Church Rock Spill

Nathaniel Morris
March 9, 2017

Submitted as coursework for PH241, Stanford University, Winter 2017

Uranium Mill Dam Disaster

Fig. 1: The Church Rock spill clean up efforts (Source: Wikimedia Commons).

The Church Rock spill occurred in 1979 and is to this day the largest accidental release of radioactive material in the United States. [1] This incident was a result of the breach and then failure of one of United Nuclear Corporation's disposal ponds for mine tailings from their uranium mill. The dam was constructed on an unstable geological site as later acknowledged by records kept by the United Nuclear Corporation themselves. Additionally federal and state inspections and reports noted that the site was unstable. [2] When breached the dam released 1,100 tons of tailings along with 94 million gallons of mill process effluent which cumulatively released three times as much radiation the the Three Mile Island incident. [3] The effects of the radioactive mill tailings were far reaching with radiation from thorium- 230 and uranium spreading 80 plus kilometers down the Puerco River in New Mexico. [1]

Environmental and Health Affects of the Incident

Because of the large area the radiation spill contacted, the environmental and health affects have been wide reaching. Elevated radiation has been monitored as far as 50 miles away from the initial spill and the radiation in the Puerco River showed 7,000 times the standard amount for drinking water. [4] This radiation contaminated not only the water but the food chain as well as seen through cattle in the area showing higher levels of radiation. Because roughly half of the Navajo population in the area get their water from unregulated sources, which became contaminated, they suffered from exposure to high levels of poisonous uranium mill tailings in the water supply. This resulted in elevated rates of kidney disease as well as at the affected Navajo population being 1.83 times more likely to have 1 of 33 selected defects. [2,3]


The United Nuclear Corporation along with the government of New Mexico did embark in a cleanup effort as shown in Fig. 1. However this attempt to fix their mistake is criticized as being vastly inadequate for the severity of damages caused by the Church Rock Spill. Scholars argue that their response was an insufficient response to the drastic situation considering the impoverished Navajo people were not able to advocate for themselves. Additionally many of the Navajo people were not able to speak English and authorities did not communicate properly in order warn the residents in the area to protect themselves from the radiation and poisonous water. Half of recoverable uranium is in New Mexico and half of that is located on Navajo land. Because of this the Navajo people have been subjected, since 1940 when uranium mining began in New Mexico, to the negative health affects of the radioactive metal. One in six Navajo uranium miners have been afflicted with lung cancer. While the Church Rock spill was the largest destructive incident other instances of uranium poisoning in Navajo lands have been a continuous problem and this one spill was not an isolated incident. [4]

© Nathaniel Morris. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] W. L. Graf, "Fluvial Dynamics of Thorium-230 in the Church Rock Event, Puerco River, New Mexico," Ann. Assoc. Am. Geogr. 80, 327 (1990).

[2] J. I. Ross, American Indians at Risk (2 volumes) (Greenwood, 2013), p. 439.

[3] C. Arnold, "Once Upon a Mine: The Legacy of Uranium on the Navajo Nation," Environ. Health Persp. 122, A44 (2014).

[4] B. E. Johansen, Resource Exploitation in Native North America: a Plague Upon the Peoples (Praeger, 2016), pp. 7-15.