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SWMU B-32 RCRA Facility Investigation/Closure Report
Section 2 - Field Investigation
2.1 - Field ActionsAt SWMU B-32, lead shot-contaminated sand was used as backfill around a PVC pipe used for sanitary waste purposes. In an effort to characterize the site and determine its readiness for RRS1 closure, a geophysical investigation was performed in 1996. Also in 1996 surface samples were collected, five excavation pits were dug and three soil borings were advanced to assess the extent of contamination. Analytical data associated with the surface, subsurface, and excavation test pit samples were rejected by the EPA in 1999 due to questionable laboratory practices by ITS Laboratories. In 1997, contaminated material was excavated, stabilized, and disposed off-site. Subsurface sampling was performed in 2000. The surface samples and excavation test pit samples could not be re-collected because the soil from which these samples were originally collected had been excavated and removed from the site.
Electromagnetic (EM) and ground-penetrating radar (GPR) geophysical surveys were conducted at SWMU B-32 in March 1996. Prior to collecting EM or GPR data, a grid system which encompassed the areas of suspected ground disturbance was established at each site. SWMU B-32 was divided into two geophysical survey grids because of a joint in the sanitary sewer pipeline. One grid was 20 feet long, with 10 foot intervals. The second grid was 80 feet long and 20 feet wide, with 20 foot intervals.
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 10 and 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, a site near SWMU B-32 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 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.
2.1.2 Waste Excavation and Disposal
In July 1997, five test pits were excavated to investigate potential contaminated sand and projectile materials at SWMU B-32. Five test pits approximately 3.5 feet deep and 6 feet square were excavated. The excavated material was placed on visqueen within the boundaries of SWMU B-32. Field observation of the sand material removed from the test pit confirmed the presence of shot material. One soil sample was obtained from each of the five test pits and the soil samples were identified as B32‑T1 through B32-T5. The samples were collected at 3.5 feet below ground surface (bgs) and analyzed by ITS Laboratories; however, in April 1999, the U.S. Environmental Protection Agency (EPA) ruled that the ITS results were unusable.
After confirming with the five test pits that the pipe bedding around the sewer line contained shot material, all visibly affected soils were removed from around the sewer line at the site. The pipe bedding and sand fill material that was removed (approximately 36 cubic yards of material) was placed on visqueen plastic for future disposal and clean fill material was placed into the excavations. All bedding material that visibly contained shot was removed.
In April 1999, representative samples from the excavated soil at SWMU B-32 were collected and analyzed for leachable lead (EPA methods SW-1311 and SW-7421) and total explosives (SW-8330) by EMAX Laboratories in Torrance, California. Data from analytical results indicated that soils contained no explosives, and leachable lead levels indicated the soils were not suitable for non-hazardous disposal within a municipal landfill. In 1999, the 36 cubic yards of contaminated sand and soil were removed and properly stabilized according to the Waste Analysis Plan (Volume 1-4, RL33 Addendum). The soil was solidified using Portland cement to achieve non-hazardous Class 2 levels, and was disposed offsite at Covel Gardens Landfill in San Antonio, Texas.
In accordance with the approved work plan, a soil gas survey
was not performed in association with the investigation conducted for SWMU
B-32.
Three surface soil samples were collected March 12, 1996, from the top one-half foot of soil in order to compare results with soil background levels for metals and explosives. Sample B32-SS1 was collected at the southwest end of SWMU B-32, B32‑SS2 from the center and B32-SS3 from the eastern portion of the site.
These samples were analyzed by ITS Laboratories. Analysis of the surface samples was deemed invalid by the EPA in 1999. Surface samples were not re-collected under the RL17 work plan because the surface materials sampled previously had been excavated and disposed offsite.
