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SWMU Building 43 RCRA Facility Investigation Report
Section 2 - Closure Activities
Miscellaneous solid waste and ammunition were burned at SWMU Building 43. The three-walled concrete-block building was used as a makeshift ammunition demolition facility, and it is presently inactive. Metal debris, fuses, shotgun shells, and casings are scattered across the ground surface of the site. In an effort to characterize the site and determine its readiness for RRS1 closure, a soil gas survey was performed in 1995 and PCE was detected in one soil gas sample.
As outlined in the Environmental Encyclopedia site-specific work plan (Volume 1-2, SWMU Building 43), the project RFI requirements were to conduct a geophysical survey drill six soil borings and to collect soil samples for VOCs, SVOCs, metals, and explosives analyses. Dioxins and furans analyses were conducted from wipe samples of the steel burn box. All field activities conducted were in accordance with the Field Sampling and Analysis Plan (Volume 1-5, Field Sampling Plan, Quality Assurance Project Plan, and RL53 Addendum).
Electromagnetic (EM) and ground penetrating radar (GPR) geophysical surveys were conducted at SWMU Building 43 on March 13 and April 2, 1996. Prior to collecting EM or GPR data, a grid system was established which encompassed the areas of suspected ground disturbance. The grid at SWMU Building 43 measured 110 feet by 80 feet.
EM data were collected at 2-foot intervals along transects that were separated by 10 feet using the established geophysical survey grid. EM measurements were taken using a Geonics EM31-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 two 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 10 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 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.
On August 23, 1996, a third round of soil gas samples were collected at SWMU Building 43. A total of seven samples were collected from seven locations and analyzed for benzene, toluene, ethylbenzene, total xylenes, cis-1,2-DCE, TCE, 1,1,1-TCA, and PCE. These soil gas sample locations, as well as sample locations from 1995, are shown on Figure Building 43-4. The August 1996 samples included locations A,0; A,1; A,2; B,0; B,1; B,2; and #7. Because bedrock or refusal was generally encountered at a depth of three feet, depth profiles could not be performed. Soil gas samples were collected at the bedrock soil interface or at the depth of refusal.
Samples were collected by manually driving a decontaminated ¾-inch stainless steel hollow sampling rod to the selected depth with a pneumatic hammer. The sampling rod was then backed a few inches out of the ground allowing the detachable point to drop off the sampling probe and exposing a void space of the formation. Soil vapors were then pulled from the soil through the probe into a Tedlar bag using a portable vacuum pump. The soil formation around the sample rod was purged for at least three probe volumes prior to sample collection.
The samples were then transported to the field gas chromatograph (GC) temporarily located at CSSA for analysis. Samples were analyzed within four hours of collection with an HNu model 321 GC equipped with an electron-capture detector (ECD) and a photo-ionization detector (PID) with a 10.2 eV light source. A Spectra-Physics model 4400 dual-channel integrator was used to plot the chromatograms, to measure the size of the peaks, and to compute compound concentrations.
2.1.3 Unexploded Ordnance Sweep
On August 28, 1997, an unexploded ordnance (UXO) sweep was performed by UXO Specialists from UXB International, Ashburn, Virginia. The UXO specialists traversed the site in a systematic manner to visually identify UXO on the surface. In addition, they used Schonstedt magnetometers to assist in identification of metal at or near the surface.
2.1.4 Surface and Subsurface Soil Samples
Six soil borings were advanced between February 29 and March 1, 2000 to characterize surface and subsurface soils at SWMU Building 43. The locations of the borings are shown in Figure Building 43-4. Subsurface soil samples were collected with a split-spoon sampler and hollow-stem auger until advancement refusal was encountered. Once refusal was encountered, rock samples were obtained by air core using a decontaminated core barrel. Soil/rock samples were collected continuously to identify soil/rock type and to identify evidence of contamination. Samples were screened using a PID as an additional measure to identify evidence of contamination. Soil boring depths ranged from 10 to 20 feet bgs. Soil boring logs are included in Appendix B.
For each sampling location at SWMU Building 43, a sample was collected from 0.5 to 1.0 feet bgs, and two additional samples were collected at different depths. Samples obtained from depths of 0.5 to 1 feet bgs, with the exception of the sample from BLDG43-SB02, are representative of Tarrant Association soils. Samples collected at greater depths within the borings consist of materials representative of the Upper Glen Rose Limestone. Samples of the Upper Glen Rose Limestone from BLDG43-SB01 were collected at 9.5 to 10 feet bgs and 12.5 to 13 feet bgs. In addition, a field duplicate, a matrix spike (MS), and a matrix spike duplicate (MSD) were collected for BLDG43-SB01 at 0.5 to 1 feet bgs. Samples of the Upper Glen Rose Limestone were collected at 0.5 to 1.0, 8.5 to 9.0, and 12.5 to 13 feet bgs within BLDG43-SB02, 5.0 to 5.5 and 9.5 to 10.0 feet bgs within BLDG43-SB03, 10 to 10.5 and 14.5 to 15.0 feet bgs within BLDG43-SB04, 5 to 5.5 and 12.5 to 13 feet bgs within BLDG43-SB05, and 9.5 to 10 and 19.5 to 20 feet within BLDG43-SB06. Samples from all of the borings were collected on March 1, 2000 except those from BLDG43-SB06, which were collected on February 29, 2000.
