The artist participated in a design team for a mile-long, six-lane overpass for the SR-51. The resulting design features six-24 foot tall, reptile-shaped support columns and 34 relief panels of human, abstract, and animal images. The panels, some as tall as 13 feet, extend up to 133 feet along the overpass retaining walls.
Zwak developed the imagery from designs on prehistoric Native American (Hohokam) artifacts found at the site during the excavation for the freeway. She surfaced the forms with adobe, a traditional southwestern building material made from dirt, clay, water, and hay. By the completion of the project, Zwak and her two assistants labored more than 4,000 hours and applied 150 tons of adobe to the overpass columns and towers.
After the major elements of Zwak’s design were in place, she invited area residents to imprint their own designs and objects in the freshly laid adobe. The variety of inlaid images and items range from hand prints, personal initials, abstract patterns and scribbles to personal mementos such as tools, keys, coins and remnants of clothing.