2.1.5 Subsurface Soil SamplesOn August 23 and 26, 1996, three soil borings were advanced at SWMU B-32 adjacent to the surface soil samples collected March 12, 1996 and identified as B32-SB1, B32-SB2 and B32-SB3. Two samples were retained for analysis from each of the borings. The samples were submitted to ITS Laboratories for analysis of metals and explosives. Analyses of these samples were deemed invalid by the EPA in 1999. The RL17 Work Plan Amendment was created to replace the invalid laboratory data.
On March 13 and 15, 2000, three soil borings were advanced at SWMU B-32 adjacent to the locations where borings were advanced in 1996 (Figure B32-4). Each sample was analyzed for explosives using EPA method SW-8330 by DataChem Laboratory in Salt Lake City, Utah. O’Brien and Gere Laboratories in Syracuse, New York analyzed for barium, chromium, copper, nickel, and zinc by method SW-6010A; arsenic by method SW-7060A; cadmium by method SW-7131A; lead by method SW-7421; and mercury by method SW-7471A. Appendix B provides a summary of analytical results reported. Equipment decontamination procedures, as well as sample collection, preparation, handling, and shipping protocols are described in the Sampling and Analysis Plan (Volume 1-4, Quality Assurance Project Plan). Quality assurance (QA) and quality control (QC) samples were collected as described in the AFCEE QAPP (Volume 1-4). All sampling points were surveyed by Parsons using a Trimble Asset-grade geographic positioning system (GPS). 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 geographic information system (GIS) database.
The soil/rock samples obtained from the SWMU B-32 area consisted of either Crawford and Bexar Stony Soils or Upper Glen Rose Limestone material. Generally, soils in the topmost foot of the soil profile at SWMU B-32 were silty, poorly sorted, dry and brown with limestone pebbles and cobbles present. The Upper Glen Rose was encountered between 0.5 and 7.5 feet bgs. The Upper Glen Rose was reported as pinkish white to pale yellow, massive, hard, and dry. No contamination was detected with a photoionization detector (PID) during soil boring installation and no water was detected in the subsurface during the soil boring installations. All investigation-derived waste (IDW) generated during the drilling effort was properly containerized, labeled, and disposed.
For each boring location at SWMU B-32, soil samples were collected at two different depths. RW-B32-SB01 samples were collected at intervals of 3.5 to 4.0 feet below ground surface (bgs) and 8.5 to 9.0 feet bgs. RW-B32-SB02 samples were collected at 3.5 to 4.0 and 11.5 to 12.0 feet bgs. Sampling intervals for RW-B32-SB03 were 3.5 to 4.0 and 12.0 to 12.5 feet bgs. A field duplicate for the sample at RW-B32-SB03 (12.0 to 12.5) was collected.
In accordance with the approved work plan, groundwater samples were not collected in association with the investigation conducted for SWMU B-32.
The geophysical surveys revealed no evidence of subsurface anomalies related to past waste disposal activities. There was little variation in the data recorded during the EM survey, which can be interpreted as homogenous and consistent soil and bedrock profiles throughout the SWMU (Figure B32-5 and Figure B32-6). In-phase readings during the EM survey ranged from a minimum of 1.5 ppt, to a maximum 31.8 ppt. Quadrature-phase readings ranged from a low of 10.1 mS/m, to a high of 107.5 mS/m.
2.2.2 Waste Excavation and Disposal
As described in Section 2.1.2, 36 cubic yards of contaminated sand and soil were removed and properly stabilized according to the Waste Analysis Plan (Volume 1-4, RL33 Addendum). The soil was solidified using Portland cement to achieve non-hazardous Class 2 levels, and was disposed offsite.
In accordance with the approved work plan, a soil gas survey
was not performed in association with the investigation conducted for SWMU
B-32.
In accordance with the approved work plan, surface soil samples were not collected in association with the investigation conducted for SWMU B-32.
Three soil borings, RW-B32-SB01, RW-B32-SB02 and RW-B32-SB03, were advanced at the locations shown on Figure B32-4. Each soil boring was installed in the location of a corresponding soil boring installed in 1996. Soil samples were obtained continuously from the ground surface to the boring termination depth and screened for organic vapors utilizing olfactory responses and headspace analysis conducted with a PID.
