SB-3 (1.5 to 2.0 feet)
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Final AOC 65 RCRA Facility Investigation Report
Section 2 - Field Investigation
As outlined in the Environmental Encyclopedia site-specific work plan (Volume 1-3, AOC 65), the objectives of the RFI were to conduct a geophysical survey and to collect surface soil samples. After identifying any geophysical anomalies, three grab surface soil samples were collected at a depth of six inches below surface grade based upon the locations of the geophysical anomalies. Each sample was analyzed for VOCs, SVOCs, explosives, and metals. All field activities were conducted in accordance with the Field Sampling and Analysis Plan (Volume 1-4, Field Sampling Plan, Quality Assurance Project Plan, and DO5068 and DO5084 Addendums).
Cleaning solvents, including PCE and TCE, were formerly used in a vat which was located in a concrete vault within AOC-65. The vat was removed in 1995 and a citrus-based cleaner replaced the usage of chlorinated solvents. Under DO 5068, soil samples were collected from underneath the former vault area in Building 90 to characterize the site and determine the readiness of AOC-65 for RRS1 closure. A soil boring was advanced in April 2000, approximately 15 feet down gradient of the Building 90 floor drain line terminus.
To further assess the extent of VOC contamination in this area, a more comprehensive investigation, including a soil gas survey, soil and bedrock sampling, and installation of shallow monitoring wells, was initiated under DO 5084 in 2001. Based on results of the soil gas survey, 14 soil borings were advanced inside and around the perimeter of Building 90 in March and April 2001. Monitoring wells were installed in four of the borings, with two independently screened intervals in one of the wells (MW-2A and MW-2B).
In accordance with the approved work plan, a geophysical survey was not performed during this phase of the investigation conducted at AOC-65. Investigations into faulting in the area of Building 90 are ongoing (AOC-65 Treatability Test Plan, Draft). These investigations, using resistivity surveys, should elucidate the location of the fault projected from the USGS data, as well as other potential faults in the area of Building 90.
A soil gas survey was performed in January and February 2001 (Soil Gas Survey Technical Report, Parsons ES, 2001) to address AOCs-57, -65, and -67, as described in Section 1.4. To optimize the selection of subsurface soil samples and monitoring well locations, this investigation was prior to the soils investigation at AOC-65.
Two soil samples were collected at AOC-65 on April 7, 2000 (Figure AOC-65-4), from underneath the western vault (AOC-65-Pit1, AOC-65-Pit2). Samples were collected from underneath the concrete floor of Building 90 by coring through the floor and using a hand trowel to obtain the soil samples. These soil samples were analyzed for VOCs and metals. Two environmental samples, a field duplicate (FD), an equipment blank (EB),and a trip blank (TB) were sent by overnight delivery to O’Brien and Gere Laboratories in East Syracuse, New York on April 7, 2000.
All decontamination, sample preparation, and handling followed the protocols established in the Field Sampling and Analysis Plan (Volume 1-5, Field Sampling Plan, Quality Assurance Project Plan). Environmental sampling also included the collection and submittal of quality assurance (QA)/quality control (QC) samples in accordance with the AFCEE QAPP (Volume 1-4, Quality Assurance Project Plan).
Surface samples were collected from the top 3 feet of soil during the advancement of borings in April 2000 and March and April 2001. The procedures for collecting these samples are described in the discussion in Section 2.2.2.
Soil borings were advanced at AOC-65 during two field efforts. SB-1 was advanced in April 2000 and, in March and April 2001, 14 additional borings were advanced in and around Building 90 and around the perimeter of the suspected AOC-65 contaminant plume. Borings were advanced by spilt spoon sampling until refusal, then by air rotary coring.
Equipment decontamination procedures and sample collection, preparation, handling, and shipping are described in the Field Sampling and Analysis Plan (Volume 1-5, Quality Assurance Project Plan). Deviations from the Sampling and Analysis Plan are noted below. QA/QC samples were collected as described in the AFCEE QAPP (Volume 1-4, Quality Assurance Project Plan).
