Report No. EPA 600/R-94/117
Date: July 1994
RESIDUAL SOIL RADIOACTIVITY AT THE GNOME TEST SITE
IN EDDY COUNTY, NEW MEXICO
S.H.Faller
Environmental Protection Agency
P.O. Box 93478
Las Vegas, Nevada 89193-3478
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NV 89193-3478
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NOTICE
The information in this document has been funded wholly or in pan by the United States Environ-
mental Protection Agency through Interagency Agreement DE-A108-91 NY 10963 from the United States
Department of Energy. It has been subject to the Agency's peer and administrative review, and it has been
approved for publication as an EPA document. Mention of trade names or commercial products docs not
constitute endorsement or recommendation for use.
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Contents
Page
Notice ii
Abstract iv
Acknowledgements v
Introduction 1
Surface Contamination and Remediation 2
Experimental Procedure 4
Experimental Results 4
Discussion 7
Summary 9
References 10
Figures
Page
Figure 1. Location of the Gnome Test Site in Eddy County, New Mexico 1
Figure 2. Gnome Site survey locations, shaft sites, and operating wells.
Locations 16 through 22 are not shown 3
Tables
Page
Table 1. Dose rate inventories at Gnome survey locations 5
Table 2. Spectrometry results at Gnome on-site and off-site locations; calculated
distribution parameter, 137Cs content, and minimum detectable activity 6
in
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ABSTRACT
A surface soil characterization was conducted at the Gnome Test Site surrounding areas near
Carlsbad, New Mexico to determine the abundances of gamma-emitting radionuclides and total expo-
sure rates. 137Cs was the only man-made nuclide detected in measurements taken at 22 on-site and
off-site locations, with a maximum concentration of 11.49 ± 0.13 kBq rrva(31.02 ± 0.35 pCi cm2).
Extended 137Cs verticle distributions and lower than expected inventories at undisturbed sites can be
attributed to the unconsolidated sandy surface of the area. Results of the in-situ sped ro me try indicate
that at all locations the dose rate due to <137Cs is small compared to that of the naturally occurring back-
ground.
IV
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ACKNOWLEDGEMENTS
The author would like to thank Brian Moore (or the strontium analyses and Don James and Max
Davis for assistance in collecting field data.
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VI
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INTRODUCTION
The Gnome Test Site is located in Eddy
County, southeastern New Mexico, approxi-
mately 35 km southeast of the city of Carlsbad
and 12 km southwest of the Department of
Energy (DOE) Waste Isolation Pilot Project
(WIPP) facility (Fig. 1). Project Gnome was a
3.1 kiloton yield nuclear detonation conducted
on 10 December, 1961, as part of the
Plowshare Program of the Atomic Energy
Commission. The program was initiated in
1957 to investigate the feasibility of the use of
nuclear explosives for nonmilitary applications
such as large-scale civil engineering projects
and scientific studies. The Gnome experiment
was specifically designed to explore the possi-
bility of converting the energy of a nuclear
explosion to electric power, investigate the
production and recovery of radioactive iso-
topes, collect data on the characteristics of
nuclear detonations within a salt medium, and
to obtain neutron cross-section measurements
over a wide energy range. It was the first of
the Plowshare experiments and the first under-
ground nuclear test conducted outside of the
Nevada Test Site in the United States (U.S.
AEC 1961; Nathans 1965; U.S. DOE 1982).
The nuclear device was detonated 370 m
below the surface of the Gnome site in the
Sal ado geological formation, which is com-
posed primarily of halite (NaCl) (Gardner and
Sigalove 1970). Access to the shotpoint was
provided by a horizontal drift tunnel that led to
a vertical shaft 340 m southwest of ground
zero. The explosion created a cavity about 21
m in height and 46 m in diameter (Gard 1968).
By June of 1962, mine-back activities had con-
nected the shaft to the cavity, allowing it to be.
entered. A blanket of collapsed material from
the upper hemisphere of the chamber provided
shielding from the highly radioactive melt pro-
duced in the explosion.
Figure 1. Location of the Gnome Test Site In Eddy County, New Mexico.
