Chapter 1

Introduction

At over 50 sites, mostly in the southwestern United States, widespread
contamination of both land and groundwater resulted from uranium ore
processing operations that took place from the early 1940s throughout the
1960s. During that period, most of the nation's uranium mining and milling
(ore processing) activities were conducted by private companies for the
Atomic Energy Commission (the Department of Energy's predecessor).
Uranium ore was crushed and processed for use in developing weapons
and in the emerging nuclear energy industry. But for every ounce of
uranium that was extracted from ore, 99 ounces of waste were produced
in the form of mill tailings-a finely ground, sand-like material. By the time
the government's need for uranium peaked, tons of mill tailings had been
produced at the processing sites. After fulfilling their government
contracts, many companies closed down their uranium mills and left large
piles of tailings at the mill sites.

The abandoned piles of uranium mill tailings contain radioactive wastes
and other hazardous materials that had been used in the uranium
extraction process. Despite the potential health risks, some mill operators
left the piles of tailings uncovered and exposed to the elements. As a
result, the tailings were spread by wind, water, and human
intervention-thus contaminating properties beyond the mill. In some
communities, citizens used the tailings as building materials for homes,
schools, office buildings, and roads because the health risks were not
commonly known. Disposal of the tailings and the contaminated liquids
from uranium processing resulted in contamination of the groundwater. In
addition, because the piles of tailings were exposed to weather, in some
cases the leaching effects of rain and snowmelt also contaminated the
groundwater. Figure 1.1 shows how groundwater becomes contaminated.

By the late 1960s, radiological research had determined that the
abandoned mill sites posed a potential hazard to public health. Exposure
to radioactive substances may cause cancer and other diseases, as well as
genetic damage. The most hazardous constituent of uranium mill tailings is
radium, which is radioactive. Radium produces radon, a radioactive gas
whose decay products can cause lung cancer. In effect, the amount of
radon released from a pile of tailings remains constant for about 80,000
years. Tailings also emit gamma radiation, which can increase the

Chapter 1
Introduction

Uranium Mill Tailings
Radiation Control Act
of 1978 Required
Cleanup of Tailings

incidence of cancer and genetic risks. Other potentially hazardous substances in tailings include arsenic, molybdenum, and selenium. The concentrations of these materials found in the tailings vary by site, ranging from 2 to more than 100 times the amounts naturally existing in soil. Concerns about the potential long-term adverse health effects of exposure to uranium mill tailings led to engineering and radiological studies that identified many abandoned uranium mill sites and nearby properties in need of cleanup.

In November 1978, to provide a comprehensive regulatory scheme for the safe disposal of uranium mill tailings, the Congress passed the Uranium Mill Tailings Radiation Control Act of 1978 (P. L. 95-604). Title I of the act governed the cleanup of mill sites that were already inactive when the legislation was passed, referred to in this report as Title I sites; Title II governed the control and cleanup of milling operations that were still active at that time, referred to in this report as Title II sites. The act made DOE primarily responsible for the cleanup of the Title I sites and the operators/owners of the Title II sites responsible for cleaning up their own

sites.

The act assigned responsibilities to three agencies: the Environmental Protection Agency (EPA), the Department of Energy (DOE), and the Nuclear Regulatory Commission (NRC). EPA was directed to establish standards for the cleanup and disposal of contaminated material from both inactive and active uranium processing sites. Under the act, as amended, EPA was to consider factors such as the risk to public health, safety, and the environment, and the environmental and economic costs of applying its standards. In January 1983, EPA issued standards for remedial actions at the Title I sites. Later that same year, EPA issued standards governing the Title II sites. These standards, except those concerning groundwater, were essentially identical to those adopted for the Title I sites.' In part, these standards limit the release of radon gas into the environment and require that the disposal method be designed to control radiological hazards "for up to one thousand years, to the extent reasonably achievable, and in any case, for at least two hundred years."

Under the act, DOE was required to clean up all the Title I sites to EPA's standards. The act created a plan of federal and state cooperation in which

'Both sets of standards were challenged by several parties in the U.S. Circuit Court of Appeals for the Tenth Circuit. The Court upheld all aspects of the standards except the groundwater standards for th Title I sites. In 1987, EPA proposed new groundwater standards for these sites. Final groundwater standards were not issued until January 1995.