On April 8, 2000, one soil boring (SB-1) was drilled approximately 50 feet west of AOC-65 (Figure AOC-65-4). This boring was located approximately 15 feet down gradient of the terminus of a drainage line that exits the building in the area of the former solvent vault area. The purpose of advancing this boring was to determine if the drain line may have carried contaminants to the storm water ditch adjacent to Building 90. CSSA funded the data validation and reporting of the samples collected from this boring independent of the two RFI delivery orders (DO 5068 and DO 5084).
Bedrock was encountered in SB-1 at 3.2 feet bgs. Soil samples from the top 3.2 feet originated from the Crawford and Bexar soil complex. In general, the soils were plastic, dry to damp, silty clays with very fine-grained sand and caliche gravel. At the time of sampling, a PID reading of 74.8 parts per million (ppm) (VOCs) was recorded at 1 feet bgs. Bedrock below 3.2 feet was the Lower Glen Rose limestone, which appeared as a mudstone/wackestone with massive to laminated bedding.
Five samples were obtained from SB-1 from discrete depth intervals (0-0.5, 0.75-1.25, 4.5-5.0, 9.5-10.0, and 13.0-13.5 feet bgs). All samples were analyzed for VOCs and metals. One sample (0.75 – 1.25 feet bgs) was analyzed for TPHs by method TX 1005. In all, a total of five environmental samples, one field duplicate, one matrix spike, one spike duplicate, and one trip blank from SB-1 were submitted for analyses to APPL Laboratories in Fresno, California on April 8, 2000.
To further assess potential soil contamination, an additional 14 borings were advanced at or near AOC-65, with three borings advanced inside Building 90 Between March 22 and April 4, 2001 (Volume 1-1, DO5084 Work Plan Addendum). The boring locations were selected based on “hot spots” identified in the soil gas survey (Draft Soil Gas Survey Technical Report, Parsons ES, August 2001). Two soil/rock samples were retained from each boring. The sampling intervals are presented for each boring in Appendix A. Samples were submitted to APPL Laboratories for analysis of VOCs, TPH, and metals.
The borings outside Building 90 were advanced to 35 feet. The three borings inside Building 90 (SB-8A, SB-9, and SB-10) were advanced to refusal, which was encountered less than 6 feet below the concrete slab in each of the three borings. The Lower Glen Rose Limestone was encountered between ˝ foot and 6 feet bgs in the 14 borings. The Crawford and Bexar soils were slightly moist, clayey sands with angular limestone clasts. The Lower Glen Rose was hard, dry, competent limestone, with bands of highly weathered, moist, marly limestone. After attaining borehole terminus at 35 feet, borings were left open overnight to determine if perched water would accumulate. Water was encountered to a depth of 19.4 feet bgs 14 hours after the advancing CS-AOC-65-MW-1 boring.
The
selection of which borings were to be completed as wells and the boring names
were altered during the field effort from those initially planned in the Field
Sampling and Analysis Plan. The original and final names are presented in
Table AOC-65-1.
Specific information on the field activities completed during the drilling of the 14 borings is described below.
Interior of Building 90
During the soil gas survey, the highest levels of contamination were observed in samples collected from under Building 90. To investigate the extent of potential contamination beneath Building 90, advancement of three borings (SB-8A, SB-9, and SB-10) was attempted inside the building using a skid-mounted hollow stem auger rig. A small-diameter core of the concrete floor was first removed to allow access to the sub-slab material, and drilling commenced into the underlying soil fill. Because the skid-mounted stem auger drill rig was not capable of drilling into bedrock, the borings were advanced to refusal (between 4.0 and 5.2 feet), sampled, plugged, and abandoned, without further advancement.
