Tijuana artist Alfredo "Libre" Gutierrez recently finished a mural that adorns the entrance to Los Sauces park in Playas de Tijuana.

Photo by Jill Replogle

The bottles fill space inside the bench structure of rebar and concrete.

Photo by Jill Replogle

4Walls Int'l pays Tijuana residents for each plastic bottle they deliver stuffed full of plastic bags and Styrofoam.

Photo by Jill Replogle

Plastic bottles filled with trash can function as fill space inside the structure of a bench or wall.

Photo by Jill Replogle

Visitors to Los Sauces park in Tijuana can rest on benches made of trash harvested from the Tijuana River watershed.

Photo by Jill Replogle

Illegal dump sites proliferate in some of the Tijuana canyons that make up the Tijuana River watershed in Mexico. They send trash and sediment downstream, clogging the estuary and threatening birds and other wildlife.

Photo by Jill Replogle

Despite periodic clean-up efforts, the canal at the bottom of Los Laureles canyon in Tijuana frequently re-fills with trash.

Photo by Jill Replogle

The Tijuana River Valley and estuary make up the last intact coastal wetlands in Southern California.

Photo by Jill Replogle