More than 40 years of plutonium production for America's nuclear weapons program extensively contaminated the Hanford site in southeastern Washington. Following the end of plutonium production in 1989, Oregon joined with federal, state and local governments, Native American Tribes, and citizen groups, to advocate for and compel the Hanford cleanup. Hanford site workers are now engaged in the world's largest environmental cleanup project. The cleanup encompasses more than 1,900 waste sites, ranging from small areas of surface contamination to 177 aging underground storage tanks containing about 53 million gallons of highly radioactive and chemically hazardous waste. There is urgency to the cleanup, as contaminants continue to spread and waste storage facilities age. The cleanup is necessary to prevent further contamination of the Columbia River. The cleanup is also necessary to restore precious and valuable resources such as the groundwater; comply with environmental laws and restore the damaged environment; preserve treaty rights; and eliminate or reduce risks to all people who live, work, or visit the area.