SAN DIEGO -- The Chargers and leaders of the San Diego Building and Construction Trades Council announced today that they've reached a project labor agreement for a proposed downtown stadium and convention center annex.

PLAs spell out terms for employing workers on a major project, such as compensation and hiring local tradesmen.

Supporters of such arrangements say PLAs ensure quality work and labor peace, usually meaning a job will be completed on time. Opponents contend they effectively shut out non-union shops and increase a project's price tag.

The council, an umbrella group for construction unions, also announced its endorsement of the team's proposed ballot measure, which would help fund the project. The Chargers have scheduled an event Saturday to launch a signature-gathering drive to qualify their initiative for the November ballot.

"It's not just about building -- we all build -- it's about the community," said Tom Lemmon, the council's business manager.

"We have the highly trained, skilled workforce that is going to do this project right, on-time and on-budget," Lemmon said. "The Chargers made the agreement to the (PLA) to make sure there's local hire, and opportunities for apprenticeship in the future, so folks are going to be able to get into apprenticeships and earn really good pay as a construction worker."

He estimated that the stadium-convention center annex project will employ several thousand people in the building trades.

Fred Maas, who is leading the Chargers' stadium effort, said the franchise is labor-friendly, and players belong to a union.

"I think it's an important statement about what the team represents and what we're committed to and what we expect at our new facility," Maas said.

The Chargers' signature drive begins at 11 a.m. Saturday at a parking lot at 13th and K streets in the East Village. National Football League Commissioner Roger Goodell, Chargers Chairman Dean Spanos, quarterback Philip Rivers and former running back LaDainian Tomlinson are among those scheduled to attend, according to the team.

Lemmon said several hundred union members will also turn out to the event.

The Chargers need around 67,000 valid signatures to qualify an initiative for the November general election ballot that would, if passed, raise the city of San Diego's hotel room tax to 16.5 percent to pay for construction of a $1.8 billion complex.

The tax is currently 10.5 percent, with an additional 2 percent fee that pays for tourism promotion, making the increase effectively 4 percent. The initiative would require two-thirds voter approval because of the tax hike.

The Chargers have pledged to chip in $350 million of their own money and use a $300 million loan from the NFL.

Team officials invited city residents to attend the event to learn more about their plans, register to vote and sign the petitions. The event will also include food and live music.

The Chargers have been asking for a replacement to Qualcomm Stadium for around 15 years. In January, NFL owners rejected their plans to build a playing facility in Carson in Los Angeles County jointly with the Oakland Raiders, after which Spanos announced he would give San Diego another try.

Spanos said he has an agreement in place to have the Chargers become the second team in a future Inglewood stadium, along with the Los Angeles Rams, if the San Diego effort falls through.