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SWMU B-33 RCRA Facility Investigation Report
Section 2 - Field Investigations
As outlined in the Environmental Encyclopedia site-specific work plans (Volume 1-2, RL17; Volume 1-2, RL33 Addendum; and Volume 1-2, RL17 and RL33 Amendment for Data Quality Rework), work conducted as part of the RFI included a geophysical survey, surface and subsurface soil and rock sampling, and waste excavation and disposal. Soil and rock samples were initially collected in 1996 and 1997. However, the analytical data associated with the samples were rejected by the EPA in 1999 due to fraudulent laboratory practices. Surface and subsurface sampling were repeated in 2000.
Procedures used for sample collection, preparation, handling, and shipping, as well as decontamination, are described in the Field Sampling and Analysis Plan (Volume 1-4, Field Sampling Plan, Quality Assurance Project Plan, and RL33 Addendum) and the Waste Handling Plan (Volume 1-5, RL33 Addendum). QA and QC samples were collected as described in the AFCEE QAPP (Volume 1-4, Quality Assurance Project Plan). Sampling locations were recorded with a Trimble Asset-grade GPS by Parsons. Surveying methodology is described in the Amendment to the Field Sampling Plan (Parsons, 2001b). All sample locations and analytical data will be incorporated into the CSSA GIS database.
Electromagnetic and ground penetrating radar geophysical surveys were conducted at SWMU B-33 in March 1996. Prior to collecting EM or GPR data, a grid system was established at each site 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. The grid system and spacing used are shown on individual site base maps. Figure B33-4 illustrates the layout of the geophysical survey grid located at SWMU B-33.
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 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 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 20 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, an area
near SWMU B-33 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. The geophysical survey grid was 295 feet long (northeast to southwest) and 40 feet wide with 20-foot spacing (Figure B33-4).
2.1.2 Waste Excavation and Disposal
In July 1997, the underground water line at Building 45 was temporarily diverted and the shot and lead-contaminated sand was excavated, stockpiled, and then later stabilized and removed from SWMU B‑33. Since the specific location of this material was not known, four test pits were dug to find it. Field observations confirmed the presence of the lead shot material within the pipe bedding material. Approximately 180 cubic yards of bedding and fill material were excavated and replaced with clean material. All soils were successfully treated by solidification with Portland cement to non-hazardous Class 2 levels. The treated soils were then transported for disposal to Covel Gardens Landfill in San Antonio, Texas in accordance with the Waste Analysis Plan (Volume 1-5, RL33 Addendum) and applicable regulations. The water line was returned to service upon completion of field activities.
While the excavation was open and the water line diverted, four confirmation subsurface soil samples (B33-T1, B33-T2, B33-T3 and B33-T4) were collected and analyzed for metals in order to determine if all shot and lead-contaminated soils had been removed from all accessible areas. However, the analyses of the subsurface samples collected in 1997 were performed by ITS Laboratories, Inc. and deemed invalid by the EPA in 1999. Replacement of these test pit samples was not proposed in the Amendment for Data Quality Rework so that the active water line would not be damaged; instead, collection of subsurface soil boring samples was planned, as described in Section 2.1.4. It is estimated that approximately 2 to 3 cubic yards of the shot and lead contaminated sand is still in place near the foundation of Building 45. Utility lines prevented the full excavation of all material.
Based on the results of the initial geophysical survey, three surface soil samples (B33-SS01, B33-SS02, and B33-SS03) were collected in March 1996 and analyzed for explosives and metals. However, the analyses of these surface samples collected in 1996 were performed by ITS Laboratories, Inc. and deemed invalid by the EPA in 1999. A Work Plan Amendment was subsequently created to replace the invalid laboratory data (RL17 Work Plan Amendment for Data Quality Rework at SWMU B-33). At the time of the field investigation conducted in March 2000, the pipe bedding had been excavated and disposed offsite. Therefore, additional surface soil sampling was not performed. The material representative of surface soils which was formerly sampled was removed from the site in July 1997 and disposed offsite. Therefore, no representative surface soil remained onsite in March 2000.
Based on the results of the initial geophysical survey and analytical results from surface soil samples, three soil borings (B33-SB01, B33-SB02, and B33-SB03) were completed in May 1997 at SWMU B-33 to assess the extent of contamination. Soil samples from borings B33-SB01, B33-SB02, and B33-SB03 were collected and analyzed for explosives and metals in order to evaluate potential leachate from the pipe bedding.
In March 2000, three additional soil borings (RW-B33-SB01, RW-B33-SB02 and RW-B33-SB03) were completed in the approximate locations of the soil borings installed in 1996 in order to replace the analytical data generated by ITS Laboratories. Borings were drilled immediately adjacent to the water line trench. Two samples were collected from each replacement boring, one at the vertical extent of the excavation and one at the total boring depth. Each subsurface soil sample was analyzed for explosives using EPA method SW-8330 and metals using methods SW-6010B (barium, chromium, copper, nickel, and zinc), SW-7060A (arsenic), SW-7131A (cadmium), SW-7421 (lead), and SW-7471A (mercury). Metals analyses were conducted by O’Brien & Gere Laboratory in Syracuse, New York, and explosives analyses were performed by DataChem Laboratory in Salt Lake City, Utah. Figure B33-4 shows the locations for replacement soil borings collected at SWMU B-33.
