[Home]
SWMU B-26 RCRA Facility Investigation Report
Section 2 - Field Investigation
SWMU B-26 is suspected of having been a waste disposal site because a trenched area was identified at SWMU B-26 on a 1966 aerial photograph. The dates of its usage are unknown, and it is presently inactive. Wooden pallets remain on the site next to the trench, and soils piles are situated on each end of the trench. In an effort to characterize the site and determine its readiness for RRS1 closure, a geophysical investigation and surface and subsurface sampling were performed in 1996. However, the analytical data associated with the surface and subsurface samples were rejected by the EPA in 1999. Surface and subsurface sampling were repeated in March 2000. All sampling points were surveyed by Parsons using a Trimble Asset-grade GPS. Surveying methodology is described in the Amendment to the Field Sampling Plan (Parsons ES, 2001b). All sample location and analytical data will be incorporated into the CSSA GIS database after it has been approved by AFCEE and CSSA.
An EM geophysical survey was conducted at SWMU B-26 in March
1996. Prior to collecting the EM data,
a grid system was established at the site which encompassed the areas of
suspected ground disturbance. This grid
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 area outline is shown in
Figure B26-4.
EM data were collected at 2-foot intervals along transects that were separated by 20 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 feet.
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.
In accordance with the approved work plan, a soil gas survey was not performed in association with the current investigation conducted for SWMU B-26.
Three surface soil samples (SS01, SS02, and SS03) were collected on March 7, 1996, and submitted to ITS Laboratories for analysis for metals, VOCs, and SVOCs. Sample SS01 was collected in the top half-foot of soil from one of the soil piles located parallel to the trench where a geophysical anomaly was identified. Sample SS02 was collected within the trench. Sample SS03 was collected from the circular soil pile adjoining the northern end of the trench.
In April 1999, the analytical data generated by ITS Laboratories for surface soil samples SS01, SS02 and SS03 were determined to be unusable by the EPA. The Work Plan for SWMU B-26 was amended in November 1999 (RL17 Work Plan Amendment for Data Quality Rework at SWMU B-26) to allow for re-sampling of the soils at SWMU B-26, with the purpose of replacing the unusable analytical chemistry data.
Three replacement surface soil samples (RW-B26-SS01, RW-B26-SS02, and RW‑B26-SS03) were collected at SWMU B-26 on March 23, 2000. These samples were collected adjacent to the surface soil samples collected in 1996, in the top half foot of the soil profile. Sample locations are shown in Figure B26-4. Surface soil samples were collected using a decontaminated hand trowel. Decontamination procedures, as well as sample collection, preparation, handling, and shipping, are described in the Field Sampling and Analysis Plan (Volume 1-4, Field Sampling Plan, Quality Assurance Project Plan). QA and QC samples were collected as described in the AFCEE QAPP (Volume 1-4, Quality Assurance Project Plan).
The three surface soil samples were submitted along with samples from SWMU B‑25, including a field duplicate, matrix spike, and spike duplicate collected for RW‑B25‑SB03. Samples were sent to APPL, Inc, for analysis of VOCs (SW-8260B) and SVOCs (SW-8270C) and O’Brien and Gere Laboratories for analysis of metals. Metals analysis included barium, chromium, copper, nickel, and zinc (SW-6010B); arsenic (SW-7060A); cadmium (SW-7131A); lead (SW-7421); and mercury (SW-7471A).
The soils at SWMU B-26 consist of Krum Complex soils. Generally, the soils in the topmost foot of the soil profile at SWMU B-26 were observed to be clayey and very dark grayish-brown with a trace of fine gravel.
Three soil borings (SB01, SB02, and SB03) were advanced on September 4, 1996 to collect samples of subsurface soil/rock, for analysis of metals, VOCs, and SVOCs. A soil boring was conducted in the trench (SB02), in a soil pile (SB01), and between the trench and a soil pile (SB03). Only SB01 was advanced adjacent to a surface soil sample collection location. Boring locations SB01 and SB03 were within the confines of the two anomalies identified by the geophysical survey. The borings were advanced to depths ranging from 10 to 13.2 feet bgs. Soil samples were collected from SB01 at 6 and 12 feet, from SB02 at 1, 4, and 9 feet, and from SB03 at 1, 6, and 12 feet.
In April of 1999, the analytical data generated by ITS Laboratories for the borings were determined to be unusable by the EPA. The Work Plan for SWMU B-26 was then amended in November of 1999 (RL17 Work Plan Amendment for Data Quality Rework at SWMU B-26) to allow for re-sampling of the soils at SWMU B-26, with the purpose of replacing the unusable analytical chemistry data.
Three soil borings were advanced on March 23, 2000, adjacent to the borings advanced in 1996. Figure B26-4 illustrates the boring locations. As shown on Figure B26-4, boring RW-B26-SB01 was drilled adjacent to surface sample RW-B26-SS01, within the confines of the geophysical anomaly identified in the northwestern portion of the site. Boring RW-B26-SB02 was drilled within the geophysical anomaly located within the central portion of the site, as shown on Figure B26-4. Boring RW-B26-SB02 was advanced at a location within the on-site trench. Boring RW‑B26‑SB03 was advanced in an area south of the southern extent of the trench, between the trench and an adjacent soil pile.
