Pebble Tailings Storage Facility Designed To Protect Fishery

VANCOUVER - Northern Dynasty Minerals Ltd. and the Pebble Partnership (PLP) highlight several design features that enhance the safety of the tailings storage facility (TSF) for the Proposed Pebble Project to counter negative generalizations repeatedly put forward by project opponents. "The failure of a tailings storage facility around the world is rare. When one does occur, however, failure is often caused by the accumulation of too much water," said Ron Thiessen, President and CEO. "The tailings storage and management plan for Pebble includes an investment of approximately $500 million in modern water treatment facilities to allow the water to be treated and safely released into the environment, meeting all required standards, instead of accumulated. Because of this and other design features, such as constructing the embankments on bedrock and with flatter slopes than is typical in the industry, the Army Corps of Engineers (USACE") in the 2020 Environmental Impact Statement said that they could not conceive of how a failure could occur. The fact is that Alaska has a very rigorous dam permitting process which will ensure that the facility will be safe before it is built."

"We invested a further $150 million in studies of the climate and potential for earthquakes in the area, conducted by a team of industry experts to ensure that the TSF would be safe. Our studies and the research and reports out of the United States Geological Survey ("USGS") demonstrate that Pebble isn't a high seismicity area, as most earthquakes in this region of Alaska are offshore and are almost abated by the time they reach the north shore of Lake Iliamna/Pebble. Still our approach to seismicity (ground movement factor) was to ensure the facilities can withstand the likely earthquake events that might impact SW Alaska, including a repeat of the 1964 Valdez 9.2 M earthquake. This was the largest event ever recorded in North America and the second largest ever. More than 30 alternative tailings sites were evaluated before the final site was selected to minimize the tailings footprint on wetlands. In fact, our project as proposed would impact less than one mile of stream for every 1,000 miles of streams feeding into Bristol Bay. The reality is that there just aren't many salmon near to the proposed mine site. We know this because of extensive salmon population studies we have conducted over many years. Why are these populations so small? It may be because of the poor quality habitat, lack of surface water in the streams, or the hills that exist between the Pebble site and the ocean, which is 120 miles away, making it a challenge for the salmon to get that far inland, or there may be other reasons. The lack of fish living near the proposed mine site does not, however, diminish our commitment to designing and operating a safe mine that can coexist with the Bristol Bay fishery.”