IndyCar race promoters will need approval from the feds to build a track over a contaminated waste site in South Boston, an added obstacle in the months-long effort to get the race off the starting line.

A spokesman for the Environmental Protection Agency said IndyCar and the Massachusetts Convention Center Authority, which owns the New Cypher Street land running over an old toxic waste dump, have to ensure the race course construction won’t disturb underground PCB contaminants.

“We’re still waiting for the landowners (MCCA) to submit something to us,” EPA spokesman Jim Murphy told the Herald.

Race promoters — called Grand Prix of Boston — have said they expect state environmental officials to give the green light to build the track this week. They say the plan to pave over New Cypher Street and other parts of the waste site will be safe for fans, drivers and nearby residents — a claim disputed by race opponents.

But the EPA — not the state — has regulatory control over that part of the proposed course, a ?fact race organizers have not ?emphasized.

Murphy said the waste site, an old junkyard, has been covered by a temporary cap for years, allowing the MCCA to use the land for a parking lot and New Cypher Street traffic. But any “change in use” in that land would trigger an automatic environmental review by the EPA.

The promoters plan to pave over the street and widen it, as well as build corporate suites and a pit lane in that area.

“We would consider building a race track over that and other uses a change in use,” Murphy said.

The Grand Prix of Boston has been negotiating with the city and various state agencies for months to get permits to hold the high-speed race planned for Labor Day weekend. But those talks have yet to produce a single permit, and the delays have caused concerns from investors and national IndyCar officials.

Murphy said the EPA recently told the city and MCCA they need to submit a plan soon, because approval could take weeks or months, potentially delaying construction. The EPA spokesman said it’s likely the agency would approve race track construction if the paving doesn’t disturb the ground underneath, but the MCCA and promoters need to ensure the safety of the site.

“What we don’t want to happen is for them to say we need it tomorrow,” he said.

Grand Prix of Boston disputed that they haven’t consulted with the EPA, saying their engineers and lawyers have been talking to the agency’s PCB coordinator since December, as well as the Massachusetts Environmental Protection Agency.