1
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SURFACE CONTAMINATION AND
REMEDIATION
Immediately following the firing of the
device, a low pressure vent from the Gnome
shaft occurred owing to the failure of a rupture
disk in a blast door in the access tunnel. For
more than a day, steam and short-lived
radioactive gases vented from the shaft and
were carried in a northwest direction from the
site (Fig. 2). After the event, a considerable
amount of contamination was present on the
surface of the site (Gardner and Sigalove
1970). Later reentry mining and core sam-
pling operations also brought contaminated
material to the surface, mostly in the form of
salt muck.
From 1968 to 1969, a cleanup program
was conducted at the site, with guidelines
specifying the removal of all radioactive mate-
rial with a reading of 2.6 x 10'8 C kg'1 h'1 (0.1
mR h"1, beta plus gamma) as measured with a
30 mg cm"2 window Geiger Muller survey
probe. Contaminated soil and debris were dis-
posed into the Gnome shaft and drift tunnels or
were interred beneath uncontaminated soil. In
addition, all surface facilities were removed
and all bore holes were plugged except for
those retained for hydrological monitoring
(U.S. AEG 1973). In 1977, a second more
extensive cleanup program was initiated with
guidelines for removal of soil with beta-
gamma activity above 0.74 Bq g'1 (20 pCi g'1)
or a moisture 3H activity above 1.1 kBq ml'1
(30 nCi ml'1). This operation included the
removal of debris from the contaminated waste
dump and salvage yard (Fig. 2) that had been
exposed by weathering, and the disposal of
contaminated soils and approximately 3 x 10*7
kg of salt muck into the Gnome cavity. The
Coach shaft denoted on the figure was con-
structed for a second Plowshare detonation
that was later abandoned. It was also used for
disposal of contaminated materials, and
because the Gnome and Coach shafts were
connected by a horizontal drift tunnel, the
associated well LRL-7 was used for water
monitoring and recovery during the operation.
Once the cavity had been filled to near capaci-
ty, remaining radioactive materials were
removed to the Nevada Test Site for burial in a
low-level waste site. The operation concluded
in 1979, and the site has since been decom-
missioned (U.S. DOE 1981, 1982).
In 1991, a study was undertaken to deter-
mine in-situ gamma-ray exposure rates and
radionuclide concentrations in surface soils at
nuclear test locations outside of the Nevada
Test Site (Faller 1992). In June of 1992, the
Gnome site was selected for a surface charac-
terization that would coincide with the annual
hydrological testing of the area (U.S. EPA
1992). This study was conducted to assess the
extent of remaining activity at the site and pro-
vide data on the distribution of the contamina-
tion in the desert environment.
Survey sites were selected from locations
of previous operational facilities such as waste
disposal sites, building foundations, and shaft
sites. In addition, radiological survey maps
from previous surveillance reports were used
to determine contaminated locations and areas
with background levels of radiation (U.S. DOE
1981).
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To Highway 128
Salvage Yard
Evaporation
Pond
X
GNOME
SHAFT
(plugged)
Survey Location
Well
Contaminated
Waste Dump
Ground Zen
(DD-1)
Decontamination Pad
"Salt Muck Pile Site
COACH SHAFT
(plugged)
Scale in Meters
LRL-7
gure 2. Gnome Site survey locations, shaft sites, and operating wells. Locations 16 through 22 are not shown.
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EXPERIMENTAL PROCEDURE
Field gamma-ray spectra were collected
with a high-purity germanium detector
(HpGe) with a relative efficiency of 30%. The
spectra were collected for periods of 45 min
with a portable battery-powered multichannel
analyzer and recorded on diskettes for later
retrieval and analysis with a laboratory mini-
computer. Soil core samples were collected
as described in Beck (1979) and Miller et al.
(1980). Conversion factors to determine dose
rates in air and soil activities were obtained
from Beck (1980), Murith et al. (1986), and
Heifer and Miller (1988). Total gamma-ray
flux was measured at each survey site with a
pressurized ion chamber (PIC) for periods of
15 min. All measurements were taken at a
height of 1 m above ground level.
Calibrations of radiation detection equipment
were performed with radioactive sources
traceable to the National Institute of Standards
and Technology (NIST). In a period of 6 d, a
total of 22 on-site and off-site locations were
surveyed, with core samples taken at 11 loca-
tions. Soil samples were packaged and
returned to the laboratory for gamma-ray
analysis as in Faller (1992). Two soil samples
were analyzed for radiostrontium content by
total dissolution, ion-exchange separation,
and beta-ray analysis.
