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Final AOC-67 RCRA Facility Investigation Report
Section 2 - Field Investigation
Bluing liquids and potentially PCE and TCE were stored in an AST on a concrete pad within AOC-67. This AST was removed by 1997. In an effort to characterize the site and determine its eligibility for closure under RRS1, three soil borings were advanced at AOC-67 in April 2001 and sampled to gather data to either support site closure or provide information regarding cleanup remediation or future investigation phases at the site.
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 in association with the investigation conducted for AOC-67.
A soil gas survey was performed in January and February 2001 (Draft, Soil Gas Survey Technical Report, Parsons ES, 2001) to address AOC-57, -65, and -67. The soil gas sampling grid within AOC-67 was not tightened (to less than the 25 foot spacing) because no contamination was indicated in any of the soil gas samples collected within AOC-67. The soil gas PCE plume identified at AOC-65 came within 35 feet of AOC-67.
Three surface soil samples were collected during the advancement of soil borings in April 2001. The sampling procedure for these samples is described in Section 2.1.4 since the surface samples were collected in conjunction with the subsurface soil samples as described below. The sampling procedures for the AOC-67 RFI are also summarized in Section 2 the Sampling and Analysis Plan Addenda (Addendum Specific to Field Sampling Plan for Subsurface Soil Boring Activities at AOC-65 and AOC-67 under AETC DO 5084, Volume 1-4: Scoping Documents, DO 5084 Addendum Tab, Environmental Encyclopedia).
Two composite surface soil samples were collected from within AOC-67 on January 2, 2002 following some utility work that trenched through AOC-67. Sample AOC67-1 is a composite of four soil samples northeast of the concrete pad at AOC-67, and AOC-67-2 is a composite of four samples collected just northwest of the concrete pad. Both sets of samples were collected in a line perpendicular to Building 90-1. These samples were sent to DHL Analytical Laboratories for analysis of metals (barium, cadmium, chromium, copper, lead, and zinc). It should be noted that results of the analysis of these samples may be used for screening, but not for closure purposes.
On April 3 and 4, 2001, three borings were advanced at AOC-67 (Volume 1-1, DO5084 Work Plan Addendum) to assess potential site contamination (Figure AOC76-4). Borings were advanced to 35 feet, and two soil/rock samples were retained from each boring. One sample was collected from each boring in the top 3 feet. The second sample from each boring was selected to determine the vertical extent of potential contamination and therefore, was selected based on PID readings and structural/geological features. In the absence of any features suggestive of potential contamination, a sample was retained from the borehole terminus, to determine if contamination was present at depth. The sampling intervals for each boring are presented in Appendix B.
In these borings, the Lower Glen Rose limestone was encountered between 0 and 2 feet bgs. 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 the borehole terminus, each boring was left open over-night to determine if perched water would accumulate. Water was not encountered in any of the borings advanced at AOC-67.
The potential for hydrocarbons was monitored by screening the retrieved core with a PID during boring advancement. The only PID measurements above 0 were observed in samples from the Glen Rose limestone. In boring SB2 (2.5 to 3.5 feet), PID readings of 0.1 and 0.4 ppm were observed. An environmental sample was retained from 2 to 3 feet, which represents the interval associated with these PID readings.
Equipment decontamination procedures, as well as 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. Quality assurance (QA) and quality control (QC) samples were collected as described in the AFCEE QAPP (Volume 1-4, Quality Assurance Project Plan). Sampling locations were marked by Parsons with a Trimble Asset-grade GPS with 1-meter accuracy. Sample locations will be incorporated into CSSA-GIS.
In accordance with the approved work plan, groundwater samples were to be collected only if water accumulated in the borings after advancement. However, water did not accumulate, and therefore, groundwater samples were not collected in association with the investigation conducted for AOC-67.
