Acid Mine Drainage at Idria

Acid Mine Drainage (AMD) is water drainage flowing from a mine that is acidic with elevated levels of dissolved metals. Metal-rich acidic drainage can also occur naturally in mineralized areas that have not been mined. An opinion exists among some people that the acid mine drainage at Idria is dangerous to human visitors. However, the facts show that it is no more acidic than coffee or soda pop and proffer no risk to human visitors to Idria.

Adit #10, February 26, 2005

While the AMD is harmless to Idria visitors, it has damaged the downstream aquatic environment of San Carlos Creek. The AMD water leaving Adit 10 is crystal-clear, but the pH rises rapidly causing the iron to precipitate out of solution, thus turning the water and streambed an ugly orange color. Based on historical accounts, San Carlos Creek supported greater diversity of biota 100 years ago than it does today. The years of increased turbidity, human foraging and AMD has killed or displaced some of the original biota. While we can never restore the original habitat, cleaning up the AMD would produce significant improvements in the downstream water quality.

Idria settling pond has not been maintained for over thirty years.

A quirk of nature has alleviated some of the stress caused by the AMD. The natural pH of San Carlos Creek is about eight, which is much higher than average streams. The mixing of AMD with San Carlos Creek water produce a pH of 7, which is considered normal. Of course, this causes the iron to precipitate out much faster, causing the water to look even worse, but at least, the water is no longer acidic. However, the high iron continues to distress the San Carlos Creek aquatic and riparian environment down stream north of Idria.

pH is a measurement of how acidic or basic a substance is, and is measured on a scale of 0 to 14, where values of 0 - 1 denote strong acids, and 13 - 14 denote strong bases. A pH of 7 is neutral.

Product	pH	Comment
Hydrochloric Acid	0.1	Obviously Dangerous, don't touch or drink
Sulfuric Acid	0.3	Great for lead-acid batteries – but, don't touch or drink
Rice Vinegar	1.0	Too sour for me
Lime Juice	1.8	Great with Tequila
Red Wine	2.0	Great with dinner
Lemon Juice	2.3	Necessary for lemon aide and lemon pie
Vinegar	2.4	Good on Salad or sweet-and-sour pork
Pepsi Cola	2.8	Probably drink too much of it
Apple Juice	2.9	Taste Great
Grapes	3.5	Great eating and for making wine
Mayonnaise	4.0	Can't have a sandwich without it
Ice Cream	4.0	Delicious desert
Tomato & Tomato Juice	4.2	Delicious
Pringles Salt & Vinegar Chips	4.5	Great with beer
AMD at Idria (Jan. 1999)	4.6	Taste terrible -- like water from a rusty pipe, also very sour ... in fact, it taste worst than terrible.
Coffee	4.7	The best way to begin a day
Beer	5.0	The good way to end a day
AMD at Idria (July 2007)	5.5	Still taste really bad, but pH has been steadily rising.
Distilled Water	5.6	Not as useful as distilled spirits
Normal Rain	5.7	No life without it
Saliva	7.0	Everybody has a mouthful of it
Blood	7.4	We're all full of it

Ray Tasting AMD at Adit #10 – trust me, it taste really, really, very terrible, horribly yucky bad.

Bibliography

Clermont College. Biology Department. "pH Testing Results."

Davids, Ken. "Low-Acid Coffees." Coffee Review. December 2000.

EPA "Pure distilled water would have tested neutral, but pure distilled water is not easily obtained because carbon dioxide in the air around us mixes, or dissolves, in the water, making it somewhat acidic."

Worsley School Science Experiment.