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SWMU B-13 RCRA Facility Investigation Report

Section 3 - Conclusions and Recommendations

SWMU B-13 was identified as a site that had been used historically for the disposal of construction debris (i.e., concrete rubble, wire binding, bricks). A portion of the waste disposal debris was covered with sand and the underlying debris has been exposed as a result of erosion from surface drainage. A geophysical survey conducted on March 12, 1996, revealed three anomalies that are potentially associated with past subsurface waste management activities. Two other anomalies were linked to construction debris piles on bedrock located within the site.

A soil boring investigation was initiated in 1996 to verify the absence or presence of VOCs, SVOCs and metals. The analyses of the subsurface samples that were collected in 1996 were performed by ITS Laboratories, Inc., and were deemed unusable by the EPA in 1999. A rework of the soil boring investigation was performed in March 2000 to replace the analytical data. DEHP, 1,2-dichlorobenzene, fluoranthene, chromium, copper, lead, mercury and zinc were detected at concentrations that exceed RRS1 closure criteria. All compounds except DEHP and 1,2-dichlorobenzene are found only in the surface soil samples. The compound 1,2-dichlorobenzene was detected at 9.5-10 feet bgs in RW-B13-SB04.

It is argued that the DEHP found in the surface and subsurface soil/rock samples may be eliminated from closure considerations as a COC. Bis(2-ethylhexyl)phthalate is a common laboratory sampling equipment contaminant. DEHP is not a transformation product of any COC at the site and there is no historical evidence to support the association of DEHP with SWMU B-13.

When a soil or rock sample is collected, the sample is handled using a trowel and rubber (nitrile) gloves. The sample typically must be pushed into the glass jar, and as such there is significant contact between the gloves and sample. This is especially true for rock samples which are difficult to put into small sample jars.

Since DEHP is a common contaminant specifically associated with gloves, and it is detected in low quantities (1.4 mg/kg) in the equipment blank, it is argued that the DEHP detected in rock samples at SWMU B-13 is associated with the use of gloves, and is not present as an environmental COC at the site.

Fluoranthene, which is commonly associated the combustion of organic matter and is present in fossil fuels, was detected in one sample, the field duplicate of RW-B31-SB01 (0.5-1 ft). Fluoranthene was reported in only one sample, and it was detected at the surface and not any lower in the soil profile. In addition, it was detected at a concentration (0.71 mg/kg) which is only slightly above the RL (0.7 mg/kg). For these reasons, it is suggested that fluoranthene may be disregarded as a COC for SWMU B-13 site closure considerations.

As described in Section 2.2.4, metals exceeded RRS1 criteria in surface soil only. These exceedances were detected at locations associated with subsurface anomalies (SB01, SB02, and SB04). Lead, copper, and zinc were the most common contaminants, but the zinc exceedances were very slight (1.2 mg/kg at SB02, and 4.4 mg/kg at SB04). Mercury and chromium also exceeded background at one sample each. The lateral extent of the metals contamination in surface soil has not been delineated.

Finally, the concentration of 1,2-dichlorobenzene exceeded the VOC RL at SB04, at a depth of 9.5 feet. This compound was not detected in any of the other samples collected at the site, including those overlying SB04 (9.5-10 feet). It was also not detected in the sample from the same location during the SVOC analysis. 

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-13, along with an evaluation of whether each DQO has been attained, is provided in Appendix D. As described in Section 1, the main objectives of the SWMU B-13 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-13 investigation were reviewed to confirm conformance with the AFCEE QAPP; and the data verification reports are included in Appendix C. All data are considered useable for site characterization purposes.

Based on soil boring findings, it is known that waste is buried at the site. Furthermore, waste piles remain on the ground surface. 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 lateral extent of contamination, have also not yet been met.

3.3 - Recommendations

Because buried and surficial waste is known to exist at the site, and because surface soil concentrations exceed background levels, the site does not meet RRS1 criteria for closure. To meet RRS1 closure criteria, excavation and proper disposal of the waste is recommended. Furthermore, additional surface soil sampling for chromium, copper, nickel, and zinc (SW-6010B), and lead (SW-7421) analytes is recommended to delineate the horizontal extent of contamination. For planning purposes, it is estimated that approximately 11,500 cubic yards of material at SWMU B-13 could contain waste and waste residue. This estimate is based on an area including SB01 and SB02 that measures 75 feet by 260 feet, and an area including the anomaly near SB03 and SB04 that measures approximately 75 feet by 150 feet. It is assumed that waste could be present to a depth of ten feet. Samples of the excavated material must be collected and analyzed using TCLP for characterization prior to off-post disposal. Landfills typically require one sample per 250 cubic yards of material which means approximately 46 samples for waste from SWMU B-13. 

Following excavation, additional sampling is recommended to determine if the site meets RRS1 closure requirements. It is not recommended that any further actions be taken for the DEHP, fluoranthene and 1,2-DCB, detected at low concentrations. DEHP is considered to be a laboratory contaminant. Fluoranthene contamination will be excavated as part of site metals cleanup. Because the concentration of 1,2-DCB was so low and limited to only one sample, additional work to address this single, slight exceedance is not considered warranted. 

Separation of waste debris from excavated soils may be warranted. Metal scrap can be recycled. If excavated soils are contaminated with metals, they can be treated along with metals-contaminated soils from other SWMUs (B-20/21, B-24, B-28, DD, and B-8).

After excavation is complete, verification samples should be collected to confirm that all waste residue has been removed. Verification samples should be analyzed for chromium, copper, nickel, and zinc (SW-6010B); lead (SW-7421); and VOCs (SW-8260B), based on results of the RFI sampling. The total number of verification samples required at the site is not anticipated to exceed 25; however, this estimate is dependent on the extent of contamination and the success of removing all waste and waste residue during initial excavation.