The list of 2011 CNN Heroes – 24 “everyday people changing the world” – includes Wilma Melville, chosen for the work she’s done in her encore career to strengthen disaster response in the United States.

After retiring as physical education teacher, Melville trained her black Labrador, Murphy, as a hobby, getting the dog FEMA-certified as a rescue dog in 1994. The hobby turned into a mission after the 1995 Oklahoma City bombing. At the time, Melville was alarmed to learn that there were only about 15 FEMA-certified canine search teams in the country. She set out to do something about it.

“We are a huge nation, and this one building alone requires far more than 15 dogs that are highly trained,” Melville remembers thinking. “Well, there’s only one thing to do. I either go back to my horseback riding in the hills, or I make a difference and find a better way to create canine disaster search teams for this nation.”

So in 1996, Melville founded the nonprofit National Disaster Search Dog Foundation (SDF). She recruited abandoned dogs from shelters, trained them to become rescuers in 11-14 months (instead of the typical two to three years), then paired them with firefighters for additional training to save lives at no cost to fire departments.

Today, the organization has trained 131 search teams around the country and responded to 80 disasters globally, including the 9/11 attacks, Hurricanes Rita and Katrina, and the earthquakes in Haiti and Japan.

Melville won a $100,000 Purpose Prize in 2007 for the extraordinary contribution she’s making in her encore career. Prize winners are people over 60 who are creating new ways to solve a range of social problems challenging our nation and our world.

Watch the video clip of CNN’s story about Wilma Melville’s work here.