SITE CHARACTERIZATION AND
REMEDIAL ACTION CONCEPTS FOR
THE WEST LAKE LANDFILL
Docket No. 40-6801
Manuscript Completed: July 1969
Date Published: July 1969
Office of Nuclear Material Safety and Safeguards
_ U.S. Nuclear Regulatory Commission
• Washington, DC 20555
This report has as its basis a characterization of the West Lake Landfill site
and evaluation of some potential remedial measures performed primarily by
S. K. Banerji, W. H. Miller, J. T. O’Connor and L. S. Uhazy of the University
of Missouri-Columbia. The Nuclear Regulatory Commission received the first
and second drafts, then titled “Engineering Evaluation of Options for Disposition
of Radioactively Contaminated Residues Presently in the West Lake Landfill, St.
Louis County, Missouri,” in 1984; thus most of the information in this report
dates from 1983-1984. However, some more recent data, principally water sampling
results, have been added. Waste disposal and other industrial activities have
continued on the 200 acre site, as have activities in the vicinity, resulting
in changes in details of topography, roads, etc. To provide a more complete
view of the radioactive material in the landfill, use has been made of figures
from the report titled “Radiological Survey of the West Lake Landfill, St. Louis
County, Missouri,” NUREG/CR-2722, May 1982.
The remedial action concepts in this report are those proposed by the contractor.
Judgments expressed in this report about these concepts are in general those of
the contractor, and do not necessarily represent the views of the Nuclear Regulatory
Commission. For example, the cost estimates for these concepts are
based on radium-226 concentrations whereas the long-term issue is dependent
upon the thorium-230 concentrations.
Although some of its information has not been updated since 1984, this report is
being released so as to make its collected information available to interested
The West Lake Landfill is near the city of St. Louis in Bridgeton, St. Louis
County, Missouri. In addition to municipal refuse, industrial wastes and demolition
debris, about 43,000 tons of soil contaminated with uranium and its radioactive
decay products were placed there in 1973. After learning of the radioactive
material in the landfill, the U.S. Nuclear Regulatory Commission (fJRC) had
a survey of the site’s radioactivity performed and, *n 1983, contracted, through
Oak Ridge Associated Universities (ORAU), with the University of Missouri-
Columbia (UMC) to characterize the environment of the site, conduct an engineering
evaluation, and propose remedial measures. This report presents a description
of the results of the UMC work, providing the environmental characteristics
of the site, the extent and characteristics of the radioactive material there,
some considerations with regard to potential disposal of the material, and some
concepts for remedial measures.
PREFACE i i i
1 INTRODUCTION 1-1
2 SITE DESCRIPTION :’• 2-1
2.1 Location 2-1
2.2 Zoning 2-1
2.3 History 2-2
2.4 Ownership 2-2
2.5 Contaminated Areas 2-2
2.6 Topography 2-3
2.7 Geology 2-3
2.8 Hydrology 2-6
2.9 Meteorology 2-10
2.10 Ecology 2-11
2.11 Demographics 2-14
3 RADIOLOGICAL CHARACTERIZATION OF THE SITE ‘3-1
3.1 Radiological Surveillance 3-1
3.2 Survey Results 3-2
3.3 Estimation of Radioactivity Inventory 3-7
4 APPLICABILITY OF THE BRANCH TECHNICAL POSITION 4-1
5 REMEDIAL ACTION ALTERNATIVE CONSIDERATIONS 5-1
5.1 Option A: No Remedial Action 5-1
5.2 Option B: Stabilization on Site With Restricted
Land Use 5-2
5.3 Option C: Extending the Landfill Off Site 5-4
5.4 Option D: Removing Radioactive Soil and Relocating
5.5 Option E: Excavation and Temporary Onsite Storage in
a Trench 5-6
5.6 Option F: Construction of a Slurry Wall to Prevent
Offsite Leachate Migration 5-8
6 REFERENCES 6-1
1.1 Location of West Lake Landfill 1-2
2.1 Land use around West Lake Landfill site 2-16
2.2 Zoning plan of West Lake area (June 1984) 2-17
2.3 Site topography and extent of contamination 2-18
2.4 Bedrock stratigraphy 2-19
2.5. Location of monitoring wells 2-20
2.6 Soil profile of river alluvium 2-21
2.7 Cross-section of Missouri River alluvial valley 2-22
2.8 Soil profile of upland loessal soil 2-23
2.9 Surface hydrology of West Lake area 2-24
2.10 Average monthly precipitation at Lambert Field
International Airport 2-25
2.11 Wind distribution for West Lake area 2-26
3.1 External gamma radiation levels (November 1980) 3-9
3.2 Location of surface soil samples, Area 1 3-10
3.3 Location of surface soil samples, Area 2 3-11
3.4 Location of auger holes, Area 1 3-12
3.5 Location of auger holes, Area 2 3-13
3.6 Auger hole elevations and location of contamination
within each hole m3-14
3.7 Cross-section B-B showing subsurface deposits in
Area 1 3-15
3.8 Cross-section E-E showing subsurface deposits in
Area 2 3-16
3.9 Rn-222 flux measurements at three locations in Area 2
3.1 RMC radionuclide analyses of water samples from the
West Lake site taken by MDNR in 1981 3-18
3.2 Radiological quality of water in perimeter monitoring
wells of West Lake Landfill (concentrations reported
in pCi/1) 3-20
3.3 Radionuclide concentrations in well water samples:
May 7-8, 1986 3-21
3.4 Radionuclide concentrations in Latty Avenue composite
4.1 Summary of maximum soil concentrations permitted under
disposal options 4-2
5.1 Itemized cost of remedial action, Option B 5-10
5.2 Itemized cost of remedial action, Option C 5-11
5.3 Itemized cost of remedial action, Option D 5-12
5.4 Itemized cost of remedial action, Option E 5-13
• 5.5 Itemized cost of remedial action, Option F 5-14
In 1973, approximately 7900 metric tons (mt) (8700 short tons) of radioactively
contaminated barium sulfate (BaS04) residues were mixed with about 35,000 mt
(39,000 t) of soil, and the entire volume was placed in the West Lake Landfill
in St. Louis County, Missouri. This material resulted from decontamination
efforts at the Cotter Corporation’s Latty Avenue plant where the material had
been stored. Disposal in the West Lake Landfill was not authorized by the
Nuclear Regulatory Commission (NRC) and was contrary to the disposal location
indicated in the NRC records. State officials were not notified of this disposal
since the landfill was not regulated by the State at the time. Although
the contamination does not present an immediate health hazard, authorities have
been concerned about whether this material poses a long-term health hazard to
workers and residents of the area and what, if any, remedial action is necessary.