Soil boring logs from the borings advanced in 1997 are presented in Appendix B. As per the Re-Work Plan (RL17 Work Plan Amendment for Data Quality Rework at SWMU B-33), new borings were not to be recorded, but the differences between the 1997 and 2000 borings were to be noted. At the time of original sampling, lead shot material was observed. However, during data quality rework activities, no discernable evidence of contamination was noted. Excavation of surface soils in July 1997 removed the bedding material encountered during completion of the May 1997 borings.
In accordance with the approved work plan, a soil gas survey was not performed in association with the current investigation conducted for SWMU B-33.
In accordance with the approved work plan, groundwater samples were not collected in association with the current investigation conducted for SWMU B-33. Groundwater was not encountered in the soil borings drilled at the site.
A geophysical survey was conducted at SWMU B-33 in March 1996 as part of initial site investigations. The geophysical survey detected four anomalies at the site. None of the geophysical anomalies indicated subsurface disturbance or possible buried waste. Two anomalies were associated with buildings, a third with the railroad tracks, and the fourth with the 6-inch metal water supply line, which connects to the poly-vinyl chloride (PVC) line leading from Building 45 (Figure B33-5).
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 SWMU B-33 (Figure B33-5 and Figure B33-6). In-phase readings during the EM survey ranged from a minimum of 5 parts per thousand (ppt), to a maximum of 50 ppt. Quadrature-phase readings ranged from a low of 10 milliSiemens per meter (mS/m), to in excess of 125 mS/m.
2.2.2 Waste Excavation and Disposal
Approximately 180 cubic yards of lead-contaminated sand was excavated, stockpiled, and then later stabilized and removed from SWMU B-33. All removed soils were successfully treated by solidification with Portland cement to non-hazardous Class 2 levels. The treated soils were then transported and disposed at Waste Management’s Covel Gardens facility in accordance with the Waste Analysis Plan (Volume 1-5, RL33 Addendum) and applicable regulations.
In accordance with the approved work plan, additional surface soil samples were not collected in association with the investigation conducted for SWMU B-33. At the time of the field actions conducted in March 2000, the pipe bedding had been excavated and disposed offsite. The material representative of surface soils which was formerly sampled was removed from the site in July 1997 and disposed offsite. Therefore, no representative surface soil remained onsite in March 2000 to be sampled.
Barium, chromium, zinc, cadmium, and lead concentrations slightly exceeded RRS1 criteria in one subsurface rock sample, and nickel slightly exceeded background in two samples. However, all concentrations were below Texas-specific median background concentration (30 TAC 350.51(m)), except one nickel result which exceeded the Texas background of 10 mg/kg by only 0.1 mg/kg. The detected concentrations are summarized in Table B33-1, which also presents the RRS1 comparison concentrations. Explosives were not detected in any of the samples. The analytical data are presented in Appendix A.
Barium, chromium, nickel, zinc, cadmium, and lead were detected in the Glen Rose Limestone sample collected from 4.0 ft. to 4.5 ft. bgs in soil boring RW-B33-SB01 at concentrations exceeding applicable RRS1 criteria (i.e., the calculated background levels for the Glen Rose Limestone). According to the boring log for B33-SB01 (Appendix B), the weathered limestone and marl that was recovered from 4.0 to 4.5 ft. bgs would be more comparable in structure and color to the soil types at the site than to the Glen Rose Limestone. None of the reported concentrations for metals exceeded the background levels of inorganic constituents in the soil. Barium was reported at a concentration of 100.4 mg/kg, chromium was reported at a concentration of 10.2 mg/kg, nickel was reported at a concentration of 9.9 mg/kg, zinc was reported at a concentration of 16.0 mg/kg, cadmium was reported at a concentration of 0.27 mg/kg, and lead was reported at a concentration of 7.41 mg/kg. The background levels for barium, chromium, nickel, zinc, cadmium and lead in Glen Rose Limestone material are 10.4 mg/kg, 10.0 mg/kg, 7.34 mg/kg, 12.0 mg/kg, 0.06 mg/kg, and 5.17 mg/kg, respectively. In addition, nickel was detected above the background level (7.34 mg/kg) in the Glen Rose Limestone sample collected from the 12.0 ft. to 12.5 ft. bgs interval of RW-B33-SB03 at a concentration of 10.1 mg/kg. The background level of nickel in the soils at SWMU B-33 is 35.5 mg/kg. All other metals concentrations reported were below the RRS1 closure standard criteria.
In accordance with the approved work plan, a soil gas survey was not performed in association with the current investigation conducted for SWMU B-33.
In accordance with the approved work plan, groundwater samples were not collected in association with the current investigation conducted for SWMU B-33.