A total of 18 environmental samples, two field duplicates, three equipment blanks, four trip blanks, two MSs and two MSDs were submitted for analyses. All samples were analyzed for VOCs (SW-8260B); barium, chromium, copper, nickel, and zinc (SW-6010B); arsenic (SW-7060A); cadmium (SW-7131A); lead (SW-7421); mercury (SW-7471A); and explosives (SW-8330). Three surface soil samples were also analyzed for SVOCs by method SW-8270C. APPL Laboratory in Fresno, California conducted all analyses except explosives analysis, which was conducted by DataChem Laboratory in Salt Lake City, Utah.
Decontamination procedures, as well as sample collection, preparation, handling, and shipping protocols, are described in the Field Sampling and Analysis Plan (Volume 1-5, Field Sampling Plan, Quality Assurance Project Plan). Quality Assurance/Quality Control (QA/QC) samples were collected as described in the AFCEE QAPP (Volume 1-4, Quality Assurance Project Plan). Sampling locations were recorded by Parsons ES with a Trimble Asset-grade GPS. Surveying methodology is described in the Amendment to the Field Sampling Plan (Parsons ES, 2001b). All sample locations and analytical data have been incorporated into the CSSA GIS database.
The soils at SWMU Building 43 are gently undulating Tarrant Association. Generally, the soils in the first foot bgs at SWMU Building 43 were silty, plastic, and brown with pebbles and cobbles. A hard mudstone was encountered between 3 and 10 feet bgs. The mudstone was dry, white to pale brown, and contained numerous cavities. No odor was detected in the mudstone, and no visible contamination was noted during the sampling efforts. No groundwater was detected during the soil boring drilling.
In accordance with the approved work plan, groundwater samples were to be collected if groundwater was encountered during soil boring drilling. Since groundwater was not encountered, no groundwater samples were collected.
One surface wipe sample was collected on March 21, 2001, from SWMU Building 43 for this investigation. The wipe sample was collected from an area blackened with soot inside the burn box. The wipe sample was sent to Triangle Laboratories in Durham, North Carolina and analyzed for dioxins and furans using EPA test method 8290. All sample analytical data will be incorporated into the CSSA GIS, after it has been approved by AFCEE and CSSA.
The survey indicated one geophysical anomaly associated with the structure Building 43 itself and is not related to suspected waste management activities. The geophysical surveys revealed no evidence of subsurface anomalies related to past waste disposal activities. There was little variation in the data that were recorded during the EM survey, which can be interpreted as homogenous and consistent soil and bedrock profiles throughout the SWMU (Figure Building 43-5 and Figure Building 43-6). In-phase readings during the EM survey ranged from a minimum of 0.8 ppt, to a maximum of 1.8 ppt. Quadrature-phase readings ranged from a low of 16 mS/m, to a high of 20 mS/m.
PCE and TCE were the only target compounds detected in soil gas samples from this site. Results are provided in Table Building 43-2 and sample locations are shown in Figure Building 43-4. PCE occurred at concentrations of 0.04 to 1.0 μg/L with the highest concentration occurring at location B,2. This point is the only location where TCE was detected; the concentration was 0.04 μg/L. Since concentrations within the SWMU Building 43 boundary are lower, the occurrence of PCE at location B,2 is consistent with the previous survey that suggested that SWMU O-1 or SWMU B-3 could be the source of the PCE contamination in the area (Parsons ES, 1996d). A definitive site-specific source of PCE does not appear to be present at Building 43 because a distinct soil gas source pattern was not detected.
2.2.3 Unexploded Ordnance Sweep
A small amount of ammunition-related debris was found and manually removed during the UXO sweep; however, no UXO was found. Several small, spent caliber cartridges, projectiles, and a number of small, spent fuses were found.
2.2.4 Surface and Subsurface Soil Samples
Elevated levels of metals were detected in five of the six surface soil samples collected at the site. All other analytical results slightly exceed or are below RRS1 levels. No SVOCs or explosives were detected in any of the samples. Table Building 43-3 presents a summary of the detected constituents. A complete list of analytical results is provided in Appendix A.
