Puente Hills is the country’s largest landfill, taking in about 12,000 tons of trash daily. But if Americans are buying less stuff and recycling more, do we still need mega-landfills?

The landfill in Salton City will go from being an 8-acre municipal site, to a 320-acre private one. But contamination from trash juice isn't the real concern: it's the threat of increased diesel truck traffic. There is a long-running scientific link between traffic air pollution and health problems.

About 150 miles east of Los Angeles, the the Lawson Dump is home to 40 acres of garbage that rises two stories high — a toxic collection of electronic waste, household chemicals and construction debris.