Appropriateness
of a statistical sampling strategy is dependent on the data objectives,
environmental media of interest, knowledge of site conditions and waste
properties, and analytical method requirements. The data objective of the
B-20 closure investigation is to identify specific hazards at the site and to
sufficiently quantify those hazards. During the closure investigation, the
environmental media of concern at the B-20 site are surface and subsurface
soils, surface water, and sediments. Information regarding the site
conditions and contaminant distribution exist in the form of past operation
knowledge and preliminary site investigation results. Specific analytical
methods for closure investigation are described in section
4.3.5, and are not expected to influence the sampling strategy.
Based on these factors, a statistical sampling strategy was developed for each
environmental media of concern at the B-20 site.
Waste
disposal activities at B-20 occurred at or near the ground surface. Also,
open detonation activities may have resulted in some areal dispersion of waste
residues. Surface soil appears to be the primary environmental media of
concern. Any contamination present in surface soils may pose direct and
indirect exposure risks. Based on these factors, the data objective for
surface soil samples is to obtain sufficient data for the baseline RA (section
5).
Substantial
information is available on the site conditions and waste management activities
that may influence the contaminant distribution in surface soils at the B-20
site. The open detonation area appears to be limited to northern and
central portions of the site as indicated by the presence of craters (Figure
2.3). However, areas that do not contain craters may have been used
for unrecorded disposal of small munitions or may not have recently been used
for disposal activities. The surface soils around the craters are
considered probable zones of higher contamination than the rest of the site.
A
combination of systematic random sampling and judgmental sampling is proposed
for surface soils at the B-20 site. Given the large area of the site (27.5
acres), application of simple random sampling would be cost prohibitive.
Furthermore, considering the available site information, the use of judgmental
sampling is appropriate and effective. However, large areas, such as
quadrants A and H, exist where waste disposal activities may not be apparent to
perform reliable judgmental sampling. Systematic random sampling will be
used to obtain data for such areas. Proposed surface soil sampling
locations for the B-20 area are shown in Figure 4.1.
The
judgmental surface soil sampling at B-20 will consist of one soil sample from
within selected crater areas and at least one sample within approximately 50
feet from the edge of those craters. Exact locations of the judgmental
samples will be determined by the sampler in the field. These samples will
provide contaminant data for suspected "hot spots" (craters) and in
the immediate vicinity (kickout zones). There are 15 craters identified at
the site. Craters 1 and 5 were previously sampled and found to contain
arsenic above MSCs, thus these craters will be sampled again. Crater 13
did not contain metals above MSCs and will not be resampled. Also, craters
10 through 15 in quadrant D are clustered together. Judgmental sampling
will be used in this quadrant to sample two craters and two kickout zones.
The resulting data is judged to be representative of the six-center
cluster. Altogether, half of the fifteen craters will have judgmental
samples collected at and near them for a total of fourteen judgmental surface
soil samples.
The
systematic random sampling will comprise one surface soil sample collected at
the nodes of a regular grid spaced at 250 feet. The starting point for
layout of the grid will be randomly chosen at the site. In the vicinity of
the craters, judgmental samples may replace systematic random samples. An
estimated 26 surface soil samples may be collected through systematic random
sampling. Together, this sampling strategy is estimated to yield
approximately 40 surface soil samples or about 1.5 samples per acre area.
This sample density is considered sufficient for the purposes of conducting the
baseline RA.
Subsurface
soil or rock contamination may exist at B-20 due to below-grade detonation of
the ammunition and contaminant migration from surface to deeper soils or the
limestone bedrock. Subsurface soil/rock contamination may pose exposure risks
during construction activities involving site disturbances, or by acting as a
source for groundwater contamination. Currently, no analytical data are
available for the B-20 subsurface soils or bedrock.
During
the preliminary investigation (section 2.5), no organic contaminants were
found in surface soils, and only low levels of metals were present.
