Sea Level Rise Threatens Humboldt Bay’s Nuclear Legacy

King Salmon and PG&E’s HBGS, HBPP, and ISFSI with 3.3 feet (1.0 meter) of sea level rise at king tide. Image: Aldaron Laird, 2019.
King Salmon and PG&E’s HBGS, HBPP, and ISFSI with 3.3 feet (1.0 meter) of sea level rise
at king tide. Image: Aldaron Laird, 2019.

Is Humboldt Bay vulnerable to sea level rise? Yes. Unfortunately, in addition to buildings and roadways, we must also consider the risks to spent nuclear fuel.

The King Salmon area is one of the communities most at-risk to sea level rise on the North Coast. It is also home to two of the most critical facilities on Humboldt Bay—the Independent Spent Fuel (nuclear) Storage Installation (ISFSI) and PG&E’s Humboldt Bay Power Generating Station—both of which are vulnerable and at risk from sea level rise.

Humboldt Bay is experiencing the highest rate of sea level rise (1.5 feet over the last hundred years) on the west coast of the United States. Ground zero for exposure to sea level rise on Humboldt Bay is the shoreline directly across from the entrance of the bay. The two jetties (constructed around 1890) and the dredging of the entrance channel funnel high-energy waves directly at this shoreline. In the winter, the highest annual tides (known as king tides) and large storm waves wash over the rocked shoreline in front of the railroad, PG&E’s Humboldt Bay Power Station, the bluff in front of the ISFSI, and King Salmon.

The nuclear unit at PG&E’s Humboldt Bay Power Plant in King Salmon was built in the early 1960s and is nearing the final stages of the decommissioning process. The spent nuclear fuel is stored in six dry casks encased in concrete at Buhne Hill, just 115 feet back from the bluff facing the entrance to the bay.

The shoreline at the base of Buhne Hill has experienced the greatest amount of erosion and retreat on Humboldt Bay, approximately 1,480 feet (at a rate of 24 feet/year) from the 1890s when the jetties were constructed, to the 1950s when PG&E installed rock slope protection.

By the 1970s, the shoreline in front of King Salmon had eroded away, allowing waves to crash onto Buhne Drive. In the 1980s, the U.S. Army Corps of Engineers constructed rock walls and jetties and a barrier dune system to protect King Salmon.

After the 2005 New Year’s Eve storm, the Governor declared a State of Disaster on Humboldt Bay, due to the most extreme water levels ever recorded on the Bay—9.6 feet at the North Spit tide gauge (the mean annual maximum for that gauge is 8.8 feet). PG&E had to do emergency repairs to its rock slope protection at the base of the bluff in front of the nuclear fuel storage casks. Emergency repairs had to be done again in 2018.

Recently released sea level rise projections indicate that water elevations could increase significantly in the next 40 years: 1 foot by 2030, 2 feet by 2050, and 3 feet by 2060 (OPC 2018). By 2060, with three feet of sea level rise, PG&E’s new Humboldt Bay Generating Station and decommissioned Humboldt Bay Power Plant and King Salmon could become completely inundated, and Buhne Hill, where the ISFSI is located, could become an island.

By 2090, the existing rock slope protection in front of the bluff on Buhne Hill and the nuclear fuel storage casks could be overtopped by 6 feet of sea level rise. Chances are high that the casks will still be there onsite. The Coastal Commission, when issuing PG&E a permit for the ISFSI stated, “there are no foreseeable alternative sites available for the spent [nuclear] fuel…the project would likely be at the site in perpetuity.” Nearly 15 years later, the case remains the same.