LOS ANGELES (CNN) -- On Saturday, at least 10,000 volunteers are expected to be called into action to clean up humanity's home -- planet Earth.
"The nation's largest community improvement movement," as the volunteer groups are known, will be getting their hands dirty and feet wet as they clean walkways and waterways around the United States.
In all, Keep America Beautiful -- the nonprofit group that is sponsoring the Great American Cleanup "National Day of Action" on Saturday -- has organized trash-clearing activities in nearly all 50 states, as well as special large-scale events in 10 locales.
These latter sites are Oakland, California; Los Angeles; Cocoa, Florida; Indianapolis; Cobb County, Georgia; Hampton Roads, Virginia; Houston; Shreveport, Louisiana; Philadelphia; and Nashville.
Volunteers around the country will spend the day outdoors picking up litter, planting trees and making other improvements to the natural world.
Tidying up the country isn't a matter of just "waving a magic wand," said Gale Cunningham, senior vice president of Keep America Beautiful and managing director of the Great American Cleanup. "It's understanding each person can make a difference."
"Each volunteer for one hour of work is worth $21.79, and we had 5.2 million volunteers last year" during a period from March 1 to May 1," he added. "The United States saved $113 million last year that would have otherwise paid government employees."
Last year's clean-up activities in 16,500 communities resulted in the removal of 177 million pounds of litter and debris; beautification of 177,000 acres of parks, public lands and open spaces; and planting of 166,000 trees and 1.5 million flowers and bulbs, according to Cunningham's group.
One of this year's spotlight sites is the namesake waterway of the nation's second largest city, the Los Angeles River.
Saturday's activities coincide with the Friends of the Los Angeles River's 23rd La Gran Limpieza, which translates to The Great Cleanup.
"This year we are integrated with the City of L.A. and L.A. County to compare trends and the progress being made," said Shelly Backlar, the river group's executive director.
About 4,000 volunteers are expected to help at 15 river locations over a span of three hours. Last year, La Gran Limpieza collected 25 tons of trash from cigarette butts to "river treasures," as Backlar put it, consisting of shopping carts, a hammock, a sleeping bag and a Barbie doll with dreadlocks.
From coast-to-coast, groups are relying on the volunteer spirit of the millennial generation and college students, who will go through every fifth bag of trash and collect scientific discoveries.
"There is passion for engagement and volunteerism from the millennials. They are active. It's inspiring to see," said Cunningham.
Christine Flowers, executive director of Keep California Beautiful, said Saturday's volunteer activities supplement state and local government efforts -- which cost taxpayers about $500 million a year -- to address illegal dumping and littering.
"When people get their hands dirty and get engaged, they care more for the environment and their community," Flowers said. "Volunteers learn something new and it gives them passion and fire to better the environment."