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[RFI Report]

Final SWMU B-12 RCRA Facility Investigation Report

Section 3 - Conclusions and Recommendations

3.1 - Conclusions

SWMU B-12 was used in the past for disposal of large pieces of scrap metal and other waste material.  Based on visual observations at the site and results of the 1995 geophysical survey, waste materials were disposed along an embankment at the site.  No EM anomalies were observed in the adjacent flat-lying portion of the site in a 1995 geophysical survey.  As discussed in Section 1.3, the geophysical survey did not include the area of the embankment due to surface interference from the visible metal debris.  A soil boring investigation was conducted in 1996 to verify the absence or presence of VOCs, SVOCs, explosives, and metals.  The soil boring investigation focused on the western boundary of SWMU B-12 because visual evidence of waste disposal was noted during the initial field investigation.  The analytical data submitted by ITS Laboratory from that investigation was deemed unusable by the EPA.  Therefore, a soil boring investigation performed in March 2000 replaced the 1996 analytical data.  As discussed in Section 1.3, the geophysical survey did not include the area of the embankment due to surface interference from the visible metal debris.

Analytical data gathered from March 2000 reported concentrations above the applicable RRS1 criteria for various metals, bis(2-ethylhexyl)phthalate, and fluoranthene.  Fluoranthene is present at RW-B12-SB04 (0 to 0.5) at a concentration of 0.75 mg/kg, which only slightly exceeds the RL for this sample of 0.70 mg/kg.

Bis(2-ethylhexyl)phthalate was detected above the RRS1 in subsurface samples from all four borings performed.  However, in the absence of any other exceeding VOCs or SVOCs, bis(2-ethylhexyl)phthalate concentrations detected in exceedance of the RL are considered to be associated with laboratory or sampling equipment bias.  The equipment blanks collected on March 15, 2000, which may be used for comparison to the SWMU B-12 samples with detected bis(2-ethylhexyl)phthalate, reported concentrations below the RL.  No other VOCs or SVOCs were reported above laboratory RLs.

Metals concentrations above background levels were detected in all borings.  Most of these concentrations did not significantly exceed background levels, except at RW-B12-SB04 (0 to 0.5 feet bgs) where lead was detected at 773.2 mg/kg, mercury was detected at 0.65 mg/kg, and zinc was detected at 182.5 mg/kg.

3.2 - Evaluation of Data Quality Objectives Attainment

Overall data quality objectives (DQOs) for the investigations at CSSA are provided in Volume 1-1 behind the RFI Addendum tab (Section 11 of the Work Plan Overview).  A detailed list of DQOs for SWMU B-12, along with an evaluation of whether each DQO has been attained, is provided in Appendix C.  As described in Section 1, the main objectives of the SWMU B-12 investigation are to determine if the site meets TNRCC requirements for RRS1 closure and to meet requirements of the 3008(h) Administrative Consent Order.

All data generated during the SWMU B-12 investigation were reviewed to confirm conformance with the AFCEE QAPP; the data verification report is included in Appendix D.  All data are considered useable for site characterization purposes.  Although several results are flagged with an M, these results are considered usable because the matrix interference is minimal and does not significantly affect the sample results.  Several results are flagged with a J however, these results are considered usable because the estimation of quantitation does not significantly affect the sample results. All of the initial calibration, second source verification and internal standard criteria were within quality control limits, as described in the data verification reports (Appendix D).

Waste material is visible in the embankment in the southwestern portion of the site; therefore, the site does not meet the TNRCC RRS1 requirement for removal of all waste. Several of the 3008(h) RFI requirements, such as identification of waste characteristics and determination of extent of contamination, have also not yet been met.

3.3 - Recommendations

Closure of SWMU B-12 under RRS1 requires removal of waste visible in the embankment at the site and delineation and subsequent remediation or removal of contaminated soil at the site.  Excavated material should be characterized prior to disposal.  The estimated volume of waste material and waste residue present at SWMU B-12 is approximately 1,300 cubic yards.  This estimate is based on an assumed length of 200 feet.  In addition, it is assumed that waste material is present throughout the height of the 20-foot embankment, and it extends back 8 feet from the embankment wall.  Based on waste at most other SWMUs at CSSA, it is likely that this waste is non-hazardous.  Confirmation samples should be collected following removal/remediation to verify that no contamination remains.  Analysis should include barium and copper (SW-6010B), lead (SW-7421), and mercury (SW-7471A), based on results of the RW-B12-SB03 (1.0 to 1.5 ft bgs) and RW-B12-SB04 (0 to 0.5 ft bgs) sample results.  Evaluation of the current boundary of SWMU B-12 should also be made at this time, and if any adjustments are necessary, the boundary of the site should be re-surveyed with a GPS unit.  The current boundary of the site appears to include too much area to the east, and possibly not enough area to the west.  Following excavation of waste and waste residue, any resulting trenches should be backfilled with clean fill and the site restored.

Following removal of all waste debris and waste residue described above, pursuit of closure under RRS1 is recommended.  The only metals exceeding background in subsurface Glen Rose samples were barium, nickel, zinc, and lead.  Detections of zinc and nickel in RW-B12-SB01 are only slightly above the background levels.  Confirmation sampling for barium and lead near RW-B12-SB03 will verify the presence of these COCs following excavation.