[Home]
SWMU B-34 RCRA Facility Investigation Report Addendum
Section 3 - Conclusions and Recommendations
SWMU B-34 consists of the below-grade piping and pipe bedding that drained from a locomotive drainage pit. The piping extends 230 feet southwest from Building 28, travels underneath an open field, and drains to an outfall area near McElroy Road. The outfall area drains to a ditch adjacent to the northern side of McElroy Road. Potential COCs associated with SWMU B-34 include VOCs, SVOCs, and metals.
Previous investigation activities conducted at SWMU B-34 included a geophysical survey, surface soil sampling, and subsurface soil/rock sampling, as described in the August 2002 RFI report. The geophysical survey did not indicate any anomalies other than those associated with the building; however, several metals were detected above RRS1. Results from the Phase I sampling event (March 2000) show above-background metals and SVOC detections to depths of up to 13.5 feet below ground surface (bgs). SVOC detections are attributed to laboratory contamination, as explained in Section 1.2. Above-background metal levels were found at depths up to 12.5 feet bgs. Although metals exceeded CSSA background in Glen Rose samples, the values are well below soil background standards and are not believed to be site-related. Metals contamination was consistently detected in surface soils and subsurface soils at depths up to 5 feet bgs. The vertical extent of contamination, based on these results, is deemed to include the entire soil profile beneath SWMU B-34.
Based on results of the RFI sampling efforts, collection of additional surface soil samples was recommended to identify the extent of contamination. Since the Phase I sampling event collected samples in a linear fashion over the piping location, the intent was to move outward in all directions from these locations. Three of the samples were to be located at the pipe outfall area to determine if any discharges from the pipe to the ground surface resulted in contamination. During March 2003, fourteen surface soil samples were collected at SWMU B-34 to satisfy these sampling recommendations. The samples were analyzed for barium, chromium, copper, nickel, zinc, cadmium, and lead. Three samples located in the pipe outfall area were also analyzed for VOCs and SVOCs. All of the metals except barium, nickel, and cadmium exceeded their RRS1 criteria. Chromium, copper, zinc, and lead exceeded their background standards four or more times, with lead exhibiting the highest reported values with respect to its background standard of 84.5 mg/kg. The March 2003 sampling effort did not define the lateral extent of contamination to the north and west of the site.
VOCs detected above RLs included only methylene chloride and toluene. However, these chemicals are not thought to be related to site contamination. Toluene was also detected in the associated blank, and, accordingly, all detected results were flagged with a “B.” Tape that was used for sample containment had been found to contain high concentration levels of toluene. Methylene chloride is a common laboratory contaminant, and it is not known to have ever been used at CSSA. Thirty-eight SVOCs were detected in all of the samples that were analyzed for SVOCs, but all of the results were M-flagged and below respective RLs. Based on these results, VOCs and SVOCs are not considered to be COCs for the site.
3.2 - Evaluation of Data Quality Objectives Attainment
Overall DQOs for the investigations at CSSA are provided in Section 11 of the Work Plan overview (Volume 1-1, RFI Addendum). A detailed list of DQOs for SWMU B-34, along with an evaluation of whether each DQO has been attained, is provided in Appendix B. As described in Section 1, the main objectives of the SWMU B-34 investigation are to determine if the site meets TCEQ requirements for RRS1 closure and to meet requirements of the consent order.
All data generated during the SWMU B-34 investigation were reviewed to confirm conformance with the AFCEE QAPP; the data verification reports are included in Appendix C. All data are considered usable for site characterization purposes. Although several results are flagged “M,” these results are considered usable because the matrix interference is minimal and does not significantly affect results.
Because metals in surface soil samples exceed background levels, TCEQ requirements for RRS1 closure have not been met. Furthermore, the consent order requirement to identify the horizontal extent of contamination has not been met.
Additional surface soil sampling is necessary to define the lateral extent of surface soil contamination. If RRS1 closure is sought, removal of known contaminated soil is necessary. Since metals contamination has likely affected the entire soil profile beneath SWMU B-34, excavation of soils to bedrock may be necessary. Soil boring logs from the August 2002 RFI show soil extends to a depth of approximately 4 to 5 feet bgs at SWMU B-34. Based on the March 2003 sampling results, the minimum area that will be excavated extends from McElroy Road northward until it encompasses B34-SS08. Although B34-SS14 has a reported lead concentration of 89.63 mg/kg, this value only slightly exceeds the RRS1 of 84.5 mg/kg; therefore, excavation on the south side of McElroy Road is not considered warranted. Additional surface soil samples should be collected to the west of the site, north of the site, and in the vicinity of B34-SS13. Based on results of the RFI sampling and the March 2003 sampling, these samples should be analyzed for chromium, copper, zinc, and lead. Barium, cadmium, nickel, and SVOCs can be deleted from the COPCs list for SWMU B-34 since they were not detected above background or RRS1 levels. VOCs are also not included because the only analytes detected above RLs, methylene chloride and toluene, are not considered to be site-related. One sample should be collected from below the pit in Building 28 and analyzed for VOCs, SVOCs, metals, and total petroleum hydrocarbon (TPH). In addition, TPH samples should be collected at previous sampling locations (B34-SS10, B34-SS11, and B34-SS12) to ensure that diesel contamination is not present. When the lateral extent of contamination has been defined, excavation activities may proceed. Confirmation samples should be collected at the site during the excavation activities to insure that all contaminated materials are removed. The analyses performed for confirmation samples will be based on the additional sampling results.