Ancient architecture that takes a pounding

For the last couple of months, Robert Horner has been packing dirt.

It’s not the usual activity for an artist or architect, but for Horner, who is both, it’s an integral part of his latest work: “Tidal Resonance Chamber,” a public art piece that combines science, sculpture and engineering, along with a respect for the work of the building it stands next to, the Center for Urban Waters.

Both building and artwork will be opened this Thursday by Gov. Chris Gregoire.

“The ‘Chamber’ is a frame or window into the condition of Commencement Bay prior to the industrial era,” Horner says. “It’s a contemplative, relaxation space that invites questions.”

Philosophically, that’s what the “Tidal Resonance Chamber” is. It’s a walk-in platform surrounded by freestanding 8-foot walls and overlooking a 2,500-gallon in-ground tank filled with water straight from the Thea Foss Waterway; as the tides ebb and flow, it connects viewers to natural rhythms and the health of the environment.

Practically, however, “Chamber” represents something new to Tacoma and Washington state: Its walls are constructed of rammed earth, a building technique that compresses a topsoil-cement-lime-chalk mixture into a solid, weight-bearing wall.

Rammed earth is an ancient building technique: It dates back to Neolithic times in China, and was popularized in the 1800s in the United States for houses and churches. But it’s more common in hot climates (Texas, Arizona, as well as Australia) where the thick walls give excellent insulation from heat and where the mixture can dry quickly.

For Horner, though, the technique is attractive on a number of levels. One is sustainability.

“We use earth from local quarries and construct the walls right here on site,” explains Horner, who is collaborating on the project with rammed-earth builder Bly Windstorm of Earthdwell LTD, based in Port Townsend. “It cuts down on the energy used by around a half.”

After mixing the earth with a bit of Portland cement for strength and iron oxides for color (Horner isn’t using onsite material, as it’s toxic and unsuitable for walls), the earth mixture is shoveled between heavy-duty plywood/aluminum forms to make the shape of the 12-inch-thick walls, strengthened by vertical and horizontal rebar. Every 6 inches, the earth is rammed down with a pneumatic tamper – like a drill with a flat, circular end. There’s hardly any waste, as Windstorm reuses his forms for every job.

The final result is a gorgeous, earth-toned surface of red, ochre, brown and orange strata, softly grainy to the touch – another reason Horner likes working with it.

He’s also designed the chamber’s five walls to be on a human scale: “Just big enough to surround you, but not too high to cut out the light.”

And the end product is – to the surprise of city engineers – incredibly strong.

“When I first applied for the permit, the City laughed at me,” says Horner. “There were lots of hurdles.”

Jon Kendall, the city building inspector, agrees.

“I had never seen rammed earth before. But it tested at extremely high strength, around 6,000 psi. (City codes require at least 2,000 pounds per square inch.) It was a learning experience for all of us. Our biggest concern is that it’s durable – the cement content is pretty low, and we don’t know how it will stand up to the salt air down there. But we’re very satisfied. It’s a beautiful structure, though very labor-intensive.”

The other component to the Tidal Resonance Chamber is science. Built with the 1-percent-for-art set aside from any public construction budget, “Chamber” not only sits right next to the city-owned, University of Washington-managed Center for Urban Waters, but references the work the Center does on water health. As the chamber’s tank fills each day with Foss water (pumped through a filter to avoid trapping fish), it in turn feeds microscopic life and plants that Horner hopes will thrive there, and reminds viewers that the Foss is a living, breathing entity.

“People need to realign themselves with natural rhythms like the tides and the planets,” says Horner. “Before we can change bigger issues like climate change we have to change our attitude, (and realize that) we’re part of the system. It’s changing, and so are we.”

Rosemary Ponnekanti: 253-597-8568