She shields herself from the cold with a sweat shirt and jacket, along with a pink hat and gloves she bought at the 99-cent store. Only a barking dog interrupts the silence.
Rivas arrives at the first house, lifts the trash can lid and shines her flashlight inside. Nothing.
"No hay. No hay," she says in Spanish.
She peers into another trash can. Nothing. She zigzags back and forth across the street, stopping at each house to search for aluminum cans, glass bottles, plastic containers, anything she can exchange for money at the local recycling center. She reaches inside and shakes the contents, listening for the telltale clink of a beer bottle or the hollow tap of a milk carton. Nothing.
She starts to feel anxious. Her husband and four children are depending on her. The $2,300 rent check on their Pasadena home is due in one week. She already asked for an extension on the gas. The cable and the phone have been disconnected.
She speeds up the pace. The plastic bags attached to the cart swoosh against one another. The wheels rattle as they roll over pebbles in the street.
A few minutes later, she finds an empty Sierra Mist can, a few plastic water bottles and several Foster's beer bottles. She dumps them into her empty cart.
"There are bad days and good days," says Rivas, 48.
As she walks toward the next house, she says, "It's going to be a bad day."
Rivas knows what people think, that she digs through her neighbors' trash to make money for drugs or alcohol. She knows what people call her -- scavenger, digger, thief.
"There are people who look at me like, 'You aren't worth anything. You aren't anybody,' " she said.
For 13 years, she says, she has collected cans and bottles "to pay my rent, my bills. I do it out of necessity."
She has looked for more stable jobs, including cleaning offices at night. But nowadays, more companies are asking for immigration papers, papers she doesn't have.
Besides, scavenging pays OK, she says. The more hours she puts in, the more she earns. Her proof is in her recycling center receipts: Oct. 22: $70.12. Dec. 12: $143.08. Jan. 4: $134.91. Overall, in a year she might earn between $20,000 and $25,000. Combined with what her husband earns and what her children contribute, they can meet the rent and put food on the table.
Rivas is part of the expanding underground economy -- the hundreds of thousands of immigrants in Southern California who clean houses, mow lawns and wash dishes, making money at the margins and paying few if any taxes. Her story mirrors the contradictions that make illegal immigration such a flash point. She broke the law getting here and drains a municipal resource staying here. Yet she works hard, very hard, so her children won't have to do the same.
Every weekday, she wakes at 2:30 a.m., knowing that even an hour more of sleep means less money. She walks miles and miles, even when it rains, even when she is battling the flu.
"If I miss one day, I'm short," she says.
Her only company is the Spanish-language DJ El Piolin, Eddie Sotelo on KSCA-FM (101.9), who entertains her through a hand-held radio one of her sons gave her two years ago.