Groundwater Events Sorted by Date

This report lists specific instances of radioactively contaminated water leaks, spills, and overflows at numerous US nuclear facilities. The events range from small spills of a few gallons to large-scale leaks of hundreds of thousands of gallons, often involving tritium. Common causes include equipment failure, operator error, and pipe degradation, with contamination affecting soil, storm drains, and nearby water bodies such as the Mississippi River, Lake Michigan, and the Connecticut River.

• Numerous events involved the release of radioactively contaminated water into major US water bodies. For example, in 1971, 53,000 gallons spilled into the Mississippi River from Monticello, and in 1976, 83,000 gallons flowed into the Connecticut River from Vermont Yankee.
• Tritium is a frequently detected contaminant in groundwater and monitoring wells, often exceeding the EPA limit of 20,000 picocuries per liter. At McGuire Unit 2 in 2006, samples measured up to 35,200 picocuries per liter.
• Operator errors, such as mispositioned valves or failure to close valves, have led to significant spills. At Browns Ferry Unit 1 in 1973, 1,400 gallons of liquid radwaste were discharged to the river due to personnel error.
• Equipment failure, including ruptured pipes and leaking valves, is a recurring cause of contamination. In 1971 at Dresden Unit 2, a ruptured aluminum test return line caused approximately 15,000 gallons of contaminated water to leak into the ground.
• Some facilities have experienced systemic issues with condensate storage tanks. At Dresden Units 2 and 3 in 2009, monitoring wells near the condensate storage tank detected tritium concentrations of 3.2 million picocuries per liter.
• Contamination has occasionally reached public infrastructure. In 1971, approximately 10,000 gallons of contaminated water from Monticello entered the Minneapolis drinking water system.
• Remediation efforts often involve the excavation of contaminated soil and shipment to licensed waste facilities. At San Onofre Unit 1, 21,900 cubic feet of contaminated sand were excavated and shipped to Richland, WA.
• The document records instances of uncontrolled releases due to a lack of proper procedures. At Rancho Seco in 1986, the company discharged about 350,000 gallons of contaminated water to the environment using a temporary procedure that was not approved.

APA

Union of Concerned Scientists (2010). Groundwater Events Sorted by Date. https://www.ucs.org/sites/default/files/2019-10/Groundwater-Events-Sorted-by-Date.pdf

Chicago

Union of Concerned Scientists. Groundwater Events Sorted by Date. 2010. https://www.ucs.org/sites/default/files/2019-10/Groundwater-Events-Sorted-by-Date.pdf.

Wikipedia

{{cite report |author=Union of Concerned Scientists |title=Groundwater Events Sorted by Date |date=27 September 2010 |url=https://www.ucs.org/sites/default/files/2019-10/Groundwater-Events-Sorted-by-Date.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{unionofconcernedscientists2010groundwater, author = {{Union of Concerned Scientists}}, title = {{Groundwater Events Sorted by Date}}, institution = {Union of Concerned Scientists}, year = {2010}, month = sep, url = {https://www.ucs.org/sites/default/files/2019-10/Groundwater-Events-Sorted-by-Date.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }