Nuva Joseph is a Ph.D. student in the Soil, Water, and Environmental
Sciences Department of the College of Agriculture and Life Sciences
at the University of Arizona. She is the rare researcher whose efforts
directly benefit the place she calls home and the people who raised
her. Joseph studies inactive uranium mill sites across the country,
specifically targeting those located in Native American communities.
Her studies are part of a uranium mill site remediation project
funded by the Department of Energy (DOE). The DOE manages former
mill sites, four of which are located in tribal communities in the
Four Corners region, where Arizona, Utah, Colorado, and New Mexico
meet. More than five hundred abandoned uranium mines remain within
the Four Corners region.
*Joseph grew up and remains closely tied to her village community,
Moenkopi, on Hopi lands in northeast, AZ. Her personal connection
to the area has made her aware of its history.
"During the Cold War era, in the mid-1900's, acid and mechanical
leaching processes left behind uranium tailings and a legacy of
contaminated regions located in native communities," Joseph explains.
"Uranium tailings were left uncovered and unregulated until the
early 1990s in many locations. Tailings were not defined as a source
of radioactive waste, according to the Atomic Energy Commission.
They didn't fall under a legal definition of a source material.
The Energy Commission insisted that they didn't have jurisdiction
over these tailings."
*Joseph's village of Moenkopi is seven miles downstream from
the Tuba City Arizona Disposal Site. Managed by the DOE's Office
of Legacy Management, the engineered 50-acre disposal cell confines
low-level radioactive tailings accumulated from uranium milling
between 1956 and 1966. Uranium ore extracted at the site was used
exclusively for atomic energy defense activities of the United States.
Active ground water remediation is also part of the strategy to
remove the uranium (the primary site contaminant) and other site-related
contaminants in compliance with the Uranium Mill Tailings Radiation
Control Act of 1978. Within the contaminated region of the aquifer,
37 extraction wells and a network of monitoring wells operate daily.
Surface water seeps, associated with the Tuba City site, are present
along the cliffs that border the Moenkopi Wash, about 4,000 feet
south of the site. The wash continues southeast from there to where
it enters the village of Moenkopi.
*The Navajo and Hopi residents residing near the site use water
from the Moenkopi wash for stock watering and agricultural diversions.
"Every year we irrigate corn plots," Joseph said. "During the planting
season direct precipitation, runoff, and water gained from the subsurface
flows contribute to the Moenkopi Wash (an intermittent stream) that
runs directly through the village. Pumps and man-made canals take
the water from the wash into our corn fields."
*" As Hopi people everything revolves around corn," Joseph
added. "To maintain our responsibilities as Hopi, our cornfields
should never be neglectedour survival and cultural and religious
practices depend on this life way. Hopi people will continue to
rely on the resources the natural world provides us, for many generations."
Of most concern in sites of uranium milling waste, is Radon-222,
produced from the radioactive decay of radium-226. Disposal sites
are required to be operational for the long-termfrom 200 to
1,000 yearsand to limit the flux of radon to below 20 picocuries
per meter squared per second. This limit is designed to prevent
any kind of environmental or human health effects. Heaps of tailings
are confined by a 3-layer cap or cover, two layers of rock riprap
to guard the tailings from water and wind erosion and a clayey soil
layer that creates a barrier to limit the escape of radon gas into
the atmosphere and the seepage of rainwater into the waste below.
*Early caps were not designed for vegetation growth. Today,
disposal cell covers located in semiarid regions are integrating
vegetation into designs. Desert shrubs, like four-wing salt bush
or rubber rabbit brush, help take up rainwater through transpiration,
preventing both water seepage into the tailings and the erosion
of the top layer of riprap rock.
*Joseph's research will help answer questions that the DOE has
on how disposal cell covers located in the semiarid regions of the
Southwest will adapt to short- and long-term climate change while
maintaining long-term performance standards for uranium mill tailings.
"Environmental impacts to the disposal cell cover, such as wind
and water erosion, can mobilize contaminants in the tailings pile,"
says Joseph. "Climate-related changes in temperature and precipitation,
and the magnitude of infrequent storm events will impact vegetation
cover and how vegetation will change over time. The environment
is changing and we need to identify how these projected changes
will impact cell cover performance."
*Some plants have the potential to send roots deep into the
cover system in search of water and to take up contaminants if roots
reach the tailings. Plant roots can also leave fine cracks in the
clayey soil layer potentially allowing radon gas to escape above
regulation limits and water to seep into tailings waste underground.
Joseph's Master of Science thesis work found evidence of plant
uptake of contaminants at some sites with early cover designs.
*"There is an urgent need to figure out these environmental
challenges," Joseph reflects, "because we can't relocate to another
areathese are our ancestral lands. We are permanently fixed
within the reservation boundary areas."
*Joseph plans to extend her research further into understanding
the perception of risk on the part of her Hopi village community,
as regards the tailings waste storage. Many members of Hopi communities
naturally fear the effects of contamination and its possible connection
to higher-than-average cancer rates in the area. She aims to bridge
the communication between community members and DOE, with the goal
of protecting human health, water resources, and the surrounding