United States
Environmental Protection
Agency
Office of Radiation Programs
Las Vegas Facility
P.O. Box 18416
Las Vegas NV89114
ORP/LV 80-2
February 1980
Radiation
&EPA
Above Ground Gamma Ray
Logging of Edgemont,
South Dakota and Vicinity
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Technical Note
ORP-LV-80-2
ABOVE GROUND GAMMA RAY LOGGING
OF EDGEMONT, SOUTH DAKOTA AND VICINITY
Jack E. Thrall*
Joseph M. Hans, Jr.*
Vonnl Kallemeyn**
February 1980
*U.S. Environmental Protection Agency
Office of Radiation Programs
Las Vegas Facility
Las Vegas, Nevada 89114
**South Dakota Department of Water and Natural Resources
Foss Building, Pierre, South Dakota 57501
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DISCLAIMER
This report has been reviewed by the Office of Radiation Programs-
Las Vegas Facility, U.S. Environmental Protection Agency, and approved for
publication. The mention of trade names of commercial products does not con-
stitute endorsement or recommendation for their use.
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PREFACE
The Office of Radiation Programs of the U.S. Environmental Protection
Agency carries out a national program designed to evaluate population exposure
to ionizing and non-ionizing radiation, and to promote development of controls
necessary to protect the public health and safety. This report presents
results from mobile gamma ray logging of several communities in the state of
South Dakota to locate areas or structures containing uranium mill tailings.
Readers of this report are encouraged to inform the Office of Radiation
Programs of any omissions or errors. Comments or requests for further
information are also invited.
Donald W. Hendricks
Director, Office of
Radiation Programs, LVF
ii
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ABSTRACT
At the request of the U.S. Nuclear Regulatory Commission, the town of
Edgemont, South Dakota and vicinity was surveyed in 1978 to determine if
uranium mill tailings from the former Edgemont Uranium Mill had been used for
off-site construction or other purposes since a similar survey conducted in
1972. Sixteen additional possible tailings use locations were found during
the 1978 survey.
This report summarizes the results of the 1971-72 and 1978 surveys to
locate suspected tailings use areas. It also presents and discusses other
gamma radiation measurements made in and around Edgemont.
iii
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TABLE OF CONTENTS
Page
ABSTRACT H1
LIST OF FIGURES v
LIST OF TABLES v
ACKNOWLEDGMENT vi
INTRODUCTION 1
SUMMARY AND CONCLUSIONS 4
EQUIPMENT DESCRIPTION 6
Mobile Radiation Scanner 6
Portable Scintillometers 6
Ion Chamber 7
DISCUSSION OF THE 1971-72 SURVEY 8
DISCUSSION OF THE 1978 SURVEY 16
DISCUSSION OF ADDITIONAL GAMMA RADIATION MEASUREMENTS MADE IN 21
EDGEMONT AND VICINITY DURING THE 1978 SURVEY
DISCUSSION OF GAMMA RADIATION MEASUREMENTS MADE IN COTTONWOOD DURING 32
THE 1978 SURVEY
REFERENCES 37
APPENDIX A - Sketches of Locations and Gamma Radiation Measurements 38
Made During the 1978 Survey
APPENDIX B - Sketch of Edgemont Showing the Approximate Locations of- 47
Anomalies Found During the 1971-72 and 1978 Surveys and
Gamma Radiation Measurements
APPENDIX C - Sketch of Dudley Showing the Approximate Location of 49
Anomalies Found During the 1971-72 and 1978 Surveys and
Gamma Radiation Measurements
iv
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LIST OF FIGURES
Number
Page
1 Aerial photograph of Edgemont, SD and vicinity 3
2 Indoor radon study-gamma screening form 13
3 Log-probability plot of PIC measurements 26
4 Log-probability plot of (LOG) scintillometer measurements 31
5 Gross corrected PIC measurements in Cottonwood 34
6 Delta (A) measurements in Cottonwood 35
LIST OF TABLES
Number page
1 Follow-up surveys of the anomalies identified during the 1971-72 9
survey
2 Follow-up surveys of the anomalies identified during the 1978 survey 18
3 PIC measurements in Edgemont, Dudley, Cottonwood 22
4 Low outside gamma (LOG) scintillometer measurements at locations where 29
tailings were not used - 1978 survey
5 Scintillometer measurements in Cottonwood 33
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ACKNOWLEDGMENT
The authors wish to thank Ping Chee, Argonne National Laboratory (ANL);
Michael Casada, Tennessee Valley Authority (TVA); John Geidt, U.S. Environ-
mental Protection Agency (EPA); Jeffrey Kotsch, U.S. Nuclear Regulatory
Commission (NRC); and Robert Sedlacek, Silver Kings Mines Inc.; for their
efforts during the 1978 survey. Their willingness to work long hours aided in
the completion of the survey before the big snow.
To Dave Duncan, Lucius Pitkin Inc., and all the unknown heros of the
1971-72 survey, our thanks for a job well done.
VI
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INTRODUCTION
Uranium ore contains, in addition to uranium, radioactive members of the
uranium decay chain. Most of the uranium is removed from the ore during the
milling process, and the majority of the other radioactive nuclides are dis-
charged in the primary milling wastes. These wastes (tailings) consist of
sands and slimes which have been used in many communities in the past for con-
struction and other purposes. Gamma radiation, emitted from the wastes, can be
a source of human whole-body exposure. Internal exposure may result from the
inhalation or ingestion of the wastes or inhalation of the short-lived
radioactive progeny of radon-222.
Although the wastes may have relatively low concentrations of radioactive
materials, their use for construction purposes generally brings them close to
humans for prolonged periods of time. This can cause radiation exposures in
excess of normal background exposures for the general population and increase
the risks of radiation induced health effects. In some cases, corrective
action may be necessary to reduce radiation exposures at locations where mill
tailings have been used. The evaluation of the radiological impact and of the
possible need for the corrective actions is to locate those structures or
areas where tailings have been used.
The Edgemont Uranium Mill (HUM) was constructed in 1956 and was operated
by Mines Development, Inc., a subsidiary of Susquehanna Western, Inc. The
initial capacity of the EUM was 250 tons of ore per day, this capacity was
expanded within a year to 500 tons per day.
The original process for uranium extraction from the ore involved acid
leaching, resin-in-pulp (RIP) ion exchange, and neutralization of the pregnant
solution with magnesium oxide for precipitation. Facilities for separating
and recovering molybdenum byproducts were added to the circuit as sufficient
amounts of molybdenum became present in the lignite ash that also was proces-
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sed for uranium. In 1960, a vanadium circuit was added and additional vana-
dium was recovered from reclaimed RIP slime tailings by acid leachi'ng and
solvent extraction.
Uranium recovery initially averaged 95 percent but towards the end of
operations the recovery averaged 90 percent. Vanadium recovery from the ore
averaged 75 to 80 percent. The 1(303 content of the ore averaged 0.20
percent with a relatively low vanadium content of about 0.25 percent V20&*
The bulk of the uranium output was produced under contract with the former
U.S. Atomic Energy Commission.
At one time nearly 10 percent of the ore fed to the HUM was uraniferous
ash derived from the burning of lignite coal near Belfield, North Dakota. The
lignite ash contained an average of 0.35 percent UaOs and 0.25 to 0.35
percent molybdenum. Most of the ore processed at the EUM was mined in the
Black Hills area of South Dakota, Wyoming, and Washington State (FBDU, 1978).
At the request of the U.S. Nuclear Regulatory Commission (NRC), the U.S.
