"The Arroyo Seco is a spiritual, cultural and environmental force linking the San Gabriel Mountains to downtown Los Angeles," he added.
The waterway holds an important place in regional history. "It is the reason why downtown Los Angeles is where it is," Dwyer said.
More than two centuries ago, settlers camped by the confluence of the Arroyo Seco and Los Angeles River. They needed to be near a supply of fresh water, but they wanted to stay out of the floodplain. The pueblo that grew into Los Angeles was built on a mesa just above the floodplain.
The Arroyo Seco, which begins near Mt. Wilson and meanders 22 miles to its confluence with the Los Angeles River near Dodger Stadium, is not only blighted by concrete debris, it also is choked in places with nonnative trees and vegetation.
As part of the project, hundreds of invasive trees and truckloads of exotic plants have been uprooted since fall.
Eucalyptus, palms, carob, tree tobacco, periwinkle and ivy have been torn out because they crowd out native species and provide little or no benefit to wildlife, Dwyer said.
Black willows, sycamores, coast live oaks, ferns and succulents more suited to the climate and habitat are taking their place. Trucks fitted with nozzles have blown specially blended seed mixes along the banks to aid regrowth.
Though the project is not unique -- work has long been underway to naturalize sections of the Los Angeles River -- Brick says the scope and commitment by Pasadena officials serve as an important model.
"There are groups all over Southern California who would like to do the same thing," he said.
Dwyer added: "Everybody is looking at this -- how do you get nature back into the city? I think it's one project at a time."
Don Bremner, a Sierra Club leader who hikes the area frequently, welcomes the change. "People will appreciate it more as a natural area," he said.
For Dwyer, who grew up in the area, the transformation is like creating life itself.
"When I'm in this place, I see what's really beneath the concrete," she said. "You add water, you add seeds, a little soil, a little air, and voila! What you get is nature in the city."