2.1.6 Investigative-Derived Waste
The rock cuttings generated during boring advancement at AOC-67 and AOC-65 were containerized in eight 55 gallon drums 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 a toxicity characterization leaching procedure (TCLP) on VOCs and metals. The analysis of this sample, presented in Appendix F, indicates that the waste may be disposed of according to Class 2 non-hazardous criteria as specified in 30 TAC 335 subchapter R. The waste is currently being considered for disposal at the Covel Gardens facility of Waste Management Inc. located in San Antonio Texas.
In accordance with the approved work plan, a geophysical survey was not performed in association with the investigation conducted for AOC-67.
In accordance with an approved work plan (Soil Gas Sampling and Analysis Plan Addenda, Dec., 2000), a soil gas survey was performed in January and February 2001 (Soil Gas Survey Technical Report, Parsons ES, 2001) to address AOC-57, -65, and -67. The soil gas sampling grid around AOC-67 was not tightened to less than the 25 foot spacing because no contamination was indicated within AOC-67. The soil PCE plume from this study is presented in Figure AOC67-4. The soil gas PCE plume identified at AOC-65 came within 35 feet of AOC-67.
Surface soil samples were collected during the advancement of the three soil borings in April 2001. Results for these samples are described in Section 2.2.4 (below), since the surface samples were collected in conjunction with subsurface samples.
Of the two composite samples collected at AOC-67 in January 2002, AOC67-1, collected from four samples northeast of the concrete pad, exceeded the CSSA soils background concentration for lead. Lead was reported at 240 mg/kg in AOC67-1, which exceeds the CSSA soils background concentration of 84.5 mg/kg. Results for both composite samples are presented in Appendix G. These data indicate that metals contamination extends to the northeast side of the concrete pad, but do not indicate metals contamination northwest of the pad.
Metals
Surface soil samples collected from SB1, SB3, and SB3 FD1 at AOC-67 contain metals in concentrations greater than the CSSA soils background concentration. Chromium (50.0 mg/kg) and lead (252.35 mg/kg) exceed the CSSA soils background concentrations of 40.2 and 84.5 mg/kg, respectively, in the sample retained from the top 1 foot of soil from SB1 (Table AOC67-1).
The SB3 surface soil sample (0 to 0.6 feet bgs) and its field duplicate revealed concentrations of chromium (47 and 52.9 mg/kg), zinc (108.77 and 148.08 mg/kg), and lead (342.56 and 324.45 mg/kg) in excess of background concentrations of 40.2, 73.2, and 84.5 mg/kg, respectively. The field duplicate concentration of barium (218.26 mg/kg) was greater than background (186 mg/kg), but the sample concentration (82.5 mg/kg) was less than background. For copper, the SB3 soil sample exceeds background (23.2 mg/kg) with a reported concentration of (31.77 mg/kg), whereas the field duplicate (11.65 mg/kg) was less than background.
Analysis of the 30 to 30.5 foot sample retained from SB3 resulted in a reported chromium concentration of 8.8 mg/kg, which slightly exceeds the Glen Rose background concentration (8.1 mg/kg). The reported nickel concentration for the sample from the 30 to 30.5 increment of SB3 (11.28 mg/kg) is greater than the background concentration (6.8 mg/kg).
VOCs
SB3 (30 to 30.5 feet bgs) exceeds the RL for methylene chloride, with a reported concentration of 0.0093 mg/kg, and an RL of 0.005 mg/kg (Table AOC-67-1). No other soil/rock sample concentrations exceed RLs for VOCs. It should also be noted that naphthalene and toluene, potentially associated with the usage of oils or weapons, were detected at concentrations below their SQLs.
SVOCs
SVOC RLs were not exceeded for any of the soil/rock samples collected at AOC-67 (Table AOC67-1). However, several SVOC compounds potentially associated with ordinance maintenance, including naphthalene, were detected at concentrations below their SQLs.
TPHs
TPH RLs were not exceeded for any of the soil/rock samples collected at AOC-67 (Table AOC67-1).
In accordance with the approved work plan, groundwater sampling was planned only if water accumulated in the borings after advancement, or in the wells after emplacement. However, water did not accumulate, so wells were not installed. Therefore, groundwater samples were not collected as part of the investigation conducted for AOC-67.
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.