Considering the low vertical migration potential of metals, subsurface soil
contamination from surface soils is unlikely, and thus, general contamination of
subsurface soils is unlikely. Furthermore, the estimated depth to
groundwater at the site appears to be relatively large (200 feet or
greater). Hence, the subsurface rock (which has a low potential for
contamination) is not expected to impact the groundwater. Based on these
factors, subsurface rock does not appear to be an environmental media of
significant concern. Therefore, contaminant identification and
quantification are limited to suspected areas of subsurface contamination such
as the craters where contaminant release below grade may have occurred during
open detonation.
Based
on the above discussion, judgmental sampling in the areas of suspected
contamination is proposed for subsurface soil/rock sampling. Therefore,
two subsurface soil/rock samples will be collected from each selected crater
using soil borings. As the craters were created by the same process, and
the materials in the pits that were destroyed were similar for each set of
shots, half of the craters will be selected for sampling. This number of
soil borings and associated subsurface soil samples should be adequate to
characterize the subsurface at B-20.
Contamination
may exist in sediments from surface migration of contaminants via runoff from
the site soils. Sediments may be found at the site in craters receiving
some site drainage, an ephemeral stream on the site, a pond located in quadrant
F, and the livestock pond. Sediments may pose similar types of exposure
risks as in the case of surface soils.
Low
levels of methylene chloride, bis(2-ethylhexyl)phthalate, and metals were
detected in sediment samples during the preliminary investigation (section
2.5). Therefore, these areas and others will be sampled for data
evaluation and verification. A systematic random sampling strategy was
chosen for sediments at the B-20 site. This sampling will involve randomly
choosing the first sampling point along the stream and then sampling both
upstream and downstream, as applicable, at approximately 400-foot
intervals. The downstream limit will be defined by the livestock pond and
the upstream limit will be the southern edge of the site where the stream
begins. This sampling strategy is estimated to collect approximately 4
sediment samples.
In
addition to the statistical sampling described above, judgmental sediment
samples from the livestock pond, the pond in quadrant F and crater 8 will be
collected. During the preliminary investigation, samples from these
locations showed the presence of organics, albeit at low levels.
Judgmental samples may also be collected from any other crater that contains
sediments at the time of the remedial investigation.
Surface
water at the site consists of an ephemeral stream, a pond in quadrant F and the
livestock pond. Surface water contamination may occur from the site
surface runoff. The surface water samples collected during the preliminary
site investigation contained low levels of metals. However, the metal
levels in the livestock pond sample were below the comparison criteria (Table
2.4). Surface water contamination may pose a threat to the area
ecology and groundwater quality.
Due
to the limited occurrence of this environmental medium at the site and
substantial information available, judgmental sampling of surface waters at the
B-20 site is found most suitable. Samples will not be collected from areas
that did not contain contaminants above comparison criteria during preliminary
sampling. Therefore, one surface water sample each will be collected from
the stream (if it contains water), the quadrant F pond and crater 8 water (if
not dry).
Background
samples will be collected for environmental media such as surface and subsurface
soils to establish chemical characteristics of environmental media not impacted
by any waste management activities. There are not acceptable background
locations at CSSA for collection of surface water and sediment samples which
would be comparable to these media at the B-20 site. A total of ten
background samples each will be collected for surface soils and subsurface
soils.
The
analytical data for the background samples will be statistically evaluated to
establish upper 95 percent confidence limit for each of the analytes. The
sample results exceeding the background 95 percent confidence limit will be
considered statistically different from the background results. However,
if all background results for an analyte are below detection limits, the
detection limits will be substituted for the background 95 percent confidence
limit.
The
remedial investigation of the B-20 area will be conducted in accordance with 31
TAC 335 Subchapter S and with the provisions of this plan. In accordance
with 31 TAC 335.6(d), CSSA will notify the EPA and the TNRCC in writing 10 days
prior to beginning any investigation activities at the B-20 site.
