In the April 29, 2015 blog post captioned Legal Update 3 -- Pebble Mine, I referred to the EPA's July 2014 proposals regarding the regulation of mining in the Bristol Bay watershed.  As discussed in the blog, final action has yet been taken on these proposals.

The EPA's Proposed Determination and the Executive Summary provide a lot of detail about the Pebble mining proposal and the threat that it would pose to the salmon fishery. 

Click here for the EPA's Executive Summary and click here for the full text of the Proposed Determination.

All of the text below is quoted (with citations omitted) from the EPA's Executive Summary.

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"Alaska’s Bristol Bay watershed is an area of unparalleled ecological value, boasting salmon diversity and productivity unrivaled anywhere in North America. As a result, the region is a globally significant resource with outstanding value. The Bristol Bay watershed provides intact, connected habitats—from headwaters to ocean—that support abundant, genetically diverse wild Pacific salmon populations. These salmon populations, in turn, maintain the productivity of the entire ecosystem, including numerous other fish and wildlife species.

"The Bristol Bay watershed’s streams, wetlands, and other aquatic resources support world class, economically important commercial and sport fisheries for salmon and other fishes, as well as a more than 4,000-year-old subsistence-based way of life for Alaska Natives. Each year Bristol Bay supports the world’s largest runs of sockeye salmon, producing approximately half of the world’s sockeye salmon.

"These sockeye salmon represent the most abundant and diverse populations of this species remaining in the United States. Bristol Bay’s Chinook salmon runs are frequently at or near the world’s largest, and the region also supports significant coho, chum, and pink salmon populations. Because no hatchery fish are raised or released in the watershed, Bristol Bay’s salmon populations are entirely wild. Bristol Bay is remarkable as one of the last places on Earth with such bountiful and sustainable harvests of wild salmon. One of the main factors leading to the success of this fishery is the fact that its aquatic habitats are untouched and pristine, unlike the waters that support many other fisheries."

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"The Pebble deposit is a large, low-grade, porphyry copper deposit (containing copper-, gold-, and molybdenum-bearing minerals) that underlies portions of the South Fork Koktuli River, North Fork Koktuli River, and Upper Talarik Creek watersheds. Based on information provided by NDM [referring to Northern Dynasty, the parent company that ultimately owns Pebble] to the SEC, mining the Pebble deposit is likely to involve excavation of the largest open pit ever constructed in North America, covering up to 6.9 square miles and reaching a depth of as much as 0.77 mile; for reference, the maximum depth of the Grand Canyon is approximately 1 mile.

"Disposal of resulting waste material would require construction of up to three mine tailings impoundments covering an additional 18.8 square miles and waste rock piles covering up to 8.7 square miles in an area that contains highly productive streams and wetlands. The volume of mine tailings and waste rock produced from the smallest mine proposed by NDM to the SEC would be enough to fill a professional football stadium more than 880 times, whereas the largest mine would do so more than 3,900 times.

"In total, these three mine components (mine pit, tailings impoundments, and waste rock piles) would cover an area larger than Manhattan. Mine construction and operation would also require the construction of support facilities, including a major transportation corridor, pipelines, a power generating station, wastewater treatment plants, housing and support services for workers, administrative offices, and other infrastructure. Such facilities would greatly expand the 'footprint' of the mine and affect additional aquatic resources beyond the scope of this proposed determination. Although NDM’s preliminary plans could change, any mining of this deposit would, by necessity, require similar mine components, support facilities, and operational features."

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“After evaluating available information, EPA Region 10 has reason to believe that unacceptable adverse effects on fishery areas (including spawning and breeding areas) could result from the discharge of dredge or fill material associated with mining the Pebble deposit.”