Environmental Protection Agency, Office of Radiation Programs-Las Vegas
Facility (ORP-LVF) conducted a radiation survey of Edgemont, South Dakota and
vicinity, during November 6-8, 1978. Figure 1 is an aerial photograph of
Edgemont, SO and vicinity. The primary purpose of the survey was to determine
if any off-site uranium mill tailings use had occurred at locations other than
those previously identified during a similar survey conducted during 1971 and
1972. To perform these surveys, a mobile gamma scanning van containing a
sensitive gamma ray detector was used to locate anomalous gamma radiation
levels. The anomalies were then further investigated to determine their
cause.
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Figure 1. Aerial Photograph of Edgemont, SD & Vicinity
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SUMMARY AND CONCLUSIONS
A total of 145 gamma radiation anomalies were identified by mobile logging
in the Edgemont, South Dakota vicinity during the 1971-72 and 1978 surveys.
Forty-four of the anomalies identified during the 1971-72 logging survey were
determined to be possible tailings use locations. Sixteen additional
locations were identified as having possible tailings use during the 1978
logging survey. It appears that some additional uranium mill tailings may
have been used since the 1971-72 survey. It is possibe that some of the
tailings locations found in the 1978 survey were missed during the 1971-72
survey because they were shielded by objects or earth.
All suspected tailings use locations found during the 1978 survey were
listed as "possible tailings use" and are considered as having tailings unless
they are shown to be otherwise by sample analysis and further measurements.
The reason for this is that it appears that mine wastes have been used in the
Edgemont school area and could have been used at other locations. Mine waste
use may be resolved by analyzing samples to determine if their uranium content
is depleted.
Log-normal plots of ambient gamma radiation levels in Edgemont and Dudley
appear to indicate near background levels except for the First and Second
Avenue areas; the verified anomaly locations; and the Edgemont school area.
Two additional areas, located on the west side of Edgemont, recently had some
of their topsoil removed. Comparison of gamma measurements in the scraped and
undisturbed areas indicate that the topsoil may be contaminated with
radionuclides. These areas should be further investigated.
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Gamma radiation surveys in Cottonwood indicate that this area has elevated
surface contamination as a result of wind and water erosion of the nearby
tailings piles. All structures in Cottonwood may be considered as tailings
locations. The estimated average net gamma external exposure rate for the
inhabited areas of Cottonwood is 158 mR/yr, ranging from 53 to 412 mR/yr.
This does not mean, however, that gamma radiation is the only source of radia-
tion exposure to persons living in the vicinity of the mill site. Inhalation
and ingestion of airborne tailings and radon progeny will also contribute to
additional human exposures. These exposure sources should be fully evaluated.
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EQUIPMENT DESCRIPTION
Mobile Radiation Scanner
Since the radionuclides contained in uranium mill tailings emit abundant
and relatively energetic gamma radiation, they may be detected remotely by
means of a sensitive gamma radiation detector. In order to locate possible
tailings use sites and to evaluate human radiation exposure, we built a mobile
radiation detector. The detector was a large sodium-iodide crystal shielded
on the bottom and sides to reduce terrestrial background radiation. The
shield contained a port to enhance the crystal's response to gamma radiation
coming from a particular direction. The detector assembly was mounted in a
van-type vehicle and was operated as a gross gamma-ray-rate meter. An analog
output of the rate meter was presented on a strip chart or log. While the
meter output was being recorded, the log was observed for increased count
rates caused by radiation sources in the proximity of the scanner. When an
increased count rate or anomaly was observed on the log, the location of the
vehicle was recorded by street address or other means. A more complete
description of the scanner and its use is available in the literature (Hans,
1977).
The gamma ray scanning vehicle used in the 1971-72 surveys contained a
modified well logging system using two 4" x 4" sodium iodide crystal detectors
connected in parallel. The detectors were mounted on the top of the right
rear end of the vehicle and were shielded in such a manner to observe areas to
the right side.
Portable Scintillometers
Several types of portable (hand held) Scintillometers were used to further
investigate anomalies identified with the mobile radiation scanner. These
investigations or follow-up surveys were conducted to verify, assess and more
precisely locate the radioactive materials causing the anomalies. The
following listing briefly describes the types of Scintillometers used.
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1. Ludlum Instruments Model 19 Scintillometer - This instrument, used in
the 1978 survey detects gamma radiation with a small sodium iodide
crystal coupled to a photomultiplier tube (PMT). The output 'signals
from the PMT are used to drive a linear rate meter having an exposure
rate range of 0-5000 yR/hr. Properly calibrated, this instrument can
provide a reasonable estimate of the gamma ray exposure rate from
uranium mill tailings or ore.
2. Rank (Baird Atomic) Model NE148A Scintillometer - This instrument oper-
ates basically in the same manner as the previously described Scintil-
lometer and was used for the follow-up surveys conducted in 1972.
3. Rank Model NE148A Scintillometer (modified) - This modified version was
used in the 1978 follow-up surveys. The rate-meter time constant was
increased to 10 seconds and a sliding lead shield assembly was attached
to the instrument body. The time constant was increased to reduce
meter fluctuations. The shield assembly helped to more precisely
locate uranium mill tailings and ore and to estimate the degree of
surface contamination.
Ion Chamber
A Reuter-Stokes Model RSS 111 ion chamber was operated in conjunction with
the mobile scanner to measure gamma ray exposure rates at selected locations.
The instrument consists of an ion chamber and electrometer coupled by a cable
to a digital rate meter and power supply. The ion chamber is pressurized to
increase its sensitivity to low level gamma exposure rates and is designed to
have a reasonably flat response to most gamma ray energies of interest.
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DISCUSSION OF THE 1971-72 SURVEY
Edgemont - Dudley - Cottonwood - Provo - Hot Springs (South Dakota)
A mobile gamma scanning unit was operated by the U.S. Atomic Energy Com-
mission contractor Lucius Pitkin, Inc.,* under an interagency agreement for
the U.S. Environmental Protection Agency. After the mobile gamma scan was
completed, the recorder chart was forwarded to the Lucius Pitkin office in
Grand Junction, Colorado, where the chart with the anomaly addresses and notes
added by the operator were analyzed. An anomaly was defined as any location
where the recorded counts per second (c/s) exceeds the pre-determined back-
ground by 50 c/s. The anomaly report was sent to the National Environmental
Research Center-Las Vegas (NERC-LV)** and, in turn, forwarded to the South
Dakota Department of Health. Field teams used this report to conduct follow-
up surveys at each anomaly location. Table 1 lists, by location, the results
of this survey. Appendix B gives the physical location of the anomalies in
Edgemont and Appendix C gives the physical location of the anomalies in
Dudley.
The field teams were composed of two persons, each equipped with a port-
able radiation survey instrument. These instruments were calibrated at the
NERC-LV and a five-item field check was performed each day to determine if the
instrument was functioning properly. If the instrument did not operate within
pre-set ranges, it was not used.
