Forty-Seven Thousand Drums Beneath the Farallon Sea: A Hidden Mid‑20th Century Radioactive Waste Legacy
From 1946 to 1970 the U.S. dumped about 47,800 containers of radioactive waste off San Francisco, many missing their designated sites and ending up across roughly 1,400 square kilometers of seabed, including inside the Greater Farallones National Marine Sanctuary. Most were 55-gallon steel drums with concrete weights, carrying low-level waste (thorium, uranium and other fission products); mapping has revealed a mix of intact barrels and degraded remnants at depths from 100 to over 2,000 meters. Early assessments downplayed hazard, but later isotope studies suggested possible marine-life anomalies. The London Convention banned ocean disposal in 1994, and there is no treaty obliging retrieval, so regulators largely leave the drums in place and continue monitoring—the sanctuary floor harboring a legacy from a past approach to waste disposal.