To provide a cleaner waterfowl feeding ground in the midst of an area contaminated from historic mining operations, the U.S. Army Corps of Engineers, Seattle District, recently finished transforming agricultural lands into wetland habitat at a privately owned farm east of Lake Coeur d’Alene, Idaho.
The pilot project in the Lower Coeur d’Alene Basin, known as the Schlepp Agriculture-to-Wetland Conversion project, was overseen by the Environmental Protection Agency in conjunction with U.S. Fish and Wildlife Service, Ducks Unlimited and the Corps, which was responsible for executing construction.
Located within the Bunker Hill Superfund Site, an area with high levels of contaminated soil from a century of Silver Valley mining operations, the Schlepp project involved converting nearly 400 acres of private farmland into wetland habitat, providing waterfowl a cleaner alternative to feeding sites contaminated with lead and other heavy metals.
Named for the land owner, Michael Schlepp, who allowed the EPA to convert his property for conservation purposes, the project is significant since many wetlands in the lower basin contain lead at concentrations higher than 1,800 parts per million (ppm), a level studies show is fatal to birds that ingest soil during feeding. The FWS estimates that approximately 150 birds die each year in the lower basin from ingesting contaminated soil.
The multi-year project was divided into two segments, the east and west fields, with the goal of lowering average lead concentrations below the EPA’s Bunker Hill Record of Decision cleanup level of 530 ppm for protection of waterfowl.
Work on the east field was finished in 2007 and the west field, which was being used to farm wild rice, was completed in November 2011.
“The west field was more contaminated and more complicated because we were turning an active rice field into a wetland,” said Amy Baker, the Schlepp conversion project manager for the Corps. “It was historically a wetland converted for farming, so we had to bring it back to its natural state.”
Cleanup techniques at the site varied, dependent upon contamination depth. In areas where contamination was relatively shallow, limited to the upper six inches, soil was removed and deposited in an on-site ditch, capped with clean soil and vegetation.
In places where contamination was deeper than six inches, workers used a selective handling technique, flipping and burying contaminated soil beneath cleaner lower levels.
Confirmation soil samples were then taken to insure that the top six inches held lead concentrations below 530 ppm, before seeding the land with wetland vegetation and grasses meant to attract migrating birds to the area.
“The actual achieved average was 288 parts per million, well beneath the goal, but more importantly we cleaned up a portion of the Bunker Hill site so birds have a cleaner place to feed,” Baker said.
The $3 million agriculture-to-wetland project was funded by EPA settlements with Coeur d’Alene Mining and the Asarco bankruptcy settlement.
Although the west field is only recently completed, migrating waterfowl have returned to the east field, dotting the new wetlands on Schlepp Farm and seemingly approving of the new habitat.