The top 3 feet of soil fill beneath Building 90 was pale yellow, sandy, and moist. Below this, a dark olive brown, slightly moist, slightly plastic soil was present to approximately 4 feet, where refusal was hit in SB-8A and SB-10. A pale yellow, gravelly limestone fill was present from 4.0 to 5.2 feet in SB-9. Small, angular white limestone clasts were present throughout the soil profile.
Potential VOC contamination was detected by PID in all three borings, with the concentration increasing with depth. The maximum PID readings were 22.2 ppm for SB-8A, 59.0 ppm for SB-9, and 17.9 ppm for SB-10. Samples for analyses were retained from these portions of the borings. An ambient blank was collected during the advancement of SB-9.
Exterior
of Building 90
AOC-65-SB-3
was advanced near SB-1, at the outfall of a drain line that extends 50 feet
westward from Building 90 to a storm water ditch. During the drilling of
SB-3, potential VOCs, measured by the PID, were detected in the soil profile (0 ppm
at the surface, 5.3 ppm at 0.5 feet bgs, and 202 ppm at 2.0 feet
bgs). A sample was retained from 1.5 to 2.0 feet. Bedrock was
encountered at 2 feet, and the PID did not register any potential hydrocarbons
over the remainder of the boring (2 to 35 feet bgs).
Potential VOCs were indicated by PID screening in the top 15 feet of SB-11. SB-11 is located exterior to Building 90, close to the former solvent vault area in Building 90, and adjacent to the exterior loading dock. A sample was retained from 8.5 to 9.0 feet bgs, because this interval contained the highest PID reading (212 ppm). The material from this interval is a fractured, dry, hard, sandy limestone.
SB-6 and SB-13 are located on the east side of Building 90 (Figure AOC-65-4). On the west side of the building, borings MW-3, MW-2AB, and SB-4 were emplaced south and southeast of the drainage ditch and SB-5, MW-1, and SB-7 were advanced north of the drainage ditch. MW-4 was completed directly southeast of Building 90. Potential hydrocarbons were indicated by low PID readings (<7 ppm) in the soil and rock portions of several borings, and samples were retained from these intervals. PID readings and associated sampling intervals are shown on the boring logs in Appendix D.
Monitoring Well Installation
Three monitoring wells were installed on the west side, and one on the south side of Building 90. The intervals for screening were selected from observations on the geological logs and measured depths to water, when water was encountered. The well locations were originally specified in the work plan, in advance of the field effort. However, during the field effort, it was determined that the wells should preferentially be installed in borings that produced observable moisture during boring advancement or within the first 24 hours after drilling. The final well names and locations are presented in Table AOC-65-1 and Figure AOC-65-4, respectively. The well completion information is presented in Appendix D.
It should also be noted that two monitoring wells are nested at different depth intervals within the same borehole (CS-AOC-65-MW-2AB). These monitoring wells are MW-2A (screening interval, 9 to 19 feet) and MW-2B (screening interval, 23 to 33 feet). The borehole log and soil/rock samples collected from it are referred to as MW-2AB, whereas water samples are labeled MW-2A and MW-2B, as appropriate.
Groundwater samples were periodically collected from the shallow monitoring wells. In addition, a “grab” water sample was collected from SB-6. The samples were collected with a bailer and were submitted to either APPL., Inc. or DHL Analytical for analysis. All samples were analyzed for VOCs. MW-1 and MW-4 samples were also tested for metals. Because the wells produced very low quantities of water, well purging was undertaken prior to sample collection during the initial sampling event on April 15, 2001. Groundwater samples were collected by CSSA personnel on August 27, 2001 and November 19, 2001. CSSA funded the data validation and reporting of the samples collected for these samples independent of the two RFI delivery orders (DO 5068 and DO 5084). The procedures for decontamination, sample preparation, and handling followed the protocols established in the Field Sampling and Analysis Plan (Volume 1-5, Field Sampling Plan, Quality Assurance Project Plan).
