The Senate approved a bill late Wednesday night giving municipalities the option to negotiate project labor agreements for public construction projects.

The permissive language, which allows labor unions to negotiate working conditions, was added to a bill allowing construction companies to both design and build highway projects.

PLAs are pre-hiring agreements that cover the terms and conditions of a construction project. Proponents of the agreements argue that they ensure work and safety standards and facilitate the timely completion of projects.

However, others say the agreements favor labor unions at the expense of non-union contractors.

The legislation comes four months after a Supreme Court decision allowed Electrical Contractors Inc., a non-union company, to sue the Hartford Board of Education. The contractor had won a bid and declined to sign a PLA to build two schools in Hartford.

The Supreme Court decision opened the door for future litigation against communities that called for project labor agreements. However, the bill the Senate passed puts into statute the option to require PLAs.

The bill was expected to be controversial with a debate lasting until Thursday morning, but even senators wary of project labor agreements seemed comfortable with the permissive nature of the bill. It passed 32-3 after around 90 minutes of debate.

Sen. Edith Prague, co-chairman of the Labor Committee, said the decision to require an agreement will be at the discretion of the community funding the project. Communities can decide to require a PLA if they determine the agreement will have direct or indirect economic benefits, she said.

“How many community people would be employed, how well the project would be handled, the issue of getting the project done on time so there will be no cost overruns,” she said. “Those are all benefits to the community.”

The bill received the support of two of the Senate’s conservative Republicans on the grounds that it permits PLAs but doesn’t require them. Sen. Len Suzio, R-Meriden, said his town was looking to build two high schools. He said PLAs have become a hot topic there.

Suzio said he likes that the bill gives towns the ability to make decisions about their own projects.

“There’s nothing coercive about this legislation. It’s permissive,” he said.

Sen. Michael McLachlan, R-Danbury, said it’s a common perception that projects that use PLAs are more expensive than projects without them. However, the bill’s fiscal note doesn’t anticipate any financial impact because communities would already be required to pay prevailing wages for any project where a PLA might be used.

McLachlan said he was supportive of the bill because of the underlying design-build proposal.

“Design-build is a best practice of corporate America and has been for years,” McLachlan said, adding in most cases it’s the best way to get to the finish line on a construction project.

He was a little unsure about the project labor agreement portion of the bill, but supported it because towns would not be required to use them.

“That tells me that if that information that we’re assuming tonight is incorrect, then the PLA gets kicked aside in favor of other alternatives,” McLachlan said.

Jim Finley, executive director of the Connecticut Conference of Municipalities, said the bill gives municipalities the option of “determining” whether to use a PLA for any school construction project that’s more than $10 million. He said it’s problematic because it ties the determination to the size of the project and it’s unclear who in a town would be making the determination. He concluded it could lead to further litigation.

Gov. Dannel P. Malloy, a former mayor, said he’s been a supporter of PLAs.

“At a time when too many people in our state are still searching for gainful employment, project labor agreements ensure that we have the best trained workforce in place for our more important projects,” Malloy said in a statement.

But Lelah Campos, president of Associated Builders & Contractors of Connecticut Inc., said non-union contractors account for 80 percent of the construction trades in the state and she pointed out that 12 states have banned them. Campos further argued that PLAs increase the cost of any given project by at least 20 percent.

Malloy, who was aware of opposition to the bill from non-union contractors, said “this is not another unfunded government mandate.” And he lobbied for the legislation.

“All this bill does is give municipalities the option of entering into a project labor agreement if they choose to do so, without the added risk of costly litigation,” Malloy said. “It’s just a common sense measure, one that will ensure that the hardworking men and women in the building trades can find employment that will support their families.”

The bill now heads to the House.

Christine Stuart contributed to this report