Final Site Information Package for National Remedy Review Board ...

SITE INFORMATION PACKAGE FOR NATIONAL REMEDY REVIEW BOARD
PART B, SECTION 1: SITE NAME, LOCATION, AND BRIEF HISTORY
Information Package, the FFS Report, and the forthcoming ROD Amendment extends
approximately 1 mile to the west beyond the confluence of the SFCDR and the North Fork
of the Coeur d’Alene River. Figure A-2 provides a map of the Upper Basin. The topographic
relief in the Upper Basin ranges from approximately 2,000 to 7,000 feet above mean sea
level.
1.2 Mining History
The Bunker Hill Superfund Site has a long history of mining and related metals-processing
activities. Mining and smelting within the Coeur d’Alene Basin began more than 100 years
ago, and the region became one of the leading silver-, lead-, and zinc-producing areas in the
world. The area surrounding the SFCDR produced over 97 percent of the ore mined in the
entire Basin (Science Applications International Corporation [SAIC], 1993). Approximately
1.2 billion ounces (34,000 tons) of silver, 8 million tons of lead, and 3.2 million tons of zinc
were produced (Long, 1998).
The Bureau of Land Management (BLM) of the U.S. Department of the Interior identified
more than 1,000 mining or milling-related features in the region surrounding the SFCDR
(BLM, 1999). Several of the features were metals-processing facilities that were constructed
at various times, including an electrolytic zinc plant, a lead smelter plant, three sulfuric acid
plants , a phosphoric acid plant , and a fertilizer plant.
As a result of past mining, milling, and smelting practices, substantial portions of the Coeur
d’Alene Basin contain elevated concentrations of lead, zinc, cadmium, and other metals.
Within the Upper Basin, elevated concentrations of metals resulted primarily from the
discharge or erosion of mill tailings and other mine-generated waste into rivers and streams.
These water bodies, in turn, deposited millions of tons of mine tailings into streambeds,
floodplains, and shorelines throughout the Upper and Lower Basins. The history of milling
and tailings disposal practices in the Basin is summarized in Table B1-1; some significant
details are summarized below.
• Approximately 62 million tons of tailings were discharged to the Coeur d’Alene Basin
after mining began.
• Tailings were frequently used as fill material for residential and commercial
construction projects.
• Until 1968, tailings tended to be discharged directly into the SFCDR or its tributaries.
Most of the tailings were transported downstream, particularly during high-flow events,
and deposited as solid tailings or as tailings/sediment mixtures in beds, banks, and
floodplain areas. Since 1968, all mill tailings have been placed in impoundments or
returned as fill to provide structural support to active mines.
• Mining activities generated large volumes of waste rock and discharged water from
mine openings (adits) that contained high concentrations of metals.
• Particulates released to the air from smelting operations contained high concentrations
of metals. The particulates were transported by the wind and were deposited
throughout the Bunker Hill Box area. (The Bunker Hill “Box” is a 21-square-mile area
surrounding the former smelter complex.)
B1-2