The Mixed Legacy of 19th Century Mines

1. Which of the following benefits did the United States derive from mining activities in the American West?

A. Presented economic opportunities of “striking gold” or other valuable minerals to anyone willing to risk confronting the frontier.

B. Facilitated laws to maintain order as well as to define and document property rights.

C. Influenced the location of state lines along with the vitality and location of cities.

D. Created jobs in all sectors.

E. All of the above.

U.S. Geological Survey. Eagle River running through mining area at Gilman zinc mine on Battle Mountain, between Redcliff and Minturn. Eagle County, Colorado. ca. 1980. (Photo courtesy USGS)

2. Which of the following were negative outcomes?

A. Depleted and abandoned mines left scarred terrain no longer suitable for other uses.

B.  Abandoned mines left safety and environmental hazards behind such as unprotected mine shafts and toxic tailings.

C. Environmental impact to streams and aquifers from acid mine drainage (AMD)

D. Native Americans were driven from their ancestral homeland to reservations on land no one else wanted.

E. 19th Century miners escaped all responsibility for damage they caused.

F. All of the above.

3. Which of the following chemicals constitute AMD?

Tailings produced from a gold/silver mine on Quartz Hill, southwest of Central City. Gilpin County, Colorado. October 1992. (Photo courtesy USGS)

A. Zinc, arsenic, and lead

B. Copper, selenium and cadmium

C. Iron, aluminum, and silver

D. A & B

E. All the above.

4. How many abandoned mines are in the west?

A. 8,000 – 10,000

B. 12,000 – 30,000

C. 50,000 – 100,000

D. Over 100,000

5. How much does abandoned mine clean-up cost per site?

Different view of Eagle River running through mining area at Gilman zinc mine on Battle Mountain, between Redcliff and Minturn. Eagle County, Colorado. ca. 1980. (Photo courtesy USGS)

A. $5 million – $10 million

B. $15 million – $20 million

C. $30 million – $40 million

D. As much as $583 million

6. How many miles of Western United States waterways are contaminated by acid mine drainage from abandoned mines?

A. 1,500 miles (5%)

B. 3,000 miles (10%)

C. 12,000 miles (40%)

D. 20,000 miles (67%)

7. Who is responsible for cleaning up old mines?

A. Property owners


C. State environmental agency

D. Volunteers

E. It depends

Tailings produced from the Climax porphyry molybdenum deposit. Northwest part of the Climax quad. Lake County, Colorado. July 1992 (Photo courtesy USGS)

8. Acid mine drainage is only caused by mining. (TRUE/FALSE)

9. Which of these constitutes how AMD pollutes the environment?

A. Contaminated water drains out mine entrances and tunnels.

B. Rainfall, stream water, and snow melt come into contact with discarded ore and tailings, then enter stream and aquifers.

C. Acidity and metals are released into the environment when oxygen and water react with metal sulfide minerals.

D. All of the above.

Silver Lake Mine and Arrastra Basin; near Silverton. San Juan Mountains. San Juan County, Colorado. August 21, 1980. (Photo courtesy USGS)

10. Which group is most affected by AMD?

A. Humans

B. Aquatic life (fish, frogs, salamanders, etc.)

C. Wildlife

D. All of the above

11. The Clean Water Act helped mitigate the AMD situation. (TRUE/FALSE)


1. ANSWER E: All of the above.

The California Gold Rush of 1849 inspired thousands to make the difficult passage across the American interior with major rushes in 1859 to the areas that would become Colorado and Nevada.  Mining settlements grew into towns and then cities that offered employment in a variety of manufacturing and service industries.

Sneffels mining camp. San Juan Mountains. Ouray County, Colorado. July 16, 1972. (Photo courtesy USGS)

2. ANSWER F: All of the above

The physical and environment damage of abandoned mines goes without saying. The geographical complexities and limitations of treaties related to Indian territory resulted in numerous conflicts. Thus, the U.S. government took possession of many areas of the Northwest, the Rockies, the Great Basin, and the Southwest which ultimately sent native populations to reservations.

3. ANSWER D: Both A & B

Acid mine drainage is water that typically carries unusually high concentrations of dissolved metals such as zinc, arsenic, cadmium, lead, copper, and selenium.

Collapsing mill at old mining town of Middleton. San Juan Mountains. San Juan County, Colorado. June 30, 1972. (Photo courtesy USGS)

4. ANSWER D: Over 100,000

As of May 2019, the Forest Service, BLM, the Park Service, and EPA together identified in their databases at least 140,652 abandoned hardrock mine features—of which over 60 percent are known to pose or may pose physical safety or environmental hazards. Officials from 13 western states also identified from their state databases about 246,000 abandoned hardrock mine features on federal and nonfederal lands within their states, including about 126,000 features that pose physical safety or environmental hazards.