2.2 - Investigative-Derived Waste
The rock cuttings generated during boring advancement at AOC-67 and AOC-65 were containerized in eight 55 gallon drums that were stored as investigative derived waste (IDW) for proper waste characterization and subsequent off-site disposal efforts. A composite sample, composed of equal amounts of soil/rock cuttings from each of the eight drums, was collected on September 27, 2001 and submitted to APPL Laboratory on the same day for Toxicity Characterization Leaching Procedure (TCLP) on VOCs and metals. The results of analysis of this sample, which is presented in Appendix F, indicate that the waste meets Class 2 Non-hazardous criteria as specified in 30 TAC 335 subchapter R. Furthermore, the IDW was determined not to contain a listed hazardous waste. This “contained-in” determination is documented in an RFI and IM Waste Management Plan dated August 2002. The waste is currently being considered for disposal at the Covel Gardens facility of Waste Management Inc. located in San Antonio, Texas.
No geophysical survey was performed as part of this phase of the RFI conducted for AOC-65. Investigations into faulting in the area of Building 90 are ongoing (AOC 65 Treatability Test Plan, Draft). These investigations, using resistivity surveys, should elucidate the location of the fault projected from the USGS data, as well as other potential faults in the area of Building 90.
In accordance with the approved work plan, a soil gas survey was performed in January and February 2001 (Draft Soil Gas Survey Technical Report, Parsons ES, 2001). Results from this soil gas survey were used to select appropriate soil boring and monitoring well locations. Further soil gas samples were not collected as part of this phase of the RFI at AOC-65.
The surface samples from underneath the former metal vat area at AOC-65 (AOC-65-Pit1, AOC-65-Pit2) are discussed in this section. Surface samples collected during advancement of borings in April 2000 and March and April 2001, are described in Section 2.2.2.
Metals
None of the reported metals concentrations from the two samples collected from fill material under Building 90 (AOC-65-Pit1, AOC-65-Pit2) were detected above the CSSA soil background concentrations (Table AOC-65-2).
VOCs
PCE was detected in AOC-65-Pit1, -Pit 1 FD, and –Pit2 at 1.74, 2.44, at 3.74 milligrams per kilogram (mg/kg), respectively, which exceed their respective RLs of 0.716, 0.699, and 0.635 mg/kg. This confirms the soil gas data collected in the soil gas survey, which suggested that PCE was present in the fill material under the former solvent vault area.
Metals
Barium (11.93 mg/kg), chromium (9.10 mg/kg), and mercury (0.22 mg/kg) concentrations exceeded Glen Rose background concentrations (10.0, 8.2, and 0.1 mg/kg) in the sample retained from 9.5 to 10.0 feet bgs for AOC-65-SB-1, located near the joint between the drainage from Building 90 and the drainage ditch west of Building 90 (Table AOC-65-3). Barium (10.1) and chromium (8.2 mg/kg) concentrations also met or exceeded background in the SB-3 (9.5 to 10.0 feet) field duplicate. None of the other five samples retained from SB-1 exceeded metal background concentrations.
Background was exceeded for barium, chromium, cadmium, zinc, nickel, copper, and lead in the remainder of the borings advanced at AOC-65 (Table AOC-65-3).
Metals exceedances occurred for surface samples:
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SB-3 (1.5 to 2.0 feet) |
Metals exceedances occurred for samples collected at depth:
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CS-AOC-65-MW-1 (6.0 to 6.5 feet); |
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CS-AOC-65-MW-2AB (23.0 to 23.5 feet); |
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CS-MW-4 (7.0 to 7.5 feet); |
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CS-MW-4 (31.0 to 31.5 feet); |
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SB-3 (21.0 to 21.5 feet); |
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SB-4 (34.0 to 34.5 feet); |
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SB-5 (34.5 to 35.0 feet); |
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SB-7 (34.5 to 35.0 feet); |
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SB-11 (8.0 to 8.5 feet); and |
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SB-13 (23.5 to 24.0 feet). |
Notably, the sample collected from 1.5 to 2.0 feet bgs at SB-3 contained chromium (73.10 mg/kg), copper (190.73 mg/kg), zinc (979.49 mg/kg), lead (1,259.95 mg/kg), and cadmium (7.23 mg/kg) in concentrations that exceed the CSSA soils background concentrations (40.2, 23.2, 73.2, 84.5, and 3.0 mg/kg, respectively). SB-3 was advanced where the drainage ditch extending from Building 90 meets the draining ditch west of
Building 90. The underlying bedrock sample retained from 21.0 to 21.5 feet at SB-3 had concentrations of barium, chromium, nickel, and lead (11.33, 8.50, 7.24, and 5.96 mg/kg) that only slightly exceeded the Glen Rose background concentrations (10.0, 8.1, 6.8, and 5.5 mg/kg), suggesting that contamination is limited to the soil in this area.