The
investigation activities are based on preliminary analytical results discussed
in section 2.5 of this document. The preliminary screening results
included fifteen craters, surface water drainages, site boundaries, and scrap
metal (inert remnants of exploded ordnance) over most of the site. Surface
soil, surface water, and sediment samples were collected.
The
preliminary analytical data showed explosives were not detected in any of the
samples. No volatile organics or semivolatile organic compounds were
detected in surface soil samples or surface water samples. It is notable
that no toluene or benzene (primary components of explosives but not degradation
products of explosives) were detected in any of the samples. However,
methylene chloride was found in three sediment samples, and the semivolatile
organic compound bis(2-ethylhexyl)phthalate was detected in crater 8 sediments.
Metals,
with the exception of selenium and silver, were detected in the samples.
Surface soils and surface water contained arsenic, barium, cadmium, chromium,
and lead. Sediments contained arsenic, barium, cadmium, chromium, mercury,
and lead. Laboratory-measured pH indicated slightly basic surface waters,
which would be expected because of limestone-weathered soils and limestone
bedrock of the region.
The
preliminary field mapping, observations, and analytical results were used to
better define the B-20 site for specification of closure actions. In
particular, the proposed remedial investigation activities are based on
preliminary results to effectively investigate the site for hazardous wastes
with a cost-efficient approach. The proposed activities were also compared
and found similar to actions used at UXO sites by Department of Defense
explosive ordnance specialists (EPA, 1993).
The
following activities are the first phase of the remedial investigation:
-
Prescreen
the site for the presence of unexploded ordnance (UXO) and mark safe areas
of traverse.
-
Perform
a magnetometer survey to locate subsurface UXO or scrap metal near areas of
drilling.
-
Drill
and sample soil borings near selected craters in the B-20 area to determine
both lateral and vertical extent of subsurface soil contamination.
-
Perform
verification sampling of surface soil, surface water, and sediments.
These
tasks are summarized in Table 4.1.
Standard
procedures for each of the above tasks include office and field
record-keeping. In the field, daily logs will be kept of that day's
activity, field team names, date, times of activities, weather, field changes,
personnel visiting the site, and field observations. Copies of the logs
will be kept in project files, as will copies of chain-of-custody forms.
The
data generated from this phase of investigation will be analyzed, verified, and
evaluated prior to preparing a remedial investigation report. Should the
data confirm that the site may be closed under risk reduction standard 2 without
additional data, and that no UXO was found after screening the entire site, the
report will be submitted to the EPA and the TNRCC with procedures, results,
verification, and request for amended closure.
Should
the data indicate that a baseline RA is necessary as the next step in closure
actions, the remedial investigation report will discuss the results and propose
additional work.
If
there is insufficient data to finalize the remedial investigation report, or if
additional data is required to perform a baseline RA, a second phase of remedial
investigation will be performed. The specific actions necessary to
complete the investigative data set or to prepare for a baseline RA will be
proposed and costed for the EPA and the TNRCC prior to initiating any phase II
remedial investigation field actions. Such actions might include
additional soil borings, drilling of groundwater monitoring wells, and
collection of additional samples in specified media. As it is unknown at
this time what phase II activities might be necessary, such activities are not
further discussed in this document.
Prior
to drilling or any other subcontractor actions, the site must be screened at the
surface for safe passage of persons and equipment. The preliminary
investigation identified site boundaries and craters (areas of most intense
demolition actions), but was not intended to define areas of safe traverse for
non-UXO-experienced personnel. CSSA has not had a UXO incident regarding
cattle and other wildlife that have roamed the site since the last demolition
actions in 1987. In addition, CSSA personnel knowledgeable in UXO
identification have walked through many portions of the site without observing
any UXO. Therefore, the potential for UXO appears low, but has not been
completely ruled out as a potential hazard at the B-20 site.
The
prescreening will be performed by a team of experienced and qualified UXO
professionals. The objectives of the prescreening will be to identify
potential UXO and areas of safe traverse for non-UXO personnel and
equipment. Safe traverse is defined as an area or corridor within which
there are no UXO and upon which it is safe to walk, drive mobile equipment, or
perform aboveground field actions.