**
Lucius Pitkin, Inc., Contractor for the Grand Junction, Colorado
Operations Office of the former U.S. Atomic Energy Commission (now
Department of Energy)
NERC-LV is now EPA Environmental Monitoring Systems Laboratorv-
Las Vegas (EMSL-LV) J
8
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TABLE 1. FOLLOW-UP SURVEYS OF THE ANOMALIES IDENTIFIED DURING THE 1971-72 SURVEY
LOCATION NUMBER+ HOG*
LOG**
HIG**<
COMMENTS
40 - 500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
70
40
100
15
50
40
25
80
50
30
30
30
40
30
50
40
45
30
100
35
30
50
35
35
130
50
21
100
20
80
21
18
22
20
20
10
10
9
12
40
30
20
60
40
20
25
25
25
25
40
20
15
12
30
20
10
12
9
16
14
13
13
14
12
12
10
12
13
13
10
NR****
NR
NR
11
18
NR
NR
NR
NR
18
NR
NR
16
NR
NR
NR
NR
NR
NR
18
10
12
NR
20
14
NR
14
15
11
NR
NR
NR
17
NR
11
Tailings north side of house
Tailings in front and south
front of house
Tailings east side of
building
Radium source
Wind blown tailings entire
yard
it H n ii M
H n n n n
n n M n n
n n n n n
Wind blown tailings on
north side of house
Wind blown tailings on
entire lot
ii ii n n n
Wind blown tailings in
entire yard
Wind blown tailings on
entire lot
M n ii n ii
Shine from tailings pile
Tailings at edge of highway
and railroad tracks
Tailings at edge of highway
on both sides
Tailings entire area
Shine from tailings pile
Tailings edge of highway
Tailings in driveway
Tailings in parking lot
Shine from mill
Tailings east side of bldg.
Tailings east side of lot
Tailings in entire yard
Tailings in yard and possible
ore sample in drive
Possible wind blown tailings
Tailings in driveway and yard
Wind blown tailings
West side of building
Tailings entire yard
Wind blown tailings entire
yard
Wind blown tailings on east
side of house
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LOCATION NUMBER*
40 - 535
536
537
538
^ f+ f\
539
r* A /\
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
HOG*
26
45
30
60
40
18
16
80
80
120
14
22
22
18
16
>3000
27
16
100
15
18
100
150
16
50
11
12
15
10
12
11
9
11
NR
11
10
15
12
11
LOG**
14
17
15
14
9
9
11
13
11
9
9
15
15
12
11
15
12
10
10
12
13
12
14
10
8
6
7
9
7
7
6
6
6
NR
6
5
6
7
7
HIG***
NR
16
NR
14
NR
NR
NR
NR
10
10
NR
NR
NR
NR
250
40
14
NR
NR
14
NR
100
NR
NR
8
NR
10
NR
9
NR
10
NR
10
NR
12
NR
10
NR
10
COMMENTS
Wind blown tailings entire
yard
Wind blown tailings and shine
ii ii M n H
Tailings in north and west yard
and southeast corner
Tailings in front lawn
Tailings east side and north-
west corner of yard
Tailings in front flower bed
and back steps
Tailings in rock garden and
picnic area
Tailings on entire lot
Wind blown tailings entire
park
Ore in basement
Ore samples
Tailings at south side of
building
j
Granite cornerstone
Tailings in gutter
Tailings in basement fill
and entire yard
Tailings in front and
south yard
High outside gamma entire lot
Tailings spots in front yard
Brick
Granite
10
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LOCATION NUMBER+ HOG*
LOG**
HIG***
COMMENTS
40 - 574 11 8
575 10 6
576 10 5
577 11 9
578 13 8
579 10 8
580 10 7
581 13 8
582 11 7
583 12 6
584 13 6
585 13 8
586 12 6
587 NR NR
588 11 7
589 11 7
590 15 6
591 NR NR
592 12 8
593 10 8
594 15 11
595 12 8
596 8 7
597 14 9
598 21 8
599 12 8
600 13 7
601 12 8
602 18 7
603 11 6
604 12 7
+ Location Number
Numbers 40-504 thru 40-559
Numbers 40-560 thru 40-604
Numbers 40-500 thru 40-503
* HOG Identifies the highest
that location (yR/hr)
** LOG Identifies the lowest
that location (yR/hr)
*** HIG Identifies the highest
recorded at that location
10
10
10
NR
NR
11
15
NR
NR
NR
15
NR
NR
NR
13
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
7
NR
NR
were assigned
were assigned
were assigned
outside gamma
outside gamma
Brick
Brick
HIG-shine from brick
Ore in rock garden in front
yard
Ore samples
Brick walls
Brick wall
Ore
Shale and Clay
Lower part of hillside
Grassy area
Northwest corner of building
and lawn
to Edgemont
to Hot Springs
to Provo
measurement recorded at
measurement recorded at
gamma measurement inside the structure
(yR/hr)
**** NR No gamma measurement was recorded
11
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A follow-up survey was performed at a location only after permission was
obtained from the owner or occupant of the property. Suspected tailings use
might have been determined while approaching the property or structure to
request permission. Once permission to survey was obtained, one surveyor
would monitor inside the structure and his partner would monitor the sur-
rounding outside property. A sketch of the property containing radiation
measurements made at three feet from surfaces was prepared for documentation
and future reference.
The mobile gamma scanning team reported sixty-one gamma radiation
anomalies from 560 structures scanned in Edgemont, South Dakota. Five of the
anomalies were duplicated. All of the anomalies were investigated, resulting
in the preparation of fifty-six Indoor Radon Study-Gamma Screening Forms. The
purpose of the form was to document the follow-up survey. Figure 2 is an
example of this form.
There were eight anomalies where no elevated radiation level could be
found. Three anomalies were identified as ore or direct radiation (shine)
from the uranium mill tailings pile. One anomaly was identified as natural
radioactivity present in granite. Forty-four of the fifty-six locations were
determined as possible tailings use locations. The forty-four possible
tailings use locations are identified as follows: two locations as probable
tailings use; sixteen locations as having tailings greater than ten feet from
the structure (tailings away-TA); twenty-five locations as having tailings
within ten feet of the structure (tailings under-TU); and the Edgemont uranium
mill site.
Two locations where uranium ore was found were habitable structures. Ore
specimens were stored in the basement at location 40-549 and gamma
measurements as high as 250 yR/hr were recorded. At location 40-550,
materials that appeared to be ore specimens were stored against the outside of
three walls. Gamma measurements exceeding 3,000 yR/hr were recorded next to
the materials; and the "shine" from the materials produced gamma measurements
as high as 40 pR/hr, inside the house. The gamma measurements recorded at
location 40-552 were caused by the granite stone used in the construction of
the structure.
12
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DAIL 101:11 ;;ofir'Lr.TLD
CARD
MUMPER
LOCATION NUMDCi!
Ill III
CITY COUNTY
i i n i i i i
2 3 4 5 G 7 8 9 10 11 12 13
ADDRESS
DIR. NAME
C^U L
I 1 1 1 1 1 1
iTATL
m
14 15
1 1 1
r.
1C
1
MONTH
n
17
1 1
YLAR
m
in 19
1 1 1
20 21 22 23 24 25 26 27 23 20 30 31 32 33 34 35 36 37 3fl 30 40
(Last Name first - Initials for first and middle name - husband and wl fc)
KPANTS i i i i i » i i II i i i i i i i i 1
°SRS
CLASSIFICATION
41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 5«
(Last Name First - Initials for first and middle name - husband and wife)