In 1980-81, Radiation Management Corporation (RMC) of Chicago, Illinois,
performed a detailed radiological survey of the West Lake Landfill under contract
to the NRC (NUREG/CR-2722). This survey was performed to determine the
extent of radiological contamination.. Before this survey, little was known
about the location or activity of radionuclide-bearing soils in the landfill.
This survey showed that the radioactive contaminants are in two areas. The
northern area (Area 2) covers about 13 acres. The radioactive debris forms a
layer 2 to 15 feet thick, exposed in only a small area on the landfill surface
and along the berm on the northwest face of the landfill. The southern area
(Area 1) contains a relatively minor fraction of the debris covering approximately
3 acres with most of the contaminated soil buried with about 3 feet of
clean soil and sanitary fill.
The RMC survey showed that the radioactivity is from the naturally occurring
U-238 and U-235 series with Th-230 and Ra-226 as the radionuclides that dominate
radiological impact. The survey data indicate that the average Ra-226 concentration
in the radioactive wastes is about 90 pCi per gram; the average Th-230
concentration is estimated to be about 9000 pCi per gram. Since Ra-226 has
been depleted with respect to its parent Th-230, Ra-226 activity will increase
in time (for example, over the next 200 years, Ra-226 activity will increase
ninefold over the present level). This Increase in Ra-226 must be considered
in evaluating the long-term hazard posed by this radioactive material.
In addition to RMC’s radiological survey, (oil and water samples were collected
and analyzed by others, Including Oak Ridge Associated Universities (ORAU), and
the University of Missouri-Columbia (UMC). “Occasionally a sample of water from
a monitoring well exceeds slightly the EPA drinking water standard of 15 pCi
gross alpha per liter. Sample analyses for priority pollutants (non-radioactive
hazardous substances) show a number of listed pollutants are present.
On the basis of radiological surveillance conducted by RMC, UMC, and ORAU, the
following areas of concern have been identified:
(1) Radioactive soil is eroding from the northwestern face of the berm, and is
being transported off site.
(2) Radon gas had been observed to accumulate to an unacceptable level
in the Butler-type building on site. This building has since been removed.
(3) Some degree of radiological contamination has been found in the wells
that monitor the perimeter.
(4) Surface exposure rates over much of the contaminated areas are greater
than 20 uR/hr.
In March 1983, the NRC through ORAU, contracted with UMC to conduct an
engineering evaluation of the site and propose possible remedial measures for
NRC’s consideration for dealing with the radioactive waste at the West Lake
Landfill. The following six remedial options were proposed and evaluated in
o Option A – No remedial action
o Option B – Stabilization onsite with restricted land use
o Option C – Extending the landfill offsite with restricted land use
o Option 0 – Removal and relocation of the contaminated material to an
authorized disposal site
o Option E – Excavation and temporary onsite storage in a trench
o Option F – Construction of a slurry wall to prevent leachate from
migrating off site
It is noted that some of the above alternatives for remedial action were
initially evaluated with the objective of permanent disposal of the waste at
The West Lake Landfill is located In St. Louis County, Missouri, 6 km (3.7
miles) west of Lambert Field International Airport (Figure 1.1) and southwest
of St. Charles Rock Road in Bridgeton, Missouri. The site has been used since
1962 for disposing of municipal refuse, industrial solid and liquid wastes, and
construction demolition debris. In addition, the landfill is an active industrial
complex on which concrete ingredients are measured and combined before
mixing (“batching”), and asphalt aggregate is prepared. Limestone ceased to be
quarried in the spring of 1987.
In 1973, 7900 metric tons [(mt) (8700 short tons)] of radioactively contaminated
barium sulfate (BaSD4) residues from uranium and radium processing were mixed
with an estimated 35,000 mt (39,000 tons) of soil and deposited in the West Lake
Landfill. Previously, this material was located at the Cotter .Corporation’s
Latty Avenue facility in Hazelwood, Missouri, and was removed during decontamination
work. It is not known what levels of contamination were already in
the soil before the barium sulfate residues were mixed into it. Disposal in the
West Lake Landfill was unauthorized and contrary to the disposal location
indicated in the U.S. Nuclear Regulatory Commission’s (NRC’s) records.
Subsequently> the NRC sponsored studies that were directed at determining the
radiological status of the landfill. In 1978, an aerial radiological survey
revealed two areas within the landfill where the gamma radiation levels indicated
radioactive material had been deposited. A BOre extensive survey was
initiated in November 1980 by the Radiation Management Corporation (RMC) under
contract to the NRC.
In March 1983, the NRC through Oak Ridge Associated Universities (ORAU) contracted
with the University of Missouri-Columbia Department of Civil Engineering
to describe the environmental characteristics of the site, conduct an engineering
evaluation, and propose possible remedial measures for dealing with the radioactive
waste at the West Lake Landfill. In May 1986, ORAU sampled water from
Seal* in Miles
Figure l.-l Location of West Lake Landfill
• wells on and close to the landfill to determine 1f the radioactive material had
• migrated into the groundwater.
Information from all these sources forms the basis for this report.
2 SITE DESCRIPTION
This chapter presents a historical and environmental description of the West Lake
Landfill site located in St. Louis County, Missouri.
The 81-hectare (ha) (200-acre) West. Lake Landfill property is situated between
the St. Charles Rock Road and the Old St. Charles Rock Road in Bridgeton,
Missouri. The southeastern and northwestern parts of the landfill abut farmland.
Several commercial and industrial facilities are located near the landfill
(Figure 2.1). The nearest residential area is a trailer park located
approximately 1 km (0.6 mile) to the southeast. A major portion of the landfill
(roughly the northern three-fourths of the site) is located on the
floodplain, approximately 2 km (1.2 miles) from the Missouri River.
The zoning plan obtained from the Bridgeton Planning and Zoning Department for
properties on and adjacent to the landfill is shown in Figure 2.2. A portion
of the landfill, including site Area 1, is zoned M-l, which is designated for
light manufacturing; the northwest part of the landfill, including Area 2, is
zoned as single-family residential (R-l). This R-l zoning indicates the use to
which the land was originally intended. However, the landfill was extended over
the land zoned R-l, and the zoning plan was simply not changed to reflect the
new usage. Other discrepancies between land use and zoning are found in the
nearby Earth City Industrial Park (William Canney, Safety Supervisor of West
Lake Landfill, Inc., personal communication, March 1984). The land across
St. Charles Rock Road is zoned for light and heavy manufacturing. The
remainder of the property surrounding the landfill is zoned residential and
The West Lake Landfill was started in 1962 for the disposal of municipal and
industrial solid wastes, and to fill in the excavated pits from the quarry
operations that had been performed at the site since 1939 (Canney, personal
communication, March 1984). In 1974, the landfill was closed by the Missouri
Department of Natural Resources (MDNR) (Karen, 1976). * new sanitary landfill,
in an area of the West Lake Landfill property which is protected from groundwater
contact, now operates under an MDNR permit.
