the negotiations, but said they were at an impasse, though he is hopeful a deal can be ironed out before arbitration next month.

“We are hoping that we can reach a mutually beneficial agreement with both the police and fire union,” Shuman said.

Beyond the contract impasse, the two unions have jointly filed suit against the city over access to data about their health plans.

Shuman said the unions’ lawsuit was the first time in his more than a decade with the city that contract negotiations have landed in court.

“It’s the first time I can recall legal action in the context of collective bargaining,” Shuman said.

According to the suit, the two unions want an independent expert to look over city employee health plans as they researched different options for their health-care coverage. City officials refused to grant the independent expert permission, so the unions filed suit.

A judge was expected to rule on the suit soon

“Depending on where that ruling comes out, we will have to see where we go from there,” Shuman said.

The firefighters are currently operating on a two-year contract, while the police union is operating on a one-year deal.

Shuman said he is open to a multi-year deal with either union.