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Demolition and excavation of the building slab at AOC-53 was conducted during October 2004. A Trac-Hoe equipped with a pneumatic hammer was used to break up the pad; the concrete debris was then excavated and stockpiled at the site prior to disposal.
Demolition of the foundation revealed that it was approximately 3 feet thick at its thickest point, along the foundation perimeter, and had four stabilization pillars (3 feet by 4 feet) running approximately 8 feet into the ground. Demolition of the foundation and pillars produced 440 cubic yards (CY) of concrete debris to be disposed.
In addition to the concrete debris, approximately 32 CY of Class 2 non-hazardous soil waste was generated at AOC‑53 during soil excavation activities. Disposal of the concrete debris was conducted under waste profile CG‑29058 C‑1. Disposal of AOC‑53 soils was conducted under waste profile CG‑25591 C‑21. All concrete debris and soil waste was disposed at Covel Gardens Landfill in San Antonio, Texas. Waste manifests are provided in Appendix A.
2.2 - Closure and Confirmation Sampling
After the foundation and pillars were demolished and stockpiled, an odor was noticed coming from the soil beneath the foundation. The odor was described as a pesticide/herbicide odor. Although there is no history of any type of pesticide usage or storage at the site, five samples, including one bottom sample (AOC53‑BOT01) and four sidewall samples (AOC53‑SW01 through AOC53‑SW04), were collected for screening purposes to identify which full analyses should be performed at the site. The screening samples, collected on October 14, 2004, were analyzed for VOCs and SVOCs. Tentatively identified compounds (TICs) were also requested for both VOC and SVOC analyses. Sample locations are shown on Figure AOC53‑5.
No VOCs or SVOCs were detected in the screening samples, but several TICs were reported. The TIC data is included in Appendix E. Although no VOCs or SVOCs were detected, five additional full quality control (QC) samples were collected on December 20, 2004 and analyzed for VOCs, SVOCs, and pesticides/herbicides. One bottom (AOC53‑BOT02) and four sidewall samples (AOC53‑SW05 through AOC53‑SW08) were collected.
One pesticide, p,p-dichlorodiphenyldichloroethylene (4,4’‑DDE), was detected in AOC53-SW07, but the result was well below the RL of 0.025 milligram per kilogram (mg/kg) for 4,4’‑DDE (Table AOC53-1). No other pesticides/herbicides were detected in the samples. RLs represent RRS1 for all analytes except metals.
Two VOCs, methylene chloride and toluene, were detected in the samples. Methylene chloride was detected in every sample, but only exceeded the RL in AOC53‑SW07. This result for methylene chloride (0.0121 mg/kg) was only slightly above the RL (0.005 mg/kg). Toluene was detected in one sample, AOC53‑SW07, but the detected concentration was below the toluene RL of 0.005 mg/kg. No other VOCs were detected in the samples. The methylene chloride detections are attributed to laboratory contamination since the site contains no source and every sample had very low reported concentrations.
Two SVOCs, 4-methylphenol and pyrene, were detected in the samples. 4‑Methylphenol was detected in two samples (AOC53‑SW06 and AOC53‑SW07), but both reported concentrations were below the RL. Pyrene was detected in one sample (AOC53‑SW05), also below the RL.
On February 2, 2004, realizing that metals were not included in the original sample analyses, metals samples were collected at each of the locations that were originally sampled for VOCs, SVOCs, and pesticides/herbicides. Although the sampling locations were the same as the previous samples, the metals samples were labeled sequentially following the original sample IDs: AOC53‑BOT03, AOC53‑SW09, AOC53‑SW10, AOC53‑SW11, and AOC53‑SW12. AOC53‑BOT03 was collected at the same location as AOC53‑BOT02, AOC53‑SW09 was collected at the same location as AOC53‑SW05, AOC53‑SW10 was collected at the same location as AOC53‑SW06, AOC53‑SW11 was collected at the same location as AOC53‑SW07, and AOC53‑SW12 was collected at the same location as AOC53‑SW08. The matching sample data was merged in Table AOC53‑1. Each sample was analyzed for barium, chromium, copper, nickel, zinc, arsenic, cadmium, lead, and mercury.
AOC53‑SW09 slightly exceeded RRS1 for lead (84.5 mg/kg) with a result of 88.47 mg/kg and AOC53‑SW11 exceeded RRS1 for zinc (73.2 mg/kg) and lead with results of 93.96 mg/kg and 125.22 mg/kg, respectively. Additional excavation and sampling was conducted at these locations on February 16, 2005. After over-excavation was complete (approximately 100 CY was excavated), AOC53‑SW13 was collected at the over-excavated location of AOC53‑SW09 and AOC53‑SW14 was collected at the over-excavated location of AOC53‑SW11. Both samples were analyzed for those analytes that originally exceeded RRS1. All results were below RRS1.
During the over-excavation on February 16, 2005, it was determined that the sampling did not cover the entire extent of the building foundation; therefore, additional samples (AOC53‑SW15, AOC53‑SW16, and AOC53‑SW17) were collected in the eastern portion of the foundation area. Each sample was analyzed for metals, VOCs, SVOCs, and pesticides/herbicides.
Only AOC53‑SW16 had RRS1 exceedances (lead, zinc, and barium). Over-excavation and sampling was conducted at this sample location on March 3, 2005. Sample AOC53‑SW18 was collected in the over-excavated area of AOC53‑SW16 and analyzed for barium, zinc, and lead. All results were below RRS1.
Table AOC53‑1 shows only the detected analytes from the full QC samples. A complete list of all analytical results, regardless of whether or not an analyte was detected, is included in Appendix B.