This new part of the landfill was opened in 1974. The bottom is lined with
clay and a leachate collection system has been installed. Leachate is pumped
to a treatment system consisting of a lime precipitation unit followed in
series by an aerated lagoon and two unaerated lagoons. The final lagoon
effluent is discharged into St. Louis Metropolitan Sewer District sewers.
The quarrying operation ceased in the spring of 1987 because not enough “good
rock” was left at the site.
The West Lake Landfill was owned from 1939 until 1988 by West Lake Landfill,
Inc., of 13570 St. Charles Rock Road, Bridgeton, Missouri. Most of the
landfill was sold in 1988 to Laidlaw Industries, Inc. The two areas which
contain the radioactive material were retained by West Lake Properties as the
principal properties of a subsidiary named Rock Road Industries, Inc.
2.5 Contaminated Areas
Radioactive contamination at the West Lake Landfill has been identified in two
separate soil bodies (Figure 2.3). Comparisons of radionuclide quantities and
of the activity ratios between radionuclides not in secular equilibrium, indicate
that the radioactive contamination in the separate soil bodies was derived from
the same source, i.e., the Cotter Corporation’s former Latty Avenue facility
in Hazelwood, Missouri (NRC, NUREG/CR-2722).
The northern area (referred to as Area 2) of contamination shown on Figure 2.3 4*
covers an area of 5.2 ha (13 acres) and lies above 5 to 6 m (16-20 ft) of landfill
debris. The contaminated soil forms a more or less continuous layer from
1 to 4 m (3 to 13 ft) in thickness, and amounts to approximately 100,000 m3
(130,000 yd3). Some of this contaminated soil is near or at the surface,
particularly along the face of the northwestern berm. Beneath the landfill
debris, the soil profile consists of 1 to 2 m (3 to 7 ft) of floodplain top
soil overlying 10 to 15 m (33 to 50 ft) of sand and gravel alluvium.
The southern area of contamination (referred to as Area 1) shown on Figure 2.3
covers approximately 1.1 ha (3 acres) and contains roughly 15,000 m3
(20,000 yd3) of contaminated soil. This body of soil is located east of the
landfill’s main office at a depth of about 1 m (3 to 5 ft), and is located over a
former quarry pit, which was filled in with debris. The depth of debris beneath
the contaminated soil is unknown, but is estimated to be 15 to 20 m (50 to 65 ft).
Limestone bedrock underlies the landfill debris.
About 75% of the landfill site is located on the floodplain of the Missouri
River. The site topography is subject to change because of the types of activities
(e.g., landfilling and quarrying) performed there. Figure 2.3 shows a
contour map of the site as of July 1986. The surface runoff follows several
surface drains and ditches which run in a northwest direction and drain into
the Missouri River.
Bedrock beneath the West Lake Landfill consists of Mississippian age limestone
of the Meramacean Series of the St. Louis and Salem formations, which extends
downward to an elevation of 58 m (190 ft) mean sea level (msl) (Figure 2.4).*
*Missouri Department of Natural Resources, Division of Geology and Land
Survey, Rolla, Missouri, Well Log Files.
The limestone is dense, bedded, and fairly pure except for intermittent layers
which consist of abundant chert nodules. The Warsaw Formation—also of
Mississippian age—lies directly beneath the limestone. The Warsaw is made up
of approximately 12 m (38 ft) of slightly calcareous, dense shale; this grades
into shaley limestone toward the middle of the formation (Figure 2.4) (Spreng,
1961). Bedrock beneath the site dips at an angle of 0.5° to the northeast.
Eight kilometers (5 miles) east of the site, the attitude of the bedrock is
reversed by the Florissant Dome; the bedrock dips radially outward from the
apex of this dome at a low angle (Martin, 1966).
Since karst (solution) activity often occurs in carbonate rocks, the possibility
of its occurrence in the West Lake Landfill area was considered. Brief
observation of the quarry walls at the landfill suggests that some solution of
the limestone has occurred, but this solution activity has apparently been
limited (see Section 2.8.1) to minor widening of joints and bedding planes near
the bedrock surface. Although karst activity within the limestone is relatively
minor, the upper surface of the bedrock is irregular and pitted as a result of
solution (Lutzen and Rockaway, 1971). This alteration of the bedrock surface
is greatest beneath the Missouri River floodplain.
Soil material in this area may be divided into two categories: Missouri River
alluvium and upland loessal soil. This demarcation is shown as the historical
edge of the alluvial valley in Figure 2.5. The division is made on the basis of
soil composition, depositions! history, and physical properties. Because the
West Lake Landfill lies over this transition zone, the surface material at the
site varies considerably from southeast to northwest.
The Missouri River alluvium (Figure 2.6) ranges in thickness from 12 m (40 ft)
beneath the landfill site to more than 30 m (100 ft) at mid-valley (Figure 2.7).
The upper 3 m (10 ft) of the soil profile consists of organic silts and clays,
that have been deposited by the Missouri River during floods.* Below this
*Missouri Department of Natural Resources, Division of Geology and Land Survey,
Rolla, Missouri, Well Log Files.
surface layer, the soil becomes sandy and grades to gravel at depths greater
than 5 to 10 m (16 to 33 ft). Because of the effects of channel scour, which
continues to grade the sediment after its initial deposition, the alluvium is
fairly homogeneous in a.horizontal direction and becomes progressively coarser
with depth (Goodfield, 1965). At the edges of the floodplain, the alluvium is
not as well graded, and a large amount of fine material is present in the deeper
sand and gravel.
The upland loessal soil (Figure 2.8) is generally thinner than the floodplain
soil, being usually less than 12 m (39 ft) thick, and was deposited during the
age of Pleistocene glaciation. The loess consists of silt-sized particles that
were transported by wind and deposited as a blanket over much of Missouri and
Illinois. On the hills near the West Lake Landfill, the loess layer may be as
much as 24 m (79 ft) thick. It consists of 6 to 9 m (20 to 30 ft) of fairly
pure silt (Peoria loess) overlying 6 to 15 m (20 to 49 ft) of clay silt (Roxana
loess) (Lutzen and Rockaway, 1971). This loess forms the hills to the southeast
of the landfill, but it has long ago been removed from the landfill site and
most of the surrounding valleys by erosion. The upper 1 m (3 ft) of the loess
has been altered to form a thin soil profile. It should be noted that loess has
a vertical permeability which is far greater than its horizontal permeability
(Freeze and Cherry, 1979). The total permeability of loess is greatly increased
by disturbance. The individual silt grains are generally quite angular, and
therefore may not be effectively compacted by the methods commonly used to consolidate
clay. The technique most effective in the compaction of loess would
employ vibration beneath a surcharge. A relict soil profile from 5 to 10 m
(16 to 33 ft) thick lies beneath the loess and directly on top of the bedrock.