North fork of Clear Creek 5 km down stream from Blackhawk. Reddish color in the stream bed is due to precipitation of iron oxyhydroxides as pH increases. Gilpin County, Colorado, October 1992. (Photo courtesy USGS)

While there may be some overlap between Federal and State databases, officials estimated that there likely are hundreds of thousands of additional abandoned hardrock mine features that they have not yet captured in their databases. Of the 140,652 total features, about 89,000 features are known to pose or may pose a physical safety or environmental hazard, according to information in the federal agencies’ databases. Specifically, agencies  confirmed 7,802 features pose a hazard, of which 6,439 pose a physical safety hazard and 1,363 pose an environmental hazard; and identified 81,541 features with an unconfirmed hazard (whereby agency staff had not assessed current conditions in person to confirm the hazard), of which 60,279 may pose a physical safety hazard and 21,262 may pose an environmental hazard.

5. ANSWER D: As much as $583 million

According to EPA documents, sites with environmental hazards can cost hundreds of millions of dollars and take many years to address. For example, as of July 2019, the actual costs at the 25 most expensive mine and mineral processing sites ranged from $50 million to $583 million per site, and EPA had been working on some of the sites for over 20 years. Furthermore, agencies monitor remedies after completion to help ensure that they are achieving the desired results.

6. ANSWER C: 12,000 miles (40%)

The U.S. Bureau of Mines estimated that 12,000 miles of the waterways of the Western United States, or about 40 percent, are contaminated by metals from acid mine drainage, mostly by abandoned mines, while 180,000 acres of lakes and reservoirs are tainted by abandoned mine runoff.

7. ANSWER E: It depends.

Theoretically, the owner of a polluting mine is responsible for the water discharged from it. But regulatory agencies find it impractical to take legal action against the vast majority of private owners. Most unwittingly inherited the problem, and could not begin to pay for remediation. They are, by virtue of having little or no financial means, “judgment-proof ” should someone sue them for environmental violations. Under current legal circumstances these private owners are often inclined to leave their mines alone. Old mines belonging to such private individuals must simply wait for some third party to clean them up.

Agencies, especially those responsible for federal land, use some of their budgets for remediation. These include the National park Service, Office of Surface Mining Reclamation and Enforcement, Forest Surface, Bureau of Land Management and the Environment Protection Agency. (See below)

Federal Expenditures to Address Abandoned Hardrock Mines by Agency, Fiscal Years 2008 through 2017, in Nominal Dollars

8. ANSWER: False

Undisturbed nature can and does generate acidic and metal-laden water without the intervention of miners. In the Animas River watershed in Colorado, much of the metal contamination in the water has been attributed to natural oxidation, or weathering, of the metal sulfide deposits. However, this “background” weathering produces for the most part only aluminum and iron, the other metals having long since leached out over the eons of geological time.

9. ANSWER D: All of the above.

Corroded 6 inch steel pipe caused by acid mine drainage from gold/silver mine on Quartz Hill, southwest of Central City. Gilpin County, Colorado. October 1992. (Photo courtesy USGS)

10. ANSWER B: Aquatic life

While all are affected in one way or another, those damaged the most are aquatic life.

Only some of the dissolved metals in acid mine drainage—cadmium and lead, for example—are potentially harmful to humans. Fish, however, are much more susceptible to the toxicity of these metals. Fish have to live in the water; we only drink about two liters of water a day.

The soluble metals, however, continually pass through and are absorbed by fishes’ gills and gastrointestinal tracts. Add in the metals absorbed from the insects they eat, and it’s not hard to see how fish in AMD-tainted water are highly vulnerable to these lethal poisons. The EPA says that we humans can tolerate copper in our drinking water at concentrations up to 5,000 micrograms per liter of water, but the fish in an alpine stream can tolerate only 65 micrograms per liter.

Severely polluted streams affect all wildlife when it becomes an unsuitable drinking source and can eventually kill vegetation along its banks.

11. ANSWER: False

Surprisingly, the Clean Water Act of 1971 enacted by Congress presents an obstacle for the treatment of acid mine drainage. To clean up polluted water issuing from a mine, you must obtain a Clean Water Act discharge permit (a National Pollutant Discharge Elimination System permit or NPDES). The permit requires that the treatment you undertake will meet Clean Water Act water quality standards, which are very stringent, and that whoever attempts the cleanup will remain responsible for the source of pollution in perpetuity (that could be you!). When a third party—a nonprofit organization, community group, government agency, or corporation—attempts to clean up acid mine drainage coming from an abandoned mine, that third party legally assumes liability for the mine’s discharge.

Another risk to such “Good Samaritans” can come from citizen groups, especially environmentalists, who oppose any laws which allow an exception to or variance from the standards and provisions of the Clean Water Act. Under the law, citizens are allowed to bring a suit to force a mine operator to meet the strict water quality standards laid down by the Clean Water Act. Clearly, the high cost of penalties, remediation of the site, and long-term maintenance are formidable obstacles to any party interested in acid mine remediation.


 1. “Cleaning Up Abandoned Hardrock Mines in the West: Prospecting for a Better Future,” by Patricia Nelson Limerick, Joseph N. Ryan, Timothy R. Brown, and T. Allan Comp; Report from the Center #7, published by the Center of the American West, University of Colorado at Boulder; 2006.

2. GAO-20-238, Report to the Ranking Member, Subcommittee on Interior, Environment, and Related Agencies, Committee on Appropriations, U.S. Senate; “Abandoned Hard Rock Mines:  Information on Number of Mines, Expenditures, and Factors That Limit Efforts to Address Hazards;” March 2020.