• i i i i i i i i i i j i i i i i n
59 60 61 62 63 64 65 66 67 63 69 70 71 72 73 74 75 76
(OWNERS ADDRESS _
GAMMA SCREEN
CZI
78
0. None
1. Completed
2. Occupant refusal
3. No - ask owner
4. Owner refusal
5. No one to contact
0. Vacant Lot
1. Residence single family
2. Multiple (<4 families)
3. Apartment (>4)
4. Motel, hotel, or hospital
5. Single business (in one unit)
6. Multiple business unit(connected) 6. No bad address
TAILINGS USE
cn
79
0. None
1. Under
t ?. Away
GAMMA MAP
cn
80
0. None
1. Yes
2. Occupant
- No
7. School
8. Church
9. Other
CARD
7. Outside only
3. Under-Away 3. No ask owner
4. Possible 4. Owner - No
3. Special scheduling 5. Unknown
9. Other
LOCATION NUMBER
CITY
COUNTY
LOCATION
CODE
M I I I I I I I I I MM
23456 7 R 9 10 11 1? 13 14 15
Township Section l.'4>c. Block Owner Number
5. No one to see
6. Not required
STATE
Lot
i i i i i
16 17 18 19
HOG
20 ?.\
LOG
22
24
25 26
Hlfi
27
28 29 30
LOCATION HIG
il 111 1
31 32 33 34 35
TYPE OF HOUSE
I I
47
1. Basement
2. SI ab on grade
3. Crawl space
FREE PUNCH COMMENT
'' i i i n i i i
36 37 38 39 40 41 42 43 44
45
46
NUMBER OF LEVELS
MATERIAL
r
i
48
49
0. Bedroom
1. Living Room
2. Kitchen
3. Den-Family Rm.
4. Dining Room
5. Attached garage
1- Masonry
2. Non masonry 6. Basement
7- "ork shop
9. Other
9. More than one
location
1 1 1
50 51 52
1 1 1
66 67 68
| |
53 54
1 1
69 70
1 1 1
55 56 67
1 1 1
71 72 73
1 1 1 1 1 1
58 69 60 61 P2 63
1 i 1 1 1 1
74 75 76 77 7fl 7°
III
64 65
1 1
80
Figure 2. Indoor Radon Study-Gamma Screening Form
13
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Locations 40-515 and 40-519, listed as possible tailings locations, were
both in close proximity to the uranium mill tailings pile. Because of this, a
positive identification of tailings was not possible. Gamma measurements made
at ground level were 40 yR/hr; and measure-ments made about seven feet from
the surface of the ground, representing "shine" from the pile, were 35 yR/hr.
Since the surface measurements at location 40-523 were 30 yR/hr and the
other measurements at 3 feet and 6 feet above the ground surface were 35
yR/hr, the surveyors believed the reported anomaly was caused by "shine" from
the tailings pile and not a deposit of tailings on the property.
There were sixteen locations where tailings were found more than ten feet
away from a habitable structure. There were vacant lots at ten of these
locations (40-508; 40-510; 40-511; 40-513; 40-514; 40-516; 40-517; 40-525;
40-546; 40-547). At the other six locations (40-520; 40-521; 40-522; 40-530;
40-544; 40-553) there were habitable structures, but the material was more
than ten feet from these structures. Exposure rates as high as 120 yR/hr were
measured.
Twenty-five locations are listed where tailings were found under or within
ten feet of a habitable structure. The tailings deposits found at sixteen of
these locations were caused by wind blown material from the mill site tailings
piles. This wind migration deposited tailings against all of the structures
and produced gamma exposure rates as high as 100 yR/hr. At eight of the
twenty-five locations (40-524; 40-529; 40-538; 40-542; 40-543; 40-551; 40-557;
40-559), the tailings had been hauled onto the property for various uses.
Gamma measurements as high as 130 yR/hr were recorded against the outside of
the structures. At the remaining location (40-556), tailings were used
beneath the basement floor slab or as fill material around the basement walls,
and also in the yard.
14
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The mobile gamma scanning unit reported forty-five gamma radiation
anomalies from 1,178 structures scanned in Hot Springs, South Dakota. All of
the anomalies were investigated, resulting in the preparation of forty-five
Indoor Radon Study-Gamma Screening Forms.
There were twenty-five anomalies where nothing was found or where the
resident refused permission to investigate further; three anomalies were from
radioactive material present in ore; and seventeen anomalies were due to
naturally occurring radioactive materials.
Uranium ore was found at three locations. At location 40-585, the ore was
located in a front-yard rock garden; and gamma measurements up to 800 uR/hr
were recorded. Numerous ore samples were found at location 40-588 and the
gamma measurements exceeded 3,000 yR/hr. At location 40-596, the ore was on a
vacant lot and appeared to be a natural geological occurrence. Gamma
measurements to 250 yR/hr were recorded at this location.
The mobile gamma scanning unit reported four gamma radiation anomalies
from twenty-two structures scanned in Provo, South Dakota. All of the
anomalies were investigated, resulting in the preparation of three Indoor
Radon Study-Gamma Screening Forms. The reported gamma anomaly at location
40-503 was due to a radium source in a sealed glass bottle inside the
residence. Gamma measurements, made at the surface of the bottle, exceeded
3,000 yR/hr. The reported anomalies at the remaining three locations were
apparently caused by tailings deposits. At two of these locations (40-501 and
40-502) the radioactive material was present on property which had habitable
structures. However, the apparent tailings deposits were more than ten feet
away. The deposit at location 40-501 was along a ditch bank and gamma
measurements as high as 40 yR/hr were recorded. At location 40-502 the mater-
ial was next to the street and at the driveway entrance. Gamma measurements
as high as 100 yR/hr were recorded at this location. Location 40-500 was a TU
location since the apparent tailings deposit was up against the north side of
the residence. Gamma measurements as high as 70 yR/hr were recorded over the
deposit; however, the residence was vacant at the time of the survey and the
surveyors were unable to enter the structure to obtain inside measurements.
15
-------
DISCUSSION OF THE 1978 SURVEY
The Edgemont area was logged with the previously described mobile scanner.
The equipment operator would observe the trace being made on the recorder,
watching for count rates (anomalies) above background for that immediate area
being recorded. When an anomaly was observed, the street address or other
identifying landmark was listed by a second person designated as an observer-
recorder. This list of anomalies was then used by gamma survey teams to
further investigate the anomalies.
The gamma survey teams were composed of two members. One member was
equipped with a portable scintillometer and the second team member was
equipped with the gamma screening form. The gamma survey instruments were
calibrated at EMSL-LV calibration facility using a Ra-226 standard source
traceable to the National Bureau of Standards (NBS). The Gamma survey
instruments were checked everyday for proper operation. If an instrument did
not check out, it was not used by the survey team.
A survey of a suspected anomaly location was performed only after permis-
sion was granted by the owner or occupant of the property. Once permission
was obtained the survey team would survey the outside of the property. Radia-
tion measurements were made at three feet above the ground level and on the
surface. Sufficient radiation measurements were taken and recorded to
determine the approximate boundaries of the radioactive materials. When sus-
pected tailings were located within ten feet of a structure, an indoor gamma
survey of the structure was completed and recorded. For some locations, where
the occupant of the property could not be located after several tries, a quick
radiation survey was done around the property boundary to try to determine if
tail'ings were used.
The mobile scanner identified eighty-four anomalies in the communities of
Dudley and Edgemont. The eighty-four anomaly locations were broken down as
follows: seventeen locations identified as possible tailings use; sixteen
locations identified as radiation sources other than tailings; and fifty-one
16
-------
locations Identified as having no radiation sources. Nine gamma radiation
survey sketches were drawn for six locations; 7811-66, 7811-80, 7811-81,
7811-82, 7811-83, 7811-84. The gamma sketches are located in Appendix A. A
contaminated bottom-dump earth scraper was found at location 7811-62.