The
first action of the UXO identification team will be to traverse the entire site
and visually identify potential UXO either partially buried or on the
ground. At most sites, this action would be performed along with a
magnetometer survey to detect UXO within a few feet of the ground surface (EPA,
1993). However, the B-20 site is unique insofar as the general depth of
soils is only a few inches deep (except in the crater areas), bedrock is
immediately below the soil, and inert scrap metal is abundant across the
site. A magnetometer survey could be performed during this task, but it is
likely that it will only detect scrap metal at the surface and that the
proximity of scrap metal pieces to each other would cause interference with the
magnetometer readings. Because of the lack of soils, buried UXO is likely
only in the crater areas. Outside of craters, it is more probable that
metal projectiles from demolition activities skipped against bedrock or were
partially buried in a few inches of soil.
Based
on the above discussion, the proposed action is to visually identify potential
UXO. The survey across the site will be in 5-foot traverses by an
experienced UXO team taking all necessary health and safety precautions for UXO
sites (EPA, 1993). Should potential UXO be found, the UXO personnel will
flag the area around the UXO object so as to differentiate it from areas of safe
traverse and mark the location on the base map. The potential UXO object
will then be verified by CSSA demolition experts. CSSA, RRAD, ES, and the
regulatory personnel providing oversight on the B-20 closure will be informed
within 24 hours, or as soon as possible, that UXO has been identified at B-20.
Depending
upon the type of UXO identified and the area it is found in, CSSA demolition
experts will present recommendations for appropriate disposal to the EPA and the
TNRCC. UXO can be removed for destruction at an appropriate facility,
destroyed at the site, or left in place. In most UXO situations, the best
option is destruction in place (EPA, 1993). UXO is hazardous waste, and
leaving it in place would result in potential continuing release of hazardous
waste. Removing UXO requires a great deal of precaution, specialized
equipment, very stable transport, and an appropriate receiving facility for
destruction. Risks are higher for the personnel handling the removal and
transport when compared to destroying the UXO in place. The latter option
usually can be performed safely and efficiently without high risk to human
health, especially as the B-20 site and CSSA demolition personnel have a history
of demolition without incident. Also, small items were generally disposed
of at B-20 (Table 2.1), indicating that proper demolition in place should
have little lasting effect on the environment.
If
no UXO is found at the surface, then the following activity of flagging safe
transit can be deleted from the remedial investigation. However, if
the UXO field team has any reasonable doubts as to the presence of potential UXO
because of surface anomalies or other field observations, the flagging of safe
transit routes will be performed.
After
prescreening for UXO has been completed and it has been decided that safe
transit corridors are necessary for health and safety precautions, safe transit
routes will be flagged by the UXO-qualified team from the known non-hazardous
zones (the roads surrounding the B-20 site) to those areas of surface and
subsurface sampling. Areas of safe transit will be identified in the field
as corridors of stakes with easily identified flagging or surveyor lines and
will also be marked on the site base map. The routes will avoid identified
UXO by at least 20 feet or more, based on professional experience. The
corridors will most likely north-south or east-west paths between the systematic
sample locations shown in Figure 4.1. Additional prescreening
traverses to the judgmental sample locations (drilling at craters and ponds)
will be performed.
Areas
where potential buried UXO are most likely to be found will be surveyed using a
magnetometer. As discussed in section
4.3.1, buried UXO are most probable in craters dug out for previous
demolition activities. Other areas have bedrock a few inches below the
surface, and it would be very difficult for UXO to be forced by trajectory
completely into the bedrock.
