The Piedmont Housing Alliance had to take its plans for an affordable-housing development in the Fifeville neighborhood back to the drawing board after a routine environmental survey revealed the groundwater is contaminated with an industrial-strength cleaning solvent.

While the chemical, trichloroethylene, isn’t concentrated enough to require extensive clean up, the housing alliance nevertheless volunteered to take steps to protect those most vulnerable to it: the construction workers who will build the development.

The chemical is in the water table, about 3 to 6 feet beneath the surface. Workers would only come in contact with it if they were digging a foundation.

To avoid this, Charlottesville architect Bill Atwood suggested building on top of the earth. Under his plan, concrete will be poured into a weight-bearing form called a “waffle slab.” It will seal off the exposed earth at the site, which is a small block bordered by Grove, King, Ninth and 10th streets.

“We decided the way to solve that problem, which will truly make this a one-of-a-kind project … was to put down a waffle-slab grid,” he said. “It’s one of the rare times in my career that we’re actually making the site safer.”