Some large open areas showed significant gamma radiation differences as
compared to the general background. Locations 7811-81, 7811-83, and 7811-84
were examples of these differences. Location 7811-81 was a newly constructed
log building located approximately in the center of a parking lot. The
parking lot had been scraped and cinders added as a top cover. The gamma
measurements increased toward the south side and northeast edge of the
parking lot. A pile of scrapings was located at the extreme west edge of the
lot, and a gamma measurement taken on top of the pile was 25vR/hr. One com-
mercial enterprise west of Edgemont on Highway 18 had a large scraped area
with a metal building located on it. When the mobile scanner was driven into
the lot the count rate dropped from about 600 counts per second (c/s) to about
400 c/s. The measurements made at both scraped areas tend to indicate the
presence of surface contamination. Locations 7811-83 and 7811-84 showed
significant increases above the general background. These two areas were
generally undisturbed and were covered with grass and weeds. Table 2 is a
listing of the anomalies identified during the 1978 survey. Appendix B gives
the physical location of the anomalies in Edgemont and Appendix C gives the
physical location of the anomalies in Dudley.
17
-------
TABLE 2. FOLLOW-UP SURVEYS OF THE ANOMALIES IDENTIFIED
DURING THE 1978 SURVEY
LOCATION NUMBER HOG* LOG**
7811 - 01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
. 31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
23
23
23
23
19
19
18
20
22
20
19
21
20
20
22
20
15
18
18
25
20
15
20
23
22
20
20
22
24
23
23
22
15
15
15
20
20
18
NR
20
23
18
19
20
23
18
15
13
14
15
15
17
16
17
18
16
17
16
17
18
16
15
15
15
15
15
15
12
17
17
17
15
18
17
19
17
17
15
15
15
15
15
11
NR
17
19
13
14
15
16
NR****
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
lUI'll'lL
Anomaly not
n n
M n
n n
n n
it n
n n
n ii
ii M
n ii
n ii
M n
M n
n n
n n
n n
ii n
n n
ii n
n n
ii n
it n
ii n
ii n
ii n
n n
n n
n n
n ii
ii n
ii n
" it
ii n
» n
ii n
" II
II II
H II
Shine from
Anomaly not
ii n
ii n
H II
II II
111 O
conf i rmed
it
n
ii
n
ii
n
n
n
n
n
n
n
n
n
n
„
„
„
„
„
„
„
„
„
„
„
„
„
„
„
„
„
II
„
„
„
II
next lot east
confirmed
„
„
„
„
18
-------
LOCATION NUMBER HOG* LOG** HIG*** COMMENTS
7811 - 46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
23
23
17
200
25
27
120
44
250
1000
23
90
24
34
50
35
120
20
235
27
140.
220
200
50
70
60
30
40
18
18
17
15
14
17
17
17
18
14
18
17
16
19
15
15
35
17
18
18
15
17
20
16
20
15
17
17
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
50
NR
28
NR
NR
NR
NR
NR
NR
NR
Anomaly not confirmed
ii ii it
Ore samples in trailer behind
house
Rock in backyard
Brick building
Sandstone foundation and rock
garden
Possible ore in basement
Rock-possible ore
Small area in back yard
-possible ore
Rock-possible ore
Sand in flower bed-possible
tailings use
Rock in yard-possible ore
Rock pile near carport
-possible ore
Hot rock and stone facing on
house-possible ore
Small spot in driveway
-possible ore
Small spot at SE corner of
house-possible tailings use
Bottom dump scraper and
immediate area scraper may
have been used in Cottonwood
-possible tailings location
Anomaly not confirmed
Possible ore in flower bed
Possible tailings in
backyard retaining wall
Possible tailings use in
flower bed
Fill hauled from across
street-possible tailings
Backyard fill -possible
tailings
Backyard fill -possible
tailings
Fill in yard-possible
tailings
Fill in yard-possible
tailings
Possible tailings use in yard
Possible tailings use in
parking lot
19
-------
LOCATION NUMBER HOG1'
LOG**
HIG***
COMMENTS
7811 - 74 40
75 25
76 18
77 23
78 22
79 23
80 240
81 28
82 60
83 23
84 20
17
16
13
17
19
12
17
18
15
17
16
NR
NR
NR
NR
NR
NR
49
NR
NR
NR
NR
Stucco-brick and petrified
wood-possible use of
tailings in stucco
Possible tailings use in
cement
Anomaly not confirmed
Fill along basement wall
-possible tailings use
Possible mine wastes
Flower bed-possible tailings
use
Possible mine wastes
Possible mine wastes
* High Outside Gamma
** Low Outside Gamma (yR/hr)
*** High Inside Gamma (uR/hr)
**** NR - No Measurements Made
20
-------
DISCUSSION OF ADDITIONAL GAMMA RADIATION MEASUREMENTS MADE IN
EDGEMONT AND VICINITY DURING THE 1978 SURVEY
A Reuter-Stokes Model RSS-111 pressurized ion chamber (PIC) was carried and
operated in the mobile scanner van during the 1978 survey. The ion chamber
detector was placed on the floor in the rear of the van and its read-out unit
was placed in the front of the van for viewing access. Most of the PIC
measurements were made on street intersections and measurements were made each
time the van entered an intersection. Consequently, more than one PIC
measurement generally was made at each intersection.
Some gamma ray shielding of the ion chamber occurs from the van structure
(i.e., metal floor and frame). The shielding factor for the van was
previously determined to attenuate the ambient exposure rate by 17 percent.
PIC measurements made in Edgemont, Dudley, and Cottonwood are listed in
Table 3. The table contains the measurement locations, gross exposure rates
at each location, and the exposure rates corrected for van shielding. The
physical location of the PIC measurements for Edgemont and Dudley are given in
Appendices B and C respectively.
All corrected exposure rates are plotted on log-probability paper to
determine their distribution characteristics (Figure 3, Plot A). The data on
plot A belongs to two distributions which end and begin near the 70 percentile
line. All data below the 74 percentile line were ranked and plotted (Plot B).
The slope or Standard Geometric Deviation (SGD) of Plot B is 1.04 and strongly
indicates that the data in this group indicates background conditions (Denham,
1975). A relatively uniform deposition of mill wastes over the Edgemont area
would also produce a similar SGD. The geometric average Qfg) or 50 percentile
value for Plot B is about 12 pR/hr. Therefore, the ambient gamma radiation
background in Edgemont and Dudley was about 12 ± 1 yR/hr at the 95 percent
confidence level. The geometric average compares well with the arithmetic
average of 12.4 yR/hr computed in Table 3.
21
-------
TABLE 3. PIC MEASUREMENTS EDGEMONT, DUDLEY, COTTONWOOD
EDGEMONT
NUMBER OF
LOCATION MEASUREMENTS
"A" St. 2nd Ave.
3rd Ave.
4th Ave.
5th Ave.
6th Ave.
7th Ave.
10th Ave.
"B" St. 2nd Ave.
3rd Ave.
4th Ave.
5th Ave.
6th Ave.
7th Ave.
"C" St. 2nd Ave
3rd Ave.
4th Ave.
5th Ave.
6th Ave.
7th Ave.
10th Ave.
11 D" St. 2nd Ave.
3rd Ave.
4th Ave.
5th Ave.
6th Ave.
7th Ave.
10th Ave.
3
2
3
3
4
4
2
2
4
4
4
4
4
4
4
4
4
4
4
4
3
4
4
4
4
4
1
AVERAGE EXPOSURE
RATE (uR/hr)
10.0
9.9
9.6
10.4
9.8
10.5
11.2
10.7
10.3
10.2
10.8
9.9
10.5
9.8
10.5
10.8
10.7
10.3
10.2
12.2
10.0
10.3
10.2
10.5
10.0
10.8
12.2
22
CORRECTED AVERAGE
EXPOSURE RATE (uR/hr)
11.7
11.5
11.3
12.2
11.4
12.3
13.1
12.5
12.0
11.9
12.6
11.6
12.3
11.4
12.3
12.6
12.6
12.1
11.9
14.2
11.7
12.0
11.9
12.2
11.7
12.6
14.3
-------
LOCATION
"E" St. 2nd Ave.
3rd Ave.
4th Ave.
5th Ave.
6th Ave.
7th Ave.
8th Ave.
9th Ave.
10th Ave.
"F" St. 2nd Ave.
3rd Ave.
4th Ave.
5th Ave.
6th Ave.
7th Ave.
8th Ave.
9th Ave.
"G" St. 2nd Ave.
3rd Ave.
4th AVe.
5th Ave.
6th Ave.
7th AVe.
11 H" St. 2nd Ave.
3rd Ave.
4th Ave.
5th Ave.
6th Ave.
NUMBER OF
MEASUREMENTS
4
4
4
4
4
5
3
3
3
5
4
4
4
5
5
3
2
4
5
4
4
6
2
1
4
5
3
2
AVERAGE EXPOSURE
RATE (uR/hr)
10.1
10.1
10.4
10.3
10.0
10.2
10.9
11.0
11.0
9.7
10.2
9.9
11.3
10.7
10.8
11.1
11.2
10.5
10.3
10.3
11.3
10.9
11.1
9.3
9.7
10.2
10.4
10.5
CORRECTED AVERAGE
EXPOSURE RATE (yR/hr)
11.9
11.8
12.2
12.1
11.7
12.0
12.8
12.9
12.9
11.4
11.9
11.6
13.2
12.5
12.6
13.0
13.1
12.3
12.1
12.1
13.3
12.7
12.9
10.9
11.4
12.0
12.1
12.2
23
-------
LOCATION
NUMBER OF
MEASUREMENTS
AVERAGE EXPOSURE
RATE (yR/hr)
CORRECTED AVERAGE
EXPOSURE RATE (uR/hrj
"H" Extension
City Well No. 2
Hospital
Ai rport
"C" St. School
Alley
School Complex
Ball Field
1
1
1
2
1
1
----- — ^ r., . f ... t
10.8
9.3
11.6
12.3
12.6
13.0
12.6
10.9
13.6
14.2
14.7
15.2
II nil
E" and "F" Streets
10.8
12.7
Cul-de-sac
off "C" Street
12.0
14.0
West Side Railroad
at Route 18
11 "A" Street
11 "B" Street
" "C" Street
" "D" Street
11 "E" Street
North End 4th Avenue
" 5th Avenue
3rd and Lawrence
4th "
3rd and Hansen
1
2
1
1
1
1
1
1
1
1
1
12.0
11.5
11.2
11.0
11.4
10.6
11.7
10.7
9.7
10.0
10.2
14.0
13.4
13.1
12.9
13.3
12.4
13.7
12.5
11.4
11.7
11.9
Top of Hill Mobile
Home Park, Southeast
Corner of Town
10.0
11.7
24
Average12.4
-------
LOCATION
A
B
C
D
E
F
LOCATION
1
2
3
4
5
6
7
8
9
10
NUMBER OF
MEASUREMENTS
1
1
1
1
1
1
NUMBER OF
MEASUREMENTS
1
1
1
1
1
1
1
1
1
1
DUDLEY
AVERAGE EXPOSURE
RATE (uR/hr)
10.5
10.3
11.0
10.2
9.6
11.3
COTTONWOOD
AVERAGE EXPOSURE
RATE (yR/hr)
19.3
15.7
12.3
12.5
13.5
19.5
18.0
21.0
18.6
14.5
CORRECTED AVERAGE
EXPOSURE RATE (uR/hr)
12.3
12.1
12.9
11.9
11.2
13.1
Average 12.3
CORRECTED AVERAGE
EXPOSURE RATE (wR/hr)
22.6
18.4
14.4
14.6
15.8
22.8
21.1
24.6
21.8
17.0
Average 19.3
25
-------
er>
100
9
8-
o
d
10
9 *-
d 6
o o
s
CL
10
m
00 0» 0>
10 20 30 40 50 60 70 80 90 95 98 99 S S §
_ Plot A
XgM^iR hr
SGD~1.08pR hr
100
9_
8_
7_
6_
5_
4—
CO
0
a
I
ee
10
Plot B
fl = 12fiR/hr
SGD?1.04
Key:
Dudley t
Cotton wood I
Edgemont*
i- 10
99
o o
10
d
5 10 20 30 40 SO 60 70 80 90 95 98 99
Cumulative Percent
op
o> o>
o>
o>
oi
o>
Figure 3. Log-Probability Plot of PIC Measurements
-------
All of the PIC measurements made in Cottonwood are not in the background
distribution. These measurements are discussed later in this report.
Seven PIC measurement locations in Edgemont were in excess of 13.4 yR/hr
(Xg + 3 SGD). These are:
1. C St. and 10th Avenue
2. C St. and school alley
3. D St. and 10th Avenue
4. C St. and school complex
5. C St. and school ballfield
6. H St. extension and airport
7. North end of Fourth Avenue
Locations 2, 4 and 5 above are on the school complex which has suspected
mine waste use. Locations 1 and 3 are probably caused by gamma radiation from
adjacent anomalies. The cause of elevated gamma exposure rates at locations 6
and 7 is not known.
Since nearly all of the PIC measurements were made on streets, there is a
possibility that the measurements may be lower than adjoining areas. This is
because the streets are paved or dirt and would have less retention of air-
borne deposition of mill wastes. In order to compare on and off-street
exposure rate levels, all Tow outside gamma (LOG) measurements made at non-
tailings locations during the 1978 survey were tabulated and ranked in Table
4. Like values were grouped and plotted on a Tog-probablity graph (Figure 4).
The data points appear to fall in one distribution and have a slope or (SGD)
of 1.1 indicating that they are ambient background measurements. The
geometric average, or 50 percent percent!le value, of the data points is about
13 wR/hr with a SGD of 1.1 yR/hr. There appears to be no statistical dif-
ference between the PIC measurements made on the streets and the corrected
scintillometer measurements made in off-street areas.
27
-------
These measurements do not imply that Edgemont or Dudley contain no air-
borne deposition of mill wastes. Large portions of 1st and 2nd Avenues in
Edgemont were found to contain wind blown tailings during the 1971-72 survey.
Ten PIC measurements were made in a campground directly north of the mill
site across the Cheyenne River. The corrected measurements ranged from 12 to
14 yR/hr. Some of the measurements were made on disturbed or bladed ground.
The high PIC and a delta measurement were made on relatively undisturbed
ground. Both measurements indicate surface contamination in that area
probably caused by wind blown tailings. The term "delta" is defined in the
next report section.