A
magnetometer measures the intensity of the earth's magnetic field in units of
gamma or tesla (Benson et al, 1982). Typical magnetometer readings are
from a sensor (fluxgate or proton) which undergoes changes in magnetic levels in
response to variations in the surrounding area. The signals are fed to an
output meter or recorder. A gradient can also be measured as a difference
between measurements at two different points. Factors affecting the
performance are magnetic properties of soil rock, e.g., iron content, mass of a
buried object, distance and depth to a buried object, and the amount of
permanent magnetism of an object. The amount of magnetic anomaly measured
by the magnetometer often varies widely over a traverse, and sometimes several
passes in different orientations are necessary to identify an anomaly.
When
magnetic properties of soil or rock are uniform, no local magnetic anomalies, or
fluctuations in gamma readings, are observed. When the magnetometer is
passed over any object or native material having nonuniform magnetic properties,
a response, or fluctuation in reading, is recorded. Nearby metal objects
cause difficulty in analyzing the data.
The
survey will be performed by the UXO-qualified team at each of fifteen
craters. Drilling is not anticipated at all craters, but the magnetometer
surveys will provide clearance for unexpected changes in the field program, if
necessary. As an abundance of scrap metal is in the vicinity of each
crater as well as across the site, the metal is expected to cause some
difficulty in interpreting the data. When possible, UXO experts will
direct removal of positively identified scrap metal at least 50 feet away from
each crater so as to remove the surface interference. Each crater survey
will consist of a minimum of six traverses, three in a north-south direction and
three in an east-west direction. As the craters are generally 20 to 40
feet wide, the traverses will be 30 to 50 feet in length. Surface
anomalies will be identified and removed if possible. The traverses may
then be repeated to screen surface interference and identify buried metal
objects. A metal detector may also be used to aid in identifying the
locations of subsurface objects within a few feet if possible.
Magnetic
anomalies will be recorded and computer generated on a map for each
crater. The results will be used in identifying appropriate drilling
locations at selected craters in areas where no anomalies were measured.
The
preliminary sample results (section
2.5) indicate the lack of explosives,
volatile organics, and semivolatile organics in surface soil. However, to
verify that no explosive compounds migrated over time into the subsurface, it is
necessary to drill for collection of subsurface soil samples. Surface soil
samples did not contain explosives, and the surface water and sediment samples,
which might have contained explosives from site runoff, also did not contain
explosives. Therefore, the most probable place of subsurface contamination
from explosive compounds is the subsurface in the area of the craters.
There
are fifteen craters identified in the field at B-20. One boring will be
drilled in close proximity to each of seven craters. Selected craters are
shown by soil boring locations on Figure 4.1. In addition, the six
craters in quadrant D are within 75 feet of each other and many cedar
trees. Therefore, two borings will be drilled near accessible craters in
quadrant D. To provide the best coverage, drilling will be attempted near
craters 10 and 11, and 14 and 15 (Figure 4.1). Other areas of
potential concern for subsurface contamination are the rocket motor standpipe
(quadrant B) and the soil mounds (quadrant H). One soil boring will be
drilled next to the rocket standpipe, and two borings near each end of the soil
mounds. A total of ten soil borings will be drilled.
Total
depth of each boring is based on demolition actions at the B-20 site.
According to CSSA SOPs (appendix B), pits typically were dug to hold
munitions and then were covered with about 6 to 8 feet of soil. The exact
depth of the pits is unknown, but might be about 12 to 15 feet BGS. Each
boring will be at least 20 feet deep, or will be drilled 5 to 10 feet into
undisturbed bedrock. Drilling will be preceded by reconnaissance in the
soil zone with a hand-held magnetometer to check for UXO.
Two
subsurface soil or rock samples will be collected from each boring. As
discussed in section 4.2,
these subsurface samples are considered judgmental samples for statistical
evaluation, because they will be collected from known hot spots which are judged
to be of sampling importance. Surface soil samples will also be collected
for analysis in selected craters as well as within 50 feet of those craters (section 4.2), providing three to four crater-specific soil samples for data
analysis and evaluation of chemical constituents. One of the subsurface
soil/rock samples will be collected at depth in soils associated with the pit,
or demolition activities, and one rock sample will be collected at the total
depth of drilling. The objective of the subsurface sample collection
depths is to test chemical constituents near the pit bottom or sides, and within
the bedrock to test for chemical migration. Subsurface soil samples will
be analyzed for metals and nitroaromatics/nitramines (explosives).