EXPERIMENTAL RESULTS
Fig. 2 depicts the Gnome Test Site and the
approximate path of the plume from the shaft
vent. On-site and near-site in-situ survey
locations and the positions of facilities that
were removed during clean up operations are
also shown. On-site wells are sampled and
analyzed yearly.
Table 1 lists the gamma-ray dose rates in
air measured at each of the survey locations.
The combined total rates are the summed con-
tributions from the cosmic-ray component,
deduced from the barometric pressure, and the
natural and man-made components, derived
from analysis of the HpGe spectra. Gross
dose rates from PIC measurements, taken at
the same survey locations as the gamma-ray
spectra, are given as a check of the summed
rates.
Table 2 lists the 137Cs inventories for each
surveyed site. The depth distribution parame-
ter is expressed as o/p, where a is the recip-
rocal of the relaxation length of the assumed
exponential profile in the soil, and p is the soil
density (Miller and Heifer 1985). At locations
where soil cores were not taken, parameters of
oo (planar distribution) and 0.05 are given to
represent a large range in distribution profiles.
Corresponding radiocesium abundances per
unit area deduced from the depth parameters
and the spectral results are listed for each sur-
vey site. The minimum detectable concentra-
tions per unit area are also given. n7Cs was
the only man-made gamma-emitting nuclide
detected in this study.
The one-sigma statistical uncertainties of
the nuclide inventories in Table 2 are general-
ly less than 20% of the calculated values, and
in some cases, as little as 1%. Uncertainties
are as high as 50% for 7Be values, owing to
the small concentrations. Uncertainties intro-
duced by literature conversion factors used to
determine individual nuclide concentrations
are generally less than 15% (Heifer and Miller
1988). In addition, uncertainties of less than
6% exist in the PIC dose rate in air values, and
some relatively small errors exist in estima-
tions of vertical distributions where they were
determined (Faller 1992).
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Table 1. Dose rate Inventories at Gnome survey locations (LOnGy tr'= 0.11 nRh').
Dose rate in air (nGy h ')
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
ON SITE
Surface ground zero (5 m northeast of monument)
Coach shaft site (well LRL-7) .
70 m northeast of Coach shaft she
130 m northeast of Coach shaft site
Waste tank/evaporation pond site
West side of salt muck pile site
East side of sail muck pile she
Gnome shaft (8 m northeast of plug)
Southeast side of contaminated waste dump
Central area of contaminated waste dump
Salvage yard
Decontamination pad
OFF SITE
Weis USGS 4 and 8
150 m northwest of Gnome shaft
400 m northwest of Gnome shaft
2.5 km northwest of Gnome shaft
10 km northwest of Gnome shaft
16 km northwest of Gnome shaft
2.5 km west of surface ground zero
3 km east of surface ground zero
4 km northeast of surface ground zero
3 km south of surface ground zero
Cosmic
45
45
45
45
45
45
45
45
45
45
45
45
45
44
44
45
45
45
45
44
44
44
«K
7.8
6.7
5.6
7.7
7.2
10.7
10.6
8.4
4.3
8.0
9.8
9.0
11.5
11.4
11.4
13.0
9.2
. 13.8
10.3
8.4
10.1
8.4
^Th'
8.4
6.7
5.3
6.8
7.7
10.5
8.5
6.6
4.8
5.9
10.6
7.3
8.8
10.2
10.4
13.4
11.2
12.9
7.0
6.8
9.0
6.5
"IP
11.1
15.8
10.9
6.3
6.5
9.7
10.4
9.4
7.0
7.7
8.9
7.5
9.0
9.1
9.7
10.6
10.8
8.9
9.0
7.5
7.6
6.3
'Be
0.6
0.4
0.3
0.4
0.3
0.1
02
0.4
0.4
0.3
0.3
0.3
0.5
0.3
0.3
0.3
0.4
0.5
0.4
0.3
0.3
0.3
wCs
4.3"
2.4"
0.3"
0.3"
0.4"
0.1b
1.0"
4.4"
0.8"
5.8
0.1"
4.1
3.3"
9.8
4.1
0.4
1.4
0.8
0.4
0.5
0.5
0.3
Total
77
77
67
67
67
76
76
74
62
73
75
73
78
85
80
83
78
82
72
68
72
59
PIC
75
70
68
67
69
73
72
73
63
75
70
73
79
83
76
76
67
77
70
68
80
65
• Contribution from series.