28
-------
TABLE 4. LOW OUTSIDE GAMMA (LOG) SCINTILLOMETER MEASUREMENTS AT LOCATIONS
WHERE TAILINGS WERE NOT USED - 1978 SURVEY
CORRECTED
RANK LOG (yR/hr) LOG (uR/hr) CUMULATIVE % LOCATION NUMBER
1 11 11 .75 7811 - 38
2 12 11.5 2.24 23
3 12 11.5 3.73 79
4 13 12.0 5.22 03
5 13 12.0 6.72 42
6 13 12.0 8.21 76
7 14 12.4 9.70 04
8 14 12.4 11.19 43
9 14 12.4 12.69 50
10 14 12.4 14.18 55
11 15 12.9 15,67 02
12 15 12.9 17.16 05
13 15 12.9 18.66 06
14 15 12.9 20.15 17
15 15 12.9 21.64 18
16 15 12.9 23.13 19
17 15 12.9 24.63 20
18 15 12.9 26.12 21
19 15 12.9 27.61 22
20 15 12.9 29.10 27
21 15 12.9 30.60 33
22 15 12.9 32.10 34
23 15 12.9 33.58 35
24 15 12.9 35.07 36
25 15 12.9 36.57 37
26 15 12.9 38.06 44
27 15 12.9 39.55 49
28 15 12.9 41.04 60
29 15 12.9 42.54 61
30 16 13.2 44.03 08
31 16 13.2 45.52 11
32 16 13.2 47.01 13
33 16 13.2 48.51 16
34 16 13.2 50.00 45
35 16 13.2 51.50 58
36 16 13.2 53.00 75
37 17 13.8 54.48 07
38 17 13.8 55.97 09
39 17 13.8 57.46 12
40 17 13.8 58.96 14
41 17 13.8 60.45 24
42 17 13.8 61.94 25
43 17 13.8 63.43 26
44 17 13.8 64.93 29
29
-------
RANK
LOG (uR/hr)
CORRECTED
LOG (yR/hr)
CUMMULATIVE %
LOCATION NUMBER
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
17
17
17
17
17
17
17
17
17
17
18
18
18
18
18
18
18
18
18
18
19
19
19
13.8
13.8
13.8
13.8
13.8
13.8
13.8
13.8
13.8
13.8
14.1
14.1
14.1
14.1
14.1
14.1
14.1
14.1
14.1
14.1
14.6
14.6
14.6
66.42
67.91
69.40
70.90
72.39
73.88
75.37
76.87
78.36
79.85
81.34
82.84
84.33
85.82
87.31
88.81
90.30
91.79
93.28
94.78
96.27
97.76
99.25
7811 - 31
32
40
48
51
52
53
57
63
77
01
10
15
28
41
46
47
54
56
81
30
59
78
30
-------
10
9 —I
5-
4-
x. 9-
~, 8-
•^
Q 7-
6—
5-
Xg 13.2(}iR/hr)
SGD 1.1
O
ill
in «- CM
9 6 6
in
6
i
2
I
5
I I I I T I I \
10 20 30 40 50 60 70 80
90 9
IS 98 9
I I I
99.9 99.99
Cumulative Percent
Figure 4. Log-Probability Plot of (LOG) Scintillometer Measurements
-------
DISCUSSION OF GAMMA RADIATION MEASUREMENTS MADE IN COTTONWOOD
DURING THE 1978 SURVEY
The community of Cottonwood is located to the southeast of Edgemont and
adjacent to the Edgemont uranium mill site. Over 50 percent of the peri-
meter area of the developed portions of Cottonwood is bounded by tailings
piles. The closest habitable structure to a tailings pile is approximately
150 feet. The location of Cottonwood, with respect to the surrounding
tailings piles, has subjected this area to wind and water eroded tailings.
Because of the elevated exposure rates from the adjacent tailings piles,
Cottonwood could not be logged with the scanner van. Some radiation
measurements, however, were made with a PIC and a modified Rank Model NE148
scintillometer. The PIC measurements were made with the unit in the scanner
van at street intersections. Figure 5 gives the measurement location and the
gross corrected PIC measurement (i.e., corrected for the van shielding). The
scintillometer used was modified to permit estimates of surface contamination
while in the presence of an external gamma radiation field (i.e., adjoining
tailings piles). The scintillometer's ratemeter time constant was increased
to minimize subjective averaging by the operator and a sliding lead shield was
added to the bottom of the instrument. The shield could be interposed between
the instrument's detector and the ground. Two ground measurements were made
at each measurement location: one with the shield away from the detector
(open reading) and one with the shield under the detector (closed reading).
The difference between the two readings (delta (A)} is indicative of ground
contamination. The magnitude of A provides an estimation of the quantity of
surface contamination. The relationship between A and above ground exposure
rates as well as the quantity of surface contamination by mill tailings has
been previously determined (Hans, 1977).
Figure 6 1s a map of Cottonwood showing the location and magnitude of A
measurements. Table 5 lists the 24 measurement locations and the scintil-
lometer measurements made at three feet above the ground and the shielded and
unshielded measurements made in contact with the ground. The average gross A
value made over the Cottonwood area was 12. Assuming a typical background A
32
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TABLE 5. SCINTILLOMETER MEASUREMENTS IN COTTONWOOD
LOCATION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18*
19
20
21
22
23
24
3 FEET ABOVE GROUND
OPEN SHIELD (uR/hr)
59
26
20
18
22
35
30
46
41
24
20
24
35
35
41
33
24
20
20
22
28
50
28
22
SURFACE OPEN
SHIELD (yR/hr)
110
45
30
26
35
70
55
85
75
45
30
50
70
65
70
55
40
30
30
35
55
100
50
40
SURFACE CLOSED
SHIELD (vR/hr)
95
35
25
19
25
50
40
60
60
35
20
35
55
50
60
45
25
25
27
25
45
80
40
30
(A) DELTA
uR/hr
15
10
5
7
10
20
15
25
15
10
10
15
15
15
10
10
15
5
3
10
10
20
10
10
Arithmetic Average 30
Arithmetic Average 12
* New Area for Mobile Homes
33
-------
f t
.'I
u
i
o
U
1
£J
1
N
•
7
n m
D -
•
^
nx"^N
D @)
D 3
a
1
•
0
TRAILER
cru
CD
TRAILER
£J
C
a
u
g
. — .
D"
c
^
g TRAILER
]
am
9
TRAILER
CZU
• n
1
(24^6)
M TRAILER
• !~3
D *
(21.8)
Q * *
•
Q-aD ',
TRAILER 1
II
II
I]
II
II
II
•o
I
li
i i
11
M
"i'
r
"ETERS
Key:
Inhabited
Not Inhabited
PIC Measurement
1-Measurement Location
Figure 5. Gross Corrected PIC Measurements in Cottonwood
34
-------
Jt
V
•o
o
I
o
N
(?0
5)y^S. /^
CD
SA ® A
TRAILER
n
TRAILER
20>io>
•••
TRAILER
'
Ll
TRAILER
•ft
TRAILER
0
•o
o
Q.
•* i
r
Key:
Inhabited
Not Inhabited
Measurement Location
DeltaAMeasurement
Figure 6. Delta (A) Measurements in Cottonwood
35
-------
measurement of 4 for local natural soils, the net average A value for the
Cottonwood area would be 8. This net A value of 8 corresponds to an estimated
surface contamination of 50 pCi/cm2 for radium-226 (derived from
measurements made at other mill sites). Assuming a soil density of 1.6 g/cm3
and the contaminants averaged over a depth of 5 cm, the radium-226 surface
contamination would be equivalent to a net radium-226 concentration in the
soil equal to 6 pCi/g. The net average above ground exposure rate estimated
for the surface deposition is about 11 yR/hr. This agrees reasonably well
with the average net corrected scintillometer measurements of 18 uR/hr for the
Cottonwood area (i.e., 30 yR/hr - 12 yR/hr). It appears that most of the
above ground exposure rates in Cottonwood result from surface deposition. The
difference of 7 yR/hr between the estimated exposure rate from the average net
corrected exposure rate minus the exposure rate from deposition may be due
from "shine" from the adjacent tailings piles.
The arithmetic average of the net above ground exposure rates based on the
corrected scintillometer measurements is 18 yR/hr. This amounts to an average
annual exposure of 158 mR ranging from 53 to 412 mR for the Cottonwood area.
