[Home]
Final
SWMU B-5 RCRA Facility Investigation/Closure Report
Section 2 - Field Investigation
As outlined in the Environmental Encyclopedia site-specific work plan
(Volume 1-2, SWMU B-5), the objectives of the site assessment were
to conduct a geophysical survey and collect surface soil samples from SWMU B-5,
with the goal of closing the site under RRS1, if appropriate.
All field activities conducted were in accordance with the field sampling
and analysis plan in the CSSA Environmental Encyclopedia
(Volume
1-4, Field Sampling Plan).
During March 1996, a geophysical survey, an engineering survey of geophysical gridpoints and metal debris within the site area, and collection of three
surface soil samples were conducted at the site.
However, the analytical data associated with the surface soil samples
were rejected by the EPA in 1999 due to questionable practices by ITS
Laboratories. Soil sampling was repeated in March 2000, in accordance with
the SWMU B-5 Rework Work Plan (Volume 1-2).
An electromagnetic geophysical survey was conducted at
SWMU
B-5 in March 1996.
Prior
to collecting EM data, a grid system was established at SWMU B-5 which
encompassed the areas of suspected ground disturbance.
These grids consisted of staked locations separated by intervals ranging
from 25 to 100 feet, depending on the size of the area and the amount of
obstructions, if any.
Figure
B5-4 illustrates the layout of the geophysical survey grid located at
SWMU
B-5, which included an approximate 180 feet by 300 feet area.
EM data were collected at 2-foot intervals along transects that were separated
by 20 to 50 feet using the established geophysical survey grid.
EM measurements were taken using a Geonics EM-31-DL ground conductivity
meter, and recorded with a Polycorder data logger.
The conductivity meter consists of transmitter and receiver coils that
are separated by 12 feet. The
instrument has a nominal depth of penetration of approximately 16 feet when
operated in the vertical-dipole mode. The
instrument measures both quadrature- and in-phase components of an induced
magnetic field. The quadrature-phase
component is a measure of apparent ground conductivity while the in-phase
component is more sensitive to the presence of ferromagnetic metal.
A lateral variation in apparent ground conductivity indicates a lateral
change in subsurface physical properties (i.e., related to degree of
disturbance). Apparent ground
conductivity is measured with a precision of approximately ±2 percent of the
full-scale meter reading which corresponds to approximately 2 milliSiemens per
meter (mS/m). The in-phase
component of the EM-31 is the response of the secondary to primary magnetic
field measured in units of parts per thousand (ppt).
The primary magnetic field is due to the current source from the EM-31.
The secondary magnetic field is due to induced currents within conductive
material in the subsurface.
Data were collected by setting the instrument to record in an automatic vertical
dipole mode. Readings were taken at
0.5 second intervals which corresponded to a reading every 2 feet along a given
transect. Both apparent ground
conductivity (i.e., quadrature phase) and in-phase data were recorded.
The operator aligned himself along a transect and, with the instrument
parallel to the transect, paced between marked or staked stations separated by
50 feet. The variation in transect footage was related to the size of
the site and the number of obstructions.
The EM-31 survey was completed according to the procedures described in
Volume
1-4, Sampling and Analysis Plan, Section 1.1.2.
Prior to the survey, a site near the
SWMU
that was determined to be free of disturbances and anomalies was selected
and marked to perform background checks and calibration.
The background checks were also performed after the survey.
All calibration and before and after background readings were recorded in
the field logbook.
During each field day, data were transferred from the data logger to computer diskettes. The data were processed using DAT31 software (Geonics, LTD) and contoured using Surfer software. For EM data that was not collected using the data logger, values were recorded on a log sheet, manually entered into a computer file, and contoured using Surfer software. Contour maps for both apparent conductivity and in-phase data were created for each site.
Soil gas samples were not collected in association with the investigation of SWMU B-5.
Three surface soil
samples were collected during March 1996. The
three sample locations were located in the central and western portions of the
site area and strategically placed near surface debris located in the site area
(Figure
B5-4).
During March 2000, the sample locations were
resampled to replace invalid ITS data submitted for the original samples.
The results section of this report only includes data from the Rework
sampling event. Surface soil
samples from SWMU B-5 consisted of materials representative of Krum Complex
soils. In general, the soils were a
calcareous clay material. At the
time of sampling, no discernable evidence of contamination was noted in
association with surface soils throughout the SWMU B-5 area.
Based on prior
identification of the site as a former disposal area for small arms ammunition
brass, COCs included VOCs, metals, and explosives.
Metals (arsenic, barium, cadmium, chromium, copper, lead, mercury,
nickel, and zinc) were included due to the potential metallic nature of the
waste. Ammunition may include
explosives residue therefore, an analysis for explosives was conducted.
VOC analyses were included in the analytical program to detect typical
contaminants associated with disposal areas.
Samples collected
at SWMU B-5 were submitted to three laboratories.
VOC samples were analyzed by Agriculture and Priority Pollutants
Laboratories, Inc., explosives samples were analyzed by DataChem Laboratories,
Inc., and metals samples were analyzed by O’Brien & Gere Laboratories,
Inc. A total of nine environmental
samples, one field duplicate sample, one matrix spike sample, and one matrix
spike duplicate sample were submitted for analyses.
All sampling points
were surveyed by Parsons ES using a Trimble Asset-grade GPS with 1-meter
accuracy. Surveying methodology is
described in the Amendment to the Field Sampling Plan
(Parsons ES, 2001b). All
sample locations and analytical data will be incorporated into the CSSA GIS
database after it has been approved by both CSSA and AFCEE.
Subsurface soil
samples were not collected in association with the investigation of SWMU B-5.
Groundwater samples were not collected during the investigation of SWMU B-5.
The survey indicated two geophysical anomalies associated with metal beams and a roll of barbed wire fence present at SWMU B-5. The geophysical surveys revealed no evidence of subsurface anomalies related to past waste disposal activities. Away from the surface metal, there was little variation in the data that were recorded during the EM survey. The resulting survey of the SWMU was interpreted as homogenous and consistent soil and bedrock profiles (Figure B5-5 and Figure B5-6). In-phase readings during the EM survey ranged from a minimum of -0.75 ppt, to a maximum of 3.0 ppt. Quadrature-phase readings ranged from a low of 24 mS/m, to a high of 33 mS/m.
No soil gas samples were obtained during the investigation of SWMU B-5.
Analytical testing
results are presented in Appendix A.
Table B5-1 includes tabulated
analytical results for detected COCs. RRS1
criteria for VOCs are the laboratory RLs. The
RRS1 criteria for metals are the background levels.
Background metals levels were statistically calculated for CSSA soils and
the Glen Rose Limestone, and are reported in the
Second
Revision to the Evaluation of Background Metals Concentrations in Soil Types
(Parsons, February 2002). As shown
in Table B5-1, no VOCs and no metals were detected over RRS1 criteria.
No subsurface soil
samples were obtained during the investigation of SWMU B-5.
Analytical results obtained for surface soil samples support the decision
to exclude subsurface soils from the investigation program.
No groundwater
samples were obtained during the investigation of SWMU B-5. Analytical results obtained for surface soil samples support the decision
to exclude groundwater from the investigation program.