VOCs
N-butylbenzene was detected in SB-1 (0.0 to 0.5 feet bgs) at 0.168 mg/kg, which is slightly greater than the RL (0.150 mg/kg). Several VOCs are detected above RLs in the surface sample from SB-3 (1.5 to 2.0 feet bgs), which recorded 212 ppm on the PID during boring advancement: N-butylbenzene, cis-1,2-dichloroethene, 4-(cymene, p-) isopropyltoluene, TCE, 1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene. These were all detected in concentrations at least three times their RL.
PCE was detected in concentrations exceeding sample RLs in one sample retained from the Glen Rose Limestone (SB-11, 8.0 to 8.5 feet), in the soil samples collected from borings MW-2AB, SB-3, MW-3, and SB-11, in four out of six soil samples collected from the fill beneath Building 90 (from SB-8, SB-9, and SB-10), and in both the soil fill samples collected under Building 90 in April 2000 (AOC–65–Pit1 and AOC–65–Pit2, Section 2.1.2). The detected PCE concentrations range from 0.0097 to 1.491 mg/kg, with the exception of SB-3 (1.5 to 2.0 feet bgs), which has a reported PCE concentration of 124.434 mg/kg.
It should be noted that PID measurements taken during the collection of several borings recorded potential VOC contamination in both soil and bedrock. However, PID measurements may be attributable to water or other interferences, and may not be due to hydrocarbons, as moisture was noted in the soil boring logs. All PID field screening results are provided on boring logs found in Appendix D.
Based on these results, the soil gas PCE plume identified by the soil gas survey at AOC-65 is confirmed by the borings advanced in this field effort. Within the soil gas plume, PCE in excess of sample RLs was detected in fill samples from under Building 90 (AOC-65-Pit1, AOC-65-Pit2, SB-8A [3.0 to 3.5 feet], SB-9 [3.0 to 3.5 and 4.0 to 4.5 feet], and SB-10 [3.5 to 4.0 feet]), along the drain line that runs from the former solvent vault area to the drainage ditch (SB-11), and in the soils south and southwest of the drainage line (MW-3, SB-3, and MW-2AB). Soil borings SB-7, SB-4, SB-1, and SB-6, located outside of the soil gas plume, did not register PCE.
PCE was not detected in the soil and bedrock samples from some borings located within the soil gas survey PCE plume (MW-4, MW-1, SB-5 and SB-13). There may be several explanations for this. The plume identified by the soil gas survey may have pockets of uncontaminated areas that are not identified in the isopleth contours developed from a grid sampling pattern. Variability in the soil materials, preferential flowpaths within the soils, and rainfall events that occurred in the time interval between the soil gas survey and the soil boring advancement may also affect the presence of PCE in soil samples. These all suggest that the plume migration may be highly variable, or that the plume is more discontinuous than the soil gas survey results suggest.
TPHs
The SB-1 sample retained from 0.75 to 1.25 feet, which registered 74.8 ppm on the PID meter at the time of collection, exceeds RLs for diesel range organic (DRO) and gas range organic (GRO), with reported concentrations of 1,500 and 510 mg/kg, respectively. The RL is 250 mg/kg for both compounds. No other samples from SB-1 were tested for TPH.