This soil was formed as a residuum before Pleistocene glaciation and was subsequently
covered by the loess blanket. This soil is a highly consolidated
clay containing abundant chert fragments (Lutzen and Rockaway, 1971). In
addition to the natural geologic properties of the landfill, human disturbance
of the soil must also be considered since material within the landfill itself
can either limit or facilitate migration of leachate to the Missouri River
In order to prevent downward movement of leachate, it is now a common practice
to place a layer of compacted clay beneath sanitary landfills. Newer portions
of the landfill (constructed since 1974) have 2 to 3 m (7 to 10 ft) of clay at
the base and around the sides. Waste is covered every day with 15 cm (6 in.)
of compacted soil; the cover soil presently used is loess (of soil classifications
CL and A4) taken from southeast of the landfill (Reitz and Jens, 1983a).
If not properly compacted, this material may have a permeability of 0.0001 cm/sec
(0.00004 in./sec) or more. It is not known what procedures for compaction, if
any, were used at the landfill before 1974 since the site was unregulated in
design as well as in materials which were accepted for disposal. J.t is believed,
however, that there is no liner present beneath the northwestern portion
of the landfill, and that sanitary (and, possibly, some hazardous) material
was placed directly on the original ground surface. Since waste was periodically
covered with soil to minimize rodent and odor problems, the landfill
probably consists of discrete layers of waste separated by thin soil layers.
Both areas containing radioactive material are in these presumably unlined g^
above-ground portions of the landfill.
2.8.1 Subsurface Hydrology
Groundwater flow in the area surrounding the West Lake site is through two
aquifers: the Missouri River alluvium and the shallow limestone bedrock. The
base of the limestone aquifer is formed by the relatively impermeable Warsaw
shale at an elevation of about 58 m (190 ft) msl (Figure 2.4). This shale
layer has been reached, but not disturbed, by quarrying operations. Therefore,
the Warsaw shale acts as an aquiclude, making contamination of the deeper limestone
very unlikely. The Mississippian limestone beds have very low intergranular
permeability in an undisturbed state (Miller, 1977). However, a
strong leachate enters the quarry pit at an elevation of about 67 m (220 ft)
msl (pt. A on Figure 2.5). This leachate is migrating vertically through more
than 30 m (98 ft) of limestone. Explosive detonations associated with quarrying
operations will tend to cause fractures to propagate in the quarry wall. These
fractures have probably extended less than 10 m (33 ft) into the rock from the
quarry face. Beyond this, the rock probably remains undisturbed. These
fractures will tend to increase inflow to the quarry pit and allow leachate to
percolate downward through the fractured zone. Thus, leachate inflow to the
quarry pit 1s not evidence of large-scale contamination of the limestone
aquifer. The only other mechanism by which leachate could travel’ rapidly
through the limestone is by transport through solution channels. ‘ Landfill consultants
and quarry operators maintain that the limestone is fairly intact
(Canney, personal communication, September 1983), and superficial observation
of the quarry walls seems to support this conclusion. Since the limestone is
fairly impervious, and groundwater flows in most areas from the bedrock into *,
the alluvium, contamination of water in the bedrock aquifer does not appear
The water table of the Missouri River floodplain is generally within 3 m (10 ft)
of the ground surface, but at many points it is even shallower. At any one
time, the water levels and flow directions are influenced by both the river
stage and the amount of water entering the floodplain from adjacent upland
areas. A high river stage tends to shift the groundwater gradient to the
north, in a direction that more closely parallels the Missouri River. Local
rainfall will shift the groundwater gradient to the west, toward the river and
along the fall of the ground surface. This is inferred from water levels
measured in monitoring wells at the West Lake site. The fact that groundwater
levels commonly fluctuate more than does the Missouri River level, indicates
that upland-derived recharge exerts a great deal of influence over groundwater
flow at the West Lake site. This influence decreases toward the river.
The deep Missouri River alluvium acts as a single aquifer of very high permeability.
This aquifer is relatively homogeneous in a downstream direction,
and decreases in permeability near the valley walls. The deeper alluvium is
covered by 2 to 4 m (7 to 13 ft) of organic silts and clays that may locally
contain a large fraction of sand-sized particles. Water levels recorded between
November 1983 and March 1984 in monitoring wells at West Lake* indicate a
groundwater gradient of 0.005 flowing in a N 30°W direction beneath the northern
portion of the landfill. This represents the likely direction of any possible
leachate migration from the landfill (Figure 2.5).
*Data supplied by Reitz and Jens engineering firm, St.Louis, 1984.
The alluvial aquifer recharges from upland areas from three sources: seepage
from loess and bedrock bordering the valley, channel underflow of upland streams
entering the valley, and seepage losses from streams as they cross the floodplain.
Of these sources, streams and their underflow represent the main source
of upland recharge to the alluvial aquifer. Streams entering the floodplain
raise the water table in a fan-shaped pattern radiating outward from their point
of entrance to the plain. In areas where streams are not present, the water
slopes downward from the hills, steeply at first and then gently to the level
of the free water surface in the Missouri River channel. The situations described
above do not take into account the effect of variations in permeability
of the shallow soil layer. Aerial photography of the site indicates that a
filled backchannel (oxbow lake) type of soil deposit is present along the southwest
boundary of the landfill (USDA, 1953). This deposit is probably composed
of fine-grained material to the depth of the former channel (6 to 10 m)
(20 to 33 ft). This deposit may tend to hamper communication between shallow
groundwater on opposite sides of the deposit.
Since no other recharge sources exist above the level of the floodplain, the
only water available to leach the landfill debris is that resulting from rainfall
infiltrating the landfill surface. Because the underlying alluvial aquifer
is highly permeable, there will be little “mounding” of water beneath the
landfill. Because the northern portion of the landfill has a level surface it
is likely that at least half of the rainfall infiltrates the surface. The
remaining rainfall is lost to evapotranspiration and (to a lesser degree) surface
runoff. Due to the height of the berm, temporary impoundment of surface
runoff is a common occurrence.
No public water supplies are drawn from the alluvial aquifer near the West Lake
Landfill. It is believed that only one private well (Figure 2.9) in the vicinity
of the landfill is used as a drinking water supply. This well is 2.2 km
(1.4 miles) N 35°W of the former Butler-type Building location on the West Lake
Landfill. In 1981, analysis showed water in this well to be fairly hard (natural
origins) but otherwise of good quality (Long, 1981).
Water in the Missouri River alluvium is hard and usually contains a high
concentration of iron and manganese (Miller, 1977). The amount of dissolved
solids present in the water of the alluvial aquifer varies greatly; purity
increases toward mid-valley where groundwater velocity is greatest. A water
sample from a well in the alluvium 3 km (1.9 miles) north of the landfill had
a total dissolved solids content of 510 mg/liter and total hardness as CaC03
of 415 mg/liter. Water in the limestone bedrock generally has a hardness
greater than 180 mg/liter as CaC03 equivalent (Emmett and Jeffery, 1968). Total
dissolved solids range from 311 to 970 mg/liter. Water in the limestone aquifer
may contain a large amount of sulfate of natural origin (Miller, 1977).
2.8.2 Surface Hydrology
Because of the extremely low slope of the Missouri River flood plain surface,
precipitation falling on the plain itself generally infiltrates the soil rather
than running off the surface. The only streams present on the floodplain are
those that originate in upland areas. Drainage patterns on the plain
(Figure 2.9) have been radically altered by flood control measures taken to
protect Earth City (Figure 2.1) and by drainage of swamps and marshes. Before
these alterations, Creve Coeur Creek passed just south of the landfill, and
drained a fairly large area. It has since been redirected to discharge into
the Missouri River upstream (south) of St. Charles (Figure 2.9). The-old
channel still carries some water, and empties into the Missouri River 45.2 km
(28 miles) upstream from the confluence with the Mississippi River. Near the
landfill, this stream is usually dry. As it crosses the flood plain, the creek
passes through shallow lakes which provide a more or less continuous flow to
the Missouri River throughout the year. A second stream, Cowmire Creek, crosses
the floodplain east of the site. This stream flows northward and joins a backwater
portion of the Missouri River at kilometer 35.4 (22 miles). Because of
the relationship which exists between river level and groundwater level in portions
of the floodplain near the river, these streams may either lose flow (at
low stage) or gain flow (at high stage).
The present channel of the Missouri River lies about 3 km (2 miles) west and
northwest of the landfill. Early land surveys of this area indicate that
200 years ago the channel was located several hundred meters to the east (toward
the landfill) of its present course (Reitz and Jens, 1983b). The Missouri River
has a surface slope of about 0.00018 (Long, 1981). River stage at St. Charles
[kilometer 45.2 (mile 28)] is zero for a water level of 126.1 m (413.7 ft) msl
(Reitz and Jens, 1983a). Average discharge of the Missouri River is 2190 m3/s
(77,300 ft3/s), with a maximum flow of 2850 mVs (101,000 ftVs) for the period
of April through July, and a minimum flow of 1140 m3/s (40,300 ft3/s) in January
and December (Miller, 1977). Some average properties of Missouri River water
for the period 1951-1970 were: alkalinity = 150 mg/liter as CaC03 equivalent;
hardness = 209 mg/liter as CaC03 equivalent; pH = 8.1; and turbidity = 694 JTU
(Jackson turbidity unit).
Water supplies are drawn from the Missouri River at kilometer 46.6 (mile 29)
for the city of St. Charles, and the intake is located on the north bank of the
river. Another intake at kilometer 33 (mile 20.5) is for the St. Louis Water
Company’s North County plant (Reitz and Jens, 1983a).
The city of St. Louis takes water from the Mississippi River, which joins the
Missouri River downstream from the landfill. In this segment of the river, the
two flow-streams have not completely mixed and the water derived from the
Missouri River is still flowing as a stream along the west bank of the
Mississippi River channel*. The intake structures for St. Louis are on the
east bank of the river so that the water drawn is derived from the upper
The climate of the West Lake area is typical of the midwestern United States,
in that there are four distinct seasons. Winters are generally not too severe
and summers are hot with high humidity. First frosts usually occur in October;
and freezing temperatures generally do not persist past March. Rainfall is
greatest in the warmer months, (about one-quarter of the annual precipitation
occurs in May and June) (Figure 2.10) (NRC, 1981). In July and August, thunderstorms
are common, and are often accompanied by short periods of heavy rainfall.
Average annual precipitation is 897 mm (35.3 in.), which includes the average
annual snowfall of 437 mm (17.2 inches snow). Average relative humidity is 68%,
*Ned Harvey, hydrologist with the USGS, telephone communication, August 1983.
and humidities over 80% are common during the summer. Wind during the period of
December through April is generally from the northwest; winds blow mainly from
the south throughout the remainder of the year. A compilation of hourly wind
observations shows that although the wind resultant is fairly consistent on a
monthly basis, the wind actually shifts a good deal and is very well distributed
in all directions (Figure 2.11) (NRC, 1981; U.S. Department of Commerce,
Meteorological data used is from Lambert Field International Airport which is
6 km (3.7 miles) east of the West Lake site. Temperature and precipitation
data are also representative of West Lake. However, because of differences in
topography between Lambert Field and the site, the actual wind directions at
West Lake may be slightly skewed in a NE-SW direction parallel to the Missouri
The West Lake Landfill is biologically and ecologically diverse. Rather than a
single ecological system (e.g., a prairie), it is a mosaic of small habitats
(1) moist bottomland and farmland adjacent to the perimeter berm
(2) poor quality drier soils on the upper exterior and interior slopes
of the berm
(3) an irregular waste ground surface associated with the inactive portion of
(4) aquatic ecosystems present in low spots on the waste ground surface
Generally, the natural systems which are present are limited by operations in
the active portion of the landfill and form a corridor along the perimeter berm
from near well site 75 (Figure 2.5), on the Old St. Charles Rock Road, clockwise
to the main entrance to the landfill near well site 68, along St. Charles Rock
Road. The following observation and descriptions demonstrate the biological
variety of these sites.
The flora of the perimeter berm extending from the southwest clockwise to the
area of the main entrance to the landfill present a series of contrasts. Along
the Old St. Charles Rock Road, the bottom and lower slope of the berm is heavily
influenced by the nearby mature silver maple (Acer saccharinum), boxelder
(Acer negundo). oak (Quercus). sycamore (Platanus). green ash (Fraximus
pennsylvanica). and eastern cottonwood (Populus deltoides) trees associated
with the old channel of Creve Coeur Creek. At the corner, between wells 59 and
60 (Figure 2.5), large silver maple and boxelder trees form a dense stand in the
moist soils at the base of the berm. The density of these trees declines on
this slope extending toward the north (well 61) and the Butler-type Building
corner. The extension of this slope toward the northwest is dominated by a
dense willow-like thicket in which a few eastern cottonwoods and a hawthorn
tree have established. From this northwest corner of the landfill to the
eastern limit of the trees between the landfill and St. Charles Rock Road (well
65), the exterior slope of the berm is dominated by dense stands of small and
large eastern cottonwoods. This latter occurrence reflects the influence of
the well-established eastern cottonwoods and sycamores associated with the permanent
pond just north of this site (Figure 2.9). The ground cover along
these exterior slopes consists of grasses, forbs, plants common to disturbed
areas, seedling cottonwoods, and shrubs. A well-manicured grass groundcover
continues from the limit of the trees to the area around the main entrance of
the landfill and well 68. This vegetation contributes to the partial stabilization
of the steep exterior slopes.
The somewhat drier top and the short, interior slope of the berm, colonized by
prairie grasses such as bluestem (Andropogon). blends into the irregular surface
of the inactive portion of the landfill. Depressions in this surface
allow water to collect and tall grasses, foxtail, and plants characteristic
of disturbed areas [e.g., ragweed (Ambrosia), mullein (Verbascum). pokeweed
(Phytolacca). cinquefoil (Potentilla). sunflower (Helianthus), and plantain
(Plantago)] are replaced by characteristic wetland species [e.g., algae
(Spirogyra). cattails (Typha). sedges (Carex). and smartweed (Polygonium)].
Young eastern cottonwoods are established at several of these wet sites.
Generally, the surface vegetation of the inactive landfill gives way to barren
waste ground around the Butler-type Building location and the barren terrain
associated with recent landfill activities.
Animals were observed associated with these habitats. Cottontail rabbits
(Sylvilagus) were encountered most frequently and their fecal pellets were observed
on the landfill. Density of fecal material was particularly heavy in
the thickets on the exterior slopes of the perimeter berm. In this regard,
coyote (Cam’s latrans) feces containing rabbit fur were observed. Small mammals
(rodents) were not seen but could certainly be present in these areas. Large
ungulates also were not sighted, but tracks and feces of white-tailed deer indicate
that they utilize the landfill.
The only birds observed were a crow (Corvus). several robins (Turdus). and whitecrowned
sparrows (Zonotrichia leucophrys). This certainly does not reflect the
extent to which birds utilize these habitats, for observations were made early
in the spring. It is readily apparent that returning migratory passerines would
utilize the surface vegetation and berm thickets for nesting, cover, and feed
later in the season. It is also possible that waterfowl could utilize the permanent
ponds on the landfill and adjacent to St. Charles Rock Road. Twelve scaup
(Aythya) and mallards (Anas) were observed on the lagoon which serves as part
of the landfill waste water treatment facility.
Small puddles contained characteristic aquatic invertebrates and at least two
species of amphibians. Casual examination of these shallow waters revealed
three genera of snails (Physa, Lymnaea, Helisoma), an isopod (Asnellus),
cyclopoid copepods, and cladocerans. Aquatic insect larvae were not observed;
however, this does not rule out their presence. The sighting of a bullfrog
tadpole (Rana catesbeiana) and audition of spring peepers (Hyla). indicates
these ponds are utilized as breeding sites. No fish were observed in these
puddles on the landfill surface; however, a dead gizzard shad (Dorsoma cepedianum)
was seen in the pond adjacent to St. Charles Rock Road. The only reptiles
seen were the water snake (Nerodia) and the garter snake (Thamnophis).
Although the northwest inactive portion of the landfill is posted with “No
Trespassing” signs, it was evident that humans do encroach on these habitats.
Fishing tackle was found tangled in power lines and trees, and spent smallgauge
shotgun shells were found on the landfill surface and berms.
The West Lake Landfill is located in the northwestern portion of the city of
Bridgeton, in St. Louis County, Missouri. Earth City Industrial Park is located
on the floodplain 1.5 to 2 km (0.9 to 1.2 miles) northwest of the landfill.
Population density on the floodplain is generally less than 10 persons per
square kilometer (26 persons per square mile); and the daytime population
(including factory workers) is much greater than the number of full-time residents.
Major highways in the area include Interstate 70 (1-70) and Interstate 270
(1-270), which meet south of the landfill at Natural Bridge Junction (Figure
1.1). The Earth City Expressway and St. Charles Rock Road lie, respectively,
west and east of the landfill. The Norfolk and Western Railroad passes about
1 km (0.6 mile) from the northern portion of the landfill (Figure 1.1). Lambert
Field International Airport is located 6 km (3.7 miles) east of the West Lake
In addition to factories at Earth City, plants are operated by Ralston-Purina
and Hussraan Refrigeration across St. Charles Rock Road. The employees of
these two plants probably comprise the largest group of individuals in close
proximity to the contaminated areas for significant periods of time. The
Ralston-Purina facilities are located 0.4 km (0.2 mile) northeast of the
Butler-type Building location at the landfill. Considering that land in this
area is relatively inexpensive and that much of it is zoned for manufacturing,
industrial development on the floodplain will likely increase in the future.
Two small residential communities are present near the West Lake Landfill.
Spanish Lake Village consists of about 90 homes and is located 1.5 km (0.9 mile)
south of the landfill, and a small trailer court lies across St. Charles Rock
Road, 1.5 km (0.9 mile) southeast of tf- site (Figure 2.1). Subdivisions are
presently being developed 2 to 3 km (1.2 to 1.9 miles) east and southeast of the
landfill in the hills above the floodplain. Ten or more houses lie east of the
landfill scattered along Taussig Road. The city of St. Charles is located
north of the Missouri River at a distance greater than 3 km (1.9 miles) from
Areas south of the West Lake Landfill are zoned residential; areas on the
other sides are zoned for manufacturing and business (Figure 2.2). Most of
the landfill is zoned for light manufacturing (M-l). However, approximately
0.3 km2 (0.12 mi2) of the northern portion of the landfill is zoned for residential
use; this includes the contaminated area around the Butler-type Building
site. The field northwest of the landfill between Old St. Charles Rock Road
and St. Charles Rock Road 1s under cultivation. Trends indicate that the
population of this area will increase, but the land will probably be used
primarily for industrial facilities.
Figure 2.1 Land use around West Lake Landfill site
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Figure 2.4 Bedrock stratigraphy
——— Landfill Boundary
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A LMchat* Collection
100m 200m 300m 400m
HISTORICAL EDGE OF
Figure 2.5 Location of monitoring wells
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1 Figure 2.6 Soil profile of river alluvium
(ml (ft) NORTHWEST
«*>-(V MISSOURI LANDFILL
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MISSOURI RIVER FLOOD PLAIN
SHALLOW FLOOD PLAIN ALLUVIUM
(Sand and Gravel)
Figure 2.7 Cross-section of Missouri River alluvial valley
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<-*- ^- A-/ ttg&R •V_- ^ r^~r ^rT-&lr ^'^l Thickness meters (feet) 2 3 (6.6 • 10) 6 - 9 (20-30) 6- IS (20 - 50) 5- 10 (17 - 33) Description Organic silts and clays (topsoil) Peoria loess, silt Roxana loess, silty-clay Well-consolidated clay residium Limestone bedrock Figure 2.8 Soil profile of upland loessal soil 2-23 ro i IVJ Sect* 1 24.000 LIOfNO: ^0) Standing WMW •"-**"• P«M>nl«l SlrMm
Figure 2.9 Surface hydrology of West Lake area
Figure 2.10 Average monthly precipitation at Lambert Field
6.2% I (calm) | 3.9%
Wind rose is for Lambert Field International Airport,
Hazelwood, Missouri, and shows the percentage of hourly
observations in each direction along with the average
speed in that direction; for example: wind blew from
the north 4.5% of the time at an average speed of 3.76 m/s.
Figure 2.11- Wind distribution for West Lake area
I 3 RADIOLOGICAL CHARACTERIZATION OF THE SITE
3.1 Radiological Surveillance
Approximately 43,000 mt (47,000 tons) of contaminated soil were reported to have
• been disposed of in the landfill. A fly-over radiological survey performed for
• .the NRC in 1978 identified two areas of contamination at the West Lake Landfill.
I Subsequently, from August 1980 through the summer of 1981, the Radiation
Management Corporation (RMC), under contract to the NRC, performed an onsite
| evaluation of the West Lake Landfill (NRC, NUREG/CR-2722). The purpose of this
survey was to clearly define the radiological conditions at the landfill. The
• results were to be utilized in performing an engineering evaluation to determine
if remedial actions should and could be taken.
The area to be surveyed was divided into 10-m (33-ft) grid blocks and included
• the following measurements:
1 (1) external gamma exposure rates 1 m (3.3 ft) above the surfaces and betagamma
count rates 1 cm (0.4 in.) above surfaces
g (2) radionuclide concentrations in surface soils
• (3) radionuclide concentrations in subsurface deposits
• (4) gross activity and radionuclide concentrations in surface and subsurface
• (5) radon flux emanating from surfaces
• (6) airborne radioactivity
| (7) gross activity in vegetation
3.2 Survey Results
Figure 3.1 shows the two areas of elevated external radiation levels as they
existed in November 1980, at the time of the preliminary RMC site survey. As
can be seen, both areas contained locations where levels exceeded 100 uR/hr at
1m (3.3 ft). In Area 2, gamma levels as high as 3000 to 4000 uR/hr were
detected. The total areas exceeding 20 |jR/hr were about 1.2 ha (3 acres) in
Area 1 and 3.6 ha (9 acres) in Area 2.
External gamma levels measured in May and July of 1981 decreased significantly,
especially in Area 1, because approximately 1.2 m (4 ft) of sanitary fill was
added to the entire area and an equal amount of construction fill was added to
most of Area 2. As a result, only a few hundred square meters (a few thousand
square feet) in Area 1 exceed 20 uR/hr. In Area 2, the total area exceeding
20 uR/hr decreased by about 10%, and the highest levels were about 1600 uR/hr,
near the location of the Butler-type building.
Surface Soil Analyses
A total of 61 surface soil samples were gathered and analyzed on site for gamma
activity. Samples were normally stored 10 to 14 days to allow ingrowth of radium
daughters. Concentrations of U-238, Ra-226 (from Pb-214 and Bi-214), Ra-223,
Pb-211, and Pb-212 were determined for each sample. Surface soil samples are
located in Figures 3.2 and 3.3.
In all soil samples, only uranium and/or thorium decay chain nucTides and K-40
were detected. Offsite background samples were on the order of 2 pCi/g Ra-226.
Onsite samples ranged from about 1 to 21,000 pCi/g Ra-226, and from less than
10 to 2100 pCi/g U-238. In those cases where elevated levels of Ra-226 were
detected, the concentrations of U-238 were generally anywhere from a factor of
2 to 10 lower. In cases of elevated sample activity, daughter products of both
U-238 and U-235 were found.
In general, surface activity was limited to Area 2, as indicated by surface
beta-gamma measurements. Only two small regions in Area 1 showed contamination;
both were near the access road across from the site offices.
In addition to onsite gamma analyses, 12 samples were submitted to RMC’s radiochemical
laboratories for thorium and uranium radiochemical determinations. The
results show all samples contain high levels of Th-230. The ratio of Th-230 to
Ra-226 (Bi-214) is about 20 to 1.
Subsurface Soil Analysis
Subsurface contamination was assessed by extensively “logging” holes drilled
through the landfill. Several holes were drilled in areas known to contain contamination,
then additional holes were drilled at intervals In all directions
until no further contamination was encountered. A total of 43 holes were
drilled, 11 in Area 1 and, in Area 2, 32 including 2 nearby offsite wells for
monitoring water. All holes were drilled with a 6-in. auger and lined with 4-in.
PVC (polyvinyl chloride) casing. The location of these auger holes is shown in
Figures 3.4 and 3.5.
Each hole was scanned with an Nal(Tl) detector and rate meter system for an
initial indication of the location of subsurface contamination. On the basis
of the initial scans, 19 holes were selected for detailed gamma logging using
the intrinsic germanium (IG) detector and multiple channel analyzer.
The results of the Nal(Tl) counts and IG analyses show concentrations of Bi-214,
as determined by the IG system, ranged from less than 1 to 19,000 pCi/g. For
those holes where both Nal(Tl) counts and IG counts were made, a good correlation
between gross Nal(Tl) counts and Ra-226 concentrations, as determined by
in situ analysis of the daughter Bi-214 by the IG system, was found.
It was determined that the subsurface deposits extended beyond areas where surface
radiation measurements exceeded 5 pCi/g. The approximate area of subsurface
contamination compared to the area of elevated surface radiation levels shows a
total difference in areas of 2 ha (5 acres).
The variations of contamination with depth for Areas 1 and 2 are shown in
Figure 3.6. As can be seen, the surface elevations vary by about 6 m (20 ft),
and the highest elevations occur at locations of fresh fill. Contamination
(>5 pCi/g Ra-226) in several areas is found to extend from the surface to
appreciable depths, about 6 m (20 ft) below the surface in two cases. In
general, the subsurface contamination appears to be a continuous single layer,
ranging from 0.6 to 4.6 m (2 to 15 ft) thick, located between elevations of 139
to 144 m (455 to 480 ft) and covering 6.5 ha (16 acres) total area.
In Figures 3.7 and 3.8, representations of the subsurface deposits are provided
on the basis of auger hole measurements. These representations are consistent
with the operating history of the site, which suggests that the contaminated
material was moved onto the site and spread as cover over fill naterial. Thus,
one would expect a fairly continuous, thin layer of contamination, as indicated
by survey results.
Six composite samples were submitted to RMC’s Environmental Chemistry Laboratory
for priority pollutant analysis. Five samples were taken from auger holes
(one from Area 1 and four from Area 2) and the sixth from the West Lake leachate
treatment plant sludge. The results indicate a significant presence of
organic solvents in Area 2 samples. The results of the leachate sludge
analysis were not as high as any of the soil samples.
A chemical analysis of radioactive material from both areas was also performed
by RMC’s laboratory. Results show elevated levels of barium and lead in most
Background Radioactivity Measurement
Various offsite locations were selected for reference background measurements.
The results of these measurements were within the normal range.
Airborne Radioactivity Analyses
Both gaseous and particulate airborne radioactivity were sampled and analyzed
during this study. Since it was known that the buried material consisted partially
or totally of uranium ore residues, the sampling program concentrated on
measuring radon and its daughters in the air. Two methods were used: the first
was a scintillation flask method for radon gas and the second was analysis of
filter paper activity for particulate daughters.
A series of grab samples using the accumulator method were taken between May
and August of 1981. A total of 11! samples from 32 locations was collected.
Measurable radon flux levels ranged from 0.2 pCi/m2s in low background areas
to 865 pCi/m2s in areas of surface contamination.
At three locations, repetitive measurements were made over a period of 2 months.
These results are plotted in Figure 3.9. As can be seen, significant fluctuations
were observed at two locations. The fact that these fluctuations were
real and not measurement artifacts was later confirmed by duplicate charcoal
canister samples, as described below.
A total of 35 charcoal canister samples was gathered at 19 locations over a
3-month period. The results show levels ranging from 0.3 pCi/m2s to 613
pCi/m2s. On 24 different occasions, the charcoal canisters and accumulator
were placed in essentially the same locations, at the same time, for duplicate
sampling. The results of this side-by-side study show generally good
correlation between the two methods.
A set of 10-minute high-volume particulate air samples was taken to determine
both short-lived radon daughter concentrations and long-lived gross alpha
activity. The highest levels were detected in November 1980, near and inside
the Butler-type building which has since been removed. These two samples
approximately equal NRC’s 10 CFR Part 20, Appendix 6, alternate concentration ‘
limit of one-thirtieth WL for unrestricted areas.
In addition to the routine 10-minute samples, five 20-minute high-volume air
samples were taken and counted immediately on the IG gamma spectroscopy system
to detect the presence of Rn-219 daughters. All samples were taken near surface
contamination. In addition to Rn-222 daughter gamma activities, Rn-219
daughters were detected by measuring the low-abundance gamma rays of Pb-211.
Concentrations of Rn-219 daughters ranged from 6 x 10-11 to 9 x 10-10 uCi/cc.
Vegetation samples included weed samples from onsite locations and farm crop
samples (winter wheat) near the northwest boundary of the landfill. This location
was chosen because runoff from the fill onto the farm field was possible.
No elevated activities were found in these samples. ^
A total of 37 water samples was taken: 4 in the fall of 1980, and the remainder
in the spring and summer of 1981. One sample was equal to the U.S. Environmental
Protection Agency (EPA) gross alpha activity standard for drinking water of
15 pCi/liter and that was a sample of standing water near the Butler-type
building. Several samples, including all the leachate treatment plant samples,
exceeded the EPA drinking water screening level for gross beta which would
require isotopic analyses. Subsequent isotopic analyses indicated that the
beta activity could be attributed to K-40. None of the offsite samples 4.
exceeded either EPA standard or screening level.
In 1981, MDNR collected 41 water samples which RMC analyzed for radioactivity
(Table 3.1). Of these samples, 5 were background, 10 were onsite surface
water, 10 were shallow groundwater standing in boreholes, and 16 were landfill
leachate. From these data, background activity is estimated as 1.2 pCi/liter
gross alpha and 27 pCi/liter gross beta. Results in Table 3.1 show the
gross alpha in two water samples exceeded or equaled 15 pCi/1; the gross beta in
ten water samples exceeded 50 pCi/1. Most of the gross beta activity comes from
7 naturally occurring K-40 as determined from subsequent isotopic analysis.
In addition, groundwater samples in perimeter monitoring wells at the West
Lake Landfill were taken by UMC personnel and ORAU in 1983, 1984, and 1986.
The well locations are shown in Figure 2.5 and the results are presented in
Tables 3.2 and 3.3. Results in Table 3.2 show the gross alpha in two water samples
slightly exceeded 15 pCi/1; the gross beta were all below 50 pCi/1 in all water
samples. Table 3.3 shows analyses were below 15 pCi/1 for gross alpha and 50 pCi/1
for gross beta for all the wells.
3.3 Estimation of Radioactivity Inventory
In examining the RMC report for bore hole samples (Table 3.3), it is noted that
the naturally occurring U-238 to Th-230 to Ra-226 equilibrium has been disturbed.
The RMC report (NRC, NUREG/CR-2722) indicates that the ratio of Ra-226 to U-238
is on the order of 2:1 to 10:1. This observation is consistent with the history
of the radionuclide deposits in the West Lake Landfill, i.e., that they came
from the processing of uranium ores to extract the uranium content and that the
radioactive material at West Lake came from the former Cotter Corporation
facility on Latty Avenue (presently occupied by Futura Coatings Company) in
Hazelwood, Missouri. This location contains contamination from ore processing
residues from which uranium had been previously separated, leaving the daughters
behind at relatively higher concentrations. Additionally, it is noted in the
RMC report that the ratio of Th-230 to Ra-226 is on the order of 5:1 to 50:1.
This indicates that radium has also been removed. Other data are available in
the Latty Avenue site study (Cole, 1981). Table 3.4 presents the radionuclide
concentrations in Latty Avenue composite samples.
Using the RMC data and averaging the auger hole measurements over the two volumes
of radioactive material found in Areas 1 and 2, a mean concentration of 90 pCi/g
was calculated for Ra-226. Also, the ratios of Th-230 to Ra-226 were established
since the level of Th-230 will determine the increase of Ra-226 with
time. Although the ratio of Th-230 to Ra-226 ranged from 5:1 to 150:1, most of
the data were in the 30:1 to 50:1 range. To ensure conservatism in estimating
the long-term effects of Ra-226, a ratio of 100:1 was used for all further
Using the Th-230:Ra-226 ratio of 100:1, the Th-230 activity is 9000 pCi per
gram. If the U-238 concentration (as well as U-234 which would be similarly
separated from the ore) is a factor of 5 less than Ra-226, this implies about
18 pCi U-238 per gram. The total mass of radioactive material (having Ra-226
concentrations of 5 pCi/g or more) In the landfill was estimated by visually
integrating the volume of radioactive material from graphs and multiplying by
an average soil density, resulting in 1.5 x 1011 grams (150,000 metric tons) of
contaminated soil. These numbers indicate that there are about 14 Ci of Ra-226
contained with its decay products in the radioactive material in the landfill.
The material also contains about 3 Ci each of U-238 and U-234, and about 1400 Ci
of Th-230. These estimates indicate the order of magnitude of the quantities
to be dealt with, although the estimate for Th-230 is regarded as conservatively
ST. CHARLES ROCK ROAD
Source: NUREG/CR-2722, Figure 3, p. 27.
Figure 3.1 External gamma radiation levels (November 1980)
Source: NUREG/CR-2722, Figure 7, p. 31.
Figure 3.2 Location of surface soil samples, Area 1
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