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SWMU B-12 RCRA Facility Investigation/Closure Report
Section 2 - Closure Activities
SWMU B‑12 is a 1‑acre site formerly used for disposal of large pieces of scrap metal and various weapons. The site contained visible metal debris, clay pipe fragments, ceramic and porcelain shards, and limestone boulders in the embankment on the southwest portion of the site. Based on the RFI sampling results, closure of SWMU B‑12 required excavation and disposal of the waste material present within and adjacent to the embankment.
Excavation of the waste and contaminated soil media was conducted during late 2003 and early 2004. During this period, approximately 2,700 CY of waste/contaminated soil media (i.e., remediation waste) was removed from the embankment area and stockpiled in the flat area on the site for waste characterization/management prior to disposal.
Three initial composite waste characterization samples were collected from the stockpiled soil, and submitted for Toxicity Characteristic Leaching Procedure (TCLP) for leachable metals analyses. TCLP analytical results indicated that leachable lead exceeded State of Texas Hazardous Waste Classification. The excavated soils were subsequently mixed in situ with 101 tons of agricultural grade phosphate as a metals stabilization technique. The phosphate was mixed by using heavy machinery to drag and mix the soil material with the phosphate. Three additional samples were collected after stabilization to determine if the treated waste met Class 2 criteria. Results of analyses for the treated remediation waste material indicated the soil met Class 2 criteria. Waste characterization sample results are included in Table B12‑2. Disposal of the remediation waste was accomplished under Waste Management, Inc. (WMI) waste profile CG‑25591 C‑15. Copies of the SWMU B-12 manifests are provided in Appendix B. The remediation waste was disposed of at WMI’s - Covel Gardens Landfill facility in San Antonio, Texas. The following photographs show excavation activities at the site.
Treatment of waste/contaminated soil media, referred to as remediation waste, within SWMU B‑12 was conducted in accordance with the USEPA’s Area of Contamination policy. The Area of Contamination concept is applicable for RCRA corrective actions and thus management of hazardous remediation waste, including treatment, is allowed without triggering RCRA Subtitle C requirements. Additionally, remediation wastes are not generated until they are removed from the area of contamination. Therefore, only non‑hazardous remediation wastes were generated from SWMU B‑12 and transported to Covel Gardens Landfill. Further discussion of the area of contamination concept and interpretation of the applicability for use at CSSA is provided in the revised RFI Waste Management Plan, dated February 2004.
Excavation at SWMU B-12, November 24, 2003.
Stockpile of excavated material at SWMU B-12.
The man-made embankment is in background.
November 24, 2003.
Debris removed during excavation at SWMU B-12, November 24, 2003.
Confirmation sampling was performed during excavation activities to verify that RRS1 criteria had been met and all waste residue had been removed from the site. As the waste and waste residue was excavated, samples were collected on the sidewalls and the bottom of the excavation pit to determine if RRS1 was achieved.
During February 2004, two bottom samples (B12‑BOT01 and B12‑BOT02) and six sidewall samples (B12‑SW01 through B12‑SW06) were collected in the excavation area. These samples were analyzed for barium, copper, nickel, and zinc (SW‑6010B), lead (SW‑7421), mercury (SW‑7471A), and fluoranthene (SW‑8270C). None of the samples had concentrations of fluoranthene that exceeded RRS1. However, several samples had metals concentrations that exceeded background RRS1 (Table B12‑3). Sampling locations are shown on Figure B12‑7.
Of the two bottom and six sidewall samples collected in February 2004, four samples (B12‑BOT01, B12‑SW04, B12‑SW05, and B12‑SW06) were reported with RRS1 exceedances for various metals. The areas with RRS1 exceedances were re‑scraped, or over‑excavated, to remove any possibly affected soils and the excavated soils were added to the existing stockpile for treatment with phosphate. An additional bottom sample, B12‑BOT03, and three sidewall samples (B12‑SW07, B12‑SW08, and B12‑SW09) were collected during May 2004. Sample B12‑BOT03 represents the over‑excavated area where sample B12‑BOT01 was collected. Sample B12‑SW07 represents the over‑excavated area where sample B12‑SW04 was collected. Sample B12‑SW08 represents the over‑excavated area where sample B12‑SW05 was collected. Sample B12‑SW09 represents the over‑excavated area where sample B12‑SW06 was collected. Samples collected from over‑excavated areas were analyzed for those metals that exceeded RRS1 in the previous samples taken from that area (Table B12‑3). See Figure B12‑7 for all sample locations. An analytical results summary is provided in Appendix A.
After the confirmation samples indicated that affected soils had been removed from the site, the 2,700 CY of stockpiled soils were removed and hauled to Covel Gardens Landfill for disposal.
Due to the absence of VOCs above RRS1 during the RFI sampling, the closure samples were not analyzed for VOCs. Two SVOCs were detected above RRS1 during the RFI sampling, DEHP (<0.03 to 13 mg/kg) and fluoranthene (<0.04 to 0.75 mg/kg).
The occurrence of DEHP above RRS1 is considered to be associated with laboratory or sampling equipment bias. In addition, there are no records of DEHP use or disposal at CSSA. DEHP is commonly used as a plasticizer and is present in laboratory equipment. Therefore, DEHP was excluded from the closure sampling routine. Fluoranthene was included in the confirmation sampling routine.