1984-04-06 – NRC – ORAU report on berm erosion surey at the West Lake Landfill

1984-04-06-nrc-orau-report-on-berm-erosion-surey-at-the-west-lake-landfill

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Oak Ridge
Associated Post Office Box 117
Universities Oak Ridge, Tennessee 37830
Telephone (615) 576-3305
Manpower Education.
Research, and Training
Division
April 6, 1984
Mr. William Crow /
Div. of Fuel Cycle & Mat. Safety
MS-SS396, Nuclear Regulatory Commission
Washington, DC 20555
Dear Mr. Crow:
Enclosed is a copy of the report on the survey of the
berm at the West Lake Landfill in St. Louis County, Missouri.
Please let me know if you have any questions concerning
this information.
Sincerely,
James D. Berger
Program Manager
Radiological Site Assessment Program
pz>
JDB/jm
Enclosure
cc: Wyngarden, NRC {3-,.:..,.)
O’Connor, Univ. of MO
McCullough, West Lake Landfill
40249270
SUPERFUNI) RF.COKDS
8405240319 840406
PDR ADDCK 0400880J
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SURVEY FOR BERK EROSION
WEST LAKE LANDFILL
ST. LOUIS COUNTY, MISSOURI
A.J. Boerner
*. INTRODUCTION
On March 12-13, 1984, representatives from Oak Ridge Associated
Universities (ORAU), Oak Ridge, Tennessee, performed a radiological survey
along a section of the benn bounding the West Lake Landfill. The objective
of the survey was to determine if erosion of the benn was occurring,
resulting in the spread of contamination to adjacent property. Information
collected included exposure rates, concentrations of radionuclides in
surface soil, and locations of elevated contact radiation levels relative
to the surface topography.
PROCEDURES
1. A scan of the north face of the benn was performed with Nal(Tl)
scintillation detectors to determine general areas of elevated
radiation levels. The area selected for further investigation is
shown in Figure 1. The walkover scan also identified an elevated
region along a short unpaved access road situated just west of the
Shuman Building and leading to the perimeter road; however, no further
measurements or sampling were undertaken at this location.
2. A 5 m grid system was established on the benn in an area identified by
the scan.
3. A sketch of the topography in each grid block was prepared.
Work performed by the Manpower Education, Research, and Training Division
of Oak Ridge Associated Universities, Oak Ridge, TN, under interagency
agreement DOE No. 40-770-80, NRC Fin. No. A-9093-0, between the Nuclear
Regulatory Commission and the Department of Energy.
April 6, 1984
4. Surface scans were conducted over the grid using portable Nal(Tl)
scintillation detectors. Locations of elevated contact radiation
levels were noted.
5. Exposure rate measurements were made at the surface and at 1 m above
the surface at each grid line intersection and at selected locations
•• of elevated readings. A Nal(Tl) scintillation meter calibrated with a
pressurized ionization chamber was used.
6. Surface (0-15 cm) soil samples were collected at twelve grid line
intersections and at five locations of elevated surface contact
radiation levels identified by the scan (refer to Figure 2). Two
additional samples were collected from the adjacent field.
7. Exposure rates were also measured at several locations near the
Landfill office building and a soil sample collected from an area of
elevated contact readings.
8. Soil samples were analyzed by gamma spectrometry. Radium-226 and
Th-230 were the major radionuclides of concern, although spectra were
reviewed for Pa-231 and Ac-227. One soil sample from the berm area
and the sample from near the office building were analyzed by neutron
activation to determine trace element composition.
RESULTS AND DISCUSSION
Topography
Figure 2 is a sketch of the berm area surveyed, indicating the grid
system and the major surface features. The slope of the berm is estimated
to be approximately 40°. The soil on the face of the berm appears quite
loose and only sparsely vegetated. There are several small ditches which
follow the slope; these suggest erosion or slippage of the surface soil
layer. Several small mounds of earth were also noted at the base of the
berm.
Direct Radiation Levels
The walkover scan identified levels ranging up to 600 uR/h near the
top of the berm. Levels were generally highest in a region near grid
coordinates C2 and C3 and in a ditch down-slope from these coordinates.
Contact exposure rates at C2 and C3 were 360 yR/h and 570 pR/h,
respectively. Elevated measurements (up to 280 pR/h) were also noted on
contact with a mound of soil between grid coordinates D4 and D5 at the base
of the berm. Specific “hot spots” were not present along the perimeter
road or the adjacent field; however, ambient radiation levels were
generally elevated – possibly the result of residues in the landfill berm.
Figure 3 indicates the contact exposure rates measured on the berm.
An area near the landfill office had been identified by a previous
survey as containing contaminated residues and having an elevated direct
radiation level.* Random measurements in that area (see Figure 4) indicate
exposure rates at 1 m above the surface ranging up to 45 yR/h. The maximum
level is near a small drainage ditch. The extent of the area exceeding
20 pR/h is smaller than that shown in the Radiation Management Corporation
report. This is probably the result of additional fill (1-1.5 m) which has
been placed on portions of this area, since the previous survey.
Radionuclide Concentrations in Soil
Radionuclide concentrations in surface soil samples are presented in
Table 1. With one exception, i.e. the sample from coordinate A5, these
samples all contained elevated levels of Ra-226 and/or Th-230. Ratios of
Th-230 to Ra-226 were in the range of approximately 25:1 to 40:1. Pa-231
and Ac-227 were also present in most of these samples. The maximum
concentrations of Ra-226 were 699 pCi/g and 662 pCi/g. These were in
samples S4 and S5 from areas having the highest direct radiation levels.
* L.F. Booth, et al., Radiological Survey of the West Lake Landfill.
St. Louis County. Missouri. Radiological Management Corporation,
May 1982.
Highest Th-230 concentrations were also noted in these two samples. A
sample (S7) from the mound of soil at the base of the berm contained
185 pCi/g of Ra-226 and 6720 pCi/g of Th-230.
Samples from grid line 5 along the base of the berm and from grid
line 6 along the perimeter road also had elevated radionuclide
concentrations; however they were lower than the concentrations in samples
from areas of elevated direct radiation. Samples B5, C5, and D5 were the
highest; these locations are downslope from the areas of highest residues
and in the vicinity of ditches and mounds of eroded soil. The two samples
(SI and S2) collected in the adjacent field, about 10 meters north of grid
coordinates B6 and D6, also contain elevated Ra-226 and Th-230
concentrations.
Sample S8 from the ditch near the office area contained 5.19 pCi/g of
Ra-226 and 344 pCi/g of Th-230. Neutron activation results for this sample
and the sample from coordinate E,6 indicate similar trace element contents.
Based on the Ra-226 to Th-230 ratios and other elemental contents it
appears that the residues are from the same source.
SUMMARY
A survey of a small area at the West Lake Landfill in St. Louis
County, Missouri, was conducted by ORAU to determine if erosion of the
landfill berm is resulting in spread of radioactive residues buried on this
site. Measurements of direct radiation levels and radionuclide
concentrations in soil and the physical condition of the berm area indicate
that erosion is occurring and that there are elevated concentrations of
Ra-226 and Th-230 at the base of the berm and extending into the adjacent
field.
Measurements performed at another area of known radioactive residue
burials, near the office building, indicate that there has been 1-1.5 m of
additional fill added to portions of this area during the past 3-4 years.
This added fill hs reduced the direct surface radiation levels at some
locations by approximately a factor of 2. Analyses suggest that the
residues from the berm and office areas are from the same source.
TABLE 1
RADIONUCLIDE CONCENTRATIONS IN SURFACE SOIL
Radionuclide Concentrations (pCi/g)
Location3
A5
B5
C5
D5
E5
F5
A6
B6
C6
D6
E6
F6
SI
S2
S3
S4
S5
S6
S7
S8 (near office
building)
Ra-226
1.05 +
11.3 +
6.77 +
23.2 +
1.35 +
1.32 +
2.36 +
3.98 +
3.93 +
2.84 +
5.15 +
0.98 ±
4.27 ±
4.49 +
38.3 +
662 +
699 +
72.3 +
185 ±
5.19 ±
0.30b
0.7
0.53
1.1
0.19
0.20
0.37
0.51
0.51
0.51
0.51
0.17
0.44
0.61
1.6
7
6
2.3
3
0.59
404
241
1006
13.
8.
99.
132
142
109
181
11.
132
178
1601
16170
19130
3280
6720
344
Th-230
<7.67 + 45 + 21 + 140 0 + 5.7 49 + 5.3 3 + 35.5 + 75 + 70 + 70 + 57 1 + 5.1 + 17 + 82 + 240 + 810 + 220 + 290 ± 480 ± 84 Pa-231 <0.59 <1.16 <0.89 7.54 + 3.07 <0.68 8 <0.57 <0.86 <0.81 <1.03 <0.98 <0.77 <0.71 <0.76 <1.22 7.16 + 3.47 140 ± 13 <10.1 18.3 + 5.1 34.9 ± 7.3 <1.70 Ac-227 <0.50 3.79 + 1.00 1.03 + 0.75 11.0 + 1.6 0.50 + 0.49 0.15 + 0.33 <0.46 2.82 ± 0.84 2.35 + 0.88 2.65 + 0.56 1.37 + 0.48 <0.59 <0.57 <0.23 5.78 + 2.23 207 +11 29.1 + 8.3 11.1 + 4.4 49.8 ± 5.0 2.44 j+ 0.86 a Refer to Figure 2. b Errors are 2a based on counting statistics. o o o o o o o o o o o o o q o o o • < a u O w u . O X - - > – –
FIGURE 1. Portion of North Edge of Landfill Indicating Survey Area.
B
F I E L D
N W
METERS
FIGURE 2. Map of Berm Area Indicating Berm Features, the Grid
System, and Soil Sampling Locations.
B
FIELD
N W
METERS
FIGURE 3. Areas of Elevated Contact Radiation Levels.
N
FIGURE A. Area Near Office Building Showing Region Exceeding 20 yR/h at
1 m Above the Surface and Soil Sampling Location.