Main Terrain is a surprising place. The new urban art and fitness park opened to the public last week on the west end of Main Street. And if the surprise of finding steel bridge trusses 25 feet above your head isn’t enough—hand crankable to spin 360 degrees, no less—maybe creating such a park from a 1.7-acre strip of land mostly surrounded by buildings in the middle of a block on the Southside is. Need more? Add to that the idea that one tiny place can combine open space, public art, fitness and stormwater management, then consider even more surprises.
According to Christian Karkow of the multi-discipline design firm Clearscapes, which designed and fabricated the sculptures:
- Steel for those bridges fit in the back of a pickup before they were assembled;
- The design team created only one-and-half blueprints for the three pivoting bridge elements; and ...
- If you line the bridges up at night, they won’t be aligned the same way the next morning.
The idea of looking for surprises in this project started when Peggy Townsend, director of Public Art Chattanooga, listed a few unexpected turns the project took.
Early on, the planning team was focused on sidewalks, she said. Landscape architect Mike Fowler wanted to look instead at this one block stretch of former rail right of way. The 1994 Southside plan, which first began formally imagining something besides blight south of TVA, tagged it as a possible greenway, but it was still mostly overgrown.
When the development team began interviewing artists, Thomas Sayre—co-founder of Clearscapes, the firm that eventually won the contract—told planners they had the wrong idea for the art. Instead of using the land like a gallery for five distinct pieces of art, he proposed a unified work in several pieces that bridged the site, both literally and metaphorically, said Townsend. PlayCore’s role designing adult fitness equipment to the park was also not part of the original plan. The firm began as a safety consultant for the active art, but got so excited by the developing plans that they volunteered to create a new line of adult fitness equipment. PlayCore worked with Get Built, a CrossFit gym less than a block away on Main Street, to develop all-hours outdoor equipment that mimics activities in the workout studio—climbing, squatting, jumping, hanging.
Clearscapes’ Karkow worked most intimately with the making and assembly of both the steel bridge trusses and the cast-concrete pylons that support them. Asking him about surprises in the creation of these sculptures leads to a flood of insights.
He was surprised by how little space the three unassembled bridge elements occupied. The pieces were cut from steel sheets by an industrial water-jet cutter. (Imagine a home pressure washer with the water pressure cranked really high, abrasive material added, and the spray honed to a tiny cutting stream—like a laser, only with water.) “It all came on two or three little pallets. My pickup truck was [surprisingly] light getting it from the cutter,” he said.
The shapes of the assembled bridge trusses are reminiscent of the Walnut Street Bridge, but they twist in a way no real bridge ever would. The steel “camelback trusses” of the walking bridge look like boxes, with a floor, two walls and an irregularly shaped ceiling. The bridge pieces of Main Terrain start out as triangles and then twist in the middle. As a result of that spiraling twist, according to Karkow, “I made one and a half bridges out there. I thought I was making three.”
He explained that the bridges on both ends are identical, mirror images of each other. When they are lined up to make the ideal bridge shape, the outside ends taper to a point and the inside ends look like triangular cross sections ready to connect to the middle piece.
“The bookends are identical, the one in the middle is unique. The one in the middle, though, is bilaterally symmetrical. Starting at one end of the piece, it’s identical, a mirror image of what’s on the other side,” with a spiraling twist in the middle, he said.
“So what I did was I made one-and-a-half bridges times two,” he added. “It just worked out that, magically, with this mirroring effect of the spiral, all I had to do was go from the end of one to the middle of the second and it would finish itself.”
But all is not symmetrical. “Line the bridges up at night,” he pointed out, “and you’ll probably use the lights on the top. They won’t be aligned in the morning because the geometry of those shapes is different from how the red lights line up. I was going to put the light dead center on the back of the two tails, but it didn’t feel right. So we just said, let’s make it look right and people will figure out their own version.”