RELEASES: Columbia River
FROM WORLD WAR II UNTIL THE EARLY 1970s, the Columbia River downstream from Hanford "held the distinction of being the most radioactive river in the United States."  The cold and abundant waters of the Columbia River made the Hanford site an ideal location. Approximately 1,200 miles long, the Columbia is the largest North American river flowing into the Pacific Ocean. With its magnificent native salmon runs and seemingly endless flow of pure water, the big river represents the lifeblood of the Pacific Northwest for many of the region's inhabitants, especially Native Americans.
To facilitate plutonium production, an endless supply of cold water was required to cool the extreme temperatures produced during reactor operations. During the cooling process, radiation entered the Columbia River in three ways: heat transfer, chemical treatments, and radioactive material introduced into wastewater effluent.
Columbia River water passed through eight "single-pass" reactors operating along its banks at the Hanford site by 1955. Pumps injected water into the reactor's core at a rate of almost 30,000 gallons per minute.  Although the water did not come into direct contact with the fuel rods, the extreme heat of the process transferred high amounts of radioactive isotopes from the reactor core into the coolant water. After leaving the cores, the discharged cooling water was then released into 107 retention basins allowing short-lived radiation to decay or stabilize. The effluent was also allowed to cool down from the nearly 200-degree temperature it had reached within the reactors with retention time ranging from a minimum of twenty minutes to six hours. Afterwards the warm, spent water was discharged back into the river to complete the loop. Even with retention, significant quantities of radionuclides with half-lives longer than a few hours were released into the river. 
To keep the cooling system clean, extreme chemical treatments were added to pipes. These chemicals as well as other natural occurring minerals already present in the affluent became radioactive during the cleaning process. As much as 25 to 40 percent of the phosphorus-32 released into the river came from chemicals used in water treatment.  Additionally, fuel slug ruptures, particulate matter, and debris activated through reactor purging added to this toxic stew. Many of the cleansing chemicals were on their own were lethal to animal and plant life when introduced in aquatic environments. All in all, for every kilogram of plutonium manufactured, some 55,000 gallons of radioactive liquids were created.  Over sixty radioisotopes were released into the Columbia through reactor effluent. Of these, phosphorus (P-32), arsenic (As-76), zinc (Zn-65), chromium (Cr-51), and neptunium (Nr-239) are considered the most dangerous. As beta-emitters these radionuclides are known to affect the gastrointestinal tract, bones, and reproductive and blood-forming organs of living organisms including humans. 
Radioactive contamination introduced into the Columbia River affected a variety of aquatic animals and plant life. Algae, insects, fish, waterfowl, and other riparian organisms dependent on the river began to accumulate radioactive waste as the contaminated substances entered the food chain, concentrating radiation into tissue and organs thousand of times before they reached those higher on the food chain. Algae was found to concentrate radiation up to 100,000 times the levels of contamination of the river water.  From 1957 to 1964, evidence of contamination appeared as far as the Pacific Coast when radioactive isotopes were found in Washington's Willapa and Oregon's Tillamook Bay oyster beds. 
Humans were exposed internally to Hanford radiation via the river pathway by drinking contaminated water (from 1944 - 1972 the cities of Kennewick and Pasco used the river for sanitary water supplies) or from eating contaminated food such as fish, shellfish, or waterfowl taken directly from the river or from fresh produce irrigated with contaminated water. Reports suggest that the area's Native American population was at the highest risk from this type of contamination due to their traditional diet consisting of up to one and a half pounds of locally caught salmon consumed daily. 
External radiation exposure also occurred through recreational activities along the contaminated stretches of river shoreline or through boating or swimming downstream from reactors. People interviewed recalled that in the 1950s and 1960s they preferred swimming near Hanford because the water was warmer. 
Hanford officials were well aware of the dangers their operation posed to the general public and overall environmental health of the region. Still, they continued to contaminate the river with radioactivity while publicly claiming that production activities did not pose a health threat to the surrounding civilian communities or the environment.