The board held its final public hearing on the Watsonville-based Granite Construction's appeal of a decision by the county planning commission last year to deny grading and zoning permits for the 414-acre Liberty Quarry.
The supervisors, however, will not vote on the appeal until a third meeting this week or next.
About 1,600 people from both sides of the issue showed up at the hearing held at the Riverside Convention Center to voice their concern.
Proponents said it sends a pro-business message and it would mean job creation. Hundreds of union workers showed up to support the project.
"I need a job, and I think it would be good for the economy," said Tom Row of Costa Mesa. "There are a lot of these people who are out of work. They need work."
Opponents, including a band of Indians and residents near the proposed site and residents say it would adversely affect the area.
"It would damage the quietness of the community," said Christine Assad of Fallbrook. "It would not be the peaceful town that I moved to."
Gary Johnson of Granite Construction, the company that wants to open the quarry, says that's not true.
"People in Temecula are not going to see it, they're not going to feel it, they're not going to hear it, they're not going to be adversely affected by it," Johnson said. "The county will require air monitoring that with be done by South Coast Air (Quality Management) District. All the environmental stuff is covered. Now it's important that we start doing things to start putting people back to work."
Still, opponents like Temecula Mayor Chuck Washington say it could damage tourism in the area.
"They're costing a lot more jobs than they're creating," Washington said. "The negative impacts are in the hundreds of millions of dollars."
About 100 direct jobs and nearly 200 collateral jobs would be created by the project, according to Granite. Planning commission staff estimated the quarry would add about $341 million annually to local government coffers.
Granite Construction is seeking a 75-year operating window, during which it plans to remove an estimated five million tons of construction-grade aggregate -- gravel and sand -- from escarpments just north of the boundary separating Riverside and San Diego counties, east of the Santa Margarita Ecological Reserve and west of Temecula, adjacent to Interstate 15 and Rainbow Valley Boulevard.
City News Service contributed to this report.