2.2.4.1 Volatile Organic Compounds
Methylene chloride was detected above the RL in fourteen of the twenty soil samples collected at the site. Concentrations ranged from 0.0054 to 0.1872 milligrams per kilograms (mg/kg). The RL for this common laboratory contaminant was 0.005 mg/kg. Methylene chloride is not a transformation product of any suspected contaminants at the site, and there is no historical or other reason to believe that the constituent should be associated with the site; therefore, it is believed to be derived from lab contamination.
Reported values for dichlorodifluoromethane, ethylbenzene, and toluene exceeded RLs in sample BLDG43-SB02 (8.5 to 9 feet). Dichlorofluoromethane, ethylbenzene, and toluene concentrations in this sample were 0.0176 mg/kg, 0.0089 mg/kg, and 0.0068 mg/kg, respectively. The RLs for these constituents are 0.005 mg/kg, 0.003 mg/kg and 0.005 mg/kg, respectively. Dichlorodifluoromethane is a coolant, which may have been associated with laboratory conditions during sample analysis. Although ethylbenzene and toluene may be associated with possible fuel use at the site, the concentrations detected are very low and in only one sample.
All other VOC concentrations identified within samples collected at SWMU Building 43 were below applicable RRS1 standards. None of the VOC concentrations associated with samples collected from this site exceeded the RRS2 closure standards.
The highest metals levels were detected in the surface soil sample collected at BLDG43-SB05. This boring was the only boring situated within the area covered with scattered metal debris. Metals concentrations in surface soil which significantly exceeded background included arsenic, cadmium, copper, lead, and zinc. Very high levels were also found in surface soil at BLDG43-SB06. The lowest metals concentrations in surface soil were at BLDG43-SB03, where only copper was detected above the RRS1 criteria. In subsurface soil/rock samples, there were two slight exceedances: one each of barium and nickel.
Arsenic exceeded the RRS1 level at only one location: BLDG43-SB05 (0.5-1.0 ft bgs). The concentration at this location was 210 mg/kg, which greatly exceeds the background concentration of 19.6 mg/kg.
Barium exceeded background in two surface soil samples, a field duplicate of a surface soil sample and one subsurface soil sample. In the surface soil samples, the concentrations above background levels were 252.85 mg/kg (BLDG43-SB05), 215.26 mg/kg (field duplicate of BLDG43-SB06) and 191.32 mg/kg (BLDG43-SB06). The background level in surface soil is 186 mg/kg. In one subsurface soil sample, BLDG43-SB06 9.5-10.0, the concentration was 13.06 mg/kg, in which the background level is 10 mg/kg.
Cadmium exceeded background levels in two of the six surface soil samples and in a field duplicate. In surface soil, above-background levels reported were 16.89 mg/kg (BLDG43-SB05), 22.0 mg/kg (BLDG43-SB06) and 22.03 mg/kg (field duplicate of BLDG43-SB06). The background concentration for CSSA soils is 3.0 mg/kg.
Chromium exceeded background in one surface soil sample from BLDG43-SB05, at a concentration of 67.7 mg/kg. This concentration is only slightly above the background of 40.2 mg/kg.
In surface soil, copper concentrations exceeded background in every surface soil sample, and concentrations ranged from 71.32 mg/kg (BLDG43-SB03) to 24,362 mg/kg (BLDG43-SB05). None of the subsurface samples contained copper above the background level of 23.2 mg/kg.
Mercury slightly exceeded background in the surface soil sample from BLDG43-SB06 and its field duplicate, at a concentration of 0.87 mg/kg and 0.82 mg/kg, respectively. These concentrations are only slightly above the background of 0.77 mg/kg.
Lead exceeded background levels in five of the six surface soil samples. In surface soil, above-background levels ranged from 224.77 mg/kg (BLDG43-SB01) to 2,208.02 mg/kg (BLDG43-SB05). The background concentration for soils is 84.5 mg/kg. None of the subsurface samples contained lead above background levels.
Nickel exceeded background in one surface soil sample and one subsurface soil sample, BLDG43-SB05 and BLDG43-SB06 (19.5-20 ft bgs). The concentrations detected in these samples were 60.0 mg/kg and 8.25 mg/kg, respectively. The background levels for surface soils and subsurface soils are 35.5 mg/kg and 6.8 mg/kg, respectively.
Finally, zinc exceeded background levels in five of the six surface soil samples. In surface soil, above-background levels ranged from 154.32 mg/kg (BLDG43-SB01) to 10,922.19 mg/kg (BLDG43-SB05). The background concentration for soils is 73.2 mg/kg. None of the subsurface samples contained zinc above background levels.
In accordance with the approved work plan, groundwater samples were not collected in association with the investigation conducted for SWMU Building 43.
All dioxins and furans in the samples collected at SWMU Building 43 were below RLs; therefore, RRS1 criteria were met. A very low concentration pf 2,3,7,8-TCDD was well below the RL of 0.006 ng. In addition, total TCDFs were detected, also below its RL of 0.03 ng.