[Environmental Outlook]
August 20, 1998

Bunker Hill: light at the end of the tunnel


Fueled by over $20 million in federal cleanup funds this year, the U.S. Environmental Protection Agency, the U.S. Army Corps of Engineers, the Morrison Knudsen Co. of Boise, and a host of other contractors and consultants are winding-up the biggest construction season ever at the Bunker Hill Superfund site in northern Idaho.

The 1998 project list included putting the finishing touches on a six-mile, heavy-duty haul road; temporarily re-routing a river; removing and disposing of more than 1.3 million cubic yards of contaminated soil; and capping & closing a 32-acre mine waste and demolition debris landfill.

How is it all being done? Well, you start with a fleet of 20 50-ton Haul-Pak trucks, two Komatsu 750 Excavators with 6.8 cubic-yard buckets, run them for two 10-hour shifts a day with the help of 180 local workers...

Silver Valley legacy: 100 years of mining and smelting waste

Mining began in the Silver Valley of Idaho's panhandle in the 1880's, with lead and zinc smelters, two acid plants and a fertilizer plant eventually being established at Kellogg. The area, known as Bunker Hill Mining & Smelting complex, ceased operating by 1983.

Bunker Hill Superfund site

Contractors and consultants are finishing up the biggest season of construction ever at the Bunker Hill Superfund site.

While they produced a significant portion of America's lead, silver and zinc during their heyday, Bunker Hill and other mining and ore processors also left behind a legacy of serious pollution in the Coeur d'Alene Basin. In addition to unleashing millions of cubic yards of contaminated slag, tailings and other mine waste to the countryside and the South Fork of the Coeur d'Alene River, mining and smelting operations at Bunker Hill were responsible for large-scale airborne lead deposition.

The impact: public health monitoring of Silver Valley children, beginning in the mid-70s, revealed the highest blood-lead levels ever recorded.

Following the site's addition to the National Priorities List in 1983, Gulf Resources -- a major Potentially Responsible Party -- declared bankruptcy. After receiving limited funds through bankruptcy proceedings, EPA turned to the Superfund trust fund to provide the resources for cleaning up the contaminated complex.

EPA later hired the Corps of Engineers to provide construction management for the project. The Corps brought in Morrison Knudsen in 1995 to demolish and dispose of over 200 buildings.

Since 1995, those buildings -- and nearly one million cubic yards of contaminated soils from the three gulches in the area -- have been buried in a 32-acre landfill that was constructed on top of the old lead smelter. As part of a 1996 Memorial Day celebration, Engineering Demolition, Inc., razed the facility's two smelter stacks (610 and 715 feet tall) with explosives.

Summer of '98: gulches, ravines and rivers

Current field work is being performed under the overall direction of the U.S. Army Corps of Engineers. Morrison Knudsen is the general contractor and Morrison Construction Services of Richland is the main subcontractor. At peak construction, the work requires 180 craft personnel, all of which were hired from the local community. Here are the highlights of the current construction season:

Silver Valley mining site

Mining began in Idaho's Silver Valley in the 1880s, with smelters, two acid plants and a fertilizer plant eventually established near Kellogg.
Photo courtesy of U.S. EPA

South Fork Coeur d'Alene River & Smelterville Flats. Morrison Knudsen is currently removing 1.3 million cubic yards of contaminated mine tailings that were deposited in an area known as the Smelterville Flats along the South Fork of the Coeur d'Alene River. The design of this removal project was a joint effort between EPA's contractor, CH2M Hill, and the State of Idaho's contractor, Terragraphics.

The project will not only help reduce further downstream damage from contaminated sediments, but will improve fish habitat by creating more pools, meanders and in-stream structure for cover and shade.

Coeur D'Alene River

The south fork of the Coeur D'Alene River was temporarily rerouted to allow for the cleanup of contaminated tailings.

To avoid making an already bad situation worse, cleanup managers decided to temporarily re-route the South Fork of the Coeur d'Alene River with the use of small dams and earth moving equipment.

Once the river was redirected away from the contaminated tailings, a new river course was established within the existing floodplain. With heavy equipment being operated virtually around the clock, workers are removing and hauling approximately 15,000 cubic yards of tailings per week.

As the tailings are removed, clean fill is being brought in to shape the new river channel. The contaminated tailings are then hauled six miles via a dedicated haul road to be permanently contained in the Central Impoundment Area, a historic mine waste dump at the site.

Tailings Disposal & Landfill Closure. The cleanup of several gulches and ravines on site has entailed removal of soils contaminated with lead, zinc, arsenic, cadmium and other heavy metals. Once areas were cleared of buildings and contaminated soils, clean material was brought in and then the area was re-planted.

Cleanup work

As the site is cleaned up and revegetated, the EPA will begin transferring the property to the State of Idaho which hopes industry, as well as native vegetation, will return.

Approximately six miles of creeks have been reconstructed, with grade control structures and check dams.

Also nearing completion is the capping and closure of a demolition debris landfill at the site of the old lead smelter. This landfill contains the remains of 200 mine-related structures demolished in previous years, and has now been capped-off with two layers of slag material, a 60 mil HDPE liner and a layer of growth media. By getting an early spring start, and thanks to superior production by the liner subcontractor, this work will finish well ahead of schedule.

The next steps

Upcoming projects will include closing the 260-acre Central Impoundment Area and installing a waterproof PVC cap to prevent future leaching. A contract for that project is expected to be advertised in January, 1999.

Bunker Hill mine

Starting in 1995, over 200 buildings have been demolished and disposed of at Bunker Hill.

Another large piece of remaining work will be to re-vegetate approximately 1,000 acres of barren hillsides. Over the next three years, various soil amendments will be applied to these hillsides in order to promote growth in the existing low-grade soils. As the site is cleaned up and re-vegetated, EPA will begin transferring the property to the State of Idaho.

It is hoped that new industry and development will occur on this reclaimed land, and that wildlife and native vegetation will soon find their way back to these areas.

After more than a century of abuse and degradation, the Silver Valley is already showing signs of renewed growth and revival after a decade of focused cleanup. Both cleanup officials and local residents hope the Summer of '98 will be long-remembered as a big step forward for both the local economy and the environment.

Mark MacIntyre is a public affairs specialist with the Seattle office of the U.S. Environmental Protection Agency.

Copyright © 1998 Seattle Daily Journal of Commerce.