For those who want the project to go ahead, the hearing is likely their last chance to have their voices heard.
"It is time to do the right thing. The right thing to do is to approve this project because we need it. We really need it very bad," said Julio Marroquin of Riverside.
But opponents say the mining operation would not create the jobs as promised. Instead, they believe dust from the operation would harm their health and kill the region's thriving wine industry.
"I don't know how they can decide that this is a good location for this project directly up wind from the Temecula Valley and hundreds of thousands of people that live in the Temecula Valley," said Cindy Myers.
"It's just the wrong project in the wrong place," said Kathleen Hamilton of Save Our Southwest Hills. "Any job that was generated by Liberty Quarry would simply be a shuffle of jobs from some place else, that would be no new jobs."
The project is near territory of the Pechanga Band of Luiseno Indians, who say the land is sacred.
"It's a huge challenge for us because there is only one creation site, absolutely only one, this is it. If it is destroyed, there isn't another one to replace it," said Mark Macarro, tribal chairman from the Pechanga Indian Reservation.
It's a battle that is nearing the end. Granite Construction is making its final appeal to the Riverside County Board of Supervisors in the hope of reversing an earlier decision blocking the proposed quarry. A permit would have allowed the company to mine up to 270 million tons of material used in concrete and road building.
Gary Johnson, the aggregate resource manager for Granite Construction, presented the appeal before the board of supervisors in a meeting that was expected to last all day.
"We need to do whatever we can in California, particularly the Inland Empire, to try to put people back to work, and investing in our economy and doing it in a manner that is environmentally sensitive is the way to do it," Johnson said.
Because there was such a long list of speakers signed up to go before the board on Monday, a second meeting was scheduled for Feb. 6.