Soil boring logs from the borings advanced in 1996 are presented in Appendix A. As provided in the work plan, new boring logs were not to be created, but differences between the 1996 and 2000 borings were to be noted. No significant differences in the lithologies of the borings advanced in 2000 were noted.Two samples were collected from each of three soil borings at SWMU B-32 and analyzed for explosives and metals. The sample from RW-B32-SB02 (3.5 to 4.0 feet bgs) consisted of soil. Analytical results from this sample were below RRS1 criteria for all COCs. The remaining samples collected consisted of Upper Glen Rose Limestone material. A summary of detected constituents is presented in Table B32-1.
No explosives were detected in any of the samples analyzed.
Samples from all three of the borings advanced exceeded the RRS1 criteria for some metals. All samples with metals concentrations exceeding the background levels were taken from the Upper Glen Rose Limestone. The Glen Rose Limestone background levels for the detected metals are 10.0 mg/kg barium; 8.1 mg/kg chromium; 6.8 mg/kg nickel; 11.3 mg/kg zinc; and 0.1 mg/kg cadmium. Metals concentrations detected in the one soil sample collected at the site (RW-B32-SB02, 3.5 to 4 feet bgs) were below soil background levels. The other samples were collected from the Glen Rose Limestone.
Barium was reported at concentrations exceeding its background level in three borings. Samples RW-B32-SB01 (8.5 to 9.0 bgs) reported 22.8 mg/kg, RW‑B32-SB02 (11.5 to 12.0 bgs) reported 31.2 mg/kg, and RW-B32-SB03 FD1 (12.0 to 12.5 bgs) reported 12.2 mg/kg concentrations for barium. All concentrations were below the Texas-specific median background concentration of 300 mg/kg. Chromium was reported at concentrations above background in one sample from RW‑B32-SB02 (11.5 to 12.0 bgs) at 13.2 mg/kg, but this is below the Texas-specific median background concentration of 30 mg/kg.
In three borings, nickel was detected at levels in exceedance of the background concentration of 6.8 mg/kg. Nickel was detected in RW‑B32-SB01 (8.5 to 9.0 bgs) at a concentration of 23.6 mg/kg, from RW‑B32-SB02 (11.5 to 12.0 bgs) at a concentration of 17.0 mg/kg, and from RW-B32-SB03 (3.5 to 4.0 bgs) at a concentration of 7.6 mg/kg. The Texas-specific median background concentration is 10 mg/kg. Zinc was reported in six samples at concentrations exceeding background (11.3 mg/kg). Sample RW‑B32‑SB01 (3.5 to 4.0 bgs) reported 12.0 mg/kg, RW‑B32‑SB01 (8.5 to 9.0 bgs) reported 59.4 mg/kg, RW-B32-SB02 (11.5 to 12.0 bgs) reported 32.2 mg/kg, RW‑B32-SB03 (3.5 to 4.0 bgs) reported 41.8 mg/kg, RW-B32-SB03 (12.0 to 12.5 bgs) reported 27.4 mg/kg and RW-B32-SB03 FD1 (12.0 to 12.5 bgs) reported 26.6 mg/kg. The Texas-specific median background concentration is 30 mg/kg.
Cadmium was reported at concentrations exceeding its background value of 0.1 mg/kg in four samples. Sample RW-B32-SB01 (8.5 to 9.0 bgs) reported 0.22 mg/kg, RW-B32-SB02 (11.5 to 12.0 bgs) reported 0.13 mg/kg, RW‑B32‑SB03 (3.5 to 4.0 bgs) reported 0.33 mg/kg and RW-B32-SB03 (12.0 to 12.5 bgs) reported 0.22 mg/kg. There is no Texas-specific median background concentration for cadmium.
In accordance with the approved work plan, groundwater samples were not collected in association with the investigation conducted for SWMU B-32.