Review of the Earthworks Mining Water Quality Study
What it means for the Pebble Mine project

Punchline first:
Of the mines in this study with similar characteristics to Pebble, 100% of them contaminated nearby waters.
Read below for a brief run down of the major points of the study, and its implications for the Pebble Project.

The Pebble Mine project is a controversial proposal by Northern Dynasty Minerals to build one of the largest gold and copper mines in the world, in southwest Alaska, near Lake Iliamna. Northern Dynasty has not yet applied for permits, but their current proposal involves both a large open pit and an underground mine, as well as removal of the water from the headwaters of Upper Talarik Creek and the Koktuli River ( important fish habitats). The site sits at the headwaters of two major Bristol Bay drainages ( Nushagak and Kvichak), and potentially poses a large threat to the region's salmon. This proposal has become a major political issue in Alaska, pitting pro-mining forces against local native villages and commercial and sport fishermen.

How well does the environemental review process protect water quality at mines?

Since 1969, the federal National Environmental Policy Act (NEPA) has required environmental review of all major mining projects that impact federal land (as well as some on state land). The Environmental Impact Statements (EISs) put out by the mining companies theoretically provide information on potential water quality impacts from mine operation, and how mitigation measures by the mine company will work to protect the environment.
Suprisingly, in 30 plus years, no studies have looked at how actual water quality at mines compares to what is predicted in their environmental statements. This groundbreaking new study from Earthworks (out December 7, 2006), is the first to do just that. You can read the Earthworks summary, or the whole 200 plus page report.

How were the study mines chosen?
First, the authors identified all hardrock mines above a certain size in the U.S. (ending up with 183). Next, they narrowed it to mines which triggered NEPA (137), for which they could get Environmental Impact Statments or Environmental Assessments (ending up with 71). This biases the sample towards newer mines, and those with better environmental documentation. From the set of 71, the authors chose 25 mines for detailed case studies. The main factor controlling which mines were selected, was which ones they could get actual water quality data for (to compare to the predictions). Next, mines were chosen to be representative of the larger sample, in location, climate, type of metal, type of mining operation, etc... One of these mines was an underground mine in Alaska - Greens Creek Mine on Admiralty Island.
Aside from the two historic mines, the average year of opening was 1986, and the average length of time they were or have been operational is 15 years.

What happened to the water?
76% (19/25) of the mines caused pollution in exceedence of water quality standards - in either surface water, ground water, or both.
60% contaminated surface water, and 52% contaminated groundwater.
The most common pollutants involved in these exceedences were toxic heavy metals such as copper, cadmium, lead, mercury, nickel, or zinc (63% of mines), arsenic and sulfate (58% of mines for each), and cyanide (53% of mines.
Of the 19 mines which leached contaminants into surface or ground water, almost half (42%) predicted "low potential" for contaminant leaching, or ignored the possibility (providing no information).
36% (9/25) of the mines have already developed acid drainage on site.
Of these 9, all but one predicted "low potential" for acid drainage, or ignored the problem.

Which mines had problems?
The most important factor that controls whether a mine will contaminate the water is how close it is to water
Of the 11 mines with perennial streams on site, all but one (91%), had contaminant exceedences in surface water.
Of the 9 mines that were close to surface water (either perennial streams on site, or less than one mile away), with moderate or high acid drainage potential, 100% of them contaminated surface water.
Mines near groundwater fared similarly (many mines are close to both surface and groundwater)
Of the 11 mines with shallow depths to groundwater (less than 50 feet or springs on site), with moderate or high acid drainage potential, all but one (91%) have had some impact to groundwater or seeps.
All of these factors (close to surface and ground water, moderate to high acid drainage potential), apply to the Pebble Project.

How did they fail?
Mining companies consistently overestimate the protective effects of their mitigation measures
76% (19) of the mines caused water contamination. Of these,
32% had failures due to hydrologic characterization (such as overestimating dilution).
58% had failures due to geochemical characterization (such as inadequate tests on acid leaching).
84% had failures due to mitigation not working as planned (such as: segregation of acid producing rock not effective, liner leaks, embankment failures, tailings spills, etc...)
Here's a quote from the report: "..even though a high proportion of the mines link a higher acid drainage or contaminant potential and close proximity to water with potential adverse impacts to water quality, the vast majority declare in EISs that mitigation measures will prevent these potential water quality impacts. Predictions of water quality not only do not assume “worst-case” conditions, they consistently assume “best-case” conditions, with all mitigation measures working effectively."

What does this mean for the Pebble Project?
The Pebble Valley is a wet place, with streams (Koktuli River and Upper Talarik Creek), lakes (Frying Pan), and wetlands (throughout the site). It's definitely in close proximity to both surface and ground water.
The ore-bearing rock at Pebble has a significant potential to generate acid, in the absence of mitigation measures (from Northern Dynasty's own statements).
Of the mines in this study with similar characteristics to Pebble, 100% of them contaminated nearby waters.
Northern Dynasty has claimed (see their presentation to Seattle fishermen) that environmental problems happened only at old mines (pre 1980s), or mines not subject to strict environmental review.
But the mines in this study had an average opening date of 1986, and all had extensive environmental reviews under NEPA (most with full EISs). 76% still caused contamination.
Northern Dynasty has claimed that mitigation measures such as separating acid generating waste, and confining waste in tailings lakes, will protect nearby waters.
But the mines in this study consistently overestimated the effectiveness of mitigation. 64% had water quality failures directly attributable to mitigation failures.

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All content by Erin McKittrick, copyright 2006-2007. Contact me with comments or questions at mckittre at gmail dot com.
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Last modified: 2/11/2007