Ten
background subsurface soil/rock samples will also be collected at CSSA at
locations not recorded or suspected to have had contaminants at the surface or
subsurface. The background samples will be collected at 5 to 10 feet BGS
in bedrock. Analytical parameters will be metals, and the results will be
statistically evaluated for comparison to B-20 subsurface soil results.
Drilling
will be performed using a hollow stem auger rig capable of changing to air
coring so that both soil and rock cores can be collected within each soil
boring. It is anticipated that hollow stem augers will be used for the
first 1 to 15 feet within pit soil, and that air coring will be used after
undisturbed limestone is encountered. The augers will be of sufficient
diameter to allow sample collection.
It
is not anticipated that groundwater will be encountered during drilling of soil
borings, as the nearest groundwater well (CSSA well I) had a depth to water of
206 feet in October 1993. However, perched water zones may be encountered
after rainstorms. If water is encountered during drilling, the boring will
be left open for 24 hours to allow collection of that water. If not enough
water forms in the bottom of the boring to allow collection with a bailer, the
boring will be grouted to ground surface for abandonment as a boring.
Subsurface
soil samples will be collected in a split spoon sample through the hollow stem
augers, and the rock cores will be collected in a core barrel The soil
will be placed in clean glass jars with Teflon(R)-lined lids, labeled, and
placed into coolers to await transport to the laboratory. Rock cores will
be broken with a clean hammer to allow fit of the rock chips into glass
jars. The jars will be labeled and placed into a cooler.
Standard
chain-of-custody procedures will be followed with each shipped cooler. If
the coolers are shipped to a laboratory, the Federal Express airbill number will
be placed on each chain-of-custody form. If a courier or contractor
employee drives the coolers to a laboratory, records will be kept of each
shipment.
The
drilling equipment will be steam-cleaned prior to arriving on site.
Between borings, the drill rig, augers, and downhole sampling equipment will be
steam-cleaned. The sampling equipment will be cleaned before and after
each use with an Alconox wash, potable water rinse, and distilled water rinse,
and allowed to air dry.
In
accordance with EPA guidance on investigation-derived wastes (IDW), the cleaning
rinsate will be disposed of on the ground at the site unless field screening
indicates the presence of contaminants (EPA, 1991). Soil/rock cuttings
will be left at each drilling site, unless field screening indicates the need to
contain the cuttings for analysis. If contaminants are known at the
drilling site(s), the rinsate will be contained for analysis.
To
close the site, data must be collected that confirms the presence or absences of
contaminants as defined by specific media concentrations. The preliminary
surface soil concentrations were compared to 31 TAC 335, Subchapter S MSCs for
soil collected from 0 to 2 feet at industrial sites (Table 2.3).
Preliminary surface water results were compared most appropriately to state
freshwater concentration criteria found at 30 TAC 307 (Table 2.4). No
comparable criteria for sediments with regard to human health were found.
Analytical
results for the preliminary sampling event indicate the presence of metals in
surface soil, surface water, and sediments (section
2.5). One volatile organic compound and one semivolatile organic
compound were detected only in sediment samples. No explosive compounds
were detected in any of the tested media.
To
confirm the presence or absence of contaminants at the B-20 site, a statistical
sampling approach was defined to best address all media of concern with a valid
but limited number of samples and corresponding analyses (section
4.2). The verification sampling and analyses will thus be
concerned with surface soils, surface water, and sediments.
Surface
soil samples will be collected as described in section
4.2. To collect a representative number of surface soils samples,
samples will be collected in a systematic statistical sampling grid of 250 x 250
feet. Judgmental samples will also be collected at and within 50 feet of
selected craters. Where the grid and craters intersect, only one (rather
than two) samples will be collected. Up to 40 surface soil samples will be
taken and analyzed for metals. As no explosives were detected in surface
soil samples collected during the preliminary sampling event, one-half of the
remedial investigation surface soil samples will be analyzed for explosives for
confirmation of previous results.