Subsurface soil samples were collected with a split-spoon sampler and hollow-stem auger until advancement refusal. Once refusal was encountered, borehole advancement continued via air rotary drilling techniques. Rock samples were collected with a rock core barrel. Decontamination procedures, as well as sample collection, preparation, handling, and shipping methodologies are described in the Field Sampling and Analysis Plan (Volume 1-5, Field Sampling Plan, Quality Assurance Project Plan). QA and QC samples were collected as described in the AFCEE QAPP (Volume 1-4, Quality Assurance Project Plan).
The Upper Glen Rose Limestone was encountered between 3 and 5 feet bgs. The Upper Glen Rose Limestone was observed to be a dry, massive, pale yellow limestone. No visual or olfactory evidence of contamination was observed during the drilling program. No organic vapors were detected by the PID. Groundwater was not encountered during the drilling program.
For each boring location at SWMU B-26, a sample was retained from two depths. RW-B26-SB01 samples were retained from 6-6.5 feet and 12.5-13 feet. Samples were collected at 4-4.5 and 9.5-10 feet bgs for RW-B26-SB02, and 6-6.5 and 12.5-13 feet bgs for RW-B26-SB03. In addition, a field duplicate, matrix spike, and spike duplicate were retained from RW-B26-SB03 (0.5-1 feet) and a field duplicate was retained from RW‑B26-SB02 (0.5-1 feet). These samples were submitted to APPL, Inc., for analysis of VOCs and SVOCs and to O’Brien and Gere for analysis of metals on March 23, 2000. Analytical methods were the same as those used on the surface soil samples.
In accordance with the approved work plan, groundwater samples were not collected in association with the investigation conducted for SWMU B-26. Groundwater was not encountered in any of the SWMU B-26 borings.
Both the in-phase component and the quadrature phase component of the EM survey revealed anomalies in the northwestern and central portions of SWMU B-26. The in-phase portion revealed only one anomalous area which may be related to waste management activities. Figure B26-5 shows this anomaly which is located in the northwestern portion of the SWMU and labeled A. Anomaly A could potentially be related to waste management activities because it is visible in both components of the survey. Figure B26-6 shows the quadrature phase component and anomaly A is clearly visible. The linear north-south trending anomalous area located in the central portion of Figure B26-6 (labeled B) may be indicative of subsurface disturbance, but given that it is not visible in the in-phase component, it is not thought to be associated with buried waste. The anomaly shows where the 3-foot trench is located at the SWMU and the 5-foot soil piles at the ends of the trench are visible as well.
In accordance with the approved work plan, a soil gas survey was not performed in association with the current investigation conducted for SWMU B-26.
Detected results are summarized in Table B26-1, and all results are provided in Appendix A. All metal analyses results for surface soil samples were less than the associated background concentrations.
All samples reported VOC and SVOC concentrations below RLs, therefore RRS1 criteria for VOCs and SVOCs have been met. The following organic compounds were reported below the laboratory RLs: naphthalene was reported in all three surface soil samples; 1,2,4-trichlorobenzene was reported in samples RW-B26-SS02 and RW-B26-SS03; bromobenzene, 1,2,3-trichlorobenzene, and bis(2-ethylhexyl)phthalate were detected in RW-B26-SS03.
Detected results are summarized in Table B26-2, and all results are provided in Appendix A. The majority of metal analyses results for subsurface soil samples were less than the associated background concentrations, with the exception of slight zinc exceedances at SB01 (12.5 to 13 ft), SB02 (9.5 to 10 ft), SB03 (6 to 6.5 ft), and SB03 (12.5 to 13 ft). Concentrations in these samples ranged from 11.9 mg/kg to 17.5 mg/kg, and the zinc background level for Glen Rose Limestone is 11.3 mg/kg. However, all of these exceedances are below the Texas-specific median background concentration (30 TAC 350.51(m)) of 30 mg/kg.
In addition, chromium was detected at 9.7 mg/kg at SB01 (12.5 to 13 ft), which only slightly exceeds the Glen Rose background level of 8.1 mg/kg. This concentration is below the Texas-specific median background level of 30 mg/kg.
All samples reported VOC and SVOC concentrations below RLs, therefore RRS1 criteria for VOCs and SVOCs have been met. Four VOCs were reported at concentrations below the RLs in the subsurface soil samples: methylene chloride, naphthalene, 1,2,3-trichlorobenzene, and 1,2,4-trichlorobenzene.
Bis(2-ethylhexyl)phthalate concentrations were greater than RL of 0.7 mg/kg for three samples: RW-B26-SB01 (6-6.5 feet), with an reported concentration of 30.0 mg/kg; RW-B26-SB03 (6-6.5 feet), with a reported concentration of 52 mg/kg; and RW-B26-SB03 (12.5-13 feet), with a reported concentration of 2.3 mg/kg. All other SVOC concentrations were less than the RLs.
Soil boring logs from the borings advanced in 1996 are
presented in Appendix B. As per the Rework Plan (RL17 Work Plan Amendment for Data Quality
Rework at SWMU B-26), new borings were not to be recorded, but the
differences between the 1996 and 2000 borings were noted. The borings advanced in 2000 were advanced
adjacent to the 1996 borings, and no significant differences in the materials
encountered within the borings were identified. No waste material or evidence of subsurface disturbance was
encountered in any of the borings. The
results below are presented only for the 2000 analytical data.
In accordance with the approved work plan, groundwater samples were not collected in association with the investigation conducted for SWMU B-26. Groundwater was not encountered in any of the SWMU B-26 borings.