Pebble Mine Pit: Cross Section

Post-mining pit lake with the potential to contaminate ground and surface waters.

Pebble Mine Pit Cross Section
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Pebble Mine Pit Diagram
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Although operations are likely to also include underground mining (block caving), the Preliminary Assessment presents design scenarios for an open pit under three “development cases”, which include 25, 45, and 78-year time horizons.

Upon completion of mining operations, groundwater which will be pumped from the open pit and underground workings during mining operations, will be allowed to fill these areas, forming a post-mining pit lake.

If the hydrology of the site is such that water from the pit can migrate down gradient to ground and surface waters, there could be long-term impacts to water off of the mine site. Because the Pebble Mine sits atop a watershed divide in a region with extensive hydrologic connection, management of contaminated pit water should be a key consideration in review of the Pebble Mine proposal.

Taken from “Bristol Bay’s Wild Salmon Ecosystems and the Pebble Mine.” For a more detailed explanation of this graphic, please see the full report.

For a higher resolution version of this diagram, please email

Images and text © Wild Salmon Center

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