Ten
background surface soil samples will be collected across CSSA to represent the
three soil types found at B-20. Analytical parameters will be metals, and
the background results will be statistically evaluated and compared to B-20
surface soil sample results from the remedial investigation.
Surface
water samples will be collected from those ponds or streams not dry during
sampling. It is anticipated that the ephemeral stream at the site will not
contain surface water most of the year, but that the quadrant F pond and
possibly crater 8 will contain enough surface water to sample. The
livestock pond will not be resampled, as detected metal levels were below
comparison criteria. The samples will be collected from clean surface
water samplers so as to not include sediments. The samples will be
analyzed for metals, and one sample will be analyzed for explosives. As
the runoff channels begin at the southern boundary of the site and end at the
pond, appropriate background surface water sampling locations are not available,
e.g., other streams and ponds at CSSA are in different soil types and do not
drain into the B-20 area.
Sediment
samples will be collected along the ephemeral stream (Figure 4.1).
At least seven samples will be collected in approximately 400-foot
intervals. Sediments will be collected with a clamshell-type sampler after
collection of surface water samples. As with surface water, background
samples appropriate to this stream are not available. The sediment samples
will be analyzed for volatile organics, semivolatile organics, and metals.
Three of these samples will be analyzed for explosives for verification
purposes.
Because
explosive compounds were not detected in any of the media tested during
preliminary sampling, it does not appear that contaminants of concern have
migrated into the subsurface. As depth to groundwater is more than 200
feet BGS, groundwater will not be tested during the Phase I remedial
investigation. Should data evaluation indicate the need for groundwater
sampling, appropriate actions based upon verified remedial investigation phase I
data will be discussed and recommended to the EPA and TNRCC.
The
analytical results will be presented in Level 3 format, and data validation will
be performed on all remedial investigation samples. The results will be
presented in the remedial investigation report.
Analytical
techniques will be taken from Test Methods for Evaluating Solid Waste,
U.S. Environmental Protection Agency, SW-846, November 1986 (EPA, 1986b).
Sampling techniques will be taken from TEGD (EPA, 1986a) and the Compendium
of Superfund Field Operations Methods (EPA, 1987a).
Laboratory
analytical methods are summarized in Table 4.2. These methods are
specified for water, soil, and sediment samples and are based on results of the
preliminary sampling and analysis. Surface and subsurface soil samples
will be analyzed for explosives, metals, and geotechnical parameters.
Surface water samples will be analyzed for explosives, metals, and general water
quality parameters. Sediment samples will be analyzed for volatile
organics, semivolatile organics, explosives, and metals.
Table
4.3 and Table 4.4 list the appropriate containers, preservatives, and
holding times for soil and water, respectively.
A
summary of the number of soil samples and associated QA/QC samples is shown on Table
4.5. The samples are listed by surface soil, subsurface soil, and
sediment samples. Background samples and QA/QC samples such as trip blanks
and duplicates are included in the total sample count per analysis. Table
4.6 lists the number of surface water samples and associated QA/QC samples.
The
data collected from the field activities (section
4.3) and laboratory analyses will be evaluated to characterize any
release of waste constituents at the B-20 site. Based on the proposed
field actions, the anticipated data will result from physical analyses such as
magnetometer survey, borehole logging, and field observation, and from chemical
analyses of samples collected at the site from different environmental
media. All chemical data will be validated using the procedures described
in the QAPP (Appendix C) to ensure that the DQOs were achieved. The
analytical data collected during the remedial investigation may also be used for
performing the baseline RA, CMS, and in corrective action design and
implementation. The following is a description of data evaluation and
reporting methods that will be used in presenting the results of the closure
investigation.