6 Assuming alp •> 0.05 (no core taken).
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Tiblt 2. Spectromotry results at Gnome on-site and off-site locations; calculated distribution parameter, '"Cs content, and mini-
mum detectable activity (1.0 kBq nr* = 2.7 pCI cm •*).
II7Cs Distrtoution
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
ON SITE
Surface ground zero (5 m northeast at monument)
Coach shaft site (well LRL-7)
70 m northeast of Coach shaft site
130 m northeast of Coach shaft she
Waste tank/evaporation pond she
West side of salt muck pile site
East side of salt muck pile site
Gnome shaft (8 m northeast of plug)
Southeast side of contaminated waste dump
Central area of contaminated waste dump
Salvage yard
Decontamination pad
OFF SITE
Wetts USGS 4 and 8
150 m northeast of Gnome shaft
400 m northwest of Gnome shaft
2.5 km northwest of Gnome shaft
10 km northwest of Gnome shaft
16 km northwest of Gnome shaft
2.5 km west of surface ground zero
3 km east of surface ground zero
4 km northeast of surface ground zero
3 km south of surface ground zero
o/p
oo
0.05
OO
0.05
OO
0.05
OO
0.05
OO
0.05
OO
0.05
OO
0.05
OO
0.05
OO
0.05
0.14
OO
0.05
0.04
OO
0.05
0.14
0.25
0.11
0.54
0.26
0.09
0.17
0.13
0.10
Activity abundance
(kBq m-2)
1.42
9.51
0.80
5.38
0.096
0.63
0.10
0.66
0.14
0.91
0.033
0.22
0.32
3.26
1.45
9.78
028
1.85
6.77
0.044
0.30
9.96
1.07
7.16
11.49
3.71
0.50
1.00
0.69
0.65
0.53
0.56
0.42
i
±
±
±
±
±
±
±
+
±
±
+
±
±
±
±
±
±
+
±
±
±
±
±
±
±
±
+
+
±
±
±
±
0.03
0.17
0.02
0.14
0.009
0.06
0.01
0.06
0.01
0.07
0.008
0.06
0.02
0.15
0.03
0.17
0.01
0.08
0.10
0.008
0.05
0.18
0.03
0.18
0.13
0.08
0.05
0.03
0.04
0.05
0.04
0.04
0.04
MDA
0.05
0.34
0.04
025
0.03
0.16
0.02
0.15
0.02
0.16
0.01
0.16
0.03
0.26
0.03
0.19
0.02
0.16
0.10
0.03
0.17
022
0.03
0.19
0.12
0.07
0.11
0.04
0.07
0.10
0.07
0.09
0.08
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DISCUSSION
The summed totals of the dose rates from
cosmic radiation and radionuclides at all sur-
veyed locations are in close agreement with
the measured PIC rates at the same sites. The
average PIC value in this study is 2.0% lower
than the average summed value, and differ-
ences in the two values at each location are
within the estimated uncertainties.
A large variability in 137Cs activity is evi-
dent across the Gnome site (locations 1
through 12). However, at all of the on-site
locations and other survey sites close to the
Gnome shaft, the range of 137Cs values should
be considered only an estimate because the
ground has been disturbed several times since
the original contamination, and it is unlikely
that the radiocesium has an exponentially
decreasing vertical distribution, as assumed in
the calculation of the inventories and dose
rates. Also, at locations 9 and 10, it is quite
possible that the observed 137Cs activity is due
to contaminated materials buried within the
waste dump.
It was suspected that the relatively high
cesium activity at the surface ground zero, sur-
vey location 1, may have been caused by over-
flow or spillage from well DD-1 which is used
to monitor the water within the Gnome cavity.
A surface soil sample was taken next to the
wellhead and returned to the laboratory for
radiochemical analysis. The ratio of ^Sr to
137Cs in soil was found to be 0.029 ± 0.010,
while the ratio in water obtained from well
DD-1 was 0.24 ± 0.05 (U.S. EPA 1979). The
large difference implies that the source of the
soil contamination was not the well water, and
was probably the post detonation venting and
drilling operations. Ratios of ^Sr to 137Cs
determined for many soil samples at the site
prior to the cleanup program of 1977 were also
generally very small (U.S DOE 1978).