The reported concentrations of DRO (2,863.1 mg/kg) and GRO (177.6 mg/kg) exceed RLs (500 and 50 mg/kg, respectively) for the sample retained from 1.5 to 2.0 feet from SB-3. TPHs were not detected in any other samples. SB-3 is located near the terminus of the drainage ditch that emanates from Building 90. SB-3 is located approximately 15 feet south of SB-1.
PCBs
Aroclor is detected in a soil sample retained from the drainage ditch (SB-3, 1.5 to 2.0 feet bgs) at 2.941 mg/kg, which exceeds the sample RL (0.7 mg/kg) (Table AOC-65-2).
SVOCs
SVOCs were not detected in concentrations above the sample RL in the subsurface samples collected at AOC 65 (Table AOC-65-2).
All chemistry data obtained during the course of this RFI were evaluated for usability by those processes discussed in Section 4.1 of Volume 1-1, Risk Assessment Technical Approach Document.
Groundwater samples were periodically collected from the four monitoring wells and one soil boring installed during this field effort. Groundwater was consistently found in monitoring wells MW-1 and MW-4, but is only found in monitoring wells MW-2A and MW-2B after significant rain events. MW-3 has been dry to date. All monitoring wells were purged prior to the initial sampling event on April 15, 2001. “Grab” samples with no purging were collected during subsequent sampling events on August 27 and November 19, 2001. Because the collection and analysis of these samples were funded by CSSA, results for these samples are presented in Appendix C. Because of the low quantities of water produced, it is not expected that these wells will be used as water supply wells. Samples were collected from MW-2A, MW-2B, SB-6, MW-4, and MW-1. Because groundwater samples from SB-6 were collected from open boreholes, any detected COCs cannot be associated with a specific screened interval.
The
groundwater samples collected in this field effort were obtained as screening
data, to gain a better understanding of contaminant migration in the groundwater
by fracture flow, and to obtain data that may help identify the origin of the
VOCs observed in the near surface environment at and around AOC-65. It
should be noted that groundwater is considered a separate operable unit from
bedrock and soil, so the groundwater data presented here are not reviewed with
closure as a consideration. Therefore, comparisons to closure criteria are made
only as a means of discussing contaminant transport and the use of data as a
screening tool.
Metals
Groundwater samples from MW-1, MW-2A, MW-4, and SB-6 were submitted for metals analyses. The reported nickel, zinc, and lead concentrations (0.020, 0.057, and 0.011 mg/kg) exceed the RLs (0.01, 0.05, and 0.005 mg/kg) in the groundwater sample collected from MW-1. Barium (0.0516 mg/kg) exceeds the RL (0.005 mg/kg) for MW-4 (Table AOC-65-4). However, there is no indication of metals contaminant migration between the two wells based on these results, because contamination is not observed in the well (MW-3) located between the two wells. Further, elevated levels of metals have not been identified in the deep monitoring wells (MW-6, MW-7, and MW-8) which are located in the vicinity of AOC-65.
VOCs
PCE was detected in all four groundwater samples. In particular, VOC concentrations in the water sample collected from MW-2A, which is located outside of the soil gas survey plume ranged from 950 to 3,400 µg/L.
TCE and Cis-1,2-dichloroethene were detected in samples from MW-1 and MW-2A. In MW-1, the concentrations of TCE and cis-1,2-dichloroethene are 17.0 and 1.7 mg/kg. Higher concentrations of TCE (39.0 mg/kg) and cis-1,2-dichloroethene (23.0 mg/kg) are recorded for MW-2A, which is screened from 9.0 to 19 feet.
Because VOCs were detected in the groundwater that were not detected above RLs in the soil or rock samples associated with the well borings, VOC migration in the area of AOC-65 must be further considered. The key finding from the groundwater samples collected is that VOC levels in the groundwater are generally higher than concentrations observed in the soils and bedrock.