A Recipe for Cleaning Up Toxic Soil: Chicken Manure, Potato Waste, and Straw
UMATILLA, ORE. — The Umatilla Army Depot started out as a place to store plain old explosive ordnance. Nothing fancy - just iron bombs, rifle ammo, and the like.
During the 1950s and '60s, workers here cleaned out explosive materials (TNT and RDX) with hot water and steam. The polluted water was allowed to run out into two lagoons where - scientists thought at the time - natural soil filtration would take care of the problem.
Instead, the concentration of chemicals turned the water pink and the ground into a major Superfund site.
To clean up the mess, the Army, the Environmental Protection Agency, and Oregon state agencies hired Bioremediation Service Inc., a company based in Portland, Ore. And just as the problem was relatively low-tech, so is the solution.
The contaminated soil is scooped up, mixed with "amendments" - chicken and steer manure, potato waste, and straw - and piled in windrows inside temporary buildings. There, where natural composting generates a temperature of 160 degrees F, microorganisms go to work.
Thirty days later - presto - toxic soil has become organic material clean enough to grow chrysanthemums, carrots, squash, and native grasses. At least that's what careful testing here has shown.
"It's been rearranged back into a natural humic substance which is benign and is part of every field," says Charles Bird, who runs the operation here at Umatilla.
The process appears to be a success. The cleanup is a year ahead of schedule and far cheaper than separating and incinerating the explosive residues would have been.
The main drawback is the "definite barnyard smell," Mr. Bird cheerily notes as he takes a visitor around. On anybody's olfactory-offending scale, it's up there with a pulp mill or a pig farm. But supporters of the process say the odor is temporary and a small price to pay for cleansing the soil.