On January 30, 2023, EPA issued a Final Determination under its Clean Water Act Section 404(c) authority to limit the use of certain waters in the Bristol Bay watershed as disposal sites for certain discharges of dredged or fill material associated with development of a mine at the Pebble deposit, a large ore body in southwest Alaska.

After extensive review of scientific and technical research spanning two decades, and robust stakeholder engagement, EPA has determined that certain discharges associated with developing the Pebble deposit will have unacceptable adverse effects on certain salmon fishery areas in the Bristol Bay watershed.

In the 50-year history of the Clean Water Act, EPA has used its Section 404(c) authority judiciously. This action marks the third time in 30 years, and only the fourteenth time in the history of the Clean Water Act, that EPA has used this authority. This action does not apply to any other resource development projects in the State of Alaska.

• Executive Summary: Final Determination, Pebble Deposit Area, Southwest Alaska (pdf)(12.89 MB, January 2023)
• Final Determination, Pebble Deposit Area, Southwest Alaska (pdf) (44.48 MB, January 2023)
• Response to Comments on Final Determination, Pebble Deposit Area, Southwest Alaska (pdf) (6.24 MB, January 2023)
• Federal Register Notice of Final Determination  (February 2023) 

This document is a prepublication version, signed by EPA's Assistant Administrator for Water, Radhika Fox, on 02/03/2023. We have taken steps to ensure the accuracy of this version, but it is not the official version.

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Alaska’s Bristol Bay watershed, home to 25 Alaska Native villages and communities, is an area of unparalleled ecological value, with salmon diversity and productivity unrivaled anywhere in North America. The region provides high-quality, diverse, and connected aquatic habitats, from headwaters to ocean, that support abundant, genetically diverse wild Pacific salmon populations. These salmon populations have supported Alaska Native cultures for thousands of years and continue to support one of the last intact salmon-based cultures in the world.

The Bristol Bay watershed produces approximately half of the world’s Sockeye Salmon, and salmon fisheries are a huge economic driver in the region, supporting approximately 15,000 jobs annually and generating an estimated $2.2 billion in 2019 alone. These salmon populations also help to maintain the productivity of the entire ecosystem, including numerous other fish and wildlife species.

Together, the Bristol Bay watershed’s diverse and largely undisturbed aquatic habitats and productive salmon populations form the foundation of this globally significant ecological and cultural resource.

The Pebble deposit, a large, low-grade deposit containing copper-, gold-, and molybdenum-bearing minerals, is located at the headwaters of the pristine Bristol Bay watershed. The Pebble deposit underlies portions of the South Fork Koktuli River (SFK), North Fork Koktuli River (NFK,), and Upper Talarik Creek (UTC ) watersheds, which drain to two of the largest rivers in the Bristol Bay watershed, the Nushagak and Kvichak Rivers.

Development of a mine at the Pebble deposit has been the subject of study for nearly two decades. EPA’s Final Determination is based on this extensive record of scientific and technical information and applies only to certain discharges of dredged or fill material associated with developing the Pebble deposit.

EPA has determined that the large-scale loss of, and damage to, headwater streams, wetlands, and other aquatic resources that support salmon populations in the SFK, NFK, and UTC watersheds from the discharge of dredged or fill material for the construction and routine operation of the 2020 Mine Plan described in Pebble Limited Partnership’s June 8, 2020, Clean Water Act Section 404 permit application, as well as future proposals that would have the same, similar, or greater levels of aquatic resource loss or damage will have unacceptable adverse effects on anadromous fishery areas in the these watersheds.

Discharges of dredged or fill material to construct and operate the proposed mine site alone would result in the permanent loss of approximately:

• 8.5 miles (13.7 km) of anadromous fish streams.
• 91 miles (147 km) of additional streams that support anadromous fish streams.
• 2,108 acres (8.5 km2) of wetlands and other waters in the SFK and NFK watersheds that support anadromous fish streams.

These discharges would also result in streamflow alterations that would adversely affect approximately 29 miles (46.7 km) of additional anadromous fish streams downstream of the mine site due to greater than 20 percent changes in average monthly streamflow.

The aquatic resources that would be lost or damaged play an important role in supporting salmon populations in the SFK, NFK, and UTC watersheds.

• Prohibits the specification of certain waters of the United States in the SFK and NFK watersheds as disposal sites for the discharge of dredged or fill material for the construction and routine operation of the 2020 Mine Plan. This includes future proposals to construct and operate a mine to develop the Pebble deposit with discharges of dredged or fill material into waters of the United States anywhere at the mine site that would result in the same or greater levels of aquatic resource loss or streamflow changes as the 2020 Mine Plan.
• Restricts the use for specification of certain waters of the United States in the SFK, NFK, and UTC watersheds as disposal sites for the discharge of dredged or fill material associated with future proposals to construct and operate a mine to develop the Pebble deposit with discharges of dredged or fill material into waters of the United States that would result in adverse effects similar or greater in nature and magnitude to the adverse effects of the 2020 Mine Plan.

By prohibiting and restricting the discharge of dredged or fill materials associated with developing the Pebble deposit in certain areas of the Bristol Bay watershed, EPA prevents unacceptable adverse effects on important wild salmon habitat, and in doing so also helps safeguard the critical Bristol Bay ecosystem.

The region’s salmon resources have supported Alaska Native cultures for thousands of years and continue to support one of the last intact salmon-based cultures in the world. Together, the Bristol Bay watershed’s largely undisturbed aquatic habitats and productive salmon populations create this globally significant ecological and cultural resource.

The streams, wetlands, and other aquatic resources of the Bristol Bay watershed also provide the foundation for world-class, economically important, commercial and sport fisheries for salmon and other fishes.