The average of the corrected gross PIC measurements made on the street
intersections in Cottonwood was 19 yR/hr (Table 3). The average of the net
PIC measurements is 7 yR/hr. The reason that the net PIC measurements do not
agree with the average net corrected scintillometer measurements (i.e., 18
yR/hr) is that the streets probably contain less contamination than the
adjacent vegetated areas.
In summary, most of Cottonwood contains eroded mill tailings and these
tailings produce an annual net average exposure rate of 158 mR ranging from 53-
to 412 mR. The average surface contamination, estimated from indirect
measurements, is approximately 50 pCi/cm2 of radium-226 averaging about 12
pCi/g. The Cottonwood population exposures to radon progeny and airborne
tailings particulates were not evaluated.
36
-------
REFERENCES
Denham, D. and D. Waite (1975), Some Practical Applications of the Log-Normal
Distribution for Interpreting Environmental Data. Paper presented at the 20th
annual meeting of the Health Physics Society, Buffalo, NY, 14-17 July, 1975.
FBDU (1978), Engineering Assessment of Inactive Uranium Mill Tailings -
Edgemont Site, Edgemont, South Dakota, (May, 1978). Ford, Bacon and Davis
Utah, Inc., 375 Chipeta Way, Salt Lake City, Utah 84108.
Hans, J. (1977), Gamma Radiation Surveys Around Uranium Mill Tailings Piles.
Workshop on Methods for Measuring Radiation in and Around Uranium Mills, May
23-26, 1977. Atomic Industrial Forum, Inc., 7101 Wisconsin Ave., Washington,
D.C. 20014.
Hans, J., 6. Eadie, J. Thrall and B. Peterson (1978), Above Ground Gamma Ray
Logging for Locating Structures and Areas Containing Elevated Levels of
Uranium Decay Chain Radionuclides, April 1978, Technical Note ORP/LV-78-2,
U.S. Environmental Protection Agency, Office of Radiation Programs, Las Vegas
Facility, Las Vegas, NV 89114.
37
-------
APPENDIX A
Sketches of Locations and Gamma Radiation Measurements
Made During the 1978 Survey
38
-------
40/40
•W
Contact on Wall
^.S® 3' ht 50>jR/hr
49/33
I
N
32/24
-34/24
32/24
31/24
w
I
31/29
32/26
Key: 34?24XX
*3 Foot Measurement injjR/hr (Gross Uncorrected)
xxSurface Contact Measurement in/jR/hr (Gross Uncorrected)
Figure A-2-a. Location 7811-80 - Basement
39
-------
Bd Rm
21/25
Bd Rm
20/23
20/31
26/24
0)
V)
£
O
Bd Rm
22/21
22/24
Bd Rm
-------
I
12/17
14/12
15/15J
d
24/30
140 uR/hr
Bottom of basement
window welt
240>iR/hr
I
60/85
35/42
17/20
19/19
35/50
17/15
22/28
21/19
NOTE: SANDSTONE USED IN FIRE PLACE. YARD AND AROUND HOUSE MEASURED 75 ;jR/hr
AT CONTACT.
Key: 14/12**
X3 Foot Measurement tnjiR/hr (Gross Uncorrected)
""Surface Contact Measurement in>iR/hr (Gross Uncorrected)
Figure A-2-c. Location 7811-80 - Outside of House
-------
/ 25.uR/hr /
(?) V <^-^
Dirt Pile
®
27/27
o
Q.
25/25
20/21
® 26/28 21/22
20/20
Key: 2$20XX
X3 Foot Measurement injaR/hr (Gross Uncorrected)
Surface Contact Measurement injaR/hr (Gross Uncorrected)
Figure A-3. Location 7811-81
42
-------
28/32
50/60
-15"
30'
•15'-
50/60
40'
HOUSE
II
STREET
Key: 5$60XX
X3 Foot Measurement injuR/hr (Gross Uncorrected)
""Surface Contact Measurement injuR/hr (Gross Uncorrected)
Figure A-4. Location 7811-82
43
-------
17/5\12
School Yard
Athletic Field
22/17
Bldg
Bldg
Bldg
Gym
17/17
1 8/20
17/17
20A17
>/3\
OJ
2
CD
Tennis Courts
18/20
"Ail
lev
II!
H
a
Key: 18"/20"
"3 Foot Measurement in>jR/hr (Gross Uncorrected)
Surface Contact Measurement in jiR/hr (Gross Uncorrected)
Shield Open Measurement Ashield Closed Measurement
Shield OpervShield Closed
>- gross PIC (uR/hr)
Figure A-5-a. Location 7811-83 & 7811-63 - Edgemont School Area
44
-------
Baseball
23^17
O
Bldg
Football
Edgemont School
Athletic Field
Key:
Shield Open Measurement/^Shield Close Measurement
Shield Open-Shield Closed
15.2) PIC Measurement tuR/hr)
Figure A-5-b. Locations 7811-83 & 7811-63 - Edgemont School Area
45
CO
o
z
o
DC
DC
1U
-------
10th Ave
(A
XJ
3
O
(5
u
Location 7811-84
O
2
O
0)
Q
WJ
00
D>
I
Key: 18X/20"X
"3 Foot Measurement injjR/hr (Gross Uncorrected)
""Surface Contact Measurement in juR/hr (Gross Uncorrected}
Shield Open Measurement AlShield Closed Measurement
Shield OpetTshield Closed
Figure A-6. Location 7811-84 - Fall River County Fairgrounds
46
-------
APPENDIX B
Sketch of Edgemont Showing the Approximate Locatfons of Anomalies
Found During the 1971-72 and 1978 Surveys and Gamma Radiation Measurements
47
-------
Key:
PIC Measurement
'71 72 Amimalv
• '78 Anomaly
Mill SITE
Figure B. Edgemont
48
-------
APPENDIX C
Sketch of Dudley Showing the Approximate Location of Anomalies
Found During the 1971-72 and 1978 Surveys and Gamma Radiation Measurements
49
-------
Key:
Measurement (uR/hr)
• '71 -'72 Anomaly
• '78 Anomaly
^ Delta Measurement
Figure C. Dudley
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
1. REPORT NO.
ORP-LV-80-2
2.
4. TITLE ANDSUSTITLE
Above Ground Gamma Ray Logging of Edgemont, South
Dakota and Vicinity
7. AUTHOR(S)
J.E. Thrall, Vonni Kallemeyn, J.M. Hans, Jr.
9. PERFORMfNG ORGANIZATION NAME.AND ADDRESS
Office of Radiation Programs - Las Vegas Facility
U.S. Environmental Protection Agency
P.O. Box 184T6
Las Vegas, Nevada 89114
12. SPONSORING AGENCY NAME AND ADDRESS
Same as above
-
[15. SUPPLEMENTARY NOTES
>6. ABSTRACT
At the request of the U
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
February 1980
6, PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO. ' " —
A1BF2K
11. CONTRACT/GRANT NO.
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
S. Nuclear Regulatory Commission, the town of Edgemont,
<.iiv.»o>/Art in iQ7fl +r\ Hot ermine if uranium mill tailinos
from the former Edgemont Uranium Mill had been used for off-site construction or other
purposes since a similar survey conducted in 1972. Sixteen additional possible tail-
ings use locations were found during the 1978 survey.
This report summarizes the results of the 1971-72 and 1978 surveys to locate
suspected tailings use areas. It also presents and discusses other gamma measurements
made iit and around Edgemont.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b-IDENTIFIERS/OFEN ENDED TERMS
c. COSATI Field/Group
Radioactive Wastes
Environmental Surveys
Uranium mill tailings
use
1807
0510
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
50
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220— I (Rf.4—77) PREVIOUS EDITION is OBSOLETE
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