&EPA
Abandoned Uranium Mines
Navajo Nation
U.S. Environmental Protection
Agency • Region 9 • San Francisco, CA • November 2019
USEPA Airplane Survey in the
Eastern Abandoned Uranium (AUM) A/line Region
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Soil samples.
In the summer of 2018, the U.S. Environmental Protection Agency (USEPA) flew the Airborne Spectral Photometric
Environmental Collection Technology (ASPECT) airplane over abandoned uranium mines in Eastern and Western Navajo
Nation. This low-flying, radiation-detecting plane collects data that shows radiation levels on the ground. The data will help
USEPA's efforts to characterize the level and extent of radiation at and around abandoned uranium mines (AUM). This fact
sheet presents results and example figures from the ASPECT survey in the Eastern AUM Region which included Smith Lake,
Coyote Canyon, Church Rock, Standing Rock, Mariano Lake, Baca/Prewitt, Pinedale, Nahodishgish, and Casamero Lake
Chapters.
Why Use ASPECT?
The ASPECT airplane is a cost-effective way
to collect radiation data for large areas using
state-of-the-art sensors to measure radiation
levels on the ground.
The data collected by the ASPECT airplane is
useful to understand the general location and
size of areas that may have radiation at levels
of concern.
Data helps USEPA determine if mining-
impacted areas were missed during the
ground investigation phase of the Eastern
Agency mines.
Understanding ASPECT Airplane Findings
The ASPECT plane flies at around 300 feet above the ground, which
gives it a field of view of approximately 6.5 acres. The data collected
provides a general trend of areas containing elevated uranium or
thorium levels. The exact area of contamination is further defined
by ground surveys.
Where did the ASPECT Plane Survey?
•	The ASPECT airplane completed four flights in the Eastern
AUM Region that covered more than 30 square miles of land.
•	The surveys included 16 abandoned uranium mine sites
and one mill site that have been previously investigated and
results have been publicly published. (For more information
on the Eastern Agency sites please visit:
https://www.epa.gov/navajo-nation-uranium-cleanup/
eastern-abandoned-uranium-mine-region)
• Approximately 13,000 data points were collected.

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Probability of U Present
>70%
>90%
<1.00
ell concentration (pCi/g)
Example Results
1.00-2.00
2.00-3.00
3.00-4.00
4.00-5.00
5.00-6.00
6.00-7.00
Haystack Mine. Probability of Uranium Present (PUP)
product shows areas where natural uranium is out of
balance (white) with the natural background (black).
White areas indicate where uranium spectral signatures are
statistically significantly present for uranium and its decay
products. This product is not correlated to concentration
and should only be used to identify areas where further
ground-based characterization efforts may be warranted.
Equivalent Uranium concentration (pCi/g) contour of the Black
Jack 1 mine. This product was derived from 453 data points
covering 1.2 square miles. The dot represents the mine
location. Much of the red area generally exceeds 7.0 pCi/g
surrounded by background concentrations ranging between
< 1 pCi/g to 2 pCi/g. This image should not be used to
independently assess potential health risks. Additional
information is necessary to make appropriate health-related
nr rlp.nnup ijp.r.icinnc	
eU concentration (pCi/g)
1.00-2.00
2.00-3.00
3.00-4.00
4.00-5.00
5.00 - 6.00
*
This map shows results from the 2018 ASPECT survey of radiation levels
over an area of about 7.8 square miles in Smith Lake and Mariano Lake
Chapters including four mines (Mariano Lake, Mac 1 &2, Black Jack 2 and
Ruby 1 mines). The blue and green colors represent the lower levels of gamma
radiation and the yellow, orange and red colors represent the higher levels of
gamma radiation.
Results, Next Steps and More Information
The survey results did not show contamination outside the mining areas that have previously been identified through
site investigations.
USEPA will continue to work with the community and the Navajo Nation to complete any additional ground
assessments necessary at the mines flown in the Eastern Agency and work towards selecting a final cleanup plan for each
of the sites.
For A/lore Information:
Sara Jacobs
Remedial Project Manager
USEPA Region 9
(415) 972-3564
jacobs.sara@epa.gov
Priscilla Tom
Community Involvement Coordinator
USEPA Region 9
(505) 240-0093
tom.priscilla@epa.gov
Dariel Yazzie
Environmental Program Supervisor
NNEPA Superfund
(928) 871-7601
darielyazzie@navajo-nsn.gov
ASPECT information website: www.epa.gov/emergency-response/aspect
USEPA Navajo Abandoned Uranium Mine Region website: www.epa.gov/navajo-nation-uranium-cleanup

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