Survey location 13 is located between two
U.S. Geological Survey wells used for a tracer
experiment in 1963 (Beetem 1964). The
experiment was designed to determine physi-
cal characteristics of dispersion and chemical
absorption reactions of radionuclides in the:
Culebra Dolomite Aquifer, which is consid-
ered to be the only significant aquifer at the
Gnome site (Gardner and Sigalove 1970). The
nuclides were injected into well USGS 8 and
recovered from USGS 4 for analysis and rein-
jection. Nuclides ml, 3H, ^Sr, and 137Cs in a
range of 0.4 to 1.8 TBq (10-50 Ci) were intro-
duced during the course of the experiment
(U.S. DOE 1982), and the latter three nuclides
are presently detected in the waters of both
wells. A laboratory analysis of a surface soil
sample taken near USGS 8 showed a ^Sr to
137Cs activity ratio of 0.11 ± 0.03 while the
water of USGS 8 had a ratio of 0.74 ± 0.11,
again indicating that the activity is probably
not due to well water spillage.
Survey sites 14 through 18 were selected
for a cursory investigation of remaining fallout
from the Gnome vent. The sites lie within the
general path of the fallout plume (Fig. 2) at
varying distances from the Gnome shaft. Of
all locations surveyed in this study, site 14
which lies 150 m from the shaft, showed the
highest 137Cs inventory. This is not unexpect-
ed because in aerial surveys flown before and
after the 1977 to 1979 decontamination opera-
tion, the region immediately northwest of the
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Gnome shaft was found to have the most
extensive 137Cs contamination (U.S. DOE
1981). The final survey showed a small area at
the same location as survey site 14 that had a
137Cs count rate equivalent to an exposure rate
of 25 to 28 nGy h'1 (2.8 to 3.3 pR h'1) at a
height of 1 m. In Table 1, it is evident that the
dose rate from 137Cs measured in this study is
about one third of that value, or approximately
equal to the contribution from the 232Th series.
Survey sites 14, 15, and 17 all show ele-
vated 137Cs abundances. Site 16 is an area that
appeared to be frequently drained, and is not
likely to have the same retention characteris-
tics as the other locations. In all, it would be
difficult to draw conclusions about the extent
of remaining fallout activity without a thor-
ough investigation. Decay and weathering in
the elapsed 31 y would have altered the origi-
nal distribution, and the plume itself which
was released for several hours would certainly
not have left a simple contoured pattern of fis-
sion products.
Sites 19 through 22 were selected for off-
site control measurements because of their dis-
tance from the Gnome site and because they do
not lie in the recorded path of the plume. The
sites have similar abundances and extended
vertical distributions of I37Cs. The activities
are somewhat low considering the average 30
cm of rainfall the area receives (Gardner and
Sigalove 1970; Miller et al. 1980; Arnalds et
al. 1989). The surface of the region around the
Gnome site consists primarily of alluvial mate-
rial and quartz sand (Mackallor 1965), and in
the immediate vicinity consists of caliche out-
croppings, sand, and sand dunes sparsely cov-
ered with desert vegetation. Poor water reten-
tion characteristics likely account for the low
137Cs fallout activity and the deep dispersion
relative to other arid regions in North America.
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SUMMARY
The dose rates deduced from in-situ spec-
trometry and soil core analysis are in close
agreement with the measured PIC rates at all
surveyed locations. As in previous surveys,
137Cs abundances were found to be highly vari-
able in the Gnome area, with the highest con-
centration lying 150 m northwest of the
Gnome shaft site. Presumably this activity
was deposited from the low-pressure venting
that occurred immediately after the detonation,
and it currently accounts for a dose rate about
equal to the contribution from the naturally
occurring M2Th series, or about one-eighth of
the total dose rate measured at that location.
Considering the time elapsed since the ear-
lier surveys, radiocesium concentrations at
contaminated locations detected in this study
were lower than expected. Also, surveys con-
ducted at surrounding control areas away from
the path of the vent plume show low 137Cs
abundances relative to other regions that
receive less or equal rainfall. Both discrepan-
cies are probably due to the predominance of
an unconsolidated sandy surface with poor
water retention characteristics.
-------
REFERENCES
Amalds, O.; Cutshalls, N.H.; Neilsen, G.A. Cesium-137 in Montana Soils. Health Phys.
57:955-958; 1989.
