Puente Hills is the country’s largest landfill, taking in about 12,000 tons of trash daily--that’s the equivalent of about 200 adult elephants, to give you an idea.

Paul Prestia, who oversees much of the operation, is watching the trucks as they flatten the incoming trash. A bunch of seagulls swoop around and dive into the piles, picking out a smelly snack. But Prestia? He’s a silver lining kind of guy. He’s just relishing the view.

“I used to work at waste-water treatment plants," he says, facing the landfill grounds and the valley below. "All waste facilities, be it landfills or power plants, all of them have great views.”

This is a state-of-the-art operation; a model for landfills worldwide. As excited as Prestia is about Puente Hills, he is even more excited about the new mega-landfill in the Imperial County town of Mesquite. Trash will continue to be brought to Puente Hills, but it will then be transported by train to Mesquite, 230 miles away.

“That’s the construction site for the new rail system," says Prestia, now leading a tour to the bottom of the man-made mountain. "The materials recovery facility is that building right here, and you can see we built our own road...