The
proposed magnetometer survey will generate readings proportional to the
intensity of earth's magnetic field. The survey data will consist of
survey point location and the magnetometer reading. The data will be
evaluated to determine indication of the presence of metal residues at the B-20
area.
The
magnetometer survey data will be presented in tabular format. The data
will also be plotted in graphical form to create contours of magnetometer
readings. The magnetometer contours will be analyzed to locate
"signature readings" for the presence of metal residues indicated by
elevated magnetometer readings. The findings of the data evaluation will
be discussed in the remedial investigation report.
The
analytical data will be generated from the proposed surface soil sampling
activities. The data will include sample location, analytical method,
analytes, concentration of analytes found, and detection limits. In
addition, analytical QA/QC data will be generated. The QA/QC data will be
used to validate the sample results in accordance with the procedures listed in
the QAPP (Appendix C).
The
analytical data will be presented in tabular form. The data will be
evaluated to determine the nature, magnitude and extent of contaminants, if any,
found in the surface soil samples. If sufficient number of samples contain
one or more contaminants significantly above background levels indicating
significant areal coverage of contamination, the analytical data will also be
presented in the form of contoured analyte concentrations. These contours
will be evaluated to determine contamination extents, waste volume and any
migration trends. The results of the data evaluation will be summarized in
the closure investigation report.
The
analytical data generated from the proposed subsurface soil sampling activities
will include sample location, analytical method, analytes, concentration of
analytes found, and detection limits. Also, a log of soil type and
conditions will be recorded in the field during drilling of soil borings.
Analytical QA/QC data will be generated and used in data validation as described
in section 4.4.2.
The
analytical data will be presented in tabular form. Based on the analytical
results, the data may also be presented in a graphical form as data flags at the
sample locations. The subsurface soil samples will be collected from
suspected "hot spots" (craters). The data will be evaluated to
determine the nature, magnitude and vertical extent of contaminants in the
subsurface soil samples. In addition, soil boring logs will be prepared to
define the vertical profile of the soil types and conditions at the borehole
locations. These logs will be evaluated to determine subsurface
conditions. The results of the data evaluation will be summarized in the
closure investigation report.
The
analytical data for the proposed sediment sampling activities will include
sample location, analytical method, analytes, concentration of analytes found,
and detection limits. In addition, analytical QA/QC data will be generated
and used in data validation as described in section
4.4.2.
The
analytical data will be presented in tabular form. Based on the analytical
results, the data may also be presented in a graphical form as data flags at the
sample locations. The data will be evaluated to determine the nature,
magnitude and vertical extent of contaminants in the sediment samples. The
results of the data evaluation will be summarized in the closure investigation
report.
The
analytical data for the proposed surface water sampling activities will include
sample location, analytical method, analytes, concentration of analytes found,
and detection limits. Analytical QA/QC data will be generated and used in
data validation as described in section
4.4.2.
The
surface water samples analytical data evaluation and reporting will be similar
to those of the sediment samples (section
4.4.4)
In
addition to the data types discussed in section
4.4.1 through section 4.4.5,
other data may be obtained during the remedial investigation activities.
These data my include visual observations, health and safety monitoring, and
historic operating or monitoring records. These data will be included as
appropriate in the remedial investigation report.
After
completing the remedial investigation, CSSA's contractor will prepare a remedial
investigation report. However, should additional (phase II) data be
required to complete the investigation, an interim technical report will be
prepared for submittal, and the final remedial investigation report be prepared
after all data has been collected, analyzed, and evaluated.
The
remedial investigation report will include descriptions of all field activities,
deviations from this closure plan, survey, drilling, and sampling techniques,
analytical procedures, and analytical results. A data validation report
will also be prepared for submittal. The report conclusion will indicate
the characterization of the site with respect to environmental media, chemical
constituents, background analysis, and the presence or absence of hazardous
waste at the site.
CSSA
will submit the final report to the EPA and TNRCC. EPA and TNRCC will
review the report for approval or recommendations for further investigation.