Beck, H.L. The natural radiation background of Utah-Preliminary report on radionuclides in
soils in populated areas. New York: U.S. Department of Energy, Environmental
Measurements Laboratory; Report No. EML-362;1979.
Beck, H.L. Exposure rate conversion factors for radionuclides deposited on the ground. New
York: U.S. Department of Energy, Environmental Measurements Laboratory; Report No.
EML-378; 1980.
Beetem, W.A.; Angelo, C.G. Carlsbad hydrology-2, tracer study at Project Gnome site, near
Carlsbad, New Mexico - background information. U.S. Geological Survey Technical Letter;
1964.
Faller, S.H. In-situ gamma-ray site characterization of the Tatum Salt Dome Test Site in Lamar
County, Mississippi. Health Phys. 62:571-575; 1992.
Gard, L.M., Jr. Geologic studies, Project Gnome area, Eddy County, New Mexico. Denver,
CO: U.S. Geological Survey; Professional Paper 589; 1968.
Gardner, M.C.; Sigalove, J.J. Evaluation of the Project Gnome/Coach Site, Carlsbad, New
Mexico, for disposition, including identification of restrictions. Las Vegas, NY: U.S.
Atomic Energy Commission; NVO-1229-106, Part I; 1970.
Heifer, I.K.; Miller, K.M. Calibration factors for Ge detectors used for field spectroscopy.
Health Phys. 55:15-29; 1988.
Mackallor, J.A. Aeroradioactivity survey and geology of the Gnome (Carlsbad) area, New
Mexico and Texas (ARMS-1). Springfield, VA: Civil Effects Test Operations, U.S. Atomic
Energy Commission; Report No. CEX-59.4.24; 1965.
Miller, K.M.; Gogalak, C.V.; Tanabe, H. Natural background radiation and 137Cs inventories in
southern Nevada. New York: U.S. Department of Energy, Environmental Measurements
Laboratory; Report No. EML-386; 1980.
Miller, K.M.; Heifer, I.K. In situ measurements of 137Cs inventory in natural terrain. In:
Proceedings of the Health Physics Society midyear topical symposium. Colorado Springs,
CO: Central Rocky Mountain Chapter of the Health Physics Society; 1985:243-251.
Murith, C.; Volkle, H.; Huber, O. Radioactivity measurements in the vicinity of Swiss nuclear
power plants. Nucl. Instrum. Meth. 243:549-560; 1986.
10
-------
Nathans, M.W. U.S. Atomic Energy Commission, Plowshare Program, Project Gnome
Carlsbad, New Mexico, isotope program - final report. Las Vegas NV: U.S. Atomic Energy
Commission; Report No. PNE 102F; 1965.
/ V
U.S. Atomic Energy Commission, Project Gnome Organization. Project Gnome; Part of the
U.S. Atomic Energy Commission's Plowshare Program for peaceful uses. Albuquerque,
NM: Albuquerque Operations Office; AL Pamphlet 3100-1; 1961.
U.S. Atomic Energy Commission, Nevada Operations Office. Gnome/Coach site disposal
options. Las Vegas, NV: U.S. Atomic Energy Commission; NVO-131; 1973.
U.S. Department of Energy, Gnome Site decontamination and decommissioning project; phase I
radiological survey and operations report; Carlsbad, New Mexico. Las Vegas, NV: U.S.
Department of Energy, Nevada Operations Office; NVO/0410-48; 1978.
U.S. Department of Energy, Gnome Site decontamination and decommissioning project; radia-
tion contamination clearance report. Las Vegas, NV: U.S. Department of Energy, Nevada
Operations Office; Report No. DOE/NV/00410-59; 1981.
U.S. Department of Energy, Nevada Operations Office, Health Physics Division, Environmental
Branch. Long-term hydrologic monitoring program; Gnome Site, Eddy County, New
Mexico. Las Vegas, NV: U.S. Department of Energy, Nevada Operations Office; Report
No. NVO-241; 1982.
U.S. Environmental Protection Agency, Radiochemical analytical procedures for analysis of
environmental samples. Las Vegas, Nevada: U.S. Environmental Protection Agency; EMSL-
LV-0539-17; 1979.
U.S. Environmental Protection Agency, Nuclear Radiation Assessment Division Annual Report
1992. Las Vegas, NV; Environmental Monitoring Systems Laboratory - Las Vegas; in prepa-
ration.
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