Super Mulch Researchers Hope Mixture Of Human Waste, Wood Ash Will Help Bunker Hill Bloom Again

Nothing lives in the mounds of mine tailings that stretch for miles along Interstate 90 at the Bunker Hill Superfund site.

But a team of researchers spent Saturday trying to jump-start life here with a mysterious cocktail of wood waste and sewage.

If successful, the biochemical compound could be the first step toward revegetating thousands of acres of barren hillsides in the 21-square-mile site.

The goal: After several years, hillsides flush with plants and erosion-controlling trees will harness toxic metals that contaminate area rivers and streams during runoff.

“Everybody knows if you plant grass and it grows, the soils will stay in place year after year,” said Don Keil, a city of Coeur d’Alene sewage worker who is helping the researchers. “That’s what we’re hoping happens here.”

The project is one of two the Environmental Protection Agency will study to determine how best to regenerate 1,000 to 3,000 acres of scarred earth.

The federal agency had hoped to begin a multimillion-dollar replanting project next spring, and is expected to choose from among the two research projects.

The second pilot project, by a Montana company, was performed earlier this year. Those researchers took a more traditional approach to seeding, using a base of lime to reduce the acid that can leach from metals in the soil and kill plants.

Saturday’s project - spearheaded by a U.S. Department of Agriculture scientist with help from regional universities and an association of wastewater treatment plants - used byproducts of human waste and wood ash from power plants.

In plots of ground measuring four meters square, the group mixed the waste and ash into batches and planted wheat grass and legumes.

The purpose: to see which batch creates a new soil rigorous enough for plants to grow atop slag heaps.

“Most of the hillsides are barren because the acid in the metals killed the plants,” said Chuck Henry, a soils professor with the University of Washington.

The waste - called biosolids - produces needed nutrients for plant life. Wood ash neutralizes the acid and provides a porous surface for moisture to get in.

“In tandem, it’s a really good combination,” Henry said.

When the acid in the soil is neutralized, “the metals are still there, but they’re just in a form that the plants can’t access - they’re sort of locked in a vault,” Henry said.

This approach has been used extensively in coal mine reclamation on the East Coast, said USDA soils researcher Sally Brown.

It also was used in the cleanup of a zinc smelter in Palmerton, Pa., in 1991.

“It was so successful they were asked to expand it to a larger area,” Brown said.

Simply learning when to plant the seeds is equally complicated. Biosolids produce ammonia that prevents seeds from blossoming fully.

The researchers are measuring “how long the grass stays, how thick it grows, how tall and vigorous,” Henry said.

These researchers contend their approach is better than the Montana company’s because lyme reduces acid from metals only temporarily. The wood ash can reduce the acid for “hundreds of years,” Henry said.

But treating soils with biosolids could cost $4,000 an acre - about 30 percent more than lime-based soil.

It’s not clear when the EPA will make a decision. But the researchers say the agency is moving quickly.

“On a government time scale, this has happened in a lightning bolt,” said Dan Thompson, president of the Northwest Biosolids Management Association.

, DataTimes ILLUSTRATION: 2 photos (1 color)