1. Iron Mountain Mine California Acid Mine Drainage Discharge Stuart Gaunt Guy Laurie

2. Location Iron Mountain Mine is located in Shasta County, in the state of California in the south-eastern foothills of the Klamath Mountains. Roughly 9 miles northwest of the city of Redding.

3. History of the Site Mining at Iron Mountain began in the mid 1850s and ended in 1963. The site compromised of approximately 1,800 hectares. California state record indicate that between 1888 and 1965 the mines yielded:  313 million pounds of copper  265,314 ounces of gold  24 million ounces of silver  2.6 million pounds of sulphur  Vast quantities of zinc and iron By the time mining operation ceased work in 1963, 10 separate mines were excavated on the site.

4. How bad was the AMD Discharge? The mining activity provided an effective means of both water and air to reach the sulphide deposits producing sulphuric acid and dissolving the heavy metals in the ore. The uncontrolled acid mine drainage was the largest source of surface water pollution in the United States. Accounted for 25% of the entire national discharge of copper and zinc to surface waters from industrial and municipal sources. According to EPA documents, workers once inadvertently left a shovel standing in the green liquid flowing from one of the mine portals. The next day half the shovel had been eaten away.

5. Social and Environmental Effects The pollution did not threaten the lives of the human population in the area. Many aquatic life forms downstream of Iron Mountain have struggled for survival particularly fish due to the potential contaminant accumulation. There has been a steady decline in the fish population in the area, an example being the listing of the endangered species list of the Winter Run Chinook Salmon.

6. High Runoff Storm Events High runoff storm events resulted in major releases of heavy metals. Dissolved copper concentrations in the Sacramento River reached 13 parts per billion. The river went from its normal pH value of 7.5 to 6. Acid mine drainage from Iron Mountain killed 100,000 or more fish on separate occasions in 1955, 1963 and 1964. 47,000 trout died during in a one week period in 1967.

7. Clean-up The Slickrock Creek Dam captures acid mine drainage escaping from fractured bedrock and buried mine portals along the south side of Iron Mountain. Dredging approximately 200,000 cubic yards of copper and zinc contaminated sediments from the Spring Creek Arm of Keswick Reservoir. Water Management: Capping selected cracked and caved ground areas. Diverting a number of creeks in the area around waste rock and mine tailing piles. Performing hydro-geologic studies and field-scale pilot demonstrations to better define the feasibility of controlling acid mine drainage formation.

8. AMD Discharge Clean-Up In 1992, the EPA selected an interim remedy to treat the acid mine drainage discharges by: – constructing collection and conveyance systems. – constructing a lime neutralization treatment plant. The treatment plant has been built and has been operating since 1994 and will continue, until an alternate remedy could be developed to assure meeting all cleanup goals.

9. Economic Effects (Settlement Costs) In 2000 a settlement was reached with Aventis, the principal responsible party at IMM. The total value of this settlement, for past costs and future work is over $950 million. Under the terms of the settlement, – $200 million for the first thirty years of site activities – $100 million in cost overrun insurance – a balloon payment of $514 million in 2030, which the EPA or State of California may use to fund future activities. – $8 million payment to EPA for future site costs – $10 million payment for natural resource restoration projects, such as wetlands restoration This was one of the largest settlements with a single private party in Superfund history

10. Summary EPA’s cleanup and pollution control measures have been very successful and have reduced the discharge of acidity, copper, cadmium and zinc by 95%. However, USGS scientists estimate that at current erosion rates, Iron Mountain will continue to produce acid mine drainage for 2,500 to 3,000 years, until the estimated 12 million tons of sulphide deposits remaining within the mountain have weathered away. Any Questions?